GLACIOMARINE SEQUENCE STRATIGRAPHY IN THE MISSISSIPPIAN RÍO BLANCO BASIN, ARGENTINA, SOUTHWESTERN GONDWANA. BASIN ANALYSIS AND PALEOCLIMATIC IMPLICATIONS FOR THE LATE PALEOZOIC ICE AGE DURING THE TOURNAISIAN.

EZPELETA M.; RUSTÁN J.J.; BALSEIRO D; FEDERICO, DAVILA; DAHLQUIST J.; VACCARI N.E.; STERREN A.; PRESTIANNI, C.; CISTERNA G.; BASEI, MIGUEL

Paraná

Congreso; VIII Congreso Latinoamericano de Sedimentología- XVII Reunión Argentina de Sedimentología; 2021

Asociación Argentina de Sedimentología

The late Paleozoic ice age (LPIA) has been well-recorded in the uppermost Mississippian ? Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics specially during the early Mississippian. We here report exceptional Tournaisian siliciclastic marine stratigraphic sections from the Andean region of central Argentina (Sierra de Las Minitas, Río Blanco Basin). Encompassing ~1400 meters, these successions contain conspicuous glacigenic evidences (eg. dropstones, primary glacial diamictites, faceted, bullet and striated clasts) with its age constrained by paleontological data and U/Pb detrital zircons. A variety of marine, glaciomarine, and fan-deltaic environments, evidence relative sea-level variations mainly associated with tectonism and repetitive cycles of glacial activity. Provenance analysis indicates a source from the Sierras Pampeanas basement located to the East. Fifteen sequences were grouped into three depositional models: 1) Transgressive System Tracts (TST) to Highstand System Tracts (HST) sequences unaffected by glacial ice, 2) Lowstand System Tracts (LST) to TST and finally HST with glacial influence, and 3) non glacial Falling-Stage Systems Tract (FSST) to TST and HST. The glacial evidences are present in the basal 6six sequences, and indicate that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In contrast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms a complex hierarchical climatic variability, instead of a single episode of ice advance and retreat.