AMT and Gravity across PraTertiary Rock Complex of Kebumen, Central Java, Indonesia

摘要

Kebumen area is located in central Java Province, Indonesia, where outcrop of Pretertiary rock of old accretion wedge presence. However, the subsurface of the area, limestone, igneous rock, and Conglomeratic-clay of Karangsambung Formation, is poorly understood in subsurface. The current survey of gravity and AMT data is executing to delineate this boundary. The gravity profile and three point AMT is measure for reconnaissance study. The field observations for rock formations are also scrutinized, but the soil is prohibiting to seen more deep in detail. The general result of interpretation and modeling, show reaching depth of one and half kilo meter, the gravity data cover the mayor rock, but the AMT is more significance in better delineating the boundary. Hence the lithology could be distinguished for melange rock (1000 Ohm.m) and Karangsambung Formation of clay-conglomerate (80 Ohm.m), but also diabase of volcanic-plutonic rock (4000 Ohm.m). The preliminary result shows two mayor results, for limestone and Diabase. Limestone is spread-out on this area, probably the olistolith, and its extensions is more pronounce in the sounding point than the surface observations only. The mysterious of diabase, is more possible as sill product rather than vertical dike.