1. science
2. geology

ICDP Proposal Cover Sheet
Workshop Preliminary X Full
Above For Official Use Only
X New Revised Addendum
Please tick or fill out information in all gray boxes
Title: Potrok Aike Maar Lake Sediment Archive Drilling Project
(PASADO)
Proponent(s): Bernd Zolitschka, Flavio Anselmetti, Daniel Ariztegui, Ray Bradley, Laurie Brown,
Hugo Corbella, Helga De Wall, Pierre Francus, Andreas Luecke, Nora Maidana,
Christian Ohlendorf, Frank Schaebitz, Stefan Wastegard
Keywords:
(5 or less)
Southern Hemispheric westerlies, quantitative climate
reconstruction, atmospheric dust, volcanic activity, maar
formation, climate modelling
Location: Santa Cruz,
Argentina
Contact Information:
Contact Person:
Department:
Organization:
Address:
Tel.:
E-mail:
Bernd Zolitschka
GEOPOLAR, Institute of Geography
University of Bremen
Celsiusstr. FVG-M, D-28359 Bremen, Germany
+49-421-218-2158
Fax: +49-421-218-9658
[email protected]
Permission to post abstract on ICDP Web site: X
Yes
No
Abstract: (400 words or less)
We propose to recover long sediment cores from Laguna Potrok Aike, a 770 ka old maar lake in the
dry steppe of southern Patagonia (Province of Santa Cruz, Argentina). Seismic surveys demonstrate
that ~400 m of pelagic sediments were deposited in the lake centre underlain by a yet unknown
thickness of volcaniclastic breccias. Based on this seismic data, three primary and three alternative
drilling sites were selected: (1) from the deepest part to obtain a continuous and high-resolution record
of climatic and environmental changes and to unveil the phreatomagmatic history including more
precise age constrains for the maar-diatreme formation from the volcaniclastic sediments below, (2)
from a subaquatic lake level terrace at 35 m water depth to constrain the range of lake level variations
and (3) from an angle hole passing through lacustrine sediments and the crater wall into the molassetype basement rocks to study the impact of explosive volcanism, post-eruptive structural evolution and
early processes of sedimentation in a relatively young maar-diatreme structure.
Within the framework of an international and interdisciplinary scientific approach the recovered
sediments will be used to test hypotheses related to this two broad themes:
•
•
High-resolution quantitative climate and environmental reconstructions from orbital and
suborbital (multimillennial) down to decadal timescales supported by multiple dating (e.g. 14C,
OSL, Ar/Ar) and stratigraphic correlation (e.g. pollen, tephra, paleomagnetics) with emphasis
on marine – ice core – terrestrial linkages and incorporation of results from GCM climate
simulations;
Detailed analyses of volcanic rocks and sediments provide insights into processes related to
phreatomagmatic explosions and early sedimention in a mid-Pleistocene maar lake. Never
before the entire lacustrine sediment record has been recoverd and underlying volcaniclastic
sediments have been drilled and investigated in a young maar-diatreme structure.
An international team of scientists has been attracted to cooperate in the framework of PASADO to
develop a comprehensive environmental, climatic and volcanological data set. Proposed science
management and drilling operation plans have the objective to achieve all necessary technical and
scientific needs to make PASADO internationally successful.
PASADO – Full ICDP Drilling Proposal
B
Scientific Objectives: (250 words or less)
Scientific deep drilling:
The main goal of PASADO is to recover long, undisturbed and continuous lacustrine and volcaniclastic
sediments from Laguna Potrok Aike as the basis for the following scientific objectives.
Quantitative climate and environmental reconstructions:
On orbital to decadal timescales a variety of multidisciplinary analytical methods will be applied to
reach these scientific goals:
• Multiple dating to provide a sound timeframe for all analyses using 14C, OSL, Ar/Ar,
tephrochronology, paleomagnetics
• High-resolution quantitative reconstruction of temperature, precipitation and hydrological
variations based on chironomids, pollen, stable isotopes, inorganic carbon and biomarkers;
• Quantitative reconstruction of terrestrial vegetation and fire history applying pollen and
charcoal;
• Development of high-resolution dust storm and volcanic tephra records based on
mineralogical and geochemical fingerprints;
• Reconstruction of a paleosecular variation record of the Earth’s magnetic field;
• Establishing marine – ice core – terrestrial linkages focusing on magnitude and abruptness of
glacial/interglacial transitions and periodicities during glacials and interglacials;
• Evaluation of proxy-based hypotheses with GCM climate simulations to establish mechanistic
links between climate variability and forcing factors. Questions relate to (1) latitudinal shifts in
the position of Southern Hemispheric westerlies, (2) recurrence patterns of synoptic-scale
phenomena like polar outbreaks, (3) the role of ice sheets, oceanic and atmospheric
circulation on climate change.
Understanding the phreatomagmatic history:
Analysis of volcanic rocks and accidental clasts will provide a unique dataset to better understand the
geometry and structure of maar-diatrems in soft-rock environments. This includes:
• Processes related to phreatomagmatic maar explosions;
• Investigation of early sedimention in a maar lake;
• Post-sedimentation and compaction history in Quaternary maar sediments.
Summary of Support Requested from ICDP
Estimated Total Project
Budget (ICDP funds plus other
Requested
ICDP funds: 1.382.000 US $
(in US$)
sources):
Planned Mobilisation in either
Start: Jan. 2008 or
Jan. 2009
(On-site operations only):
Requested
Operational
Support:
Estimated Duration in Month
2.004.195 US $
3 months
Drill Engineering
(Please contact ICDPs
Operational Support
Group if required)
Downhole
Logging (Please
contact ICDPs OSG if
required)
Field Lab
Equipment
(Please contact ICDPs
OSG if required)
Training Course
(Please contact ICDPs
OSG if required)
25,120 US$
4,820 US$
Details such as a Budget Plan, Management Plan, and Drilling Plan to be provided as attachment to the
Proposal. OSG contact: U. Harms ([email protected]), Phone: +49 331 288 1085
Potrok Aike Maar Lake Sediment Archive Drilling Project
(PASADO)
a proposal submitted to the
International Continental Scientific Drilling Program (ICDP)
Attn: Dr. Uli Harms
GeoForschungsZentrum Potsdam
D-14473 Potsdam, Germany
Principal Investigators:
Bernd Zolitschka, University of Bremen, Germany, [email protected]
Flavio S. Anselmetti, ETH-Zurich, Switzerland, [email protected]
Daniel Ariztegui, University of Geneva, Switzerland, [email protected]
Raymond S. Bradley, University of Massachusetts, USA, [email protected]
Laurie Brown, University of Massachusetts, USA, [email protected]
Hugo Corbella, Universidad Nacional de la Patagonia Austral, Río Gallegos and Museo
Argentino de Ciencias Naturales, Buenos Aires, Argentina, [email protected]
Helga De Wall, University of Wuerzburg, Germany, [email protected]
Pierre Francus, Institut National de la Recherche Scientifique Quebec, Canada,
[email protected]
Andreas Luecke, Research Centre Juelich, Germany, [email protected]
Nora I. Maidana, University of Buenos Aires, Argentina, [email protected]
Christian Ohlendorf, University of Bremen, Germany, [email protected]
Frank Schaebitz, University of Cologne, Germany, [email protected]
Stefan Wastegard, University of Stockholm, Sweden, [email protected]
PASADO – ICDP Full Drilling Proposal
Table of contents
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Introduction ................................................................................................................ 1
Geology of the study area .......................................................................................... 2
Relevant previous work.............................................................................................. 4
3.1
Meteorological data ..................................................................................... 4
3.2
Limnology .................................................................................................... 5
3.3
Process studies ........................................................................................... 5
3.4
Seismic investigations ................................................................................. 7
3.5
Sediments.................................................................................................. 10
3.6
Paleoclimatic and environmental reconstruction ....................................... 11
3.7
Climate modelling ...................................................................................... 14
Importance of the study area ................................................................................... 15
Scientific motivation and goals of the drilling project................................................ 16
Proposed work ......................................................................................................... 18
6.1
Site selection and drilling strategy ............................................................. 18
6.2
Site survey information .............................................................................. 19
6.3
Geophysical downhole logging and log interpretation ............................... 20
6.4
Initial field-based investigations ................................................................. 21
6.5
Core storage, archiving and further lab-based processing ........................ 22
Expected scientific and societal benefits of the proposed work ............................... 24
Project management ................................................................................................ 24
International science team ....................................................................................... 26
Time table ................................................................................................................ 28
References............................................................................................................... 28
Appendices
A1. Seismic stratigraphy and interpretation .................................................................... 32
A1.1
Aims........................................................................................................... 32
A1.2
Seismic methods ....................................................................................... 32
A1.3
Results....................................................................................................... 34
A1.3.1 Morphobathymetry..................................................................................... 34
A1.3.2 Seismic facies and seismic stratigraphy .................................................... 34
A1.3.3 Seismic stratigraphic interpretation of Unit I and implications for
environmental history................................................................................. 41
A1.3.4 Maar geometry and anticipated deeper strata ........................................... 45
A1.3.5 References ................................................................................................ 45
A2. Seismic sections of proposed drill sites ................................................................... 47
A2.1
Maps .......................................................................................................... 47
A2.2
Seismic sections ........................................................................................ 48
A3. Permitting and environmental issues........................................................................ 54
A4. Education and outreach............................................................................................ 54
A5. Detailed budget ........................................................................................................ 55
A6. CVs of principal investigators ................................................................................... 61
A7. Relationship to other international geoscientific programmes .................................. 74
A8. Letters of support...................................................................................................... 75
IV
PASADO – Full ICDP Drilling Proposal
1
1. Introduction
We have recently identified the 100 m deep and 770 ka old maar lake Laguna Potrok Aike
(52°S, 70°W; 113 m a.s.l.) in southern Patagonia (Argentina) as a potential ICDP drilling
target and request funds for drilling operations in Argentina (Figs. 1, 2). The location of
Laguna Potrok Aike is of global geological significance and potentially the only site that can
provide a continuous and high-resolution terrestrial sediment record over several glacial
cycles for South American mid-latitudes. The area is extremely sensitive to climatic changes
and an ideal continental counterpart of marine records from the Atlantic and Pacific Oceans
for a comprehensive understanding of the past climate system. Thus PASADO tackles a
problem of global significance at a location of paramount importance, i.e. a „world-class“
geologic site. After the international ICDP workshop “PASADO” was carried out in March
2006 in Río Gallegos (Argentina), a broad international collaboration started and the best
possible science team grew together with the aim to pool financial and technological
resources to carry out the deep drilling with the GLAD800 coring system at Laguna Potrok
Aike in close cooperation with DOSECC.
Fig. 1: Map of South America and satellite image of
southern Patagonia with the maar lake Laguna
Potrok Aike, some other lakes and the City of Río
Gallegos indicated.
The “Potrok Aike Maar Lake Sediment Archive Drilling Project” (PASADO) plans to
continue the incentive of ICDP in a sense that in addition to tropical lake coring activities also
non-tropical sites are considered. However, all outer tropical sites are from the northern
hemisphere. To improve our understanding of global climate dynamics PASADO will be the
first location from the non-tropical southern hemisphere to be drilled within the framework of
the ICDP.
A sound basis for PASADO was formed by seismic surveys and multidisciplinary
reconstructions based on 1 m gravity and 19 m piston cores. Data from four seismic surveys
indicate a funnel shape structure consistent with the interpretation of a maar-diatreme
setting. The thickness of lake sediments exceeds 400 m. These data clearly make Laguna
Potrok Aike a well-suited site for terrestrial climate reconstructions of the Southern
Hemisphere. So far, just a few shallow drillings into maar-diatreme structures have been
performed. All of them, except for kimberlite diatremes, are in Tertiary volcanic fields in
basement-type wall rocks (e.g. Schulz et al., 2005) and so far there is a lack of information
about the geometry of maar-diatremes in sedimentary and soft-rock settings. The
geophysical survey in combination with the drillings at Laguna Potrok Aike will give important
insights into the internal structure of maar-diatremes with relevance for their potential as
sediment-traps. Bouguer anomalies of Quaternary maar structures are distinctly different
from those of Tertiary maars (Büchel et al., 1987) and highlight the more mature stage of
compaction in older maar sediments.
PASADO addresses several challenging issues of geoscientific and socioeconomic
relevance related to Earth history, global environment and climate change, to volcanic
PASADO – Full ICDP Drilling Proposal
2
systems and to sedimentary basins as included in ICDP’s scientific themes. Research topics
comprise quantitative climatic and environmental reconstruction, paleosecular variation of the
Earth's magnetic field, natural hazards (fire history, history of volcanic activity including
tephra fallout, dust deposition) and volcanic systems (evolution of phreatomagmatic craters,
history of volcanic activity) for the last glacial to interglacial cycles. Moreover, from the
beginning this project will include climate modelling components. Obtained reconstructions of
climate variability will be compared statistically with the output of Global Circulation Model
(GCM) simulations to improve our understanding of forcing mechanisms of the global climate
system.
Fig. 2: Bathymetric map of Laguna Potrok Aike. Please note the Holocene lake level low stand
(submerged terrace level at ca -35 m in dark green), young fluvial and lacustrine deposits (grey), the
1,19 Ma old basalt flow (red), the tephra deposits (pink), the moraine till (yellow), outcrops of Santa
Cruz Formation (orange), the multi-channel seismic lines and the planned ICDP drill sites.
2. Geology of the study area
The study area is located in the Pliocene to late Quaternary Pali Aike Volcanic Field (Fig. 3)
a northwest-southeast oriented tectono-volcanic belt about 50 km wide and more than 150
km long. This back arc volcanic area (Mazzarini & D'Orazio, 2003) is situated in the Magellan
Basin 80 km west of the city of Río Gallegos, 70 km north of the Strait of Magellan and about
100 km east of the Andean volcanic arc. Petrologically, the Pali Aike Volcanic Field consists
of alkali-olivine basalts with an age range from 3.8 Ma (Pliocene) in the western part towards
0.01 Ma (Holocene) closer to the Atlantic Ocean (Fig. 3). Along fissure related eruptions,
cinder cones, lava domes and about 100 maars (Ø 500 to 4000 m) have been formed.
PASADO – Full ICDP Drilling Proposal
3
Fig. 3: Map of the Pali Aike Volcanic Field with ages of Pliocene to late Quaternary back arc volcanism
and position of mid-Pleistocene terminal moraines (Corbella, 2002; Zolitschka et al., 2006a).
