Geology and foraminiferal studies of parepare volcanic formation at Parepare City and Suppa, Pinrang, South Sulawesi, Indonesia

The Parepare Volcanic Formation at Parepare City and Suppa, Pinrang, South Sulawesi, Indonesia is lithologically consists of tuffs, porphyry trachytic, volcanic breccia and alluvium. The aim of this research are to produce a geological map of the research area with the scale of 1:25000, to determine the species of foraminifera in tuff lithology and to date/determine the “Epoch” and “Age” of the Parepare Volcanic Formation.The ruff is light to dark brown in colour and range from ash to lapilli tuffi The brecciated-volcanic comprises of trachyte and andesite as fragment and supported by tuff as matrix. Meanwhile, the trachyte is petrographically consist of plagioclase (11%), biotite (15%), pyroxene (2%) and orthoclase (26%). In the present study, seven samples of pyroclastic tuff were collected from one outcrop at Tanahmili. The tuff sample are crush into powder, wash and soak in detergent ovemight by using the simple soaking method. Then the sample are dried, sieve using 0.15 mm mesh. Than the foraminifera were picked and identified using stereomicroscope. The sample collected at the tuff at Tanahmili contain abundance of well-preserved foraminifera. A total of 48 species of foraminifera which belong to 39 genus were successfully identified. According to the chronostratigraphy data of foraminifera species, the age of tuff which is the oldest lithology in the Parepare Volcanic Formation start to deposited, marked by the first appearance of Anastomosa nutalli Hedberg, Bulimina marginata d'Orbigny, Planulina foveolata Brady, Protoglobobulimina pupoides d'Orbigny and Pyrgo subsphaerica d'Orbigny. While the last appearance of Mucronina vaughani Cushman marked the end of it. Based on the parameter of foraminifera age we can conclude that the age of the tuff of Parepare Volcanic Formation is Tortonian of Late Miocene to Zanclean of Early Pliocene. The depositional environment for the tuff based on the foraminifera species is upper bathyal environment at the depth of 200 m to 1000m.