Rockall Continental Margin Report. Final geological report (5 volumes)

The Rockall Continental Margin Project was a 3-year research programme, undertaken between April 1992 and March 1995, designed to investigate the geology and resource potential of part of the frontier area west of Scotland. The programme was funded by a consortium comprising the British Geological Survey (BGS) and 8 exploration companies - BP, British Gas, Conoco, EE Caledonia, Elf, Enterprise, Esso and Mobil. The study has focused on the central and northern Rockall Trough, although several long transect lines were run across the Rockall Plateau and into the Iceland Basin to provide a margin-wide assessment of the geological framework. Over the duration of the project, multichannel seismic, gravity, magnetic and bathymetry data, together with boreholes and shallow-sample information were acquired by the consortium. These data form the basis of this 5-volume report. A descriptiono f the geology and prospectivityo f the surveyed area comprises volume 1, whilst the data on which the geological interpretation is based, including biostratigraphy, petrology and geochemistry of the boreholes and shallow samples, are presented in volumes 2 to 5. The widespread distribution of Upper Cretaceous to lower Palaeogene volcanic rocks continues to hinder our understandionfg t he geological frameworkof the Rockall Continental Margin. Whilst it has been proved that Lower Proterozoic gneisses form continental basement on Rockall Bank, and are therefore part of the Islay structural terrane, the pre-Cretaceous supracrustal infill of the Rockall Trough and Hatton-Rockall Basin remains conjectural. Reworked palynomorphs of Carboniferous, Jurassic and Early Cretaceous age have been identified in lower Palaeogene sediments recovered on the western margin of the Rockall Trough, but their provenance is uncertain. The present morphological expressiono f the Rockall Continental Margin largely reflects late Mesozoic-Cenozoic extensional tectonism associated with North Atlantic sea-floor spreading. In mid-Cretaceous time, the Rockall Trough was the focus of extreme crustal attenuation associated with abortive continental breakup along the axis of the basin. The growth of the axid Rosemary Bank and Anton D o h s eamounts may have been initiated duringth is phase of crustal thinning. When the axis of spreading shifted westwards, the margin was affected by extensive volcanism concomitant with the split between Rockall Plateau and Greenland, that formed the North-East Atlantic OceaInn. the study area, this volcanismis manifested by the areally extensive, Paleocene to lower Eocene lavas and sills. The continental margin subsequently underwent regional differential subsidence punctuated by intermittent tectonism. This is reflected in the post-volcanic, sedimentary succession for which, for the first time, a unified seismic stratigraphy linking the Rockall Trough and Hatton-Rockall Basin has been established. Three main post-volcanic seismic-stratigraphical sequences have been defined; upper Paleocene to lower upper Eocene, upper Eocene to middle Miocene, and middle Miocene to Holocene. Stratigraphical control and inter-basin correlation are based on a databaseo f BGS boreholes and shallow samples, DSDP boreholes and well 164/25-2 (courtesy of BP). Late Paleocene to early late Eocene sedimentation occurred amidst continuing tectonic instability across the margin. This has been well demonstrated on the edge of Rockall Bank where a prograding shelf-margin sequence penetratebdy borehole 94/3 preserves a record of fluctuating alluvial to shallow-marine sedimentation, interrupted by phases of uplift, erosion and sporadic volcanism. Late Eocene subsidence in the Rockall Trough and Hatton-Rockall Basin provided the downwarped, basin-margin unconformity onto which upper Eocene to middle Miocene sediments onlap. This is a major sequence boundary and essentially marks the onset of deep-water, current-controlled sedimentation in both basins. In the Rockall Trough, the main buildup of the Feni Ridge sediment drift occurred during this interval. A phase of mid-Miocene tectonism resulted in the initiationo f the Barra Fan, on the eastern margin of the Rockall Trough, and may also have instigated a change in regional palaeoceanography culminating in the developmenotf a widespread unconformity across the Rockall Trough and Hatton-Rockall Basin. On the Hebrides Slope, middle Miocene to Holocene sediments form a thick, prograding, clastic weAd gthei.n ner package of deep-water sediments is preserved in the Rockall Trough and, on the western margin of the trough, an erosional regime has prevailed throughout this interval. This has resulted in a marked asymmetry to the depositional sequence architecture across the Rockall Trough. The Hatton- Rockall Basin was similarly dominated by deep-water processes but, in contrast to the Rockall Trough, a much thicker sedimentary succession has accumulated in this basin. In terms of prospectivity, circumstantial evidence suggests that Carboniferous, Mesozoic or lower Tertiary source rocks may be present in the Rockall Trough, but no definite thermogenic source has been proved. Potential hydrocarbon indicators include gas blanking, fluid-migration structures and locally high methane concentrations in surface sediments. The identification of tilted fault blocks on the western margoifn the Rockall Trough, in bothU K and Irish waters, illustrates one possible hydrocarbon-trapping mechanism that may be applicable to this area. Other potential trapping styles include fault-scarp fans and lowstand slope-apron or basin-floor fans

