Paleogene sediment provenance and paleogeographic reconstruction of the South Yellow Sea Basin, East China: Constraints from detrital zircon UPb geochronology and heavy mineral assemblages

Highlights

• The source-to-sink system was first analyzed in the South Yellow Sea Basin.

• The tectonic significances on the Paleogene provenance evolution were revealed.

• The paleogeographic evolution was reconstructed in the South Yellow Sea Basin.

Abstract

This study presents new zircon UPb geochronological and heavy mineral assembly data from Paleogene rocks to constrain the provenance and paleogeographic evolution of the South Yellow Sea Basin (SYSB), East China. Heavy minerals are mainly ilmenite, garnet, epidote, zircon and pyrite. Detrital zircon ages from the Paleocene Funing to Eocene Sanduo Formations can be grouped into five major populations: 100–300 Ma, 400–500 Ma, 600–900 Ma, 1700–2100 Ma and 2300–2700 Ma. Paleocene Funing sediments mainly contain zircons of ~220 Ma, ~760 Ma, ~1850 Ma and ~ 2500 Ma, consistent with zircons from the Daibie-Sulu Orogen, the South China Craton, and the North China Craton. Lower Eocene Dainan sediments show different detrital zircon ages and heavy mineral assemblages, indicating a change in sediment sources. The Daibie-Sulu Orogen served as a major source for the North Depression. Sediments of the southern segment of the South Depression were derived mainly from the Daibie-Sulu Orogen and the North China Craton from the west, while sediments of the northern segment of the South Depression received a southwestward supply from the Central Uplift with detrital zircon peak ages of ~440 Ma. Detrital zircon age spectra of Sanduo samples resemble those of Dainan samples with peaks at ~120 Ma, ~220 Ma, ~440 Ma, ~800 Ma, ~1850 Ma and ~ 2500 Ma, suggesting that they share common sources. The results allow the reconstruction of an updated paleogeographic model for the Paleogene of the South Yellow Sea Basin.

Introduction

Detrital zircon UPb ages and heavy mineral assemblages can be used to reveal source-to-sink links between sedimentary basins and their sourcing orogens (Yang et al., 2013; Lee et al., 2017; Dillinger et al., 2018; Li et al., 2018b; Su et al., 2018; Fossum et al., 2019; Fyhn et al., 2019; Gladkochub et al., 2019; Yang et al., 2019). Provenance changes may be related to inferred tectonic movements, postorogenic denudation or tectonic subsidence (Shen et al., 2012a, Shen et al., 2012b; Li et al., 2018b).

The South Yellow Sea Basin (SYSB) is an important offshore petroliferous basin in East Asia (Yi et al., 2003; Yao et al., 2008; Liu et al., 2018). It is located in the offshore area of the Lower Yangtze Block (Fig. 1), filled with pre-Indosinian marine carbonate, Mesozoic and Cenozoic continental deposits (Yao et al., 2008; Zhang et al., 2015; Pang et al., 2017, Pang et al., 2019). It can be subdivided into the North Depression, Central Uplift, South Depression and Wunansha Uplift from north to south (Yao et al., 2008) (Fig. 2). By the end of 2018, 30 wells had been drilled in the SYSB, with 13 wells in the North Depression (Shinn et al., 2010), 2 Continental Shelf Drilling Program (CSDP) wells in the Central Uplift (Guo et al., 2017; Cai et al., 2019) and 15 wells in the South Depression. While the adjacent basins such as the Bohai Bay Basin and Subei Basin show great hydrocarbon potential, no commercial discovery has been made in the SYSB (Fig. 1). These basins are located in different tectonic units and controlled by contrasting stress fields (Fig. 1). For example, the Bohai Bay Basin belongs to the North China Craton, and experienced NW-SE extension in the north, N-S extension in the central part and NW-SE extension in the south. However, the SYSB belongs to the Yangtze Block/ South China Craton and experienced NW-SE extension. Previous studies on the SYSB mainly focus on (1) investigating the petroleum system (Yoon et al., 2010; Cai et al., 2019; Pang et al., 2019), (2) tectono-thermal evolution of the Central Uplift, the Gunsan Basin and other parts of the SYSB (Yi et al., 2003; Shinn et al., 2010; Yao et al., 2010; Pang et al., 2017, Pang et al., 2018, Pang et al., 2019; He et al., 2019) and (3) sedimentary characteristics of the Central Uplift (Guo et al., 2017; Liu et al., 2018; Cai et al., 2019; Pang et al., 2019). There is a lack of studies on the sediment provenance of the SYSB, especially regarding Paleogene siliciclastic rocks.

The SYSB has undergone post orogenic intracontinental rifting (K₂t-E) and post rifting (N-Q) (Ren et al., 2002; Yao et al., 2010). Paleogene strata in the North Depression and South Depression consist of the Funing, Dainan and Sanduo Formations (Fig. 3). During the syn-rift stage (Paleogene), there were three regional tectonic movements, the Wubao, Zhenwu and Sanduo movements. Less is known about how the movements controlled the sediment provenance evolution spatially and temporally. Concerning the SYSB and adjacent area, UPb geochronology has been carried out in the Subei Basin on the Dainan sandstone and in the Gunsan Basin on the Cretaceous sandstone (Lee et al., 2017; Zhou et al., 2018; He et al., 2019). In contrast, detrital zircon UPb geochronology and heavy mineral research of Paleogene sandstones in the SYSB remain less explored, limiting understanding of the SYSB rift system evolution.

In this study, we present detrital zircon UPb ages and heavy mineral assemblages from the Funing Formation to the Sanduo Formation of the SYSB. When compiled with the published data, we are able to constrain the depositional age and provenance of these strata and refine the paleotopographic reconstruction of the SYSB during the Paleogene. The study of the rift system in the SYSB is of great scientific significance and will provide new evidence for tectonic evolution and paleogeography in East China.