Multiproxy Paleosol Evidence for Jurassic Paleoclimate Fluctuations in the Sichuan Basin, SW China

Abstract

Paleoclimate reconstruction of continental environments has been hampered by the limited evidence. A thick sequence of Jurassic continental deposits in the Sichuan Basin, Southwest China yields abundant paleosols that may offer valuable insights regarding Jurassic climate scenarios. A succession of 169 paleosols belonging to Protosols, Calcisols, and Argillisols from 23 detailed stratigraphic sections was recognized and characterized macro‐ and micromorphologically and assessed for mineral and geochemical compositions. Quantitative paleoclimate reconstructions using bulk geochemical proxies, the depth to and the stable oxygen isotopic composition of paleosol carbonates indicated a predominant alternation of semiarid and arid cool/warm‐temperate climatic conditions punctuated by several episodes of subhumid and humid climates that generally prevailed in the Sichuan Basin during the Jurassic. The estimated paleoatmospheric CO2 concentrations (pCO2) from calcic paleosols yielded a low range of ∼104 ± 58 to ∼610 ± 152 ppmv during the Middle Jurassic. The terrestrial paleotemperature changes in the Sichuan Basin coincided with the pCO2 variations, which probably resulted from global geological events (e.g., volcanic activities, magmatic and oceanic events, and the ephemeral caps development) in the Middle Jurassic. Jurassic climatic fluctuations in the basin were likely attributed to true polar wander due to global plate motion, megamonsoon effect linked to global and regional paleogeography, and regional paleotopography.

Evolution from shallow‐water deltas to fluvial fans in lacustrine basins: A case study from the Middle Jurassic Shaximiao Formation in the central Sichuan Basin, China

“…Apart from the tectonics, climate is also a significant driver of basin‐fill processes (Foreman et al ., 2012; Simpson & Castelltort, 2012; Foreman, 2014; McKie, 2014; Colombera et al ., 2017; Noorbergen et al ., 2018; Nutz et al ., 2020; Lin et al ., 2022). The Shaximiao Formation corresponds to an overall relatively arid environment (Li et al ., 2022a,b). Petrographic and geochemical analyses indicated frequent fluctuations between relatively arid and humid climates in the study area (Figs 11 and 12), which has also been supported by palaeosol geochemical analyses conducted by Li et al .…”

“…Petrographic and geochemical analyses indicated frequent fluctuations between relatively arid and humid climates in the study area (Figs 11 and 12), which has also been supported by palaeosol geochemical analyses conducted by Li et al . (2022a,b). The overall oxidizing environment, as demonstrated by U/Th, Ni/Co and V/Sc values, corresponded to shallow water or exposed conditions in the study area (Fig.…”

Element Geochemical Characteristics and Geological Significance of Mudstones from the Middle Jurassic Shaximiao Formation in Sichuan Basin, Southwest China

“…The element characteristics show that the western edge of the basin was warm and dry in the Middle Jurassic, and turned cool in local periods . The characteristics of clay minerals in the southwestern margin of the basin indicate a semi-arid climate dominated by intermittent cold and drought when Shaximiao Formation was deposited . The analysis of the paleosol and carbonate nodule in the northeast of the basin shows that this period is in the semiarid to semihumid climate and the dry-humid and cool/warm temperate climates alternately .…”

“…14 The characteristics of clay minerals in the southwestern margin of the basin indicate a semi-arid climate dominated by intermittent cold and drought when Shaximiao Formation was deposited. 15 The analysis of the paleosol and carbonate nodule in the northeast of the basin shows that this period is in the semiarid to semihumid climate and the dry-humid and cool/warm temperate climates alternately. 16 These studies reveal the paleoclimate of each region of the basin but lack of comprehensive analysis combined with mudstone type, paleowater body, and oxidation conditions.…”

Oscillations of a fluvial‐lacustrine system and its ecological response prior to the end‐Triassic: Evidence from the eastern Tethys region

“…The Xujiahe Flora has been suggested to be flourishing under tropical‐subtropical hot and humid climatic conditions (Lee, 1964; Ye et al, 1986; Wu, 1983; Sun et al, 1995). In recent years, studies on systematic palaeobotany (Lu et al, 2021; Wang et al, 2015; Xu et al, 2021), palynology (Li et al, 2016, 2018; Liu et al, 2015), as well as sedimentology and geochemistry (Lu et al, 2019; Pole et al, 2018; Shen et al, 2022; Zhu et al, 2017) were conducted for these Upper Triassic sequences of the Sichuan Basin, showing notable temporal variations in climate at that time (Li et al, 2020; Li et al, 2021; Lu et al, 2019; Tian et al, 2016). The environmental evolution during the Late Triassic in the northeastern Sichuan Basin is yet poorly understood, which is critical to provide insight on the level of ecosystem stability, deterioration and/or collapse prior to the Tr–J transition in this region.…”