ALBERT

Description: Mass-balance calculations indicate that a massive amount of 13 C-depleted carbon was released into the early Danian atmosphere in volumes comparable with the younger Paleocene–Eocene Thermal Maximum (PETM). This Danian hyperthermal event (the Dan-C2) has been documented from the fill of the Boltysh meteorite crater, Ukraine. Palynofloras recovered from the Boltysh crater fill show a trend from mesic forest to savannah ecosystem dominance on a millennial scale across the hyperthermal inception with no abrupt compositional shift. This longer-term trend is overprinted by moisture availability oscillations reflecting orbital forcing. Forcing is not directly tracked by the oscillations, which are composed of mesic forest and savannah palynofloras separated by rapid critical transitions. The absence of an ecological collapse at the Dan-C2 indicates that plant ecosystems experienced dominant forcing from orbital cyclicity, rather than a stochastic temperature rise.

Description: Distinguishing axial and lateral sedimentary systems in rift basins is crucial for predicting reservoir distribution and quality, particularly where synrift strata are interrupted by mass transport complexes (MTCs). Upper Jurassic deep-marine synrift successions in the central North Sea have been studied to assess the temporal and spatial relationships of sediments and controls on reservoir quality. In the Late Jurassic, the central graben experienced erosion at rift margins, whereas adjacent grabens were starved and underfilled with marine sediments, supplied by axial and transverse systems. This study focused on sediments adjacent to a major intrabasinal high, the Josephine ridge. Data included seismic, wireline logs from 16 wells, and biostratigraphic and sedimentological analysis of 144 m (472 ft) of core. Synrift strata are dominated by mudstones but include MTCs interbedded with coarse sandstones at the rift margin and fine-grained turbidite sandstones in basinal depocenters. Petrographic and heavy mineral data indicate different provenance between MTCs and basinal turbidites. Turbidites correlate with periods of lowered relative sea level, during the initial rift phase, and record axial sediment supply. The composition of the MTCs corresponds to in situ strata on the adjacent Jade and Judy horsts. The distribution of MTCs implies formation by crestal collapse horsts during the rift climax and represents a transverse system, with no genetic relationship to axial turbidites. In starved deep-marine basins, fine-grained, well-sorted axial systems may provide the most extensive reservoirs. Transverse systems derived from isolated horsts are typically coarse-grained, poorly sorted, and spatially restricted, being unlikely to provide significant reservoir material.

Description: Following the intra-volcanic Rosebank discovery in the Faroe–Shetland Basin, NE Atlantic, there has been a need to find suitable analogues to characterize reservoir architectures, connectivities and compartmentalization of interlava clastic beds. The Faroe Islands, situated c. 160–190 km to the NW of this discovery, are an exposed remnant of the Palaeogene lava field host and the near-vertical cliff sections afford the opportunity to map lateral variations over many kilometres. This was achieved through 3D photogrammetry based on high-resolution digital photographs taken from a helicopter. The study focused on the Eocene Enni Formation, which is dominated by a mixture of simple and compound lava flows commonly separated by minor volcaniclastic beds, including the widespread Argir Beds. In general, the interlava beds are tabular shaped and 〈1 to c. 6 m thick. Locally they thicken in depressions formed by the wedging out or differential erosion of underlying lava flow lobes. Connectivity may be caused by the wedging out of successive lava flows leading to the lateral merging of interlava beds or more rarely be hydraulically connected via conglomeratic fills of major channels. Lateral compartmentalization may be caused by the intersection of interlava beds by dykes, lava tubes, lava-filled channels or reverse faults.

Description: The Lagavulin exploration well 217/15-1Z penetrated a c . 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene–Eocene boundary in the NE Faroe–Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene–Eocene boundary. Basalts from the lower c . 1.3 km have low TiO 2 (〈1.5 wt%) and low Zr/Y (2–3), with olivine-phyric picrites towards the base (Mg# 70–82; olivine Fo 85–91 ). The hiatus correlates precisely with a change to high-TiO 2 (2.5–3.2 wt%), high-Zr/Y (〉4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area. Supplementary material: All raw geochemical data and supplementary analyses are available at http://www.geolsoc.org.uk/SUP18888 .

Description: Basalt dykes from the regional dyke swarm of the British Palaeogene Igneous Province (BPIP) were emplaced parallel to structural lineaments linking onshore and offshore volcanic edifices. Basalts that underwent minimal interaction with the crust have Mg# 60–75, Nd 58 c . 8, 206 Pb/ 204 Pb c . 17.5, 18 O 5.9 ± 0.3, and 87 Sr/ 86 Sr 〈0.7040. Basalts with convex-upwards REE profiles ([La/Sm] N 〈1; [Sm/Yb] N 〉1) were generated by limited extents of melting (〈10%) in the garnet–spinel transition of the upper mantle. Basalts with LREE-depleted ([La/Sm] N 〈1) or flat REE profiles require substantial (up to 20%) melting of spinel lherzolite. Modelling of major element compositions and olivine equilibration temperatures indicates that the mantle potential temperature was a maximum of 1530 °C beneath the BPIP at 58–60 Ma. Magmatism occurred at the periphery of a mantle thermal anomaly (proto-Iceland plume; T P ≤ 1560 °C) centred beneath western Greenland. The distribution of BPIP magmas was controlled by extensional tectonism driven by plate boundary forces resulting from plate reorganizations in the northern hemisphere starting at c . 62 Ma. The well-known mildly alkaline lava piles of Skye and Mull represent volcanoes on the flanks of the resulting rift system.

