The assumption that all salt in the Gulf of Mexico basin is Jurassic demands a fixed structural framework since mid‐Jurassic time. This assumption has questionable geological support and is challenged. Salt in the Salina Basin of southern Mexico has been presumed Jurassic because shallow salt at Chinameca is overlain by ammonite‐bearing Kimmeridgian — early Neocomian limestones which, in turn, are overlain by Oligocene sediments. Despite numerous salt penetrations elsewhere in the Salina Basin, the Chinameca limestone has not been encountered. Instead, the non‐piercing salt massifs directly underlie Oligo‐Miocene beds, which have also been found intercalated with the salt. Two wells that have traversed the salt found Oligocene sediments below. Field checks in the Chinameca limestone type‐locality reveal that these beds are both strongly folded and heavily brecciated. They do not overlie the salt normally, and are interpreted as slumped masses that slid from elevated fault scarps onto Oligocene evaporites during Oligocene block movements. Geological evidence supports the conclusion that the Salina salt is Oligocene, and was deposited during the worldwide Oligocene eustatic drop. Because the Salina salt is stratigraphically continuous with the salt in offshore Campeche, this also is deemed to be Oligocene. The Challenger salt has been dated as Jurassic on the basis of one palynomorph‐bearing sample cored from the cap rock of the Challenger knoll. However, the Challenger salt is in continuity with the Campeche evaporites, which suggests that it, too, is Oligocene. In view of the wide range of datable detrital material recovered from Salina salt samples, the dating of Challenger salt from a single sample of insoluble residue cap‐rock is considered premature. On the north side of the Gulf, evidence for Oligocene salt obtained earlier from the Belle Isle salt dome is supported by the presence of intra‐Frio evaporites encountered in two deep exploration wells. The probability of large deposits of Tertiary evaporites in the Gulf of Mexico leads to the interpretation that the evolution of the Gulf Basin was governed by a sequential process of deep crustal extension that persists until the present day, rather than an exclusively Jurassic extensional event as is currently accepted.

It is now popular to interpret the geological evolution of the Oman Mountains within the framework of the plate‐tectonic paradigm. Current interpretations hold that the deep‐water Hawasina sediments, huge exotic limestone blocks and the overlying Semail serpentinite originated in a Tethyan Ocean to the north of the present‐day mountains in Permian to Senonian time. In the Late Cretaceous, continental collision telescoped these oceanic rocks and thrust them southward over the autochthonous carbonate platform where they are now exposed. The origin of turbidites, debris flows and exotic blocks in the Hawasina complex is interpreted to have been a north‐facing continental margin that bordered the Tethys Ocean. Howevel; Permian to Cenomanian limestones that are exposed all along the axis of the Oman Mountains show no sign of penecontemporaneous rifing and erosion. If the supposed shelf‐edge ever existed, it is now hidden from view. There are some serious questions that counter the popular model. The long duration of deep‐water deposition is predicated upon the assumption that cleanly‐reworked shallow‐water benthonic fauna in the Hawasina turbidites were derived penecontemporaneously from shelf sediments and are therefore age indicative. This is a subjective judgment that can be challenged, because clean, recycled fossils from older consolidated formations are common constituents of deep‐water turbidites worldwide. Also, the dissolution of contemporaneous pelagic microfauna below the Carbonate Compensation Depth is supported by present‐day analogues. Where faunal inversions occur in a bedded succession, the palaeontological assumptions force a structural interpretation of repetition by thrusting. Howevel; in the Oman Mountains, massive thrusts interpreted to have horizontal displacements of over 100 km from a supposed Tethyan ocean basin appear to lack the expected disruption in the field. For example, in Wadi Miaidin, supposedly Jurassic sandstone turbidites of the Guwayza Formation (part of the Hawasina) appear to rest on the autochthonous Coniacian Muti Formation without major structural disturbance. This lack of deformation across what is interpreted to be a major thrust plane casts serious doubt upon dating criteria and demands detailed structural analyses to resolve both structural and palaeontological assumptions. In the Al Ajal area on the north flank of the Oman Mountains, intra‐volcanic sediments resting below the Semail Ophiolite, which have previously been dated as Triassic, have yielded Senonian Globotruncana. This also raises doubts about dating based upon reworked fauna in deep‐water turbidites. The tectofacies of the Hawasina sediments with ubiquitous turbidites and debris flows are typical of thick and rapidly deposited sediments in a tectonically active environment. Howevel; the ffawasina succession is relatively thin for the assumed time span, and the Permian to Cenomanian autochthonous succession of monotonous platform carbonates is indicative of structural quiescence. On the other hand, regional ex...

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Study of the fauna from a newly discovered fossiliferous outcrop of the Cove Lower Marine Band in Thornton Burn, East Lothian, has led to the correlation of this horizon with the Redesdale Ironstone in Northumberland and has thereby demonstrated the first palaeontological link between the Upper Calciferous Sandstone v in S.E. Scotland and the Lower Limestone Group in N.E. England. The collection of D x fauna made from the Thornton Burn outcrop includes goniatites, brachiopods, lamellibranchs, and crinoids. The discovery of Beyrichoceratoides redesdalensis (Hind) gives the first definite indication of the presence of B zone in the Scottish Carboniferous. Faunal lists and descriptions of some of the more interesting species are included in this paper as well as descriptions of the crinoids collected which are given in the succeeding paper by James Wright. I.

Uncertainties remain concerning the common assumption that economic oil pools result only from deep, catagenic oil generation. These uncertainties stem from the many geological criteria that point to early oil entrapment and, furthermore, from the failure to resolve problems of oil migration out of, and through, consolidated sediments. Early oil emplacement is indicated by the preferential charging of paleostructures, inhibition of diagenesis and compaction by reservoired oil, folded oil‐water contacts, and by evidence supporting the immaturity of huge heavy‐oil deposits. The uncemented and uncompacted nature of the Athabasca “tar sands”, the perfect preservation of fossil wood within them, and the tilted oil‐water contacts at the Athabasca, Peace River and Cold Lake accumulations, support geological deductions of very‐early oil emplacement, and geochemical criteria for its immaturity. If such huge volumes of oil are immature, this would be in harmony with geological observations which conclude that pools of mature oil most probably result from in‐reservoir maturation of early‐expelled, biogenically‐generated heavy oil and methane. Hydrocarbons that remain in source rocks are maturated during burial, but are immobilised by progressive loss of effective permeability.