FLOODPLAIN TAPHONOMIC MODE OF EARLY MIOCENE VERTEBRATES OF SOUTHERN PATAGONIA, ARGENTINA

MONTALVO, CLAUDIA I.; RAIGEMBORN, M. SOL; TOMASSINI, RODRIGO L.; ZAPATA, LUCIANO; BARGO, M. SUSANA; UNCAL, M. CELESTE MARTÍNEZ; VIZCAÍNO, SERGIO F.

PALAIOS

SEPM-SOC SEDIMENTARY GEOLOGY

Lugar: Lawrence; Año: 2019 vol. 34 p. 105 - 120

0883-1351

ABSTRACT: A continental assemblage of fossil mammals from the Santa Cruz Formation (early Miocene,Burdigalian) recovered from the coast of the Santa Cruz Province (Anfiteatro locality), Argentina, was evaluatedtaphonomically. Due to its stratigraphic position and age (~ 17.5 Ma), the fossiliferous level corresponds to the lowersection of the Estancia La Costa Member (lower part of the Santa Cruz Formation). The Anfiteatro assemblage(Santacrucian South American Land Mammal Age) is dominated by mammals, but some birds and carnivorecoprolites were also recorded. The recorded taphonomic features and the sedimentological interpretation suggest thatthe bone remains were preserved in a floodplain related to a fluvial system influenced by volcaniclastic input. Theassemblage was interpreted as a result of death of mammals over a short period of time. The residence time ofcarcasses on the surface was variable. Although most bones were quickly buried, the exposure was sufficiently long forthe disarticulation and scattering of different skeletal components and the agency of other processes (e.g., trampling,weathering). The loss of skeletal elements is linked to the action of water flows generated in the plain, during overbankfloods or rainfalls, which mobilized those elements more susceptible to transport. After burial, the specimens wereaffected by diagenetic processes (e.g., soil corrosion, infilling, impregnation, deformation). The taphonomic evaluationof the Anfiteatro locality provides a framework for the analysis of other fossil assemblages with similar featuresworldwide.