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APALDETTI Graciela Cecilia

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Título:

Preliminar Taphonomical analysis of Triassic bones from Los Colorados Formation (La Rioja Province, Argentina

Autor/es:

PEREZ, ML; OTERO, ALEJANDRO; KRAPOVICKAS, VERÓNICA; ALONSO, PABLO; LEARDI, JUAN; GAETANO, LEANDRO; APALDETTI, CECILIA

Lugar:

Puerto Madryn

Reunión:

Congreso; XIII RCAPA; 2018

Institución organizadora:

CENPAT

Resumen:

LosColorados Formation is a worldwide recognized continental unit deposited in theIschigualasto-Villa Unión basin in San Juan and La Rioja Provinces,Northwestern Argentina. Itis mainly composed of lenticular sandstone beds and laterally extensive laminatedto massive mudstone units, recording sedimentation in different fluvial settings.These rocks represent a case study for the abundance and diversification eventsthat affected Upper Triassic archosaurs. Although the tetrapod fauna recovered fromthis unit is relatively well-known, their taphonomic modes are scarcely known.In this sense, we present a preliminary petrographic analysis of both epiphysesand diaphysis of bone remains collected in these deposits, and X-raydiffraction, which allowed us to interpret the damaging process that acted onthe bone tissue. The most destructive taphonomical process affecting the bones wascaused by chemical action of dissolved materials acting within fossil-diagenesis.Thin section of the epiphysis shows preserved trabecular bone with cracksperpendicular to the fibers, obtured cavities filled with calcite set in two cycles:microgranular on the periphery and polycristaline euhedral on the centre. Sub-periostealbone, however, is relatively well-preserved. Diaphyses present a highly alteredtrabecular bone, obtured cavities with calcite in three cycles: two microgranularperipherical rows and large euhedral crystal in the internal lumen. Thesub-periosteal bone is mostly altered. X-ray diffraction shows predominant calcitein the epiphysis, whereas gypsum is mostly present in the diaphysis. Summingup, diagenetic cracks allowed the circulation of solutions (mostly with calciteand gypsum) in the bone, expanding and destroying it.

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