Abstract All of the components of an exhumed Devonian petroleum system occur in Orkney. These include a good quality mature source rock to bitumen-bearing sandstone reservoirs, with several separate accumulations that could have held about 1.88 billion barrels of oil. The exhumed system presents an excellent analogue for deeply buried petroleum systems offshore. Whilst lighter oils are now absent, reported oil shows occur, commonly associated with faults cutting the Eday Group. On Orkney, Middle Devonian source rocks (750 m thick) were thick lacustrine laminites (fish beds) representing some 30% of the sequence. RockEval and vitrinite analyses show the organic matter is good quality Type I and II and within the early oil window. These source rocks underwent burial until Permian inversion. Several exhumed reservoirs occur on Orkney in aeolian and fluvial sandstones with porosities from 15 to 25%. These reservoirs have been ‘breached’, losing the light-end hydrocarbons, leaving pore space oil stain and bitumen residues. Thin fluvial and sheet-floods sands found within the lake cycles have bitumen residues and provided connectivity between the thicker reservoir units. All types of trap are found including a major, broad anticline running north–south on Mainland Orkney and an unconformity with fault traps and pinchouts.

Abstract The account of the Old Red Sandstone (ORS) given by Wally Mykura (1991) in the third edition of this book remains an authoritative account containing many details which will not be repeated here. Wally Mykura wrote at a time of active controversy concerning the relation of the Grampian Block to Devonian successions south of the Highland Boundary Fault. His untimely death robbed him of the opportunity to discuss problems which have been reconciled to some extent by recent work and revision of absolute ages for the Devonian (Tucker et al . 1998). The chapter title follows tradition, recognizing that both the base and the top of the Devonian cannot generally be defined in Scotland. The Stonehaven Group of ORS facies is now thought to be as old as the Mid-Silurian (Marshall 1991) and the top of the Upper ORS passes conformably up into Carboniferous strata. The term Old Red Sandstone (discussion in Waterston 1965) was originally derived from the ‘Oelter rother Sandstein’ of Werner, and was applied to the Permian red sandstones of Germany. Phillips (1818) used ORS in its present sense, and Murchison (1839) considered it should be regarded as a system. However, it was Sedgwick & Murchison (1839) who established the Devonian system for marine strata in SW England and included the ORS within the Devonian. Old Red Sandstone is now used as a facies term and, whilst the rocks are mostly of Devonian age, there are notable exceptions. The distribution of ORS strata ( Fig. 8.1 ) shows

Abstract The Devonian–Recent tectono-stratigraphic history of the Northern, Central and Southern North Sea is here reviewed at a regional scale and four novel cross-border pseudo-Wheeler diagrams are presented to summarize the stratigraphic evolution of the cycles of basin fill and uplift/erosion. In this scheme, six first-order megasequence boundaries have been defined, characterized by extensive and long-lasting erosional hiatuses and major coastal regressions: (1) Caledonian (or Base Devonian) Unconformity; (2) Variscan–Saalian (or Base Permian) Unconformity; (3) Mid Cimmerian (or Intra-Aalenian) Unconformity; (4) Late Cimmerian (or Base Cretaceous) Unconformity; (5) Atlantean (or Near-Base Tertiary) Unconformity; and (6) Eridanos (or Mid-Miocene) Unconformity. These surfaces have been linked to regional causal factors ranging from orogenesis-related compressional uplifts, in either active plate margin settings (1) or foreland basin settings (2), to intra-plate dynamically supported uplifts associated with the development of mantle plumes (3, 5 and 6) and the end-of-rifting and associated widespread erosion of tilted fault block crests (4). The aforementioned megasequence boundaries punctuate the geodynamic evolution of the North Sea area and facilitate the subdivision of the entire the North Sea sedimentary basin fill into six megasequences, named here A–F. All of the lithostratigraphic units of the North Sea (formations and members) have been described within the context of this first-order tectono-stratigraphic framework. The correlation powers of certain stratigraphic markers are also compared and contrasted, together with the potential cross-border equivalence of sedimentary units on different sides of the political median lines.

Abstract The Carboniferous and Permian systems are important components of the basement rocks in Thailand and crop out widely. The exceptions are the Khorat Plateau, where they occur in the subsurface but are concealed beneath a thick Mesozoic cover, and in the Chao Phraya Central Plain where they are largely covered by Quaternary sediments but crop out in scattered monadnocks (Fig 5.1 ). Most Carboniferous and Permian rocks are of shallow-marine facies although siliceous sediments of ancient ocean-bottom origin are also known in places. Continental deposits are quite rare. The Carboniferous System is dominated by siliciclastic rocks except in northernmost Thailand around the Chiang Mai-Mae Hong Son area where there are large carbonate bodies. In contrast, carbonates are the dominant lithology in the Permian System, forming characteristic karst topography in the tropical humid climate. It has been quarried in some areas, such as Saraburi and Ratchaburi, for flagstones and cement production. In the 1970s and 1980s the Department of Mineral Resources (DMR), Thailand, published a series of 1:250 000 scale geological maps covering the whole of Thailand. That stratigraphic information laid the groundwork for a number of papers on the Carboniferous and Permian systems of this country ( Bunopas 1981 , 1983 , 1992 , 1994 ; DMR 2001 , 2007 ; Raksaskulwong 2002 ; Assavapatchara et al. 2006 ). In parallel with those stratigraphical works, more palaeontological aspects of Carboniferous and Permian strata were summarized ( Toriyama et al. 1975 ; Ingavat