CONICET | Buscador de Institutos y Recursos Humanos

The Santa Clara Abajo Formation in the north of Mendoza province, Argentina, represents part of the infilling of the Triassic Cuyana rift Basin. Deposits here are interpreted as a lacustrine-fluvial system with development of a delta. The lake lake-center sediments (Finely finely laminated mudrock facies) present actinopterygian specimens that have been previously identified as members of the Pseudobeaconiidae family. Fish remains have been very well preserved, with mainly hard parts remaining, generally undeformed and lie lying concordant to the stratification. A taphonomic analysis has been conducted to determine thermal lake water water-column conditions, which combined with sediment features, provide hints on paleolimnologicaly changes in the system over time. The fish remains can be sorted into three preservation modes through their Taphonomic taphonomic attributes. Mode A: Isolated and dispersed scales. Mode B: associated but dispersed scales, loosely to well sorted, low to moderate density. Mode C: scale patches and articulated fishes. These modes are associated with a range of three thermal lake water water-column conditions from warm to cold temperatures respectively. A The combination of progradational to aggradational stacking pattern plus the identification of a fluctuating profundal facies association suggests the Santa Clara Abajo paleolake was a Balancedbalanced-fill lake system. Stratigraphical analysis of the taphonomic modes for the Balancedbalanced-fill lake allowed interpretationing of a tendency up up-section from fluctuating thermal conditions (cold and warm), to a stable-cold pattern, to a stable-warm pattern, to fluctuating thermal conditions (cold and warm) again. This tendency directly links to lake lake-level fluctuations resulting in paleolake lacustrine intervals that reflect hydrologic closure to hydrology hydrologic opening to hydrologic closure again.