Palaeontological Heritage Impact Assessment for Sewerage Upgrade in Alicedale, Eastern Cape

Palaeontological Heritage Impact assessment for Sewerage upgrade in Alicedale, Eastern Cape

Prepared for: Gibb Engineering

Port Elizabeth 2nd Floor, Greyville House, Cnr Greyville & Cape Rd, Greenacres, Port Elizabeth 6001

Compiled by: Dr Robert Gess

Rob Gess Consulting, Box 40, Bathurst, 6166

Research Associate of the Albany Museum, Somerset Street, Grahamstown

[email protected]

November 2016

Contents

Executive Summary ...... 3 Background ...... 4 Geology ...... 5 Site visit ...... 9 Conclusions and Recommendations ...... 14 References ...... 15

List of Figures

Figure 1: Map showing proposed new sewer lines (red) superimposed on topographic and geological data...... 7 Figure 2: Stratigraphic column of the Cape Supergroup with strata to be impacted by the development indicated in red...... 8 Figure 3: Sewerage gravity feed manhole point 1 (Fig. 1)...... 10 Figure 4: Yellow weathered Kweekvlei Formation mudstone at point 2 (Fig. 1)...... 10 Figure 5: Weathered Kweekvlei Formation black shale and more weathered yellowish shale in the road-cutting approaching the Bushman’s River at point 4 (Fig. 1)...... 11 Figure 6: Thick alluvium obscuring bedrock at the vegetable growing project in the valley at point 3 (Fig. 1)...... 11 Figure 7: Alluvium levelled for street at point 6 (Fig.1)...... 12 Figure 8: Levelled and paced street obscuring bedrock at point 5 (Fig 1)...... 12 Figure 9: Ridge comprising upwardly folded Witpoort Formation quartzites to the south of Alicedale, viewed from point 7 (Fig. 1)...... 13 Figure 10: Carbonaceous mudstones interbedded quartzites within the top of the Witpoort formation at point 8 (Fig. 1)...... 13

Executive Summary

Gibb (Pty) Ltd was appointed by Makana Local Municipality to undertake a Basic Assessment and Water Use License Application for the proposed upgrade to sewerage infrastructure in Alicedale, Eastern Cape.

Gibb subcontracted Rob Gess Consulting to conduct a Palaeontological Heritage Impact Assessment for the project to be included in the Basic Assessment Report and inform conservation and mitigation requirements for any Paleontological finds during the PIA or during construction phase.

The literature review indicated that the area intended for development overlies strata of the Witteberg Group (Cape Supergroup), more specifically the Witpoort Formation (Witteberg Group, Cape Supergroup) and the Kweekvlei Formation (Lake Mentz Subgroup, Cape Supergroup).

The Witpoort Formation (Witteberg Group, Cape Supergroup) strata belong to the Late Devonian (Famennian) and the black shale lenses of this rock, particularly in the vicinity of Grahamstown have proved remarkably fossiliferous. Shale lenses in the Grahamstown area have yielded at least 20 important fish fossils as well as dozens of plant and algal taxa.. In addition, remains of giant eurypterids and other arthropods such as scorpions have been found in. Lag deposits of bone have not, as yet, been discovered in this region, but may be expected.

The fine muddy sediments of the Kweekvlei Formation (Lake Mentz Subgroup, Witteberg Group) are increasingly silty upwards but have, as yet, with the exception of a single shark spine, yielded only plant fragments and sparse ichnofossils.

The majority of the area is underlain by alluvium and weathered mudstone of the Kweekvlei Formation, trenching into which is unlikely to disturb fossiliferous material. There is a potential that fossils could be found during excavations into areas where fresh mudstones on the Kweekvlei Formation are exposed at the surface;on the hill slope in the south east of the area, and approaching the east bank of the Bushmans River. However, the Kweekvlei Formationis not known for being palaeontologically rich.

Far more likely to be of palaeontological importance would be exposure of any black shales exposed within the quartzites of the Witpoort Formation. These are however unlikely to be exposed as the Witpoort Formation only outcrops in the extreme south west of the area and is unlikely to be excavated into to any depth.

It is therefore recommended that where fresh (black) shale of the Kweeklei Formation is exposed trenches should be left open. These sections can then be collectively inspected by a palaeontologist before closure. Should the quartzites of the Witpoort Formation be cut into and black shale of the Witpoort Formation be exposed a palaeontologist should immediately be contacted to evaluate the occurrence. If any suspected fossils are encountered during the project a palaeontologist should immediately be contacted. The project can commence as no prohibitions have been identified from the paleontological study.

Background

Alicedale Town falls in Makana Local Municipality and Sarah Baartman District Municipality in the Eastern Cape. It is located approximately 110 km north east from Port Elizabeth and 54km West of Grahamstown. The nearest neighbouring towns are Paterson (28 km via the N10) and Riebeck East (31 km via the R400).

