DOCSLIB.ORG

A Keystone of the Cape Fold Belt

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Keystone of the Cape Fold Belt Kaaimansgat Inlier: A Keystone of the Cape Fold Belt Geological Society of South Africa Western Cape Branch End-of-Year Field Trip 29 November 2008 Scott Maclennan and Christie Rowe Department of Geological Sciences, University of Cape Town Meeting place: Spar parking lot, Main Road Villiersdorp 10am Saturday 29 November Directions: From Cape Town, take the N2 east across Cape Flats and up to Sir Lowry’s Pass. After the pass, turn on the R321 toward Villiersdorp/ Theewaterskloof Dam. The R321 becomes Main Rd, Villersdorp and the Spar is on your left as you enter town. Abstract: The geology of the Western Cape can be summarized in a few sentences. A Neoproterozoic marine sedimentary sequence was deformed in the Saldanian “orogeny”, intruded by the Cambrian Cape Granite Suite, exhumed and planed off, then buried under the Paleozoic Cape Basin, which was subsequently deformed by the ~ Permian Cape Orogeny. However, the details of the depositional environments and the tectonic setting of these deformations are still poorly understood. Understanding of the Saldanian deformation is hindered by poor exposure and structural overprinting of the later orogeny. According to plate tectonic reconstructions, the Cape region would have been interior to the Gondwana supercontinent during Permian time – not near a collisional margin as is the typical setting for fold-thrust belts. Finally, the geometry of the Cape Fold Belt is unique in that it makes a near 90° corner in the syntaxis region, where NNW-SSE trends of the western limb and the E-W trends of the southern limb meet. The Kaaimansgat Inlier, a small valley in the heart of the syntaxis region, is an excellent natural laboratory to explore these puzzles. Maclennan (2008) made a detailed structural and lithostratigraphic study of the Kaaimansgat valley of rocks below and above the unconformity. Unique characteristics of the Cape Fold Belt The Cape Fold Belt overprints an earlier fold belt represented by deformation of the Malmesbury Group sediments at ~550Ma – the Saldanian Orogeny. Partly due to poor outcrop, the structural history of the Malmesbury Group is poorly understood. Structures observed in the Malmesbury rocks today are the cumulative effect of two orogenies: the Saldanian and the Cape Orogenies. Figure from Curtis (2001). Figure 14. Tectonostratigraphic correlation diagram for segments of the Gondwanian fold belt. The spatial arrangement of the columns reflects the paleogeographic position (as shown in Fig. 15) of these once contiguous geological provinces along the paleo-Pacific margin of Gondwana. Tectonostratigraphy of Pensacola Mountains is after Storey et al. (1996) ; pre-Cape Supergroup data are established after Barnett et al. (1997) and Armstrong et al. (1998). SPF—Schoemans Port Formation, KSG—Kansa Subgroup. The Kaaimansgat locality has relatively good exposure of Malmesbury rocks, and perfect exposure of the unconformity surface. Folding or faulting of the unconformity surface and basal Table Mountain Group can been taken to represent the local effects of the Cape Orogeny. Maclennan (2008) mapped and defined the geometry of the large-scale Cape-age dome in Kaaimansgat and back rotated Malmesbury structures to attempt to understand Saldanian structure in the area. In addition, he measured deformed reduction spots in the Malmesbury phyllites and was able to establish the orientation of the finite strain ellipse at three locations within the area. Gondwana re-assembly (Figure 1 from (Gaucher et al., 2004)) showing older basement rocks which were structurally or metamorphically overprinted during Pan-African orogenies (gray hatching) and sedimentary deposits from Pan-African time (black). During the time of folding, the position of the CFB was far inside the Gondwana super continent – not at the margin where fold belts commonly form during plate collisions. Most mountain belts today form at the edges of continents where two plates are directly in contact with one another, and where thinner, younger or weaker crust is more deformable than the interior cratons. According to most plate reconstructions from Permian time, the Cape Fold Belt was not at an active