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Geochemical Signatures of Paleodepositional and Diagenetic Environments: A STEM/AEM Study of Authigenic Clay Minerals from an Arid Rift Basin, Olduvai Gorge, Tanzania

Published online by Cambridge University Press:  01 January 2024

Victoria C. Hover  and
Gail M. Ashley
Victoria C. Hover*
Affiliation:
Department of Earth and Environmental Science, Rutgers University, Newark, NJ 07081-1819, USA
Gail M. Ashley
Affiliation:
Department of Geological Sciences, Rutgers University, Piscataway, NJ 08854-8066, USA
*
*E-mail address of corresponding author: [email protected]
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Abstract

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Olduvai Gorge, Tanzania (East African Rift) exposes a 100 m thick Plio-Pleistocene sequence of dominantly volcaniclastic sediments deposited in a 50 km wide closed basin containing a playa lake. A scanning transmission electron and analytical electron microscopy (STEM/AEM) study of authigenic clay minerals in sediments from representative depositional environments in the basin (pyroclastic fan, fluvial plain, wetland, lake margin and lake basin) was undertaken to determine whether clay compositions and textures could provide unique geochemical fingerprints characteristic of source area (Plio-Pleistocene trachytic volcanics vs. Precambrian quartzose-feldspathic basement) or paleoenvironmental conditions.

Our study shows that compositional signatures obtained by clay minerals during early pedogenesis are inherited from their parent source rocks. Sediments sourced from volcanics contain highly disordered, dioctahedral smectite. Those sourced from Precambrian basement are similar, but are more Al-rich. Subsequent neoformation in the pedogenic (soil) or diagenetic (lake-margin, lake) environments results in the modification of original clay mineralogy, compositions, and textures, and unique paleoenvironmental fingerprints are acquired. Soils developed on the distal pyroclastic fan contain smectite with more Fe(III) and Mg than smectite from the proximal pyroclastic fan sediments. A trend of decreasing Al and increasing Mg content occurs in smectite compositions in samples from the fluvial to lake-margin and lake environments as a result of partial replacement of original dioctahedral Al-rich smectite by neoformed trioctahedral Mg-rich smectite (stevensite). Neoformed celadonite replaces smectite in the most saline lake sediments.

The STEM/AEM data collectively indicate that diagenesis in the saline-alkaline lake results in the replacement of Al-rich dioctahedral smectite by Mg-rich trioctahedral smectite (stevensite) and Mg- and Al-rich celadonite. Thus, determination of clay mineral compositions at a basin-wide scale provides a useful tool for interpreting the spatial distribution of depositional and diagenetic environments.

Keywords

CeladoniteClay NeoformationEarly DiagenesisPedogenesisSmectite
Type
Research Article
Information
Clays and Clay Minerals , Volume 51 , Issue 3 , June 2003 , pp. 231 - 251
Copyright
Copyright © 2003, The Clay Minerals Society

