Glaciomarine sequence stratigraphy in the Mississippian Río Blanco Basin, Argentina, southwestern Gondwana. Basin analysis and palaeoclimatic implications for the Late Paleozoic Ice Age during the Tournaisian.

EZPELETA, MIGUEL; RUSTÁN, JUAN JOSÉ; BALSEIRO, DIEGO; DÁVILA, FEDERICO MIGUEL; DAHLQUIST, JUAN ANDRÉS; VACCARI, NORBERTO EMILIO; STERREN, ANDREA FABIANA; PRESTIANNI, CYRILLE; CISTERNA, GABRIELA ADRIANA; BASEI, MIGUEL

JOURNAL OF THE GEOLOGICAL SOCIETY

GEOLOGICAL SOC PUBL HOUSE

Año: 2020

0016-7649

The Late Palaeozoic Ice Age (LPIA) has been well recorded in the uppermost Mis-sissippian?Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics, particularly during the early Mississippian. We report on ex-ceptional Tournaisian glaciomarine stratigraphic sections from central Argentina (Río Blanco Basin). Encompassing ~1400 metres, these successions contain conspicuous glacigenic strata with age constraints provided by palaeontological data and U/Pb detrital zircon age spectra. A variety of marine, glaciomarine and fan-deltaic environments indi-cate 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 Systems Tracts (TST) to Highstand Systems Tracts (HST) sequences unaffected by glacial ice; 2) Lowstand Systems Tracts (LST) to TST and then to HST with glacial influence; and 3) non-glacial Falling-Stage Systems Tract (FSST) to TST and HST. The glacial evidence indicates that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In con-trast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms complex hierarchical climate variability, rather than a single episode of ice advance and retreat.