1. science
2. geology

PALAEONTOLOGICAL INPUT TO THE SALDANHA ENVIRONMENTAL MANAGEMENT
PLAN
(Desktop Study)
By
John Pether, M.Sc., Pr. Sci. Nat. (Earth Sci.)
Geological and Palaeontological Consultant
P. O. Box 48318, Kommetjie, 7976
Tel./Fax (021) 7833023
Cellphone 083 744 6295
[email protected]
Prepared at the Request of
Aikman Associates Heritage Management
Henry Aikman
0833066768
[email protected]
23 January 2012
CONTENTS
2
INTRODUCTION
1
3
METHODOLOGY
1
4
PALAEONTOLOGICAL HERITAGE MANAGEMENT
3
5
BRIEF HISTORICAL GEOLOGY AND PALAEONTOLOGY
5
6
THE BEDROCK GEOLOGY
6
6.1
GEOLOGICAL HERITAGE
6
6.2
SALDANHA IN GONDWANA
7
7
THE EARLY COASTAL PLAIN
8
7.1
WEATHERING-PROFILE SILCRETE
8
8
THE SANDVELD GROUP
10
9
THE ELANDSFONTYN FORMATION - FLUVIAL/RIVER DEPOSITS
11
10
THE VARSWATER FORMATION – ESTUARINE/PARALIC AND MARINE
13
10.1
MEMBERS OF THE VARSWATER FORMATION AT LANGEBAANWEG
13
10.1.1
Langeenheid Clayey Sand Member (LCSM)
13
10.1.2
Konings Vlei Gravel Member (KGM)
13
10.1.3
Langeberg Quartz Sand Member (LQSM)
15
10.1.4
Muishond Fontein Pelletal Phosphorite Member (MPPM)
15
10.2
OVERVIEW OF THE VARSWATER FORMATION
15
10.2.1
Sea-level history and the Coastal-plain Marine Record
15
10.2.2
Langeenheid Clayey Sand Formation (LCS)
16
10.2.3
Konings Vlei Gravel Formation (KG)
16
10.2.4
The Upper Varswater Formation
17
11
THE MID-MIOCENE SALDANHA FORMATION - MARINE
20
12
THE UPPER VARSWATER FORMATION
21
13
THE UYEKRAAL FORMATION – MARINE
22
14
THE VELDDRIF FORMATION – MARINE AND ESTUARINE
23
14.1
PALAEONTOLOGY OF THE VELDDRIF FORMATION.
25
15
THE AEOLIANITES
26
I
16
THE PROSPECT HILL FORMATION - AEOLIANITE
26
17
THE LANGEBAAN FORMATION - AEOLIANITE
27
18
THE SPRINGFONTYN FORMATION – MAINLY AEOLIAN
29
18.1
BAARD’S QUARRY FLUVIATILE DEPOSITS (BQF)
30
19
THE WITZAND FORMATION – RECENT DUNES
31
20
THE IMPORTANCE OF BOREHOLE CORES
31
21
PROPOSED WIND ENERGY FACILITIES
32
22
APPLICATION FOR A PALAEONTOLOGICAL PERMIT
33
23
REPORTING
33
24
REFERENCES
34
25
GLOSSARY
39
25.1
GEOLOGICAL TIME SCALE TERMS (YOUNGEST TO OLDEST).
41
26
APPENDIX 1 – MONITORING FOR FOSSILS
43
26.1
CONTACTS FOR REPORTING OF FOSSIL FINDS.
43
27
APPENDIX 2 - FOSSIL FIND PROCEDURES
44
27.1
ISOLATED BONE FINDS
44
27.2
BONE CLUSTER FINDS
45
27.3
RESCUE EXCAVATION
45
27.4
MAJOR FINDS
46
27.5
EXPOSURE OF FOSSIL SHELL BEDS
46
LIST OF FIGURES
Figure 1.
Geology of the project area. From Visser & Schoch (1972),
1:125000 Map Sheet 255: 3217D & 3218C (St Helenabaai), 3317B
& 3318A (Saldanhabaai). Legend below in order of youngest to
oldest formations.
2
Figure 2.
As Figure 1, but with shine-through of aerial imagary (Google
Earth).
4
Figure 3.
The Cenozoic Era (65.5 Ma to present) showing global
palaeoclimate proxies, aspects of regional vegetation history and
the context of formations of the Sandveld Group.
9
II
Figure 4.
Bedrock topography showing Oligocene fluvial incision. From
Roberts et al., 2011, Fig 6A. 1=Fossil Park, 2=borehole s22.
10
Figure 5. Elandsfontyn Formation distribution from boreholes. From Erasmus
(2005).
12
Figure 6. Stratigraphic column for the Sandveld Group at Langebaanweg.
From Roberts et al., 2011.
14
Figure 7. Varswater Formation distribution from boreholes. From Erasmus
(2005).
18
Figure 8.
Sea level history for the middle and late Quaternary, showing
glacial/interglacial Marine Isotope Stages. From Siddall et al.,
2007.
23
Figure 9.
Schematic section of Baard’s Quarry deposits.
1974b.
TABLE 1
TABLE 2
From Tankard,
31
10
19
---oooOOOooo---
The author is an independent consultant/researcher and is a recognized
authority in the field of coastal-plain and continental-shelf palaeoenvironments
and is consulted by exploration and mining companies, by the Council for
Geoscience, the Geological Survey of Namibia and by colleagues/students in
academia pursuing coastal-plain/shelf projects.
Expertise
 Shallow marine sedimentology.
 Coastal plain and shelf stratigraphy (interpretation of open-pit
exposures and on/offshore cores).
 Marine macrofossil taxonomy (molluscs, barnacles, brachiopods).
 Marine macrofossil taphonomy.
 Sedimentological and palaeontological field techniques in open-cast
mines (including finding and excavation of vertebrate fossils (bones).
Membership Of Professional Bodies
 South African Council of Natural Scientific Professions. Earth Science.
Reg. No. 400094/95.
 Geological Society of South Africa.
 Palaeontological Society of Southern Africa.
 Southern African Society for Quaternary Research.
 Heritage Western Cape. Member, Permit Committee for Archaeology,
Palaeontology and Meteorites.
 Accredited member, Association of Professional Heritage Practitioners,
Western Cape.
---oooOOOooo---
III
SUMMARY
This document has been prepared at the request of Aikman Associates:
Heritage Management, the consultants whom are coordinating the Heritage
Management inputs to the Saldanha Municipality Environmental Management
Framework (EMF). The need for incorporating “palaeontological sensitivity” in
the EMF is a consequence of the National Heritage Resources Act (NHRA No.
25 of 1999) that protects palaeontological sites and materials, inter alia. Its
purpose is to outline the nature of palaeontological/fossil heritage resources in
the subsurface of the Area of Interest (AoI) for the Saldanha EMF. The fossil
types, their abundance and mode of occurrence is directly related to the
nature of the sediments in which they occur. Thus a description of the fossil
potential or sensitivity of an area is essentially a description of the geology.
The most detailed published map of the area remains that of Visser & Schoch
(1972), at 1:125000 scale, reproduced as Figure 1. The main palaeontological
aspects of the area at the surface, as recorded on the Visser & Schoch (1972)
geological map, were annotated in Google Earth and exported in a
georeferenced form as kml (Keyhole Markup Language) files, to be
incorporated in GIS visualization software.
Annotations and source kml files
Table 2, reproduced below, summarizes the Saldanha coastal-plain
stratigraphy as presented in this report. As discussed in Section 10.2 and
further, a “genetic”, sequence-stratigraphic approach to the Sandveld deposits
produces more formations, from the “promotion” of members or parts of the
Varswater Formation to equal formation status. Table 1 (page 10) represents
the “official” stratigraphy as currently published (e.g. in Roberts et al., 2006)
and graphically depicted in Figure 6. It must be noted that the stratigraphy
presented herein is informal and is the writer’s interpretation, but it is based on
extensive observations elsewhere on the West Coast, as well as in the
IV
Saldanha area. Figure 3 in the text shows where the formations fit in terms of
sea-level and palaeoclimatic history.
In Table 2 the formations of the Sandveld Group are categorized according to
their likelihood of being intersected in the course of bulk earth works. Table 2
also summarizes the palaeontological sensitivity of the formations.
TABLE 2. Formations of the Sandveld Group – sequence stratigraphic
interpretation (see text).
FORMATION
Age and description
Sensitivity
Underlies the surface and affected by bulk earth works
WITZAND
SPRINGFONTYN
VELDDRIF
LANGEBAAN
PROSPECT HILL
Holocene and recently active
dune fields and cordons <~12
ka.
Quaternary to Holocene, mainly
quartzose dune and sandsheet
deposits,
interbedded
palaeosols,
basal
fluvial
deposits <~2 Ma.
Quaternary raised beaches &
estuarine deposits, <~1.2 Ma.
Sea-levels below ~15 m asl.
Late
Pliocene
to
Late
Quaternary aeolianites <~3 Ma.
Late Miocene aeolianite 12-9
Ma?
Mainly archaeological sites.
Fossil bones very sparse,
high signif. Basal BQF-type
deposits locally – high
signif.
Shell fossils common, local
signif. Fossil bones very
sparse, high signif.
Fossil bones mod. common,
local to high signif.
Fossils very sparse – high
signif.
Local exposures only - mainly buried, possibly exposed in deep excavations
UYEKRAAL (2)
VARSWATER
Mid-Pliocene marine deposits
~3 Ma. Sea-level max. ~35 m
asl
Early Pliocene transgressive
marine deposits in embayments
(LQSM and MPPM members).
Later early Pliocene regressive
deposits of wider area. 5-4 Ma.
Sea-level max. ~50 m asl
Shell fossils common, local
signif. Fossil bones very
sparse, high signif.
Fossil
bone
common
locally, high signif. Shells
very sparse, high signif.
No exposure –buried formations likely to only be intercepted in boreholes
Late Miocene marine deposits
KONINGS
VLEI (prev. KGM Member in lower
GRAVEL (1)
Varswater Fm.). 11.5-9.5 Ma?
Sea-level max~30 m asl.?
Mid-Miocene marine deposits
SALDANHA
(predicted presence), 17-14 Ma.
Sea-level max. ~90 m asl.
Mid Miocene early-transgression
LANGEENHEID
estuarine deposits (prev. LCSM
CLAYEY SAND (1) Member in lower Varswater
Fm.). 18-17 Ma.
V
Fossil bones and
sparse, high signif.
shell
Very few fossils recovered,
high signif. if found.
Plant microfossils – high
signif.
ELANDSFONTYN
Oligocene-early Miocene fluvial Plant fossils – high signif.
muds, peats, sands and gravels,
~26-18 Ma.
EXPOSED OLDER ROCKS – PRE-SANDVELD GROUP
SILCRETES
Bedrock/basement
Archaeological Stone Age
resources & geoheritage
Malmesbury shales intruded by Geoheritage/scientific sites
Cape Granites
(no fossils)
Early Cenozoic humid climates
(1) Previously a
(2) Previously subsumed in the UVF: Upper Varswater Fm.
member of the
UVF.
LVF: Lower Varswater Fm.
LVF.
The Bedrock
The bedrock comprises Malmesbury Group shales (Ma) that were intruded at
depth by molten magmas that solidified and crystallized to become the “Cape
Granites” (Figure 1). These bedrock formations are not of palaeontological
interest. Notwithstanding, there is a host of rock types associated with the
intrusion of the Cape Granites into the Malmesbury metasediments and
metavolcanics. These rocks are still being studied and informative outcrops
have been identified and feature as reference and teaching/field trip sites. It is
recommended that the Saldanha EMF include such geoheritage/scientific
outcrop sites, designated by the relevant specialists (e.g. the authors of the
recent synopsis of research on the Cape Granites: Scheepers & Schoch,
2006). This will enhance the geotourism itineraries for the Saldanha area.
The Silcretes
The silcretes (QQ patches on geological map) are the oldest, truly coastalplain rock that can be seen in the Saldanha area. They are also the first
natural earth resource to be exploited, being the favoured material for the
manufacture of Stone Age implements from the start of that technology 1.5
Ma. The silcrete outcrops would have been visited and occupied countless
time during the last 1.5 million years and are surrounded by the evidence of
stone tool making, called “factory sites”, often with ESA, MSA and LSA
industries all present. When visiting silcrete outcrops, one is standing in the
same place in the landscape as the most ancient inhabitants of the Saldanha
area, a million or more years ago!
The Sandveld Group
The succeeding Cenozoic deposits of the Saldanha area coastal plain
comprise the formations of the Sandveld Group (Tables 1 & 2, Figure 3 & 6),
all of which are fossiliferous. The lower formations, (Elandsfontyn, Saldanha,
and most of the Varswater) are not exposed, being buried beneath aeolian
sands of the Prospect Hill, Langebaan and Springfontyn formations and thus
do not feature on the geological map (Figure 1).
The Elandsfontyn Formation (EF)
The deeply weathered bedrock is overlain by the fluvial Elandsfontyn
Formation which attains its greatest thicknesses (~60 m) in palaeovalleys
incised by the ancestral Berg and other rivers. It does not outcrop and thus
VI
does not feature on the geological map. The formation, deposited during
overall rising sea level (during the early to mid-Miocene Figure 3), includes
peaty material which is a record of vegetation change (plant fossils, pollen,
molecular fossils) and which is of international scientific significance.
The Elandsfontyn Formation will only be intercepted during deep borehole
drilling and in deep excavations such as mining pits and pits made as part of
industrial plants. Thus for most developments it is not a consideration.
Langeenheid Clayey Sand Formation (LCS)
The Langeenheid Clayey Sand is interpreted as estuarine sediments
deposited as continued, mid-Miocene rising sea level (Figure 3) inundated the
valleys. Although this unit is restricted to the palaeovalleys, its occurrences
are expected to be a feature of regional extent. For present purposes, the
Langeenheid Clayey Sand is regarded as a separate formation, as tabulated
in Table 2.
The Saldanha Formation (SF)
The Mid-Miocene Climatic Optimum was characterised by a prolonged sealevel highstand, residual basal deposits of which of are preserved elsewhere
on the West Coast between ~40 - ~90 m asl., and in patches beneath
Pliocene deposits at lower elevations. Veneers of this marine package are
also expected to be present in the Saldanha area. However, although
suspected, no unequivocal occurrences have yet been identified, beyond the
speculation that the “Gravel Member” basal to the Upper Varswater Formation
(KG, see below) may incorporate a condensed record of this highstand. No
convincing mid-Miocene marine shell assemblages have been identified yet in
the Saldanha area.