References

Ashley, G.M., (1996) Springs, pools, and adjacent wetlands, a newly recognized habitat, lowermost Bed II, Olduvai Gorge, Tanzania Geological Society of America Abstracts with Program 26 28.Google Scholar
Ashley, G.M., (2000) Geologists probe Hominid environments: Geological Society of America 1999 Presidential Address GSA Today 10 24 29.Google Scholar
Ashley, G.M., (2001) Orbital rhythms, monsoons, and play a lake response, Olduvai Basin, Equatorial East Africa at 1.85–1.75 Ma EOS, Transactions, American Geophysical Union, supplement, Abstracts 82 47 F759.Google Scholar
Ashley, G.M. and Driese, S.G., (2000) Paleopedology and paleohydrology of volcaniclastic paleosol: implications for Early Pleistocene paleoclimate record, Olduvai Gorge, Tanzania Journal of Sedimentary Research 70 1065–1080 10.1306/040300701065.Google Scholar
Ashley, G.M. Hay, R.L., Renaut, R.W. and Ashley, G.M., (2002) Sedimentation patterns in a Plio-Pleistocene volcaniclastic rift-platform basin, Olduvai Gorge, Tanzania Sedimentation in Continental Rifts Tulsa, Oklahoma Society for Sedimentary Geology 107–122 10.2110/pec.02.73.0107.Google Scholar
Ashley, G.M. Renaut, R.W., Renaut, R.W. and Ashley, G.M., (2002) Rift Sedimentation Sedimentation in Continental Rifts Tulsa, Oklahoma Society for Sedimentary Geology 3–10 10.2110/pec.02.73.0003.Google Scholar
Badaut, D. and Risacher, F., (1983) Authigenic smectite on diatom frustules in Bolivian saline lakes Geochimica et Cosmochimica Acta 47 363–375 10.1016/0016-7037(83)90259-4.Google Scholar
Banfield, J.F. and Barker, W.W., (1998) Low-temperature alteration in tuffs from Yucca Mountain, Nevada Clays and Clay Minerals 46 27–37 10.1346/CCMN.1998.0460104.Google Scholar
Banfield, J.F. Jones, B.F. and Veblen, D.R., (1991) An AEM-STEM study of weathering and diagenesis, Abert Lake, Oregon: I. Weathering reactions in volcanics Geochimica et Cosmochimica Acta 55 2781–2793 10.1016/0016-7037(91)90444-A.Google Scholar
Banfield, J.F. Jones, B.F. and Veblen, D.R., (1991) An AEM-STEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage Geochimica et Cosmochimica Acta 55 2795–2810 10.1016/0016-7037(91)90445-B.Google Scholar
Baxter Grubb, S.M. Peacor, D.R. and Jiang, W.-T., (1991) Transmission electron microscope observations of illite polytypism Clays and Clay Minerals 39 540–550 10.1346/CCMN.1991.0390509.Google Scholar
Blumenschine, R.J. and Masao, F.T., (1991) Living sites at Olduvai Gorge, Tanzania? Preliminary landscape archaeology results in the basal Bed II lake margin zone Journal of Human Evolution 21 451–462 10.1016/0047-2484(91)90095-D.Google Scholar
Blumenschine, R.J. and Peters, C.R., (1998) Archaeological predictions for hominid land use in the paleo-Olduvai Basin, Tanzania, during lowermost Bed II times Journal of Human Evolution 34 565–607 10.1006/jhev.1998.0216.Google Scholar
Brindley, G.W., (1955) Stevensite, a montmorillonite-type mineral showing mixed-layer characteristics American Mineralogist 40 239 247.Google Scholar
Carstea, D.D. Harward, M.E. and Knox, E.G., (1970) Formation and stability of hydroxy-Mg interlayers in phyllosilicates Clays and Clay Minerals 18 213–222 10.1346/CCMN.1970.0180405.Google Scholar
Çolak, M. Helvaci, C. and Maggetti, M., (2000) Saponite from the Emet colmenite mines, Kütahya, Turkey Clays and Clay Minerals 48 409–423 10.1346/CCMN.2000.0480401.Google Scholar
Darragi, F. and Tardy, Y., (1987) Authigenic trioctahedral smectites controlling pH, alkalinity, silica and magnesium concentrations in alkaline lakes Chemical Geology 63 59–72 10.1016/0009-2541(87)90074-X.Google Scholar
Decarreau, A. Grauby, O. and Petit, S., (1992) The actual distribution of octahedral cations in 2:1 clay minerals: Results from clay synthesis Applied Clay Science 7 147–167 10.1016/0169-1317(92)90036-M.Google Scholar
de la Fuente, S. Cuadros, J. Fiore, S. and Linares, J., (2000) Electron microscopy study of volcanic tuff alteration to illite-smectite under hydrothermal conditions Clays and Clay Minerals 48 339–350 10.1346/CCMN.2000.0480305.Google Scholar
