Multiple Proxy Estimates of pCO2 in the Hauterivian–Barremian of the Laiyang Basin, Eastern China

Abstract. In recent decades, several proxies have been developed to reconstruct atmospheric paleo-CO2 concentrations (pCO2). The confidence in paleo-CO2 estimates can be increased by comparing results from multiple proxies with multiple species at a single site. Here we present a new pCO2 record for the Hauterivian–Barremian using three methods based on two fossil coniferous species (Cupressinocladus sp. and Brachyphyllum obtusum) collected from Laiyang Basin, eastern China. The pCO2 values were approximately 579–663 ppmv (recent standardization) and 966–1106 ppmv (carboniferous standardization) based on the stomatal ratio (SR)-based method, and about 472–525 ppmv based on the mechanistic model. Both of these two methods were highly coincident with other SR-based and geochemical reconstructions for the early stage of the Early Cretaceous. The pCO2 value estimated using the carbon isotopes model was approximately 472–525 ppmv, which is generally lower than the pCO2 valueestimated using the other methods. The mechanistic model may be widely applied to more fossil taxa than the SR-based method and retains sensitivity at high pCO2. Furthermore, by comparing with other pCO2 records and Weissert event in the Early Cretaceous, the pCO2 values obtained from this study indicate a relatively low atmospheric CO2 concentration during the Hauterivian–Barremian, and reflect the cooling event in the last stage of the Weissert event.