Konings Vlei Gravel Formation (KG)
The KGM is a fossiliferous, polyphase phosphatic gravel, formed by phases of
erosion and re-cementation of phosphatic sandstone. Originally this “Gravel
Member” was thought to be partly or wholly of mid-Miocene age. In this case
it is wholly or partly equivalent to the Saldanha Formation.
The age of the KG is not well constrained and its polyphase origin makes it
problematic.
This assemblage has more in common with Pliocene
assemblages than with those of early to middle Miocene age (pers. obs.). It is
thus feasible that the last events to affect the KGM were during the late
Miocene (Figure 3). Alternatively, it is possible that the last events affecting
the KGM were during the early Pliocene transgression. The KGM will be
regarded as a separate Konings Vlei Gravel Formation (Table 2. A larger
collection of fossils is required in order to resolve the age of the KG.
The Varswater Formation (LQSM & MPPM)
The Langeberg Quartz Sand Member (LQSM) is richly fossiliferous, with a
diversity of bones, shells and microfossils reflecting river floodplain, salt marsh
and tidal-flat environments. It records rising sea-level in the LBW embayment
and is expected to be only in preserved in such embayments. The Muishond
Fontein Pelletal Phosphorite Member (MPPM) reflects further deepening, with
deposition in an expanded estuarine system. A temporary retreat of the sea
VII
allowed local streams to advance across the exposed earlier deposits, cutting
down to the LQSM and concentrating bones in channel lags, as well as
flushing in “new” bones from the surrounding area. The extensive vertebrate
assemblage recovered from the Langebaanweg quarry indicates an early
Pliocene age for the LQSM and MPPM (Hendey, 1981a, 1981b). A review of
the existing data (Roberts et. al., 2011) indicates an age of ~5-5.2 Ma, when
the early Pliocene transgression was nearing its maximum (Figure 3).
Outcrops of phosphatic sands and rock are outlined (blue polygons,
Varswater Fm.kml). The main occurrence is the 3 areas around the LBW
Fossil Park. Fossil bones are noticed in these areas and are probably
reworked from the upper MPPM, or more likely, are occurrences on the
erosion surface on top of the MPPM. The “Varswater” phosphatic sediments
of Soetlandskop between 40-100 m asl. near Stompneusbaai may be of
Miocene age and need investigation. A small fossil shell occurrence near
Saldanha (blue dot) appears to be of early Pliocene age, but material is very
limited. These areas are particularly sensitive and bulk earth works would
need sustained monitoring.
The Uyekraal Formation
Sea level rose again in the middle Pliocene (~3.0 Ma) to a level now ~30 m
asl., and the western part of the Varswater Formation was eroded away,
although some pockets may preserved locally in topographic lows. When sea
level receded again, the Uyekraal Formation “Shelly Sands” were deposited
as the shoreline prograded seawards to form the lower, outer part of the
coastal plain. The Uyekraal Fm. is under a thickness of Langebaan Fm.
aeolianites and calcrete, but is encountered in deeper earth works such as
quarries. At the coast, outcrops with extinct and warm-water fossil shells
occur at Leentjiesklip, Bomgat, Sea Harvest, Elandspunt and the lower quarry
at Diazville (Uyekraal Fm.kml). These are regarded as the outer, eroded
edge of the Uyekraal Formation. Another possible occurrence is the 30 m asl.
fossil oyster bed near Stompneusbaai. It is probable that there are other
occurrences under thin cover on the Vredenburg coast that could be exposed
during normal infrastructural earthworks.
The current state of the aforementioned exposures should be investigated, as
input to a conservation/management plan. Some of these are already “wellknown” geosites that regularly feature in geological/palaeontological field trip
itineraries. Managed geosites will enhance the geotourism potential of the
area.
The Velddrif Formation
The Velddrif Fm. (VD) includes all Quaternary marine deposits below about 15
m asl. that fringe the coast. All the features that are green relate to the
Velddrif Fm. VD QB1.kml outlines larger areas that are closely underlain by
it. VD fossils.kml marks fossil sites specifically noted by Visser & Schoch,
1973) . Along the rocky coast are exposures of the younger, LIG VD (small
light-green spheres, VD Raised Beach 1.kml). South of Jacobsbaai, a
prominent, outer beach ridge is present (VD Beach Terrace 1.kml). VD other
outcrops.kml marks shoreline exposures around Langebaan Lagoon and
Saldanha Bay. The higher, older VD deposits are shown as Raised Beach
VIII
2.kml (small, dark-green spheres) which are prevalent on the Posberg
Peninsula . These deposits are represented by the inner beach ridge south of
Jacobsbaai (VD Beach Terrace 2.kml).
The sensitivity of the younger (outer, 6m) open-coast Velddrif Formation is
moderate and of local significance overall. The exposures along the Berg
River contain exotic warm-water fossil shells and extinct species. These are
just a few sites and are sensitive. The older parts (higher, ~8-15 m asl.) are
poorly exposed and practically unstudied.
Bulk earth works into the Velddrif Formation, that create significant exposure,
must be mitigated by sampling and recording. As for the previous, the state of
the better exposures of the Velddrif Formation should be evaluated, as input to
a CMP. Similarly, some of these are already “well-known” geosites that
regularly feature in field trip itineraries.
The Prospect Hill Formation
The inner aeolianite ridge between Saldanha Bay and Paternoster, previously
in the Langebaan Fm., includes fossil eggshell of the extinct ostrich
Diamantornis wardi dating it to between 12-9 Ma in the Miocene. (Figures 1 &
3, PH, magenta outline, Prospect Hill Fm.kml). Undiagnostic fragmentary
mammal bones have also been found. However, marine microfossil content,
strontium isotope stratigraphy and apparently underlying early Pliocene shell
fauna suggest a younger age.
The Prospect Hill Formation is quarried and expansion of the mining is
proposed. Palaeontological mitigation plans must be included in the mining
EMP. Notably, the fossil discoveries at the Prospect Hill quarry were made
during the carrying out of palaeontological mitigation. Regular mitigation of
mining pit exposures and of development earth works has the potential for
further discoveries that stand to have heritage/scientific benefits in increasing
the knowledge of the Prospect Hill Formation and resolving the conflicting
evidence for its age.
The Langebaan Formation - aeolianite
These calcareous aeolianites are evident in the coastal landscape as the
ridges, low hills and mounds beneath a capping calcrete crust, or “surface
limestone” in old terminology. The considerable extent of the Langebaan
Formation aeolianites (QC, deep yellow) is evident in Figure 1 and attests to
the persistence of strong southerly winds and the availability of calcareous
sand on beaches.
The aeolianites contain further calcretes and leached terra rosa soils at depth,
attesting to a number of periods of reduced rates of sand accumulation,
surface stability and soil formation. There are more marked breaks between
periods of sand accumulation, shown by erosion surfaces or very thick
calcretes formed over a long time. Surface geomorphology also shows
distinct accumulations, as various dune plumes advanced inland from the
coast over previous plumes.
IX
The main “bulk” of aeolianites is not very fossiliferous, but fossil bones from
the Langebaan Formation formation have been a prime source of information
on Quaternary faunas and archaeology (Fossil bone finds.kml). Most of the
fossils in the aeolianites are associated with particular contexts, particularly
buried, stable surfaces (palaeosurfaces) where time has permitted bones to
accumulate. The common fossils include shells of land snails, fossil tortoises,
ostrich incl. egg fragments, sparsely scattered bones etc. Bone and shell
concentrations related to buried Early and Middle Stone Age archaeological
sites may occur in this context in the aeolianite, particularly in its upper part.
“Blowout” erosional palaeosurfaces may carry fossils concentrated by the
removal of sand by the wind. Hollows between dunes (interdune areas) are
the sites of ponding of water seeping from the dunes, leading to the deposits
of springs, marshes and vleis. Being waterholes, such are usually richly
fossiliferous. The lairs of hyaenas, with concentrations of bones of antelopes
and small carnivores, have proved a rich source of “stashed” bones of various
ages.. The calcretes have facilitated overhangs and crevices for use as lairs,
superimposing bone concentrations into an older, partly-cemented aeolianite.
The file Langebaan Fm fossils.kml marks only three sites – these were
evidently sites where fossil land snails were particularly noticeable for Visser &
Schoch (1973). There will be many more such sites. At least one extinct land
snail has been found and is seemingly useful for correlating the older parts of
the Langebaan Formation.
Fossils found in the Langebaan Fm. approximately date the older aeolianites
to late Pliocene, early Quaternary ~1.2 Ma and mid-Quaternary ~600 ka.
Near Geelbek, dating of three sequential calcretes indicated their formation at
~250, ~150 and ~65 ka, during glacial periods. At Kraalbaai the aeolianite is
dated to 117-79 ka. Dating of aeolianites near Cape Town by luminescence
methods shows accumulation during MIS 7 and MIS 5 (interglacials), with
calcrete formation in the intervening glacial (ice age) periods.
The marked fossil bone sites are certainly not all that have been discovered
and more recent finds are under-represented. Sometimes bones have been
exposed on the surface by erosion, usually by wind. Other finds have been
spotted in the sides of excavations. Excavations into the Langebaan Fm.
must be monitored in order to spot fossil bone. Spoil from excavations must
be inspected as far as possible. Large excavations, such as quarrying, must
be periodically inspected and recorded.
The Springfontyn Formation
The Springfontyn Formation is an informal category that accommodates the
mainly non-calcareous, windblown sand sheets and dunes that have covered
parts of the landscape during the Quaternary. Its areal extent is depicted on
the geological map (Figure 1) as surficial units Q2 (older cover) and Q1
(younger cover). The Springfontyn Fm. consists of the sequences beneath
these “coversands”, i.e. SubQ2 and SubQ1.
Unit Q2 is characterized by its surface manifestation as the distinct
“heuweltjiesveld”, the densely dot-patterned landscape of low hillocks that are
termitaria. Its true areal extent is not immediately appreciated as it laps onto
X
bedrock and onto the Langebaan Fm., but for the purposes of geological
mapping (Figure 1) these overlap areas were depicted “transparently” as
outlines. It is also apparent that Q2 underlies large areas now covered by Q1.
The dot-patterned “heuweltjiesveld” is merely the surface-soil characteristic of
Unit Q2. Not much detail is known about Unit Q2 at depth (Sub-Q2).
Pedogenic layers of ferruginous concretions, clayey beds and minor calcretes
occur among sandy-soil beds. Clearly Q2 will differ from place to place
according to the local setting. In this area, in addition to mainly windblown
sands from the south, Sub-Q2 will likely comprise the local
colluvial/hillwash/sheetwash deposits, small slope-stream deposits, alluvium in
the lower valleys and vlei and pan deposits. Middle Quaternary OSL dates of
~150 to ~600 ka from the bases of sampled sections (Chase & Thomas, 2007)
reflect the accumulation of Unit Sub-Q2.
Surface Unit Q1 is a younger “coversand” geological unit and is “white to
slightly-reddish sandy soil” (Visser & Toerien, 1971; Visser & Schoch, 1973).
These are patches of pale sand deposited in geologically-recent times. In
places these sands are undergoing semi-active transport and locally have
been remobilized into active sandsheets and dunes. Chase & Thomas (2007)
have cored Q1 coversands in a regional survey of various settings along the
West Coast and applied optically stimulated luminescence (OSL) dating
techniques to establish the timing of sand accumulation. Their results indicate
several periods of deposition of Q1 during the last 100 ka.
The Springfontyn Formation aeolianites date from at least ~600 ka, if not older
and, in parts, may be of similar ages as parts of the Langebaan Fm., but
derived from less calcareous sources and/or deposited in settings more prone
to subsequent groundwater leaching in water tables. The reworking of older
coastal-plain deposits was likely the major sediment source. It is also possible
that decalcified marine sands have not been recognized as marine in origin,
especially if only encountered in boreholes, and been included in the
Springfontyn Fm.
The Springfontyn Formation has clearly accumulated episodically over a
considerable time span and thus will include palaeosurfaces with bone fossils
and other settings such as vlei deposits with considerable fossil potential.
Earth works should be basically monitored during the Construction Phase
EMPs, with Fossil Find reporting procedures in place and a palaeontologist on
standby.
The fossiliferous, early Quaternary Baard’s Quarry Fluviatile deposits (BQF)
are small-scale watercourse channel cut&fill deposits that are expected to
occupy relict drainage lines, but now, due to covering aeolianites and
coversands, these drainages are not always obvious in the landscape. For
the present, the BQF deposits are regarded as a basal member of the
Springfontyn Formation. The occurrences may be quite shallow (Figure 9)
and may be unexpectedly encountered in earthworks in the Springfontyn
Formation, such as foundations for wind turbines. Few early Quaternary
mammal faunas have been found and further discoveries of BQF-type
deposits would be highly significant.
XI
The Importance of Borehole Cores
Borehole data logs and cores, from drilling for water (“Water Affairs”) and from
specific stratigraphic investigational programs carried out by the Geological
Survey, have been invaluable for the understanding of the subsurface geology
of the Saldanha area. At present the borehole cores obtained during
stratigraphic drilling investigations (Rogers, 1980) are curated by the Council
for Geoscience. The existing borehole cores from the Saldanha area are a
diminishing resource as material gets used up in ongoing analyses.
Geotechnical coring programmes are often preliminary to large industrial
developments. Such a geotechnical core set is a sample of the “natural
archive” of the history of the Saldanha Bay area and the availability of material
of such scientific value is not likely to be repeated in the foreseeable future. It
is recommended that existing and future borehole core sets are donated to the
Council for Geoscience after the geotechnical data requirements are met,
rather than to eventually discard them. The cores will then be available for
archiving as type material, public display and for scientific analysis, particularly
the application of modern isotopic and biogeochemical techniques (molecular
fossils).
Proposed Wind Energy Facilities
Proposed wind energy facilities (WEFs), involving substantial numbers (100s)
of spatially-distributed turbine foundation pits, present an unprecedented
scientific opportunity (should some of the proposed projects proceed). Most of
these excavations, up to 20X20 m in area and 4 m deep, will be in the
Springfontyn and Langebaan formations. In spite of the overall low fossil
potential, there is a good probability that fossils will be exposed at some point
during excavating hundreds of such foundation pits.
