The Indian subcontinent and Asian continent first contacted in the late Cretaceous (about 65Ma) and strongly collided after 52 Ma that is evidenced by slowed northward motion of the Indian Subcontinent from 18-20cm/yr to 4.5cm/yr. Although the first record of uplift in Himalayan regions has been recorded during the Eocene, major uplifts of the Himalayan Range and Tibetan Plateau and the subsequent sediment supply started from the Oligocene through Miocene. Particularly, the rapid uplift stages of Himalayan-Tibetan regions have been recognized, at least, around 8Ma and the last 1Ma based on sedimentological and paleonbotanical studies of marine and terrestrial sequences. The micropaleontological studies in marine sequences revealed that the increased elevations in the Himalayan-Tibetan regions forced a strong monsoonal circulation about 8 Ma, which produced intense upwelling around the Arabian Sea and more seasonal climate changes of terrestrial sequences around the southern Asia. The hypothesis that uplift of plateaus and mountains caused large-scale climate changes during the Cenozoic is still unknown. However, an enhanced chemical weathering due to tectonic uplift in the Himalayan-Tibetan regions may be explained as the active driving force of the Cenozoic global cooling at the beginning of 50 Ma.
Cenozoic paleoclimatic and paleoenvironmental changes in the northwestern Pacific region, including Kamchatska, Sakhalin and northern Japan, can be summarized as followings: 1) Cenozoic paleoclimatic changes of Kamchatska are similar to those of the Hokkaido and Sakhalin. 2) Parallel communities of shallow-marine mollusks can be recognized throughout the Pelogene and Nogene in Sakhalin, Kamchatska and northern Japan. 3) The Oyashio-type cold water-mass might be first appeared at around 1 Ma as indicating by such shallow-water mollusca as Chlamys islandicus. These Cenozoic geological history and faunal changes of the northwestern Pacific region should be considered from a viewpoint of the Pacific gateway events such as onset of the Drake Passage at 23.5 Ma, enclosure of the Indonesian seaway at 17 Ma, the intermittent opening of the Bering landbridge after 5 Ma and so on.
The Cretaceous to Paleocene Yezo forearc basin was developed between the western Early Cretaceous volcanic arc and the eastern Early Cretaceous to Early Eocene accretionary complexes in the northeastern margin of Eurasia Plate. Its sediments are distributed across a 150 km-wide and 1400 km-long belt from Northeast Japan to Sakhalin including off the Pacific coast in north-south direction. It is subdivided into three subbasins on the basis of geologic setting: Hokkaido, Kitakami and Joban subbasins. In the first half of this paper, the tectonic setting is reviewed not only for the better understanding of the basin, but also in order to evaluate the distribution of carbonaceous rocks as source rocks and reservoir sandstone. In the latter half, twenty-seven stratigraphic sections including 4 onshore and 8 offshore boreholes and 15 surface sections are correlated to delineate the sedimentary history and basin evolution through the temporal and spatial distributions of facies successions and depositional sequences. Two second-order shallowing-upward cycles for the Cretaceous are recognized in Hokkaido but are obscure in northern Honshu. Shallow-marine to paralic sediments of the first cycle (early Albian to Turonian) are represented by the Mikasa Formation (late Albian to Turonian) as the western marginal facies in Hokkaido. The Campanian to Maastrichtian shallow-marine and non-marine facies of the second cycle (Coniacian to Maastrichtian) are characterized by the Hakobuchi Formation in the Hokkaido subbasin and its correlatives in the Kitakami and Joban subbasins. The two formations include several third- and fourth-order depositional sequences with coarsening-upward facies successions. The uppermost Maastrichtian to Upper Paleocene interval is missing everywhere in the Yezo basin. Furthermore, two third-order depositional sequences of the late Paleocene (uppermost Hakobuchi Formation) and the uppermost Paleocene to lower Eocene (Haboro Formation) have developed with unconformities in a few areas.
A new assemblage of Late Cretaceous fossil plants (the Kamikitaba assemblage) was discovered from the Ashizawa Formation of Futaba Group (Early Coniacian; 89Ma). The flora includes well-preserved mesofossils of angiosperm flowers, fruits, seeds, leaf fragments and woods. Some aspects on the origin of angiosperms and the vegetational consequences of Cretaceous and Paleogene flora are reviewed in the paper.
