INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Lacustrine Triassic paleoenvironments from Argentina: a context to paleobiology
MANCUSO, ADRIANA CECILIA; BENAVENTE, CECILIA ANDREA
Congreso; 11º CONGRESO DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA; 2016
New sedimentological, mineralogical and geochemical data from the units of the Triassic Cuyana (CB) and Ischigualasto-Villa Unión (IVUB) rift basins along with the revision of pre-existing data provides a more accurate paleoenvironmental-paleoclimate framework for their biotas. For the CB during Anisian times, the Cerro de las Cabras Formation represents an ephemeral playa-lake. Its aggradational succession corresponds to an underfilled lake with persistently closed surface hydrology. However, stable isotope geochemistry points to an open groundwater supply and a regional recharge point for the aquifer. The Cerro Puntudo Formation represents an alkaline playa-lake fed by groundwater and ephemeral surface-water input. The unit is an aggradational?minor progradational succession, suggesting a balanced-filled lake type. Geochemistry data from carbonates indicates that the system was a through-flow lake. Mineralogy data for these two paleolakes indicate a seasonal regime with an alternating evaporative-dilution-evaporative stratigraphic trend. This reflects a possible arid-humid-arid regional paleoclimate pattern (aquifer fluctuation). During Late Norian times, the Santa Clara Arriba Formation represents a deltaic-lacustrine system interpreted as a shallow stratified overfilled lake type. Geochemical data from its carbonates might indicate a long residence time for lake waters and the tendency to hydrological closure perhaps linked to seasonal rainfall. For the IVUB, during Carnian times, the Los Rastros paleolake previously known as an overfilled lake type presents palustrine carbonate deposits that record a low evaporative tendency up-section within the lower section of the unit. The multifactor analysis of all the data presented allows interpreting a paleoecosystem context in which paleobiodiversity can be better assessed.