The PIAs for these proposed WEFs must recommend that the Construction
Phase EMPs include the monitoring of bulk earth works by on-site personnel
and field inspections by a palaeontologist. The aim of field inspection is to
examine a representative sample of the various deposits exposed in the
turbine excavations, recording context, fossil content and to take samples. As
many as possible should be basically recorded and key pit sections identified
and described and sampled in more detail (e.g. for OSL dating).
Geoheritage and Geotourism
The Saldanha area is well-endowed with palaeontological geoheritage, as well
as other geosites of scientific importance. Although some of these sites
already feature in “field excursion” itineraries, the geotourism potential is not
yet formally exploited and protected. As a desktop study, the data provided is
illustrative and spatially inaccurate; the next step would be to “groundtruth”
potential geosites and ascertain their status. These can be prioritized on the
basis of existing ease of general access. The observations will inform a
management and conservation plan. Educational and explanatory information
must be appropriately provided for designated geoheritage sites.
---oooOOOooo---
XII
2
INTRODUCTION
This document has been prepared at the request of Aikman Associates:
Heritage Management, the consultants whom are coordinating the Heritage
Management inputs to the Saldanha Municipality Environmental Management
Framework (EMF).
The need for incorporating “palaeontological sensitivity” in the EMF is a
consequence of the National Heritage Resources Act (NHRA No. 25 of 1999)
that protects palaeontological sites and materials, inter alia.
Its purpose is to outline the nature of palaeontological/fossil heritage
resources in the subsurface of the Area of Interest (AoI) for the Saldanha
EMF. The fossil types, their abundance and mode of occurrence is directly
related to the nature of the sediments in which they occur, i.e. the depositional
environment or the conditions under which the sediment originally
accumulated. For example, marine deposits usually contain layers (beds) with
abundant fossil seashells. Terrestrial dune deposits commonly contain much
lower densities of land snails and very sparse bones, but concentrations of
these occur locally in specific settings within the dunefield.
This document must therefore be read in conjunction with reference to the
geological map of the area (Figure 1). It summarises the geological history
and nature of the various formations and their fossil content and contexts.
Different fossil contexts are shown as annotations (points, polyline and
polygons), done in Google Earth (Figure 1). Most of these annotations merely
highlight fossil occurrences that are shown on the original geological map, but
a few additional occurrences have been added. The annotations are
illustrative and by no means a comprehensive representation: museum and
Geological Survey records and databases were not reviewed, due to the
limited time available.
3
METHODOLOGY
The most detailed published map of the area remains that of Visser & Schoch
(1972), at 1:125000 scale. The printed map was cut up into its 15’ latitude/15’
longitude tiles and these were scanned to jpg images. Ideally, these then
need rectification to the WGS84 Datum with multiple control point algorithms.
However, to save time, the map tiles were imported (added) into Google Earth
and approximately matched to linear features by eye. Exact matching onto
the Google Earth “background” is not possible by this “eyeballing”, nor do map
tiles exactly match up along their boundaries.
1
Figure 1. Geology of the project area. From Visser & Schoch (1972), 1:125000 Map
Sheet 255: 3217D & 3218C (St Helenabaai), 3317B & 3318A
(Saldanhabaai). Legend below in order of youngest to oldest formations.
Q5: Recent windblown sands and dunes along the beach are mapped as unit Q5. Prominent
dune plumes extend north from sandy beaches. Called the Witzand Formation.
Q1: Another surface unit is the recent soil-unit Q1, white to slightly-reddish sandy soil, which is
mainly a stabilized sand sheet blanketing the underlying geology.
Q2: An older surface unit Q2, shallow sandy soil with heuweltjies (heuweltjiesveld), occurs
inland the coast. Incipient calcretes occur in Q2.
QC: The Langebaan “Limestone” Formation, aeolianite Unit QC, is underlain mainly by
marine deposits of Pliocene age (Varswater & Uyekraal fms).
PH: The Prospect Hill Formation. Part of the Langebaan Fm between Saldanha Bay and
Paternoster has now been separated as this new formation, due to fossil finds indicating that it
is significantly older than the other aeolianites included in the Langebaan Formation. This is
2
shown by the magenta outline in Figure 1.
G1, G2, G3, G4 and G5 are outcrops of various bedrock granites of the Cape Granite Suite.
Ma: Bedrock outcrops of Malmesbury Group metasediments.
Annotations and kml files
The next step was to annotate, in Google Earth, the main palaeontological
aspects of the area, as recorded on the Visser & Schoch (1972) geological
map. The inaccurate geological map overlay was then “faded out” and these
annotations were then viewed in Google Earth only and adjusted to more
feasible positions, e.g. in terms of recorded elevation. Notwithstanding the
level of inaccuracy in the matching, the annotations (for the most part along
the coast), should not be too far off (<200 m). The annotations were then
exported in a georeferenced form as kml (Keyhole Markup Language) files, to
be incorporated in GIS visualization software.
This account of the geology and palaeontology of the Saldanha area is
primarily based on the interpretations in the literature (see below), but differs
in detail on the basis of the author’s own observations both in the area and
from the wider region, particularly the Namaqualand coastal plain.
4
PALAEONTOLOGICAL HERITAGE MANAGEMENT
Notably, palaeontological mitigation differs from archaeological mitigation in
that the latter is usually done before the excavation of bulk earth works,
because the archaeological material is on the surface or shallowly buried.
3
Figure 2. As Figure 1, but with shine-through of aerial imagary (Google Earth).
Although fossils may be exposed on the surface in the vicinity of some of the
sites, this material is usually disturbed and fragmentary. In most cases, such
surficial or shallowly-buried material is in an archaeological context, to be dealt
with by qualified archaeologists. The intent of palaeontological mitigation is to
sample the in situ fossil content and describe the pristine stratigraphic sections
exposed below any human occupation layers.
The rescue of fossils or sampling of fossil content (palaeontological mitigation)
cannot usually be done prior to the commencement of excavations for
infrastructure, prospecting or mining. These palaeontological interventions
thus happen once the EIA process is done, the required approvals have been
obtained and excavation of the trenches/pits is proceeding. The action plans
and protocols for palaeontological mitigation must therefore be included in the
Environmental Management Plan (EMP) for a project.
4
Palaeontological mitigation is a longer-term process and generally does not
usually a priori impede a project. It is possible that during the course of works
an exceptional occurrence could be uncovered that may require a more
extended mitigation programme or perhaps conservation in situ. However, on
the scale of most developments, and prospecting and mining operations, such
low-probability occurrences are also likely to be limited in extent.
Fossils are rare objects, often preserved due to unusual circumstances. This
is particularly applicable to vertebrate fossils (bones), which tend to be
sporadically preserved and have high value w.r.t. palaeoecological and
biostratigraphic (dating) information.
Such fossils are non-renewable
resources. Provided that no subsurface disturbance occurs, the fossils remain
sequestered there.
When excavations are made they furnish the “windows” into the coastal plain
depository that would not otherwise exist and thereby provide access to the
hidden fossils . The impact is positive for palaeontology, provided that efforts
are made to watch out for and rescue the fossils. Fossils and significant
observations will be lost in the absence of management actions to mitigate
such loss this loss of the opportunity to recover them and their contexts when
exposed at a particular site is irreversible. The status of the potential impact
of bulk earth works for palaeontology is not neutral or negligible.
It is not possible to predict the buried fossil content of an area other than in
general terms. The important fossil bone material is sparsely scattered in
most deposits and much depends on spotting this material as it is uncovered
during digging i.e. by monitoring excavations. The very scarcity of fossil
bones in certain contexts, such as in ancient dunes, makes for the added
importance of watching for them. There remains a medium to high risk of
valuable fossils being lost in spite of management actions to mitigate such
loss. Machinery involved in excavation may damage or destroy fossils, or they
may be hidden in “spoil” of excavated material.
5
BRIEF HISTORICAL GEOLOGY AND PALAEONTOLOGY
Early geological and palaeontological work in the Saldanha Bay area
described the calcareous aeolianites, their basal marine beds and
occurrences of phosphatic deposits (Du Toit, 1917; Wybergh, 1919, 1920;
Haughton, 1932a,b). The overall perspective on the surface geology in this
area has been provided by Visser & Schoch (1973) and the accompanying
map. They document valuable observations from the earlier phosphate
exploration phase. Further details of the “Langebaan” or “Coastal Limestones”
are provided by Siesser (1970, 1972).
Mining of the phosphatic deposits led to the discovery of fossil-rich “bone
beds” at Langebaanweg (LBW) which is now an internationally significant
palaeontological site renowned for its prolific, diverse and exceptionally well
5
preserved Mio-Pliocene vertebrate faunas. The exposures provided by mining
and exploratory drilling greatly expanded the knowledge of the stratigraphy
and fossil record of the area (Tankard 1974a,b, 1975a,b,c; Dingle et al., 1979;
Hendey, 1981a,b,c and many earlier publications). Kensley (1972, 1977)
described the taxa and palaeoenvironmental significance of the invertebrates
present in the Gravel and Quartzose Sand members of the Varswater
Formation. Just recently, Roberts et al. (2011) produced a valuable review of
the literature pertaining to the LBW site, citing 176 references. Scientific
papers that refer to the LBW faunas number in the several hundred.
Rogers (1980, 1982, 1983) reviewed and described the wider-scale geology of
the Saldanha coastal plain, viz. gross bedrock topography, sediment
thicknesses and lithostratigraphy, as revealed by a Department of Water
Affairs drilling programme. Useful reviews and summaries that include the
geology and palaeontology around Saldanha are Dingle et al. (1983), Hendey
(1983a,b,c), Hendey and Dingle (1990), Pether et al. (2000) and Roberts et al.
(2006).
6
THE BEDROCK GEOLOGY
The older bedrock of the region consists of Malmesbury Group shales (Ma in
Figure 1) that along the coast have mostly been eroded away to below sea
level. Their origin dates from over 550 Ma (another Ma meaning million years
ago, Mega-annum), when muddy sediments, impure limestones and subsea
basalts were deposited into the Adamastor Ocean that once existed on the
western margin of the early continent (Gresse et al. 2006).
Subsequently, during the assembly of supercontinent Gondwana, continental
drift closed up the Adamastor Ocean and its infill was compressed and welded
onto the older part of southwestern Africa, metamorphosing the muds and
lavas into tightly-folded shales and metavolcanic greenstones. During this
process, between 550 and 515 Ma, the compressed Malmesbury Group was
intruded at depth by molten magmas that solidified and crystallized to become
the “Cape Granites” (Figure 1) that are now exposed as hills in many places,
such as around Darling and Vredenburg.
6.1
GEOLOGICAL HERITAGE
These bedrock formations are not of palaeontological interest.
Notwithstanding, there is a host of rock types associated with the intrusion of
the Cape Granites into the Malmesbury metasediments and metavolcanics.
These rocks are still being studied and informative outcrops have been
identified and feature as reference and teaching/field trip sites.
It is recommended that the Saldanha EMF include such geoheritage/scientific
outcrop sites, designated by the relevant specialists (e.g. the authors of the
recent synopsis of research on the Cape Granites: Scheepers & Schoch,
2006). This will enhance the geotourism itineraries for the Saldanha area.
6
6.2
SALDANHA IN GONDWANA
Mountain ranges had been thrust up along the collision edges of the
assembled parts of the Gondwana supercontinent. The southern Cape was
now some distance from the edge of Gondwana, with the tip of South America
and part of Antarctica between it and the southern Gondwana coast. By ~500
Ma the mountain ranges had eroded down, exposing the “basement” shale
and granite that weathered to form a gently undulating landscape.
Meanwhile, northward drift of Gondwana opened a rifted margin across the tip
of Africa that then subsided. This formed the Agulhas Sea, the depositional
basin in which the ~8 km thickness of Cape Supergroup sediments,
comprising the Table Mountain, Bokkeveld and Witteberg Groups,
accumulated. Overall, the Cape Supergroup is a great wedge of sediment
derived from the north and thickening southwards, from wide fluvial braidplains through shallow marine environments to deeper-water deposits further
out in the Agulhas Sea (Thamm & Johnson 2006). The Saldanha area was
now deeply buried again beneath a few km thickness of sediment.
As Gondwana continued to drift, southern Africa became located at the South
Pole and the future Cape was covered by large ice sheets, with glacial Dwyka
tillite deposits accumulating from ~300 Ma. Subsequently, between 280 and
230 Ma, the Agulhas Sea underwent compression from the south, squeezing
the Cape Supergroup upwards in a series of stacked thrusts and folds to form
the Cape Fold Belt mountains, while to the north the crust sagged downwards
to form the Karoo Basin. The Saldanha area was now submerged in the
Karoo Sea.
The Karoo Basin subsequently filled up with ~12 km of marine, deltaic, fluvial
and, finally, aeolian deposits. The basin was then covered by a vast
outpouring of ‘Continental Flood Basalt’ lavas, up to 5 km thick and covering
two million square km. Its remnants are seen today as the Drakensberg and
Lebombo mountain ranges and the accompanying igneous ‘plumbing’ of
numerous dolerite dykes and sills in the Karoo Supergroup. This immense
eruption of lava and gas, over just a few million years around 183 Ma, was the
surface manifestation of the inexorable subcrustal flows that portended the
break-up of Gondwana.
By ~155 Ma, rifting was under way and the continental margins of southern
Africa began forming. By ~130 Ma, new oceanic crust was being generated
between the land masses and the separation of Africa from South America
was under way, so that by ~100 Ma southern Africa was surrounded by ocean.
By 65 Ma, at the end of the Cretaceous, enormous volumes of sediment had
been eroded from the subcontinent, and the basic topographic elements of the
Great Escarpment and interior and coastal ‘African’ surfaces of southern
Africa had taken shape (Partridge & Maud, 1987).
The “Gondwana” sediments of the Cape and Karoo Supergroups have
eroded off the Saldanha area coastal plain, re-exposing again the
deeply-buried “basement” of Malmesbury shales and Cape Granites.
basement was now bearing the imprint of rifting, i.e. the bedrock had
7
been
once
This
been
faulted into high and low areas, called horsts and grabens, and the latter lowlying graben blocks strongly influenced the developing coastline and river
courses.
7
THE EARLY COASTAL PLAIN
During the late Cretaceous the newly-formed coastal plain was submerged
(transgressed) during periods of high sea-level and during the warm periods of
the Eocene Epoch the coastal plain was also submerged several times. Most
of these previously extensive marine deposits of this long ~60 million-year
timespan have been eroded from the coastal plain and occurrences are not
known in the Saldanha area. The erosion was more pronounced during times
of low sea levels, when rejuvenated river systems cut down to the lowered
base levels.
