Preservation study of Triassic Charophytes (Cerro Puntudo San Juan, Argentina). A chemometric approach.

BENAVENTE, C. A.; D`ANGELO J A; CRESPO, E M.

Mendoza

Simposio; 6th International Symposium on Extant and Fossil Charophytes; 2012

International Research Group on Charophytes (IRGC)

A chemometric study of energy-dispersive X-ray data was performed to study preservation features (major and minor chemical components) of Charophytes (gyrogonites). The gyrogonites have been found in the Cerro Puntudo Formation (Anisian ?243.8 ± 1.9 my? Cuyana Basin), in a microbialitic carbonate lacustrine succession. Gyrogonites belonging to three different strata of the succession were analyzed. Spectrochemical data were obtained using scanning electron microscopy in combination with energy-dispersive X-ray spectrometry (SEM-EDS). Semi-quantitative data were analyzed by Principal Component Analysis (PCA). SEM-EDS spectra show the presence of O, Ca, and minor elements (e.g., Si and Mg), indicating a predominantly calcium carbonate (CaCO3) composition. PCA model supports differences obtained between central and peripheral areas of the gyrogonites, indicating a higher CaCO3 content (or lower Ca concentration) in the central part of the gyrogonites. No considerable differences were found among gyrogonites from the three different strata, implying a similar preservation mode. This suggests a differential diagenetic pattern for the external cells of the gyrogonites and its centre. These data also have implications about the chemical composition of the paleolake water (Si and Ca availability) and the provenance and catchment areas.