Currently, sewage from Alicedale Town discharges into various conservancy tanks around the town. There is one main conservancy tank opposite the water treatment works. The sewage is transported with tankers from the conservancy tanks to a gravity main North of Kwanonzwakazi which gravitates down to the recently built wastewater treatment works. This an outdated system which is cost intensive and relies heavily on onsite personnel to transport the sewage before it overflows. It also poses health risk as sewage spills, from the tankers that are transporting them.

GIBB (Pty) Ltd was appointed by Makana Local Municipality to assess the existing sewerage infrastructure and undertake a concept design process to consider various options of design for upgrades to the current sewerage system. An environmental screening exercise and consultation with the Department of Economic Development, Environmental Affairs and Tourism was done resulting in a decision by the competent authority that a Basic Assessment Process should be undertaken to assess the potential impacts of the proposed sewerage upgrades project.

This project aims to provide the town of Alicedale with a waterborne sanitation system which will allow the sewage to be drained via a reticulation system to a point where it would be pumped up to the existing gravity main. It will then be directed via the gravity main to the existing wastewater treatment works.

It is proposed that the sewage should flow from houses via a waterborne reticulation system to a pump station on the Western side of Alicedale. The pump station will then pump the sewage along a rising main that crosses the Bushman’s River at the bridge and ties into an existing gravity line north of Kwanonzwakazi, where the sewage would gravitate down to the existing treatment works. New reticulation will be situated within the road reserve.

The site visit indicated that the boundary between the Witpoort and Kweekvlei Formations lies slightly further south than it is portrayed on the geological map and the majority of the area is therefore situated over strata belonging to the Kweekvlei Formation. Nonetheless outcrops of the Kweekvlei Formation are rare along the pipeline route and were only encountered a little to the west of the sewerage gravity feed area (Fig. 3) in the south east of the area (Fig. 4) and approaching the bridge over the Bushmans River (Fig. 5). Within the valley itself a thick layer of alluvium overlies much of the bedrock (Fig. 6). In addition much of the route follows areas that have been levelled for streets (Fig. 7) and/or paved over (Fig. 8). These areas are probably largely underlain by further alluvium.

Only in the south west of the area, near the proposed pumping stations, are outcrops of the Witpoort Formation visible (Fig. 9). In the adjacent railway cutting these uppermost Witpoort Formation strata are seen to continue potentially fossiliferous mudstone interbeds, likely to be of a similar age to those of the Waterloo Farm lagertätten (Fig. 10).

Geology

The area intended for development overlies strata of the Witteberg Group (Cape Supergroup), more specifically the Witpoort Formation (Witteberg Group, Cape Supergroup) and the Kweekvlei Formation (Lake Mentz Subgroup, Cape Supergroup) (Fig.1). These two formations correlate with the latest Devonian Famennian age, and the earliest Carboniferous Tournasian age respectively. They are separated by one on the Earth’s most extreme extinction events, the EDME (end-Devonian Mass Extinction event) or Hangenberg Extinction event.

Cape Supergroup rocks represent sediments deposited in the Agulhas Sea, which had opened to the south of the current southern African landmass, in response to early rifting between Africa and South America during the Ordivician. Around the time of the Devonian/Carboniferous transition it was situated within 15 degrees of the South Pole. The Witteberg Group is the uppermost of three subdivisions of the Cape Supergroup (Fig. 2) and is secondarily folded throughout the district into a series of giant corrugations.

The Witpoort Formation is characterised by thick light coloured quartzites, consolidated from mature quartz sand accumulated along a sandy shoreline, under linear barrier-island conditions. These form distinctive, resilient ridges that may be traced along the full length of the Cape Fold Belt. Thin black shale layers and lenses within this formation include deposits derived from muds carried by river systems into coastal estuarine lagoons. Hills to the south of Alicedale are comprised of a giant upward fold (anticline) of Witpoort Formation strata. A sudden rise in relative sea level, corresponding to the Tournasion transgression at the end of the Devonian Period, terminated the sandy shoreline deposition of the Witpoort Formation, which is overlain by the fine dark muddy sediments of the Kweekvlei Formation. These shales generally weather to a pale yellowish colour and form lowered topography such as the Alicedale valley, couched between two Witpoort Formation ridges.

Figure 1: Map showing proposed new sewer lines (red) superimposed on topographic and geological data.

Figure 2: Stratigraphic column of the Cape Supergroup with strata to be impacted by the development indicated in red.

