Detrital zircon geochronology reveals source-to-sink relationships in the Pearl River Mouth Basin, China

Abstract

A major challenge in provenance and source-to-sink analysis is deciphering intrabasinal versus extrabasinal sediment sources and processes. This issue is well-illustrated by the Paleogene Pearl River Mouth Basin (PRMB), whose provenance reflects a combination of sediments eroded from the Cathaysia Block (CB), southeastern China, and from intrabasinal structural highs. Here we use new detrital zircon UPb ages from Paleogene formations in seven boreholes, southern PRMB, to investigate such local versus regional influences on provenance. Detrital zircons from the upper Eocene-lower Oligocene Enping Formation are dominated by Jurassic-Cretaceous ages, with a 125–110 Ma age-cluster, absent in modern river data from the CB and diagnostic of intrabasinal sediment sources. In the northern part of the basin, Mesozoic-dominated zircon age-spectra give way to Paleozoic and Precambrian grains, a pattern also recognized for the late Oligocene Zhuhai Formation, suggesting a major change in provenance likely related to extrabasinal influence from the CB. The age spectra for these samples are most similar to the northeastern Pearl River, narrowing this region as the most likely source. Spatial analysis of the results suggests that during deposition of the Enping Formation, sediment transport was not uniform and that the basin's architecture strongly influenced provenance, with structural highs acting as both sediment sources and barrier to sediment transport from the CB; whereas structural lows, with clear extrabasinal influence, functioned as sediment transport corridors. Such spatial differences are lost in samples from the Zhuhai Formation and their provenance suggests that the paleo-Pearl River and tectono-climatically driven surface processes in the CB dominated deposition thereafter.