Preangerian (Miocene) Mollusca from the Lower Sangkulirang Marl Formation, Kari Orang, Kalimantan (East Borneo)

In the early part of the century L.M.R. Rutten collected a number of molluscs at his locality number 141, in Lower Sangkulirang Marls, long considered as Early Miocene (Tf2), near Sungai Kari Orang and not far from Witkamp's locality Kari Orang. But for their geologic age, these faunas have very little in common. In the present paper some 20 molluscan species (among them very few bivalves) from loc. 141 are discussed, including 4 new ones (Polinices? (Conuber?) orangensis, Nihonia witkampi, Conus kutaiensis, and Laevicardium (Discors) rutteni), hence no more than 16 are used for age determination. Of these, 14 occur in Preangerian deposits. Equally close relationships appear to consist with the fauna of the Lower Gelingseh Beds and the classical Javanese Preangerian, a distribution also shown by Witkamp's Kari Orang fauna while curiously enough the ties between the latter and loc. 141 are almost non-existent. The overall evidence indicates that part of the Lower Sangkulirang Marl Formation, covering loc. 141 and overlying deposits, should be referred to the Preangerian, Tf3.