Description: 〈span〉〈div〉Abstract〈/div〉The NE Atlantic margin is one of the last frontier areas of hydrocarbon exploration within the UK Continental Shelf. In 2004, a major oil and gas discovery (Rosebank) was made within Paleocene–Eocene-age lavas in the Faroe–Shetland Basin. The Rosebank Field consists of intra-basaltic terrestrial to marginal-marine reservoir sequences, separated by basaltic lava flows and volcaniclastics. Despite the identification of a major intra-lava-incised drainage system running parallel to the SW–NE-trending Rosebank Field, the controls on the distribution of both the volcanics and the intra-basaltic sediments were previously unclear, in part due to the difficulties that volcanic sequences pose to seismic acquisition, processing and interpretation. This has led to uncertainty in defining the wider intra-basaltic play. However, the examination of the recently acquired FSB 2011–12 MultiClient GeoStreamer® Survey has facilitated an increased definition of the geological units within and below the volcanic succession, and a reinterpretation of the Late Paleocene–Early Eocene stratigraphy. Through integration of 3D seismic data and well analysis, we present a regional overview of the volcanics and intra-basaltic sediments in the Rosebank region of the Faroe–Shetland Basin. We find that the structural setting of the Rosebank Field, in addition to lava-flow morphology, strongly influences the distribution of the intra-basaltic play fairway within the Paleocene–Eocene-aged Flett Formation. Restriction of fluvial siliciclastic sediments adjacent to the Corona Ridge extends the theorized Rosebank play fairway to the area SW of the Rosebank Field. Our analysis indicates that understanding the underlying basin structure is integral to the success of intra-basaltic plays.〈/span〉

Description: The Lagavulin exploration well 217/15-1Z penetrated a c . 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene–Eocene boundary in the NE Faroe–Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene–Eocene boundary. Basalts from the lower c . 1.3 km have low TiO 2 (〈1.5 wt%) and low Zr/Y (2–3), with olivine-phyric picrites towards the base (Mg# 70–82; olivine Fo 85–91 ). The hiatus correlates precisely with a change to high-TiO 2 (2.5–3.2 wt%), high-Zr/Y (〉4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area. Supplementary material: All raw geochemical data and supplementary analyses are available at http://www.geolsoc.org.uk/SUP18888 .

Description: Tuffs form key stratigraphic markers that assist with determining the timing of volcanic margin development. A number of laterally extensive tuffs are preserved along the North Atlantic Margin in the offshore Faroe–Shetland Basin (FSB), a product of early Palaeogene volcanism associated with the break-up and seafloor spreading between Greenland and NW Europe. These tuffs, which are dominantly basaltic in composition, are widely preserved in the contiguous North Sea Basin. However, less attention has been paid to them in the FSB. This study integrates multiple regional datasets, including 3D seismic data and released commercial well logs, to detail the character and distribution of early Palaeogene tuffs in the FSB. The earliest tuffs are more locally identified by their presence in core, whereas later tuffs are more regionally recognizable, highlighting more widespread volcanism with time. The distribution of tuffs also reveals the timing of formation of the previously enigmatic volcanic centres. Importantly, owing to constraints of vertical resolution in well data, we argue that the number of tuffs in the North Atlantic Margin is probably underestimated, and biased towards basaltic tuffs, which are easier to identify on well logs.

Description: Accurate palaeoenvironmental analysis is at the heart of producing reliable interpretations and depositional models. This study demonstrates a multivariate statistical approach to facies analysis based on relationships between grain size and quantitative palynology. Our methodology has the advantage that it can be used on small amounts of sample, such as core or well cuttings, as the basis for facies analysis. Proof of concept studies involving the collection of grain-size and palynological datasets from well-exposed outcrops of the Middle Jurassic, Lajas Formation of the Neuquén Basin, Argentina, demonstrate that canonical correspondence analysis can be used to consistently recognize facies and aid in the determination of depositional environments. This study demonstrates the link between depositional facies, grain-size distribution, palynomorph hydrodynamics and assemblage taphonomy of palynomorphs. This knowledge can be transferred into a semi-automated statistical facies prediction technique for the subsurface in complex depositional settings, particularly when calibrated against conventional sedimentary facies analysis. Supplementary material: The full set of grain-size data and statistical scores are available at: https://doi.org/10.6084/m9.figshare.c.3745481.v1

Description: Seismic reflection data allow for the 3D imaging of monogenetic edifices and their corresponding plumbing systems. This is a powerful tool in understanding how monogenetic volcanoes are fed and how pre-existing crustal structures can act as the primary influence on their spatial and temporal distribution. This study examines the structure and lithology of host-rock as an influence on edifice alignment and provides insight into the structure of shallow, sub-volcanic monogenetic plumbing systems. The anticlinal Ben Nevis Structure, located in the northerly extent of the Faroe–Shetland Basin, NE Atlantic Margin, was uplifted during the Late Cretaceous and Early Paleocene by the emplacement of a laccolith and a series of branching sills fed by a central conduit. Seismic data reveal that multiple intrusions migrated up the flanks of the Ben Nevis Structure after its formation, c. 58.4 Ma (Kettla-equivalent), and fed a series of scoria cones and submarine volcanic cones. These monogenetic edifices are distributed around the crest of the Ben Nevis Structure. The edifices are fed from a complex network of sills and transgressive sheets, involving lateral magma migration of tens of kilometres before extrusion at the surface. This work highlights the importance of underlying basin structures in influencing the sites and development of subaerial monogenetic fields, and the importance of lateral magma flow within volcanic systems. Supplementary materials: The results of the statistical alignment analysis of the monogenetic edifices are available at https://doi.org/10.6084/m9.figshare.c.3662809 .