The oldest outcropping geological strata in the immediate study area are Lower
Miocene fine-grained molasse-type fluvial sediments of the Santa Cruz Formation (Fig. 2).
During the Plio-Pleistocene, the investigated area south of the river Río Gallegos was
covered by glaciers that originated from the Magellan Strait, Seno Skyring and Seno Otway
(Fig. 3). Fluvioglacial deposits (Patagonian Gravel Formation) and moraine tills today form
the surface of the southern Patagonian Plains. Glaciations occurred between 3.5 and 1.0 Ma.
However, evidences and dating are poor (Rabassa & Clapperton, 1990; Zolitschka et al.,
2006b).
Laguna Potrok Aike is a 100 m deep maar lake with a diameter of 3.5 km (Fig. 2). The
entire depression has a diameter of about 5 km. At the southwestern crater rim a cinder cone
with a well-developed basaltic lava flow which was Ar/Ar-dated to 1.19 ± 0.02 Ma is visible
(Fig. 2; Zolitschka et al., 2006b). Both are covered with moraine till (Fig. 2). The lava flow
never entered the lake and was not related to the formation of the maar. Glacial sediments
and related terminal moraines ca 10 km south of Laguna Potrok Aike must be older than the
maar (Fig. 3).
The tephra deposits at the lee-side of Laguna Potrok Aike (Fig. 2) are composed of
volcanic fragments (juvenile and non-juvenile glass, lapilli and clasts) and accidental lithics.
The common bed forms associated with base surge deposition are all indicating a typical
phreatomagmatic explosive event in generating the Potrok Aike maar and its pyroclastic
succession. Silt fragments and quartz grains derived from disrupted crystalline gravels as
well as siliciclastic grains from alluvial deposits are found as accidental clasts. This suggests
that the phreatomagmatic eruption not only occurred in the inter-basalt layer ground water
table (e.g. pure water recharge), but either surface aquifers (e.g. fluvial or glaciofluvial
systems with sand deposition) or interbedded water-saturated sand/silt/fine gravel layers
provided water for the phreatomagmatic explosion.
Ar/Ar-dating of glass fragments (0.77 ± 0.24 Ma, Zolitschka et al., 2006b) reflects the
heterogeneity of volcanic fragments in pyroclastic deposits. For more precise age
determinations of the diatreme formation a distinction of non-juvenile volcanic fragments from
disrupted co-magmatic dyke and sill or older lava flow fragments will be crucial.
PASADO – Full ICDP Drilling Proposal
4
Generally, a maar-diatreme structure is formed by a shallow explosive eruption caused
by the contact of rising magma with groundwater. Shock waves cause a fragmentation of the
wall rocks and due to ejection of the magmatic (juvenile) clasts mixed with wallrock clasts a
cone-shaped diatreme with a crater rim is formed.
The size of the depression (Ø 5 km) or the lake (Ø 3.5 km) as observed at Potrok Aike
today are very likely the result of wave erosion at the lake shore which is developed in soft
sedimentary rocks. This explanation has been used for the four large Espenberg Maars in
Alaska (Ø 4-7 km) which are developed in Pleistocene sediments (Beget et al., 1996).
Reflection seismic revealed that this assumption seems to be correct also for Laguna Potrok
Aike (Fig. A13; Gebhardt, 2006, pers. comm.). Here a diameter of only 2400 m has been
determined for the initial maar-diatreme structure which seems to have the shape of a
champaign glass. However, this diameter still is larger than the diameters of other maardiatremes which are in the range of 10 to 1500 m and have diameter to depth ratios between
1:1 and 1:2.5 (Lorenz, 2003). The larger diameter can be a result of repeated
phreatomagmatic explosions with downward migrating locus of thermohydraulic explosion, a
consequence of the soft substrate environment or a combination of both.
3. Relevant previous work
This proposal is based on two interdisciplinary projects in the framework of the German
Climate Research Programme (DEKLIM) called “South American Lake Sediment Archives
and Modelling” (SALSA) and “Transient simulation of the middle Holocene with a coupled
atmosphere-ocean general circulation model” (MIDHOL). Moreover, four seismic surveys
have been carried out within the DFG-funded project “Pre-site survey for potential new ICDP
sites in southern Patagonia, Argentina” (POTROK) which is related to the DFG Priority
Programme “ICDP”. This research had and still has a strong educational component with five
Ph.D. theses (one finalised and four ongoing), two diploma and one state examination thesis.
3.1 Meteorological data
The eastern part of southern Patagonia is a semiarid cool semidesert with steppe vegetation
lacking any well-defined rainy season. A strong precipitation gradient exists between the
west and the east coast of South America caused by the topography of the continent. The
Southern Hemispheric westerlies (SHW) transport humid air from the Pacific Ocean to the
Andes leading to annual precipitation sums of 4000-6000 mm along the west coast
(Weischet, 1996). In the rain shadow east of the Cordillera, precipitation decreases to <400
mm and in the Pali Aike Volcanic Field even to <300 mm (Gonzalez & Rial, 2004). At the
Potrok Aike meteorological station occasionally values of only 150 mm have been observed
(Zolitschka et al., 2006b).
The SHW across Patagonia are characterized by high wind speeds with mean annual
values of 7.4 ms-1 at Río Gallegos and maxima during summer. Wind direction is primarily
from the west shifting occasionally to NW and SW (Weischet, 1996; Baruth et al., 1998). The
instrumental meteorological record of the Río Gallegos weather station exists since 1931 but
is rather fragmentary. It shows an annual mean precipitation sum of 250 mm and a mean
annual temperature of 7.4°C with a July (winter) minimum of +1.0°C and a January (summer)
maximum of 13.0°C. Both mean annual temperature and annual precipitation sum for the
Potrok Aike meteorological station (990 m distance to the lake and run by INTA since
January 1999) are 30-40% lower compared to the Río Gallegos weather station near the
coast (Zolitschka et al., 2006b). While the differences in temperature can be explained by the
increasing degree of continentality towards the west, the discrepancy in precipitation points
towards an eastern source region for rainfall events that may be related to polar outbreaks.
This assumption has been confirmed by statistical analysis of Potrok Aike meteorological
data demonstrating that most precipitation is brought in by air masses from the east (Mayr et
al., 2007b). Precipitation is thus an indicator for the strength of SHW and links hydrological
data to the regional synoptic situation and to expected latitudinal shifts of SHW.
PASADO – Full ICDP Drilling Proposal
5
3.2. Limnology
Laguna Potrok Aike is a 100 m deep maar lake with a surface area of 7.58 km² and one
episodic inflow at its western and several episodic gullies at the eastern shore (Fig. 2). The
lake is mostly fed by groundwater and currently has no surface outflow. As a closed lake
system it reacts very sensitively to hydrological variations. This is evidenced by a multitude of
surficial and submerged lake level terraces (Haberzettl et al., 2005). Morphometric data
reveal an almost circular shape of the lake while the topography suggests a significant
influence of the catchment area (estimated to ca 200 km²) on the lake system. Therefore, a
thick sedimentary infill must be expected. Despite the large catchment area the maximum
water depth still is 100 m which points to an enormous initial crater depth. Bathymetry (Fig.
2) reveals an almost flat and pot-shaped morphology of the lake floor typical for maar lakes.
However, water profile data show that there is almost no stratification of the water column
under present-day conditions (Fig. 4). This is due to strong winds that enforce polymictic
conditions and hardly allow the formation of a thermally stratified water body during southern
summers.
Fig. 4: High resolution water temperature data (thermo isopleths) recorded with 6 hr resolution by 7
thermistors attached to a mooring at the deepest part of Laguna Potrok Aike (Zolitschka et al., 2006b).
With regard to the ionic composition, the water of Laguna Potrok Aike is dominated by
chloride and sodium followed by magnesium, potassium, calcium and sulphate at a pH
between 8.7 and 9. This is supported by high electric conductivities between 2970 and 3110
µS cm-1 for the years 2002 to 2005. Laguna Potrok Aike is a subsaline lake with salinities
ranging from 2.22 to 2.53 ppt. Nitrate concentrations were mostly below detection limit.
Remarkably high are the total phosphorus (TP) concentrations in the surface water: 13003600 µg L-1 (Zolitschka et al., 2006b). Despite these high TP concentrations planktonic
productivity is low which is also indicated by a secchi depth of 6.9 m. Elevated TP values are
difficult to explain but might be related to groundwater inflow and regional geology.
3.3. Process studies
Since the start of the SALSA project in the year 2002 we have established an extensive
monitoring programme in and around Laguna Potrok Aike. This includes the meteorological
station run by INTA in proximity to the lake. Moreover, thermistors are installed at various
water depths attached to a mooring string in the lake to monitor seasonal temperature
changes and mixing processes of the water body (Fig. 4). Attached to this mooring are also
PASADO – Full ICDP Drilling Proposal
6
sediment traps and a pressure sensor. The latter records lake level fluctuations continuously.
This monitoring effort is important for an understanding of sediment forming processes
because the terminal lake Laguna Potrok Aike is very sensitive to changes in the
hydrological regime. Several terraces up to 25 m above and at least 35 m below present day
lake level witness drastic lake level variations during the past. Studies of recent processes
indicate that changes of the lake water volume lead to changes in the carbonate system
(Haberzettl et al., 2005) and the oxygen isotopic composition of the lake water (Mayr et al., in
prep.), which opens the possibility to trace such changes in the sedimentary record.
Meteorological together with stable isotope data, bathymetric information of the lake
and calculations of the local radiation balance were used to perform hydrological balance
calculations by combining an energy-budget with a bulk-transfer method (Brutseart, 1982;
Penman, 1948). The obtained lake volume changes were translated into changes of the lake
level between Jan. 2001 and Dec. 2004 (Ohlendorf et al., in prep.). For the time period Mar.
2003 until Dec. 2004 calculated lake level changes were compared to pressure sensor data
(Fig. 5). The fact that calculated lake levels closely follow the measured ones indicates that
lake level mainly is driven by the precipitation/evaporation ratio.
1.8
1.6
Lake level (m)
1.4
LL measured, pressure sensor (m)
LL calculated, ref. 14.03.03 (m)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Mar-03
May-03
Jul-03
Aug-03
Oct-03
Dec-03
Mar-04
May-04
Jul-04
Aug-04
Oct-04
Dec-04
Date
Fig. 5: Lake level (LL) of Laguna Potrok Aike between March 2003 and Dec. 2004 as measured by a
pressure sensor installed on a mooring string in 27.5 m water depth in comparison to a lake level
curve that was calculated using an energy-budget/bulk-transfer approach (Ohlendorf et al., in prep.).
The reference lake level is of March 14, 2003.
An analysis of the meteorological factors that contribute to the hydrological balance
calculation reveals that together with precipitation, wind strength and wind direction exert an
important influence on the hydrological balance of Laguna Potrok Aike. In particular, it is
inferred that lake levels decrease during periods of persistently high wind speed (mostly from
westerly directions) whereas they increase during periods with a more frequent occurrence of
winds from easterly directions. Because the lake level, i.e. the lake water volume, controls
the lake water carbonate system (Haberzettl et al., 2005), lake volume changes are archived
in the sedimentary record through changes in the sediment carbonate content. In a first
approximation the degree of supersaturation of the lake water with respect to calcite and thus
the potential for lake internal calcite precipitation is a function of lake water volume, which
was also confirmed by sediment trap studies. Hence, phases of high sedimentary calcite
concentration represent periods with low lake levels. However, a quantification of this
relationship is not admissible over long time intervals and we therefore attempt to combine
this approach of water volume reconstruction with the stable isotope approach (Mayr et al.,
2007a).
Already funded is a new project in the framework of the DFG priority programme
“ICDP” that will start in February 2007 with the investigation of short sediment cores (46
gravity cores of up to 49 cm length). It is called “Analysis of sediment areal distribution in
Laguna Potrok Aike” (ASADO). This proposal will bring forward our understanding of
PASADO – Full ICDP Drilling Proposal
7
processes controlling the spatial sediment distribution, geochemical sediment characteristics
and nutrient availability in the modern maar lake. Moreover, the spatial distribution of pollen
and diatoms as well as of the stable isotope signal will be investigated. In view of PASADO
this knowledge is vital for a thorough understanding of the long sediment record to be drilled
from the deep central lake basin.
Water chemistry and stable isotope data of surface waters from 23 lakes in the
Patagonian steppe, but also from wells, springs, streams as well as precipitation,
groundwater and atmospheric water vapour were sampled for isotope analyses (Mayr et al.,
2007a; Zolitschka et al., 2006b). Such a stable isotope approach can be used for estimating
the water balance of lakes. Obtained data imply that the isotopic composition of rainfall in
south-eastern Patagonia is predominantly determined by precipitation amount and moisture
source area. For the investigated area, the first meteoric water and evaporation lines in δ2H
vs. δ18O space were derived (Fig. 6).
For a better interpretation of biological proxies and to make available quantitative climate and
environmental reconstructions, Argentine colleagues are developing training sets for
diatoms, chironomids and pollen in order to develop transfer functions. These investigations
are related to analyses of modern water, surface sediment and sediment or pollen trap
samples from different seasons of Laguna Potrok Aike but also from a wide variety of other
lakes in southern Patagonia.
Fig. 6: Stable isotope values of precipitation
(Río Gallegos), surface water, groundwater
and atmospheric vapour in δ2H vs. δ18O space
(Mayr et al., 2007a). Precipitation data plot on
the given Local Meteoric Water Line (LMWL),
surface waters on a Local Evaporation Line
(LEL).
3.4 Seismic investigations
Four seismic surveys were carried out between 2003 and 2005 at Laguna Potrok Aike (Figs.
2, A2, A10) in order to reveal the general geometry of the maar lake and its bedrock and to
characterize the internal structures and thicknesses of lacustrine sediments, their spatial
distribution and possible lithologies. Different seismic methods were combined to obtain both
high-resolution and deep penetration acoustic data which are critical in terms of finding ideal
drill sites that provide undisturbed successions of lacustrine sediments. In early 2003 the
subsurface of Laguna Potrok Aike was investigated with a high-resolution 3.5 kHz seismic
surveying system. The second seismic campaign took place in Feb. 2004 and used two
parallel 1 in3 airguns. To further increase seismic penetration, additional single-channel
sparker data were acquired in Dec. 2004. Finally, in order to obtain a better insight into the
general maar geometry and the deeper sedimentary layers, an additional seismic pre-site
survey was carried out in March 2005 with a 40 in3 Mini-G airgun as acoustic source. The
results of this deep seismic survey reveals an at least 400 m thick lacustrine sediment infill.
