Plant taphonomy in a lake affected by volcanism (Agua de la Zorra Formation, Upper Triassic) Mendoza, Argentina

PEDERNERA, TOMÁS; MANCUSO, ADRIANA CECILIA; BENAVENTE, CECILIA ANDREA; OTTONE, EDUARDO GUILLERMO

PALAIOS

SEPM-SOC SEDIMENTARY GEOLOGY

Lugar: Lawrence; Año: 2020

0883-1351

Volcanic eruptions have an impact on the paleoecologyof plant communities and their preservation in the fossil record. The aim ofthis contribution is to evaluate the influence of volcanism on plantpreservation in lacustrine settings, via systematic sampling and chemicalanalyses of fossil plants in the Upper Triassic Agua de la Zorra Formation, ofthe Argentinian Cuyana Basin. Plant remains are not uniformly preservedthroughout the section of the Agua de la Zorra Formation and their stratigraphicdistribution reflects the original spatial pattern of the plant communities. SEM-EDXanalyses was used to demonstrate how volcanism affected diagenesis of the plantremains. Eight taphonomic modes were determined from biostratinomic analysis,and three preservational modes from the chemical features observed in theSEM-EDX spectra. The three preservation modes recognized by SEM-EDX analysisare more likely linked to diagenesis and are not equivalent to the taphonomicmodes described based on the biostratinomic features. The Agua de la Zorrapaleolake preferentially preserved plant material because of anoxic conditions indeeper parts of the lake, and a high sedimentation rate in proximal near-shorefacies. The plant remains are most abundant in sandy facies deposited byhigh-energy flows but there is no evidence that these flows were pyroclasticnor that the plant remains were generated by volcanic trauma.