Trace fossil diversity in hyperpycnites: ethologic implications and comparison to trace fossil in episodic gravity flows

CARMONA, N.B.; PONCE, J.J.; LÓPEZ CABRERA, M.I.; OLIVERO, E.B.

Ushuaia, Tierra del Fuego

Conferencia; AAPG Hedberg Research Conference - "Sediment Transfer from Shelf to Deepwater - Revisiting the Delivery Mechanisms"; 2008

The analysis of trace fossil suites in hyperpycnal deposits reflects important clues to understand the dynamic of these flows. These ichnoassemblages, associated to environments with sustained and rapid deposition of sediment, are characterized by a moderate to low diversity, low intensity of bioturbation, ichnotaxa with normal sizes and absence of complex behavioral strategies. In general, the trace fossil suites are mainly dominated by deposit-feeder organisms, showing a paucity of suspension-feeding ethologies (except in more proximal areas). Compared to the trace fossil suites of episodic gravity flow deposits, the ichnofauna of these hyperpycnites show dominance of facies-crossing forms, absence of especialized-feeding ethologies and communities with less-developed tiers. In addition, most of these structures were developed during the depositional event. The evaluation of the ichnologic characteristics in these hyperpycnites helps to recognize the major paleoecological parameters operating in these flows. In particular, the pulsating and sustained character of the hyperpycnal flows seems to be one of the main stresses influencing and controlling the development of the endobenthic communities in these environments.