Quaternary Tectonic Activity near the Qianliyan Island of Southern Yellow Sea

Many Quaternary folds and faults are identified on the seismic reflection profiles acquired in the adjacent areas of Qianliyan Island of southern Yellow Sea.The faults are mainly of reverse fault.The folds are mainly gentle and tilted,caused by fault activities.Most folds and faults occurred below a plane of unconformity between middle Pleistocene and its overlying upper Pleistocene.Some faults,such as Qianliyan fault,are late Pleistocene active fault.Many faults and folds were synsedimentarily developed in the lower Pleistocene and underlying strata,revealling rather strong tectonic activity,especially at the basin boundary where the faults even cut into the late Pleistocene stratum.The formation of folds and faults was attributed to the last tectogenesis of the Yellow Sea in middle Pleistocene,which maybe correspond to the Kunlun-Huanghe movement of Qinghai-Tibet plateau.At that time,the N-S striking horizontal stress drove the early-developed basin boundary faults reactive and further induced the NEE or E-W striking tectonic deformation in the overlying sedimentary layer.