The Antarctic Peninsula is a Mesozoic–Cenozoic magmatic arc built on Palaeozoic and younger basement. It was formed by processes related to the subduction of Pacific ocean floor at its western margin, although subduction has now ceased along most of its length. The peninsula features all the tectonic components commonly associated with a developing arc system: basement, accretionary complex, magmatic arc, arc-related basins, intra-arc extension and post-subduction volcanism. Seventeen thousand kilometres of high resolution aeromagnetic data have recently been collected in a transect across part of the arc, covering an area 290 by 230 km and incorporating examples of most of the above tectonic components. The new map reveals distinct magnetic signatures, which can now be related to each of these components in a way that was not possible with reconnaissance data sets. A characteristic magnetic anomaly pattern for each component is described and comparisons drawn with magnetic studies of other arc regions.

The Antarctic Peninsula is a Mesozoic–Cenozoic magmatic arc built on Palaeozoic and younger basement. It was formed by processes related to the subduction of Pacific ocean floor at its western margin, although subduction has now ceased along most of its length. The peninsula features all the tectonic components commonly associated with a developing arc system: basement, accretionary complex, magmatic arc, arc-related basins, intra-arc extension and post-subduction volcanism. Seventeen thousand kilometres of high resolution aeromagnetic data have recently been collected in a transect across part of the arc, covering an area 290 by 230 km and incorporating examples of most of the above tectonic components. The new map reveals distinct magnetic signatures, which can now be related to each of these components in a way that was not possible with reconnaissance data sets. A characteristic magnetic anomaly pattern for each component is described and comparisons drawn with magnetic studies of other arc regions.

The Okenyenya gabbro-syenite complex, one of a number of intrusive igneous complexes of late-Mesozoic age in northwestern Namibia, was emplaced at the time of opening of the South Atlantic Ocean. The 5-km-diameter complex comprises a wide variety of rock types that can be subdivided into two contrasting magmatic suites, one tholeiitic and the other alkaline, which were emplaced in close proximity over a time-span of ˜5 Ma. The tholeiitic suite of rocks includes picritic gabbro, olivine gabbro through quartz monzodiorite and syenite, whereas the alkaline suite includes alkaline gabbro, essexite, nepheline syenite and a range of lamprophyric rock types. Detailed petrographic, mineralogical and bulk rock geochemical data show that the earliest, saucer-shaped, intrusion of olivine gabbro-quartz monzodiorite rocks can be subdivided into an Inner Zone and an Outer Zone (each comprising three distinct intrusive units). The individual units can be readily distinguished on the basis of bulk rock geochemical variations, together with cryptic and modal mineralogical variations. An unusual feature of the intrusive body is that bulk rock and mineral compositions become more evolved with apparent depth, within the body as a whole and within each unit. Compositional variation within the individual intrusive units requires a complex interplay between in situ crystallization, variable expulsion of interstitial melt, magma recharge, and re-equilibration of primocrysts with trapped interstitial melt. Cross-cutting dykes of picritic gabbro (MgO= 13–21 %) have compositions consistent with olivine control. Incompatible trace element ratios (e.g. Zr/Nb= 12.5 ± 1.3) suggest that the picritic gabbro magmas were derived from a distinct source region compared to that giving rise to the tholeiitic olivine gabbros (Zr/Nb = 6.8 ± 1.1).

Alkaline gabbro occupies the central region of the complex and, on the basis of major, trace and rare earth element variations, can be subdivided into four distinct intrusive bodies, interpreted as remnant magma chambers, each having experienced variable degrees of crystal accumulation. In places, magma chamber processes have given rise to centimetre-scale rhythmic layering. Incompatible trace element ratios (e.g. Zr/Nb = 4.4 ± 1.2) serve to distinguish the source region of the alkaline gabbro magmas from those giving rise to the tholeiitic suite of magmas. Younger rocks of both the tholeiitic and alkaline suites show strong evidence of the effects of extensive crystal fractionation. The quartz syenite is characterized by a strong negative Eu anomaly indicative of substantial feldspar fractionation and also shows evidence for direct contamination by earlier gabbro, whereas the syenite shows evidence for feldspar accumulation. Both syenites have geochemical characteristics suggesting consanguinity with the Outer Zone rocks of the olivine gabbro-quartz monzodiorite intrusion. In contrast, the essexite and nepheline syenite compositions are qualitatively consistent with derivation from one of the alkaline gabbro magmas by extensive fractionation of plagioclase, clinopyroxene, olivine and amphibole. The final stage of magmatism is represented by a suite of alkaline and ultramafic lamprophyres emplaced as dykes and diatremes, the latter carrying a variety of megacrystic and xenolithic material, including mantle nodules. The alternation between tholeiitic and alkaline magmatism evident within the Okenyenya complex is similar to that characteristic of the evolution of many ocean island volcanoes.

