TRIASSIC CARBONATE ROCKS IN THE PHATTHALUNG AREA, PENINSULAR THAILAND

Carbonate rocks in the Phatthalung area and others in Peninsular Thail and have been known as the Permian Rat Purl Limestone. The study area is characterized by several isolated limestone mountains and is locate d in Phatthalung province. Micropaleontological study of these carbona te rocks indicates that they should be assigned a late Early to Late T riassic age. The Chaiburi Formation is newly proposed and divided into three members: the Phukhaothong Dolomite, Chiak Limestone and Phanomw ang Limestone in ascending order. The Phukhaothong Dolomite consists o f thickly bedded to massive dolomite and yields Neospathodus kummeli S weet, N. waageni Sweet, N. cfr. waageni Sweet and other conodonts that indicate Dienerian to Smithian (Early Triassic). The Chiak Limestone Member consists of bedded and laminated limestone with intercalated th in chert layers and nodules. This limestone commonly yields Early Tria ssic to Middle Triassic conodonts such as Neospathodus timorensis (Nog ami) and Neospathodus kockeli (Tatge), both reliable indicators of lat est Spathian to early Anisian, and rare occurrences of Neogondolella b ulgarica (Budurov and Stefanov), an indicator of the middle Anisian. T he Phanomwang Limestone Member is mostly massive limestone with interc alated reef limestone (coral buildups) and yields abundant fossils tha t indicate Carnian (Late Triassic). Microfacies analysis and stratigra phic sequences of carbonate rocks in this area show the gradual change of depositional environment from low to high energy conditions.