Quaternary stratigraphy and paleoenvironmental evolution of the Ningbo Coastal Plain revealed by core Z02

Abstract

The Quaternary sediment in the Ningbo Coastal Plain was the deposit due to sea-land interaction, which recorded information of past climate changes. The region is therefore an ideal area to study paleoclimate changes and sedimentary characteristics. We determined the stratigraphic division and paleoenvironmental evolution based on ¹⁴C and paleomagnetic dating, along with detailed analyses of lithology, pollen assemblage, foraminifera and ostracodes assemblage, and grain size of sediment in core Z02 located in the southeastern Ningbo Coastal Plain. The results showed that the boundary between the Holocene and Upper Pleistocene in the core Z02 record was at 30.5 m, the boundary between the Upper and Middle Pleistocene was at 82.65 m, and the boundary between the Quaternary and Lower Cretaceous was at 90 m. The Middle Pleistocene section of the core contained few sediments, while the Lower Pleistocene section was completely missed. During the late Pleistocene, the hydrodynamic conditions experienced energy levels of medium to medium low to medium, and sedimentary facies changed from alluvial lake to overbank to river to lake to alluvial lake to lake to overbank. During the Holocene, the hydrodynamic changes experienced energy levels of medium low to low to medium, and the sedimentary facies changed from shoreland to shallow sea to shoreland lake. The Ningbo Coastal Plain had experienced tectonic uplift, weathering and erosion stage in the Early and Middle Pleistocene, from warm and humid to dry in the Late Pleistocene, and from warm and humid to dry and cool in the Holocene, as revealed by the core Z02 record. This study provided useful information in investigating past environmental changes in the subtropical coastal region of eastern China.

Keywords: Ningbo Coastal Plain; Quaternary stratigraphy; foramini-fera; grain size; ostracoda; paleoenvironmental evolution; pollen.