In northeastern Argentina the Holocene (ca. 2500 6000 C-14 yr B.P.) benthic marine molluscan fauna from the Cerro de la Gloria Member of the Las Escobas Formation represents a higher sea-level stand (approximately 4-5 m above m.s.l.) than the present one and belongs to an original shallow water environment. Most of this fauna (48%) belongs to the Argentine Zoogeographic Province while part of it (12%) is shared with the Magellanian Province. The rest of the taxa are cosmopolitan (5%) or belong to the Caribbean, Antillean and Brazilian provinces (35%). The latter are considered stenothermic warm-water indicators which in the present northeastern marine shelf of Argentina are scarcer (6-14%), most of them ranging from the Antilles to southern Brazil or northeastern Uruguay. It is a thermally anomalous molluscan fauna which is a consequence of local coastal palaeogeography and global mid-Holocene climatic change. On that basis a higher sea-water temperature during the mid Holocene is inferred, probably due to a stronger influence of the Brazil Current which could have extended farther south- and westwards during the Hypsithermal. The disagreement between the data presented here and the micropalaeontological data is still a problem to be solved, likely through critical systematic revisions of the foraminiferids and ostracods not included in this paper.