During late Eocene and Oligocene times, the Earth underwent major cooling
and the Antarctic ice cap grew substantially, lowering sea level (Figure 3).
The river erosion caused by this Oligocene regression is considered
responsible for the main features of the buried bedrock topography as now
preserved beneath the coastal plain, i.e. buried river valleys or
palaeochannels, such as those under the Saldanha area (Figure 4). The
ancestral Berg River is thought to have occupied the Geelbek palaeovalley
during the Oligocene regression (Figure 4). Subsequently, the palaeovalleys
were infilled with river sediments during the early Miocene. The palaeo-Berg
then shifted northwards, meandering over this alluvium, to a later Miocene and
Pliocene entering Saldanha Bay.
7.1
WEATHERING-PROFILE SILCRETE
The late Cretaceous and early Cenozoic palaeoclimates were mainly humid
and long-lived land surfaces were deeply weathered, resulting in leached,
pallid (kaolinitic) soil profiles and hard, siliceous layers that formed in the
weathering profile, called silcrete (old name is surface quartzite). These
silcretes are the only rocks in the Saldanha area that survive from these times
and occur as patches of “capping rock” on the weathered bedrock, both shale
and granites. The occurrences are usually on higher spots of the terrain, as
the silcrete has protected the underlying profile from erosion. Originally the
silcrete formed within drainages, i.e. low areas, but with lowering of the
surrounding landscape they are now proud (topographic inversion).
In the Saldanha area the patches of silcrete, labelled QQ, are found on the
granites of the Vredenburg Peninsula and on the Malmesbury bedrock in the
eastern part of the AoI. The silcretes are thus the oldest, truly coastal-plain
rock that can be seen in the Saldanha area. They are also the first natural
earth resource to be exploited, being the favoured material for the
manufacture of Stone Age implements from the start of that technology 1.5
Ma. This is due to the micro-crystalline, “glassy” quartz composition of
8
silcrete, generally uniform in texture and capable of being shaped by knocking
off flakes to form sharp edges.
Figure 3.
The Cenozoic Era (65.5 Ma to present) showing global palaeoclimate
proxies, aspects of regional vegetation history and the context of
formations of the Sandveld Group.
Cyan curve - history of deep-ocean temperatures, adapted from Zachos et al. (2008).
Blue curve is an estimate of global ice volumes, adapted from Lear et al. (2000).
Global ice volumes roughly indicate sea-level history caused by the subtraction from
the sea of water as land-ice. The expansion of Fynbos and Karoo floras is adapted
from Verboom et al. (2009). Other annotations are also mentioned in the text.
Formations: EF-Elandsfontyn Fm. LCS-Langeenheid Clayey Sand (LVF). SFSaldanha Fm. (Miocene marine deposits cf. Kleinzee Fm). KG-Konings Vlei Gravel
(LVF). PH-Prospect Hill Fm. UVF-Upper Varswater Fm. US-Uyekraal Fm. LBLangebaan Fm. VD-Velddrif Fm. SP-Springfontyn Fm. LVF- Lower Varswater Fm.
9
Figure 4. Bedrock topography showing Oligocene fluvial incision. From Roberts et
al., 2011, Fig 6A. 1=Fossil Park, 2=borehole s22.
As the prime technological “feedstock”, the silcrete outcrops would have been
visited and occupied countless time during the last 1.5 million years and are
surrounded by the evidence of stone tool making, called “factory sites”, often
with ESA, MSA and LSA industries all present. When visiting silcrete
outcrops, one is standing in the same place in the landscape as the most
ancient inhabitants of the Saldanha area, a million or more years ago!
8
THE SANDVELD GROUP
The coastal deposits around Saldanha are subsumed in the Sandveld Group,
which is comprised of the following formations:
TABLE 1. Formations of the Sandveld Group – current lithostratigraphy.
SANDVELD GROUP
Age and lithology
Witzand Formation
Holocene and recently active dune fields and cordons
Springfontyn Formation
Quaternary to Holocene calcareous sandstone (aeolianite) with
interbedded palaeosols
Velddrif Formation
Quaternary estuarine coquina, calcarenite, sand and conglomerate
Langebaan Formation
Late Pliocene to Late Quaternary aeolianites
Prospect Hill Formation
Late Miocene aeolianite
Varswater Formation
Mio-Pliocene littoral and shallow marine sandstone, coquina and
conglomerate
Elandsfontyn Formation
Early- mid-Miocene fluvial muds, peats, sands and gravels
Adapted from Roberts et al., 2006.
10
Table 1 represents the “official” stratigraphy as currently published (e.g. in
Roberts et al., 2006) and graphically depicted in Figure 6. However, as
discussed in Section 10.2 and further, a “genetic”, sequence-stratigraphic
approach to the Sandveld deposits produces more formations from the
“promotion” of members of the Varswater Formation to formation status
(compare Tables 1 & 2). It must be noted that the stratigraphy presented
herein is informal and is the writer’s interpretation, but it is based on extensive
observations elsewhere on the West Coast, as well as in the Saldanha area.
As listed in Table 2 the formations of the Sandveld Group may be categorized
according to their likelihood of being intersected in the course of bulk earth
works:



Underlies the surface and will be affected by bulk earth works
Local exposures only - mainly buried, possibly exposed in deep excavations
No exposure –buried formations likely to only be intercepted in boreholes
Table 2 also summarizes the palaeontological sensitivity of the formations.
9
THE ELANDSFONTYN FORMATION - FLUVIAL/RIVER DEPOSITS
Over much of the coastal plain of the southwestern Cape, the deeply
weathered bedrock is overlain by the fluvial Elandsfontyn Formation (Rogers,
1980, 1982), which attains its greatest thicknesses (~60 m) in bedrock
topographic lows and is never exposed. In the Saldanha area it is
distinguished from overlying paralic and marine sediments by the angularity of
its sands and the lack of carbonate and phosphate. The Elandsfontyn
Formation sediments are considered to be derived from the deeply weathered,
coastal-plain bedrock as “newly released, first cycle” material (Rogers, 1980,
1982, 1983).
From the late Oligocene at ~27 Ma, slow warming recommenced, the ice cap
melted over time and climates of mid-higher latitudes ameliorated, in a long
trend with several glacial relapses, towards a Mid-Miocene Climatic Optimum
at 17–15 Ma (Figure 3). As sea-level rose again the incised coastal valleys
became backed up with sediments (Figures 4 & 5). A number of finingupward cycles terminating in muddy and peaty layers are usually present.
The depositional environments are interpreted to be those of meandering
rivers under humid climatic conditions (Rogers, 1980, 1982).
Fossil pollen in Elandsfontyn Formation sediments provides evidence of mixed
podocarp-angiosperm forest and lowland palms in older parts, while the
younger, upper parts of these composite deposits have taxa characteristic of
the Cape Floristic Region (Figure 3) (Coetzee et al. 1983). These younger
sequences relate to the climatic deterioration of the later Miocene as the
Antarctic ice sheet expanded, regional circulation stepped towards its modern
configuration and the ancient forests gave way to reduced, increasingly
11
seasonal rainfall and dry-season fires. Correspondingly, grasses and shrubs
diversified in the changing landscape (Cowling et al. 2009), in tandem with
adaptations and extinctions in the Cape insect and mammal faunas.
Figure 5. Elandsfontyn Formation distribution from boreholes. From Erasmus (2005).
In the Langebaanweg area (S1 borehole), the pollen from peats of the
Elandsfontyn Fm. suggested an early to middle Miocene age (Coetzee and
Rogers, 1982). The characteristics of the Elandsfontyn Fm. in the wider
region are detailed in Cole & Roberts (1996) and Cole & Roberts (2000).
Notwithstanding, the existing fossil plant data have not provided more tightlyconstrained age estimates for the various occurrences.
The Elandsfontyn Formation will only be intercepted during deep borehole
drilling and in deep excavations such as mining pits and pits made as part of
industrial plants. Thus for most developments it is not a consideration.
12
THE VARSWATER FORMATION – ESTUARINE/PARALIC AND MARINE
10
Phosphatic and bone-bearing estuarine and marine deposits of the Varswater
Formation (Tankard, 1974b) overlie the Elandsfontyn Formation. For the most
part, the Varswater Fm. is concealed beneath the Langebaan and
Springfontyn formation’ aeolianites, but its distribution is known from
boreholes. Its proximity to the surface is betrayed by phosphatic rocks and
nodules.
The type area of the Varswater Fm. is the E Quarry at the SAMANCOR
phosphate mine, aka. the LBW quarry or the West Coast Fossil
Park.(www.fossilpark.org). There the topographic low of the valley formed a
broad embayment when inundated by rising sea level. Such topographic lows
were able to accommodate a thicker sequence of deposits.
Thinner
sequences were deposited in the surrounding, higher areas, but these were
more prone to subsequent removal by erosion.
As currently defined (Roberts et. al., 2011) the Varswater Formation consists
of smaller units/formations currently with the status of “members”. The lower
two members are of different Miocene ages and comprise the Lower
Varswater Fm (LVF).
The Upper Varswater Fm. (UVF) is the main
fossiliferous deposit of early Pliocene age (Figures 3 & 6).
10.1
MEMBERS OF THE VARSWATER FORMATION AT LANGEBAANWEG
10.1.1
Langeenheid Clayey Sand Member (LCSM)
At Langebaanweg, the carbonaceous silts and clays of the Elandsfontyn
Formation pass upwards into clayey, greyish-green fine sand with reddish
mottles. Interpreted as estuarine sediments deposited as the mid Miocene
rising sea level (Figure 3) flooded into the valley embayments, this unit is only
locally present and varies from 1 to 11.5 m in thickness (Roberts et al., 2011).
Macrofossils have not been found in it, but observations are limited as it is
known mainly from boreholes and is below quarry footwall at Langebaanweg.
Plant microfossils (phytoliths) are present (Rossouw et. al., 2009). The
reddish mottling of the LCSM suggests that it was later weathered during
exposure on land (subaerial palaeoweathering).
10.1.2
Konings Vlei Gravel Member (KGM)
The LCSM was eroded and closely overlying the erosion surface is the marine
“Gravel Member”, a fossiliferous, polyphase phosphatic gravel, formed by
phases of erosion and re-cementation of phosphatic sandstone. In the
Langebaanweg embayment, the KGM unit thickens from ~2 m in the north to
~8 m in the southwest. Where thickly preserved, sandy sediments with
pockets of fossil warm-water marine molluscs, scattered shark teeth and rare
mammalian bones occur. A shallow marine origin is envisaged for the KGM,
with contemporaneous cementing of phosphatic sand being episodically
disrupted by high-energy storm events, generating intraformational gravels
that were later re-cemented.
13
It has been suggested that the KGM is a condensed record of Middle to Late
Miocene transgression and regression (Hendey, 1981a,b) and that the initial
phase of the “Gravel Member” was deposited during the mid-Miocene sealevel high (Figure 3, SF). Tankard (1975c) named the “Gravel Member” the
Saldanha Formation, considered to be of mid-Miocene age (see below).
However, the presence of the three-toed horse Hippotherium cf. primigenium
indicates an age younger than ~10.7 Ma (Geraads et al., 2002). For instance,
it may correlate with high sea level between 11.5-9.5 Ma (Figure 3).
Figure 6.
Stratigraphic column for the Sandveld Group at Langebaanweg.
Roberts et al., 2011.
14
From
10.1.3
Langeberg Quartz Sand Member (LQSM)
During latest Miocene-earlyPliocene warming (Figure 3), rising sea level reentered the LBW embayment. The LQSM is a shallow estuarine deposit
consisting of river floodplain, salt marsh and tidal-flat environments, laid down
when the shoreline of the rising sea-level was just west of E Quarry and a
beach-barrier or spit had formed across the estuary mouth. Composed of pale
quartz sands, muddy silts and peats, it is only up to ~2 m thick. It is richly
fossiliferous, with a diversity of bones, shells and microfossils reflecting the
various environments. Fossil plant material (pollen and phytoliths) from peat
in the LQSM has some similarities with that in the mid-Miocene Elandsfontyn
Formation, but with more emphasis on summer-dry adapted fynbos (Scott,
1995; Rossouw et. al., 2009) (Figure 3).
10.1.4
Muishond Fontein Pelletal Phosphorite Member (MPPM)
The MPPM is the main phosphatic-sand bearing unit of the Varswater
Formation. Its formation reflects the increasing inundation of the area by
rising sea level. Deposition took place in an expanded estuarine system;
seals and fishes reflect the aquatic estuarine habitat. The MPPM becomes
more open-marine in the upper part, with marine microfossils, fish teeth and
shell fragments, but very few bones, and evidently reflects deposition in a
deepening embayment.
The fossil bone beds occur in channels incised into the lower MPPM and
LQSM and in the lags of stacked channel fills embedded in the MPPM
estuarine deposits (Figure 6). The channels originated when sea-level
temporarily receded during a regressive episode in the overall transgressive
regime. The estuarine deposits were exposed and a local stream system
incised into them, concentrating bones from the LQSM and delivering “new”
bones from the surrounding catchment, for a brief period until sea-level rose
again (Roberts et. al., 2011).
The extensive vertebrate assemblage recovered from the Langebaanweg
quarry indicates an early Pliocene age for the LQSM and MPPM (Hendey,
1981a, 1981b). A review of the existing data (Roberts et. al., 2011) indicates
an age of ~5-5.2 Ma, when the early Pliocene transgression was nearing its
maximum (Figure 3).
10.2
OVERVIEW OF THE VARSWATER FORMATION
10.2.1
Sea-level history and the Coastal-plain Marine Record
As seen in Figure 3, the LCSM, KGM and UVF (LQSM & MPPM) have
distinctly different ages. The current stratigraphic nomenclature is “work in
progress”, historically based on lithology (sediment composition and texture)
and not explicitly based on sea level history.
The latter approach
(sequence/dynamic stratigraphy) is appropriate to coastal-plain stratigraphy,
which has been formed by repeated cycles of marine transgressions and
regressions. In this approach, a marine formation includes that package of
deposits that relates to a particular sea-level cycle of rising and falling sea
15
level. The LCSM, KGM and UVF members of the Varswater Formation can
thus be treated (informally for now) as separate formations.