Deocampo, D.M. and Ashley, G.M., (1999) Siliceous island in a carbonate sea: modern and Pleistocene records of spring-fed wetlands in Ngorongoro Crater and Olduvai Gorge, Tanzania Journal of Sedimentary Research 69 974–979 10.2110/jsr.69.974.Google Scholar
Deocampo, D.M. Blumenschine, R.J. and Ashley, G.M., (2002) Wetland diagenesis and traces of early Hominids, Olduvai Gorge, Tanzania Quaternary Research 57 271–281 10.1006/qres.2001.2317.Google Scholar
Dong, H. and Peacor, D.R., (1996) TEM observations of coherent stacking relations in smectite, I/S and illite of shales: Evidence for MacEwan crystallites and dominance of 2M1 polytypism Clays and Clay Minerals 44 257–275 10.1346/CCMN.1996.0440211.Google Scholar
Drever, J.I., (1973) The preparation of oriented clay mineral specimens for X-ray diffraction analysis by a filtermembrane peel technique American Mineralogist 58 553 554.Google Scholar
Eberl, D.D. Jones, B.F. and Khoury, H.N., (1982) Mixed-layer kerolite/stevensite from the Amargosa Desert, Nevada Clays and Clay Minerals 30 321–326 10.1346/CCMN.1982.0300501.Google Scholar
Eberl, D.D. Środoń, J. Northrop, H.R., Davis, J.A. and Hayes, K.F., (1986) Potassium fixation in smectite by wetting and drying Geochemical Processes at Mineral Surfaces Washington, D.C. The American Chemical Society 296–326 10.1021/bk-1987-0323.ch014.Google Scholar
Faust, G.T. and Murata, K.J., (1953) Stevensite, redefined as a member of the montmorillonite group American Mineralogist 38 973 987.Google Scholar
Faust, G.T. Hathaway, J.C. and Millot, G., (1959) A restudy of stevensite and allied minerals American Mineralogist 44 342 370.Google Scholar
Fiore, S., (1993) The occurrences of smectite and illite in a pyroclastic deposit prior to weathering: Implication on the genesis of 2:1 clay minerals in volcanic soils Applied Clay Science 8 249–259 10.1016/0169-1317(93)90007-N.Google Scholar
Foster, M., (1960) Interpretation of the composition of trioctahedral micas US Geological Survey Professional Paper 354–B 11 50.Google Scholar
Frostick, L.E., Renaut, R.W., Reid, I. and Tiercelin, J.-J. (1986) Sedimentation in the African Rifts. Special Publication 25. Geological Society of London, 382 pp.Google Scholar
Gac, J.Y. Droubi, A. Fritz, B. and Tardy, Y., (1977) Geochemical behavior of silica and magnesium during the evaporation of waters in Chad Chemical Geology 19 215–228 10.1016/0009-2541(77)90016-X.Google Scholar
Garrels, R.M. Mackenzie, F.T. and Stumm, W., (1967) Origin of the chemical compositions of some springs and lakes Equilibrium Concepts in Natural Water Systems Washington, D.C American Chemical Society 222–242 10.1021/ba-1967-0067.ch010.Google Scholar
Guthrie, G.D. and Veblen, D.R., (1990) Interpreting one dimensional high-resolution transmission electron micrographs of sheet silicates by computer simulation American Mineralogist 75 276 288.Google Scholar
Hay, R.L. and Morgan, B.A., (1970) Silicate reactions in three lithofacies of a semi-arid basin, Olduvai Gorge, Tanzania The Fiftieth Anniversary Symposia: Mineralogy and Petrology of the Upper Mantle, Sulfides, and Geochemistry of Non-marine Evaporites Washington, D.C Mineralogical Society of America 237 255.Google Scholar
Hay, R.L., (1976) Geology of Olduvai Gorge, a Study of Sedimentation in a Semiarid Basin Berkeley, California University of California 203 pp.Google Scholar
Hay, R.L., (1989) Holocene carbonatite-nephelinite tephra deposits of Oldoinyo Lengai, Tanzania Journal of Volcanic Geothermal Research 37 77–91 10.1016/0377-0273(89)90114-5.Google Scholar
Hay, R.L. and Laporte, L.F., (1990) Olduvai Gorge; A case history in the interpretation of hominid paleoenvironments in East Africa Establishment of a Geologic Framework for Paleoanthropology Boulder, Colorado Geological Society of America 23–37 10.1130/SPE242-p23.Google Scholar
Hay, R.L. and Kyser, T.K., (2001) Chemical sedimentology and paleoenvironmental history of Lake Olduvai, a Pleistocene lake in northern Tanzania Geological Society of America Bulletin 113 1505–1521 10.1130/0016-7606(2001)113<1505:CSAPHO>2.0.CO;2.Google Scholar