The seismic stratigraphy and lithologic interpretations are summarized here. For detailed
results including selected seismic lines please refer to chapters A1 and A2 in the appendix.
PASADO – Full ICDP Drilling Proposal
8
Two major seismic stratigraphic units (Units I and II) are identified in the seismic
sections (Fig. 7). Unit I (with Subunits I-a to I-d) is of lacustrine origin, while Unit II consists of
the surrounding bedrock that was fractured and ejected during the phreatomagmatic eruption
forming the lake's depression. The lacustrine subsurface of the different morphobathymetric
areas (lake shoulders, slopes, deep basin) cannot be physically connected, because the
continuity of seismic reflections cannot be traced across the steep slopes.
Fig. 7: Interpreted line drawing of N-S multi-channel seismic reflection profile AWI-20058230 with
proposed drill sites PTA2 and PTA3 (cf. Fig. 2). The diatreme flank (in yellow) is well-defined in the
northern but not visible in the southern part of the lake.
Lacustrine Unit I (I-a to I-d):
Subunits I-a and I-b can only be discerned on the lake shoulders, where they are separated
by a major unconformity (Fig. A3). There, the upper ~5-10 m that define I-a consist of
draping, slightly basinward dipping layers that terminate laterally when the slope becomes
steeper. This unit conformably overlies an erosional unconformity, which persistently occurs
around the entire lake truncating reflections of the underlying upper slope section (Fig. A4A).
The consistent water depth of ~35 m that marks the outcrop of the erosional unconformity
clearly points towards a significant lake level lowering to near that depth. During this phase,
subaerial exposure led to the erosion of the upper slope sediments of Subunit I-b that have
been deposited during previous lake level highstands. Because the depth of -35 m
represents the deepest observed erosion, it is certain that the lake level did not fall beyond
that depth and that at least during the more recent history represented by Subunits I-a and Ib, Laguna Potrok Aike never fell dry. Several lens-shaped convex upward features occurring
on the unconformity mark paleoshorelines (Fig. A4B) formed during a stepwise transgression
following the -35 m lowstand. Sediment cores have been taken across this unconformity (Fig.
A7) and provide timing and the lithologic response to these lake level fluctuations.
In the central basin, all seismic reflections of the entire lacustrine infill (Unit I) bend
slightly upward towards the edges of the basin indicating a bowl-shaped layer-cake
sedimentary architecture that gradually becomes infilled without major unconformities. Here,
Subunits I-a and I-b are merged into one Subunit I-ab, because neither an unconformity nor
a detectable correlative conformity separates them. Acoustic velocities vary around 1550 m/s
indicating unconsolidated lacustrine sediments. Within Subunit I-ab, seismic data indicates
well-layered sediments that are interrupted in some areas by local mass flows (Figs. A3,
A20) occurring at six stratigraphic levels (S0-S5). The undisturbed central part of Subunit Iab has been recovered in a 19 m long core (Fig. A7). Interpreting the multi-channel airgun
data, the deeper parts of Subunit I-ab extend down to 50-60 m below the central plain of the
lake. Further mass movement deposits can be recognized mainly in the western, southern
and eastern parts close to the steep diatreme flanks. Pelagic sedimentation dominates in the
PASADO – Full ICDP Drilling Proposal
9
central and northern parts. The boundary between I-ab and I-c is non-erosive with I-ab
forming downlaps onto I-c from the eastern and western parts of the lake, pointing at a
significant lake level change (Figs. A11, A12). Within this deeper section, I-c is a rather thin
sedimentary package (approx. 20 m) that forms onlaps onto the underlying Subunit I-d in the
eastern part of the lake, while this contact is conformal in north-south direction. Subunit I-c,
probably deposited during a lowstand, has seismic velocities of ~1600 m/s characteristic for
unconsolidated lacustrine mud. The boundary between I-c and I-d remains obscure in the
western part of the central plain due to limited acoustic penetration. Similar to I-ab, I-d is
characterized by well-stratified sediments intercalated with mass movement deposits mainly
in the parts close to the diatreme flanks (Fig. A11). Its upper boundary is non-erosive; the
lower boundary cannot be observed because it is masked by multiples in some areas and
obscured due to limited acoustic penetration in others. This acoustic blanketing occurs
mainly in the central and western part of the lake and might point to some free gas, but
alternatively, could also be an indicator for thick coarse-grained deposits or tephra layers.
Bedrock (Unit II):
The bedrock forming the steep diatreme flanks consists of the well-layered sandstones of the
Santa Cruz Formation in the lake surroundings. The distinct facies change between the
slightly dipping, bedded sandstone and the smaller scale layers of the lacustrine sediments
resembles the facies changes in other maars (e.g. Messel Pit and Baruth Maar, Germany;
Wiederhold, 2003; Schulz et al., 2005). The boundary between the diatreme flank and the
lacustrine sediments is best visible in the northern and eastern part of the lake while it is
much less pronounced in the western and southern parts where it is buried below thick
packages of mass movement deposits (Figs. A11, A12). These packages tend to weaken the
acoustic penetration making it difficult to distinguish correctly between lacustrine layers and
bedrock bedding. Acoustic velocities of the sandstone bedrock are around 3000 m/s.
Maar geometry and anticipated deeper strata:
The site survey data indicate that Laguna Potrok Aike is characterized by similar geometries
like other investigated maars (Fig. A13), e.g. the Messel Pit and the Baruth Maar in Germany
(Wiederhold, 2003; Schulz et al., 2005). Seismic surveys as well as deep drillings in both of
these maars revealed a typical succession of maar-related lithologies followed by lacustrine
sediments (Pirrung et al., 2003) so that we anticipate similar successions in Potrok Aike
maar as well: (i) Lacustrine strata at the top are dominated by pelagic sedimentation in the
upper layers and intercalated with or even dominated by mass movement deposits (debris
flows and turbidites) in the deeper layers. The entire lacustrine sediment package has
thicknesses of around 250 m in both cases with acoustic velocities of ~1500-1600 m/s in the
pelagic sediments and up to 2400 m/s in the mass movement-dominated deposits
(Wiederhold, 2003; Schulz et al., 2005; Goth et al., 2003). (ii) Lapilli tuffs and stratified
collapse breccia that are formed immediately after the phreatomagmatic eruption as fallback
and slope failure sediments. The boundary between these strata and the overlying lacustrine
sediments is well defined by an abrupt increase to higher acoustic velocities of 3000 to 3500
m/s. (iii) Unstratified diatreme breccia with velocities in the range of 3000 to 3500 m/s,
related to the phreatomagmatic eruption and subsequent collapse of the crater.
During preparation of a velocity model for stacking of the multi-channel data of Laguna
Potrok Aike, observed velocities did not exceed 1800 m/s down to at least 600 ms twt in the
central part of the lake, i.e. in the part between the steep diatreme flanks. Stacking and
deconvolution using the derived velocity model, unfortunately, could not attenuate the
multiples well enough to make deeper strata visible in the processed seismic sections. In any
case, the lack of higher velocities points at lacustrine muds down at least 400 m below lake
floor in the central part of the lake as the deeper, maar-related strata would require velocities
as high as 3000 m/s according to the typical lithological success
PASADO – Full ICDP Drilling Proposal
10
3.5 Sediments
A 19 m long piston core from the central 100 m deep basin of Laguna Potrok Aike provides a
calibrated basal radiocarbon age of almost 16,000 cal. BP (Figs. 8, 9). In general, the
sediment record consists of clayey and sandy silts becoming slightly coarser with depth (Fig.
8). Only tephra layers and reworked volcanic ashes comprise fine to medium sand. The
sediment is minerogenic silt with mostly <4% and rarely up to 10% total organic carbon
(Haberzettl et al., 2007a). The carbonate content can be as high as 33% (Figs. 10, 11: TIC x
8.33). The multi-channel seismic survey indicates a thickness of the lacustrine sediment
sequence of ca 400 m. Based on the age-depth relationship established by Haberzettl et al.
(2007a) for the sediment record from the centre of the lake (Fig. 9), two different estimations
are possible for the entire sediment record that will be recovered with the GLAD800:
Fig. 8: Lithology of the composite sediment record from Laguna Potrok Aike (piston core PTA-03/12)
including medians of calibrated radiocarbon dates (Haberzettl et al., 2007a).
PASADO – Full ICDP Drilling Proposal
11
Fig. 9: Age-depth model (Haberzettl et al., 2007a, modified) based on calibrated radiocarbon ages,
volcanic ash layers and optically stimulated luminescence dating (OSL).
•
Assuming 400 m of continuous sedimentation and an onset of lacustrine deposition
shortly after formation of the maar around 770 ka, we estimate a linear sedimentation
rate of 0.52 mm yr-1;
• If we estimate the onset of sedimentation by extrapolating the linear sedimentation rate of
1.05 mm yr-1 that was determined for the last 16,000 years to the entire record of 400 m,
we yield a basal age of ca 380 ka. As we have no indications for erosional hiatuses in the
deep lake basin due to desiccation, we assume that compaction, which has not been
taken into consideration for this calculation, is the main reason for this underestimation.
Another option is that sediment thickness could be more than 400 m.
Altogether, estimates demonstrate that the sedimentary record from Laguna Potrok Aike
covers at least three and maybe up to seven glacial to interglacial cycles, perhaps even back
to the Brunhes/Matuyama boundary and thus will be unique for extra-tropical South America.
High resolution seismic studies revealed an unconformity in a subaquatic lake level
terrace of Laguna Potrok Aike. This unconformity in the terrace located approximately 35 m
below the present lake surface can be traced all around the lake. It is characterized by 3-4 m
of almost horizontally layered sediments above and sediments dipping towards the lake
centre below. Piston cores recovered from such a site verify this unconformity. Sediments
above the unconformity consist of dark brown to black silts, whereas below the unconformity
greenish brown fine sands dominate (Haberzettl et al., 2007b). Dating confirms this
unconformity and reveals a hiatus of almost 40,000 years with continuous deposition starting
again around 7000 cal. BP (Haberzettl et al., 2007b). Recently, the oldest radiocarbon age of
44,800 BP was confirmed by an OSL age of 53 ka from the base of the record. All
sedimentological data support the interpretation that the lake level was considerably lower
than today before 7000 cal. BP which caused the presence of a hiatus with unknown
duration in this shallow part of the lake.
3.6 Paleoclimatic and environmental reconstruction
The 19 m long (Fig. 8) and multiple-dated (Fig. 9) piston core profile from Laguna Potrok
Aike exhibits distinct changes in sedimentary parameters that indicate climatic and
environmental variabilities. Monitoring data suggests that the content of total inorganic
carbon (TIC) mirrors changes of the lake’s water volume and reflects variations in the
PASADO – Full ICDP Drilling Proposal
12
hydrological cycle. Thus it is possible to reconstruct hydrological variations for the last two
millennia (Fig. 10) and for the entire Holocene and the Late-Glacial (Fig. 11). Recent studies
of other lakes further to the northwest (Lago del Desierto, Laguna Chaltel, Laguna de las
Vizcachas; all unpubl. own data) indicate that this is at least a regional signal caused either
by latitudinal shifts or by intensity variations of the SHW.
Fig. 10: Total inorganic carbon (TIC)
record as a proxy for lake level
fluctuations reflecting hydrological
variations during the last 1600 years
based on a 1 m gravity core from
Laguna Potrok Aike (Haberzettl et
al., 2005).
Fig. 11: Total inorganic carbon (TIC)
and Titanium (Ti) records for the late
Weichselian and Holocene of
Laguna Potrok Aike as indicators for
lake level fluctuations (TIC) and
detritic sediment input (Ti). Both
proxies reflect wet conditions for the
time prior to 13,000 cal. BP (the lake
had an outflow) and moist conditions
for the early Holocene (no outflow
anymore), whereas the Late-Glacial
and the Holocene since 8700 cal. BP
are
characterised
by
marked
dry/moist cycles (Haberzettl et al.,
2007a, modified).
These data demonstrate that the region experienced drastic environmental changes in
the past. The record from Laguna Potrok Aike suggests moist conditions during the LateGlacial and the early Holocene (16,000-8700 cal. BP) interrupted by drier conditions before
the beginning of the Holocene (13,200-11,400 cal. BP). Data also imply that this period was
a major warm phase in south-eastern Patagonia approximately contemporaneous to the
Younger Dryas chronozone in the Northern Hemisphere (12,700-11,500 cal. BP). The most
drastic changes of the record start with the deposition of the Mt. Burney tephra generating
intensified erosion. Thereafter, the lake level fell to its lowest Holocene position (8650-7300
cal. BP). After a transgression period the lake level was extremely variable. The last
exceptionally high lake level is ascribed to the Little Ice Age (Fig. 10), which was the most
PASADO – Full ICDP Drilling Proposal
13
humid phase since the early Holocene (prior to 8650 cal. BP). This interpretation is
supported by pollen and diatom analyses (Wille et al., 2007).
High-resolution analyses of allochthonous pollen (Andean forest taxa – AFT, i.e. mainly
Nothofagus) deposited in Laguna Potrok Aike reflect the variability of zonal wind intensities
during the Holocene. These indicators for the strength of SHW co-vary on centennial
timescales with C/N ratios and Ti contents, interpreted as differential organic matter sources
and minerogenic input to the sediment, respectively (Fig. 12). The correlations underline a
linkage between hydrological variability and west wind variability in Extra-Andean Patagonia
(Mayr et al., 2007b). When the SHW intensity was strong, more arid conditions prevailed (low
Ti) and more littoral organic matter was deposited (higher C/N) due to lower lake levels. A
shift to generally more intense SHW suggests intensification to modern wind conditions at
that latitude around 9200 cal BP (Fig. 12). Accordingly, the period with most intense SHW
was 8.7–7.4 ka cal BP coinciding with the suggested lowest Holocene lake level (Haberzettl
et al., 2007a). During periods with weakened SHW, air masses from easterly directions
reached Laguna Potrok Aike more frequently giving rise to enhanced precipitation (high Ti)
and dominance of algal organic matter (low C/N) prevailing during periods of high lake levels.
Hence, the coherence of Ti and C/N variations with the AFT record allows a detailed
reconstruction of SHW intensity and its impact on the ecosystem (Mayr et al., 2007b).
Fig. 12: Andean forst taxa (AFT) pollen variations as AFT flux (logarithmic scale) and AFT index (a)
compared to C/N ratios (b) and Ti contents (c). Interpretation of proxies to the right; OM: organic
matter (Mayr et al., 2007b).
