Salt Rhythm Characteristics and Paleoclimatic Significance of Pukou Formation (2nd Member) in Yanghuai Section of Huai'an Salt Basin,Northern Jiangsu
Salt lake sediments,commonly characterized by its multi-stage formation and continuity,are important in paleoenvironment reconstruction. The salt rhythms of different scales show different paleoclimatic changes in their respective scale. The Pukou Formation is the main saliniferous sequence in the Huai'an basin,and studying the rhythms developed in the rock record can reveal the paleoclimatic characteristics. Based on core observation and mineral composition analysis,we have determined the salt rhythms and the vertical lithological variations. The paleoclimatic indications by the rhythms have revealed short-term paleoclimatic changes. The salt rhythms can be divided into five cycles,and each cycle is identified by a complete sequence of mudstone-glauberite- bearing salt rock-salt rock-glauberite-bearing salt rock. The extensive development of warm saline mineral (e. g. glauberite) indicates the paleoclimate was warm and arid. This study reconstructed the paleoclimate at IV-order rhythm,which was characterized by frequent arid-wet climatic fluctuations,despite dominated by arid climate. The thickness of rhythms generally reflects the fluctuation frequency.