Depositional system of Halang Formation from Ci Mande and Panaruban River outcrop: an interpretive based on lithofacies and trace fossil

Abstract

This paper focuses on confusing various theories of Middle to Late Miocene sedimentary rocks, especially the Halang Formation in the CiMande and Panaruban River Banyumas Central Java. Previous studies revealed miscellaneous conclusions regarding the depositional system of this formation. This research was conducted with field observations, consisting of 2 measured stratigraphy section. Lithofacies and trace fossils are identified by making detailed vertical records of outcrops. The lithofacies association are: B1 is Massive Sandstone, B2a is Parallel Laminated Sandstone, B2b is cross-laminated sandstone, C2 is interbedded sandstone and shale, D1 is Siltstone, E1 is Mudstone, and F2 is Coherent deposits. Four variations of trace fossils include Thallasinoides, Skolithos, Chondrites and Rhizocorallium. It is classified into Skolithos Ichnofacies and Cruziana Ichnofacies in the lower shoreface. Skolithos and Cruziana ichnofacies association in the submarine fan due to local sediments preserved trace fossils are not ultimately consolidating. Based on the facies association, it has characteristics resulting from the turbidite mechanism, which was deposited in the deep marine fan environment precisely in parts of suprafan lobes on midfan. Conversely, the presence and diversity of trace fossils indicate that these sediments were deposited in shallow marine. The conclusion is that the sediment in which the trace fossils are preserved has been partially lithified, and the deposition reworked by gravity in the suprafan lobes on the midfan.