collisional margin but rather well inside the continent of Gondwana. It is therefore interesting to ask whether the Cape Orogeny deformed only the Paleozoic basin sediments (Cape Super Group) which were isolated from the basement by a structural detachment, or whether the middle and lower crust was also significantly strained. As of yet the magnitude of Cape-age deformation of the Malmesbury Group is not well understood. The two arms of the Cape Fold belt meet at a sharp corner: Syntaxis (n) a map-scale curve in a mountain belt. This raises the question of whether one long fold belt was folded or whether folding in two orientations occurred simultaneously or one after another. Detailed structural mapping and fold characterization by de Beer (1995) constitutes the only study that we know of which uses structural field data to address the question. Coenie showed that farther upsection in the Bokkeveld and Witteberg Groups the fold geometries were formed by simultaneous shortening in two directions (constriction). However, the model was not as well fit by the deformation in the Table Mountain Group sediments. This may indicate a gradation from thick-skinned deformation in the hinterland toward thin skinned deformation in the foreland of the Cape Fold Belt. Figure 1 from de Beer (1995). Stop 1. Overlook The Peninsula Formation quartzites frame Kaaimansgat valley. The unconformity is located just below the outcrop of this quartzite. The Malmesbury Group metasediments outcrop in the valley floor, with the most resistant lithologies forming topographic highs. The Peninsula Formation is folded into a 030/210 orientated doubly plunging anticline. The eastern limb diverges from this trend, being closer to an easterly orientation. The overall structure of the Malmesbury Group is interpretated as being a large anticline that is S shaped, or curvilinear. This was interpreted from a gradual change in bedding orientation from NW-SE in the SE of the valley through N-S in the centre around to roughly E-W in the upper NE corner of the valley. Restoring Malmesbury Group structures to their pre-Cape orogeny orientation reveals that the structures were rotated during Cape folding into more of a NE trend, in alignment with the general trend of the syntaxis Stop 2. “Purple phyllite” and reduction spots in the Malmesbury Group A purple phyllite outcrops along the road cut. A normal fault divides these rocks from the basal beds of the Peninsula Formation, which consist of interbedded mudstones and sandstones. This fault is roughly N orientated and dips steeply to the east. A fine grained purple fault gouge occurs within the normal fault plane. In the purple phyllite dark macroscopic grains of chloritoid are visible. This unit also contains small green ellipses, otherwise known as reduction spots and record the strain experienced by these rocks. This is because they are interpreted as starting off as perfect spheres and are the result of interactions of reducing and oxidizing fluids. Reduction spots are also present on the western limb of the Kaaimansgat Valley. Reduction spots on the western limb record ±60% shortening while the eastern limb shows ±50% shortening. Stop 3. Lithologic variation in the Malmesbury Group; and TMG basal conglomerates – Lunch Stop. Along the northern slopes of Kaaimansgat a thick conglomerate overlies an angular unconformity with the Malmesbury Group. It has a strong cleavage at its base and contains a variety of clasts. This grades into to the Peninsula Formation quartzites that contain only rounded vein quartz pebbles. The road cuts along the road up to Eagles Nest expose the interbedded sandstones and shales of the Malmesbury Group. Stop 4. Granitic intrusion boundary A large granitic intrusion is present all along the western side of Kaaimansgat Valley. For the most part it is almost completely altered, the only surviving primary mineral is quartz. Near the centre of the outcrop there is a body of much finer grained felsic material that has a strong cleavage. This was interpreted as being a heavily sheared part of the granite batholiths. Stop 5. Faulted unconformity, Graafwater Formation (or equivalent) and interesting MG lithologies. There is evidence for shearing along the unconformity and the thinly bedded Graafwater Formation