Cenozoic stratigraphic correlation and the lower limit of Quaternary in Guanzhong Basin

Thick Cenozoic sediments in Guanzhong Basin provide excellent geological records for the study of the regional tectonics, sediment environment evolution and paleoclimate change.However, there are still controversies about the Cenozoic stratigraphic division and the lower boundary of Quaternary in Guanzhou Basin.Based on paleomagnetism and paleontology strata from drilling cores and outcrop sections, we reappraise and reestablish the Cenozoic strata framework in Guanzhong Basin.According to fluvial-lacustrine deposits and eolian red clay-loess sequences, the authors discuss the lower limit of Quaternary in Guanzhong Basin. Evidence from lithology, magnetostratigraphy, biostratigraphy and climate change supporting the lower limit of Quaternary strata should be confined to the boundary of "Yellow Sanmen" and "Green Sanmen" in the traditional Sanmen Formation or the boundary of eolian loess and red clay sediments around M/G boundary, and the paleomagnetic age is 2.6 Ma.Based on palaeomagnetic data of drilling cores, outcrops and previous literature, we revise the Cenozoic chronostratigraphic chart in Guanzhong Basin and amend or reallocate the ages of different strata from Eocene to Holocene.We propose that Neogene and Quaternary deposits in the Guanzhong Basin can be generally classified into two sets of different genesis sediments e.g.eolian and fluvial-lacustrine sequences.The eolian deposits can be extended to the Miocene period, which is older than previous conventional knowledge, and this Miocene eolian red clay sequences can be named as Duangjiapo Formation.This study is helpful to understand the formation and evolution of the sedimentary environment, paleoclimatic change, basin resource exploitation and geological engineering construction in Guanzhong Basin.