Evidence of climatic variations in Upper Pleistocene and Holocene sediments from the Lagoon of Venice (Italy) and the Yellow Sea (China)

Abstract

The effects of global climatic changes that occurred since the last Quaternary glaciation are recognizable in the stratigraphic sequences from several coastal zones in different locations around the world. The paleoevolution of the Northern Adriatic Sea and the Yellow Sea during the last 25,000 years has been characterized by several similar episodes of climatic changes. We report on the effects of climatic changes on the mineralogical composition and textural characteristics of clay and sand sedimentations in these paleoenvironments that are geographically far apart, correlating regional paleoclimatic changes with the mineralogical composition variations of sand and clay sequences. The mineralogical investigation has evidenced an increase of Quartz and Feldspar percentages and a decrease of Calcite and Dolomite during colder periods. Two depositional events, the hard clay layers and the cemented sand formations, that carry the imprints of the climatic conditions during their diagenesis are here reported and described. The hard clay layers represent the last continental sedimentation deposited during the Upper Pleistocene. The compactness of these clay layers is probably due to a long exposure to a cold and very dry climate. The water inside cemented sands studied were found under and outside of the Venice Lagoon and are similar to the beachrock formations presently found in tropical regions in intertidal zones. These cemented sands are remnants of ancient shorelines and witnesses of warm climate events.