above. This is evident in S-C fabrics in shale lenses and thinly bedded sandstones along and slightly above the unconformity. This movement always has a sense of shear towards the centre of the valley and so is interpreted as a result of layer parallel shearing during the Cape age folding. The observed shear senses do not indicate a large amount of displacement along the unconformity and the Cape orogeny was predominantly thick-skinned at this locality. Interbedded grits and shales are exposed here as well as the steeply south dipping contact with the Malmesbury sandstones Stop 6. (optional) Bedded sandstones in the Malmesbury, bedding cleavage intersections Bedding is hard to find in the Malmesbury Group sediments here owing to their metamorphic grade but the course sandstones contained a few localities where cross and graded bedding outcrop allowing for the determination of younging directions as well. Intersection lineations between bedding and cleavage show changing plunge directions. This was interpreted as being evidence for undulations of the major fold structure in the vertical and horizontal planes. Multiple deformation events are required for the formation of the structures preserved in the Malmesbury Group, a proportion of which is attributable to the later Cape orogeny. References Cited: Belcher, R.W. and Kisters, A.F.M., 2003. Lithostratigraphic correlations in the western branch of the Pan-African Saldania belt, South Africa: the Malmesbury Group revisited. South African Journal of Geology, 106: 327- 342. Curtis, M.L., 2001. Tectonic history of the Ellsworth Mountains, West Antarctica: Reconciling a Gondwana enigma. Geological Society of America Bulletin, 113(7): 939-958.
Load more

Recommended publications
  • A. the Cape Province Fold Belt
    SECTION II-A BRIEF SURVEY OF THE GEOLOGY OF THE CAPE SYSTEM A. THE CAPE PROVINCE FOLD BELT 1. Distribution and Folding The main occurrence of the Cape System in South Africa is confined to the Cape Province where a threefold division is recognised, namely the Table Mountain Series, or T.M.S., the Bokkeveld Series and, at the top, the Witte­ berg Series. The rocks occur along the western and southern margins of the sub-continent (see map on p. 10) where they lie with marked unconformity on older formations with granite intrusives. In the south and southwest, the Cape System dips beneath and is overlain conformably by the tillite of the Dwyka Series which forms the base of the Karroo System, but along the 'western margin the tillite when followed northwards, gradually overlaps the variolls series of the Cape System and finally lies directly on pre-Cape rocks. The whole system has been folded with a general N-S strik on the West and more intensely with a general E-W strike in the south with especially complex crumpling in the SW in the vicinity of Ceres and the Hex River Mountains, where the two fold axes Ineet. The folds in the south are frequently overturned, and are sometimes isoclinal. Usually lateral folds display a fairly teep pitch with the result that they ar hortened, outcrops occur en echelon and a particular horizon may reappear a nwnber of times in a traverse acros the ),stem. Pressure .has resulted in the alteration of organic matter to graphite in many cases and the cOlnplete de truction of micro flora.
    [Show full text]
  • The Origin and Early Evolution of Dinosaurs
    Biol. Rev. (2010), 85, pp. 55–110. 55 doi:10.1111/j.1469-185X.2009.00094.x The origin and early evolution of dinosaurs Max C. Langer1∗,MartinD.Ezcurra2, Jonathas S. Bittencourt1 and Fernando E. Novas2,3 1Departamento de Biologia, FFCLRP, Universidade de S˜ao Paulo; Av. Bandeirantes 3900, Ribeir˜ao Preto-SP, Brazil 2Laboratorio de Anatomia Comparada y Evoluci´on de los Vertebrados, Museo Argentino de Ciencias Naturales ‘‘Bernardino Rivadavia’’, Avda. Angel Gallardo 470, Cdad. de Buenos Aires, Argentina 3CONICET (Consejo Nacional de Investigaciones Cient´ıficas y T´ecnicas); Avda. Rivadavia 1917 - Cdad. de Buenos Aires, Argentina (Received 28 November 2008; revised 09 July 2009; accepted 14 July 2009) ABSTRACT The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis,andPanphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as ‘‘all descendants of the most recent common ancestor of birds and Triceratops’’.