On the Namaqualand coast the deposits of the three major sea-level cycles
are preserved on the coastal plain. These three formations each have an
internally-consistent geometry of palaeoenvironments, are separated by
erosional contacts and sometimes by intervening terrestrial deposits, and are
sufficiently separated in time and by palaeoceanographic changes that each
has a distinct, distinguishing fossil content. The fossil evidence indicates that
the ages of these three large formations are mid-Miocene (~16 Ma), early
Pliocene (5-4 Ma) and mid-Pliocene (~3 Ma). Each formation extends
seawards from its highest palaeoshoreline (transgressive maximum). These
are, from oldest to youngest, at ~90, ~50 and ~30 m asl.
The position of these marine “90, 50 and 30 m Packages” or formations on the
sea-level curve is shown in Figure 3. The ~90 m, ~50 m and ~ 30 m asl.
palaeoshorelines do not reflect the actual sea-level (relative to the present
level) that was attained during each transgression. Instead, uplift of the
subcontinent edges has raised the palaeoshorelines to their present
elevations. Notably, each formation has a phosphatic component. The
implications of sea-level history for the coastal plain record in the Saldanha
area is further enlarged below.
10.2.2
Langeenheid Clayey Sand Formation (LCS)
In terms of sea-level history, the LCSM can be regarded as the upper, terminal
member of the Elandsfontyn Formation (rather than the lowest member of the
Varswater Formation), deposited when rising sea-level led to estuarine
environments conformably succeeding the river deposits in the palaeovalleys
(Figure 3). On the other hand, these beds are distinct from the underlying
fluvial and marshy deposits of the Elandsfontyn Fm. They form a significant
part of the stratigraphy, averaging 10 m in thickness. Although this unit is
restricted to the palaeovalleys, its occurrences are expected to be a feature of
regional extent. For present purposes, the Langeenheid Clayey Sand is
regarded as a separate formation, as tabulated in Table 2.
10.2.3
Konings Vlei Gravel Formation (KG)
Sea level continued rising due to global warming, culminating in the MidMiocene Climatic Optimum (Figure 3). The passage of the shoreface over the
area produced an eroded surface on the LCS and ultimately the area was
submerged at shelf depths of ~70-80 m. Muddy shelf deposits would have
accumulated, but when sea level fell again (Figure 3) these would have been
largely eroded away and replaced by shallow-marine, inner-shelf and
shoreface deposits. The KGM evidently formed under such circumstances,
with cementing phosphatic sand being episodically disrupted by storm events,
generating intraformational gravels that were later re-cemented.
The age of the KGM is not well constrained and its polyphase origin makes it
problematic. The shell fossils postdate the earliest, worn, hard phosphatic
sandstone, but the two samples came from different phases of reworking,
early and late. Only a very small assemblage of fossil shells has been
16
obtained. This assemblage has more in common with Pliocene assemblages
than with those of early to middle Miocene age (pers. obs.). It is thus feasible
that the last events to affect the KGM were during the late Miocene (Figure 3).
Alternatively, it is possible that the last events affecting the KGM were during
the early Pliocene transgression, in the form of an initial low-energy marine
incursion into the LBW embayment. The Hippotherium fossil teeth could have
been reworked from the older, late Miocene deposits (Hendey & Dingle,
1990).
The KGM will be regarded as a separate Konings Vlei Gravel Formation
(Table 2). The Varswater Formation will then only be comprised of the UVF.
The KG Fm. may be mainly of mid-Miocene age and thus equivalent to the
Saldanha Formation (see below). Alternatively, it is mainly of late Miocene
age, as reflected in Figure 3. Its top may have been reworked by the early
Pliocene marine incursion. A larger collection of fossils is required in order to
resolve its age.
10.2.4
The Upper Varswater Formation
A further complication arises with respect to the definition of the Varswater
Formation in the wider region. In general, the occurrence of phosphatic sands
in boreholes is correlated with the MPPM. Such “Varswater Fm.” sands have
been identified up to ~90 m asl. in boreholes, as well as extending down to
and beyond the current shoreline of Saldanha Bay. Such a wide-ranging
distribution is suspicious when viewed against the sea-level record and
associated stratigraphy defined further north on the Namaqualand coast.
The subsurface distribution of the “Varswater Formation” as depicted in Figure
7, primarily relates to the occurrence of phosphatic sands and not formations
of different ages formed during separate sea-level cycles. As phosphatic
sands are recorded up to ~90 m asl. in the Elandsfontyn borehole S22 south
of Langebaanweg (Rogers, 1980), the Upper Varswater Formation has been
associated with a transgression to 90 m asl. (Roberts et al., 2012).
An early Pliocene “Varswater” transgression to 90 m asl. is spurious and is
also negated by the deep-sea oxygen-isotope record which is incompatible
with major Pliocene deglaciation of Antarctica and very high sea levels (Hodell
& Venz, 1992).
The Upper Varswater LQSM and MPPM were deposited in a deepening
environment during sea level rise/transgression into an embayment, during the
earliest Pliocene, 5.2-5 Ma (Figure 3). A large formation of approximately the
same age is present on the Namaqualand coastal plain, over-riding the eroded
edge of the mid-Miocene marine deposits.
Fossil evidence such as
“Langebaanian” vertebrates shows that these marine deposits are basically
the same age as the Upper Varswater Formation (Pether et. al., 2000).
Notably, these early Pliocene marine deposits are found below ~50 m asl.,
indicating a transgressive maximum not much higher. Initially called the “50 m
Package” (Pether et. al., 2000), this formation is now informally called the
“Avontuur Formation”. At LBW the MPPM attains a maximum elevation of ~50
m asl.
17
An important difference is that, while the UVF was deposited during sea level
rise into a deep embayment , the Avontuur Formation was deposited when
sea level later receded from ~50 m asl., somewhat later. In contrast with the
record of the Saldanha palaeo-coast, due to the steeper gradients along the
open-coast, transgression deposits were largely destroyed as sea level later
regressed.
Phosphatic sands in the subsurface that extent up to the present coast have
also been included in the Varswater Formation (Figure 7). The flat plain
extending west from LBW is underlain by marine deposits that are spatially
consistent with being equivalent to mid-Pliocene 30 m Package deposits, seen
in Namaqualand diamond mines as a substantial, prograded marine formation
built out seawards from a sea-level maximum of 30-35 m asl. By historical
precedent, these marine beds may be called the Uyekraal Formation (see
below) and separated from the Varswater Formation.
Figure 7. Varswater Formation distribution from boreholes. From Erasmus (2005).
18
TABLE 2. Formations of the Sandveld Group – sequence stratigraphic
interpretation (see text).
Age and description
FORMATION
Sensitivity
Underlies the surface and affected by bulk earth works
Holocene and recently active dune
fields and cordons <~12 ka.
WITZAND
LANGEBAAN
Quaternary to Holocene, mainly
quartzose dune and sandsheet
deposits, interbedded palaeosols,
basal fluvial deposits <~2 Ma.
Quaternary raised beaches &
estuarine deposits, <~1.2 Ma. Sealevels below ~15 m asl.
Late Pliocene to Late Quaternary
aeolianites <~3 Ma.
PROSPECT HILL
Late Miocene aeolianite 12-9 Ma?
SPRINGFONTYN
VELDDRIF
Mainly archaeological sites.
Fossil bones very sparse, high
signif.
Basal BQF-type
deposits locally – high signif.
Shell fossils common, local
signif.
Fossil bones very
sparse, high signif.
Fossil bones mod. common,
local to high signif.
Fossils very sparse – high
signif.
Local exposures only - mainly buried, possibly exposed in deep excavations
UYEKRAAL (2)
Mid-Pliocene marine deposits ~3
Ma. Sea-level max. ~35 m asl
VARSWATER
Early
Pliocene
transgressive
marine deposits in embayments
(LQSM and MPPM members).
Later early Pliocene regressive
deposits of wider area. 5-4 Ma.
Sea-level max. ~50 m asl
Shell fossils common, local
signif.
Fossil bones very
sparse, high signif.
Fossil bone common locally,
high signif. Shells very sparse,
high signif.
No exposure –buried formations likely to only be intercepted in boreholes
KONINGS
GRAVEL (1)
VLEI
SALDANHA
LANGEENHEID
CLAYEY SAND (1)
ELANDSFONTYN
Late Miocene marine deposits
(prev. KGM Member in lower
Varswater Fm.).
11.5-9.5 Ma?
Sea-level max~30 m asl.?
Mid-Miocene
marine
deposits
(predicted presence), 17-14 Ma.
Sea-level max. ~90 m asl.
Mid Miocene early-transgression
estuarine deposits (prev. LCSM
Member in lower Varswater Fm.).
18-17 Ma.
Oligocene-early Miocene fluvial
muds, peats, sands and gravels,
~26-18 Ma.
Fossil bones and shell sparse,
high signif.
Very few fossils recovered,
high signif. if found.
Plant microfossils – high signif.
Plant fossils – high signif.
EXPOSED OLDER ROCKS – PRE-SANDVELD GROUP
SILCRETES
Early Cenozoic humid climates
Archaeological Stone
resources & geoheritage
Bedrock/basement
Malmesbury shales intruded by
Cape Granites
Geoheritage/scientific sites (no
fossils)
(1) Previously a
member of the LVF.
(2) Previously subsumed in the
UVF.
UVF: Upper Varswater Fm.
LVF: Lower Varswater Fm.
19
Age
11
THE MID-MIOCENE SALDANHA FORMATION - MARINE
Perceived mid-Miocene marine deposits have been named the “Saldanha
Formation” by Tankard (1975c). This name has historical precedence, but the
pinning down of this formation to a specific section has proved elusive. The
stratotype, at the “Bomgat” on the Hoedjiespunt peninsula, is of mid-Pliocene
age. The reference stratotype in the Langebaanweg mine is evidently the KG,
where it manifests as a polyphase conglomerate composed of clasts of
phosphatic sandstone. The named occurrence at Ysterplaat is of Pliocene
age, based on fossil shells found subsequently by the writer.. Only the
occurrences on the Namaqualand coast referred to by Tankard (1975c) can
be confirmed as mid-Miocene of age (pers. obs.).
On the Namaqualand coastal plain, the inland limit of marine deposits is at
about 90 m asl., where a prominent cliff line has locally developed. The
marine deposits that extend seawards are locally fossiliferous and thus are
dated to ~16 Ma (Pether et al., 2000), during the Mid-Miocene Climatic
Optimum. These marine deposits are informally called the “90 m Package” or
“Kleinzee Formation”. Small, thin patches of residual mid-Miocene marine
inner-shelf deposits, preserved beneath Pliocene formations at low elevations,
are a common feature in the Namaqualand record. These isolated patches,
rarely thicker than 0.5 m thick and a few tens of metres in extent, have
preserved the shelly fauna, enabling recognition of their Miocene age.
Not all evidence of mid-Miocene time when the Saldanha-area coastal plain
was so extensively submerged has been “lost”. The phosphate mineralization
found around the summits of several granite hills dates from this time when
the summits were islands during the mid-Miocene submergence. The islands
were offshore seabird roosts, covered in guano, and the phosphorus leached
from the guano and impregnated the underlying granite, forming a kind of
“mineralogical fossil”.
These deposits were also the first phosphate
occurrences that attracted commercial attention. These occurrences and old
workings are also potential geosites for inclusion in a CMP.
When sea level receded from the mid-Miocene high, the coastal plain below
~90 m asl. would have been covered with marine sediments. Marine deposits,
such as rounded gravels or phosphatic marine sands, occurring in the 50-90
m asl. range, are likely of mid-Miocene age. The thickness of the Miocene
marine deposits above ~40 m asl. will have been reduced by erosion and
deflation and the residua will be weathered and disguised. Considerable
thicknesses of “phosphatic marine section” are suspect and very likely include
aeolian deposits.
In the Saldanha area, it is possible that some of the high-elevation (>~40 m
asl.) phosphatic deposits may date to the middle Miocene. If these are marine
deposits they are likely to be eroded remnants overlain by old aeolianites.
The latter, formed by reworking of the older marine deposits, may also be
phosphatic.
20
An example on the Vredenburg Peninsula is the “Varswater” phosphatic
sediments that form the eastern flank of Soetlandskop, exposed between 40100 m asl. near Stompneusbaai (Figure 1, blue QP polygon; cf. Figure 7), and
which are overlain by Langebaan Formation aeolianite. The phosphatic
material comprises brown sandstones, brown nodules and friable, sandy
phosphatic limestone, interbedded with layers of shelly limestone (Visser &
Toerien, 1973). Fossil oysters have been found on the northern slopes of
Soetlandskop, but these may have come from younger Pliocene deposits (e.g.
Uyekraal Fm., see below). An area underlain by phosphatic “Varswater”
deposits is thought to underlie the northern end of the Prospect Hill Fm.
aeolianites (Figure 1 cf. Figure 7). As the latter may be Late Miocene ~10 Ma
of age, the underlying marine deposits are also Miocene.
Patches of Miocene marine deposits are often locally preserved at lower
elevations, in topographic lows, beneath Pliocene marine deposits. As
mentioned above, the initial phase of the “Konings Vlei Gravel Fm.” could
have been formed during the mid-Miocene. This remains an open question,
only to be resolved by more fossil finds.
In short, the mid-Miocene “Saldanha Formation” certainly exists in the
subsurface of the Saldanha area, but it is yet to be unequivocally identified.
12
THE UPPER VARSWATER FORMATION
At LBW the early Pliocene transgression reached ~50-60 m asl., from which
sea level then receded, causing the shoreline to build out seawards (prograde)
and covering the previous MPPM with shallow, shoreface and beach deposits
(a regressive sequence). However, these regressive deposits have not been
identified at LBW. It is possible that the basal contact of the regressive
sequence is still unrecognized in the upper MPPM. Nevertheless, the
subaerially-exposed marine sediments of the prograded shoreline would then
have been subjected to erosion by streams and wind, reducing the original
thickness substantially and perhaps removing the regressive deposits
altogether.
Similarly, in the wider Saldanha area, outside of the embayments, the
regression from the early Pliocene sea-level high would have left a regressive
sequence mantling the emerged coastal plain, then subject to deflation by
wind and transformation into aeolianites.
Outcrops of phosphatic sands and rock are outlined (blue polygons, Varswater
Fm.kml). The main occurrence is the 3 areas around the LBW Fossil Park.
Fossil bones are noticed in these areas and are probably reworked from the
upper MPPM, or more likely, are occurrences on the erosion surface on top of
the MPPM. The “Varswater” phosphatic sediments of Soetlandskop between
40-100 m asl. near Stompneusbaai may be of Miocene age and need
investigation. A small fossil shell occurrence near Saldanha (blue dot)
appears to be of early Pliocene age, but material is very limited. These areas
21
are particularly sensitive and bulk earth works would need sustained
monitoring.
