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Pennsylvanian and Permian sequences in Bolivia; direct responses to Gondwana glaciation

G. W. Grader, P. E. Isaacson, E. Diaz-Martinez and M. C. Pope
Pennsylvanian and Permian sequences in Bolivia; direct responses to Gondwana glaciation (in Resolving the late Paleozoic ice age in time and space, Christopher R. Fielding (editor), Tracy D. Frank (editor) and John L. Isbell (editor))
Special Paper - Geological Society of America (2008) 441: 143-159


Western Gondwana underwent a steady drift from mid-latitudes ( approximately 50 degrees S, Early Carboniferous) to lower latitudes (<40 degrees S) by Late Carboniferous time, and glacial deposition had ended in Bolivia by the early Pennsylvanian (Morrowan). At this time, carbonates and evaporites were being deposited across the Peru-Bolivia Basin. The Pennsylvanian and Permian Titicaca Group represents an Andean transgressive marine to restricted carbonate and regressive red bed megasequence (Cuevo Supersequence or Subandean Cycle). The transgressive part of this Pangean first-order sequence records inherited basement controls and ephemeral pericratonic seaways into the interior of a western landmass. The well-dated Copacabana Formation records many high-frequency sequences and meter-scale cycles that form larger, third-and second-order composite sequences in the central Andes. Diverse carbonates; compositionally immature but texturally more mature arkosic and lithic sandstones, shales, tuffs, and evaporites characterize Copacabana Formation lithologies, which have been dated using foraminifera, fusulinids, conodonts. and palynomorphs. Estuarine barrier sands and cross-bedded, fossiliferous marine sandstones with limestone lithoclasts were derived by reworking of semilithified Copacabana rocks during lowstands and transgressive flooding events. Sedimentation rates in Bolivia were relatively low (7-25 m/m.y.) compared with the thicker and shale-rich Copacabana Formation in Peru. Stacked transgressive systems tracts and highstand systems tracts with significant hiatuses formed in open-marine and restricted to semiarid coastal depositional systems. Twelve second-and third-order, 30-100 m composite sequences have incisement or protosol development above marine limestone of the underlying sequence: extensive siliciclastic lowstand and/or transgressive shoreline facies occur above these sequence boundaries. Thick accumulations of progradational carbonate characterize the highstand systems tracts. More distal subtidal ramp sequences (well-developed in the Cochabamba and northern Subandes areas) are shale-cored with fossiliferous packstone-grainstone caps, but they lack evidence of subaerial exposure or disconformity. Small, meter-scale shallowing-upward parasequences and internal autocyclic, icehouse facies mosaics comprise the larger Copacabana composite sequences. Pennsylvanian sequence boundaries (occurring as a result of glacial drawdowns) occurred at ca. 318 Ma, 311 Ma, 309 Ma, 308 Ma, and 306.5 Ma. Permian drawdowns occurred at 299 Ma, 293 Ma, and 283 Ma.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 441
Title: Pennsylvanian and Permian sequences in Bolivia; direct responses to Gondwana glaciation
Title: Resolving the late Paleozoic ice age in time and space
Author(s): Grader, G. W.Isaacson, P. E.Diaz-Martinez, E.Pope, M. C.
Author(s): Fielding, Christopher R.editor
Author(s): Frank, Tracy D.editor
Author(s): Isbell, John L.editor
Affiliation: University of Idaho, Department of Geological Sciences, Moscow, ID, United States
Affiliation: University of Nebraska Lincoln, Department of Geosciences, Lincoln, NE, United States
Pages: 143-159
Published: 2008
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2441-6
Meeting name: Late Paleozoic ice age; toward a more refined understanding of timing, duration, and character
Meeting location: Salt Lake City, UT, USA, United States
Meeting date: 20050821Oct. 21, 2005
References: 76
Accession Number: 2008-123128
Categories: Stratigraphy
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., strat. cols., 1 table, geol. sketch maps
S17°00'00" - S15°00'00", W69°00'00" - W67°00'00"
Secondary Affiliation: University of Wisconsin Milwaukee, USA, United StatesGeological Survey of Spain, ESP, SpainWashington State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200847
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