Grain-size components of sediments in the Northern Jiangsu Coastal Plain and its paleoclimatic implications

The analysis of sediment grain-size characteristics enables the interpretation of sediment provenance, depositional environments, and paleoclimatic records. This study examines sensitive grain-size components indicative of paleoclimatic variations and associated climatic evolution through the analysis of grain-size composition in sediments from borehole JS1, located in the Northern Jiangsu Coastal Plain and dating from the late Middle Pleistocene onward, using principal component analysis, frequency distribution curves, and the Sahu discrimination method. The results show that the sediments are predominantly governed by two principal factors: grain-size components 0.178-17.18 μm (F11) and 18.86-39.78 μm (F3). Variations in F3 content exhibit cyclicity consistent with glacial/interglacial rhythms, reflecting broad global climate patterns. The vertical distribution profile of F11 closely matches the paleomagnetic record from Zhenjiang, supporting its use as a proxy for East Asian Summer Monsoon intensity. A comparative analysis reveals that the distribution curves of the sensitive components F11 and F3 record two major winter monsoon events during the MIS 7 and MIS 5 interglacials, as well as one pronounced East Asian Summer Monsoon event during MIS 3. Moreover, Mann-Kendall abrupt change-point analysis identifies two significant climatic shifts: an abrupt intensification of the East Asian Summer Monsoon around 34 ka and a marked transition to a warmer climate at approximately 4.3 ka.