Westwards towards the coast, the Upper Varswater Formation has been
eroded during a subsequent high sea level and is expected to thin and
eventually pinch out, except for pockets preserved locally in topographic lows
in the granite bedrock or in the top of the Elandsfontyn Formation. It is
overlapped by the following formation.
13
THE UYEKRAAL FORMATION – MARINE
Sea level rose again in the middle Pliocene (~3.0 Ma) to a level now ~30 m
asl. West of the West Coast Fossil Park, a flat plain underlain by marine
deposits extends from ~20 m asl. towards the coast. Rogers (1983) named
the marine deposits the Uyekraal Shelly Sand Member of the Bredasdorp
Formation. It has a capping hardpan calcrete, beneath which is green-hued
shelly, gravelly sand with phosphatic casts (steinkerns) of molluscs and shark
teeth (Rogers, 1982, 1983).
Note that the Uyekraal Shelly Sand Member is not formally recognized and is
subsumed in the Varswater Formation, but it is deserving of being called the
“Uyekraal Formation”, Sandveld Group.
At various places around Saldanha Bay are exposures of shelly marine
deposits with Pliocene assemblages and these are the eroded fringes of the
Uyekraal Formation. (See Uyekraal Fm.kml - Leentjiesklip, Hoedjiespunt
peninsula, Diazville lower quarry, Duyker Eiland). On the basis of extinct fossil
shells, the Uyekraal shelly beds are correlated with the Hondeklip Bay Fm. of
Namaqualand, deposited during the mid-Pliocene ~3.0 Ma (Pether et al.,
2000). Similarly, the Uyekraal Fm. will be extensive beneath the outer several
km of the low-gradient coastal plain. It is probable that there are other
occurrences under thin cover on the steeper Vredenburg coast that could be
exposed during normal infrastructural earthworks.
North of the Berg River, Rogers (1980) recognized in boreholes a marine
formation extending seawards from ~30 m asl that he named the Bookram
Member of the Varswater Formation, the type borehole (S7) being on the farm
Bookram. This “Bookram Member” is likely to be of the same mid-Pliocene
age.
Fossil shells and some vertebrate fossils have previously been obtained from
deep excavations at Saldanha Steel that penetrated the Uyekraal Formation
(Roberts, 1997). At least some of these are reworked from the Varswater Fm.
or perhaps the mid-Miocene “Saldanha Formation. The Uyekraal Formation is
the youngest marine formation that has a warm-water shell fauna in opencoast deposits and a significant number of extinct species.
22
The current state of the aforementioned exposures should be investigated, as
input to a conservation/management plan. Some of these are already “wellknown” geosites that regularly feature in geological/palaeontological field trip
itineraries. Managed geosites will enhance the geotourism potential of the
area.
14
THE VELDDRIF FORMATION – MARINE AND ESTUARINE
After ~2.6 Ma the Earth went into “Ice House” mode (the Quaternary Period)
and major ice caps formed in the polar regions, subtracting water from the
oceans. During Ice Ages sea levels fluctuated at positions mainly below
present (Figure 8) and coastal rivers eroded their valleys to deeper levels.
These now-submerged shorelines were also the source of the sand for further
additions to the Langebaan Formation in the form of dune plumes blown far
inland.
Figure 8.
Sea level history for the middle and late Quaternary, showing
glacial/interglacial Marine Isotope Stages. From Siddall et al., 2007.
During the Quaternary period there were brief intervals of global warming
(interglacials), of which the present time is an example, when sea levels were
similar to the present level or several metres above or below present level.
23
The higher sea levels are the Quaternary “raised beaches” found at low
elevations (<15 m asl.) around the coast, where they are exposed in cliffs
beneath dune rocks, on top of low marine platforms fringing the coast and
within the lower reaches of valleys, e.g. the Berg River.. They comprise the
Velddrif Formation.
Most of the Velddrif Formation deposits that are exposed date to the Last
Interglacial (LIG) about 125 ka (ka: thousand years ago) and are found up to
~8 m asl. due to storm deposition, but the mean sea level was about 5-6 m
asl. The LIG is also known as Marine Isotope Stage 5e (MIS 5e).
These LIG shelly beach deposits are most extensive on Velddrif 110, tapering
off west of the Berg River mouth and northwards past Dwarskersbos. Where
more extensive, the Velddrif Fm. (VD) was mapped as unit QB1 (estuarine
and beach deposits) by Visser & Schoch (1973) (Figure 1, VD QB1.kml)).
Equivalent estuarine deposits are found along the banks of the Berg River
estuary as far upstream as Kruispad. VD fossils.kml marks fossil sites
specifically noted by Visser & Schoch, 1973) . Along the steeper, rocky,
granite coast of western St. Helena Bay are numerous exposures (small lightgreen spheres), but exposures are less common along the Vredenburg open
coast (VD Raised Beach 1.kml). South of Jacobsbaai, a prominent beach
ridge is present (VD Beach Terrace 1.kml). VD other outcrops.kml marks
shoreline exposures around Langebaan Lagoon and Saldanha Bay.
Farther inland are higher-lying marine terrace deposits up to 12-15 m asl.
This older raised beach is very poorly known and it is possible that beach
deposits of differing ages are preserved from place to place. It is probable
that most of such occurrences relate to an older interglacial high sea level
around 400 ka (MIS 11). However, Hendey & Cooke (1985) also argued that
the Skurwerug dune plume, dated to ~1.2 Ma, may be associated with an
early Quaternary palaeoshoreline at ~8-12 m asl. VD Raised Beach 2.kml
marks these higher, older deposits which are prevalent on the Posberg
Peninsula (small, dark-green spheres). These deposits are represented by
the inner beach ridge south of Jacobsbaai (VD Beach Terrace 2.kml).
Deposits relating to the MIS 7 interglacial about 200 ka are often found in the
bases of the Langebaan Formation aeolianite seacliffs and exposed in the
intertidal zone and below sea level. These include estuarine/lagoonal and
coastal vlei deposits, the latter reflecting high water tables associated with the
nearby high sea level. The vlei deposits include organic-rich and peaty beds
with terrestrial fossil bones.
During the Last Ice Age, sea level had dropped down to about 130 m below
present during the last Glacial maximum (LGM – Figure 4). When sea level
returned it stood at a slightly higher level 3-4 m above present sea level
between 7.5 to 6 ka. The LIG raised beach was eroded by waves and in
places altogether removed and sea cliffs eroded into the old dunes of the
Langebaan Formation. The deposits of a much younger raised beach, called
the “Holocene High”, where deposited along the coast (not shown in Figure
1). These Holocene beach deposits may be quite extensive in places where
there was lots of sand available, such as the St. Helena Bay Coast. In other
24
areas, particularly cliffed coast, ongoing coastal erosion has removed this
“Holocene High” beach.
The sensitivity of the younger (outer, 6m) open-coast Velddrif Formation is
moderate and of local significance overall. The exposures along the Berg
River contain exotic warm-water fossil shells and extinct species. These are
just a few sites and are sensitive. The older parts (higher, ~8-15 m asl.) are
poorly exposed and practically unstudied.
Bulk earth works into the Velddrif Formation, that create significant exposure,
must be mitigated by sampling and recording. Although the open-coast shelly
fauna is mainly modern, faunal changes are present, surprises occur and rare
bones may be spotted in the deposits. The application of dating techniques to
shells, such as amino-acid racemisation, requires spatially-distributed
samples, from many localities, to build a comparative database.
In summary, the significance of shell fossils involves:




Significance in the history of sea-level change, coastal evolution and
associated faunal changes.
For future radiometric and chemical dating purposes (rates of coastal
change).
Modern analytical techniques such as stable isotopic analyses can reveal
indications of environmental conditions of the past.
Preservation for the application of yet unforeseen investigative techniques.
As for the previous, the state of the better exposures of the Velddrif Formation
should be evaluated, as input to a CMP. Similarly, some of these are already
“well-known” geosites that regularly feature in field trip itineraries.
14.1
PALAEONTOLOGY OF THE VELDDRIF FORMATION.
The Late Quaternary LIG deposits at various locations around the coast of the
western and southern Cape are of particular interest due to the occurrence of
several species of exotic fossil shells of West African origin, today found living
in the tropics along the Angolan coast and farther northwards. The taxonomy
of these exotic or “extralimital” species has been dealt with in Kilburn &
Tankard (1975) and Kensley (1974, 1985a,b).
To account for the occurrence of the West African species, Tankard (1975a)
suggested that, during the LIG, shallow-water coastal embayments were more
numerous due to the higher sea-level. Water temperature in the sheltered
embayments was warmer than at present due to increased insolation, but
open-coast sea-temperatures were similar to the present day regime.
Postulating a poleward shift of the LIG South Atlantic Anticyclone relative to its
present mean position, he suggested a concomitant southward shift of
isotherms and the West African molluscan province, bringing tropical taxa
closer to the Cape. Periodic southward incursions of tropical (Angolan) water
carried the larvae of tropical taxa through the environmental barrier of
Benguela upwelling, to warm embayments along the LIG coast. Further
southward dispersal could have been accomplished by inshore southward
currents developed during westerly winds associated with the passage of midlatitude cyclones.
25
The episodic southward incursions of tropical Angolan water into the northern
Benguela invoked by Tankard (1975a) have subsequently become known as
Benguela Niños (Shannon et al., 1986). The molluscan evidence therefore
suggests that oceanographic conditions in the LIG northern Benguela involved
frequent or extended Benguela Niño-type situations at some time.
15
THE AEOLIANITES
Aeolianites or “dune rocks/fossil dunes” overlie the marine deposits of the
coastal plain, i.e. the “Saldanha”, upper Varswater and Uyekraal formations.
They rest on wind-deflation erosion surfaces formed on the marine deposits
and are comprised of calcareous sand reworked from the marine deposits by
wind and also blown off the beaches of the receding sea levels. The
calcareous aeolianites are evident in the coastal landscape as the ridges, low
hills and mounds beneath a capping calcrete crust, or “surface limestone” in
old terminology.
Until recently the calcareous aeolianites of the west coast of the southern
Cape have all been lumped in the Langebaan Formation or “Langebaan
Limestones” (Figure 1, deep yellow, QC), thus including various aeolianites of
different ages as an “amalgam” of the dune plumes that formed on the coastal
plain, at differing places and times. This is reflected in the different ages
indicated from fossils found at various places. Of course, the aeolianites must
be younger than the underlying “foundation” of marine deposits. Potentially
the oldest Miocene aeolianites would overlie mid-Miocene Saldanha or late
Miocene KGM marine deposits, mid-Pliocene and younger aeolianites would
overlie the Upper Varswater Fm. and early Quaternary and younger
aeolianites would overlie the Uyekraal Fm.
16
THE PROSPECT HILL FORMATION - AEOLIANITE
The inner aeolianite ridge stretching north from Saldanha Bay up the coast to
near Paternoster has been found to have fossil eggshell fragments of extinct
ostriches (Diamantornis wardi) and extinct land snail forms (Roberts & Brink,
2002). Diamantornis wardi is dated as Miocene 10-12 Ma in the Namib Desert
(Senut & Pickford, 1995) and, based on dated occurrences in East Africa and
Arabia, an age of 12-9 Ma is indicated. These aeolianites, previously
belonging to the Langebaan Formation, are now called the Prospect Hill
Formation (Figure 1, PH, magenta outline, Prospect Hill Fm.kml), due to the
significantly older age indicated by the fossils (Roberts & Brink, 2002; Roberts
et al., 2006). Separation of this aeolianite as a distinct formation is also
justified by it being lithologically distinct from the younger aeolianites that abut
it.
26
However, the age of this formation is contentious. Sand-size marine
microfossil species, blown from the ancient beaches of the time, suggest that
the dunes formed by deflation of younger Pliocene marine deposits (Dale &
McMillan, 1999). Strontium isotope stratigraphy also indicates a younger,
latest Miocene/early Pliocene age (Franceschini & Compton, 2004). A small
fossil shell occurrence in the railway cutting just south of the Prospect Hill
quarry (blue dot), apparently underlying the formation, appears to be of early
Pliocene, Varswater Fm. age.
The Prospect Hill Formation is quarried and expansion of the mining is
proposed. Palaeontological mitigation plans must be included in the mining
EMP. Notably, the fossil discoveries at the Prospect Hill quarry were made
during the carrying out of palaeontological mitigation. Regular mitigation of
mining pit exposures and of development earth works has the potential for
further discoveries that stand to have heritage/scientific benefits in increasing
the knowledge of the Prospect Hill Formation and resolving the conflicting
evidence for its age.
17
THE LANGEBAAN FORMATION - AEOLIANITE
The considerable extent of the Langebaan Formation aeolianites (QC, deep
yellow) is evident in Figure 1 and attests to the persistence of strong southerly
winds and the availability of calcareous sand on beaches. The largest tract of
amalgamated dune plumes (Geelbek Plume) extends from the
Geelbek/Langebaan Lagoon/16 Mile Beach area. The beaches of Saldanha
Bay supplied the Saldanha Plume extending northwards and west of the De
Op/Kleinberg topo-high. Further accumulations formed along the Vredenburg
Peninsula and on Posberg.
Much of the aeolian sand is tiny fragments of shell. The cementing of this
“calcarenite” is generally quite weak, but much denser cementing has taken
place in the uppermost part of the fossil dunes in the form of a “carapace” or
capping of calcrete. The calcrete is a type of cemented soil called a
pedocrete, formed in the near-surface by evapo-transpiration after the dunes
became inactive and were vegetated. The aeolianites contain further
calcretes and leached terra rosa soils at depth, attesting to a number of
periods of reduced rates of sand accumulation, surface stability and soil
formation.
There are more marked breaks between periods of sand
accumulation, shown by erosion surfaces or very thick calcretes formed over a
long time.
As mentioned, the dune plumes accumulated episodically, under the influence
of climate (windiness, rainfall) and available sand source areas (sea-level
position, sediment supply), with erosion and re-deposition of previous dunes
also taking place in some areas, separated by periods of stability and soil
formation. The most favourable sand supply conditions seem to have
prevailed at sea levels below present, in the range of 10-40 m bsl.
27
The Langebaan Fm. aeolianites do not appear to be very fossiliferous, but
fossils from this formation and its correlates have been a prime source of
information on Quaternary faunas and archaeology (Fossil bone finds.kml).