    [Show full text]
  • The Role of Fossils in Interpreting the Development of the Karoo Basin
    Palaeon!. afr., 33,41-54 (1997) THE ROLE OF FOSSILS IN INTERPRETING THE DEVELOPMENT OF THE KAROO BASIN by P. J. Hancox· & B. S. Rubidge2 IGeology Department, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa 2Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa ABSTRACT The Permo-Carboniferous to Jurassic aged rocks oft1:J.e main Karoo Basin ofSouth Africa are world renowned for the wealth of synapsid reptile and early dinosaur fossils, which have allowed a ten-fold biostratigraphic subdivision ofthe Karoo Supergroup to be erected. The role offossils in interpreting the development of the Karoo Basin is not, however, restricted to biostratigraphic studies. Recent integrated sedimentological and palaeontological studies have helped in more precisely defming a number of problematical formational contacts within the Karoo Supergroup, as well as enhancing palaeoenvironmental reconstructions, and basin development models. KEYWORDS: Karoo Basin, Biostratigraphy, Palaeoenvironment, Basin Development. INTRODUCTION Invertebrate remains are important as indicators of The main Karoo Basin of South Africa preserves a facies genesis, including water temperature and salinity, retro-arc foreland basin fill (Cole 1992) deposited in as age indicators, and for their biostratigraphic potential. front of the actively rising Cape Fold Belt (CFB) in Fossil fish are relatively rare in the Karoo Supergroup, southwestern Gondwana. It is the deepest and but where present are useful indicators of gross stratigraphically most complete of several depositories palaeoenvironments (e.g. Keyser 1966) and also have of Permo-Carboniferous to Jurassic age in southern biostratigraphic potential (Jubb 1973; Bender et al. Africa and reflects changing depositional environments 1991).
    [Show full text]
  • The Stratigraphy and Structure of the Kommadagga Subgroup and Contiguous Rocks
    THE STRATIGRAPHY AND STRUCTURE OF THE KOMMADAGGA SUBGROUP AND CONTIGUOUS ROCKS by ROGER SWART B.Sc . (Hons) Thesis presented in fulfilment of the requirements for the degree of Master of Science in the Department of Geology, Rhodes University ,Grahamstown. January 1982 ABSTRACT The Lake Mentz and Kommadagga Subgroups were deposited i n a marine environment and are characterised by a heterogeneous sequence of sediments, which range in grain size from clays to grits . During the first phase of deposition the Kwee~ vlei Shale and Floriskraal Formations were deposited in a prograding shoreline environment, whereas the succeeding Waaipoort Shale Formation is interpreted as represnting a reworked shoreline. The final phase of deposition of the Cape Supergroup was a regressive one in which the Kommadagga Subgroup wa s fo rmed. The coa rs eni ng upward cycle of thi s subgroup represents a deltaic deposit. A significant time gap appears to exist before the deposition of the glacial-marine Dwyka Tillite Formation. Structurally, the area was subjected to deformation by buckle folding at about 250 Ma into a series of folds with southward dipping axial planes. Only one phase of deformation is recognised in the study area . A decrease in pore space, mineral overgrowths,formation of silica and calcite cements and development of aut~igenic minerals such as opal, stilpnomelane; analcite, prehnite, muscovite and various clay minerals are the characteristic diagenetic features of the sediments.The mineralogical evidence suggests that the maximum temperature
    [Show full text]
  • Revealing the Beattie Magnetic Anomaly and the Anatomy Of
    11th SAGA Biennial Technical Meeting and Exhibition Swaziland, 16 - 18 September 2009, pages 490 - 499 Revealing the Beattie Magnetic Anomaly and the anatomy of the crust of southernmost Africa: Geophysics and deep sub- surface geology where the Cape Fold Belt and Karroo Basin meet A. S. Lindeque1,2,3, M.J. de Wit4 1. Now at Alfred Wegener Institute for Polar and Marine Research, Geophysics, Building D3280, Am Alten Hafen 26, 27568 Bremerhaven, Germany, [email protected] 2. Council for Geoscience, Western Cape, P.O. Box 572, Bellville 7535, Cape Town, South Africa 3. GeoForschungsZentrum Potsdam, Section 2.2, Telegrafenberg, 14473 Potsdam, Germany 4. AEON - Africa