Palaeontology

The stratigraphically lowest Witteberg Group strata present belong to the Late Devonian (Famennian) Witpoort Formation (Witteberg Group, Cape Supergroup) This largely quatzitic unit represents mature sandy strata deposited along a linear barrier island type coast. Particularly around Grahamstown black shale lenses, interpreted as estuarine deposits deposited during brief transgressive events, have proved remarkably fossiliferous. A series of lenses at Waterloo Farm, to the south of Grahamstown, have provided southern Africa’s most important Late Devonian locality, which has yielded at least 20 taxa of fossil fish (including jawless fish (Agnatha), armoured fish (Placodermi), spiny sharks (Acanthodii), sharks (Chondrichthyes), ray finned fish (Actinopterygii) and lobe finned fishes (Sarcopterygii) including Coelacanths (Actinistia), lungfish (Dipnoi) and Osteolepiformes. Dozens of plant and algal taxa have been collected, as well as remains of giant eurypterids and other arthropods such as scorpions. These latter fossils represent the oldest known terrestrial animal remains from Gondwana. Abundant trace fossils have also been collected. The top of the Witpoort Formation coincides with the end of the Devonian and is similar in age to the end- Devonian extinction event. Witpoort Formation quartzites have yielded a range of plant stem taxa and trace fossils. Lag deposits of bone have not, as yet, been discovered, but may be expected.

The overlying formations of the Lake Mentz Subgroup, the Kweekvlei Formation, Floriskraal Formation and Waaipoort Formation (Fig.2) are all Early Carboniferous in age, the 360 myo Devonian-Carboniferous boundary (and the Hangenberg Extinction event) having been passed at the top of the Witpoort Formation.

The fine muddy sediments of the Kweekvlei Formation (Lake Mentz Subgroup, Witteberg Group) are increasingly silty upwards but have, as yet, yielded only plant fragments and sparse ichnofossils. A single shark fin-spine has been recorded from a mud- chip lag deposit above the base of the Kweekvlei Formation on Hilton Farm, north of Grahamstown (pers. obs.).

Site visit

A thorough site visit was conducted by Rob Gess Consulting on the 12th November 2016. It was concluded that the boundary between the Witpoort and Kweekvlei Formations lies slightly further south than it is portrayed on the geological map and the majority of the area is therefore situated over strata belonging to the Kweekvlei Formation.

Nonetheless outcrops of the Kweekvlei Formation are rare along the pipeline route and were only encountered a little to the west of the sewerage gravity feed area (Fig. 3) in the south east of the area (Fig. 4) and approaching the bridge over the Bushmans River (Fig. 5) Within the valley itself a thick layer of alluvium overlies much of the bedrock (Fig. 6). In addition much of the route follows areas that have been levelled for streets (Fig. 7) and/or paved over (Fig. 8). These areas are probably largely underlain by further alluvium.

Figure 3: Sewerage gravity feed manhole point 1 (Fig. 1).

Figure 4: Yellow weathered Kweekvlei Formation mudstone at point 2 (Fig. 1).

Figure 5: Weathered Kweekvlei Formation black shale and more weathered yellowish shale in the road-cutting approaching the Bushman’s River at point 4 (Fig. 1).

Figure 6: Thick alluvium obscuring bedrock at the vegetable growing project in the valley at point 3 (Fig. 1).

Figure 7: Alluvium levelled for street at point 6 (Fig.1).

Figure 8: Levelled and paved street obscuring bedrock at point 5 (Fig 1).

Figure 9: Ridge comprising upwardly folded Witpoort Formation quartzites to the south of Alicedale, viewed from point 7 (Fig. 1).

Figure 10: Carbonaceous mudstones interbedded quartzites within the top of the Witpoort formation at point 8 (Fig. 1).

Conclusions and Recommendations

The majority of the area is underlain by alluvium and weathered mudstone of the Kweekvlei Formation. Fresher material of this formation is exposed on the hill slope in the south east of the area, and approaching the east bank of the Bushmans River. These strata are not known for being palaeontologically rich, but consequently the discovery of any fossils from this horizon would give important insights into the recovery phase after the End Devonian Mass Extinction event.

It is therefore recommended that:

1) Where fresh (black) shale of the Kweeklei Formation is exposed trenches should be left open. These sections can then be collectively inspected by a palaeontologist before closure.

2) Should the quartzites of the Witpoort Formation be cut into and black shale of the Witpoort Formation be exposed a palaeontologist should immediately be contacted to evaluate the occurrence.

3) Should any suspected fossils be encountered elsewhere during the project a palaeontologist should immediately be contacted.

The project can proceed as no prohibitions have been identified from the paleontological study.

References

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Gess, R.W. and Hiller, N. (1995a). A preliminary catalogue of fossil algal, plant, arthropod, and fish remains from a Late Devonian black shale near Grahamstown, South Africa. Annals of the Cape Provincial Museums (Natural History) 19: 225-304.

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Gess, R.W. (2016). Vertebrate biostratigraphy of the Witteberg Group and the Devonian Carboniferous boundary in South Africa, in eds. Linol, B. and de Wit, M. J., The Origin and Evolution of the Cape Mountains and Karoo Basin. Springer, Regional Geology Reviews. pp 131-140. Doi: 10.1007/978-3-319-40859-0_13

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