Tectono-stratigraphic framework and evolution of East Junggar Basin, Central Asia

Abstract

The late Paleozoic development of the East Junggar Basin and adjoining mountain belts was critical to the construction of the larger Central Asian Orogenic System, yet the structural framework of basement rocks and overlying strata of the basin and their spatio-temporal relationship with adjacent thrust-bounded ranges remain poorly constrained. In this study, we conducted reflection seismology and compiled existing geologic observations of the East Junggar Basin and adjacent Bogda Shan to the south and Kelameili Shan to the north to construct cross sections depicting the tectono-stratigraphic framework and evolution of the region. Our work shows that Carboniferous–Permian strata overlying basement rocks in the East Junggar Basin occur in structural uplifts and depressions and feature at least five major unconformities. The structure of the East Junggar Basin is characterized by: (1) horsts and grabens involving basement rocks and overlying Carboniferous–Jurassic strata; (2) series of stratigraphic depressions marked by Jurassic–Cretaceous strata; and (3) a south-dipping monocline in uppermost Neogene–Quaternary strata. Mesozoic–Cenozoic strata are absent along the northern margin of the East Junggar Basin at the Kelameili Shan. Strata are generally older from the Kelameili Shan to the northern East Junggar Basin where Devonian–Carboniferous strata are thrust southward over younger strata. In contrast, thicker sequences of Cretaceous–Quaternary strata are present in the southern portion of the East Junggar Basin. Strata of the East Junggar Basin were deposited in a foreland depression formed in the footwall of a leading, north-directed thrust of the Bogda Shan. The overall tectono-stratigraphic framework of the East Junggar Basin is a product of tectonic activity varying in time and space along the northern and southern basin-mountain interfaces since the late Paleozoic.