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[Display omitted] • A dense seismic array deployed 18 days is used to image a 3D Vs model. • Three LVZs are revealed in the shallow crust beneath the Shiziyang Waterway area. • Three cross-cutting fault zones in the sedimentary basement are identified. • Two-stage differential fault movements dominated the opening of the Shiziyang Waterway. The Shiziyang Waterway, located in the northern continental margin of the South China Sea, has developed a complex fault system owing to the coupling action of the oceanic crust and continental crust. However, the geological structure in the shallow crust beneath the Shiziyang Waterway and the relationship between faults and waterway development are still unclear, resulting in difficulty in assessing the earthquake risk to the surrounding cities. In this study, based on a high-density short-period seismic array that was recently deployed around the Shiziyang Waterway, a high-resolution shear wave velocity model is inverted to as shallow as 4 km by the ambient noise tomography method. The results showed that at depths ranging from 0.2 to 4 km, three sets of low-velocity zones (LVZs), trending east–west, northeast, and northwest, are revealed, which are speculated to be the Shougouling fault (SGLF), Xinhui-Shiqiao fault (XSF), and Shiziyang fault bundle (SZYFb), respectively. The shear-wave velocity anomalies illustrate that the SGLF stopped extending east at the north endpoint of the Wenchong-Zhujiangkou fault (WZF). The two-stage differential vertical movements of the WZF, Nangang-Humen fault (NHF), and Hualong-Haioudao fault (HHF) dominated the opening of the Shiziyang Waterway. This study provides new seismological evidence of the opening process for the Shiziyang Waterway and reveals that internal fault activity dominated the development and evolution of the Pearl River Delta. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Detailed 15.3–1.8 Ma clay elemental geochemistry records for the northeastern Qaidam Basin are presented. • Long-term and persistent weakening of the chemical weathering intensity has occurred since the Middle Miocene. • Global cooling-related drying played a key role in the chemical weathering intensity. • Miocene uplift of the northern Tibetan Plateau might exert some influence on the weakened chemical weathering intensity at 12–8 Ma. Abstract Cenozoic basin sediments around the Tibetan Plateau are valuable archives that can be used to reveal long-term interactions among tectonics, climate and weathering. However, the reconstruction of silicate weathering histories in this tectonically active region is consistently hindered by the presence of frequently embedded conglomerate and sandstone in the long sedimentary sequences. Here, we present detailed geochemical compositions of the clay components of the sediments in the Huaitoutala section (ca. 15.3–1.8 Ma) of the northeastern Qaidam Basin to reconstruct the chemical weathering history of the catchment since the Middle Miocene. Major element ratio proxies reveal evidence of four stages of change: from ca. 15.3 to 12.6 Ma, in which the clay components are characterized by relatively high Chemical Index of Alteration (CIA) values (75–88, average = 81) but low mobile/immobile oxide ratios (e.g., K 2 O/Al 2 O 3 , Na 2 O/Al 2 O 3 and CaO/Al 2 O 3), thus indicating the occurrence of intense chemical weathering conditions; from ca. 12.6 to 6.6 Ma, in which decreasing CIA values, together with increasing mobile/immobile oxide ratios, suggesting that a long-term decrease in silicate weathering intensity occurred in the source area; from 6.6 to 2.6 Ma, in which the clay components in the sediments exhibit persistently low CIA values (66–81, average = 76.8) and high oxide ratios, which are indicative of mild to moderate chemical weathering; and since 2.6 Ma, in which the CIA values (64–80, average = 75.5) have continued to decrease with increasing oxide ratios, thus reflecting mild chemical weathering conditions. The geochemical proxy records demonstrate that the intensity of chemical weathering has continually decreased and that the Qaidam Basin has experienced continuous aridification since ca. 12.6 Ma. We suggest that Middle-Miocene global cooling-related drying has exerted a significant influence on the trend of decreasing chemical weathering intensity since ca. 12.6 Ma. In addition, the Late Cenozoic rapid uplift and exhumation of the NE Tibetan Plateau could have limited the time that the silicate rocks were exposed in the weathering profile prior to the deposition, which may have led to their weakened intensity of chemical weathering. [ABSTRACT FROM AUTHOR]