There exist coal-bearing Paleogene basins along the Straits of Tatar, in the southwest Sakhalin. Those are presumed to be the northward extension of the hydrocarbon-yielding Ishikari Basin. Several basins in the southwest Sakhalin yields matured source rocks, which are evident from the existence of the offshore Izyilmetiev gascondensate field and many oil seepages on land. Five Paleocene coals, one Miocene coal and four Miocene siliceous mudstones were collected for pyrolysis analysis in the southwest Sakhalin on the land area. The results are as follows; Eocene coal (Nizhne Due Fm.) : HI : 263-430 mg/g, TOC : 45.46-73.05%, Tmax : 408-424 degree C. Miocene coal (Verkhne Due Fm.) : HI : 177 mg/g, TOC : 62.48%, Tmax : 408 degree C. Miocene siliceous mudstone (Kurassi Fm.) : HI : 159-275 mg/g, TOC : 1.26-1.79%, Tmax : 396-411 degree C. According to the results, Paleogene coals have most promising potential to expel hydrocarbon and develop seepages to the surface. This paper reports not only the non-marine source rock potential but also the petroleum potential of basins in the southwest Sakhalin on the analogy of the Yufutsu Field in the Ishikari Basin of Japan.
Chinese Cenozoic sedimentary basins are divided into two basin groups by their tectonic feature and the geographical distributions. The divided line lies from Holan Shan (Ningxia Province) to Dashue Shan (Sichuan Province), via Liupan Shan — Longmeng Shan. Western Basins consist of Tarim Basin, Qaidam Basin and Junggar Basin etc. They are compressional basins and relatively vast basins in the area. Eastern basins are extensional (rift) basins, which are subdivided into three basin groups. They are Eastern Sea Coast Basin System, Eastern Basin System and Western Basin System. Eastern Sea Coast Basin System includes East China Sea Basin and Pearl River Mouth Basin etc. Eastern Basin System includes Sungliao Basin and Bohai Gulf Basin etc. Western Basin System includes Ordos Basin and Sichuan Basin etc. It is estimated that around 90% of crude oil originated from non-marine source rocks. Biomarker data from Qaidam Basin, Bohai Gulf Basin and Pearl River Mouth Basin have been interpreted. In Qaidam Basin, biomarkers indicate the existence of the hypersaline environment in the era of Oligocene and Miocene. Main source rock of Es3 (3rd member of Shahejie Formation) is abundant of non-marine algae in Bohai Gulf Basin. Biomarker data from Wenchang Formation and Enping Formation, which are main source rocks in Pearl River Mouth Basin, indicate that source material was deposited in the fresh water environment.
The Tertiary Mahakam Delta Province, East Kalimantan, Indonesia, has produced significant oil and gas in amount to more than 3 billion barrels of oil equivalent from the late 19th Century to the end of the 20th Century. The origin of the oil and gas is widely believed to be non-marine. Pre-PSC activities of oil and gas exploration began in the onshore area of the Samarinda anticlinolium, and resulted in the discoveries of the Sanga-Sanga oil fields. The oil fields produced mostly waxy, heavy to medium oil. The activities produced 33 millions barrels of oil to 1940. PSC activities commenced in late 1960's, and are essential to the oil and gas production in the area including onshore and offshore Mahakam Delta Province. The PSC exploration was initiated with a geological imagination that folding structures similar to those onshore should have been extended off the Mahakam delta, too. The activities in the PSC exploration in early 1970's resulted in the beginning of oil production in 1972 and gas in 1982. Exploration concept established in 1970's also resulted in the discovery of Sisi-Nubi and Peciko gas fields more off the delta. The exploration concept consisted of an idea of non-marine origin of oil and gas, and of corridor function of reverse faults for the oil and gas migration. Exploration opportunity on the shallow-water areas was saturated in the middle of 1990's, which corresponded the peak of oil production in Indonesia. The exploration targets shifted to deepwater areas. The shift needed a new concept to establish a reasonable mechanism of oil and gas charge to the anticlinal traps in the deepwater areas. An idea for this need is significant supply of coal and coaly mud from the delta to the deepwater areas in periods of lowstand.