Earth Observatory Network and Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa, [email protected] ABSTRACT The deep crust of the southernmost margin of Africa contains unresolved tectonic features such as the Paleozoic Cape Fold Belt (CFB), the Paleozoic-Mesozoic Karroo Basin and the largest terrestrial magnetic anomaly, the Beattie Magnetic Anomaly (BMA). Without resolving these structures, our understanding of the evolution of the southern margin will be incomplete and limited. Under the auspices of the Inkaba yeAfrica framework, several geophysical datasets were acquired from 2004 to 2007, along two transects across the margin and its unique tectonic features. This research presents a tectonic model and crustal geometry, at the centre 100 km of the western transect. The model is derived from the joint interpretation of: surface geology, aeromagnetic data, nearby deep boreholes, teleseismic receiver functions, impedance spectroscopy measurements on borehole samples, near vertical reflection seismic data (NVR), shallow P- and S-wave velocity data, wide angle refraction data and magnetotelluric data.
    [Show full text]
  • Proceedings of the 18Th Biennial Conference of the Palaeontological Society of Southern Africa Johannesburg, 11–14 July 2014
    Proceedings of the 18th Biennial Conference of the Palaeontological Society of Southern Africa Johannesburg, 11–14 July 2014 Table of Contents Letter of Welcome· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 63 Programme · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 64 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 66 Hand, K.P., Bringing Two Worlds Together: How Earth’s Past and Present Help Us Search for Life on Other Planets · · · · · · · 66 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 67 Erwin, D.H., Major Evolutionary Transitions in Early Life: A Public Goods Approach · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 67 Lelliott, A.D., A Survey of Visitors’ Experiences of Human Origins at the Cradle of Humankind, South Africa· · · · · · · · · · · · · · 68 Looy, C., The End-Permian Biotic Crisis: Why Plants Matter · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 69 Reed, K., Hominin Evolution and Habitat: The Importance of Analytical Scale · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
    [Show full text]
  • Remagnetizations in Late Permian and Early Triassic Rocks from Southern Africa and Their Implications for Pangeareconstructions
    412 Earth and Planetary Science Letters, 79 (1986) 412-418 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 151 Remagnetizations in Late Permian and Early Triassic rocks from southern Africa and their implications for Pangea reconstructions Martha M. Ballard ‘, Rob Van der Voo * and I.W. HZlbich 2 ’ Department of Geological Sciences, University of Michigan, Am Arbor, MI 48109 (U.S.A.) ’ Department of Geology, University of Stellenbosch, Stellenbosclr (Republic of South Africa) Received March 31,1985; revised version received June 24, 1986 -A paleomagnetic study of late Paleozoic and early Mesozoic sedimentary rocks from southern Africa suggests wide-spread remagnetization of these rocks. Samples of the Mofdiahogolo Formation in Botswana and of the Lower Beaufort Group in South Africa were treated using thermal, alternating field and chemical demagnetization. The Mofdiahogolo redbeds show a univectoral decay of the remanence revealing a characteristic direction of D = 340°, I = - 58O, k = 64, a9s = 12O. The Lower Beaufort sandstones, using thermal and alternating field demagnetization, show a very similar direction of D = 337O, I = -63”, k = 91, ags = 6O. A fold test on the Beaufort rocks is negative indicating that this magnetization is secondary and acquired after the Permo-Triassic Cape Belt folding event. Previous studies have reported similar directions in the Upper Beaufort redbeds as well as in the Kenyan Maji ya Chumvi Formation of Early Triassic age. The poles of these studies have been used in testing the validity of the various Pangea reconstructions for the Late Permian and the Early Triassic. Our results suggest that these poles may also be based on remagnetized data and that their use to document the position of Gondwana in Pangea reconstructions should be treated with caution.
