Episodic volcanic eruption and arid climate during the Triassic-Jurassic transition in the Qiangtang Basin, eastern Tethys: A possible linkage with the end-Triassic biotic crises

Paleoenvironmental Conditions and Shale Oil Potential of the Carboniferous Ha’erjiawu Formation in the Santanghu Basin, NW China

“…Hence, the paleoclimatic conditions can be deduced from the elemental composition of sedimentary rocks [48][49][50]. For example, the utilization of Ga/Rb, Sr/Cu, and K 2 O/Al 2 O 3 ratios as geochemical proxies in shales has long been employed to reconstruct the climatic conditions in geologic history [46,[50][51][52]. Generally, a high Ga/Rb ratio (>0.25) and low K 2 O/Al 2 O 3 ratio (<0.2) suggest intense chemical weathering associated with warm and humid climatic conditions, whereas a low Ga/Rb ratio (<0.25) and high K 2 O/Al 2 O 3 ratio (>0.2) indicate weak weathering linked to dry and cold climatic conditions [46].…”

“…Generally, a high Ga/Rb ratio (>0.25) and low K 2 O/Al 2 O 3 ratio (<0.2) suggest intense chemical weathering associated with warm and humid climatic conditions, whereas a low Ga/Rb ratio (<0.25) and high K 2 O/Al 2 O 3 ratio (>0.2) indicate weak weathering linked to dry and cold climatic conditions [46]. The Sr/Cu ratio ranging from 1.3 to 5.0 is indicative of a humid and warm climate, whereas a Sr/Cu ratio exceeding 5.0 suggests an arid climate [52]. In this study, the geochemical proxies reveal that the majority of samples from the Ha'erjiawu Formation black shales were deposited under warm and humid climatic conditions, while a minority of samples were formed in dry and cold climatic conditions (Figure 5).…”