The record from Laguna Potrok Aike demonstrates that the SHW strength varied on
centennial to multi-centennial time scales. Comparable quasi-millennial periodicities of
climate proxies are well-known from Antarctic ice cores (Masson et al., 2000; Delmonte et
al., 2005) suggesting changes in southern hemispheric atmospheric circulation as a
fundamental control mechanism. Compared to other proxy records in the South American
realm from continental (e.g. Jenny et al., 2003; Gilli et al., 2005) and marine (Lamy et al.,
2001) sites, our record shows an earlier onset of intensified SHW in the Holocene. Data
further suggest that SHW were much more variable during the Holocene than previously
inferred from other records.
PASADO – Full ICDP Drilling Proposal
14
3.7 Climate modelling
In the framework of the project MIDHOL the hydrological regime at Laguna Potrok Aike has
been analyzed in terms of precipitation and its link to large-scale atmospheric circulation.
Transient simulations were done in which a combination of orbital, solar and greenhouse gas
forcing were used to drive the global coupled atmosphere-ocean model ECHO-G for the midHolocene (7000-4500 cal. BP). Results were compared to a quasi-equilibrium pre-industrial
control simulation with constant conditions of 1750 AD.
The coarse horizontal resolution (approx. 300 x 300 km) of the GCM is of special
concern for the complex topographic terrain over southern Patagonia. Thus the climate
model output related to hydrological variables (precipitation, evaporation) could not directly
be used for comparison with local conditions derived from sediment proxy data, i.e. lake level
variations. For the mid-Holocene lake levels were reconstructed to have been lower
compared to pre-industrial times (Haberzettl et al., 2007a).
To overcome the scale-mismatch between the large scales of the climate model and
the local scale of the proxy data, a downscaling approach was applied to link the large-scale
atmospheric circulation (LSC) with local precipitation. This approach includes two steps:
First, a statistical downscaling model was calibrated and validated with observational
meteorological data. Here statistical transfer functions have been setup between large-scale
sea level pressure over southern South America and precipitation at Laguna Potrok Aike for
the second half of the 20th century. In a second step these transfer functions have been
applied to the simulated LSC of the ECHO-G model.
Fig. 13 left side: Time series of estimated precipitation for the orbital-forced simulation (ORB) based
on simulated large scale circulation during the mid-Holocene at Laguna Potrok Aike for Dec.-Feb.
(DJF, upper panel) and June-Aug. (JJA, lower panel). Dashed lines are the 95% confidence intervals
related to the uncertainties of downscaling models. Note reduced precipitation during DJF and
increased precipitation during JJA compared to pre-industrial times (CONPRE). Right side:
Differences in vertical cross-sections of zonal winds along 70° W between the situation at 6000 cal.
BP and pre-industrial times for DJF (upper panel) and JJA (lower panel). Note increased zonal winds
over southern South America during DJF as opposed to reduced winds during JJA.
PASADO – Full ICDP Drilling Proposal
15
An advantage of the statistical downscaling model is the analysis of the driving
mechanisms between LSC and precipitation. Specifically for the situation at Laguna Potrok
Aike it was realised that increased westerly winds are associated with reduced precipitation
and vice versa. However, as also shown by the downscaling model, this link is only
moderate, because only 25% of the variability of precipitation at Laguna Potrok Aike can be
explained by changes of LSC on a monthly basis.
The large-scale information of the climate model related to SHW was directly used for
comparison with the large-scale hypothesis formulated on information derived from proxy
data for the mid-Holocene. These hypotheses are related i) to a year-round northward
position (Markgraf, 1993; Markgraf et al. 2003) of SHW and ii) to an increased seasonality
(Schäbitz, 1999; Mancini et al., 2005) of SHW.
Results of the estimated precipitation based on the downscaling of the simulated LSC
are given for southern summer (Dec.–Feb.: Fig. 13 upper panel) and winter (June–Aug.: Fig.
13 lower panel) for the period 7000–4500 cal. BP. In the right panel vertical cross-sections of
differences of zonal winds along 70°W between 6000 cal. BP and pre-industrial times (AD
1750) are given for the same seasons.
During DJF slightly reduced precipitation is evident compared to pre-industrial times,
whereas during JJA increased precipitation is observed. The annual precipitation difference
(not shown) shows slightly increased precipitation and thus seems to be inconsistent with
reconstructed lower lake levels at Laguna Potrok Aike. However, since precipitation cannot
explain the full range of lake level changes, evaporation needs to be taken into account to
compare modeling (downscaling) results and proxy reconstructions on a consistent basis.
An explanation for precipitation changes during the mid-Holocene are changes of zonal
winds. Increased westerly winds at Laguna Potrok Aike are associated with reduced
precipitation and vice versa. Here climate simulations indicate reduced westerly (zonal)
winds during JJA and increased westerly winds during DJF over southern South America.
The situation is different further to the north, where winds are increased during JJA and
reduced during DJF. Therefore, simulations support the large-scale proxy hypothesis related
to an increased seasonality of SHW during the mid-Holocene.
4. Importance of the study area
In the southern hemisphere long, continuous and high resolution series of terrestrial
paleoclimatic data are scarce and only slowly emerging, e.g. from New Zealand (Horrocks et
al., 2005; Shulmeister et al., 2004; Turney et al., 2006). Such records are a key to a better
evaluation of teleconnections and inter-hemispheric differences. In recent studies it emerged
that for a proper understanding of the global climate system Southern Oceans play a key role
(Kaiser et al., 2007, Knorr and Lohmann, 2003, White and Peterson, 1996). The most
extreme oceanic character globally is encountered between 40°S and 60°S where 98% of
water are juxtaposed to 2% of land: Patagonia and a few small islands. This region close to
the Andean volcanic chain is subject to shifts in polar and mid-latitude pressure fields and
precipitation regimes. It also is affected by the El Niño Southern Oscillation (ENSO)
phenomenon (Ariztegui et al., 2007) and by the Antarctic Oscillation (AAO; Jones and
Widmann, 2003). Patagonia thus can potentially provide unique terrestrial records of
variations in (1) climate, (2) hydrology and (3) deposition of aeolian dust. Such records also
may act as a cornerstone for palaeodata-model comparisons (Wagner et al., submitted.).
Additionally, links can be established to ice cores from Antarctica and to marine records from
the Southern Oceans where dust and tephra of Patagonian provenance have been detected
(Basile et al., 1997, Diekmann et al., 2000, Narcisi et al., 2005).
For southernmost South America lake studies are still rare and extend in time not
beyond the Late-Glacial. At Lago Cardiel a 3,5 kHz seismic survey together with 14C-dated
sediment cores indicate that this 75 m deep lake contains only sediments spanning ~20,000
years and almost dried out around 13,000 cal. BP (Gilli et al., 2001, Gilli et al., 2005a, b;
Markgraf et al., 2003). Similarly, investigations of lake sediment cores from the Gran Campo
PASADO – Full ICDP Drilling Proposal
16
Nevado area in Chile (53°S) provide records for Late-Glacial and Postglacial times (Kilian et
al., 2000). Only for Laguna Potrok Aike a 16,000 year record with high temporal resolution
(Haberzettl et al., 2007a) and a second record of lower resolution back to MIS 3 with a hiatus
of unknown duration exists (Haberzettl et al., 2007b). Thus continuous records from southern
South America that reach back far beyond the onset of the Late-Glacial are still missing.
In areas not scoured by young glaciations (Fig. 3), volcanic crater lakes are ideal for
the recovery of long and continuous paleoenvironmental records. Their potential has been
demonstrated for the West Eifel Volcanic Field, Germany (e.g. Negendank and Zolitschka,
1993; Zolitschka et al., 2000), for the Massif Central, France (e.g. Thouveny et al., 1994), for
southern Italy (e.g. Allen et al., 1999; Guilizzoni and Oldfield, 1996; Zolitschka and
Negendank, 1996), for China (e.g. Mingram et al., 2004a, b) and for New Zealand (e.g.
Horrocks et al., 2005). Laguna Potrok Aike is the only lake in the Pali Aike Volcanic Field with
a continuous sedimentary record potentially covering several glacial to interglacial cycles.
In addition to climatic and paleoenvironmental research related to its lacustrine
deposits this maar opens yet another window for research: investigation into formation,
structure and composition of a relatively young maar-diatreme structure. Scientific drilling
was never before carried out into the deep diatreme underneath a modern maar lake.
Studies of maar structures currently include only records from Tertiary dry maars (e.g.
Pirrung et al., 2003; Schulz et al., 2005). However, a first comparison of the lithology of the
scientific drilling into the Messel Pit, an Eocene maar structure in Germany, fits well with the
deep seismic structure of Laguna Potrok Aike (Fig. A13). Altogether, the global importance of
deep scientific drilling into the maar structure of Laguna Potrok Aike is based on two
elements:
• Quantitative climate reconstruction in combination with proxy-model intercomparison;
• Investigation of the phreatomagmatic formation and early sedimentation of a young maar.
5. Scientific motivation and goals of the drilling project
The proposed project PASADO is an interdisciplinary scientific deep drilling and analytical
laboratory effort with wide international participation. Laguna Potrok Aike has been
recognised as an outstanding geological site to study the continental climate and
environment of South American mid-latitudes continuously and with high temporal resolution.
The critical role of the Southern Hemisphere for climate reconstructions is generally
accepted, but links between tropical and Antarctic climates at decadal to centennial
timescales across different archives have yet to be established. Especially with terrestrial
records an understanding of long-term environmental changes on the southern continents is
still in its formative stages as proxy records are both spatially diffuse and temporally
discontinuous. The increasing awareness of major inter- and intra-hemispheric disparities in
the timing of climatic signals and forcing that influences land, ocean and ice core records
underscores the need for the proposed integrated effort to explore the dynamics of the
Southern Hemisphere climate system. Such a paleoclimatic record from diverse proxy
sources provides a much wider range of realisations needed to describe and understand the
full range of natural climate system behaviour. Moreover, for the first time, it will be possible
to drill through the entire lacustrine sedimentary sequence and into the underlying
volcaniclastic breccias to investigate the phreatomagmatic formation of a maar structure and
to study the processes of early sedimentation in a maar.
With conventional coring equipment it was possible to obtain 19 m of sediment in
100 m of water depth covering the last 16,000 years. Now we are at a stage to implement
another dimension to reach our goals and drill the entire sediment sequence of ca 400 m of
lacustrine sediments plus ca 200 m penetration into the volcanic breccias underneath. To
recover such a suite of long cores from Laguna Potrok Aike we have to use scientific drilling
equipment (GLAD800) operated by DOSECC in the framework of the ICDP. Our well
established local collaboration with INTA, UNPA and Capt. Moreteau and his crew will
augment the process of drilling by e.g. providing logistical support and room for the field
PASADO – Full ICDP Drilling Proposal
17
laboratory, building the dock at the lake shore and running a vessel to shuttle the crew and to
tow the drill rig.
Once sediment cores have been recovered, the drill holes will be analysed with an
extensive down hole logging programme. Sediment cores themselves will be scanned on-site
with a multi sensor core logger (MSCL) and archived following standard protocols. After
shipping to Bremen, cores will be opened and analysed non-destructively. Only after this has
been accomplished, discrete sampling will start including a wide range of internationallybased interdisciplinary analyses. Due to the unique geographic situation of Laguna Potrok
Aike we envisage the following scientific goals for PASADO:
Quantitative climate and environmental reconsystructions:
• Establish a chronology from orbital and suborbital (multimillennial) down to decadal
timescales supported by multiple dating (e.g. 14C, OSL, Ar/Ar) and stratigraphic
correlation (e.g. pollen and paleomagnetic records);
• High-resolution quantitative reconstruction of temperature (based on chironomids and
biomarkers) as well as precipitation and hydrological variations (based on total inorganic
carbon, pollen and stable isotopes);
• High-resolution quantitative reconstruction of terrestrial vegetation (pollen) and fire history
(charcoal);
• Development of records of dust storm events and volcanic eruptions based on their
mineralogical and geochemical fingerprints;
• Reconstruction of paleosecular variation of the Earth’s magnetic field;
• Establish marine – ice core – terrestrial linkages
o by developing models that allow to trace atmospheric dust from Patagonian sources
to marine sediments (South Atlantic) and ice cores (Antarctica) and
o by comparing the PASADO data set with the high-resolution EPICA (2004) ice core
record from Antarctica focusing (1) on the magnitude and abruptness of
glacial/interglacial transitions and (2) on the periodicities and cycles during glacials
and interglacials;
• Statistical comparison of PASADO data with climate simulations from GCMs to establish
links between climate variability and climate forcing factors such as changes in the
Earth’s orbit, solar output and greenhouse gas concentrations. Questions to be answered
include:
o Are latitudinal shifts in the position of the SHW reproducible?
o Are synoptic-scale phenomena like polar outbreaks and their recurrence patterns
represented?
o Can synchronous interhemispheric climatic linkages be detected to assess the role of
ice sheets, oceanic and atmospheric circulation and astronomic forcing on climate?
Phreatomagmatic history:
• Processes related to phreatomagmatic maar explosions are investigated to
o reconstruct the geometry of diatreme structures in sedimentary host rocks (first
opportunity to drill a maar structure in the framework of the ICDP) in order to establish
the evolution of maar formation and to proof the models for maar diatrems;
o link internal processes (volcanism, tectonics) with external processes (glaciation);
o obtain more precise age constraints on the formation of the maar and on the last
glaciation at 52°S;
• Investigation of early sedimentation in a young (~770 ka) maar lake;
• Contribution to the understanding of post-sedimentation and compaction history of
Quaternary maar sediments.
To achieve these goals scientifically, we apply for an accompanying science programme
including down hole logging and logging of all sediment cores in the field with a MSCL.
Additionally, laboratory-based analyses will be carried out in subsequent international
research projects that will make intensive use of the recovered sediment cores. To achieve
these goals technically, we apply for a scientific drilling with the GLAD800 system:
PASADO – Full ICDP Drilling Proposal
•
•
•
•
18
To drill the complete lacustrine sediment infill (ca 400 m) in triplicate from the centre of
the lake,
To drill the lacustrine sediment infill (ca 50 m) in triplicate from a 35 m lake level terrace
to better understand lake level fluctuations,
To drill into phreatomagmatic breccias and the maar diatreme at the central lake drilling
site from ca 400 to 600 m sediment depth and
To drill from the lake with an angle hole through the crater wall and into the basement
rocks.