    [Show full text]
  • Introduction to the Tetrapod Biozonation of the Karoo Supergroup
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/342446203 Introduction to the tetrapod biozonation of the Karoo Supergroup Article in South African Journal of Geology · June 2020 DOI: 10.25131/sajg.123.0009 CITATIONS READS 0 50 4 authors, including: Bruce S Rubidge Michael O. Day University of the Witwatersrand Natural History Museum, London 244 PUBLICATIONS 5,724 CITATIONS 45 PUBLICATIONS 385 CITATIONS SEE PROFILE SEE PROFILE Jennifer Botha National Museum Bloemfontein 82 PUBLICATIONS 2,162 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Permo-Triassic Mass Extinction View project Permo-Triassic palaeoecology of southern Africa View project All content following this page was uploaded by Michael O. Day on 24 August 2020. The user has requested enhancement of the downloaded file. R.M.H. SMITH, B.S. RUBIDGE, M.O. DAY AND J. BOTHA Introduction to the tetrapod biozonation of the Karoo Supergroup R.M.H. Smith Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, 2050 South Africa Karoo Palaeontology, Iziko South African Museum, P.O. Box 61, Cape Town, 8000, South Africa e-mail: [email protected] B.S. Rubidge Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa e-mail: [email protected] M.O. Day Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa e-mail: [email protected] J. Botha National Museum, P.O. Box 266, Bloemfontein, 9300, South Africa Department of Zoology and Entomology, University of the Free State, 9300, South Africa e-mail: [email protected] © 2020 Geological Society of South Africa.
    [Show full text]
  • Seismic Hazard in South Africa
    Western Cape Unit P.O. Box 572 Bellville 7535 SOUTH AFRICA c/o Oos and Reed Streets Bellville Cape Town Reception: +27 (0) 21 946 6700 Fax: +27 (0) 21 946 4190 Seismic Hazard in South Africa M. Brandt Council for Geoscience Report number: 2011-0061 © Copyright 2011. Council for Geoscience 1 Contents Contents..................................................................................................................................................2 Figures.....................................................................................................................................................2 Tables......................................................................................................................................................3 1 General seismicity...........................................................................................................................4 2 African Regional seismicity .............................................................................................................5 3 Seismic Hazard Maps for Southern Africa by Fernandez and Du Plessis........................................7 4 South African Seismograph Network and Database.....................................................................11 4.1 Limitations and the need for updating the SHA maps ........................................................11 5 Identification of zones and hot spots ...........................................................................................15 5.1 Discussion of the
    [Show full text]
  • Addo Elephant National Park – Geology
    Addo Elephant National Park – Geology Introduction Before we start, one must remember that we live on a dynamic planet, which is permanently changing and evolving. The earth has a radius of about 6 300km and is covered by a 40km thick crust. The surface crust is continuously being driven by convection currents in the underlying mantle. This causes the crustal plates (continents and oceans) to move relative to each other, a process called “continental drift”. Crustal plates can drift (float) from the warmer tropics to the colder pole regions, all the time changing the way in which a landscape evolves. The combination of earth processes and climatic conditions has a significant impact on the final landscape appearance. The oldest rocks – Peninsula formation quartzitic sandstone The easiest way to describe the geological evolution of the Park is to start with the oldest rocks and work our way towards the present. Our story begins when Africa was joined to a number of other continents to form a super continent called “Pangea”. We (South Africa) were stuck in the middle of this land mass and our landscape was, therefore, very different to what one sees today. The oldest rocks encountered in the Park occur as small islands in Algoa Bay. The Bird Island complex comprises Black Rock, Stag, Seal and Bird Islands and occurs about 10 km south of the Woody Cape cliffs. These rocky islands are made up of quartzitic sandstone of the Peninsula Formation, which forms part of the Table Mountain Group, which in turn forms part of the Cape Supergroup.