Most of the fossils in the aeolianites are associated with particular contexts,
particularly buried, stable surfaces (palaeosurfaces) where time has permitted
bones to accumulate. The common fossils include shells of land snails, fossil
tortoises, ostrich incl. egg fragments, sparsely scattered bones etc. Bone and
shell concentrations related to buried Early and Middle Stone Age
archaeological sites may occur in this context in the aeolianite, particularly in
its upper part.
“Blowout” erosional palaeosurfaces may carry fossils
concentrated by the removal of sand by the wind. Hollows between dunes
(interdune areas) are the sites of ponding of water seeping from the dunes,
leading to the deposits of springs, marshes and vleis. Being waterholes, such
are usually richly fossiliferous. The lairs of hyaenas, with concentrations of
bones of antelopes and small carnivores, have proved a rich source of
“stashed” bones of various ages.. The calcretes have facilitated overhangs
and crevices for use as lairs, superimposing bone concentrations into an
older, partly-cemented aeolianite.
The file Langebaan Fm fossils.kml marks only three sites – these were
evidently sites where fossil land snails were particularly noticeable for Visser &
Schoch (1973). There will be many more such sites. At least one extinct land
snail has been found and is seemingly useful for correlating the older parts of
the Langebaan Formation.
At the Diazville lower quarry, Langebaan Fm. aeolianite overlying the midPliocene, marine Uyekraal Formation enclosed vertebrate material indicative
of a late Pliocene or younger age (Roberts & Brink, 2002) (Diazville Member.
The fossil suid (bushpig) from Skurwerug dates the fossil dune-plume there to
the early Quaternary ~1.2 Ma (Hendey & Cooke, 1985). At Elandsfontein a
fossil interdunal vlei was exposed by deflation, the large number of fossil
bones and ESA tools indicate an age of ~600 ka (Klein et. al., 2007). At
Geelbek dunefield, dating of three sequential calcretes indicated their
formation at ~250, ~150 and ~65 ka, i.e. stability/soil formation during glacial
periods (Felix-Henningsen et. al., 2003). Dating of aeolianites near Cape
Town by luminescence methods shows accumulation during MIS 7 and MIS 5
(interglacials), with calcrete formation in the intervening glacial (ice age)
periods (Roberts et al., 2009). At Kraalbaai the aeolianite (Kraal Bay Member)
is dated to 117-79 ka (Roberts & Berger, 1997). Middle and late Quaternary
ages are indicated by relationships to Last Interglacial (~125 ka) and earlier
shoreline deposits.
At Spreeuwal on the shore of Saldanha Bay, fossil vlei deposits are exposed
in the intertidal zone and contain large mammal bones and some MSA
artefacts (Avery & Klein, 2009). The larger mammal component includes
extinct species and others not recorded historically in the Western Cape.
Small mammals, birds, reptiles, amphibians, freshwater gastropods and
ostracods also occur.
Examples of hyaena bone accumulations in dens within the partly-lithified
dune rocks are the Sea Harvest and Hoedjiespunt sites in Saldanha Bay.
Hoedjiespunt is the find site of fossil teeth of a hominid in deposits 200-300 ka
28
old. The Sea Harvest site produced an essentially modern human tooth that is
older than 40 ka. Both sites provided considerable samples of the faunas of
those times, thanks to the brown hyaenas.
The marked fossil bone sites are certainly not all that have been discovered
and more recent finds are under-represented. Sometimes bones have been
exposed on the surface by erosion, usually by wind. Other finds have been
spotted in the sides of excavations. Excavations into the Langebaan Fm.
must be monitored in order to spot fossil bone. Spoil from excavations must
be inspected as far as possible. Large excavations, such as quarrying, must
be periodically inspected and recorded.
18
THE SPRINGFONTYN FORMATION – MAINLY AEOLIAN
The Springfontyn Formation is an informal category that accommodates the
mainly non-calcareous, windblown sand sheets and dunes that have covered
parts of the landscape during the Quaternary. Its areal extent is depicted on
the geological map (Figure 1) as surficial units Q2 (older cover) and Q1
(younger cover). The Springfontyn Fm. consists of the sequences beneath
these “coversands”, i.e. SubQ2 and SubQ1.
Unit Q2 is characterized by its surface manifestation as the distinct
“heuweltjiesveld”, the densely dot-patterned landscape of low hillocks that are
termitaria made by Microhodotermes viator. Its true areal extent is not
immediately appreciated as it laps onto bedrock and onto the Langebaan Fm.,
but for the purposes of geological mapping (Figure 1) these overlap areas
were depicted “transparently” as outlines. It is also apparent that Q2 underlies
large areas now covered by Q1. “Heuweltjies” are longed-lived features that
are persistently inhabited by generations of termites. They occur in a
background of light reddish-brown, sandy soil, but they have internal calcretes
due to enrichment in calcium by the plant-gathering activity of the termites. It
seems that over large areas the termitaria are inactive and are now “fossil”
features in the landscape.
The dot-patterned “heuweltjiesveld” is merely the surface-soil characteristic of
Unit Q2. Not much detail is known about Unit Q2 at depth (Sub-Q2).
Pedogenic layers of ferruginous concretions, clayey beds and minor calcretes
occur among sandy-soil beds. Clearly Q2 will differ from place to place
according to the local setting. In this area, in addition to mainly windblown
sands from the south, Sub-Q2 will likely comprise the local
colluvial/hillwash/sheetwash deposits, small slope-stream deposits, alluvium in
the lower valleys and vlei and pan deposits.
Surface Unit Q1 is a younger “coversand” geological unit and is “white to
slightly-reddish sandy soil” (Visser & Toerien, 1971; Visser & Schoch, 1973).
These are patches of pale sand deposited in geologically-recent times. In
places these sands are undergoing semi-active transport and locally have
been remobilized into active sandsheets and dunes.
29
Chase & Thomas (2007) have cored Q1 coversands in a regional survey of
various settings along the West Coast and applied optically stimulated
luminescence (OSL) dating techniques to establish the timing of sand
accumulation. Their results indicate several periods of deposition of Q1 during
the last 100 ka, with activity/deposition at 63–73, 43–49, 30–33, 16–24 and 4–
5 ka. Notably, underlying sands produced dates from ~150 to ~600 ka,
reflecting the accumulation of Unit Q2 in the middle Quaternary.
The Springfontyn Formation aeolianites date from at least ~600 ka, if not older
and, in parts, may be of similar ages as parts of the Langebaan Fm., but
derived from less calcareous sources and/or deposited in settings more prone
to subsequent groundwater leaching in water tables. The reworking of older
coastal-plain deposits was likely the major sediment source. It is also possible
that decalcified marine sands have not been recognized as marine in origin,
especially if only encountered in boreholes, and been included in the
Springfontyn Fm.
The Springfontyn Formation has clearly accumulated episodically over a
considerable time span and thus will include palaeosurfaces with bone fossils
and other settings such as vlei deposits with considerable fossil potential.
Earth works should be basically monitored during the Construction Phase
EMPs, with Fossil Find reporting procedures in place and a palaeontologist on
standby.
18.1
BAARD’S QUARRY FLUVIATILE DEPOSITS (BQF)
Baard’s Quarry was situated just east of the WC Fossil Park, near
Langebaanweg railway station. Phosphatic rock material was the targeted ore
at Baard’s Quarry, where mining commenced in 1943. The quarry was closed
and backfilled in the early 1960s.
Observations at Baard’s Quarry and nearby on Muishond Fontein show that
the top of the Varswater Fm. may be incised by donga-like, small-scale
channels with multiple cut & fill structures (Tankard, 1974b; Visser & Schoch,
1973). Figure 9 shows the BQF deposits overlying the MPPM and beneath ~1
m of Springfontyn Q2 coversands.
In the BQF example, the lower channel fills were very fossiliferous (Hendey,
1978). The presence of Equus (horse/zebra) indicates an age younger than
2.6 Ma., whilst other taxa suggest an age >2 Ma. Few early Quaternary
mammal faunal assemblages have been found and further discoveries of
BQF-type deposits would be highly significant.
These small-scale watercourse deposits are expected to occupy relict
drainage lines, but now, due to covering aeolianites and coversands, these
lines are not always obvious in the landscape. Notably, the occurrences may
be quite shallow (Figure 9) and may be unexpectedly encountered in
earthworks in the Springfontyn Formation, such as foundations for wind
turbines. For the present, the BQF deposits are regarded as a basal member
of the Springfontyn Formation.
30
Figure 9. Schematic section of Baard’s Quarry deposits. From Tankard, 1974b.
19
THE WITZAND FORMATION – RECENT DUNES
The latest addition of dunes to the coastal plain is Unit Q5 (Figure 2),
otherwise known as (Rogers, 1980), for obvious reason. These are sands
blown from the beach in the last few thousand years and accumulated in the
form of a narrow dune cordon or “sand wall” parallel to the coast, or as dune
plumes transgressing a few kilometres inland.
20
THE IMPORTANCE OF BOREHOLE CORES
Borehole data logs and cores, from drilling for water (“Water Affairs”) and from
specific stratigraphic investigational programs carried out by the Geological
Survey, have been invaluable for the understanding of the subsurface geology
of the Saldanha area. The Elandsfontyn Formation is mainly known from
borehole cores and is unlikely to be exposed. Similarly, the older Miocene
31
and Pliocene marine deposits are not likely to be exposed in most earth
works, except in limited areas nearer the coast where aeolianites are thinner.
Cores through the thick aeolianites show features such as palaeosols that
reveal their accumulation history.
At present the borehole cores obtained during stratigraphic drilling
investigations (Rogers, 1980) are curated by the Council for Geoscience. The
existing borehole cores from the Saldanha area are a diminishing resource as
material gets used up in ongoing analyses.
Geotechnical coring programmes are often preliminary to large industrial
developments. Such a geotechnical core set is a sample of the “natural
archive” of the history of the Saldanha Bay area and the availability of material
of such scientific value is not likely to be repeated in the foreseeable future. It
is recommended that existing and future borehole core sets are donated to the
Council for Geoscience after the geotechnical data requirements are met,
rather than to eventually discard them. The cores will then be available for
archiving as type material, public display and for scientific analysis, particularly
the application of modern isotopic and biogeochemical techniques (molecular
fossils).
21
PROPOSED WIND ENERGY FACILITIES
Proposed wind energy facilities (WEFs), involving substantial numbers (100s)
of spatially-distributed turbine foundation pits, present an unprecedented
scientific opportunity (should some of the proposed projects proceed). Most of
these excavations, up to 20X20 m in area and 4 m deep, will be in the
Springfontyn and Langebaan formations. In spite of the overall low fossil
potential, there is a good probability that fossils will be exposed at some point
during excavating hundreds of such foundation pits.
The PIAs for these proposed WEFs must recommend that the Construction
Phase EMPs include the monitoring of bulk earth works by on-site personnel
and field inspections by a palaeontologist. Appendices 1 and 2 outline
monitoring by construction personnel and general Fossil Find Procedures.
The aim of field inspection is to examine a representative sample of the
various deposits exposed in the turbine excavations, recording context, fossil
content and to take samples. As many as possible should be basically
recorded and key pit sections identified and described and sampled in more
detail (e.g. for OSL dating).
32
22
APPLICATION FOR A PALAEONTOLOGICAL PERMIT
A permit from Heritage Western Cape (HWC) is required to excavate fossils.
The applicant should be the qualified specialist responsible for assessment,
collection and reporting (palaeontologist).
A permit has not been applied for prior to the making of excavations. Should
fossils be found that require rapid collecting, application for a retrospective
palaeontological permit will be made to HWC immediately.
The application requires details of the registered owners of the sites, their
permission and a site-plan map.
All samples of fossils must be deposited at a SAHRA-approved institution.
23
REPORTING
Should fossils be found a detailed report on the occurrence/s must be
submitted. This report is in the public domain and copies of the report must be
deposited at the IZIKO S.A. Museum and Heritage Resources Western Cape.
It must fulfil the reporting standards and data requirements of these bodies.
The report will be in standard scientific format, basically:
 A summary/abstract.
 Introduction.
 Previous work/context.
 Observations (incl. graphic sections, images).
 Palaeontology.
 Interpretation.
 Concluding summary.
 References.
 Appendices
The draft report will be reviewed by the client, or externally, before submission
of the Final Report.
33
24
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Tankard, A.J. 1975a. Thermally anomalous Late Pleistocene molluscs from
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1975c.
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25
GLOSSARY
~ (tilde): Used herein as “approximately” or “about”.
Aeolian: Pertaining to the wind. Refers to erosion, transport and deposition of
sedimentary particles by wind. A rock formed by the solidification of
aeolian sediments is an aeolianite.
AIA: Archaeological Impact Assessment.
Alluvium: Sediments deposited by a river or other running water.
Archaeology: Remains resulting from human activity which are in a state of
disuse and are in or on land and which are older than 100 years,
including artefacts, human and hominid remains and artificial features
and structures.
asl.: above (mean) sea level.
Bedrock: Hard rock formations underlying much younger sedimentary
deposits.
Calcareous: sediment, sedimentary rock, or soil type which is formed from or
contains a high proportion of calcium carbonate in the form of calcite or
aragonite.
Calcrete: An indurated deposit (duricrust) mainly consisting of Ca and Mg
carbonates. The term includes both pedogenic types formed in the
near-surface soil context and non-pedogenic or groundwater calcretes
related to water tables at depth.
Clast: Fragments of pre-existing rocks, e.g. sand grains, pebbles, boulders,
produced by weathering and erosion. Clastic – composed of clasts.
Colluvium: Hillwash deposits formed by gravity transport downhill. Includes
soil creep, sheetwash, small-scale rainfall rivulets and gullying, slumping
and sliding processes that move and deposit material towards the foot of
the slopes.
Coversands: Aeolian blanket deposits of sandsheets and dunes.
Duricrust: A general term for a zone of chemical precipitation and hardening
formed at or near the surface of sedimentary bodies through pedogenic
and (or) non-pedogenic processes. It is formed by the accumulation of
soluble minerals deposited by mineral-bearing waters that move upward,
downward, or laterally by capillary action, commonly assisted in arid
settings by evaporation. Classified into calcrete, ferricrete, silcrete.
ESA: Early Stone Age. The archaeology of the Stone Age between 2 000
000 and 250 000 years ago.
EIA: Environmental Impact Assessment.
EMP: Environmental Management Plan.