6. Proposed work
6.1 Site selection and drilling strategy
The highest priority drilling site is located in the deep central basin (sites 2, 5: Fig. 2). Here
seismic data indicate deepest penetration of at least 400 m and this is also the site where
hiatuses related to lake level fluctuations are not expected. Therefore, this site offers best
conditions to recover a continuous and high resolution sediment record necessary to reach
all scientific objectives. Marginal to the deep central plain slump deposits have been detected
seismically. These areas will be avoided for drilling. Coring transects at Laguna Potrok Aike
is not feasible because basin flanks are rather steep and erosion is likely. Only the circumlacustrine lake level terrace at 35 m water depth provides another option for drilling (sites 1,
4: Fig. 2). Here an erosional hiatus has already been detected (Haberzettl et al., 2007b) and
we expect a discontinuous record. Linked to the profundal sediment record this site will give
important additional information about hydrological variations and thus improves the overall
interpretation. This location is scheduled to become the first drill site because the order of
drilling will be from shallow to deep. The third and last drilling site will be near the northern
end of the lake at 90 m water depth where an angle hole will be drilled through the crater wall
and into the basement rock (Lower Miocene fluvial sandstones, Santa Cruz Formation) to
investigate the transition zone that was formed during maar eruption (sites 3, 6: Fig. 2). This
drill site is dedicated for volcanological investigations. Similarly, after having penetrated into
400 m of lake sediments in the central basin (sites PTA08-2/5: Tabs. 1, 2), drilling continues
into volcanic breccias (sites PTA08-2C/5C: Tabs. 1, 2).
Tab. 1: Proposed primary drilling sites at Laguna Potrok Aike.
Drill
site
PTA
Latitude
(°S)
Longitude
(°W)
Water
depth
(m)
Depth of
penetration (m)
Water depth
+ penetration
(m)
No. of
holes
Total core
recovery
(m)
Drilling
days*
Logging
days**
min-max
08-1
08-2
08-2C
08-3
-51,9541
-51,9641
-51,9641
-51,9576
-70,3683
-70,3760
-70,3760
-70,3765
35
100
100
90
50
400
600
300
85
500
700
390
Total
3
2
1
1
7
150
800
600
300
1850
6
32
24
12
74
0.7-2.0
1.2-2.0
0.8-1.2
0.6-1.0
3.3-6.2
* Estimation of drilling days is based on 25 m per day.
**Estimation of logging days is based on data of Tab. 3.
Tab. 2: Proposed alternate drilling sites at Laguna Potrok Aike.
Drill
site
PTA
Latitude
(°S)
Longitude
(°W)
Water
depth
(m)
Depth of
penetration (m)
Water depth
+ penetration
(m)
No. of
holes
Total core
recovery
(m)
Drilling
days*
Logging
days**
min-max
08-4
-51,9549
-70,3889
35
50
85
3
150
6
0.7-2.0
08-5
-51,9642
-70,3778
100
400
500
2
800
32
1.2-2.0
08-5C
-51,9642
-70,3778
100
600
700
1
600
24
0.8-1.2
08-6
-51,9569
-70,3786
90
300
390
1
300
12
0.6-1.0
Total
7
1850
74
3.3-6.2
* Estimation of drilling days is based on 25 m per day.
**Estimation of logging days is based on data of Tab. 3.
PASADO – Full ICDP Drilling Proposal
19
Altogether, we propose to drill three sites (Fig. 2, Tab. 1). Three alternate sites have
been identified if a primary site has to be abandoned for technical, scientific or other
unforeseeable reasons (Fig. 2, Tab. 2). Sediment cores for climatic and environmental
studies will be recovered in triplicate to ensure a complete and overlapping sedimentary
record. For volcanological investigations one hole per site is sufficient. We intend to almost
exclusively use the hydraulic piston corer (HPC) for lacustrine sediments. However, near the
transition to volcanic breccias and for the basement rocks of the angle hole the Extended
Nose (EXN), Extended Core Bit (The Alien) or the Diamond Core Bit may come into action.
6.2 Site survey information
The proposed drilling sites were determined based on bathymetric (Fig. 2) and seismic data
(Figs. 7, A15-21). Penetration depths are listed in Tabs. 1 and 2. According to seismic
profiles and recovered piston cores we expect the following lithologies:
• Pelagic lake sediments: They are recognized on seismic data by a laterally-continuous,
reflective seismic facies and a “draping” geometry composed of variable amounts of
authigenic and biogenic calcite, silt- to clay-sized clastics and organic matter. The relative
percentages differ between lake level high- and lowstands. This sediment type has been
continuously deposited and will be the prime target for climatic and environmental
reconstructions (cf. Fig. 8).
• Volcanic ash layers: Tephra layers occur occasionally with a thickness ranging from less
than 1 mm up to several cm and vary in grain size from silt to sand (cf. Fig. 8). They are
very useful for core correlation and dating (tephrochronology) and can be distinguished
on seismic data.
• Turbidites and slump deposits: Due to the distal position of all sediment cores recovered
so far, classic turbidites related to flood-events have not been detected and are assumed
to play no role for the proposed drilling sites. Slump deposits, however, are present due
to the steep side walls of the lake basin and have been mapped in detail with seismic
data. Thus, drilling sites will be positioned in areas where these units are absent. At
greater sediment depths, where penetration of the seismic signal was insufficient to
image the sediment geometry in detail, slump deposits may be more common as the
basin gets narrower and steeper.
• Litoral lake sediments: At the 35 m lake level terrace we plan to penetrate through the
paleoshoreline. Larger grain sizes like coarse silt and sand as well as reworked
carbonaceous shells and plant macro fossils are likely. We do not expect that hard soil or
desiccation horizons occur, as this was not the case in the cores we recovered with
piston and gravity cores.
• Volcaniclastic breccias: Neither seismic nor former drilling operations penetrated deep
enough to reach down to this sedimentary unit. We assume that sediments are
comparable to investigated Tertiary dry maar records (Schulz et al., 2005). Following this
approach, breccias may consist of a series of clastic units including (from top to bottom)
debris flows, collapse breccias, lapilli tuff as well as stratified and unstratified diatreme
breccias.
• Fluvial sandstones: Uplift of the Andes caused the formation of Lower Miocene finegrained molasses-type fluvial sandstones of the Santa Cruz Formation. This rather soft
sandstone is believed to compose the basement underneath Laguna Potrok Aike.
Potential sources of hazards during drilling operations are thought to be minimum. Indeed,
the relatively minor penetration of the 3.5 kHz seismic system (Figs. A2, A7B) is not related
to the presence of gas but rather to tephra layers that seem to absorb considerable acoustic
energy. Weather should as well pose no significant hazard on drilling activities because the
lake is relatively small (7.6 km2) and thus has only a small fetch even though wind speed can
be significantly higher than 6 bft. Ideally, drilling should occur during summer. Weather
conditions are mostly good, although wind strengths increase until noon and then start to
decrease again. Precipitation is very low in general.
PASADO – Full ICDP Drilling Proposal
20
Logistically, trucks easily reach Laguna Potrok Aike. Paved roads exist from Buenos
Aires (where the equipment has to be cleared through customs) to Río Gallegos (2639 km).
Paved and dirt roads reach the lake from Río Gallegos (112 km), where trucks can almost
drive to the lake shore. Only the last 50 m to the shore need to be levelled and supported.
The lake itself has no harbour or any other facility. Therefore, a dock with electricity and
lighting needs to be built. A catamaran, R/V “Lago Cardiel”, is already on the lake and will be
available as a safety, shuttle and towing boat.
6.3 Geophysical downhole logging and log interpretation
Borehole logging in lacustrine sediments is essential to obtain continuous in situ physical and
chemical information around the borehole and to give an overview of the subsurface geology
at the drill sites. Data sets obtained by wireline logging with slimhole tools provide the
following information:
•
•
•
•
•
•
•
•
True vertical depths, precise depth locations of the bottom hole, measurements of
borehole dimensions and volume calculations provide a means for core re-orientation
and are necessary for monitoring the drilling process.
Precise core depths and corrections of core deformation resulting from the process of
coring (stretching and compressing).
Hole to hole correlation for multiple drill sites, detection of gaps in core recovery and
determination of a continuous profile. A composite stratigraphy for each drill site based
on triplicate coring will be established. Moreover, changes within overlapping core
sections help to interpret the lateral (spatial) lithological variability if any.
Characterisation of petrophysical properties of sedimentary rocks. These include
sediment composition, textures and facies, rock magnetic properties and porosities and
will be compared to later laboratory-based analyses on discrete sediment samples.
Interpretation will be related to compaction and diagenetic characteristics, stratigraphy,
unconformities and lithologic boundaries, identification of volcanic ash layers and
sequence stratigraphy.
Structural properties of drilled hard rock sections. The planned dipmeter, borehole
televiewer (BHTV) and caliper measurements will be used to determine the predominant
stress field. This can be used to achieve information, e.g. about volcanic processes
during the development of Laguna Potrok Aike.
Measurements of dip and orientation of sedimentary structures.
Construction of the “equivalent logging depth” which will be used in comparison with the
sediment core depth to correct the latter and to obtain the “true depth”.
Integration and calibration of seismic profiles and 3D modelling around boreholes. A
time/depth-calculation is needed to extrapolate the geological information of seismic
profiles into lateral direction. This is done using the vertical seismic profile (VSP), which
produces an exact velocity model.
Successful core recovery will depend strongly on good control of downhole conditions and
borehole stability during coring. Therefore, in situ downhole measurements of e.g. borehole
geometry and borehole dip are important to deal efficiently with potential drilling problems.
Geophysical logs will be available on-site and provide all the necessary quick stratigraphic
information.
All logging operations will be conducted with the equipment for geophysical
measurements in small-scale drill holes available at the Leibniz Institute for Applied
Geophysics (GGA) in Hannover (Wonik & Salge 2000; Wonik & Bücker 2000). Comparable
slimhole tools have already been deployed successfully with the GLAD800 drilling platform
during earlier expeditions and operate through its drill string. The winch has a cable length of
1200 m and all tools can be used in an open drill hole with a minimum diameter of 75 mm.
Logging tools will be lowered into the coring riser or the DLS rods (diameter: 101.6 mm) as
soon as the wireline coring, main hoist cables and the kelly are set aside. The power supply
from the diesel engine on board of the GLAD800 will be utilised as a source for electricity.
PASADO – Full ICDP Drilling Proposal
21
Heave compensation is not available for the GLAD800. But experience has shown that
swells of 1-2.5 m do not affect logging quality. Wave heights of more than 1 m very rarely
occur at Laguna Potrok Aike. Even if they should occur during the drilling period,
uncontrolled tool movements resulting in log depth shifts and incorrectly stacked records can
be avoided by logging during the usually calm nights.
The following methods for measuring physical parameters are available:
•
•
•
•
•
Radiometric method: natural gamma rays; contents of K, Th and U; bulk density; neutron
porosity; relative amounts of C, Ca, H, Fe, O, Si;
Acoustic method: sonic velocity; ultrasonic view of the borehole wall with the borehole
televiewer (BHTV); vertical seismic profile (VSP);
Electric method: resistivity (DLL); self potential; dip and direction of layers (dipmeter); IPeffect;
Magnetic method: magnetic susceptibility, magnetic field;
Other methods: borehole diameter (4-arm-caliper), salinity and temperature of the mud.
The vertical sampling rate of downhole logging is 5 cm on average. However, some methods
like the dipmeter have a higher sampling rate (2 mm). In a cased borehole only a small
number of the listed parameters can be measured because of the physical conditions. The
proposed logging program for PASADO will provide all involved scientists with a unique data
set for geological interpretation. Furthermore, geostatistical methods will be used to detect
cycles in logging data. With some restrictions even changes in sedimentation rate can be
determined (Molinie & Ogg, 1990; Wonik, 2001).
At every site logging operations will start immediately after the drilling has been
terminated. Logging schedules are listed in Tab. 3 based on a mean standard logging time
estimated at 50 m/h for five different slimhole sondes and calculated for the respective water
and total drilling depths. Additionally, 4 hours are added to set up the logging equipment on
the drill rig plus safety time for tool repairs or other unforeseeable events (10 hours).
Tab. 3: Proposed logging schedule for the anticipated three drilling sites at Laguna Potrok Aike.
Drill site
PTA 08-1A
PTA 08-1B
PTA 08-1C
PTA 08-2A
PTA 08-2B
PTA 08-2C
PTA 08-3
Sum
Water
depth (m)
Sediment
depth (m)
Logging time
(min.)
35
35
35
100
100
100
90
50
50
50
400
400
600
400
1950
102
102
102
600
600
840
600
2946
Installation and
safety time
min-max (min.)
240-840
240-840
240-840
240-840
240-840
240-840
240-840
1680-5880
Total time for logging
min-max
(min.)
342-942
342-942
342-942
840-1440
840-1440
1080-1680
840-1440
4626-8826
Preliminary on-site processing will be carried out in the field to provide first lithologic
and stratigraphic interpretations. Additionally, correlation with seismic reflectors and MSCL
data gives information about lithologic boundaries, occurrence of tephra layers and makes
available a preliminary characterisation of the sediment record.
6.4 Initial field-based investigations
For PASADO we will need a shore-based laboratory which will be set up in a shed on the
premises of the INTA Potrok Aike field station. The shore-based laboratory will be equipped
with the GEOTEK MSCL available through the ICDP operational support group. In addition to
the MSCL, pore-water geochemistry and basic sedimentological investigations like
preparation and microscopic investigation of smear slides will be carried out.
Logging of physical properties of sediment cores is part of the established standard
methods of scientific deep drilling projects, e.g. IODP, ICDP, CRP and ANDRILL (e.g. Hodell
et al., 2006; Huvenne et al., 2006; Niessen & Jarrard, 1998; Niessen et al., 1998). During
drilling, the destruction-free parameters like density, p-wave velocity and magnetic
PASADO – Full ICDP Drilling Proposal
22
susceptibility are important in order to correlate cores and core segments (e.g. Pälike et al.,
2005). Analysis of physical properties is done with the calibrated and computer-controlled
MSCL (Weber et al., 1997; Best & Gunn, 1999; Zolitschka et al., 2001). Resolution depends
on sensor type and varies between 0.5 mm and 10 cm. Physical properties will be measured
in the field immediately after core recovery for all drill sites using the MSCL. Some proxies
will be processed on-site to assist in drill-strategic and drill-technical decisions. Almost realtime on-site core logging is needed to combine the individual 3 m long core sections to form
one composite profile by aligning the signals of core-logging data from triplicate drill sites.
