Comparative Study of Basins within Palaeogene Seaway in East China and Cretaceous Seaway in North America and Its Reservoir Significance

The well known Cretaceous seaway in North America was recognized in the middle of the last century and the Palaeogene seaway in East China was proposed by the author recently. The two seaways located on the opposite sides of North Pacific Ocean may be not a coincidence, and a comparative study was made in this paper. The results show that the two seaways inundated basins share several similarities particularly in basin origin, filling processes and reservoir facies. It is suggested that reservoir facies of estuarine sandstone and shelf bar sandstone related to sea level fluctuation, which are well developed in the Cretaceous seaway covered basins in North America might have been also developed here in Palaeogene seaway inundated basins in East China. Therefore it is worth paying more attention to finding these new reservoir facies on this side of the Pacific ocean. Evidences of sedimentology and ichnology indicate that good prospects are likely.

Late Palaeogene palynoflora from Point Hennequin of the Admiralty Bay,King George Island,Antarctica with reference to its stratigraphical significance

The present paper is to discuss the geological age and sedimentary environment based mainly on the characteristics of the palynological assemblage in the intercalated tuffaceous sand mudstones of the Upper Point Hennequin Group in the Admirelty Bay, King George Island, Antarctica. More than 40 species, mainly the Late Paleogene plant community in Gondwana and belonging to Weddellian biogeographic Province, were encountered within the volcano sedimentary rocks of the Upper Point Hennequin Group. The index member is the genus Nothofagidites . The occurrence of N. cf. saraensis and N. cf. flemingii and the absence of Proteacidites spp. indicates that the sporopollen bearing rocks is of Oligocene age, which were deposited in a limnetic zone near medium lower mountains environment with warm and humid climate.

Palaeogene Biostratigraphic Characteristics of Red Basins In Western Henan and Its Adjacent Areas, With an Outline of Palaeogene Palaeobiogeographic Provinces of China

This article is a preliminary summary of Paleogene biostratigraphy of the Liguanqiao, Tantou andYuanqu basins, with a new proposal for Paleogene paleobiogeographic provinces of China. On the basis of asynthetic analysis of the geological data, characters of the mammalian assemblages and their comparisons withother corresponding faunas, a new scheme on Paleogene biostratigraphic subdivision of the basins has been putforward here. Based on differences of biostratigraphic sequences, characteristics of mammalian assemblagesand directions of faults controlling Paleogene basins in China, six Paleogene paleobiogeographic provinces ofChina have been proposed in this paper, that is: Tianshan-Yinshan-Tumen Province; Tarim-North China Prov-ince; Kunlun-Qinling Province, Yangtze Province, Nanling and Southeastern Coastal Province, Qinghai andTibet Province.

Formation mechanisms and distribution of high quality reservoirs in deep strata in Palaeogene in northern steep slope zone of Bonan sag, Jiyang depression, China

Petrographic analysis combined with various techniques, such as thin section identification, petro-physical property testing, mercury penetration, oil testing results, was used to assess basic reservoir characteristics of deep strata in Palaeogene in the northern steep slope zone of the Bonan sag, China. The formation mechanisms of high quality reservoirs in deep strata were discussed according to evolution characteristics of paleopressures and paleofluids in geological period. The deep reservoirs have poor physical properties and mainly develop extra-low porosity, extra-low and ultra-low permeability reservoirs. Reservoir spaces mainly consist of secondary pores and overpressure fractures. Early overpressure, early hydrocarbon filling and dissolution by early organic acids are the major formation mechanisms of high quality reservoirs. The conglomerate in inner fan which had a poor primary physical property mainly experienced strong compaction and calcareous matrix recrystallization. The physical properties of the inner fan were poor with weak dissolution because of poor mobility of fluid. The reservoirs mainly are type IV reservoirs and the distribution extends with the burial depth. The braided channel reservoirs in the middle fan had relative good primary physical properties and strong ability to resist compaction which favored the preservation of primary pores. Large amounts of the secondary porosities were created due to dissolution by early organic acids. A series of micro-fractures generated by early overpressures would be important migration pathways for hydrocarbon and organic acids. Furthermore, early overpressures had retarded maturation of organic matters and organic acids which had flowed into reservoirs already and could keep in acid environment for a long time. This process would contribute significantly to reinforcing the dissolution and enhancing the reservoir quality. The braided channel reservoirs were charged with high oil saturation preferentially by early hydrocarbon filling which could inhibit later cementation. Therefore, the braided channel reservoirs develop a great quantity of reservoir spaces with type I, type II and type III reservoirs in the majority in the deep strata. With the burial depth, distributions of type I and type II reservoirs are narrowed and distribution of type III reservoirs decreases first and then extends. The reservoirs both in outer fan and in interdistributary of the middle fan have extremely poor physical properties because of extensive carbonate cementation. The type of the reservoirs mainly is type IV.

Palaeogene Angiosperm flora and environmental implications of Intertrappean Series of Central India

The Palaeogene represents the age of spread and diversification of angiosperms in the Indian sub-continent. The palaeogene plant megafossils of this region can broadly are considered under(i) Deccan Intertrappean flora of CentralIndia,(ii) Eocene flora of Kutch and(iii) Eocene plants fossils from Meghalaya. Among the fossil flora recovered from the Deccan Intertrappean sites of central India consists of well preserved fossil representing all the major groups of the Plant Kingdom. Among the reported angiosperms Aerorhizos, Aeschynomene, Cyperaceoxylon, Bridelioxylon(affinities with marshy Bridelia hamiltoniana), Nymphaeocaulon are the indicators of a marshy environment. Nipadites, Nypa, Cocos, Palmoxylon(Cocos) sundaram, Sonneratioxylon, Sahnianthus, Enigmocarpon, Viracarpon(affinities with Pandanaceae) are the indicators of coastal or estuarine, saline environment. Anogeissusoxylon, Boswellia, Phyllites, Sahnipushpum(affinities with Araceae), Ebenoxylon(affinities with Diospyros melanoxylon), Euphorbioxylon(affinities with Euphorbiaceae), Grewioxylon(affinities with Grewia tiliaefolia), Rhamnoxylon, Sapindoxylon, Syzygioxylon are capable of surviving in a climate not unlike the one prevailing presently in this region. Ailanthoxylon, Barringtonioxylon, Elaeocarpoxylon, Grewioxylon, Indocarpa(affinities with Guttiferae), Lagerstroemia, Musa and Musocaulon, Sparganium, Viracarpon are the indicators of a more humid climate in the past. The 38 species of Palmoxylon and 19 of other palm parts(Nypa excluded) variously described as Carpolithus, Deccanthus, Palmocarpon, Palmophyllum, Palmostrobus, Rhizopalmoxylon and Tricoccites are indicative of coastal habitat. Thus the reported flora consists of taxa belonging to marine, esturine, freshwater and terrestrial habitat with both evergreens to deciduous forms. It is suggestive of an equable warm and moist tropical climate over the whole of peninsular India during the Palaeogene.