Abstract
Located within the continental red beds of the upper Elliot Formation (Eastern Cape, South Africa), the Lower Jurassic Pronksberg bentonite is in close proximity to the boundary between the Triassic and Jurassic, which coincides with one of Earth’s largest mass extinction events. Sedimentological, mineralogical, and major and trace element geochemical data indicates that: (1) the bentonite formed by devitrification of felsic volcanic ash; (2) the deposit was reworked by gentle currents in an ephemeral lake where intense chemical weathering of the volcanic ash occurred; and (3) the source of the original felsic volcanic material was probably in southwest Gondwana (now South America) where explosive silicic igneous activity has been documented not only in the Permian, but also in the Late Triassic and Early Jurassic.
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References
Álvarez PP, Benoit SV, Ottone EG (1995) Las formaciones Rancho de Lata, Los Patillos y otras unidades mesozoicas de la Cordillera Principal de San Juan. Rev Asoc Geol Argent 49:123–142.
Álvarez PP, Ramos VA (1999) The Mercedario rift system in the principal Cordillera of Argentina and Chile. J South Am Earth Sci 12:17–31.
Bohor BF, Triplehorn DM (1993) Tonsteins: Altered Volcanic-Ash Layers in Coal-Bearing Sequences: Boulder, Colorado. Geol Soc Am, pp 47.
Bordy EM, Hancox PJ, Rubidge BS (2004) Fluvial style variations in the Late Triassic–Early Jurassic Elliot Formation, main Karoo Basin, South Africa. JAES 38:383–400.
Bordy EM, Erikson P (2015) SACS Elliot Formation (Late Triassic - Early Jurassic), Karoo Supergroup, South Africa. SAJG 107:397–412.
Bhatia MR, Crook, KAW (1986) Trace element characteristics of greywackes and tectonic discrimination of sedimentary basins. Contrib Mineral Petrol 92:181–192.
Eisenhour D, Reisch F (2006) Bentonite. In: Kogel JE, Trivedi N, Barker JM, Krukowski ST (eds), Industrial Minerals and Rocks. 7th Ed. Colorado: SME Inc., 357–368.
Foulkes S (2009) A geochemical analysis of volcanic ashes in the Pristerognathus, Tropidostoma and Cistecephalus Assemblage Zones of the Beaufort Group, Karoo Supergroup, in the Eastern Cape, South Africa. Unpublished Honours thesis, Rhodes University, Grahamstown, South Africa, pp 56.
Heckroodt R (1991) Clay and clay materials in South Africa. J South Afr Inst Min Metall 91:343–363.
Johnson MR (1971) Provisional geological report: an occurrence of bentonite in the Pronksberg (Mountain), Wodehouse District CP. Geol Surv S Afr Pretoria, 0012 6/196, pp 7.
Keyser N, Zawanda PK (1988) Two occurrences of ash-flow tuff from the lower Beaufort Group in the Heilbronn-Frankfort area, northern Orange Free State. SAJG 91:509–521.
Larsen G, Plum KH, Forster H (1991) Zeolites and other hydrothermal alteration products of synthetic glasses. Eur J Mineral 3:933–941.
Linol B, de Wit M, Barton E, de Wit MJC, Guillocheau F (2015) U–Pb detrital zircon dates and source provenance analysis of Phanerozoic sequences of the Congo Basin, central Gondwana. Gondwana Res 29:208–219.
Lopez-Gamundi O (2006) Permian plate margin volcanism and tuffs in adjacent basins of west Gondwana: Age constraints and common characteristics. J South Am Earth Sci 22:227–238.
Marsh JS (2010) Karoo andesites and dacites. Abstract book of the 2nd Annual Igneous and Metamorphic Studies Group Meeting (January, 2010) Grahamstown, South Africa. Unpaginated.
Marsh JS, Eales H.V (1984) Chemistry and petrogenesis of igneous rocks of the Karoo Central area, southern Africa, Special Publication of the Geological Society of South Africa 13:27–68.
McLachlan IR, Jonker JP (1990) Tuff beds in the northwestem part of the Karoo Basin. SAJG 93:329–338.
Ottone E, Monti M, Marsicano C, de la Fuente M, Naipauer M, Armstrong R, Mancuso A (2014) A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina): SHRIMP U-Pb zircon dating and biostratigraphic correlations across southern Gondwana. J South Am Earth Sci 56:186–199.
