Micropaleontology analysis of larger foraminifera at the bottom of Wonocolo Formation have never done, because most research pertaining to this formation is more focused on micropaleontology analysis based of planktonic and small benthonic foraminifera as microfossil index of decisive determinant of the age and depositional environment. The terminology of larger benthonic foraminifera is intended for foraminifera that have a relatively large size (> 2mm) and determination can only be distinguished from the inner structure, so that identification can only be done by observing thin sections of loose rock or fossil. Three larger bentonik foraminifera are recorded in the lower part of Wonocolo Formation. These species are Cycloclypeus eidae, Lepidocyclina (T) rutteni and Lepidocyclina B form. The content of these larger benthonic foraminifera indicate that the bottom of Wonocolo Formation have Tf1-2 age which it same as upper part of Middle Miocene to lower part of Late Miocene. For furthermore, it can be correlated with the planktonic foraminifera zonation as N15/N16 zone and deposited in the middle neritic environment.
Larger bentonic foraminifera, Wonocolo Formation, Middle to Late Miocene
Author : Muhammad Tatang Djunaedi, Mohammad Taufiq