Hover, V.C. Walter, L.M. Peacor, D.R. and Martini, A.M., (1999) Mg-smectite authigenesis in a marine evaporative environment, Salina Ometepec, Baja, California Clays and Clay Minerals 47 252–268 10.1346/CCMN.1999.0470302.Google Scholar
Hover, V.C. Walter, L.M. and Peacor, D.R., (2002) K-uptake by modern estuarine sediments during early marine diagenesis, Mississippi delta plain, Louisiana Journal of Sedimentary Research 72 775–792 10.1306/032502720775.Google Scholar
Huertas, F.J. Caudros, J. Huertas, F. and Linares, J., (2000) Experimental study of the hydrothermal formation of smectite in the beidellite-saponite series American Journal of Science 300 504–527 10.2475/ajs.300.6.504.Google Scholar
Jackson, M.L., (1969) Soil Chemical Analysis–Advanced Course 895 pp.Google Scholar
Jiang, W.-T. Peacor, D.R. Merriman, R.J. and Roberts, B., (1990) Transmission and analytical electron microscopic study of mixed-layer illite/smectite formed as an apparent replacement product of diagenetic illite Clays and Clay Minerals 38 449–468 10.1346/CCMN.1990.0380501.Google Scholar
Jones, B.F. (1986) Clay mineral diagenesis in lacustrine sediments. Pp. 291–300 in: Studies in Diagenesis (Mumpton, F.A., editor). US Geological Survey Bulletin, 1578.Google Scholar
Jones, B.F. and Weir, A.H., (1983) Clay minerals of Lake Abert, an alkaline, saline lake Clays and Clay Minerals 31 161–172 10.1346/CCMN.1983.0310301.Google Scholar
Khoury, H.N. Eberl, D.D. and Jones, B.F., (1982) Origin of magnesium clays from the Amargosa Desert, Nevada Clays and Clay Minerals 30 327–336 10.1346/CCMN.1982.0300502.Google Scholar
Kim, J.-W. Peacor, D.R. Tessier, D. and Elsass, F., (1995) A technique for maintaining texture and permanent expansion of smectite interlayers for TEM observations Clays and Clay Minerals 43 51–57 10.1346/CCMN.1995.0430106.Google Scholar
Kappelman, J., (1984) Plio-Pleistocene environments of Bed I and lower Bed II, Olduvai Gorge, Tanzania Palaeogeography, Palaeoclimatology, and Palaeoecology 48 171–196 10.1016/0031-0182(84)90043-9.Google Scholar
Kappelman, J., (1986) Plio-Pleistocene marine-continental correlation using habitat indicators from Olduvai Gorge, Tanzania Quaternary Research 25 141–149 10.1016/0033-5894(86)90052-9.Google Scholar
Laird, D.A. and Mermut, A.R., (1994) Evaluation of the structural formula and alkylammonium methods of determining layer charge Layer Charge Characteristics of 2:1 Silicate Clay Minerals Boulder, Colorado Clay Minerals Society 79 103.Google Scholar
Leakey, L.S.B. (1965) Olduvai Gorge: 1951–1961. Vol. I. Cambridge University Press, Cambridge, UK.Google Scholar
Leakey, M.D., (1971) Olduvai Gorge: Excavations in Beds I and II. 1960–1963 UK Cambridge University Press 309 pp.Google Scholar
Liutkus, C.M. and Ashley, G.M. (2003) Sedimentology and stratigraphy of and ancient freshwater lake-margin wetland, Olduvai Gorge, Tanzania. Journal of Sedimentary Research (in press).Google Scholar
Moore, D.M. and Reynolds, R.C., (1997) X-ray Diffraction and the Identification and Analysis of Clay minerals Oxford, UK Oxford University Press 378 pp.Google Scholar
Odin, G.S., (1988) Green Marine Clays Amsterdam Elsevier 445 pp.Google Scholar
Paquet, H., Duplay, J., Valeron-Blanc, M.-M. and Millot, G. (1987) Octahedral compositions of individual particles in smectite-palygorskite and smectite-sepiolite assemblages. Pp. 73–77 in: Proceedings of the International Clay Conference, Denver, 1985 (Schultz, L.G., Olphen, H. van and Mumpton, F.A., editors). The Clay Minerals Society, Bloomington, Indiana.Google Scholar
Peacor, D.R. and Buseck, P.R., (1992) Diagenesis and low grade metamorphism of shales and slates Minerals and Reactions at the Atomic Scale: Transmission Electron Microscopy Washington, D.C Mineralogical Society of America 335–380 10.1515/9781501509735-013.Google Scholar
Peacor, D.R. and Buseck, P.R., (1992) Analytical electron microscopy: X-ray analysis Minerals and Reactions at the Atomic Scale: Transmission Electron Microscopy Washington, D.C Mineralogical Society of America 113–140 10.1515/9781501509735-008.Google Scholar