This is important to compensate for the small-scale loss of sediment at core breaks even with
a core recovery rate of 100%. The relevance of core logging increases if core recovery is
<100%. This procedure guarantees a recovery of continuous core sections which are
essential for high-resolution paleoclimate investigations. Moreover, this approach produces
an equivalent logging depth which has the advantage to correct for stretching and squeezing
within core sections and between drill holes and thus provides the most accurate depth
scale. Logging parameters will also provide first ideas about lithologies and thus can be used
to infer e.g. paleoclimatic changes. Three main topics for analysis and interpretation of
physical properties have been established:
•
•
•
Physical properties of long cores are well suitable for statistically robust analyses to
recognize
o Different lithological units (e.g. by cluster analysis: Bücker et al., 2001) and
o Milankovitch and sub-Milankovitch cycles (Hinnov, 2000);
Parameters such as p-wave velocity and density are needed to combine sediment cores
with seismic sections. This allows to project the one-dimensional (temporal) information
derived from core analyses into temporal-spatial variations visible in seismic profiles;
Certain physical parameters can also be used as a simple and fast proxy of climate
induced changes in the investigation area instead of using cost-intensive and timeconsuming laboratory analyses. The use of p-wave velocity and density as a proxy for
grain size variations that was established at IODP cores may help to reveal Milankovitchdriven glacial-interglacial cycles. Grain size distributions are more precisely determined
when investigating the spectral information and sonic attenuation of p-wave transmission
seismograms in addition to the simple p-wave travel time (Breitzke 2000; Breitzke et al.,
1996).
After drilling, all field measurements will be processed at respective home laboratories. Grain
size distribution and other chemical and physical proxies will be measured on selected
samples with conventional methods. Calibrated physical properties will then be much better
understood and can be interpreted in terms of exceptionally high resolution variations in the
sedimentary environment.
Geochemical investigations will also be carried out on-site. For these analyses a part of
the core catcher sample will be used to squeeze out the pore water and to measure pH,
electric conductivity, salinity and alkalinity. This information will provide yet another set of
immediate data to support preliminary field-based interpretations. The pore water will be
retained and later on analysed in the laboratory for its stable isotope composition.
On-site sedimentological analyses will be confined to determination of the weight of the
core sections and the core catcher sample to estimate average densities of recovered
sediments and to the production of smear slides. In the field laboratory the smear slides will
be analysed microscopically and add substantial information to the MSCL data.
Microscopical data may include qualitative estimates about grain size distribution, occurrence
of volcanic tephra layers or presence of autochthonous calcites as well as indicate remnants
of biological productivity like pollen, diatoms, chironomids, ostracods, aquatic snails or litoral
plant remains.
6.5 Core storage, archiving and further lab-based processing
The objective of PASADO is to recover high quality cores from Laguna Potrok Aike and to
ensure that they will be archived in the best possible manner to be available for a wide range
PASADO – Full ICDP Drilling Proposal
23
of future investigations. Therefore, once handed over by the drillers to the scientific team
onboard of the GLAD800, the cores will be handled very cautiously until finally stored in the
GEOPOLAR cold room at the University of Bremen.
After saving the sediment of the core catcher (approximately 3 cm) and pushing the
core liner out of the core barrel, a clear cap is placed on the “down” end of the core liner with
acetone sealant and duct-tape and a blue cap is affixed to the “top” end of the liner. The core
liner is then split into a 1.5 m “top” section and a smaller “bottom” section. The identifier for
each core section is written on both, top and bottom halves with waterproof black markers
and on opposite sides of the liner. “Up” arrows are also added on the pre-marked lines on the
liner. Additionally, the upper (blue) cap is labelled. The label convention is:
•
•
•
Expedition-Lake/Year-Site/Hole-Core/Device-Section
e.g.: GLAD8-PTA08-1A-1H-1
Global Lake Drilling Expedition 8 – Laguna Potrok Aike, 2008 – Site 1, Hole A – Core 1,
drilled with HPC – Section 1
Abbreviations: e.g. hydraulic piston corer (HPC), core catcher (CC), extended nose (EXN)
After capping and labelling, core sections will be shelved in the on-board refrigeration unit
and ferried to the shore-based laboratory at the end of every shift. Sediment cores will then
be logged with the MSCL. Logging scientists process the data and correlate the holes using
the SPLICER program to produce a composite depth scale. Thus depth offsets between
holes will be determined and communicated to the GLAD800 to guide the drilling of
subsequent holes.
All obtained data and drilling reports will be transferred in daily packages to the Drilling
Information System (DIS) at GFZ Potsdam via a satellite-based internet connection. Internet
access in the field will be provided by INTA.
After completion of shore-based analyses, core sections will be stored in boxes in the
refrigerated container (reefer) which will be transported to Buenos Aires and shipped to
Bremen after the drilling expedition has finished. Upon customs clearance cores will be
stored in dark at +4°C in the GEOPOLAR cold room. First step will be lengthwise splitting of
the cores. One of the split core halves will then be carefully cleaned and photographed
digitally. This archive half will next be used for logging with the GEOTEK MSCL for P-wave
velocity, electrical resistivity, and gamma ray attenuation. Following this procedure, the split
archive half will be imaged and logged with a point sensor for magnetic susceptibility and
with the XRF core scanner at 1 cm resolution. Furthermore, digital image and radiographic
scans will be performed with the split core. Finally, archive halves will be stored in D-tubes
and archived in the GEOPOLAR cold room.
Macroscopic core descriptions will be conducted on the work half. In addition, smear
slides will be analysed microscopically to support sediment characterisation. Next, volumetric
samples for water content and dry bulk density will be taken from the composite sedimentary
sequences of each drill site. In parallel and from the same depths subsampling for
geochemistry, stable isotopes and biological proxies (pollen, diatoms, chironomids, other
algae) will be carried out. After drying and weighing the same sample will be used to analyse
total organic and inorganic carbon, nitrogen and sulphur. Depending upon need, a U-channel
will be taken continuously for rock- and paleomagnetic investigations and for further highresolution XRF scanning. This U-channel will constitute an additional archive.
With the exception of some critical components (which have not yet been determined)
that might deteriorate immediately after the contact with oxygen due to core splitting and
therefore need to be sampled soon after core opening, all other sampling activities will be
deferred and will occur after the financial aspects of their analyses have been assured. Highresolution sampling is anticipated for one composite profile for every drill site. The amount of
material needed per sample depends on the demands of the various analyses and on the
concentration of e.g. certain microfossils. The science party of PASADO will follow sampling
policies and regulations as set up by IODP and adapted by ICDP.
PASADO – Full ICDP Drilling Proposal
24
7. Expected scientific and societal benefits of the proposed work
The major scientific objective is to obtain a long sedimentary record that will provide the first
continuous, quantitative and high-resolution paleoclimate and paleoenvironmental record
from the non-tropical southern mid-latitudes throughout the last glacial-interglacial cycles.
Moreover, we will produce quantitative climate reconstructions based on multiple proxies
(pollen, chironomids, stable isotopes, organic geochemistry) that will be compared with the
output of climate models. Through this proxy-modelling alliance it will be possible to derive a
much more precise understanding of the underlying climate forcing. As an additional
achievement the phasing of wet-dry cycles and other high-frequency climate shifts will be
determined for southern South America. These will then be linked to climatic oscillations of
South America (El Niño) and Antarctica (AAO).
Climate models will be tested with reconstructions of the past that are different from
present day conditions to support and improve climate model estimations of future climate
changes. Thus possible causes and regional patterns of climate anomalies in southern South
America will be analysed by means of climate simulations with a high-resolution regional
climate model for different periods of the past and for the preindustrial period. Regional
simulations will address the role of precipitation and evaporation on lake levels, on moisture
sources and the influence of external climate forcing, such as orbital parameters, solar
variability and past and future impacts of atmospheric greenhouse gas concentrations. Also
relationships between large-scale atmospheric circulation and local climate anomalies for
past and future climates will be considered.
Laguna Potrok Aike is of global geological importance with regard to being the first
large (maar) crater lake studied for its entire sedimentary record. It thus will be possible to
develop and calibrate lithofacies models for lacustrine systems covering several glacial to
interglacial cycles, i.e. from the time of its phreatomagmatic formation. Based on typical
lacustrine sedimentation rates of ~1 mm a-1 the overall temporal resolution will be much
higher compared to other long lake sediment records like Lake Baikal or Lake El’gygytgyn.
This site will become the first maar where a scientific drilling project will attempt to penetrate
lacustrine sediments and to reach the underlying volcaniclastic rocks. This approach will
produce new insights into the early geological history of maar craters and processes that led
to the formation of the modern lake.
After all, investigations within the framework of PASADO will also have societal
benefits. The major economic income in the Province of Santa Cruz is related to extensive
sheep farming. Like during colonisation in the late 19th century this is a rather droughtsensitive economy until today. However, since that time climate started to become drier
resulting in decreased precipitation and increased evaporation. As this climatic process is still
ongoing and was even accelerating during the last decade, climate models will be used to
extrapolate the impact of this change on the economy of the 21st century.
8. Project management
Most PIs are from countries that are already members of the ICDP except for Argentina,
Sweden and Switzerland. Sweden intends to become a member in 2009 (cf. letter of support
in A8), whereas we are still working to convince Argentina to take this step forward (cf. A8).
The situation with Switzerland has been and still is tackled actively by the Swiss PIs (cf. A8).
However, a consensus about a Swiss ICDP membership has not yet been reached.
All PIs have considerable experience with the design and planning of scientific drilling
operations on lakes and with international cooperation. B. Zolitschka and C. Ohlendorf will be
the overall science coordinators of PASADO and act as co-chief scientists in the field. Both
have a long standing record with international lake coring projects. Lake drilling will be
contracted to DOSECC. We have a good working relationship with its director D. Nielson
who developed the GLAD800 drill rig and has a wealth of experience with previous lake
drilling projects.
PASADO – Full ICDP Drilling Proposal
25
The fieldwork at a remote site like Laguna Potrok Aike – the next settlement is Río
Gallegos in a distance of 112 km – needs a very thorough planning. For scientific drilling
operations it is crucial to set up docking facilities and a field camp for housing and living as
well as a field laboratory. The field camp will be organised on the property of the INTA field
station. About ten trailors will be hired from local companies in Río Gallegos for sleeping,
eating and living. Food and water like all the other necessary items will be provided with a
daily shuttle from Río Gallegos. All the logistics, like arrangements for housing, meals, supply
trips, airport shuttle services and communication with locals will be overseen by a local
Argentinean whom we would like to hire as an on-site logistics coordinator. He or she will be
fluent in English as well as in Spanish and also interacts with the technical support group.
For technical support we have ascertained the help of Capt. Moreteau, a nautical pilot
with a license for ocean going ships along the South Atlantic shores and through the Strait of
Magellan. For several years Capt. Moreteau served as a geological consultant for many lakebased scientific operations in Patagonia but also for commercial projects, e.g. harbour
construction at Lago Argentino or building a pipeline to connect offshore oil fields. He will be
the ideal person to take care for road construction to the lake and for construction of the
dock. In addition, he will provide the RV “Lago Cardiel”, a catamaran equipped with powerful
engines to (1) manoeuvre the coring platform and (2) serve as a shuttle boat between shore
and drill rig. Capt. Moreteau with his crew will run the catamaran as well as install and run
communication via vhf and hf radios between the platform, the shore and the field camp.
Moreover, all other technical support, like fuel, oil, lubricants, forklift, backhoe, installation of
land anchor points but also trash disposal will be overseen by him.
H. Corbella, N. Maidana and B. Zolitschka will be contact persons with local political
organisations (government of the Province of Santa Cruz or the City of Río Gallegos) and the
national government, if necessary. They also keep close links with the owners of nearby
estancias and with regional and national radio and TV stations as well as with newspapers.
Fig. 14: On-site management structure for one shift of PASADO.
All information related to regional geology and volcanology will be provided by H.
Corbella and B. Ercolano. The seismic site survey is the responsibility of F. Anselmetti who
works in close collaboration with D. Ariztegui, M. DeBatist, F. Niessen and C. Gebhardt. C.
Ohlendorf will oversee all aspects of core handling and curation. F. Niessen will be in charge
of the GEOTEK MSCL in close collaboration with D. Ariztegui. T. Wonik takes care of
PASADO – Full ICDP Drilling Proposal
26
downhole logging operations. With F. Anselmetti and D. Ariztegui we have two of the PIs of
the very successful Peten-Itza Drilling Project in our team. This will guarantee that previous
experiences will be transferred to PASADO.
For subsequent and detailed analyses of sediment cores at their respective home
laboratories coordination responsibilities are as follows: volcaniclastic rocks (H. De Wall),
tephrochronology (S. Wastegard), lacustrine sedimentology (C. Ohlendorf, B. Zolitschka),
stable isotopes (A. Lücke), pollen (F. Schäbitz), diatoms (N. Maidana), paleomagnetics (L.
Brown), microfacies analyses (P. Francus), paleoclimatic reconstruction (R. Bradley) and
deep biosphere (D. Ariztegui).
The on-site management structure (Fig. 14) follows the successful approach of the
Peten-Itza project. Drilling operations will be carried out in 2 shifts of 12 hours each. On
board of the GLAD800 each shift consists of one drilling supervisor and three drillers from
DOSECC and one co-chief scientist and three scientists of the scientific party. The co-chief
scientist will interact closely with the DOSECC drilling supervisor for on-site decision making.
The three scientists are responsible for core curation, handling of the core catcher sample
and to assist as a driller’s helper. For the field laboratory the two shifts consist of three
scientists: the core logging scientist will operate the MSCL and construct composite sediment
profiles applying the software package SPLICER. The sedimentologist will take care for
organising the cores in the reefer, packing them for shipping and taking samples from the
core catcher for smear slide preparation. The geochemist will squeeze interstitial water from
the core catcher samples which has to be done and measured in the field. Altogether, eight
people from DOSECC and 14 scientists (8 platform-based and 6 laboratory-based) will be
necessary for a smooth operation.
9. International science team
Since 2002, the start of the DEKLIM project SALSA, we have established a strong GermanArgentinean collaboration which since then included more and more European scientists.
With the call for the ICDP Workshop PASADO, held March 15-19, 2006 in Río Gallegos
(Argentina), the list of interested scientists and included disciplines extended tremendously.
Following this call 52 participants from 5 continents and 11 countries (Tabs. 4, 5) were willing
to cooperate and were invited to Patagonia. More scientists expressed their interest but were
unable to attend. All of these and some additional scientists who expressed their interest of
participation in PASADO after the workshop reports appeared in “Scientific Drilling”
(Zolitschka et al., 2006a) and “PAGES News” (Zolitschka et al., 2006c) are listed in Tab. 5.
