Late Paleozoic carbonates and glacial deposits in Bolivia and northern Argentina: significant paleoclimatic changes

ANDERSON, H.; DI PASQUO, M.M.; GRADER GEORGE W.; ISAACSON, P.

Latitudinal Controls on Stratigraphic Models and Sedimentary Concepts

Allen Press Inc.

Lugar: TULSA; Año: 2019; p. 185 - 203

di Pasquo Mercedes M., Anderson Folnagy Heidi J., Isaacson Peter E., Grader George W., 2017. Late Paleozoic carbonates and glacial deposits in Bolivia and northern Argentina: significant paleoclimatic changes. Hedberg Conference? Latitudinal Controls on Stratigraphic Models and Sedimentary Concepts SEPM (Society for Sedimentary Geology), (submitted August 2015) (accepted june 2017). Special Publication Latitudinal Controls on Stratigraphic Models and Sedimentary Concepts No. 108 (2019) p. 185?203. DOI: https://doi.org/10.2110/sepmsp.108.10 https://sedimentary-geology-store.com/highlights/special-publications ISBN 978-56576-346-3, eISBN 978-56576-347-0- Tulsa, Oklahoma 74135-5814, U.S.A. https://sepm.org/Downloads.aspx. A marked climatic paleogradient (from west northwest to south) is visible in the Carboniferous depositional systems in Bolivia. In thenorthwest is the Pangean trend, a warm-water Pennsylvanian and Permian succession (preceded by a Late Devonian glacially derived rock assemblage).To the south is the cold climate Gondwanan trend, a succession of Late Devonian and Pennsylvanian cold-water siliciclastics with glacially influenceddeposition. Whereas Devonian through (limited) Mississippian strata are comparable in overall character, a sharp climatic gradient in western SouthAmerica is established by the earliest Pennsylvanian. The Pangean trend in northwestern Bolivia and Peru continues with warm-water Pennsylvanianand Permian carbonates, evaporites, and mixed siliciclastics of a semiarid, open seaway association (Copacabana Formation). This unit was depositedby marine transgression north (northern Bolivian subsurface and Lake Titicaca area), reaching central Bolivia by the Early Permian (Early Cisuralian).Regionally, the warm Pangean pattern continues into the younger and more restricted overlying Cisuralian and younger Permian and Triassic rockscharacterized by restricted marine deposits of both humid and arid association (including red beds). To the south, Early Pennsylvanian rocks in theGondwanan trend record continental and lacustrine glacial deposition as far north as central Bolivia, with glacial influence strongest in southern Boliviaand northern Argentina. By the Late Pennsylvanian, glacial influence has waned and is restricted to southern Bolivia near the Argentine border. TheCopacabana Formation is enigmatic because of the following: (1) its autochthonous succession over cold-water, glaciogenic deposits of the LateDevonian and Mississippian and (2) its apparent coeval deposition with Pennsylvanian (and Permian) glacial diamictites. Although the former can beattributed to paleolatitudinal shift, or a clockwise rotation of Gondwana, what is not easily explained (and much discussed) is the autochthonouscontinuity of northeastern and central Bolivian carbonate deposits of the northern Peru?Bolivia Basin with southern Pennsylvanian and Permianglaciogenic deposits, which accumulated in the Tarija?Chaco Basin. Given that these cold and warm-water deposits were coeval in time, a severeclimate gradient must have existed across Bolivia beginning in Pennsylvanian time. Western Gondwana records steady movement from high latitudes(~558S) in the Late Devonian to midlatitudes (~408S) by Pennsylvanian time. Glacial deposits seen in the northwest during the Late Devonian becomerestricted to the southern Tarija?Chaco Basin by the Late Pennsylvanian. By Early Pennsylvanian (Bashkirian) time, carbonates, evaporites, andsiliciclastics were deposited in northwest Bolivia. In central Bolivia, Mississippian diamictites, undated Pennsylvanian siliciclastics, Copacabanalithofacies, and carbonates of the Vitiacua Formation are vertically stacked at a few locations.