ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Nine formations from the Mergui Basin, Andaman Sea, are described in detail: the Ranong, Yala, Payang, Tai, Kantang, Surin, Trang, Thalang and Takua Pa Formations. Of these, the Ranong, Yala, Tai, Surin and Thalang are described for the first time, while the Payang, Kantang, Trang and Takua Pa are redefined and formally described. The Mergui Basin is a transtensional back‐arc basin, which formed in the Oligocene due to the onset of steady and increasingly oblique convergence between the Indian and SE Asian Plates and the formation of associated strike‐slip faults. The geological history of the Mergui Basin and surrounding areas is briefly summarised. Major similarities between the Mergui Basin and the petroleum‐rich North Sumatra Basin are noted, and the petroleum potential of the Mergui Basin is briefly ass

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Minor amounts of authigenic pyrite are common throughout the Middle Jurassic Brent Group, often being well developed within the delta‐plain fades of the Ness Formation. Petrographic analyses of pyrite samples from the Lyell and Murchison fields reveal two stages of pyrite authigenesis, both of which occurred during an early stage of burial.The first phase of pyrite authigenesis is represented by the development of nodules and finely‐disseminated cement within shale, mudstone, and siltstone fades, and can include the development of bladed marcasite nodules. These cements are interpreted as having formed within organic‐rich sediment soon after deposition, and pre‐date all other authigenic precipitates (typically calcite, quartz and kaolinite). “Early” pyrite cements display a wide range of δ34S(‐14.9 to +42.5% CDT), and some nodules analysed display isotopically‐heavy cores and considerably lighter margins. These isotopically‐zoned nodules are problematical. They could be interpreted as forming via progressive “closed system” bacteriogenic reduction and isotopic fractionation of sea‐water sulphate, with incorporation of heavy H2S into the earliest‐formed pyrite occurring as a result of its upward diffusion through the sediment column, following isotopic fractionation at depth. However, there are a number of problems with this type of interpretation. These include the fact that diffusion will favour the32S isotope, so that the first‐formed cements should still be isotopically “light” not “heavy”; also, there is a mass‐balance problem, in that no low δ34S sulphides were detected.Coarsely‐crystalline pyrite euhedraform nodular cements mainly within sandstones (δ34S ‐2.6 to +12.8%CDT), and are interpreted as a “later” diagenetic phase. This second phase of sulphide cementation also pre‐dates the main phases of quartz and kaolinite authigenesis within sandstones, but post‐dates an early phase of kaolinite, and may have been partly coeval with some early calcite authigenesis.High organic contents and the early establishment of reducing conditions led to early formation of pyrite within fine‐grained brackish and marine sediments. The lowest measured end‐member δ34S of sandstone‐hosted pyrite cements is less isotopically depleted than that within fine‐grained argillaceous fades, perhaps indicating that sandstone‐hosted pyrite cements began to form subsequent to the onset of burial and bacteriogenic reduction within mudstones. Compaction of marine/brackish‐water shales and mudstones (or sulphate diffusion from these fades) may have supplied an already isotopically‐fractionated source of sulphate to poro