The Okenyenya gabbro–syenite complex, one of a number of intrusive igneous complexes of late-Mesozoic age in northwestern Namibia, was emplaced at the time of opening of the South Atlantic Ocean. The 5-km-diameter complex comprises a wide variety of rock types that can be subdivided into two contrasting magmatic suites, one tholeiitic and the other alkaline, which were emplaced in close proximity over a time-span of ~5 Ma. The tholeiitic suite of rocks includes picritic gabbro, olivine gabbro through quartz monzodiorite and syenite, whereas the alkaline suite includes alkaline gabbro, essexite, nepheline syenite and a range of lamprophyric rock types. Detailed petrographic, mineralogical and bulk rock geochemical data show that the earliest, saucer-shaped, intrusion of olivine gabbro–quartz monzodiorite rocks can be subdivided into an Inner Zone and an Outer Zone (each comprising three distinct intrusive units). The individual units can be readily distinguished on the basis of bulk rock geochemical variations, together with cryptic and modal mineralogical variations. An unusual feature of the intrusive body is that bulk rock and mineral compositions become more evolved with apparent depth, within the body as a whole and within each unit. Compositional variation within the individual intrusive units requires a complex interplay between in situ crystallization, variable expulsion of interstitial melt, magma recharge, and re-equilibration of primocrysts with trapped interstitial melt. Cross-cutting dykes of picritic gabbro (MgO = 13–21 %) have compositions consistent with olivine control. Incompatible trace element ratios (e.g. Zr/Nb= 12.5 ± 1.3) suggest that the picritic gabbro magmas were derived from a distinct source region compared to that giving rise to the tholeiitic olivine gabbros (Zr/Nb = 6.8 ± 1.1).

Alkaline gabbro occupies the central region of the complex and, on the basis of major, trace and rare earth element variations, can be subdivided into four distinct intrusive bodies, interpreted as remnant magma chambers, each having experienced variable degrees of crystal accumulation. In places, magma chamber processes have given rise to centimetre-scale rhythmic layering. Incompatible trace element ratios (e.g. Zr/Nb = 4.4 ± 1.2) serve to distinguish the source region of the alkaline gabbro magmas from those giving rise to the tholeiitic suite of magmas. Younger rocks of both the tholeiitic and alkaline suites show strong evidence of the effects of extensive crystal fractionation. The quartz syenite is characterized by a strong negative Eu anomaly indicative of substantial feldspar fractionation and also shows evidence for direct contamination by earlier gabbro, whereas the syenite shows evidence for feldspar accumulation. Both syenites have geochemical characteristics suggesting consanguinity with the Outer Zone rocks of the olivine gabbro–quartz monzodiorite intrusion. In contrast, the essexite and nepheline syenite compositions are qualitatively consistent with derivation from one of the alkaline gabbro magmas by extensive fractionation of plagioclase, clinopyroxene, olivine and amphibole. The final stage of magmatism is represented by a suite of alkaline and ultramafic lamprophyres emplaced as dykes and diatremes, the latter carrying a variety of megacrystic and xenolithic material, including mantle nodules. The alternation between tholeiitic and alkaline magmatism evident within the Okenyenya complex is similar to that characteristic of the evolution of many ocean island volcanoes.

The first specimen of the ankylosaur genus Polacanthus from the mainland Barremian of southeast England is described as Polacanthus rudgwickensis sp.nov. Polacanthus rudgwickensis is larger than Polacanthus foxii, and there are significant differences in the dermal armour, the tibia and caudal vertebrae of the two species. Polacanthus foxii appears to be restricted at present to the Isle of Wight with one specimen from southwest England, whilst Polacanthus rudgwickensis is only known from Sussex. This geographical distribution, the palaeobiological implications and possible sexual dimorphism are discussed for this genus.

The first specimen of the ankylosaur genus Polacanthus from the mainland Barremian of southeast England is described as Polacanthus rudgwickensis sp.nov. Polacanthus rudgwickensis is larger than Polacanthus foxii, and there are significant differences in the dermal armour, the tibia and caudal vertebrae of the two species. Polacanthus foxii appears to be restricted at present to the Isle of Wight with one specimen from southwest England, whilst Polacanthus rudgwickensis is only known from Sussex. This geographical distribution, the palaeobiological implications and possible sexual dimorphism are discussed for this genus.

An early fabric is preserved in pseudomorphs of contact metamorphic cordierite and andalusite found in hornfelsed Dalradian rocks at the NW margin of the Ben Vuirich Granite. As previous work had suggested that this fabric may be of regional tectonic (D1) origin, and taken as evidence that a pre-590 Ma (Neoproterozoic) erogenic event had affected the Dalradian Supergroup, the textures found in the hornfelses and their porphryoblasts are illustrated and described in detail. Three types of hornfels are recorded: unspotted, cordierite-, and andalusite-bearing. Cordierite was altered to mica, garnet, and kyanite, and andalusite pseudomorphed by kyanite, during the subsequent D2 regional metamorphism.

The early fabric is finely spaced and associated with a weak shape fabric, except in the higher grade hornfelses where it is more intensely developed and formed during the deformation of irregularly shaped, cross-cutting granitic veinlets. It is concluded that the hornfels fabric is probably bedding modified by intrusion-related deformation, rather than a D1 fabric parallel to bedding. The implication of this finding is that intrusion of the Ben Vuirich Granite occurred during the Vendian (c.650 Ma) rifting phase, at about the time that the Tayvallich lavas were being deposited, and before any significant deformation of the Dalradian rocks had taken place. There is no unambiguous evidence to show that the early fabric in the hornfels at Ben Vuirich formed during a Precambrian, regional-scale, deformation of the Dalradian block.

An early fabric is preserved in pseudomorphs of contact metamorphic cordierite and andalusite found in hornfelsed Dalradian rocks at the NW margin of the Ben Vuirich Granite. As previous work had suggested that this fabric may be of regional tectonic (D1) origin, and taken as evidence that a pre-590 Ma (Neoproterozoic) orogenic event had affected the Dalradian Supergroup, the textures found in the hornfelses and their porphryoblasts are illustrated and described in detail. Three types of hornfels are recorded: unspotted, cordierite-, and andalusite-bearing. Cordierite was altered to mica, garnet, and kyanite, and andalusite pseudomorphed by kyanite, during the subsequent D2 regional metamorphism.

The early fabric is finely spaced and associated with a weak shape fabric, except in the higher grade hornfelses where it is more intensely developed and formed during the deformation of irregularly shaped, cross-cutting granitic veinlets. It is concluded that the hornfels fabric is probably bedding modified by intrusion-related deformation, rather than a D1 fabric parallel to bedding. The implication of this finding is that intrusion of the Ben Vuirich Granite occurred during the Vendian (c.650 Ma) rifting phase, at about the time that the Tayvallich lavas were being deposited, and before any significant deformation of the Dalradian rocks had taken place. There is no unambiguous evidence to show that the early fabric in the hornfels at Ben Vuirich formed during a Precambrian, regional-scale, deformation of the Dalradian block.

The blueschists of Andros Island consist of a probable Permian-Eocene metasedimentary rock succession (meta-sandstone, marble, chert), containing large bodies of magmatic rock (serpentinized ultra-mafic rocks, gabbros and granodiorite). The development of a layer-parallel foliation and axial plane cleavage, followed by two phases of intense deformation with recumbent folding, almost completely obliterated the primary bedding and stratigraphic relations in the metamorphic complex. The main features of the geological evolution of Andros, that is, the original environment of deposition and the character and direction of tectonic transport, have been hitherto unclear because of this deformation. The present sedimentological and structural study has led to the discovery of preserved relics of primary sedimentary structures, including graded bedding and chaotic sedimentary breccias. Associated turbidite and olistostromic formations can be recognized at three stratigraphic levels in the Andros Island’s reconstructed column. Some layers of the metasedimentary rocks, having preserved clear signs of the layer’s top and bottom, were also used for the identification of the primary anticlines and synclines among widespread developed recumbent folds. This study has shown that the structural style of the last synmetamorphic recumbent folds with northwest vergence is the same, independent of the direction of the present axial plane dips. This data can be interpreted as a result of monovergent tectonic transport in the last metamorphic event. The analysis of structural relations between primary bedding and first synmetamorphic foliation proves that most of the stratigraphic succession has been preserved in a normal stratigraphic position after the first blueschist and before the second greenschist deformation stage.

The blueschists of Andros Island consist of a probable Permian-Eocene metasedimentary rock succession (meta-sandstone, marble, chert), containing large bodies of magmatic rock (serpentinized ultra-mafic rocks, gabbros and granodiorite). The development of a layer-parallel foliation and axial plane cleavage, followed by two phases of intense deformation with recumbent folding, almost completely obliterated the primary bedding and stratigraphic relations in the metamorphic complex. The main features of the geological evolution of Andros, that is, the original environment of deposition and the character and direction of tectonic transport, have been hitherto unclear because of this deformation. The present sedimentological and structural study has led to the discovery of preserved relics of primary sedimentary structures, including graded bedding and chaotic sedimentary breccias. Associated turbidite and olistostromic formations can be recognized at three stratigraphic levels in the Andros Island's reconstructed column. Some layers of the metasedimentary rocks, having preserved clear signs of the layer's top and bottom, were also used for the identification of the primary anticlines and synclines among widespread developed recumbent folds. This study has shown that the structural style of the last synmetamorphic recumbent folds with northwest vergence is the same, independent of the direction of the present axial plane dips. This data can be interpreted as a result of monovergent tectonic transport in the last metamorphic event. The analysis of structural relations between primary bedding and first synmetamorphic foliation proves that most of the stratigraphic succession has been preserved in a normal stratigraphic position after the first blueschist and before the second greenschist deformation stage.

A fossil flora of Miocene age has been preserved by karstic agencies in a solution subsidence complex developed in a large exotic block of limestone, part of the Gwna Group mélange (?Cambrian), at Trwyn y Parc, Cemaes Bay, Anglesey. The flora suggests that the Menaian Surface and the Snowdonian Mountain block were already well established landscape features by the end of the Miocene. The wider geomorphological implications of the find are briefly discussed.

A fossil flora of Miocene age has been preserved by karstic agencies in a solution subsidence complex developed in a large exotic block of limestone, part of the Gwna Group mélange (?Cambrian), at Trwyn y Parc, Cemaes Bay, Anglesey. The flora suggests that the Menaian Surface and the Snowdonian Mountain block were already well established landscape features by the end of the Miocene. The wider geomorphological implications of the find are briefly discussed.

Dolomites formed in upper Turonian–lower Coniacian Cueva Formation carbonates in the El Ribero area (Burgos province, northern Spain) have been investigated. Carbonate banks up to 30 m thick are massive or poorly structured along several kilometres, but at this location they contain clinoforms that dip away from the central area of the Rosío diapir, producing a dome-like structure. Three main diagenetic processes affected the El Ribero carbonates: silicification, dolomitization and subsequent dedolomitization. Silicification was mainly early, producing chert nodules from Thalassinoides burrows and replacing anhydrite cauliflower-type geodes, converting them into quartz geodes and silicified fossils (corals, echinoderms and oysters). Dolomite occurs immediately below the first order Coniacian Sequence Boundary (CSB) and is restricted to the diapiric area of influence. The dolomite has a flat top, whereas its base is irregular, suggesting downward movement of dolomitic fluids. Isotopic data from the dolomite (δ18O=−3.4‰PDB and δ13C= 1.1‰PDB) are similar to values reported from both evaporative and mixing zone dolomite. Finally, an intense and locally destructive dedolomitization produced significant dissolution. This affected the unsilicified organisms, and was followed by the development of meteoric-water poikilotopic calcite cements and radiaxial calcite geodes infilling dissolution cavities (isotopic values for later calcite are δ18O=−7.4‰PDB and δ13C=−9.0‰PDB). In addition, palaeokarstic horizons formed as a result of diapiric uplifts that caused collapse structures and vugs of several centimetres in size infilled by laminated sediments. All these features suggest that the diapiric movements could have been synsedimentary and particularly active during the Cueva Formation deposition.

Dolomites formed in upper Turonian–lower Coniacian Cueva Formation carbonates in the El Ribero area (Burgos province, northern Spain) have been investigated. Carbonate banks up to 30 m thick are massive or poorly structured along several kilometres, but at this location they contain clinoforms that dip away from the central area of the Rosío diapir, producing a dome-like structure. Three main diagenetic processes affected the El Ribero carbonates: silicification, dolomitization and subsequent dedolomitization. Silicification was mainly early, producing chert nodules from Thalassinoides burrows and replacing anhydrite cauliflower-type geodes, converting them into quartz geodes and silicified fossils (corals, echinoderms and oysters). Dolomite occurs immediately below the first order Coniacian Sequence Boundary (CSB) and is restricted to the diapiric area of influence. The dolomite has a flat top, whereas its base is irregular, suggesting downward movement of dolomitic fluids. Isotopic data from the dolomite (δ18O=-3.4‰PDB and δ13C= 1.1 ‰PDB) are similar to values reported from both evaporative and mixing zone dolomite. Finally, an intense and locally destructive dedolomitization produced significant dissolution. This affected the unsilicified organisms, and was followed by the development of meteoric-water poikilotopic calcite cements and radiaxial calcite geodes infilling dissolution cavities (isotopic values for later calcite are α18O=-7.4‰PDB and δ13C=-9.0‰PDB). In addition, palaeokarstic horizons formed as a result of diapiric uplifts that caused collapse structures and vugs of several centimetres in size infilled by laminated sediments. All these features suggest that the diapiric movements could have been synsedimentary and particularly active during the Cueva Formation deposition.

The South Wales Coalfield comprises Namurian, Westphalian and Stephanian sequences which developed in the external zone of the Variscan Orogenic Belt. Sedimentation is thought to have been concentrated in a paralic basin related to crustal flexure in a foreland basin setting, linked to Variscan tectonic loading to the south. It has long been recognized that coal rank varies across the Coalfield, from high-volatile bituminous rank in the east and southeast, to anthracite in the northwest. This is confirmed here on the basis of comprehensive volatile matter and vitrinite reflectance data sets, computer contoured to generate isovol and isoreflectance maps. A steady increase in coalification with depth is also recorded. Clay mineral investigations show the presence of illite and kaolinite across the entire coalfield area, while neither pyrophyllite nor mixed clays were detected. Illite crystallinity values from mudstones are in the range 1.20–0.44 Δ°2θ.

Vitrinite reflectance data indicate maturation temperatures in the range 123–290 °C; clay mineral and IC values suggest temperatures up to 230°C, while previous descriptions of pyrophyllite from the Coalfield would allow locally for even higher temperatures. Coalification appears to have occurred rapidly (maximum 5 Ma) following deposition, implying high heat flux during Westphalian times. This is also indicated by fluid inclusion evidence from quartz crystals in clay ironstone nodules.

The inference is of a high geothermal gradient (c. 50°C km-1) during Westphalian times, contrasting with an earlier gradient estimate of 20–37°C km-1. Relatively high gradients have also been determined previously for the Ruhr Coalfield, which occupies a similar tectonic setting in the external zone of the Variscan Orogenic Belt. Such a gradient is at odds with the proposed foreland basin tectonic setting for the South Wales Coalfield, in which low geothermal gradients would be anticipated.

The South Wales Coalfield comprises Namurian, Westphalian and Stephanian sequences which developed in the external zone of the Variscan Orogenic Belt. Sedimentation is thought to have been concentrated in a paralic basin related to crustal flexure in a foreland basin setting, linked to Variscan tectonic loading to the south. It has long been recognized that coal rank varies across the Coalfield, from high-volatile bituminous rank in the east and southeast, to anthracite in the northwest. This is confirmed here on the basis of comprehensive volatile matter and vitrinite reflectance data sets, computer contoured to generate isovol and isoreflectance maps. A steady increase in coalification with depth is also recorded. Clay mineral investigations show the presence of illite and kaolinite across the entire coalfield area, while neither pyrophyllite nor mixed clays were detected. Illite crystallinity values from mudstones are in the range 1.20–0.44 Δ°2θ.

Vitrinite reflectance data indicate maturation temperatures in the range 123–290 °C; clay mineral and IC values suggest temperatures up to 230°C, while previous descriptions of pyrophyllite from the Coalfield would allow locally for even higher temperatures. Coalification appears to have occurred rapidly (maximum 5 Ma) following deposition, implying high heat flux during Westphalian times. This is also indicated by fluid inclusion evidence from quartz crystals in clay ironstone nodules.

The inference is of a high geothermal gradient (c. 50 °C km−1) during Westphalian times, contrasting with an earlier gradient estimate of 20–37°C km−1. Relatively high gradients have also been determined previously for the Ruhr Coalfield, which occupies a similar tectonic setting in the external zone of the Variscan Orogenic Belt. Such a gradient is at odds with the proposed foreland basin tectonic setting for the South Wales Coalfield, in which low geothermal gradients would be anticipated.

Porosity measurements of 22 Upper Cretaceous Chalk samples, and mean Chalk porosities derived from sonic logs in three wells, were used to quantify apparent exhumation (height above maximum burial-depth) in the onshore Cleveland Basin/East Midlands Shelf. Late Cretaceous/Tertiary exhumation of the East Midlands Shelf resulted in the removal of 1.2 km of section near the coast and more than 2 km of section inland, to the west. The southern margin of the Cleveland Basin was exhumed by 2 km, and exhumation increases northwards towards the recognized inversion axis running east–west along the basin’s centre. The northwards increasing exhumation associated with the east–west trending inversion axis of the Cleveland Basin is superimposed upon the regional westward trend of increasing exhumation of eastern England. These two trends control the outcrop distribution of the Upper Cretaceous Chalk in the Cleveland Basin/East Midlands Shelf.

Porosity measurements of 22 Upper Cretaceous Chalk samples, and mean Chalk porosities derived from sonic logs in three wells, were used to quantify apparent exhumation (height above maximum burial-depth) in the onshore Cleveland Basin/East Midlands Shelf. Late Cretaceous/Tertiary exhumation of the East Midlands Shelf resulted in the removal of 1.2 km of section near the coast and more than 2 km of section inland, to the west. The southern margin of the Cleveland Basin was exhumed by 2 km, and exhumation increases northwards towards the recognized inversion axis running east–west along the basin's centre. The northwards increasing exhumation associated with the east–west trending inversion axis of the Cleveland Basin is superimposed upon the regional westward trend of increasing exhumation of eastern England. These two trends control the outcrop distribution of the Upper Cretaceous Chalk in the Cleveland Basin/East Midlands Shelf.

Recent results in the geological history of Indonesia indicate that Timor island (Indonesia) has a Gondwanian origin and emerged about 3.5 Ma ago. The Palaeogene anthracothere artiodactyl described by von Koenigswald in 1967 from this island cannot be autochthonous because of its Laurasiatic affinities. The geological history and structure of Timor is summarized, and the origins of the occurrence of this anthracothere (a floating carcass washed up on the Eocene formations of Timor, a continental Asian fossil recently brought by traders, and an hypothetic partial Asian origin of Timor) are discussed.

Recent results in the geological history of Indonesia indicate that Timor island (Indonesia) has a Gondwanian origin and emerged about 3.5 Ma ago. The Palaeogene anthracothere artiodactyl described by von Koenigswald in 1967 from this island cannot be autochthonous because of its Laurasiatic affinities. The geological history and structure of Timor is summarized, and the origins of the occurrence of this anthracothere (a floating carcass washed up on the Eocene formations of Timor, a continental Asian fossil recently brought by traders, and an hypothetic partial Asian origin of Timor) are discussed.