Polyak, V.G. and Güven, N., (2000) Authigenesis of trioctahedral smectite in magnesium-rich carbonate speleothems in Carlsbad Cavern and other caves of the Guadalupe Mountains, New Mexico Clays and Clay Minerals 48 317–321 10.1346/CCMN.2000.0480302.Google Scholar
Peters, C.R. and Blumenschine, R.J., (1995) Landscape perspectives on possible land use patterns for early hominids in the Olduvai Basin Journal of Human Evolution 29 321–362 10.1006/jhev.1995.1062.Google Scholar
Reading, H., (1996) Sedimentary Environments: Processes, Facies and Stratigraphy 3rd UK Blackwell Science 688 pp.Google Scholar
Reynolds, R.C. Jr, Brindley, G.W. and Brown, G., (1980) Interstratified clay minerals Crystal Structures of Clay Minerals and their X-ray Identification London The Mineralogical Society 249 303.Google Scholar
Seifert, F., (1968) X-ray powder data for Mg-Al celadonite (leucophyillite) from Barcza, Poland Contributions to Mineralogy and Petrology 19 93–96 10.1007/BF00371731.Google Scholar
Singer, A., (1980) The paleoclimatic interpretation of clay minerals in soils and weathering profiles Earth-Science Reviews 15 303–327 10.1016/0012-8252(80)90113-0.Google Scholar
Singer, A., (1984) The paleoclimatic interpretation of clay minerals in sediments–a review Earth-Science Reviews 21 251–293 10.1016/0012-8252(84)90055-2.Google Scholar
Singer, A. and Stoffers, P., (1980) Clay mineral diagenesis in two East African lake sediments Clay Minerals 15 291–307 10.1180/claymin.1980.015.3.09.Google Scholar
Środoń, J. Morgan, D.J. Eslinger, E.V. Eberl, D.D. and Karlinger, M.F., (1986) Chemistry of illite/smectite and end-member illite Clays and Clay Minerals 34 368–378 10.1346/CCMN.1986.0340403.Google Scholar
Stoffers, P. and Singer, A., (1979) Clay minerals in Lake Mobuto Sese Seko (Lake Albert)–Their diagenetic changes as indicators of the paleoclimate Geologische Rundschau 68 1009–1024 10.1007/BF02274684.Google Scholar
Takahashi, N. Tanaka, M. Satoh, T. Endo, T. and Shimada, M., (1997) Study of synthetic clay minerals. Part IV: synthesis of microcrystalline stevensite from hydromagnesite and sodium silicate Microporous Materials 9 35–42 10.1016/S0927-6513(96)00084-3.Google Scholar
Tardy, Y. Cheverry, C. and Fritz, B., (1974) Neoformation d’une argile magnésienne dan les dépressions interdunaires du lac Tchad: Application aux domaines de stabilité des phyllosilicates alumineaux mangésiens et ferriéres Comptes Rendu Academy Science français, Paris Serial C 278 1999 2002.Google Scholar
Tazaki, K. Fyfe, W.S. and van der Gaast, S.J., (1989) Growth of clay minerals in natural and synthetic glasses Clays and Clay Minerals 37 348–354 10.1346/CCMN.1989.0370408.Google Scholar
Tettenhorst, R. and Moore, G.E. Jr, (1978) Stevensite oolites from the Green River Formation of central Utah Journal of Sedimentary Petrology 48 587 594.Google Scholar
Yuretich, R.F. and Cerling, T.E., (1983) Hydrogeochemistry of Lake Turkana, Kenya: mass balance and mineral equilibria in an alkaline lake Geochimica et Cosmochimica Acta 47 1099–1109 10.1016/0016-7037(83)90240-5.Google Scholar
van der Pluijm, B.A. Lee, J.H. and Peacor, D.R., (1988) Analytical electron microscopy and the problem of potassium diffusion Clays and Clay Minerals 36 498–504 10.1346/CCMN.1988.0360603.Google Scholar
von Damm, K.L. and Edmond, J.M., (1984) Reverse weathering in the closed-basin lakes of the Ethiopian Rift American Journal of Science 284 835–862 10.2475/ajs.284.7.835.Google Scholar
Warren, E.A. and Ransom, B., (1992) The influence of analytical error upon the interpretation of chemical variations in clay minerals Clays and Clay Minerals 27 193–209 10.1180/claymin.1992.027.2.05.Google Scholar
Weaver, C.D. and Pollard, L.D., (1973) The Chemistry of Clay Minerals Amsterdam Elsevier Scientific Publishing Co. 213 pp.Google Scholar
Webster, D.M. Jones, B.F., Renaut, R.W. and Last, W.M., (1994) Paleoenvironmental implications of lacustrine clay minerals from the Double Lakes Formation, southern high plains, Texas Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Tulsa, Oklahoma Society for Sedimentary Geology 159–172 10.2110/pec.94.50.0159.Google Scholar