[Display omitted] • (La/Yb) N -Na 2 O/Al 2 O 3 plot can be used to identify analcime-bearing pyroclastic rocks. • Th/U-Rb/Sr plot may identify pyroclastic rocks deposited in reducing conditions. • Pyroclastic rocks in Lunpola Basin originated from ultrapotassic and adakitic magmas. • The west Lhasa terrane was dominated by mantle lithosphere detachment. • The east Lhasa terrane was characterized by lower crustal thickening. Tephrochronology provides a powerful tool to date and correlate the sedimentary sequence. However, the recognition of tuff and tuffinite in Cenozoic sequences is challengeable because of modification and alteration during diagenesis. In this contribution, we studied samples from the Cenozoic Lunpola basin on the central Tibetan Plateau to explore the potential provenance and distinction of pyroclastic materials from clastic sediments and to recognize the source-to-sink process of pyroclastic rocks and their deep geodynamic implications. The bulk mineralogical compositions and major and trace elements and Sr-Nd-Hf isotopic compositions of the pyroclastic rocks and clastic sediments in the Lunpola Basin were determined and compared with those of contemporary volcanic rocks in the Lhasa terrane. It is suggested that Th/U-Rb/Sr and (La/Yb) N -Na 2 O/Al 2 O 3 discrimination plots might be used to distinguish pyroclastic from clastic sedimentary rocks in terms of source, transportation and diagenesis. According to the trace element and Sr-Nd and Hf isotope signatures, the 23.5 Ma pyroclastic rocks in the Lunpola Basin may originate from the Xungba ultrapotassic magmatism, and the ∼ 21- ∼15 Ma pyroclastic rocks may have been supplied by corresponding adakitic magmatism. The spatial distributions of the ultrapotassic and potassic as well as adakitic volcanic rocks in the Lhasa terrane may reveal that the west Lhasa terrane mantle lithosphere was detached and the east Lhasa terrane lower crust was thickened along with the India-Asia plate convergence. [ABSTRACT FROM AUTHOR]

[Display omitted] • Paleoecological and paleohydrological changes in the Qaidam Basin occurred during the EOT. • Changes in CPI, ACL, Paq and L/H, indicating bacterial, algal and aquatic plants shrink , and terrestrial plants flourish. • δ2H 31 values were increased by 18.1‰, indicating a decrease in water vapor content and an increasingly arid climate. The Eocene/Oligocene transition (EOT) at ∼34 Ma has been considered the most prominent climatic cooling event in the Cenozoic Era. However, few organic biomarker studies have attempted to reconstruct relevant terrestrial ecological and hydrological responses to an age characterized by drastic temperature changes. This research aims to reconstruct the paleoecological and paleohydrological evolution of the Qaidam Basin (QB) on the northeastern Tibetan Plateau (NE TP) between 40.2 and 29.9 Ma, based on analyses of n -alkane chain length distributions as well as compound-specific hydrogen isotopic compositions (δ2H alk). Research showed the presence of a sequence of pronounced ecological and hydrological variations at 35.0–33.1 Ma, including: 1) a significantly decreased input of bacteria, algae and aquatic plants, allied with a markedly increased input of terrestrial plants, reflected in a significant increase in carbon preference index (CPI) and the average chain length (ACL) ratio, as well as an abrupt decline in the relative ratio of mid- to long-chain length homologue (Paq) values and the ratio of low- to high- molecular-weight n -alkanes (L/H); and 2) drier climatic conditions, reflected in an 18.1‰ increase in δ2H 31 values, as well as more positive hydrogen isotopic precipitation values (δ2H p). These features demonstrate significant paleoecological and paleohydrological changes in the QB in response to the drier and cooler climate during the EOT. [ABSTRACT FROM AUTHOR]

• The late Cretaceous–early Eocene paleoclimate of the Jianghan Basin was studied. • The salinity of the paleolake was mainly controlled by climate change. • The temporal differentiation of the evaporite deposits resulted from tectonics. • The widespread evaporites indicate an extremely arid climate during the Paleocene. • The climate became semi-humid during the early Eocene. The Jianghan Basin, Central China, contains a thick, continuous sequence of early Cenozoic evaporite-bearing deposits that provide a wealth of information about early Cenozoic climate change and evaporites accumulation in East Asia. However, the paleoclimatic history of the basin and its effect on the evaporites are largely unknown. We obtained a deep drill core (SKD1, 2346.5 m long) from the late Cretaceous to early Eocene evaporite-bearing deposits in the Jianghan Basin. Detailed analyses of the lithofacies, mineralogy and geochemistry of the core indicate that salinization and deepening of the lake occurred (corresponding to the Yuyang Formation to the lower Xingouzui Formation), followed by desalting and shallowing (corresponding to the upper Xingouzui Formation). Reconstruction of the spatiotemporal evolution of the evaporites in the Jiangling depression suggests a transition from semi-arid conditions in the late Cretaceous to extremely arid conditions in the initial stage of the Eocene. The climate then became semi-humid during the deposition of the upper Xingouzui Formation, indicating a monsoon or monsoon-like climate in East Asia during the early Eocene. The southward migration of the depocenter of the Jiangling depression, coupled with a warm and extremely arid climate, resulted in the precipitation of evaporites during the accumulation of the upper Shashi Formation and the lower Xingouzui Formation. These results indicate great potential for identifying potash resources within the subsag in the southern Jiangling depression. [ABSTRACT FROM AUTHOR]