(AGENPARL) – VENEZIA lun 19 giugno 2023 Speaker: Dr. Sebastian Richiano, CONICET Puerto Madryn

Titolo: Paleoclimate and paleoceanographical interpretations using bioerosion ichnodiversity patterns in the southern South-Western Atlantic at Patagonia, Argentina

The talk will be available via Zoom: https://unive.zoom.us/j/

Abstract:
Marine Late Quaternary skeletal concentrations from Argentina are rich in mollusks, extending more than 3,000 km between the Río de La Plata and southern Patagonia, where those formed during MIS11, 9, 7, 5 and 1 are the best preserved in the SWA. In this work we will analyze Pleistocene, Holocene and modern Patagonian deposits, where detailed field and laboratory observations carried out on bulk samples, allowed to identify a great variety of bivalve and gastropod taxa which testify an interesting history of paleoclimate- paleoceanographical-changes to present. In the molluskan fauna a great variety of bioerosion traces were identified (up to 15 ichnogenus) made by porifers, bryozoans, annelids, other gastropods and brachiopods. In general, the most characteristic traces are those produced by bryozoans, polychaetes and predatory gastropods. No strict correlation is evident between ichnodiversity patterns through time or latitude, but it is possible to observe a linkage to local oceanographical/biotic controls. In modern samples, most of the ichnotaxa were made by bryozoans, showing a general trend of higher bioerosion degree and ichnodiversity at higher latitudes. This pattern is controlled by sea surface temperature and productivity, as several ichnodiversity peaks for modern localities match with well constrained conditions (substrate, salinity, coastal fronts). Similarly, this applies for the Holocene. By contrast, not for the Pleistocene, when dissimilar conditions probably prevailed, especially during the Last Interglacial (colder waters richer in nutrients) as a response to different paleocirculation settings (winds, currents, ocean fronts). Some exceptions to this general pattern are observed at different localities, where local paleo-oceanographical conditions control the water-productivity levels affecting the bioerosional patterns (i.e. coastal fronts, upwelling currents, etc). In conclusion, the macrogeographical distribution of trace fossils, at least for Patagonia, could be used for interpreting the strong linkage between Earth history-climatic cycles-atmospheric-oceanic circulation patterns and Late Quaternary biotic responses.

Fonte/Source: http://www.unive.it/data/agenda/1/75898