My research interests have been the interpretive sedimentology of ancient strata. This has involved me in studies of sedimentary rocks at locations as varied as Montana, Utah, Mexico, Ireland, Australia, and South Africa in addition to Pennsylvania. The subjects of these studies included Carboniferous limestones, ooidal ironstones, and fluvial, coastal, and shallow-marine siliciclasticdeposits. One thread that linked some of my work has been the investigation of Upper Devonian strata of the same age on several continents. One objective of this was to determine whether these strata preserve a record of small-scale fluctuations of relative sea level. My most recent extension of this thread took me to South Africa to study Upper Devonian strata in the Cape Fold Belt. I found in these strata a stacked series of small-scale shallowing-upward sequences (parasequences) that have the same magnitude as similar cycles in contemporaneous strata on four other continents. This provides a strong argument that the cyclic patterns were were caused by global eustasy, probably by the forces termed Milankovitch orbital variations. You can see some of the general nature as well as the physical sedimentary structures and biogenic structures of these South African rocks.
Publications of the Last Decade:
Cotter, E. (2000) Depositional setting and cyclic development of the lower part of the Witteberg Group (Mid- to Upper Devonian), Cape Supergroup, Western Cape, South Africa: South African Journal of Geology, v. 103, p. 1-14.
Cotter, E. (1998) Silurian coastal sedimentation in the Appalachian Foreland Basin of Pennsylvania modulated by small-scale fluctuations of relative sea level, in Landing, E., and Johnson, M.E., editors, Silurian Cycles: Linking Dynamic Stratigraphy with Atmospheric and Oceanic Changes: New York State Museum Bulletin 492, p. 223-231.
Cotter, E., and Driese, S. G. (1998) Incised valley fills and other evidence of sea-level fluctuations affecting deposition of the Catskill Formation (Upper Devonian), Appalachian Foreland Basin of Pennsylvania: Journal of Sedimentary Research, v. 68, p. 347-361.
Cotter, E. (1998) Late Devonian Milankovitch-scale sea-level cycles of Gondwana confirm global eustasy: 10th International Gondwana Conference, Cape Town, South Africa, Journal of African Earth Sciences, v. 27, no. 1A, p. 48-49.
Cotter, E., and Driese, S.G. (1997) Incised valley/estuarine deposits in the Catskill Formation (Upper Devonian) of Pennsylvania, USA: characteristics, contrasts, and controls: Sixth International Conference on Fluvial Sedimentology, Cape Town, South Africa, Abstracts, p. 42.
Driese, S.G., Mora, C.I., and Cotter, E. (1997) Paleosol changes along a coastal-margin to alluvial-plain transect: Catskill Fm. (Upper Devonian), central Pennsylvania: Geological Society of America Annual Meeting, Salt Lake City, Utah, G.S.A. Abstracts with Programs,
Cotter, E. (1996) Silurian of central Pennsylvania, in Broadhead, T. W., editor, Sedimentary environments of Silurian Taconia: University of Tennessee Studies in Geology, v. 26, p. 128-154.
Cotter, E. (1995) Inclined heterolithic stratification in the "fluvial" Catskill Formation of Pennsylvania: Evidence of repeated marine influence well above formation base: Geological Society of America, Northeastern Section, Cromwell, Connecticut.
Cotter, E., and Link, J.E. (1993) Deposition and diagenesis of Clinton ironstones (Silurian) in the Appalachian Foreland Basin of Pennsylvania: Geological Society of America Bulletin, v. 105, p. 911-922.
Driese, S.G., Mora, C.I., and Cotter, E. (1993) Paleosols, paleoclimate, and paleoatmospheric CO2; Paleozoic paleosols of central Pennsylvania: Field Trip for International Association of Geochemistry and Cosmochemistry and SEPM (Society for Sedimentary Geology), University of Tennessee Studies in Geology, v. 22, 136p.
Driese, S.G., Mora, C.I., Cotter, E., and Foreman, J.L. (1992) Paleopedology and stable isotope chemistry of Late Silurian vertic paleosols, Bloomsburg Formation, central Pennsylvania: Journal of Sedimentary Petrology, v. 62, p. 825-841.
Cotter, E. (1992) Diagenetic alteration of chamositic clay minerals to hematite in oolitic ironstone: Journal of Sedimentary Petrology, v. 62, p. 54-60.
Cotter, E., and Graham, J.R. (1991) Coastal plain sedimentation in the Late Devonian of southern Ireland; cross-stratification in fluvial deposits?: Sedimentary Geology, v. 72, p. 201-224.
Cotter, E. (1990) Storm effects on siliciclastic and carbonate shelf sediments in the medial Silurian succession of Pennsylvania: Sedimentary Geology, v. 69, p. 245-258.
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