QUANTITATIVE ANALYSES OF LATEST QUATERNARY STRATIGRAPHY FROM CORES USING MODERN MEIO AND MACROBENTHIC INVERTEBRATES: A PRACTICAL APPROACH TO FACIES INTERPRETATION

Latest Quaternary coastal deposits are not always exposed on the surface and in such cases can be directly investigated only by means of wells and/or trenches. This report describes how benthic ostracod and mollusk analyses performed on a network of cores enabled a detailed facies characterization of the Late Pleistocene-Holocene successions buried beneath the modern Po Delta and Arno plains (Italy). On the basis of relative abundance categories, key extant mollusk and ostracod taxa commonly retrieved from cored deposits are illustrated and discussed as fundamental facies discriminators. In addition, this report summarizes the major biofacies associations that were formed during the present interglacial in the targeted successions. Some biofacies attributions are straightforward, but others are ambiguous. Where evaluation of individual facies is difficult, the joint consideration of ostracods and mollusks may contribute important information about depositional environments. Finally, thorough the application of detrended correspondence analysis (DCA) to the mollusk part of the dataset, an interpretable paleobiological pattern emerges despite taphonomic and sedimentological overprints. Amongst all possible mechanisms that may play a role in ‘shaping’ macrofossil distribution, the ecological signal driven by salinity represents the most prominent factor controlling the composition of mollusk associations in back-barries environments, whereas water depth appears to be the main driver or the macrofaunal turnover in marine coastal environments.

These results support the utility of the stratigraphic paleobiology approach as a fruitful strategy for investigating stratigraphic variations in faunal content from coastal setting and reconstructing the palaeoenvironmental gradients that shape the composition of marine communities.