Ferricrete:
Indurated deposit (duricrust) consisting predominantly of
accumulations of iron sesquioxides, with various dark-brown to yellowbrown hues. It may form by deposition from solution or as a residue
39
after removal of silica and alkalis. Like calcrete it has pedogenic and
groundwater forms. Synonyms are laterite, iron pan or “koffieklip”.
Fluvial deposits: Sedimentary deposits consisting of material transported by,
suspended in and laid down by a river or stream.
Fm.: Formation.
Fossil: Mineralised bones of animals, shellfish, plants and marine animals. A
trace fossil is the disturbance or structure produced in sediments by
organisms, such as burrows and trackways.
Heritage: That which is inherited and forms part of the National Estate
(Historical places, objects, fossils as defined by the National Heritage
Resources Act 25 of 1999).
HIA: Heritage Impact Assessment.
LSA: Late Stone Age. The archaeology of the last 20 000 years associated
with fully modern people.
LIG:
Last Interglacial. Warm period 128-118 ka BP. Relative sea-levels
higher than present by 4-6 m. Also referred to as Marine Isotope Stage
5e or “the Eemian”.
Midden: A pile of debris, normally shellfish and bone that have accumulated
as a result of human activity.
MIS: Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen
isotope stages (OIS), are alternating warm and cool periods in the
Earth's paleoclimate, deduced from oxygen isotope data reflecting
changes in temperature derived from data from deep sea core samples.
Working backwards from the present, MIS 1 in the scale, stages with
even numbers representing cold glacial periods, while the oddnumbered stages represent warm interglacial intervals.
MSA: Middle Stone Age. The archaeology of the Stone Age between 20-300
000 years ago associated with early modern humans.
OSL:
Optically stimulated luminescence. One of the radiation exposure
dating methods based on the measurement of trapped electronic
charges that accumulate in crystalline materials as a result of low-level
natural radioactivity from U, Th and K. In OSL dating of aeolian quartz
and feldspar sand grains, the trapped charges are zeroed by exposure
to daylight at the time of deposition. Once buried, the charges
accumulate and the total radiation exposure (total dose) received by the
sample is estimated by laboratory measurements.
The level of
radioactivity (annual doses) to which the sample grains have been
exposed is measured in the field or from the separated minerals
containing radioactive elements in the sample. Ages are obtained as the
ratio of total dose to annual dose, where the annual dose is assumed to
have been similar in the past.
Palaeo: Or paleo. Ancient. Greek palaio-, from palaios, ancient, from palai,
long ago.
Palaeontology: The study of any fossilised remains or fossil traces of animals
or plants which lived in the geological past and any site which contains
such fossilised remains or traces.
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Palaeosol: An ancient, buried soil whose composition may reflect a climate
significantly different from the climate now prevalent in the area where
the soil is found. Burial reflects the subsequent environmental change.
Palaeosurface: An ancient land surface, usually buried and marked by a
palaeosol or pedocrete, but may be exhumed by erosion (e.g. wind
erosion/deflation) or by bulk earth works.
Peat: partially decomposed mass of semi-carbonized vegetation which has
grown under waterlogged, anaerobic conditions, usually in bogs or
swamps.
Pedogenesis/pedogenic: The process of turning sediment into soil by
chemical weathering and the activity of organisms (plants growing in it,
burrowing animals such as worms, the addition of humus etc.).
Pedocrete: A duricrust formed by pedogenic processes.
Phytoliths: Very small particles of silica (between 5 and 100 microns) that
form in the epidermal tissues of plant leaves and stems and have
distinctive and repeatable shapes. They survive well in most soils and
sediments.
PIA: Palaeontological Impact Assessment.
SAHRA: South African Heritage Resources Agency – the compliance
authority, which protects national heritage.
Stone Age: The earliest technological period in human culture when tools
were made of stone, wood, bone or horn. Metal was unknown.
25.1
GEOLOGICAL TIME SCALE TERMS (YOUNGEST TO OLDEST).
For further info, go to www.stratigraphy.org
ka: Thousand years or kilo-annum (103 years). Implicitly means “ka ago” i.e.
duration from the present, but “ago” is omitted. The “Present” refers to
1950 AD. Generally not used for durations not extending from the
Present. Sometimes “kyr” is used instead.
Ma: Millions years, mega-annum (106 years). Implicitly means “Ma ago” i.e.
duration from the present, but “ago” is omitted. The “Present” refers to
1950 AD. Generally not used for durations not extending from the
Present.
Holocene: The most recent geological epoch commencing 11.7 ka till the
present.
Pleistocene: Epoch from 2.6 Ma to 11.7 ka. Late Pleistocene 11.7–126 ka.
Middle Pleistocene 135–781 ka. Early Pleistocene 781–2588 ka (0.782.6.Ma).
Quaternary: The current Period, from 2.6 Ma to the present, in the Cenozoic
Era. The Quaternary includes both the Pleistocene and Holocene
epochs. The terms early, middle or late in reference to the Quaternary
should only be used with lower case letters because these divisions are
informal and have no status as divisions of the term Quaternary. The
sub-divisions 'Early', 'Middle' or 'Late' apply only to the word Pleistocene.
41
As used herein, early and middle Quaternary correspond with the
Pleistocene divisions, but late Quaternary includes the Late Pleistocene
and the Holocene.
Pliocene: Epoch from 5.3-2.6 Ma.
Miocene: Epoch from 23-5 Ma.
Oligocene: Epoch from 34-23 Ma.
Eocene: Epoch from 56-34 Ma.
Paleocene: Epoch from 65-56 Ma.
Cenozoic: Era from 65 Ma to the present. Includes Paleocene to Holocene
epochs.
Cretaceous: Period in the Mesozoic Era, 145-65 Ma.
Jurassic: Period in the Mesozoic Era, 200-145 Ma.
Precambrian: Old crustal rocks older than 542 Ma (pre-dating the Cambrian).
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26
APPENDIX 1 – MONITORING FOR FOSSILS
A persistent monitoring presence over the period during which excavations are
made, by either an archaeologist or palaeontologist, is generally not practical.
The field supervisor/foreman and workers involved in digging excavations
must be encouraged and informed of the need to watch for potential fossil and
buried archaeological material. Workers seeing potential objects are to report
to the field supervisor who, in turn, will report to the ECO. The ECO will inform
the archaeologist and/or palaeontologist contracted to be on standby in the
case of fossil finds.
To this end, responsible persons must be designated. This will include
hierarchically:
 The field supervisor/foreman, who is going to be most often in the field.
 The Environmental Control Officer (ECO) for the project.
 The Project Manager.
Should the monitoring of the excavations be a stipulation in the Archaeological Impact Assessment, the contracted Monitoring Archaeologist (MA) can
also monitor for the presence of fossils and make a field assessment of any
material brought to attention. The MA is usually sufficiently informed to
identify fossil material and this avoids additional monitoring by a
palaeontologist. In shallow coastal excavations, the fossils encountered are
usually in an archaeological context.
The MA then becomes the responsible field person and fulfils the role of
liaison with the palaeontologist and coordinates with the developer and the
Environmental Control Officer (ECO).
If fossils are exposed in nonarchaeological contexts, the palaeontologist should be summoned to
document and sample/collect them.
Other alternatives could be considered, such as the employment of a
dedicated monitor for the construction period. For instance, a local person
could be detached from or trained by personnel at the West Coast Fossil Park.
26.1
CONTACTS FOR REPORTING OF FOSSIL FINDS.
West Coast Fossil Park

Pippa Haarhoff: 083 289 6902, 022 766 1606, [email protected]
Iziko Museums of Cape Town: SA Museum, 021 481 3800.

Dr Graham Avery. 021 481 3895, 083 441 0028.

Dr Deano Stynder. 021 481 3894.
Heritage Western Cape
 Justin Bradfield. 021 483 9543
 Jenna Lavin: 021 483 9685
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27
APPENDIX 2 - FOSSIL FIND PROCEDURES
In the context under consideration, it is improbable that fossil finds will require
declarations of permanent “no go” zones. At most a temporary pause in
activity at a limited locale may be required. The strategy is to rescue the
material as quickly as possible.
The procedures suggested below are in general terms, to be adapted as befits
a context. They are couched in terms of finds of fossil bones that usually
occur sparsely, such as in the aeolian deposits. However, they may also
serve as a guideline for other fossil material that may occur.
In contrast, fossil shell layers are usually fairly extensive and can be easily
documented and sampled (See section 15.5).
Bone finds can be classified as two types: isolated bone finds and bone
cluster finds.
27.1
ISOLATED BONE FINDS
In the process of digging the excavations, isolated bones may be spotted in
the hole sides or bottom, or as they appear on the spoil heap. By this is
meant bones that occur singly, in different parts of the excavation. If the
number of distinct bones exceeds 6 pieces, the finds must be treated as a
bone cluster (below).
Response by personnel in the event of isolated bone finds
 Action 1: An isolated bone exposed in an excavation or spoil heap
must be retrieved before it is covered by further spoil from the
excavation and set aside.
 Action 2: The site foreman and ECO must be informed.
 Action 3: The responsible field person (site foreman or ECO) must
take custody of the fossil. The following information to be recorded:
o Position (excavation position).
o Depth of find in hole.
o Digital image of hole showing vertical section (side).
o Digital image of fossil.
 Action 4: The fossil should be placed in a bag (e.g. a Ziplock bag),
along with any detached fragments. A label must be included with the
date of the find, position info., depth.
 Action 5: ECO to inform the developer, the developer contacts the
standby archaeologist and/or palaeontologist. ECO to describe the
occurrence and provide images asap. by email.
Response by Palaeontologist in the event of isolated bone finds
The palaeontologist will assess the information and liaise with the developer
and the ECO and a suitable response will be established.
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27.2
BONE CLUSTER FINDS
A bone cluster is a major find of bones, i.e. several bones in close proximity or
bones resembling part of a skeleton. These bones will likely be seen in
broken sections of the sides of the hole and as bones appearing in the bottom
of the hole and on the spoil heap.
Response by personnel in the event of a bone cluster find
 Action 1: Immediately stop excavation in the vicinity of the potential
material. Mark (flag) the position and also spoil that may contain
fossils.
 Action 2: Inform the site foreman and the ECO.
 Action 3: ECO to inform the developer, the developer contacts the
standby archaeologist and/or palaeontologist. ECO to describe the
occurrence and provide images asap. by email.
Response by Palaeontologist in the event of a bone cluster find
The palaeontologist will assess the information and liaise with the developer
and the ECO and a suitable response will be established. It is likely that a
Field Assessment by the palaeontologist will be carried out asap.
It will probably be feasible to “leapfrog” the find and continue the excavation
farther along, or proceed to the next excavation, so that the work schedule is
minimally disrupted. The response time/scheduling of the Field Assessment is
to be decided in consultation with developer/owner and the environmental
consultant.
The field assessment could have the following outcomes:
 If a human burial, the appropriate authority is to be contacted (see
AIA). The find must be evaluated by a human burial specialist to
decide if Rescue Excavation is feasible, or if it is a Major Find.
 If the fossils are in an archaeological context, an archaeologist must be
contacted to evaluate the site and decide if Rescue Excavation is
feasible, or if it is a Major Find.
 If the fossils are in an palaeontological context, the palaeontologist
must evaluate the site and decide if Rescue Excavation is feasible, or if
it is a Major Find.
27.3
RESCUE EXCAVATION
Rescue Excavation refers to the removal of the material from the just the
“design” excavation. This would apply if the amount or significance of the
exposed material appears to be relatively circumscribed and it is feasible to
remove it without compromising contextual data. The time span for Rescue
Excavation should be reasonably rapid to avoid any or undue delays, e.g. 1-3
days and definitely less than 1 week.
In principle, the strategy during mitigation is to “rescue” the fossil material as
quickly as possible. The strategy to be adopted depends on the nature of the
occurrence, particularly the density of the fossils. The methods of collection
would depend on the preservation or fragility of the fossils and whether in
loose or in lithified sediment. These could include:
45


On-site selection and sieving in the case of robust material in sand.
Fragile material in loose/crumbly sediment would be encased in blocks
using Plaster-of Paris or reinforced mortar.
If the fossil occurrence is dense and is assessed to be a “Major Find”, then
carefully controlled excavation is required.
27.4
MAJOR FINDS
A Major Find is the occurrence of material that, by virtue of quantity,
importance and time constraints, cannot be feasibly rescued without
compromise of detailed material recovery and contextual observations.
A Major Find is not expected.
Management Options for Major Finds
In consultation with developer/owner and the environmental consultant, the
following options should be considered when deciding on how to proceed in
the event of a Major Find.
Option 1: Avoidance
Avoidance of the major find through project redesign or relocation. This
ensures minimal impact to the site and is the preferred option from a heritage
resource management perspective. When feasible, it can also be the least
expensive option from a construction perspective.
The find site will require site protection measures, such as erecting fencing or
barricades. Alternatively, the exposed finds can be stabilized and the site
refilled or capped. The latter is preferred if excavation of the find will be
delayed substantially or indefinitely. Appropriate protection measures should
be identified on a site-specific basis and in wider consultation with the heritage
and scientific communities.
This option is preferred as it will allow the later excavation of the finds with due
scientific care and diligence.
Option 2: Emergency Excavation
Emergency excavation refers to the “no option” situation wherein avoidance is
not feasible due to design, financial and time constraints. It can delay
construction and emergency excavation itself will take place under tight time
constraints, with the potential for irrevocable compromise of scientific quality.
It could involve the removal of a large, disturbed sample by excavator and
conveying this by truck from the immediate site to a suitable place for
“stockpiling”. This material could then be processed later.
Consequently, emergency excavation is not a preferred option for a Major
Find.
27.5
EXPOSURE OF FOSSIL SHELL BEDS
Response by personnel in the event of intersection of fossil shell beds
46




Action 1: The site foreman and ECO must be informed.
Action 2: The responsible field person (site foreman or ECO) must
record the following information:
o Position (excavation position).
o Depth of find in hole.
o Digital image of hole showing vertical section (side).
o Digital images of the fossiliferous material.
Action 3: A generous quantity of the excavated material containing
the fossils should be stockpiled near the site, for later examination and
sampling.
Action 4: ECO to inform the developer, the developer contacts the
standby archaeologist and/or palaeontologist. ECO to describe the
occurrence and provide images asap. by email.
Response by Palaeontologist in the event of fossil shell bed finds
The palaeontologist will assess the information and liaise with the developer
and the ECO and a suitable response will be established. This will most likely
be a site visit to document and sample the exposure in detail, before it is
covered up.
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