Tectonostratigraphy and provenance analysis to define the edge and evolution of the eastern Wuyi-Yunkai orogen, South China

Abstract

Copyright © Cambridge University Press 2017 We report three Palaeozoic sedimentary successions in northeastern South China that display markedly different tectonostratigraphic characteristics: the Jiangshan section exhibits an angular unconformity between the Upper Ordovician and Carboniferous stratra; the Shuangming section exhibits a disconformity between the lower Silurian and Upper Devonian strata; and the Xinqiao section exhibits a disconformity between the upper Silurian and Upper Devonian strata. The Shuangming and Xinqiao sections are interpreted to represent the remnant Nanhua foreland basin, whereas the Jiangshan section is in the fold-and-thrust zone of the Wuyi-Yunkai orogen. The Lizhu-Changshan thrust fault in between is interpreted to be the frontal thrust and the boundary of the orogen. Detrital provenance analysis of the Ordovician–Devonian sandstones from the Shuangming and Xinqiao sections shows that the Ordovician–Silurian, mid- to late-orogenic sandstones contain dominantly 860–780 Ma zircon populations and subordinate 2.5 Ga, 1.89–1.78 Ga, 980–950 Ma, 630–540 Ma and 430 Ma populations, indicating nearby sources including the early Neoproterozoic Sibao orogen, inverted Neoproterozoic rift basins and related plutons, recycled Ediacaran–Cambrian strata and, increasing with time, exposed Cathaysia basement and minor syn- to late-orogenic plutonic intrusions. The Devonian post-orogenic sandstones exhibit a dominant 440 Ma population with minor 2.5 Ga, 1.89–1.78 Ga, 860–780 Ma and 630–540 Ma populations, suggesting a dominant contribution from now widely exposed, mid- to late-orogenic plutonic intrusions (with or without contributions from rare volcanism of similar ages) in a residual topographic high SE of the Lizhu-Changshan fault. This residual topographic high of the Wuyi-Yunkai orogen had completely perished by early Carboniferous time, c. 60Myr after the end of the orogenic event.