Pankhurst RJ, Rapela CW, Fanning CM, Márquez M (2006) Gondwanide continental collision and the origin of Patagonia. Earth-Sci Rev 76:235–257.
Pearce JA, Harris NBW, Tindle AG (1984) Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J Petrol 25:956–983.
Pyle D (1989) The thickness, volume and grainsize of tephra fall deposits. B Volcanol 51:1–15.
Rocha-Campos AC, Basei MA, Nutman AP, Kleiman LE, Varela R, Llambias E, Canile FM, da Rosa OCR (2011) 30 million years of Permian volcanism recorded in the Choiyoi igneous province (W Argentina) and their source for younger ash fall deposits in the Paraná Basin: SHRIMP U–Pb zircon geochronology evidence. Gondwana Res 19:509–523.
Ryan KM, Williams DM (2007) Testing the reliability of discrimination diagrams for determining the tectonic depositional environment of ancient sedimentary basins. Chem Geol 242:103–125.
Sato A M, Llambias EJ, Basei MAS, Castro CE (2015) Three stages in the Late Paleozoic to Triassic magmatism of southwestern Gondwana, the relationships with the volcanogenic events in coeval basins. J South Am Earth Sci 63:48–69.
Schmidt ER (1976) Clay. In: Coetzee C (ed) Mineral resources of the Republic of South Africa. Fifth edition. Geol Surv S Afr Pretoria Handb 7:275–286.
Sciscio L, Bordy EM (2016) A preliminary geochemical study of the Upper Triassic-Lower Jurassic Elliot Formation in southern Africa. JAES http://dx.doi.org/10.1016/j.jafrearsci.2016.03.014.
Sun SS (1982) Geochemical composition and origin of Earth’s primitive mantle. Geochim Cosmochim Acta 46:179–192.
Tomlinson E, Smith C, Albert P, Aydar E, Civetta L, Cian IR, Cubukcu E, Gertisser R, Isaia R, Menzies M, Orsi G, Rosi M, Zanchetti G (2015) The major and trace element glass compositions of the productive Mediterranean volcanic sources: tools for correlating distal tephra layers in and around Europe. Quat Sci Rev 118:48–66.
Viljoen JHA (1994) Sedimentology of the Collingham Formation, Karoo Supergroup. SAJG 97:167–183.
Viljoen JHA (1998) Distribution of altered volcanic ash beds in the Dwyka and Ecca Groups of the main Karoo Basin, South Africa. JAES Special Abstracts Issue, Gondwana 10: Event Stratigraphy of Gondwana 27:204–205.
Weltje GJ, von Eynatten H (2004) Quantitative provenance analysis of sediments: review and outlook. Sediment Geol 171:1–11.
Winchester JA, Floyd PA (1977) Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chem Geol 20:325–343.
Wotzlaw JF, Guex J, Bartolini A, Gallet Y, Krystyn L, McRoberts CA, Taylor D, Schoene B, Schaltegger U (2014) Towards accurate numerical calibration of the Late Triassic: high-precision U-Pb geochronology constraints on the duration of the Rhaetian. Geology 42:571–574.
Acknowledgements
Most of all, we would like to thank Goonie Marsh for the countless stimulating discussions. Our special thanks go to our friends and colleagues Rugshana Daniels, Blair McPhee and Lara Sciscio for field and lab assistance. Albert and Susanna Roodt are acknowledged for graciously allowing us access to the abandoned bentonite pits on Pronksberg. We thank Chris Harris and Agnes Odri for improving an earlier version of the manuscript, and reviewers Jurie Viljoen and Maarten de Wit for their constructive comments. The financial support of the National Research Foundation of South Africa via its African Origins Platform and Completive Program for Rated Researches grants (#82606, #93544) to EMB is hereby acknowledged. Opinions expressed and conclusions arrived at are those of the authors only.
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Bordy, E.M., Abrahams, M. (2016). Geochemistry of the Pronksberg Bentonite of the Upper Elliot Formation (Early Jurassic), Eastern Cape, South Africa. In: Linol, B., de Wit, M. (eds) Origin and Evolution of the Cape Mountains and Karoo Basin. Regional Geology Reviews. Springer, Cham. https://doi.org/10.1007/978-3-319-40859-0_12
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