Altogether, there are currently 58 scientists (36% of them are female) representing a
wide geographical coverage and a balanced expertise: 29 different disciplines shape
PASADO to a vivid inter- and multidisciplinary geoscience approach. This is reflected in the
different topics that were discussed during the PASADO workshop (Zolitschka, 2006;
Zolitschka et al., 2006a, c). All scientists mentioned in Tab. 5 constitute the international
science team of PASADO. This team includes drilling experts as well as scientists with most
of them following clear multidisciplinary and interdisciplinary objectives.
Tab. 4: Countries covered and number of working groups involved per country.
Country
Argentina
Germany
USA
Canada
U.K.
Switzerland
Australia
Belgium
Chile
Poland
Sweden
total
Number of working groups
11
10
6
6
3
2
1
1
1
1
1
43
Number of scientists
17
14
8
7
5
2
1
1
1
1
1
58
PASADO – Full ICDP Drilling Proposal
27
Tab. 5: Alphabetical list of scientists who constitute the international science team of PASADO with
their respective affiliations, countries and scientific disciplines.
First name Last name
Affiliation
Country
Speciality
Flavio
Daniel
Ramiro
Luis
Raymond
Laurie
Hugo
Andrea
Marc
Helga
Bettina
Pierre
Diego
Catalina
Claudia
Torsten
Miguel
Sonja
Julie
Kyeong
Hedy
Scott
Andreas
Isabelle
Peter
Andreas
Nora
Fabiana
Ulrike
Julieta
Christoph
Elizabeth
Beata
J. Daniel
Alexandra
Dennis
Frank
Christian
Gabriel
Marta
Carlos
Reinhard
Eduardo
Jorge
Frank
Guillaume
Juergen
Horacio
Paul
Christel
Sebastian
Stefan
Cathy
Martin
Michael
Thomas
Zhaohui
Bernd
ETH-Zurich
University of Geneva
DIPA-IMHICIHU, Buenos Aires
DIPA-IMHICIHU, Buenos Aires
University of Massachusetts
University of Massachusetts
UNPA & MACN, Buenos Aires
CADIC-CONICET, Ushuaia
Ghent University
University of Wuerzburg
UNPA, Río Gallegos
INRS, Quebec
Universidad de Cordoba
AWI Bremerhaven
CONICET IFAS, Tandil
University of Goettingen
UNPSJB, Puerto Madryn
University of Arkansas
University of Sheffield
University of Arizona
University Crescent
Queen's University
University of Liverpool
INRS, Quebec
University of Regina
Research Centre Juelich
University of Buenos Aires
CEQUA, Punta Arenas
University of Wuerzburg
ILPLA, Instituto de Limnologia
University of Munich (LMU)
UNPA, Río Gallegos
University of Poznan
Puerto Madryn
University College, London
DOSECC
AWI, Bremerhaven
University of Bremen
INTA, Río Gallegos
Universidad de Mar del Plata
Serv. de Hidrografia Naval
Université Laval, Quebec
Universidad de Cordoba
CADIC-CONICET, Ushuaia
University of Cologne
Université du Québec à Rimouski
University College, London
University of Alaska, Fairbanks
Curtin University of Technology
IFM-GEOMAR, Kiel
GKSS Research Centre
University of Stockholm
Montana State University
University of Birmingham
University of Cologne
GGA, Hannover
University of Massachusetts
University of Bremen
Switzerland
Switzerland
Argentina
Argentina
USA
USA
Argentina
Argentina
Belgium
Germany
Argentina
Canada
Argentina
Germany
Argentina
Germany
Argentina
USA
U.K.
USA
Canada
Canada
U.K.
Canada
Canada
Germany
Argentina
Chile
Germany
Argentina
Germany
Argentina
Poland
Argentina
U.K.
USA
Germany
Germany
Argentina
Argentina
Argentina
Canada
Argentina
Argentina
Germany
Canada
U.K.
USA
Australia
Germany
Germany
Sweden
USA
U.K.
Germany
Germany
USA
Germany
seismic stratigraphy
limnogeology
archaeology
archaeology
paleoclimatology
paleomagnetism
volcanology
Quaternary stratigraphy
seismic
volcanology
Quaternary stratigraphy
Microsedimentology
aeolian dust
Seismic stratigraphy
Paleomagnetism
Sedimentology
Volcanology
Diatoms
climate modeling
14
C, 10Be
non-siliceous algae
Paleohydrology
OSL dating
Chironomids
biochemistry
stable isotopes
Diatoms
archaeology
volcanology
chironomids
stable isotopes
remote sensing, GIS
phytoplankton
geological consultants
geochemistry
engineer
physical properties
sedimentology
logistical support
palynology
magnetometry
diatoms
sedimentology
Quaternary stratigraphy
palynology
paleomagnetics
image analysis
sediment modeling
Pb and Sr isotopes
tephrochronology
climate modeling
tephrochronology
charcoal
climate modeling
palynology
downhole logging
organic geochemistry
sedimentology
Anselmetti
Ariztegui
Barberena
Borrero
Bradley
Brown
Corbella
Coronato
DeBatist
DeWall
Ercolano
Francus
Gaiero
Gebhardt
Gogorza
Haberzettl
Haller
Hausmann
Jones
Kim
Kling
Lamoureux
Lang
Larocque
Leavitt
Luecke
Maidana
Martin
Martin
Massaferro
Mayr
Mazzoni
Messyasz
Moreteau
Nederbragt
Nielson
Niessen
Ohlendorf
Oliva
Paez
Paterlini
Pienitz
Piovano
Rabassa
Schaebitz
St-Onge
Thurow
Toniolo
Vallelonga
van den Bogaard
Wagner
Wastegard
Whitlock
Widman
Wille
Wonik
Zhang
Zolitschka
PASADO – Full ICDP Drilling Proposal
28
10. Time table
A realistic time schedule for the PASADO drilling project is necessary and required for all
pre-drilling activities like funding, planning, permitting and shipping but of course also for the
actual field work in Argentina. Delays in this timeline have to be avoided as much as possible
as they usually waste financial resources and unnecessarily question the project
management. However, unpredictable changes in the time schedule often occur and are
related to factors that are difficult to foresee like delayed notification of funding agencies,
especially if five national funding agencies from different countries have to be considered in
addition to ICDP, like in the case of PASADO. Moreover, sudden changes of governmental
or custom regulations or delays in shipping have to be taken into consideration. To minimize
such effects good communication between PIs, funding agencies, DOSECC and all scientific
participants is the key aspect for success.
Tab. 6: Work schedule with milestones for the process of funding (black), a fast track option for drilling
in 2008 (blue) and a slow track option for drilling in 2009 (red).
Years
Months
2007
2008
2009
1 2 3 4 5 6 7 8 9 101112 1 2 3 4 5 6 7 8 9 101112 1 2 3 4 5 6 7 8 9 101112
PASADO proposal submitted
Informal ICDP decision
Supportive proposals submitted*
Formal ICDP decision
Supportive proposals decided
Pre-mobilisation site visits
Equipment leaves to Argentina
Mobilization
Drilling
Demobilization
Equipment returns
Core splitting and scanning
Sampling parties
*to DFG, NSF, NSERC, SNF and VR
We plan the drilling operations to be carried out in the months of January to March
2008 (Tab. 6). This time of the year is selected as the most appropriate with longest daylight
conditions and highest daily temperatures (10-13°C) during southern summer. This “fast
track” option (Tab. 6) will be possible if funding notifications are received in less than half a
year after the informal ICDP decision was made. If this should not be the case, the “slow
track” option (Tab. 6) provides ample time for all the funding to be secured, as this implies
that drilling will be carried out one year later from January to March 2009. In any case, preplanning activities will start immediately after notification by ICDP.
11. References
Allen, J.R.M., U. Brandt, A. Brauer, H. Hubberten, B. Huntley, J. Keller, M. Kraml, J. Mingram, J.F.W. Negendank,
N.R. Nowaczyk, H. Oberhänsli, W.A. Watts, S. Wulf & B. Zolitschka, 1999. Rapid environmental changes
in southern Europe during the last glacial period. Nature 400: 740-743.
Ariztegui, D., P. Bosch and E. Davaud. (2007). ENSO and TAD frequencies during the Little Ice Age (LIA) in
Northern Patagonia. Quaternary International, in press.
Baruth, B., W. Endlicher & P. Hoppe, 1998. Climate and desertification processes in Patagonia. Bamberger
Geographische Schriften 15: 307-320.
PASADO – Full ICDP Drilling Proposal
29
Basile, I., Grousset, F.E., Revel, M., Petit, J.R., Biscaye, P.E. & Barkov, N.I., 1997. Patagonian origin of glacial
dust deposited in East Antarctica (Vostok and Dome C) during glacial stages 2, 4 and 6: Earth and
Planetary Science Letters 146: 573-589.
Begét, J. E., D. M. Hopkins, S.D. Charron (1996). The largest known maars on earth, Seward Peninsula,
Northwest Alaska. Arctic 49: 62-69.
Best, A.I., Gunn, D.E., 1999. Calibration of marine sediment core loggers for quantitative acoustic impedance
studies. Marine Geology, 160: 137-146.
Breitzke, M., 2000. Acoustic and elastic characterization of marine sediments by analysis, modeling, and
inversion of ultrasonic P wave transmission seismograms. Journal of Geophysical Research, 105: 21,41121,430.
Breitzke, M., Spiess, V., 1993. An automated full waveform logging system for high-resolution p-wave profiles in
marine sediments. Marine Geophysical Researches, 15: 297-321.
Breitzke, M., Grobe, H., Kuhn, G., Müller, P. 1996. Full waveform ultrasonic transmission seismograms: A fast
new method for the determination of physical and sedimentological parameters of marine sediment cores.
J. Geophys. Res. 101: 22,123-22,141
Brutseart, W. 1982. Evaporation into the atmosphere, 1 ed. Kluwer Academic Publishers.
Büchel, G., Jacoby, W., Lorenz, V., Zimanowski, B. 1987. Geophysical aspects of the formation of Eifel maars.
Terra cognita, EUG IV, 11.54: 365.
Bücker, C.J., Jarrard, R.D., Niessen, F., Wonik, T. (2001). Statistical Analysis of Wireline Logging Data of Cape
Roberts Borehole CRP-3 (Antarctica), Terra Antartica, 8, 491-506.
Corbella, H., 2002. El campo volcano-tectónico de Pali Aike. In: Haller M.J. (ed.), Geología y Recursos Naturales
de Santa Cruz. Relatorio del XV° Congreso Geológico Argentino. El Calafate. Buenos Aires, pp. 287-303.
Delmonte, B., Petit, J.R., Krinner, G., Maggi, V., Jouzel, J., Udisti, R., 2005. Ice core evidence for secular
variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the
Holocene. Climate Dynamics 24, 641–654.
Diekmann, B., G. Kuhn, V. Rachold, A. Abelmann, U. Brathauer, D. K. Futterer, R. Gersonde and H. Grobe.
(2000). Terrigenous sediment supply in the Scotia Sea (Southern Ocean): response to Late Quaternary ice
dynamics in Patagonia and on the Antarctic Peninsula. Palaeogeography, Palaeoclimatology,
Palaeoecology 162: 357-387.
EPICA community members, 2004. Eight glacial cycles from an Antarctic ice core. Nature 429: 623-628.
Gilli, A., F. Anselmetti, D. Ariztegui, J. Bradbury, K. Kelts, V. Markgraf and J. McKenzie. (2001). Tracking abrupt
climate change in the Southern Hemisphere: a seismic stratigraphic study of Lago Cardiel, Argentina
(49°S). Terra Nova 13: 443-448.
Gilli, A., F. S. Anselmetti, D. Ariztegui, M. Beres, J. A. McKenzie and V. Markgraf. (2005a). Seismic stratigraphy,
buried beach ridges and contourite drifts: the Late Quaternary history of the closed Lago Cardiel basin,
Argentina (49°S). Sedimentology 52: 1-23.
Gilli, A., D. Ariztegui, F. S. Anselmetti, J. A. McKenzie, V. Markgraf, I. Hajdas and R. D. McCulloch. (2005b). MidHolocene strengthening of the Southern Westerlies in South America -- Sedimentological evidences from
Lago Cardiel, Argentina (49°S). Global and Planetary Change 49: 75-93.
Goth, K., Suhr, P., and Schulz, R., 2003. Zwei Forschungsbohrungen in das verdeckte Maar von Baruth
(Sachsen). Z. Angew. Geol., 1/2003: 9-17.
Guilizzoni, P. and F. Oldfield. (1996). Palaeoenvironmental analysis of Italian crater lake and Adriatic sediments.
Memorie dell´Istituto italiano di Idrobiologia 55: 1-357.
González, L. & P. Rial, eds., 2004. Guía geográfica interactiva de Santa Cruz. Río Gallegos, 59 pp.
Haberzettl, T., Fey, M., Lücke, A., Maidana, N., Mayr, C., Ohlendorf, C., Schäbitz, F., Schleser, G.H., Wille, M. &
B. Zolitschka, 2005. Climatically induced lake level changes during the last two millennia as reflected in
sediments of Laguna Potrok Aike, southern Patagonia (Santa Cruz, Argentina). Journal of Paleolimnology
33: 283-302.
Haberzettl, T., M. Wille, M. Fey, S. Janssen, A. Lücke, C. Mayr, C. Ohlendorf, F. Schäbitz, G. Schleser & B.
Zolitschka, 2006. Environmental change and fire history of southern Patagonia (Argentina) during the last
five centuries. Quaternary International 158: 72-82.
Haberzettl, T., Corbella, H., M. Fey, S. Janssen, A. Lücke, C. Mayr, C. Ohlendorf, F. Schäbitz, G.-H. Schleser, E.
Wessel, M. Wille, S. Wulf, B. Zolitschka (2007a). A continuous 16,000 year sediment record from Laguna
Potrok Aike, southern Patagonia (Argentina): Sedimentology, chronology, geochemistry. The Holocene, in
press.
Haberzettl, T., B. Kück, S. Wulf, F. Anselmetti, D. Ariztegui, C. Corbella, M. Fey, S. Janssen, A. Lücke, C. Mayr,
C. Ohlendorf, F. Schäbitz, G. Schleser, M. Wille, B. Zolitschka (2007b): Hydrological variability and
explosive volcanic activity in southeastern Patagonia during Oxygen Isotope Stage 3 and the Holocene
inferred from lake sediments of Laguna Potrok Aike, Argentina. Palaeogeography, Palaeoclimatology,
Palaeoecology, in press.
