Core from the Lower Sihapas Formation were interpreted to represent six shallow marine and shoreline lithofacies. The stratigraphic succession lies within a transgressive and highstand phase comprises aggradational parasequences in the lower part and cycles of coarsening upward or progradational parasequence in the upper part. Each parasequence set contains several parasequences and may he equivalent to one phase of a relative sea level rise and .fall cycle in a shallow marine setting. The upper Oligocene aggradational parasequence of upper shoreface and shoreline facies. pass upward into a fining upward succession of lower shoreface facies. in response to transgression. This unit is overlain by shelf bioturbated mudstone, in response to a relative sea level rise. In the Lower Miocene, this Unit was then followed by upper shoreface and washover facies, corresponding to a regression. This mil is capped by tidal mud flats and tidal sand flat with siderite nodules and thin coal layer The Upper part of the Lower Sihapas succession is lower shoreface facies which pass upward into shelf mudstone of the tipper Sihapas Formation.
Author : Jarot Setyowiyoto