Sedimentary characteristics and sedimentary-tectonic responses of the Sihong segment of Tan-Lu fault zone since the Late Mesozoinc: A case study of borehole SHJ02

The evolution of sedimentary basin since the Late Mesozoic in Sihong and surrounding areas of Jiangsu Province and the formation of present landform are mainly controlled by the multi-stage tectonic activities in the Sihong segment of Tan-Lu fault zone. The fluctuation characteristics of sedimentary basement and deposit accumulation process under the control of neotectonic movement are completely recorded by the Neogene-Quaternary loose sediments. Taking the borehole SHJ02 in Sihong segment for example, the paleogeographic environment and tectonic evolution characteristics are discussed based on the analysis of borehole core features and stratigraphic sequence division. The depth of borehole SHJ02 is 246.00 m, revealed strata including the Quaternary(buried depth of 0～47.43 m), Neogene(47.43～239.52 m), Late Cretaceous red bed(239.52～242.70 m)and Early Cretaceous volcanic rock(more than 242.70 m)from top to bottom. The characteristics of Late Mesozoic-Cenozoic stratigraphic sequences and sedimentary framework show the tectonic evolution processes as the deposition of Late Cretaceous fault depression, Paleogene uplift and denudation, fluvial-lacustrine sediments in the Neogene extensional environment, and rapid uplift under the background of late Quaternary compression in the Sihong segment of Tan-Lu fault belt. The rapid transformation of sedimentary systems such as the Neogene-Quaternary channel evolution and frequent alternations of fluvial-lacustrine facies is a response to the neotectonic movement in the area.