Pustaka Ilmiah Universitas Padjadjaran

Abstrak

Paleoenvironment Kelompok Pematang , Subcekungan South Aman , Cekungan Sumatera Tengah Berdasarkan Data Wireline Log, Core, Dan Seismik.

South Aman Trough is located in the southern part of Central Sumatra Basin. Pematang group of South Aman Trough sedimented over a period of syn-rift tectonic (Heidrick et. Al, 1996). Weak seismic reflection and strong amplitude seismic shows facies indications that associated with lacustrine environments. During paleogene time, large freshwater system developed within structurally controlled rift graben (H.H William and R.T Eubank, 1993). Shale in rich organic material dominates in pematang group that makes it good as source rock. But there are also sandstone and konglomerat facies that exhibit the association with alluvial fan environment. lithofacies analysis shows all cores in research area sedimented in terrestrial environments, such as lacustrine and river. Reddish Paleosoil exhibit the characteristics of the Lower Red Bed Formation and Upper Red Beds Formation which is sedimented in lacustrine to fluvial environments. Parallel lamination brown shale exhibit the characteristics of the Brown Shale Formation which is deposited in a large lacustrine system. Sandstone with coarse grain to conglomerate with coarsening upward pattern show the associations of braided fluvial system. Elektrofacies log analysis indicates a pattern associated with lacustrine to fluvial environments.Sequence stratigraphic interpretation guide us to reconstruction the paleoenvironment. In this research area, we are able to identified 4 sedimentation sequence. All of the sedimentation sequence shows the paleoenvironment. Sedimentation sequence-1 with coarsening upward log pattern shows the shallow lacustrine environment where accommodation is relatively low. Sedimentation sequene-2 shows the accommodation to be relatively higher with deep lacustrine environment. Sedimentation sequence-3 shows a decrease in accommodation which is associated with braided fluvial system environment. Sedimentation sequence-4 show the environment which is associated with fluvial meandering system. Paleoenvorinment reconstruction will be useful for geologists and geophysicist to make the exploration become more economical.