Japan Vietnam Petroleum Co., Ltd. (JVPC) confirmed oil accumulation in fractured granitic basement and Miocene sandstone at the Rang Dong structure in Block 15-2, offshore S. R. Vietnam. Since 1998, Rang Dong oil field is producing oil from both reservoirs. The Cuu Long Basin has thick and wide syn-rift deposits of the Oligocene lacustrine source rock shale which is confirmed in over 30 wells drilled in Block 15-2. This shale is dark brown, very hard with oil shows, high resistivity and slow sonic velocity. The source rock potential is very high with 1-4 wt% of TOC and 200-700 mg/g of HI. The kerogen type is dominantly type I and is highly oil prone. Although the shale encountered in the Rang Dong field are immature, it is estimated to be mature to overmature at the center of the basin and near mature at the proximity of the Rang Dong field. The characters of the oil produced from the fractured reservoir and the Miocene sandstone reservoir in the Rang Dong oil field are commonly high wax, low sulfur and 35-43 deg. API gravity. In another structure, condensate (52 deg API) was found in the weathered zone of basement. The oil maturation confirmed by biomarkers suggests that the oil produced from basement has higher maturity than Miocene oil. From Sterane triangle plot, these produced oils are confirmed to have been generated by the same source rock which is the Oligocene lacustrine shale. In a few wells, a fracture-filling “Tar-like Material”, a possible obstacle for production, was locally found in the fracture zone of the basement. It is largely insoluble in the organic solvent and more mature than the produced oil. Biomarkers and geochemical data suggest that it is generated by some sort of cracking byproduct.
Tertiary basins in Thailand are pull-apart basins which originated in coincidence with collision of Indian Plate and Eurasian Plate at the end of Cretaceous age. Lacustrine sediments of “Oligocene” age are commonly recognized in the lower part of the basins, which are known to act as source rock for crude oil both in onshore and offshore areas. Based on geochemical investigation of the basins, characteristic two patterns of petroleum system from the lacustrine source rock were recognized as (1) “syn-rift type” and (2) “post-rift type”. In the syn-rift type, source and reservoir rocks are interfingering, or reservoirs are located immediately above the source rocks, which lead to lateral migration or short vertical migration of hydrocarbons. In the post-rift type, source rocks are present at greater depth than reservoirs and, therefore, hydrocarbons should migrate vertically to shallower reservoirs and oil reservoirs and gas reservoirs coexist. Tertiary basins in Thailand originated with common lacustrine source rocks at the bottom. However, differences in the subsequent tectonic movement lead to the variations in depth and maturation level of the source rock and reservoir type. Consequently two different types of petroleum system were formed.
It was formerly thought that Miocene coal is main source rock in the basins in and around Indochina Peninsula in Southeast Asia. However, detailed investigation by the state-of-art geochemical analytical technique such as GC-MS-MS and diamondoids on crude oils and condensates revealed that Oligocene lacustrine source rock exist and the petroleum system originated from this source rock play an important role in these basins. The analytical results indicated that different type of fluids (oil, condensate and gas) generated from 2 source rocks mixed during their migration and trapping. Two-dimensional basin modeling on the Malay basin confirmed the mixing of different type of fluids during their migration and trapping. The understanding of this kind of complex dual petroleum systems will give new insights on petroleum potential of the basins in Southeast Asia.
Planktonic foraminiferal marker beds such as Globorotalia ikebei bed, No.3 and No.2 Globorotalia inflata beds and Neogloboquadrina asanoi bed, have been useful for correlation and age determination of the marine Plio-Pleistocene formations along the coast of the Japan Sea in northeast Japan. All the marker beds are not necessarily found in the oil exploratory wells, however, although the formations are inferred to be deposited under the deep sea environment (the Uvigerina akitaensis Zone of benthic foraminifera). The N. asanoi and No.2 G. inflata beds are more occasionally missing at offshore wells, Akita Prefecture. The distribution maps of each marker bed were made based on biostratigraphic data of 80 wells, and they suggest that regional deep sea erosion and/or non-deposition occurred at topographic highs of anticlinal structures which had been formed in relation to compressional foldings since early Pliocene. The occurrence patterns of the marker beds were divided into five patterns based on their combination of existence and missing. The patterns could be closely related with the timing of structure growths. It is interpreted that major scaled erosions occurred at the Marker A and around the Pliocene-Pleistocene boundary, where they eroded the No.2 G. inflata bed and the N. asanoi bed, respectively. Structural uplift is considered to be the important factor for the deep sea erosion of the marker beds.