Preliminary study of Quaternary tectono-climatic cycles in China

Abstract

Major Cycle II This started in the middle part of the aggradation of Early Pleistocene lacustrine and fluviolacustrine beds (Nihewan, Yuanmou and Qiangtant Formations), and ceased with the deposition of the top part of these strata. During this cycle, the second glacial stage corresponding to the Shizishan glacial stage of the East Kunlun Mountains is essentially indicated by sporepollen assemblages and periglacial phenomena reflecting a cold climate. Until the second interglacial stage, or the late part of it, intense tectonic movements (also named Nihewan, Yuanmou and Qiangtang movements) occurred simultaneously all over the country, and interrupted the development of Early Pleistocene lakes. The timing is shown by magnetostratigraphy and began near the Gauss/Matuyama boundary and ended after the Olduvia event. Major Cycle I This began about 3.4 Ma ago when global climate became colder and continued to about 2.4 Ma BP corresponding more or less with the entire Gauss Epoch. The moraines and the fluvioglacial or periglacial sediments representing the first glaciation rest mostly unconformably on bedrock including Pliocene sequences, with partial conformity in places. Overlying fluviolacustrine beds are generally in overlapping or transitional relationship with them. For example, it can be seen that the Sammen movement marking the end of Major Cycle I led to a break in the sedimentation in the ancient Sanmen Lake of the Sanmenxia area on Yellow River (Cao et al., 1983). several boundaries between the various cyclothems stratigraphically and geomorphologically. Using magnetostratigraphy and climatostratigraphy the boundaries between three major cycles can be established as follows.