    [Show full text]
  • Palaeontological Heritage of the Eastern Cape
    PALAEONTOLOGICAL HERITAGE OF THE EASTERN CAPE John Almond Natura Viva cc, CAPE TOWN Billy de Klerk Albany Museum, GRAHAMSTOWN Robert Gess Bernard Price Institute (Palaeontology), Wits University, JOHANNESBURG The Eastern Cape is the second largest province in South Africa, comprising some 14% of the area of the RSA. The population is about seven million. The province is renowned for its living biodiversity and it also boasts a rich fossil record stretching back some 560 million years. The majority of the provincial area is underlain by shallow marine, coastal and terrestrial sediments of Phanerozoic ( ie post- Precambrian) age that are known to contain fossils of some sort, or are potentially fossiliferous (See accompanying simplified geological map and stratigraphic chart, both produced by the Council for Geoscience, Pretoria). Among the palaeontological highlights of the Eastern Cape are: • diverse, high-latitude lacustrine to lagoonal biotas from the Late Devonian – Early Carboniferous Witteberg Group ( c. 360-345 Ma = million years ago). These include a variety of fish and vascular plants as well as rarer arthropods. • fish, reptiles and therapsids (“mammal-like reptiles”) from the Late Permian to Early Triassic Beaufort Group ( c. 266-250 Ma) • extraordinarily rich fossil floras from the Late Triassic Molteno Formation ( c. 220 Ma) • a range of Early Cretaceous dinosaurs and plant fossils from the Kirkwood Formation ( c. 135 Ma) • rich shelly marine faunas from the Early Cretaceous Sundays River Formation ( c. 135 Ma) • important coastal marine fossil biotas of the Algoa Group ranging from Eocene to Recent in age (50 to 0 Ma). Important fossil collections from the Eastern Cape are housed at several South African Institutions, such as: Iziko: South African Museum (Cape Town), Albany Museum (Grahamstown), Port Elizabeth Museum (Port Elizabeth), Bernard Price Institute for Palaeontology, Wits.
    [Show full text]
  • New Late Permian Tectonic Model for South Africa's Karoo Basin
    www.nature.com/scientificreports OPEN New Late Permian tectonic model for South Africa’s Karoo Basin: foreland tectonics and climate Received: 12 December 2016 Accepted: 1 August 2017 change before the end-Permian Published: xx xx xxxx crisis Pia A. Viglietti 1,2, Bruce S. Rubidge1,2 & Roger M. H. Smith1,2,3 Late Permian Karoo Basin tectonics in South Africa are refected as two fning-upward megacycles in the Balfour and upper Teekloof formations. Foreland tectonics are used to explain the cyclic nature and distribution of sedimentation, caused by phases of loading and unloading in the southern source areas adjacent to the basin. New data supports this model, and identifes potential climatic efects on the tectonic regime. Diachronous second-order subaerial unconformities (SU) are identifed at the base and top of the Balfour Formation. One third-order SU identifed coincides with a faunal turnover which could be related to the Permo-Triassic mass extinction (PTME). The SU are traced, for the frst time, to the western portion of the basin (upper Teekloof Formation). Their age determinations support the foreland basin model as they coincide with dated paroxysms. A condensed distal (northern) stratigraphic record is additional support for this tectonic regime because orogenic loading and unloading throughout the basin was not equally distributed, nor was it in-phase. This resulted in more frequent non-deposition with increased distance from the tectonically active source. Refning basin dynamics allows us to distinguish between tectonic and climatic efects and how they have infuenced ancient ecosystems and sedimentation through time. Te Karoo Basin of South Africa represented a large depocenter situated in southern Gondwana supported by the Kaapvaal Craton in the northeast and the Namaqua-Natal Metamorphic Belt (NNMB) in the southwest1, 2.
    [Show full text]