Abstract Cyclothems are stratigraphic sequences deposited during glacial-eustatic transgressive–regressive inundations of land. Major cyclothems are most complete on lower shelves and become separated by exposure surfaces higher on the shelf. Minor cyclothems extend only onto lower shelves or are parasequences reflecting a reversal of sea level during general phases of transgression or regression. In Midcontinent North America, highstand condensed intervals of major cyclothems are conodont-rich black shales correlated eastwards into the Illinois and Appalachian basins. The number of cyclothems decreased by loss of lesser cyclothems across these basins, signifying an eastwards increase in their depositional elevations. Generalized palaeogeographical maps show that facies successions developed across these basins during a single major interglacial transgression and regression. The control of glacial eustasy by the interaction of Earth's orbital parameters, along with radiometric dating, allows subdivision of the cyclothem succession into c. 400 kyr groupings, which reflect the longest eccentricity cycle and facilitates global correlation. Delineation of the basinward extents of regression from the disappearance of exposure surfaces elucidates the history of basin-margin development. Major cyclothems that underwent reversals of general sea-level trend display ‘splays’ of lesser cycles onto the higher shelf. Geochemical cycles ‘nested’ within deepest-water shales on low shelves appear as thin nearshore facies between exposure surfaces at their high-shelf shorelines.

Abstract A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the US Desmoinesian–Missourian boundary) – Event 3. Two earlier significant changes occurred, first in the mid-Moscovian (Atokan–Desmoinesian; ∼Bolsovian–Asturian) – Event 1, and the second in the late Moscovian (mid-Desmoinesian; mid-Asturian) – Event 2. These changes occurred during a time period of dynamic and complex physical change in Euramerican Pangaea driven by changes in polar ice volume and accompanying changes in sea level, atmospheric circulation, rainfall, and temperature. During the Event 3 change, hyperbolized as ‘the Carboniferous rainforest collapse’, lycopsid dominance of (mostly peat) swamps changed to marattialean tree-fern and medullosan pteridosperm dominance, and biodiversity decreased. Event 3 encompassed one glacial–interglacial cycle and included vegetational turnover in other wetland habitats. For several subsequent glacial–interglacial cycles peatland dominance varied, known from palynology, before stabilizing. These vegetational changes likely reflect climatic events driving unidirectional, non-reversible wetland vegetational changes, during cooler, wetter parts of glacial–interglacial cycles. Discussion is complicated by different placements of crucial stratigraphic boundaries, but under the same names, compromising both clear communication and understanding of the literature. Not the least is the floating base of the Cantabrian Substage, together with the position of the Westphalian–Stephanian Stage boundary.

Abstract The Middle–Late Pennsylvanian Subperiod was marked by recurrent glacial–interglacial cycles superimposed on a longer-term trend of increasing aridity. Wetland and drought-tolerant floras responded with repeated migrations in the tropics, and a major plant turnover occurred in swamp ecosystems in parts of Euramerica near the Middle–Late Pennsylvanian boundary. However, the corresponding ecological and evolutionary responses of insects and other terrestrial arthropods are poorly understood. Here, we review the record of plant–arthropod interactions and analyse origination and extinction rates of insects during the Middle–Late Pennsylvanian. Although preliminary, plant–arthropod associations broadly persist through the Middle–Late Pennsylvanian boundary, and new damage types and host-plant associations first appear in the Late Pennsylvanian, possibly related to increased availability of accessible vascular and foliar tissues associated with the shift from arborescent lycopsid to tree and seed fern dominance in Euramerican wetlands. Likewise, our analysis of the insect body fossil record does not suggest especially high rates of origination or extinction during this interval. Together, these results suggest that insects did not suffer major extinctions during the Middle–Late Pennsylvanian, despite short- and long-term changes in climate and environmental conditions.

Abstract A dataset with pore pressures from more than 1000 exploration wells has been used to investigate the dynamics of aquifer systems in the Norwegian Continental Shelf (NCS). Variations in aquifer pressures reflect flow of porewater through permeable rocks over geological time. Strongly overpressured regimes are formed within confined aquifers in subsiding areas, where fluid flow out of the aquifer is controlled by vertical seepage. In transitional pressure regimes, fluid flows within permeable beds towards areas with hydrostatic pressures. In the hydrostatic regime, pressure differences result from density differences due to varying formation water salinity and by hydrocarbon columns. An underpressured regime has been encountered in confined aquifers in the platform areas of the Barents Sea, and is related to net uplift and erosion. In the case studies, pressure differences are interpreted in the context of the relevant pressure regime, and with a dynamic approach where segment boundaries and cap rocks are regarded as low-permeability restrictions rather than barriers. The present distribution of pressure regimes was developed over the last few million years due to rapid Pleistocene sedimentation and erosion processes.