OSTRACODA FROM MIOCENE DEEP-WATER DEPOSITS IN CENTRAL CHILE: PRELIMINARY RESULTS

Analyses of late Miocene exposures of the Navidad, Ranquil, and Lacui Formations along the central coast of Chile yield a marine ostracode fauna comprised of 108 species. This is a temperate to cold-water fauna fauna, mostly endemic, with nearly a third of its species reported from the Southwest Atlantic and Southern Ocean. Planktic foraminifers correlate the three units with the Tortonian-Messinian interval. Both ostracodes and benthic foraminifers reveal bathymetric faunal mixing of littoral, neritic, and bathyal species, and deposition at lower middle bathyal (1000-1500 m) or greater depths. A predominance of well-preserved and articulated carapaces in some of the Navidad and Ranquil samples indicate their rapid deposition, which supports sedimentologic and foraminiferal evidence for downslope displacement via debris flows on the continental slope east of the Peru-Chile Trench. This phenomenon could also explain the presence of some reworked Oligocene ostracodes in the Lacui Formation. Our ongoing research includes descriptions of new taxa and range extensions for previously described species. Such data will enable a better understanding of the Cenozoic evolution and paleogeography of the Southeast Pacific ostracode fauna.