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abundant evidence from the Northern Gulf of Mexico Basin suggests that late Early Cretaceous to Recent sea‐floor spreading is the principal factor in the formation of the structural components of this basin. This would classify the Gulf of Mexico Basin as an active tectonic basin as opposed to the more accepted passive basin status. The following two‐part paper presents a model for this lithospheric plate adjustment together with the geological evidence to support this movement. Part 1 discusses the rift model and supporting evidence. Some of this evidence is: a proposed triple‐junction rift zone radiating from a large dome centered in the DeSoto Canyon area; the division of the Gulf of Mexico Basin Jurassic salt province into three salt basins (the Interior, Exterior, and Challenger Basins); the linearity and structurally‐positive attitude of the Cretaceous Shelf Edge; an excessive Exterior Basin salt mass that thickens towards the Sigsbee escarpment; large areas of non‐diapiric salt found within the Exterior Basin; an extensional fault zone found underlying the Abyssal Plain; and the absence of a Late Mesozoic section from the Exterior Basin, a section that would be needed to cover the salt until it was overlain by younger Tertiary sediments.Part 2 discusses further evidence for an active Gulf of Mexico Basin, and includes the following observations. The recorded positive gravity response in the Exterior Basin is in conflict with thick Louann salt found there. Possible lithospheric plate boundaries are outlined by linear magnetic signatures, recorded earthquake epicenters and centers of active and dormant volcanism. Magnetic, deep refraction and reflection data record a ridge‐and‐valley basement complex running parallel to these lithospheric plate boundaries. Refraction and reflection data allows the Challenger salt layer to extend northwards under the Abyssal Plain, and to connect to the Exterior Basin Louann salt layer. Eastern Cretaceous Shelf Edge paleostmctural restoration shows doming along this linear structure from the early Late Cretaceous through the Early Tertiary, which corresponds to Albian‐ early Cenomanian through Early Tertiary linear doming in the offshore area of eastern Mexico. Eastern Mexico's Tuxlas volcanic field appears to be part of the Trans‐Mexico neovolcanic belt that has been relocated along a transform fault. Other lines of evidence ar

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Mineralogical studies of Tertiary subsurface sediments in the Niger Delta have shown that smectite, kaolinite, mixed‐layer illite/smectite and illite are the principal clay minerals, with subordinate quantities of chlorite. Clays from the Recent delta have similar mineralogical compositions.Sediments in the eastern Niger Delta are contributed by rivers which drain the Oban and Bamenda Massifs, and the Tertiary volcanics and Cretaceous sediments of the Benue Trough. Sediments in the central and western delta are derived by weathering of the North, Central and SW Nigerian Basement, and also from Cretaceous sediments which are drained by the Niger/Benue river systems.The clay‐mineral assemblages of the western, central and eastern Niger Delta sequences differ. These differences are thought to be related to geothermal gradients, environments of deposition, source materials, pore‐waters chemistry and basin tectonics.Clay‐mineral assemblages from nine wells in the Niger Delta are used in this study as a possible means of correlation. A relationship can be established between clay mineralogy and the occurrence of hydrocarbons in the wells inves

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The Amik ‐ Reyhanli Basin is situated in the south of Turkey, near the Syrian border. The Dead Sea fault, which crosses the Lebanon and enters Turkey in the Antakya region, forms the basin's eastern boundary. Its basement is composed of Upper Cretaceous Koçali‐Karadut ophiolites. Seismic interpretations indicate that a Mio‐Pliocene structure exists in the Amik region, and this was originally interpreted by exploration geologists to be a faulted anticline. However, careful seismic interpretation now suggests that the structure is a “triangle zone”, resulting from activity in the Dead Sea fault‐zone in the east and the Amanos fault to the west. It is suggested that duplex structures related to this triangle zone are present beneath the Cretaceous ophiolites, and constitute oil‐prospective areas.Esso Oil Co. interpreted this positive structure as a faulted anticline, and recently drilled Well Amik‐1, which was dry, in order to test the oil possibilities of Tertiary elastics and carbonates. The well terminated in the Koçali‐Karadut ophiolites. The underlying duplex structures were not reached, and the oil possibilities of Upper Cretaceous and Jurassic‐Triassic carbonates in these duplexes therefor

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A magnitude 4.7 earthquake which occurred on June 2, 1993 in the vicinity of theMinagish/Umm Gudairoilfields in Kuwait was a complete surprise. It was felt over an area of about 2,500 sq. km, and the main shock was followed two days later by an aftershock with a magnitude of 3.2. Five earthquakes are known to have occurred between 1975 and 1977 in this area, but there had been no previously reported seismic activity. In Kuwait, seismic hazards could result from excessive fluid withdrawal, fluid injection, intraplate seismicity within the Arabian Plate, or from the effects of large earthquakes along the Zagros Belt. Sinkholes have been reported to form as a consequence of fluid‐withdrawal related subsidence. The spatial correlation between recent, moderate‐sized earthquakes and operating oilfields suggests that the current seismicity may be related to oil production. It is proposed that a permanent seismic network in Kuwait be established, to monitor and evalute seismic hazards, and predict damaging earthquake ev

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1994.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY