Oxygen And Carbon Isotopic Compositions Of Fossil Brachiopods From Devonian, Longmenshan Area, Sichuan Provoince, P.R. Chian

The carbon and oxygen isotope composition and its evolution of Marine carbonate rock is commonly means to the study of the ancient climate and ancient marine environment. The stable isotope composition of Ancient marine carbonate rock approximate reflect the stable isotope composition. of the ancient oceans. Therefore, the study of marine carbonate rock stable isotope composition is of great significance to understanding the changes of paleocean level, tectonic activity, global climate changes, biological extinction, ancient seawater temperature and salinity. Last 40 years studies shows: brachiopods fossils is the ideal target to reconstruct the stable isotope composition of the ancient oceans for they are widely distributed, low magnesium calcite shell components, and thus have a stronger resistance to the transformation of the role of geneticive capacity geological history.This paper analysed the carbon and oxygen isotope composition of brachiopods fossils from the Devonian Period in Sichuan Province. Through analysis the influence factors that impact its carbon and oxygen isotope composition of brachiopods fossils, the Devonian Period tectonic activity, geographical location and its sea-level change, we reach the following preliminary understanding:1: Passes means of petrographic, trace element, cathodoluminescence, oxygen and carbon isotope analysis: the most of brachiopods from Devonian in Longmen mountain, Sichuan province presered the original oxygen and carbon isotope feature of seawater.2: the carbon, oxygen isotope composition of brachiopods fossils shows: the trends of its evolution have good relationship with the sea-level that reflected by lithofacies paleography. The Sichuan Longmen Mountain Devonian period. The heavy values of oxygen and the light values of carbon reflect the low sea-level. The variations in the oxygen and carbon isotopic signals reflect the transgression happened in the lower and middle Givetian stage and the lower Frasnian stage and the regression happened in the upper Givetian stage and the upper Frasnian stage.3: By discuss the carbon and oxygen isotope composition of brachiopods fossils and its evolution...