The Architectural Element Distribution of Cinambo Formation in Jatigede Area, Sumedang District, West Java - Indonesia

Abstract

This research is conducted in Jatigede subdistrict, Sumedang district, West Java Province, Indonesia, with a geographic position 175500 - 185000E and 9237800 -9242200 S. There are many different types of rocks scattered forming the Cinambo Formation including sandstones, mudstones, alternation claystones, conglomeratic sandstones, and conglomerate stones. Stratigraphic cross-section measurements on the Cimanuk River and Cinambo River traverses is carried out to figure out the distribution of the architectural elements of the Cinambo Formation. Nine lithofacies are obtained from both traverses: massive conglomerate (A1-1), graded bedding conglomerate and graded bedding conglomeratic sandstone (A2-3), conglomeratic sandstone (A2-1), massive sandstone (B1-1), graded bedding sandstone (B2-4), bedded sandstone (B2-1), alternation sandstone – mudstone (sandstone domination) (C2-2), alternation dense and thin alternation sandstone – mudstone, and mudstone intercalation sandy siltstone. The architectural elements that appear on Cimanuk River traverse are sandy lobe, proximal channel, distributary channel and proximal levee, while the elements that appear on the Cinambo River traverse are sandy lobe, proximal levee and distal levee.  A vertical change of the architectural element can be observed on both traverses, which are likely to be caused by the fluctuation of sea level. Base on the architectural element data, it can be concluded that the Cinambo Formation was deposited in the upper fan-basin plain of a deep-marine fan system.