Jurassic sediments geochemical constraints on provenance, weathering process, and palaeoclimate variation of the north margin of Qaidam Basin, north‐eastern Tibetan Plateau

Abstract

The Jurassic sequence in the northern Qaidam Basin can be represented by the lower coal‐bearing swamp‐lacustrine sediments unit and the upper reddish clastic deposits suite, which recorded dramatic transition of deposit environment changes. Whole‐rock geochemical data of this succession in Dameigou profile were used to reconstruct the provenance and chemical weathering history. Based on the major element discrimination diagrams, trace element ratios and chondritenormalized REE patterns, most sediments were derived from a similar source area with felsic‐intermediate rocks as dominant contributors. Multiple geochemical parameters and index displayed good correlation, via vertical variations sequence, Jurassic chemical weathering history of northern Qaidam Basin was established, and four stages were recognized from the profile. Phases I and III experienced intense chemical weathering, while Phases II and IV are characterized by mild to moderate chemical weathering. Based on this, long‐term Jurassic climatic evolution of the Qaidam Basin was reconstructed. Early‐middle period of Early Jurassic and middle period of Middle Jurassic developed warm and humid climate. On the contrary, late Early Jurassic‐early Middle Jurassic and late Middle Jurassic‐Late Jurassic was deposited under relatively semiarid to arid climatic conditions.

Topographic growth of the northeastern Tibetan Plateau during the middle‐late Miocene: Insights from integrated provenance analysis in the NE Qaidam Basin

“…It is noted that low Al 2 O 3 /SiO 2 values during 15–13 Ma (20%, n = 22) and high values after ca. 8 Ma (29%, n = 31) match well with whole‐rock geochemical compositions of bedrocks in the East Kunlun Shan (14%–18%, n > 4,400; An, 2015) and widespread Al‐rich metamorphic and sedimentary rocks in the southern Qilian Shan (29%, n = 63; Chen et al., 2009; Hu et al., 2019; Jian et al., 2013; Wang, MacLennan, et al., 2020), respectively. Such observation leads us to favour that sediments are mainly from the East Kunlun Shan during 15–13 Ma and from the southern Qilian Shan after ca.…”

Arid climate disturbance and the development of salinized lacustrine oil shale in the Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China

“…Shale adsorption isotherms show that the J2d 7 has a Langmuir adsorption capacity ranging from 0.55-5.93 m 3 /t, indicating a significant shale gas exploration potential (Wang et al, 2016;Guo et al, 2018). The sequence stratigraphic framework of the Middle Jurassic Dameigou Formation in Yuqia Sag is well-established Shao et al, 2015;Shang et al, 2018;Qian et al, 2018), and organic geochemical analyses have indicated large-scale paleoclimatic change during its deposition (Ritts et al, 1999;Wang et al, 2015;Meng et al, 2018;Hu et al, 2019). However, a detailed understanding of climate variability during deposition, particularly with regard to the changing hydrological conditions, remains unclear.…”

Evolution of depositional environment of the Pliensbachian Stage (Lower Jurassic) coal‐bearing series in the Qaidam Basin, NW China

“…During the Pliensbachian Stage, the tectonic subsidence of the Qaidam Basin is relatively continuous and slow (lower than 20 m/Ma) (Wang et al, 2006). However, the climate in the Qaidam Basin is characterized by multiple significant perturbations (Hu et al, 2020;Zhou et al, 2022) In Episode II, the relatively warm and semi-humid climate is continuous, and the palaeogeomorphology is relatively flat and wide because of the filling effect in Episode I. The sediments also come from the Oulongbruk Block basement lithologies to the north (Yu et al, 2017;Figure 12b).…”

“…During the Pliensbachian Stage, the tectonic subsidence of the Qaidam Basin is relatively continuous and slow (lower than 20 m/Ma) (Wang et al, 2006). However, the climate in the Qaidam Basin is characterized by multiple significant perturbations (Hu et al, 2020; Zhou et al, 2022). Based on high‐resolution mineralogical and geochemical analyses, Zhou et al (2022) identified three warm and humid climate intervals during the Pliensbachian Stage in the study area, which are generally correlated to the increasing atmospheric CO 2 concentrations (Li et al, 2020; Figure 12).…”