Pre-Tertiary stratigraphy of the Tanimbar islands, Indonesia
Rakhmat Fakhruddin
Centre for Geological Survey, Geological Agency, Ministry of Energy and Mineral Resources, Jl. Diponegoro No. 57 Bandung, Jawa Barat, Indonesia
Abstract
Relatively few Pre-Tertiary outcrop examples have been described in the literature. Pre-Tertiary rocks outcrop at these islands is hardly found due to high levels of weathering and dense vegetation. This area needs a further geological works because this is one of the few area near offshore of Arafura sea where we can get Pre-Tertiary rocks outcrop analog for subsurface interpretation. The main objective of this paper is to recognize the stratigraphic successions of the Pre-Tertiary sedimentary rocks exposed in the study area based on their lithological characteristic and palynological ages. The methods used are geological fieldwork and palynological analysis for samples obtained. Four lithostratigraphic units are recognized from the outcrops: 1) Upper Triassic (Rhaetian to Carnian) limestone, sandstones, and claystone of Wotar Formation with depositional environment ranging from marginal marine to deep water environment, 2) Lower Jurassic (Toarcian to Hettangian) sandstones and claystone of Selu Formation, the unit was deposited at shallow marine with tide influenced environment, 3) Upper Jurassic (Tithonian) to Lower Cretaceous (Barrimian) red and brown claystone and siltstone of Arumit Formation, which was deposited in tidal environment, and 4) Lower Cretaceous (Aptian) to Upper Cretaceous (Maastrichtian) sandstone of Ungar Formation, which was deposited in foreshore, shoreface to marine offshore environment. Middle to Upper Jurassic rock unit was not found at the studied area. This time interval is probably represented by the clay dominated matrix of mud volcano (Bubuan Mud Complex).
Keywords: Pre-Tertiary, Tanimbar, Wotar, Selu, Arumit, Ungar, Bubuan Mud
Topic: Geology