Early Jurassic climate and atmospheric CO<sub>2</sub> concentration in the Sichuan paleobasin, southwestern China

Abstract

Abstract. Climatic oscillations have been developed through the (Early) Jurassic from marine sedimentary archives but remain unclear from terrestrial records. This work presents investigation of climate-sensitive sediments and carbon and oxygen isotope analyses of lacustrine and pedogenic carbonates for the Early Jurassic Ziliujing Formation taken from the Basin in southwestern China. Sedimentary and stable isotope proxies manifest that an overall secular (semi)arid climate dominated the Sichuan Basin during the Early Jurassic, except for the Hettangian. This climate pattern is similar to the arid climate in the Colorado Plateau region in western North America but is distinct from the relatively warm and humid climate in northern China and at high latitudes in the Southern Hemisphere. The estimated atmospheric CO2 concentration (pCO2) from carbon isotopes of pedogenic carbonates shows a range of 980–2610 ppmv (∼3.5–10 times the pre-industrial value) with a mean of 1660 ppmv. Three phases of pCO2 (the Sinemurian 1500–2000 ppmv, the Pliensbachian 1000–1500 ppmv, and the early Toarcian 1094–2610 ppmv) and two events of pCO2 rapidly falling by ∼1000–1300 ppmv are observed, illustrating the pCO2 perturbation in the Early Jurassic. The perturbation of pCO2 is compatible with seawater temperature and carbon cycle from the coeval marine sediments, suggesting a positive feedback of climate to pCO2 through the Early Jurassic.

Clumped isotope evidence for Early Jurassic extreme polar warmth and high climate sensitivity

“…Our Δ47 SST for the Lower-Jurassic can be compared to published results from Earth System models that simulate past intervals of global warmth to discuss model-data discrepancies. Proxy-data indicate an atmospheric pCO2 of 1000±500 ppmv during the Early Jurassic, with maximum values of 1750±500 ppmv, i.e., 6x pre-295 industrial levels (PIL), during the T-OAE (McElwain et al, 2005;Li et al, 2020). Earth system models run at 6x PIL for Early Jurassic (Dera and Donnadieu, 2012) produce lower SST than those inferred from our Δ47 data, with a maximum model-data discrepancy of >15°C at high latitudes (Fig.…”

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

“…Based on high-resolution mineralogical and geochemical analyses, Zhou et al (2022) identified F I G U R E 8 Sedimentary characteristics of the upper sequence in facies association B. (a) Field photograph of outcrop showing the upper sequence in facies association B with highlighted box sections enlarged in (c-e); (b) sketch map of the upper sequence in facies association B, (c) Enlargement from (a) showing black coal seam in the upper sequence of facies association B, (d) Enlargement from (a) showing blocky rooted mudstone in the upper sequence of facies association B and (e) Enlargement from (a) showing plant fossils in the upper sequence of facies association B. three warm and humid climate intervals during the PliensbachianStage in the study area, which are generally correlated to the increasing atmospheric CO 2 concentrations(Li et al, 2020; Figure12). Therefore, we mainly evaluate the influences of climate change on depositional evolution here and suggest the depositional model during the Pliensbachian Stage in the northern Qaidam Basin (Figure12).In Episode I, the basin is in the initial stage of receiving sedimentation.…”

“…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). Therefore, we mainly evaluate the influences of climate change on depositional evolution here and suggest the depositional model during the Pliensbachian Stage in the northern Qaidam Basin (Figure 12).…”

Clumped isotope evidence for Early Jurassic extreme polar warmth and high climate sensitivity

“…Proxy data indicate an atmospheric pCO 2 of 1000 ± 500 ppmv during the Early Jurassic, with maximum values of 1750 ± 500 ppmv, i.e. 6× pre-industrial levels (PILs), during the T-OAE (McElwain et al, 2005;Li et al, 2020). Earth system models run at 6× PIL for the Early Jurassic (Dera and Donnadieu, 2012) or Cretaceous-Eocene paleogeography almost invariably produce lower SSTs than those inferred from our 47 data, with a maximum modeldata discrepancy of > 15 • C at high latitudes (Fig.…”