Sunday, December 20, 2015

Sino-Korean Block was Located at the Northern Margin of East Gondwana Across the Ediacaran/Cambrian Boundary

Detrital zircon geochronology and Nd isotope geochemistry of the basal succession of the Taebaeksan Basin, South Korea: Implications for the Gondwana linkage of the Sino-Korean (North China) block during the Neoproterozoic–early Cambrian


Lee et al


The paleogeographic configuration of continental blocks around East Gondwana during the Neoproterozoic–early Cambrian is controversial. This study reports the U–Pb ages of detrital zircons and Nd isotopic composition of the Neoproterozoic–early Cambrian succession developed on the Precambrian basement in South Korea, which formed the southeastern portion of the Sino-Korean block (SKB) in its present configuration. Three stratigraphic units are addressed in this study: the Neoproterozoic Jangsan, early Cambrian Myeonsan, and early–middle Cambrian Myobong Formations. Both the Jangsan (white to pink quartz sandstone) and Myeonsan (dark gray ilmenite-rich sandstone/shale) formations are barren and are unconformably and conformably overlain, respectively, by the dark gray, fossiliferous fine-grained Myobong Formations. The Jangsan and Myeonsan Formations contain zircons with Archean–Paleoproterozoic ages, indicative of detritus derived from the local Precambrian basement. In contrast, the Myobong Formation is dominated by Mesoproterozoic to Neoproterozoic zircons, which are not represented in the local Precambrian basement. The Sm–Nd model ages of the Myobong Formation are younger than those of the underlying strata, indicative of significant changes in provenance during the deposition of this formation. Comparison with coeval sediment having Gondwana signatures in the southern margin of the SKB and the Tethyan Himalayan terrane strongly suggests that the Myobong Formation was derived from orogens in East Gondwana. The results of this study reveal that the timing of the Myobong Formation deposition marks the onset of a sedimentation episode on the southeastern margin of the SKB, which was related to the emergence of a vast source province in East Gondwana, possibly aided by the Cambrian transgression onto the SKB. In comparison with the published literature, we argue for the paleogeographic continuity of the SKB with the northern margin of East Gondwana, possibly between northwestern Australia and northeastern India during the Neoproterozoic–early Cambrian.

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