The South Yellow Sea is an important sink for sediments delivered by the Yellow and Yangtze rivers in East Asia. We conducted a high‐resolution geochemical analysis on the bulk sediments retrieved from a marine drill core (CSDP‐1) using the method of X‐ray fluorescence (XRF). Our results show large geochemical variations along the core. As demonstrated by linear correlations along with the Al‐Si link in a compositional principal component analysis (PCA), the variations in elemental ratios among Al, K, Zr, Ba, and Si are primarily controlled by sediment sorting effects. A closer examination indicates a gradual shift of sediment provenance from the Yangtze to the Yellow River catchment in the core. With the help of a fuzzy c‐means cluster analysis on elemental ratios of Al/Si, Al/Ti, K/Si as well as the chemical index of alteration (CIA), the timing of a major provenance change in the core is narrowed down to 1.5–1.7 Ma. This timing corresponds to a major seismic and sedimentary boundary (T2) in the Yellow Sea Basin and coincides with the onset of fluvial terrace deposition and incision in the middle and upper reaches of the Yellow River. As a result, we argue that the major provenance change derived from geochemical variations in the Yellow Sea sedimentary basin can be linked with the integration of the modern Yellow River. The provenance change is likely caused by a coupling between regional tectonic deformation and the Asian summer monsoon enhancement in the early Pleistocene.
Linking marine sinks to potential terrestrial sources is one of most intriguing but challenging aspects of sediment source-to-sink studies. In this study, we analyzed 23 zircon samples (3271 filtered best ages) from surface sediments of the east China seas (ECSs) that cover a large portion of the Bohai Sea, Yellow Sea, East China Sea to part of the northeastern South China Sea. The results of U-Pb age distributions exhibit variable signatures in different seas. The Bohai Sea is characterized by 4 age populations at 203–286 Ma, 383–481 Ma, 1830–1940 Ma and 2480–2548 Ma, whereas the southern Yellow Sea and the East China Sea are featured by 5 age populations at 176–223 Ma, 383–481 Ma, 732–830 Ma, 1830–1940 Ma and 2480–2548 Ma. We propose that the presence or absence of the population of 732–830 Ma in the Yangtze Craton (YC) and the North China Craton (NCC) is a possible geochronological signature to distinguish zircon grains derived from the two source regions. Furthermore, on the basis of multidimensional scaling (MDS), U-Pb ages in the sediments of the Bohai Sea, East China Sea and the Taiwan Strait could be correspondently linked to those of the Yellow River, the Yangtze River and Taiwan rivers. The good linkages support the view that U-Pb age distributions of detrital zircons in the margin seas are mainly controlled by fluvial discharges, and ultimately, by the tectonic history of the corresponding source regions. Using a sediment forward mixing model, we obtained the relative sediment contributions and spatial variations of five most important river discharges in the region. The mixing results suggest that the major rivers in the region, i.e., the Yangtze and the Yellow Rivers, are the dominant sediment contributors to the continental margin, and their mixing coefficients could be used to infer relative sediment budgeting. In addition, spatial variations in mixing coefficient in the East China Sea indicate that sediment mixing and partitioning processes in the marine depositional environment have played a part role in propagating the provenance signals as a result of interaction of oceanic currents and tides. The combined method between provenance analysis and mixing modeling provides a feasible way to appreciate sediment budgeting in the geological past.
The Central Asian Orogenic Belt is complex and little understood in its geotectonic history. Here, we apply a new approach to conclude on the paleogeography of major Mongolian terrains using small skeletal fossil assemblages and a combined analysis of U‐Pb ages and typology of detrital zircons. We document a new Cambrian Stage 3 fauna from the Telmen Block located between the Dzhabkan and Tuva‐Mongolia cratons. Based on a hierarchical cluster analysis of 35 blocks, we observe the most robust biogeographic relationship between Telmen and Kusnetzk Alatau and between Tuva‐ Mongolia and Lake Zone. These results challenge the view that these cratons were assembled during the Ediacaran/Cambrian in a single ribbon‐shaped paleocontinent. Detrital zircon U‐Pb ages indicate a unique age population at ∼516 Ma at Telmen derived from I‐type granitoids, neither seen on Dzhabkan nor Tuva‐Mongolia cratons supporting their different tectonic evolution within the Palasian Ocean after the breakup of Rodinia.
The Bogeda Shan (Mountain) is in southern part of the Central Asian Orogenic Belt (CAOB) and well preserved Paleozoic stratigraphy, making it an ideal region to study the tectonic evolution of the CAOB. However, there is a long-standing debate on the tectonic setting and onset uplift of the Bogeda Shan. In this study, we report detrital zircon U-Pb geochronology and whole-rock geochemistry of the Permian sandstone samples, to decipher the provenance and tectonic evolution of the West Bogeda Shan. The Lower-Middle Permian sandstone is characterized by a dominant zircon peak age at 300–400 Ma, similar to the Carboniferous samples, suggesting their provenance inheritance and from North Tian Shan (NTS) and Yili-Central Tian Shan (YCTS). While the zircon record of the Upper Permian sandstone is characterized by two major age peaks at ca. 335 Ma and ca. 455 Ma, indicating the change of provenance after the Middle Permian and indicating the uplift of Bogeda Shan. The initial uplift of Bogeda Shan was also demonstrated by structural deformations and unconformity occurring at the end of Middle Permian. The bulk elemental geochemistry of sedimentary rocks in the West Bogeda Shan suggests the Lower-Middle Permian is mostly greywacke with mafic source dominance, and tectonic setting changed from the continental rift in the Early Permian to post rift in the Middle Permian. The Upper Permian mainly consists of litharenite and sublitharenite with mafic-intermediate provenances formed in continental island arcs. The combined evidences suggest the initial uplift of the Bogeda Shan occurred in the Late Permian, and three stages of mountain building include the continental rift, post-rift extensional depression, and continental arc from the Early, Middle, to Late Permian, respectively.