Cretaceous tectonostratigraphy of the Faroe-Shetland region

This report presents a set of observations from the rock record and seismic data that detail aspects of the Cretaceous succession in the Faroe–Shetland region, and which have provided the basis for a regional tectonostratigraphic framework. Timeslice reconstructions showing basin history and lithofacies, combined with seismic stratigraphic information that includes the record of contemporary tectonic events, provide chronological indicators of change in the Faroe– Shetland region. These changes are considered in relation to both local and regional tectonic events; the latter includes key events related to the developing North Atlantic spreading centre, in an attempt to better understand the driving mechanisms and controls on the development of the proto-NE Atlantic margin. The first part of the report (Chapter 1) introduces the project and the context of the study. In particular, the common assumption that, along the NW European margin, Late Jurassic rifting extended into the Early Cretaceous as a single event; a premise that commonly overlooks one of the most fundamental events in the evolution of the NE Atlantic margin – the rotation of the principal extension vector from E–W to NW–SE. Another common misconception is that the Late Cretaceous interval represents a phase of thermal sag and general tectonic quiescence in the Faroe–Shetland region. Such assumptions have generally been the result of speculative application of the North Sea Cretaceous setting to the Atlantic margin; this study aims to rigorously test these assumptions by providing a clear set of regional observational data that provide a direct record of events for the Cretaceous succession in the Faroe–Shetland region. Due to the availability of data, our focus is on the eastern half of the Faroe–Shetland region. This is followed in Chapter 2 by a summary of the regional geological framework, both of the proto-NE Atlantic margin and the Faroe–Shetland region. The latter incorporates published information combined with observations from this study, with a particular focus on the regional seismic-stratigraphic expression of the Cretaceous succession. By choosing a set of seismic profiles across the eastern part of the Faroe–Shetland region, a seismic-stratigraphic scheme has been established, which probably represents the first regional integration of seismic data. This scheme is calibrated with the well database and, thus, provides important chronological information for several regional unconformities. Chapter 3 presents a summary of the Cretaceous tectonostratigraphy of the Faroe–Shetland region, based on a set of timeslice reconstructions that address: 1) basin history; 2) lithofacies; and, 3) lithostratigraphy. These timeslice maps are intended to provide a series of base layers for anyone wishing to undertake future palaeogeographic and/or palinspastic reconstructions. The timeslice reconstructions are underpinned by the set of stratigraphical-range charts and the regional correlation chart presented in Appendices 1 and 2, respectively. The stratigraphicalrange charts detail the chronological range, lithology and lithostratigraphy of the Cretaceous record for each commercial well and BGS borehole, whereas the correlation chart summarises this record on the scale of the individual basin, sub-basin or high. The timeslice reconstructions reveal a highly variable history of differential uplift and subsidence throughout the Cretaceous period, which has important consequences for the tectonic development of this region. Key conclusions include: 1) confirmation that the Early Cretaceous rifting phase is distinct and separate from Late Jurassic rifting; 2) Cretaceous basin development was highly variable and occurred against a backdrop of polyphase extension, uplift and compression, as well as a rising eustatic sea level; and, 3) the Upper Cretaceous succession does not show a simple pattern of ‘post-rift’ subsidence – indeed it is difficult to define a classic post-rift phase to this framework. In Chapter 4, we discuss the implications of our study with regard to the tectonic development of the proto-NE Atlantic margin, by correlation of key local tectonic phases with established regional tectonic events in Europe and the North Atlantic region. The pattern of co-eval extension and compression that is observed is consistent with regional strike-slip associated with transtension and transpression; thus, given the location of the Faroe–Shetland region relative to the developing North Atlantic spreading centre (e.g. Figure 2.1), as well as the Alpine collisional zone, it is not surprising that this area developed as a zone of oblique strike-slip motion. Chapter 5 presents a set of conclusions that summarise the key points of the study. There is no doubt that the highly variable pattern of sedimentation and protracted tectonic history were both influenced by the development of the proto-NE Atlantic margin

