CARBONATE DEPOSITIONAL ENVIRONMENT AND PLATFORM MORPHOLOGY OF THE WONOSARI FORMATION IN THE AREA EAST OF PACITAN

Abstract

Field observation and laboratory work have been conducted to determine the carbonate facies distribution and to interpret the environment of deposition and platform morphology of the Tertiary limestones of the Wonosari Formation in the east of Pacitan. All samples were then classified based on Jordan classification (1985), and being interpreted their environment of deposition. The Wonosari Formation in the east of Pacitan comprises of coral boundstone facies, foraminifera packstone-wackestone, larger foram packstone, coral-larger foram rudstone, and algal-foraminiferal packstone facies. These facies represent depositional environments of the reef zone or the outer shelf, basin-outer slope and middle-upper slope environments situated to the north of the reef zone, and a back reef-inner shelf environment to the south and west. Sari: Penelitian lapangan dan analisa di laboratorium telah dilakukan untuk menentukan sebaran fasies karbonat dan interpretasi lingkungan pengendapan serta morfologi platform dari batugamping Tersier Formasi Wonosari di sebelah timur Pacitan. Sampel batuan diklasifikasikan berdasarkan klasifikasi Jordan (1985) yang kemudian diinterpretasikan lingkungan pengedapannya. Formasi Wonosari di timur Pacitan terdiri atas fasies coral boundstone, foraminifera packstone-wackestone, larger foram packstone, coral-larger foram rudstone, dan fasies algal-foraminiferal packstone. Fasies-fasies tersebut mewakili lingkungan-lingkungan pengendapan reef zone atau outer-shelf, lingkungan basin-outer slope dan middle-upper slope yang terletak di utara reef zone, serta lingkungan back reef-inner shelf di sebelah selatan dan barat reef zone.