The earliest clastic sediments overlying the Xiong'er volcanic rocks: Implications for the Mesoproterozoic tectonics of the southern North China Craton

Xiong'er volcanism and the accompanying sedimentation that occurred along the southern margin of the North China Craton (NCC) are thought to be related to the breakup or outgrowth of the Columbia supercontinent. A series of conglomerates, pebbly sandstones, coarse- to fine-grained sandstones, siltstones, and argillaceous rocks that comprise the Bingmagou Formation unconformably overlie the Paleoproterozoic Xiong'er volcanic rocks, which themselves are unconformably overlain by Mesoproterozoic sediments (Wufoshan and Ruyang Groups) within the southern margin of the NCC. The Bingmagou Formation is considered to be one of the oldest known clastic deposits, providing information on tectonic evolution subsequent to the Xiong'er volcanism. These rocks comprise a fan delta facies sequence and can be divided into fan delta plain, fan delta front, and pro-fan delta subfacies. Detrital zircons from the formation reveal the presence of two major age peaks at ca. 2700 Ma and 2500 Ma, and one minor age peak at ca. 2100 Ma; indicative of an NCC basement provenance. Samples from the Ma'anshan Formation (Wufoshan Group) yield a major age peak at ca. 1850 Ma, a minor peak at ca. 2500 Ma, and include several younger ages between ca. 1698 Ma and 1798 Ma. These ages are indicative of progressive evolution of provenance between the Bingmagou Formation and the overlying Ma'anshan Formation. The geochemistry of Bingmagou Formation sediments is indicative of felsic source rocks with arc-like affinities, which is markedly distinct from the upper groups. Sedimentary facies, regional unconformities, and detrital zircon data may indicate an uplift in the source area.