CONICET | Buscador de Institutos y Recursos Humanos

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