Controls on the location of compressional deformation on the NW European margin

The distribution of Cenozoic compressional structures along the NW European margin has been compared with maps of the thickness of the crystalline crust derived from a compilation of seismic refraction interpretations and gravity modelling, and with the distribution of high-velocity lower crust and/or partially serpentinized upper mantle detected by seismic experiments. Only a subset of the mapped compressional structures coincide with areas susceptible to lithospheric weakening as a result of crustal hyperextension and partial serpentinization of the upper mantle. Notably, partially serpentinized upper mantle is well documented beneath the central part of the southern Rockall Basin, but compressional features are sparse in that area. Where compressional structures have formed but the upper mantle is not serpentinized, simple rheological modelling suggests an alternative weakening mechanism involving ductile lower crust and lithospheric decoupling. The presence of pre-existing weak zones (associated with the properties of the gouge and overpressure in fault zones) and local stress magnitude and orientation are important contributing factors

An overview of the Upper Paleozoic-Mesozoic stratigraphy of the NE Atlantic region

This study describes the distribution and stratigraphic range of the Upper Paleozoic–Mesozoic succession in the NE Atlantic region, and is correlated between conjugate-margins and along the axis of the NE Atlantic rift system. The stratigraphic framework has yielded important new constraints on the timing and nature of sedimentary basin development in the NE Atlantic, with implications for rifting and the breakup of the Pangaean supercontinent. From a regional perspective, the Permian–Triassic succession records a northward transition from an arid interior to a passively-subsiding, mixed carbonate/siliciclastic shelf margin. A Late Permian–earliest Triassic rift pulse has regional expression in the stratigraphic record. A fragmentary paralic to shallow-marine Lower Jurassic succession reflects Early Jurassic thermal subsidence and mild extensional tectonism; this was interrupted by widespread Mid-Jurassic uplift and erosion, and followed by an intense phase of Late Jurassic rifting in some (but not all) parts of the NE Atlantic region. The Cretaceous succession is dominated by thick basinal-marine deposits, which accumulated within and along a broad zone of extension and subsidence between Rockall and NE Greenland. There is no evidence for a substantive and continuous rift system along the proto-NE Atlantic until the Late Cretaceous

Cenozoic pre- and post-breakup compression in the Faroe-Shetland area, within the context of the NE Atlantic

This report is primarily based upon the interpretation of oil industry 2D seismic data, and aims to elucidate aspects of Cenozoic tectonostratigraphic development in the Faroe–Shetland region, especially with regard to post-breakup compression. Evidence of Cenozoic and Late Cretaceous pre-breakup compression and deformation is briefly reviewed. We have utilised established seismo-stratigraphic frameworks and a recently updated scheme for the post-breakup Eocene (Stronsay Group) succession, which are largely based upon the recognition of units bounded by regional unconformities. The seismic expression, extent and thickness of the seismo-stratigraphic units are illustrated by geoseismic profiles, structure contour maps and isochore maps, which are used to analyse the spatial and temporal development of post-breakup compression and deformation within the Faroe-Shetland region. The Faroe-Shetland region records a complex spatial and temporal pattern of departures from the thermal subsidence normally associated with passive margins, including broad uplifts and accelerated basinal subsidence together with fold development up to kilometre scale. The phases of latest Eocene / earliest Oligocene ‘sagging’ (accelerated subsidence) and early Pliocene uplift and exhumation (tilting) appear to be coeval with compression. Indeed, compression appears to have been active throughout post-breakup times, although the loci of deformation have varied both spatially and temporally. Conceivably, some of the large scale sagging, tilting and uplift may be associated with lithospheric folding. Much of the intra-Eocene folding appears to be focused in the southwestern part of the Faroe-Shetland region, around the Munkagrunnur Ridge and Judd area, where phases of shelf progradation are preserved and may be associated with contemporaneous uplift. However, there also appears to be evidence of episodic intra-Eocene and younger uplift in the area around the northern Fugloy Ridge. The overall shaping of the Faroe-Shetland Channel appears to have been initiated at the end of the Eocene, associated with uplift on the Fugloy Ridge and Faroe Platform areas, and with accelerated subsidence in the Faroe-Shetland Basin; this shaping was further developed during the Neogene. A Neogene opening of the ‘Faroe Conduit’ oceanic gateway is favoured on the basis of regional evidence of faunal isolation and restricted environment of deposition together with uncertainty regarding the nature of the ‘Southeast Faroes drift’. A significant phase of Miocene folding is associated with the Intra-Miocene Unconformity (IMU), whereas the Mid Miocene Unconformity (MMU) represents a relatively minor break with a restricted distribution in the NE Faroe-Shetland region. Seabed relief on some folds and late Neogene seismic onlaps may indicate that fold development persisted into Recent times. Lateral offsets and local basin inversion associated with the folding, suggest a strong structural inheritance from the underlying rift architecture. A broad coincidence between the timing of formation of the unconformities and plate reorganisation events in the adjacent Norway Basin and wider region may suggest that these events made important contributions to the forces shaping the margin. The development of Miocene and younger folds may have been influenced by gravitational potential energy / body forces associated with the density structure of the Iceland Insular Margin and the Southern Scandes, or with modulations to ridge-push resulting from transient changes in ridge elevation associated with plume-related temperature (buoyancy) variations in the underlying asthenosphere. Far field stresses associated with, for example, collision between Eurasia and Iberia may also have exerted significant influence on deformation within the Faroe-Shetland region

