Carbonate-siliciclastic sequences of the Pennsylvanian and Permian Copacabana Formation, Titicaca Group, Andes of Bolivia

Depositional history of the Copacabana Formation within the Pennsylvanian-Permian Titicaca Group comprises part of a central Andean Late Paleozoic-Triassic marine through regressive red bed megasequence (Cuevo Supersequence). This Pangean 1st-order transgressive-regressive sequence in the Peru-Bolivia Basin records inherited basement controls and ephemeral pericratonic seaways behind a western landmass (arc). It is unclear how Late Paleozoic depositional systems in the central Andes were connected, and accumulation histories need regional synthesis. Twenty detailed stratigraphic sections (∼400 to 30 m thick) of the Copacabana Formation were measured in the Cordillera Oriental and Altiplano of Bolivia, and detailed biostratigraphic data was complied at each.; The Copacabana Formation was differentiated into a localized Bashkirian-Moscovian lower member, a widespread Kasimovian-Sakmarian middle member, and a ubiquitous Artinskian upper member. Carbonates and compositionally immature sandstones, with minor shales, tuffs and evaporates characterize heterolithic, cyclic ratty facies stacking patterns. Major differences in initial sediment accumulation and styles of deposition occur at the Copacabana Peninsula (Altiplano area), the Huarina fold and thrust belt, the Cochabamba area, and the southeast Subandes area.; Stacked, mainly transgressive and highstand systems tracts with significant hiatuses represent up-dip, open and restricted to semi-arid coastal and marine depositional systems. About twelve 2nd to 3rd-order, 30 to 100 m composite sequences show significant accumulation of siliciclastic lowstand/transgressive shoreline facies above sequence boundaries. Paleosols developed over marine limestones of the underlying sequence. Thick accumulations of aggradational-progradational carbonates and minor sandstone characterize HSTs. More distal subtidal ramp sequences are shale cored and occur without subaerial exposure of fossiliferous packstone-grainstone caps. Small meter-scale shallowing-upward autocyclic facies mosaics populate the larger Copacabana sequences.; Accumulation patterns are indicative of combined tectonic and high-amplitude, high-frequency glacio-eustatic depositional controls. The Upper Copacabana Member has a more slowly changing character, both in shallow and deep-water environments, and reflects a continuum of regional accommodation and global transition from icehouse to greenhouse conditions. Warm-water carbonates with West Texas-Andean fauna overlie glacially influenced coldwater Mississippian deposits and underlie tropical Triassic red beds. Late Paleozoic history of the Cuevo Supersequence suggests a Pennsylvanian-Permian back-arc strike-slip to incipient rift tectonic setting.