Global climate change drove terrestrial ecosystem evolution during the late Paleocene-middle Miocene in the Lanzhou Basin, northeast Tibetan Plateau

Abstract

In this paper, we present organic carbon isotope records from continental sediments spanning the late Paleocene-middle Miocene (57.9–15.0 Ma) in the Lanzhou Basin, northeastern Tibetan Plateau to investigate terrestrial ecosystem-response to global climate change. The continuous sediment δ13CTOC values that we obtained range from −27.83‰ to −20.05‰. Combining these data with the sediment C/N ratios and n-alkane distribution, we infer that the major source of sediment organic matter was terrestrial C3 plants. Furthermore, we note that both sediment δ13CTOC and δ13Cn-alkanes values gradually become more positive from 57.9 to 26 Ma and then become relatively more negative from 26 to 15 Ma. These δ13C values vary closely with global temperature changes. We propose that global temperature controlled δ13C values with cooler conditions resulting in less rainfall in inland Asia, and vice versa. Therefore, mainly driven by the global temperature, the regional climate in the Lanzhou Basin gradually changed from warm-wet to cold-dry conditions during 57.9–26 Ma, and the climatic conditions became warmer and wetter again after 26 Ma. This long-sequence terrestrial ecologic environment study obtained from the northeast Tibetan Plateau powerfully demonstrates the first-order role of global climate in regulating the long-term evolution of regional environment.