Fine-scale provenance variability during the initial Cambrian transgression on the peri-Gondwana margin: Detrital zircon geochronology of the basal Taebaek Group, eastern North China Platform

Abstract

Extensive detrital zircon U-Pb data, resolved at fine spatial and temporal scales, provide detailed information on how sediment sources and dispersal systems evolved throughout platform development. Regional scale provenance analysis is conducted from the Cambrian basal Taebaek Group (the Jangsan, Myeonsan, and Myobong formations), Taebaeksan Basin in the eastern margin of the North China Platform using detrital zircon geochronology (41 samples, 1762 analyses) to reveal spatial and stratigraphic variability of the age spectra. The integrated data are classified into three groups: Group 1 (>1700 Ma, double peaks at ∼ 2.50 Ga and 1.87 Ga, from the Yeongnam Massif); Group 2 (1700–575 Ma, from Gondwana or other sources in the Sino-Korean Craton); Group 3 (youngest clusters at ca. 500 Ma, high Th/U ratios, from an outboard arc). The Jangsan Formation consists mainly of Group 1 zircons. The Myeonsan Formation contains groups 1 (83 %) and 3 (15 %), with minor Group 2. The Myobong Formation is dominated by groups 2 (72 %) and 3 (7 %) in the western/southern basin, but retains groups 1 (96 %) and 3 (2 %) in the northern/eastern part. Basal coarse-grained units were primarily sourced from adjacent basement rocks without ex-situ sediments. With ensued transgression, these sources were submerged, shifting provenance to upland areas and the outboard arc. Subsequent base-level rise led to the rapid influx of fine-grained sediments from outboard sources from Gondwana or other Sino-Korean sources, causing abrupt detrital zircon changes in the low-gradient western/southern basin. In contrast, the northern/eastern basin retained a consistent local basement signature, even in fine-grained deposits. These fine-scale variations likely reflect the interplay of topographic changes and global marine transgression. These, together with stratigraphic and sedimentological data, lead to a better understanding of the early-stage basin-filling history of the Taebaeksan Basin in the eastern North China Platform.