10월 28일(목)
․고생물학 | 고기후학
2010 추계지질과학연합학술발표회 초록집 147
Cretaceous atmospheric pCO
2
variations on the basis of pedogenic carbonatesSung Kyung Hong*․Yong Il Lee
School of Earth and Environmental Sciences, Seoul National University, [email protected]
It is important to study the role of atmospheric carbon dioxide concentrations (pCO2) in regulating the temperature during the Cretaceous to understand the evolution of the Cretaceous climate. However, the Cretaceous pCO2 variations remains uncertain. Although pedogenic carbonates have been known as good proxies for reconstruction of the Cretaceous pCO2, detailed long-term Cretaceous pCO2 records from pedogenic carbonates are lacking for the Albian-Early Campanian period. The Gyeongsang Basin, the largest Cretaceous non-marine basin located in Southeast Korea, contains several pedogenic carbonate-bearing strata, ranging in age from the Aptian to Early Campanian, thus filling the age gap in the pedogenic carbonates record. In this study, we present the carbon isotope data of pedogenic carbonates formed during the Aptian to Early Campanian in the Gyeongsang Basin and the corresponding atmospheric pCO2, and then a high resolution Cretaceous pCO2 trend reconstructed by combining the results of this study with recalculated pCO2 levels from the literature.
The carbon isotopic values of the pedogenic carbonates and plant materials in the Gyeongsang Basin range from -8.2‰ to -3.7‰ and from -23.9‰ to -23.3‰, respectively.
The pCO2 estimates derived from pedogenic carbonates of the Gyeongsang Basin show a wide variation, but an increasing trend from 480 ppm V to 1500 ppm V in the studied Aptian to Early Campanian. The compiled pCO2 levels suggest that mid-Cretaceous pCO2 (1000-1600 ppm V) was higher than those of the Early and the Late Cretaceous (<1000 ppm V). This pCO2 trend is in agreement with the broad trend of paleotemperature. Also, our result that pCO2 level rose from 400 ppm V in the Aptian to a peak of 1600 ppm V in the mid-Cenomanian and then declined to 700 ppm V in the mid-Campanian provides new geological evidence in support of the hypothesis that the mid-Cretaceous thermal maximum was caused by high levels of pCO2. The pCO2 levels during the Early Cretaceous are marked by two lows(<500 ppm V). The two pCO2 low intervals seem to associated with evidence reported for the presence of continental ice sheets at high latitudes. Therefore, we conclude that the Cretaceous climatic change was associated with pCO2 variation.
구두 13-2
