摘要:

A detailed study of the magnetic and seismic data in and adjacent to the NW Carboniferous Basin of Ireland suggests that surface faults, mainly in the Carboniferous and Devonian rocks, are directly related to regional faults on older subjacent basement. These regional faults have controlled the tectonics of the area since the Late PreCambrian.The primary faults are associated with the steeply‐dipping fault zone whose presence is marked by the Fair Head‐Clew Bay magnetic linear (FCL). The FCL can be traced to the east where it becomes concident with the Highland Boundary Fault zone of Scotland. The Highland Boundary Fault maarks the southern limit of the Dalradian rocks. and was a plate margin beignning in Late Combrian‐ Early Ordovician (Grampian)times. In ireland, the FCL also marks this Lower Paleozoic plate boundary. Associated secondary magnetic linears (linears) indicate the presences of other basement fault caused by mkovement on the FCL, which were rejuvencated during the Upper Paleozoic.Large magnitude movement on these fault‐systems commenced druging the Early Paleozoic and continued through the Devonian, with lesser magnitude movement continuing until after the Carboniferous. The abrupt change from the more than 4,500 m of Paleozoic sediments present south of the FCL to approximately 1,500 m of sediments to the north is a result of complex wrench‐faulting, shown by flower structures in seismic profiles, Fold orientations and fold and fault deflections near the major sinistral fault are also consistent with formation within a sinistral str

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Recent literature on carbonate source rocks is reviewed, particular importance being attached to those papers which give details of lithology and depositional environment, as well as details relating to the organic matter in the rock. It is demonstrated that depositional and environmental criteria which have been applied to other source rocks are equally valid for carbonates. Evidence is presented which upholds the view that clay mineral catalysis is minimal in these rocks. Another feature which is emphasised is that of “self‐sourcing”I.t is suggested that the evidence presented in the papers reviewed calls for the recognition of two modes of “self‐sourcing” i.e. the oil or gas canbe truly indigenous and formed where it is found, or it can have migrated within the carbonate complex. Supporting evidence ?om experimental work, both published and unpublished, is presented to support the main conclusions o

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Evaluation of existing magnetometric, gravimetric, seismic and well data indicates that a large basin, some 300 km long, 100 km wide and up to 13.5 km deep, occupies the greater part of the Sinai‐Israel offshore area. The basin, referred to here as the Pleshet Basin, is flanked by a series of magnetic and gravimetric anomalies, interpreted as being caused by basement highs.None of the wells drilled in the basin penetrated the Jurassic section. It is suggested, however, that the thick sedimentary sequence filling the basin includes strata of Paleozoic to Quaternary age.Wells drilled in the SE part of the basin showed an increase in clastic content in a NW direction. The source of these clastics is therefore to be sought in the west. It is perhaps the basement ridge that presumably forms the western flank of the basin, or even a large land‐mass further away.The Pleshet Basin occupies a position similar to that of the prolific basins of the Middle East within the unstable shelf belt that surrounds the Arabo‐Nubian Massif. It here postulated that the Pleshet Basin is a potentially hydrocarbon‐generative dep

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Limited geological events are occasionally observable, but petroleum geochemistry is inevitably a wholly inferential science. It can only be simulated in the laboratory, with occasional help from industrial‐scale work, by using the Arrhenius equation to convert observations in human time to geotime by means of temperature change.There are difficulties here. First, the Arrhenius equation is purely empirical. The analogy with the theoretically rigorous van't Hoff isochore cannot give the Arrhenius equation any more than empirical status. A departure from linearity unobservable in human time could well make the extrapolation to geotime subject to significant errors.Secondly, the inability to define petroleum generation in terms of specific molecules prevents the assignment of specific activation energies to specific reactions. Energies of activation can vary significantly between even similar reactions.Thirdly, catalysis can accelerate a reaction by ten or twenty powers of ten, and even variations in natural clays can alter reaction rates almost a thousandfold.Each of these three factors could easily introduce errors of two powers of ten in translating laboratory simulation to geotime.From equilibrium considerations, petroleum generation and degeneration belong to a continuous spectrum of reactions in which very large molecules are broken down into smaller ones, and ultimately methane. Pressure inhibits the equilibrium of such reactions to such an extent, especially as the molecules become smaller, that there can be no validity to simulation experiments which are not carried out at geopressures.Altogether. it seems unlikely that the age of oil can be limited by thermodynamic considerations.Finally, an inorganic origin for some petroleum ought not to be completely ignore

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Compilation of hydrologic data for deep aquifers in the Michigan Basin makes it feasible to test the hydraulic theory of hydrocarbon migration in Michigan. Comparison of equipotential surfaces and patterns of hydrocarbon deposits shows that commercial oil deposits in most aquifers and the more prolific gas deposits in the St. Peter Sandstone are preferentially associated with regional groundwater discharge areas, as predicted by the hydraulic theory. Shallow natural gas deposits occur in regional groundwater recharge areas of Devonian and Mississippian aquifers. The gases in these deposits have chemical compositions suggesting a biogenic origin. Their occurrence in regional recharge regions is believed to be due to a combination of high interfacial methane‐water tension due to low subsurface temperature and pressure and water‐saturated, gas‐impermeable rock surrounding the dep

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

It is customary to interpret ophiolite belts, including those of the Middle East, as remnants of oceanic crust. However, the mere presence of an ophiolite belt by itself is not proof that it is the site of a former subduction zone.It is argued in this paper that no subduction zone is, or ever was, present in the Middle East. Earthquake‐intensity and earthquake‐epicentre maps show that shocks of magnitude 6.5 and greater (Richter scale) take place in many areas far removed from proposed subduction zones. Even the major proposed subduction zone of the Middle East‐the Zagros “suture” or Zagros “crush zone”‐ has no associated volcanic rocks, and therefore lacks the lithological suit which typifies so‐called subduction zones. Moreover, basement‐rock exposures and basement reached in deep boreholes indicate that at least the major part of the Zagros Fold Belt is underlain by continental, non‐oceanic crust.The fact that identical lithofacies of the same, late PreCambrian through Early Tertiary, are present on both sides of the alleged subduction zone should be enough to give one cause for thought. Well‐known and closely related faunas have been described from Early and Late Paleozoic strata on both sides of the Zagros suture for many decades.Disagreements among plate tectonicists are many. Some advocate the former presence of two or more plates in this region; others have postulated several microplates; other workers support island‐are interpretations; almost all favour the existence of at least one suture zone that marks the locus of a continent‐continent collision. Nearly all of these hypothese are mutually exclusive. Most would cease to exist if the field data were honoured. These data show that there is nothing in the geologic record to support a separation in the past of Arabia‐Africa from the

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The geochemical parameters of potential source rocks in the Ogaden Basin, Ethiopia are conducive to the presence of gas and oil. This prediction is based on Lopatin's method of calculating the time‐temperature indices of thermal maturation of organic matter in rocks. Paleozoic and Mesozoic rocks, the Bokh Shale and Hamanlei Formation respectively, are estimated to lie in a thermal zone which is appropriate for generation of petroleum, especially gas, at several localities in the Basi

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Book reviewed in this article:“Plate tectonics: how it works”, by A. Cox and R.B. Hart.“Oil‐oil and oil‐rock correlations: a chemists perspective” by 1 L. Weber''Petroleum geochemistry and exploration in the Afro‐Asian region” edited by R.K. Kumar et al.“The e˜olurion of reef commuriitie.˜” hv A.1. Fugrr.urom.“AAPG Memoir 41: Puleotrctonics and sedimentation”

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1988.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY