Based on recent vegetation distribution and an integration of macropalaeobotanical and palynological information, a palaeocommunity model is explored that may permit detailed interpretations of quantitative sporomorph distribution patterns in the Jurassic and Early Cretaceous of NW-Europe in terms of changes in palaeoenvironment (sea-level, climate). The conceptual model is based on the recognition of Sporomorph Ecogroups (SEGs) that reflect broad co-existing plant communities, viz. upland, lowland, river, pioneer, coastal, and tidally-influenced SEGs. In successive palynological assemblages, shifts in the relative abundance of SEGs are thought to be indicators of sea-level changes. Climatic changes may be recognised through significant shifts within the quantitative composition of individual SEGs.

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Approximately 1300 m of Oligocene-Miocene clastic strata are exposed along the Miran River in the southeastern Tarim basin, where the adjacent Altun Shan form the topographic escarpment of the northern Tibetan Plateau. The sedimentary section is faulted against Proterozoic rocks of the Altun Shan in the footwall of the south-dipping, oblique reverse Northern Altyn Tagh fault. Oligocene-Lower Miocene strata consist of fine-grained rocks that record low-gradient depositional systems. Mid-Miocene and younger rocks consist of coarse conglomerate, derived from the Altun Shan and deposited by high-gradient depositional systems. The change to coarse, high-gradient depositional systems with detrital source areas coincident with the modern Miran River drainage is interpreted to mark the onset of uplift of the Altun Shan on the Northern Altyn Tagh fault and its erosional exhumation. The age of the change from pre-orogenic to synorogenic sedimentation is constrained by a foraminifera assemblage at the base of the conglomeratic section that includes Early-Middle Miocene planktonic foraminifera. This interpretation is also supported by apatite fission track and (U-Th)/He ages and thermal models that indicate rapid Miocene cooling, and hence, rapid exhumation of the Altun Shan. In addition to defining the age of the synorogenic section, the foraminifera assemblage contains planktonic taxa, indicating a connection to open marine waters, and benthic assemblages typical of brackish to near-sea level paleobathymetry. Thus, micropaleontologic evidence demonstrates that the Miran River locality, now at ϳ1400 m elevation, was at sea level approximately 15 million years ago. Thus, in addition to constraining the age of surface uplift and exhumation of the Altun Shan, the principal mountain range of the Tibetan Plateau in this region, as ϳ15 to 16 Ma, the foraminifera assemblage indicates that the SE Tarim basin, off the northern edge of the plateau, had an average surface uplift rate of nearly 100 m/m.y. for the past 15 million years. These results suggest that shortening in the Altun Shan and uplift of the range significantly post-dated the initiation of large-scale strike-slip on the Altyn Tagh fault, and that regional surface uplift mechanisms operated in the Tarim basin, beyond the margins of the Tibetan Plateau.

IMPF: 00.66A synthesis of the upper Moscovian sedimentotogical and palaeontological record of terrestrial habitats across the Variscan foreland and adjacent intramontane basins (an area which is referred to here as Variscan Euramerica) suggests a contraction and progressive westward shift of the coal swamps. These changes can be correlated with pulses of tectonic activity (tectonic phases) resulting from the northwards migration of the Variscan Front. This tectonic activity caused disruption to the landscapes and drainage patterns where the coat swamps were growing, which became less suitable to growth of the dominant plants of the swamps, the arborescent lycopsids. They were progressively replaced by vegetation dominated by marattialean ferns, which through a combination of slower growth and larger canopies resulted in less evapo-transpiration. This in turn caused localised reductions in rainfall, which further affected the ability of the lycopsids to dominate the swamp vegetation. These changes were initially localised and where the coat swamps were able to survive the lycopsids and pteridosperms show little change in either species diversity or biogeography, indicating that at this time there was minimal regional-scale climate change taking place. By Asturian times, however, the process had accelerated and the swamps in Variscan Euramerica became progressively replaced by predominantly conifer and cordaite vegetation that favoured much drier substrates. Except in localised pockets in intramontane basins of the Variscan Mountains, the last development of coat swamps in Variscan Euramerica was of early Cantabrian age. Further west, lycopsid-dominated coal swamps persisted for a little longer. The last remnants of the lycopsid-dominated coal swamps in the Illinois Basin disappeared probably by middle-late Cantabrian times, as the cycle of contracting wetlands and regional reductions in rainfall generated its own momentum, and no longer needed the impetus of tectonic instability. This tectonically-driven decline in the Euramerican coal swamps was probably responsible for an annual increase in atmospheric CO2 of c. 0.37 ppm, and may have been implicated in the marked increase in global temperatures near the Moscovian - Kasimovian boundary, and the onset of the Late Pennsylvanian interglacial.Peer reviewe

IMiddle Jurassic -Early Cretaceous strata are a target for oil and gas exploration in the Dutch offshore. During the initial stages of the 'Late Jurassic' offshore exploration, various oil fields and a few gas fields were discovered of which only one, the F3-FB field, proved to be economically viable.In the Northern Offshore of the Netherlands, latest Middle Jurassic (Callovian) -earliest Cretaceous (Ryazanian) strata are mostly limited to the Dutch Central Graben and Terschelling basins. Outside the Dutch Central Graben and the Terschelling Basin only thin veneers of these strata occur on the fringing highs such as the Schill Grund High and the Step Graben. The geology of this non-marine to shallow marine succession is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate changes, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. The large number of lithostratigraphic units defined in the Stratigraphic Nomenclature of the Netherlands illustrates the complexity of this time-interval.In recent years, new biostratigraphic techniques and newly acquired stratigraphic data led to the identification of a series of events which can be related to the tectonic, climatic, environmental and stratigraphic development of the 'Late Jurassic' in the Dutch Central Graben and Terschelling basins. Based on these data, three stratigraphic sequences can be recognized. Sequence 1 (Callovian -earliest Kimmeridgian) records the initiation of the Dutch Central Graben, Sequence 2 (early Kimmeridgian -early Portlandian) that of the initiation of the Terschelling Basin. During sequence 3 (late Portlandian -Ryazanian) the Dutch offshore was draped by a regional transgression. These insights have directly impact on the exploration potential, which is discussed in two play concepts. The first is a strat-trap play in the fluvial/paralic sediments of Sequence 1 in the lows between the graben boundary and salt domes. The second example is the Spiculite play, which comprises a bioclastic sandstone reservoir at the top of a dome with a 4-way dip closure. These two examples highlight the necessity of understanding the paleoenvironment and geography for assessing the future exploration potential.