Hinnov, L.A., (2000) New perspectives on orbitally forced stratigraphy, Annual Review of Earth and Planetary
Sciences, 28, 419-475.
Hodell, D., Anselmetti, F., Brenner, M., Ariztegui, D. and the PISDP Scientific Party (2006): The Lake Peten Itza
Scientific Drilling Project. Scientific Drilling, 3: 25-29.
Horrocks, M., P. C. Augustinus, Y. Deng, P. Shane and S. Andersson. (2005). Holocene environments recorded
in a New Zealand maar crater: Lake Pupuke. New Zealand Journal of Geology and Geophysics 48: 85-94.
PASADO – Full ICDP Drilling Proposal
30
Huvenne, V.A.I., Dorschel, B., Foubert, A., Van Rooij, D., and the IODP Exp. 307 Scientific Party (2006). First
insights in the sedimentary environment at the base of a large cold-water coral bank (Challenger Mound,
NE Atlantic), based on IODP Exp. 307 (May 2005). Geophysical Research Abstracts, 8: 07455.
Jenny, B., Wilhelm, D., Valero-Garce´ s, B.L., 2003. The southern westerlies in Central Chile: Holocene
precipitation estimates based on a water balance model for Laguna Aculeo (331500S). Climate Dynamics
20: 269–280.
Jones, J. and M. Widmann. (2003). Instrument- and tree-ring-based estimates of the Antarctic oscillation. Journal
of Climate 16: 3511-3524.
Kaiser, J., Lamy, F., Arz, H., Hebbeln, D., 2007. Variability of sea-surface temperatures off Chile and the
dynamics of the Patagonian Ice Sheet during the last glacial period based on ODP Site 1233. Quaternary
International, in press.
Kilian, R., H. Biester, J. Müller, K. Eusterhues, G. Casassa and C. Schneider. 2000. Climatic and volcanic
influences on the late Pleistocene and Holocene lacustrine sedimentation in the southernmost Andes
(53°S). Proceedings IX. Congreso Geológico Chileno, Actas, 2: 35-39.
Knorr G., G. Lohmann, 2003. Southern Ocean origin for the resumption of Atlantic thermohaline circulation during
deglaciation. Nature 424: 532-536
Lamy, F., D. Hebbeln, U. Röhl, G. Wefer, 2001. Holocene rainfall variability in southern Chile: a marine record of
latitudinal shifts of the Southern Westerlies. Earth and Planetary Science Letters 185: 369-382.
Lorenz, V. 2003. Maar-Diatrem-Vulkanismus - Ursachen und Folgen. Die Guttauer Vulkangruppe in Ostsachsen
als Beispiel für die komplexen Zusammenhänge. Z. geol. Wiss. 31: 267-312.
Mancini M.V., Paez M.M., Prieto A.R., Stutz, S., Tonello, M., Vilanova, I. (2005). Mid-Holocene climatic variability
reconstruction from pollen records (32°-52°S, Argentina). Qaternary International, 132: 47-59.
Marengo, J. & J. Rogers, 2001. Polar air outbreaks in the Americas: assessments and impacts during modern
and past climates. In Markgraf, V. (Ed.), Interhemispheric climate linkages, San Diego, Academic Press,
31-51.
Markgraf V (1993) Paleoenvironments and paleoclimates in Tierra-del-Fuego and southernmost Patagonia,
South-America. Palaeogeogr, Palaeoclimatol, Palaeoecol 102: 53–68.
Markgraf V, Bradbury J, Schwalb A, Burns S, Stern C, Ariztegui D, Anselmetti AGF, Stine S, Maidana N (2003)
Holocene palaeoclimates of southern Patagonia: limnological and environmental history of Lago Cardiel,
Argentina. Holocene 13: 581–591
Masson, V., Vimeux, F., Jouzel, J., Morgan, V., Delmotte, M., Ciais, P., Hammer, C., Johnsen, S., Lipenkov, V.Y.,
Mosley-Thompson, E., Petit, J.-R., Steig, E.J., Stievenard, M., Vaikmae, R., 2000. Holocene climate
variability in Antarctica based on 11 ice-core isotopic records. Quaternary Research 54, 348–358.
Mayr, C., Lücke, A., Stichler, W., Trimborn, P., Ercolano, B., Oliva, G., Schleser, G.H., Soto, J., Ohlendorf, C.,
Haberzettl, T., Schäbitz, F., Zolitschka, B., Fey, M., Janssen, S. & Wille, M. (2007a): Precipitation origin
18
2
and evaporation of lakes in semi-arid Patagonia (Argentina) inferred from stable isotopes (δ O, δ H).
Journal of Hydrology, in press.
Mayr, C., M. Wille, T. Haberzettl, M. Fey, S. Janssen, A. Lücke, V. Markgraf, C. Ohlendorf, G. Oliva, F. Schäbitz,
G.-H. Schleser, B. Zolitschka (2007b). Holocene variability of the southern hemisphere westerlies in South
America. Quaternary Science Reviews, in press.
Mayr, C., A. Lücke, H. Corbella, M. Fey, T. Haberzettl, S. Janssen, N.I. Maidana, C. Ohlendorf, F., Schäbitz, G.H.
Schleser, M. Wille and B. Zolitschka (in prep.). Isotopic and geochemical variability of sedimentary organic
matter from Laguna Potrok Aike reflect hydrological changes in semi-arid Patagonia during the last 16,000
years. Chemical Geology.
Mazzarini, F. & M. D'Orazio, 2003. Spatial distribution of cones and satellite-detected lineaments in the Pali Aike
Volcanic Field (southernmost Patagonia): insights into the tectonic setting of a Neogene rift system.
Journal of Volcanology & Geothermal Research 125: 291-305.
Mingram, J., J. Allen, C. Bruchmann, J. Liu, X. Luo, J. Negendank, N. Nowaczyk and G. Schettler. (2004a). Maar
and crater lakes of the Long Gang Volcanic Field (NE China) - overview, laminated sediments, and
vegetation history of the last 900 years. Quaternary International 123: 135-147.
Mingram, J., G. Schettler, N. Nowaczyk, X. Luo, H. Lu, J. Liu and J. Negendank. (2004b). The Huguang maar
lake - a high-resolution record of palaeoenvironmental and palaeoclimatic changes over the last 78,000
years from South China. Quaternary International 122: 85-107.
Molinie, A.J., Ogg, J.G. & Ocean Drilling Program Leg 129 Scientific Party (1990): Sedimentation-rate curves and
discontinuities from sliding-window spectral analysis of logs. The Log Analyst, 31: 370-374.
Narcisi, B., J. R. Petit, B. Delmonte, I. Basile-Doelsch and V. Maggi. (2005). Characteristics and sources of tephra
layers in the EPICA-Dome C ice record (East Antarctica): Implications for past atmospheric circulation and
ice core stratigraphic correlations. Earth and Planetary Science Letters 239: 253–265.
Negendank, J.F.W. & B. Zolitschka, 1993. Paleolimnology of European maar lakes. Berlin, Heidelberg, New York,
Springer Verlag, Lecture Notes in Earth Sciences, 49, 513 pp.
Niessen, F. and R.D. Jarrard (1998) Velocity and Porosity of Sediments from the CRP-1 Drillhole, Ross Sea,
Antarctica. Terra Antartica 5: 311-318.
Niessen, F., R.D. Jarrard and C. Bücker (1998) Log-based physical properties of the CRP-1 core, Ross Sea,
Antarctica. Terra Antartica 5: 299-310.
Ohlendorf, C., M. Fey, T. Haberzettl, S. Janssen, A. Lücke, C. Mayr, G. Oliva, F. Schäbitz, G.H. Schleser, M.
Wille and B. Zolitschka (in prep.). A comparison of hydrological balance calculations with instrumental lake
level data for Laguna Potrok Aike (Argentina). Climatic Change.
PASADO – Full ICDP Drilling Proposal
31
Pälike, H., Moore, T., Backman, J., Raffi, I., Lanci, L., Parés, J. M. & Janecek, T. (2005): Integrated stratigraphic
correlation and improved composite depth scales for ODP sites 1218 and 1219. In: Wilson, P.A., Lyle, M.
& Firth, J.V. (eds.). Proceedings of the Ocean Drilling Program, Scientific Results Volume 199: 1-41.
Penman HL (1948) Natural evaporation from open water, bare soil and grass. Proc Roy Soc A 193: 120-145.
Pirrung, M., Fischer, C., Büchel, G., Gaupp, R., Lutz, H., Neuffer, F. -O., 2003. Lithofacies succession of maar
crater deposits in the Eifel area (Germany). Terra Nova 15: 125-132.
Rabassa, J., C.M. Clapperton, 1990. Quaternary glaciations of the southern Andes. Quaternary Science Reviews
9: 153-174.
Schäbitz, F. (1999): Paläoökologische Untersuchungen an geschlossenen Hohlformen in den Trockengebieten
Patagoniens. Bamberger Geogr. Schr., 17: 1-239.
Schulz, R., Buness, H., Gabriel, G., Pucher, R., Rolf, C., Wiederhold, H., and Wonik, T., 2005. Detailed
investigation of preserved maar structures by combined geophysical surveys. Bull. Volcanol. 68: 95-106.
Shulmeister, J., I. Goodwin, J. Renwick, K. Harle, L. Armand, M. S. McGlone, E. Cook, J. Dodson, P. P. Hesse, P.
Mayewski and M. Curran. (2004). The Southern Hemisphere westerlies in the Australasian sector over the
last glacial cycle: a synthesis. Quaternary International 118-119: 25-53.
Thouveny, N., J.-L. d. Beaulieu, E. Bonifay, K. M. Creer, J. Guiot, M. Icole, M. Johnson, S. Jouzel, M. Reille, T.
Williams and D. Williamson. (1994). Climate variations in Europe over the past 140 kyr deduced from rock
magnetism. Nature 371: 503-506.
Turney, C. S. M., A. P. Kershaw, J. J. Lowe, S. v. d. Kaars, R. Johnston, S. Rule, P. Moss, L. Radke, J. Tibby, M.
S. McGlone, J. M. Wilmshurst, M. J. Vandergoes, S. J. Fitzsimons, C. Bryant, S. James, N. P. Branch, J.
Cowley, R. M. Kalin, N. Ogle, G. Jacobsen and L. K. Fifield. (2006). Climatic variability in the southwest
Pacific during the Last Termination (20–10 kyr BP). Quaternary Science Reviews 25: 886-903.
Wagner, S., M. Widmann, J. Jones, T. Haberzettl, A. Lücke, C. Mayr, C. Ohlendorf, F. Schäbitz, B. Zolitschka
(submitted). Transient simulations, empirical reconstructions and forcing mechanisms for the MidHolocene hydrological climate in Southern Patagonia. Climate Dynamics.
Weber, M.E., Niessen, F., Kuhn, G. , Wiedicke M., 1997. Calibration and Application of Marine Sedimentary
Physical Properties using a Multi-Sensor Core Logger. Mar. Geol., 158: 151-172.
Weischet, W. 1996. Regionale Klimatologie. Teil 1: Die neue Welt. - Teubner, Stuttgart, 468 pp.
White, W.B., R. Peterson, 1996. An Antarctic Circumpolar Wave in surface pressure, wind, temperature, and sea
ice extent. Nature 380: 699-702.
Wiederhold, H., 2003. Das verdeckte Maar von Baruth im seismischen Bild. Z. Angew. Geol., 1/2003: 26-35.
Wille, M., N.I. Maidana, F. Schäbitz, M. Fey, T. Haberzettl, S. Janssen, A. Lücke, C. Mayr, C. Ohlendorf, G. H.
Schleser, B. Zolitschka (2007): Vegetation and climate dynamics in southern South America: the
microfossil record of Laguna Potrok Aike, Santa Cruz, Argentina. Rev. Palaeobot. Palynol., submitted.
Wonik, T. (2001): Gamma-ray measurements in the Kirchrode I and II boreholes. – Palaeogeography,
Palaeoclimatology, Palaeoecology, 174: 97-105.
Wonik, T. & Bücker, C. (2000): Möglichkeiten der Bohrlochgeophysik im Institut für Geowissenschaftliche
Gemeinschaftsaufgaben. – DGG-Mitteilungen, Sonderband III: 27-30.
Wonik, T. & Salge, S. (2000): Eine Apparatur für geophysikalische Messungen in kleinkalibrigen Bohrungen bis
1300 m Teufe. - Geol. Jb., E 52: 129-160.
Zolitschka, B., ed. (2006). ICDP Workshop Potrok Aike Lake Sediment Archive and Drilling Project (PASADO) –
Programme, Abstracts, Excursion guide. Terra Nostra 1/2006: 1-88.
Zolitschka, B. & J.F.W. Negendank, 1996. Sedimentology, dating and paleoclimatic interpretation of a 76.3 ka
record from Lago Grande di Monticchio, southern Italy. Quaternary Science Reviews 15: 101-112.
Zolitschka, B., A. Brauer, H. Stockhausen, A. Lang & J.F.W. Negendank, 2000. An annually dated late
Weichselian continental paleoclimate record from the Eifel, Germany. Geology 28: 783-786.
Zolitschka, B., Mingram, J., van der Gaast, S., Jansen, J.H.F. & R. Naumann (2001): Sediment logging
techniques. In: Tracking environmental change using lake sediments: physical and chemical techniques,
W.M. Last & J.P. Smol (eds.); Kluwer Academic Publishers, Dordrecht; 137-153.
Zolitschka, B., Corbella, H., Maidana, N., Ohlendorf, C. (2006a). Investigating Maar Formation and the Climate
History of Southern Argentina – the Potrok Aike Maar Lake Sediment Archive Drilling Project (PASADO)
Scientific Drilling 3: 54-55.
Zolitschka, B., Schäbitz, F., Lücke, A., Clifton, G., Corbella, H., Ercolano, B., Haberzettl, T., Maidana, N., Mayr,
C., Ohlendorf, C., Oliva, G., Paez, M.M., Schleser, G.H., Soto, J., Tiberi, P., Wille, M. (2006b). Crater lakes
of the Pali Aike Volcanic Field as key sites of paleoclimatic and paleoecological reconstructions in
southern Patagonia, Argentina. Journal of South American Earth Sciences 21: 294-309.
Zolitschka, B., Corbella, H., Maidana, N., Ohlendorf, C. (2006c). ICDP workshop PASADO: Deep drilling at
Laguna Potrok Aike, a maar lake in southern Argentina. PAGES News14 (2): 39-40.