Litofasies dan Diagenesis Batugamping Formasi Rajamandala di Lintasan Cikamuning
Abstract
Abstract. Limestone of Rajamandala Formation is one of formation that located in North West Java basin with Late Oligocene age based on Martodjojo, 1984. Rajamandala Formation is well exposed in Padalarang area extends to Sukabumi area of West Java. Due to its vast expanse and sufficient variety of rocks in the carbonate platform system, it can be a good model for studying Tertiary reef systems in Indonesia. The method used in this research is the outcrop collection data in the field and petrographic analysis which aims to find out the facies, diagenesis, and age of the Rajamandala Formation especially on the Cikamuning track. The results of the study there are 10 litofasies foraminiferal grainstone, skeletal- coralclast grainstone, skeletal-intraclast rudstone (breccia), platy coral boundstone, foraminiferal packstone, skeletal - coralclast grainstone, large benthic foram grainstone, coral boundstone, compositional grainstone, and compositional breccia grainstone. These facies are covering at least 4 diagenesis environment : marine phreatic, meteoric phreatic, burial diagenesis and meteoric vadose, deposited in Late Oligocene based on paleontology analysis where depositional environment is shallow marine.
Key words: Cikamuning, Diagenesis, Facies, Rajamandala Formation
Abstrak. Batugamping Formasi Rajamandala merupakan salah satu formasi yang berada di cekungan Jawa Barat Utara yang mempunyai umur Oligosen Akhir berdasarkan Martodjojo, 1984. Formasi Rajamandala ini tersingkap dengan baik di daerah Padalarang dan melampar sampai dengan daerah Sukabumi Jawa Barat. Dikarenakan pelamparannya yang sangat luas dan variasi batuan yang cukup lengkap dalam sistem platform karbonat sehingga dapat dijadikan model yang baik untuk mempelajari sistem terumbu Tersier di Indonesia. Metode yang digunakan dalam penelitian ini adalah pengambilan data singkapan di lapangan serta analisis petrografi yang bertujuan untuk mengetahui fasies, diagenesis, serta umur dari Formasi Rajamandala khusunya pada lintasan Cikamuning. Hasil dari penelitian terdapat 10 litofasies: foraminiferal grainstone, skeletal- coralclast grainstone, skeletal-intraclast rudstone (breccia), platy coral boundstone, foraminiferal packstone, skeletal - coralclast grainstone, large benthic foram grainstone, coral boundstone, compositional grainstone, dan compositional breccia grainstone. Batuan karbonat pada lintasan penelitian telah mengalami setidaknya 4 lingkungan diagenesis, yaitu marine phreatic, meteoric phreatic, burial diagenesis, dan meteoric vadose. Umur batuan pada lokasi penelitian adalah Oligosen Akhir berdasarkan analisis foraminifera besar, dengan lingkungan pengendapan adalah laut dangkal.
Kata Kunci: Cikamuning, Diagenesis, Fasies, Formasi Rajamandala
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https://www.google.com/maps/. Diakses 9 Juli 2018
DOI: https://doi.org/10.29313/ethos.v8i1.5077
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