Aptian–Albian clumped isotopes from northwest China: cool temperatures, variable atmospheric <i>p</i>CO<sub>2</sub> and regional shifts in the hydrologic cycle

Abstract. The Early Cretaceous is characterized by warm background temperatures (i.e., greenhouse climate) and carbon cycle perturbations that are often marked ocean anoxic events (OAEs) associated shifts in the hydrologic cycle. Higher-resolution records of terrestrial marine δ13C δ18O (both carbonates organics) suggest climate during Aptian–Albian, including a period with OAE 1a early Aptian subsequent “cold snap” near Aptian–Albian boundary prior to Kilian 1b. Understanding continental system an important factor determining triggers feedbacks these events. Here, we present new paleosol carbonate stable isotopic (δ13C, Δ47) CALMAG weathering parameter results from Xiagou Zhonggou formations (part Xinminpu Group Yujingzi Basin NW China) spanning Aptian–Albian. Published mean annual air temperature (MAAT) Barremian–Albian Asia relatively cool respect Cretaceous. However, largely based on coupled measurements dinosaur apatite phosphate (δ18Op) (δ18Ocarb) therefore rely estimates meteoric water (δ18Omw) δ18Op. Significant likely influenced δ18Omw region, complicating MAAT estimates. Thus, independent (e.g., clumped isotopes or desirable required confirm estimated δ18Op δ18Oc reliably determine regional δ18Omw. Primary material was identified using traditional petrography, cathodoluminescence inspection, subsampling. Our preliminary Δ47-based reconstructions (record 14.9 ∘C), which interpret as being representative MAAT, match similar paleolatitudes Asian (average ∼ 15 ∘C) across This, supported our atmospheric paleo-pCO2 concentration 396 ppmv, indicates cooler midlatitude climate. Additionally, Δ47 ΔMAP, precipitation, Δδ18Omw) may track drying interval).