Paleoclimate of some Permo-Triassic carbonates of Malaysia

Abstract

Four hundred thin-sections of Permian (Chuping and Summalayang Limestones) and Triassic (Kodiang Limestone) carbonates of Malaysia were studied, mainly to interpret probable climatic zones during their formation. Chuping Limestone is rich in skeletal grains and intraclasts formed in shallow, high-energy environments. Original mineralogy of skeletal grains and early diagenetic cements were chiefly calcites with some aragonite. The faunal assemblage is similar to that of subpolar carbonates. The brachiopods are characterized by heavy δ 13C and light δ 18O and these values lie in the same field as an Early Permian fauna from eastern Australia. The δ 18O values of fauna show unrealistic temperatures because the fauna has equilibrated with melt waters. However, calculated original δ 18O values of the fauna from δ 13C indicate temperatures ranging from 2 to 13°C with δ w of +1.2. These features reflect cool-temperate (to ?subpolar) conditions. Summalayang Limestone is rich in fusulinids and was deposited in bar to shelf environments. Fusulinids are often filled with fine, equigranular sparry calcite. Early diagenetic origin of these cements is indicated by erosion of cements during transportation and also by the cross-cutting relationship of veins with cements. These cements were originally Mg calcites. The foramol faunal assemblage, and predominantly Mg calcite mineralogy of both fauna and cements, reflect temperate climate. Kodiang Limestone was deposited in peritidal environments. This limestone formation has all the characteristic features of modern, warm, tropical carbonates such as chlorozoan assemblage, diverse non-skeletal grains, abundant early diagenetic dolomites and predominance of aragonitic fauna, non-skeletal grains and cements. The formation of temperate carbonates during the Permian suggests that Malaysia was probably part of Gondwanaland.