Palaeoecological analysis of Sentolo Formation based on foraminifera fossil assemblage from stratigraphic cross-sectional measurements in Pengasih, Kulon Progo, Yogyakarta

Departement of Geological Engineering Universitas Diponegoro, Semarang, Indonesia

Abstract

Sentolo formation that is included in the Kulon Progo stratigraphic series has a wide distribution. Although there have been a number of studies on it, more detailed research is needed, as there are still many unexplored outcrop locations. Moreover, there are still a lot of questions about the stratigraphic relationship between Sentolo Formation and Oligocene-Miocene volcanic series of Kulon Progo. Based on this background, this study is focused on the existence of foraminifera fossil in Sentolo Formation as an indicator of palaeoecological conditions at the time Sentolo Formation was deposited. This research is very important to get a detail understanding about the indicators that are influential at the time of deposition process of Sentolo Formation in research area. Based on palaeoecological analysis, the palaeoecology at the time Sentolo Formation deposited was normal marine continental slope waters. Meanwhile, the community structure of foraminifera indicates a stable water conditions in a marine environment that was not disrupted by volcanism, so it becomes a good factor for the growth of foraminifera. Whereas the presence of volcaniclastic material mixed with carbonate which is occurred in the lower part of Sentolo Formation were interpreted as reworked of older volcanic rock.