Dynamic evolution of the Faroe-Shetland region

This report presents a series of twenty palaeoenvironment maps that span the interval between the Late Jurassic and the Quaternary, and which form the basis of a generalised reconstruction of the late Mesozoic–Cenozoic development of the Faroe–Shetland and adjacent region. The database behind this study is firmly grounded within the portfolio of existing FSC stratigraphic reports (Cretaceous to Eocene), though it also includes new work that has extended the stratigraphic time series back to the Kimmeridgian (Late Jurassic), and forward to the Mid-Pleistocene. A synthesis of the main structural elements – basins, highs, faults, folds – is also included as these features provide a reference framework on the maps, as well being indicators of contemporary deformation spanning the pre-, syn- and post-breakup stages of NE Atlantic development in this region. By considering the palaeoenvironment maps (our observations) we identify the following key stages in the late Mesozoic–Cenozoic ‘dynamic evolution’ of the Faroe–Shetland region: • Intermittent and localised rifting in the Late Jurassic (mid-Kimmeridgian–earliest Berriasian) and Early Cretaceous (late Berriasian–Hauterivian). • Early Cretaceous (Aptian–Albian) instigation of rifting in the Faroe-Shetland Basin with maximum extension and basin widening in the Late Cretaceous (Coniacian–Maastrichtian). Localised uplift, compression and folding in various basins, particularly in Cenomanian–Turonian. • The Paleocene onset of major extrusive volcanism initiated close to Danian/Selandian boundary; growth of major basaltic shield of Selandian–Thanetian age overlying continental crust in the vicinity of the Faroe Platform; plate breakup and associated volcanism in the earliest Eocene north and west of the Faroe Islands. • Eocene (post-breakup) episodic uplift and erosion along the southern and eastern flanks of the Faroe-Shetland Basin; this was followed by a period of major compressive structuration across the entire Faroe–Shetland region spanning the end-Eocene/Oligocene–Mid-Miocene interval; this set the template for the shape of the modern-day continental margin, including the formation of the deep-water Faroe Conduit which facilitated the transfer of intermediate- and deep-water masses across the Greenland-Scotland Ridge. By comparing the timing of these key phases of geological development of the Faroe–Shetland region with European and North Atlantic plate tectonics we identify a first-order correlation between the pattern of deformation that we observe and established changes in intraplate and/or plate boundary stresses. This raises the possibility that additional forces, including those postulated to be related specifically to the internal dynamics of a mantle plume, may not be a prerequisite to the evolution of the Faroe–Shetland region

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

A place-based approach to payments for ecosystem services

Payment for Ecosystem Services (PES) schemes are proliferating but are challenged by insufficient attention to spatial and temporal inter-dependencies, interactions between different ecosystems and their services, and the need for multi-level governance. To address these challenges, this paper develops a place-based approach to the development and implementation of PES schemes that incorporates multi-level governance, bundling or layering of services across multiple scales, and shared values for ecosystem services. The approach is evaluated and illustrated using case study research to develop an explicitly place-based PES scheme, the Peatland Code, owned and managed by the International Union for the Conservation of Nature’s UK Peatland Programme and designed to pay for restoration of peatland habitats. Buyers preferred bundled schemes with premium pricing of a primary service, contrasting with sellers’ preferences for quantifying and marketing services separately in a layered scheme. There was limited awareness among key business sectors of dependencies on ecosystem services, or the risks and opportunities arising from their management. Companies with financial links to peatlands or a strong environmental sustainability focus were interested in the scheme, particularly in relation to climate regulation, water quality, biodiversity and flood risk mitigation benefits. Visitors were most interested in donating to projects that benefited wildlife and were willing to donate around £2 on-site during a visit. Sellers agreed a deliberated fair price per tonne of CO2 equivalent from £11.18 to £15.65 across four sites in Scotland, with this range primarily driven by spatial variation in habitat degradation. In the Peak District, perceived declines in sheep and grouse productivity arising from ditch blocking led to substantially higher prices, but in other regions ditch blocking was viewed more positively. The Peatland Code was developed in close collaboration with stakeholders at catchment, landscape and national scales, enabling multi-level governance of the management and delivery of ecosystem services across these scales. Place-based PES schemes can mitigate negative trade-offs between ecosystem services, more effectively include cultural ecosystem services and engage with and empower diverse stakeholders in scheme design and governance