K. MASATANI (1967) presented the oil geology of East Kalimantan on this journal. This short note is supplement to his paper. From the oil geologic point of view, the geologic development of the Meratus Range and the eastern rim of the Barito Basin is discussed herein. Newly revised stratigraphy of the pre-Tertiary rocks encountered in the region drained by the Riam Kanan and Riam Kiwa Rivers is introduced and also geologic age of Koolhoven's Manunggul Formation is emended. The discovery of Esteriids from the base of the Rantaulajung Formation occupied at the top of the Manunggul Group which begins with the basal conglomerate and is overlain by the Turonian fossil-bearing formation and others strongly suggest that the necessity of reconsideration of Senonian age of the fauna described by K. MARTIN. The Cenomanian species of Orbitolina, namely O. concava reported by L.H. Krol is considered to be other species, such as Orbitolina lenticularis. Judging from the foraminiferal fauna of the Hantakan Limestone, geologic age of the Orbitolina-bearing formation exposed as the longitudinal strip along the west side of the Meratus Range is considered to be Aptian or so. The Tertiary stratigraphy of the lower reaches of the Riam Kiwa River and the Tandjung oilfield is described. The boundary between the stages Tc and Tab is settled at the base of the C Sandstone which contains reworked Tab foraminifers in the northern part of the Tandjung anticline. The C Sandstone forming the Tandjung anticline unconformably overlies the Tab Formation which is already suffered slightly from folding occurred prior to the deposition of the C Sandstone. However, the Tc formation in the Pengaron area, more than 100km south of Tand-jung, overlies the Tab formation with an apparent conformity. The thickness of the Tc formation in the Tandjung area is 118m, while it is 20-90m in the Pengaron area. An unconformable relation between the Td and Tc formations is presumed in the Tandjung area, but MOHLER stated that "the B.P.M. field geologist took Tertiary c and d togcther, calling "Tcd"… the Tertiary every ofted begins with a slight unconformity". On the contrary, the Te formation in the Tand-jung area conformably overlies the Td formation. On the other hand, HASHIMOTO and KOIKE did not recognize any of the marine Td formation below the marine Te limestone, the Mataraman Formation, in their reconnaissance route along the Riam Kiwa River. A probable nonmarine formation, the Bumirata, is underlain conformably below the Mataraman. It was recorded in the Kahajan test well drilled at Kahajan, about 120km southwest of Pengaron, that the Tcd limestone directly rests on the Tab formation. Thus, the "Te" reduces its thickness toward south and becomes absent, but it increases its thickness toward north and becomes 1, 800m thick in the Upper Mahakam region.
Sedimentary rocks cover the large part of Hokkaido Island and they reserve various kinds of natural resources, such as coal, petroleum, natural gas and porcelain raw materials. But, until today, we have few systematic data on the chemical composition of muddy rocks which are interbedded in the sediments. This paper deals with the chemical and expansion characteristics of the Neogene siltstones from Chikubetsu area, northwestern Hokkaido, and also the geochemical study of depositional environment of the geologic sequence of the area. To get the basic informations on the geochemical and sedimentological studies, seven siltstone samples were obtained at the surface of the ground and additional one sample of fire clay was obtained from the underground mining site. Major elements and expansion properties of these samples were determined. The data were compared with those of average sedimentary rock and average shale reported by F.W. CLARK in 1920, and the following results were obtained; average value of sedimentary Chikubetsu siltstone rock and shaleSiO2% low high P2O5% high low Fe2O3% high low MnO % high low CaO% high low K2O % high low The geochemical study of the depositional environment for each formation was tried using the value of Fe2O3/FeO ratio, and the followings were obtained. fire clay in Haboro Formation…fresh water Kotanbetsu Formation…brackish water Chikubetsu Formation…brackish water Haboro Formation…brackish water other formations intercalating tuffaceous siltstones…volcanic ash containes a large amount of Fe2O3 and could not determine the depositional The value of expansion ratio of a siltstone sample from Haboro Formation reaches up to 5 to 6, therefore, this newly discovered expansion siltstone may be suitable for the practical usage.
The preliminary study was carried out on the carbon isotopic ratios of about 30 samples of crude oil obtained from some oil fields in Akita and Niigata prefectures, northern Japan. The reservoir strata of these oil fields are mainly composed of sandstone and mudstone except a few cases of volcanic tuff and of dolomite, and these rocks are ranging from Miocene to Pliocene in age. Massspectrometric measurement of carbon isotopic ratios is performed by the method proposed by McKinney and Craig with a little modification. Carbon isotopic ratios show rather uniform distribution through the samples and the δ-value in P.D.B. scale have an average of-23.7‰ with the range from-24.7 to-22.2‰. These features are closely resembled to those of oil from North America that sammarized by Degens. (E.T. Degens, 1969). The importance of carbon isotopic investigations on the separate fractions of distillation of crude oils is pointed out for the discussions on the origin of petroleum.