Abstract Where hydrocarbon exploration targets occur within basins affected by large igneous province (LIP) sequences, an understanding of the volcanic stratigraphy is essential in compiling accurate basin models at all scales. Ditch cutting samples are one of the most commonly available sources of data yielding information in the context of LIP stratigraphy such as phenocryst load, degree of secondary precipitation and lava composition, largely unattainable by remote sensing. Where core data is limited or absent, cuttings provide the only means of accessing such data along with valuable inference of volcanic facies development and down-hole conditions. Interpretations based on cuttings data are widely used in industry and, as such, a repeatable and well-defined methodology for the analysis and designation of volcanic facies from cuttings is an important requirement for regional and individual play modelling. Such an approach has not been common practice to date. We propose a system of basic percentage-based cuttings analysis and ternary classification specifically tailored to LIP sequences, and argue for the benefits of a coherent and transparent basin-wide approach. The classification system is further developed into a log-style output for easy integration and comparison with other down-hole geophysical and biostratigraphic data.

Abstract The Paleocene sedimentary sequences of the Faroe-Shetland Basin, northeast Atlantic, contain abundant palynomorphs (algae, pollen and spores). While one component of the palynoflora, the dinoflagellate cysts, has been used as the basis for biostratigraphical subdivisions of the succession, the terriginous palynoflora is the more abundant. This terriginous component was derived from two primary sources. The first, and most common source has an angiosperm palynoflora dominated by hickory types ( Momipites species), which occur in association with plane-types (various Tricolpites species) and Ginkgo . This palynoflora occurs commonly in most Faroe-Shetland Basin wells throughout the early and mid-Paleocene succession. A second flora, which is restricted to early and mid Paleocene successions in the west of the basin, has an angiosperm component dominated by Cupuliferoipollenites and Cupuliferoidaepollenites species (broadly, ash and chestnut types). This Greenland Flora is confined to four main stratigraphical pulses in the early and mid-Paleocene, occurring more commonly in proximity to major transfer zones, and west of the Corona Ridge. This distribution pattern provides evidence of argillaceous sediment transportation from the west into the Faroe-Shetland Basin via major transfer zones. Comparison to palaeoclimatic interpretations dispute a relationship between climate change and westerly sediment input into the Faroe-Shetland Basin. Instead, a comparison is invited between pulses of igneous activity in the North Atlantic Igneous Province and sediment transfer from the uplifted eastern zone of the proto-North Atlantic rift.

Abstract The papers in this volume represent a step forward in our knowledge of the geological evolution of the North Atlantic from the Cretaceous-Palaeogene boundary through to the early Eocene. With the increase in hydrocarbon exploration activities in the Faroe-Shetland Basin (Fig. 1 ), new interpretations of the regional geology have become increasingly important, and the accuracy of the time frame for this work is vital to our understanding of the sequence of volcanic and sedimentary events. The synthesis of data relating to Palaeogene volcanism and sedimentation along the Norwegian Margin by Eldholm et al. emphasizes the importance of transfer zones, possibly inherited from the Proterozoic basement, in the distribution of sediments and volcanic products during rifting (Fig. 2 ). Furthermore, subsequent uplift and the development of marginal highs are invoked as factors which affected water circulation within the basins, leading to a deterioration in the Eocene climate. This work identifies the relevance of the North Atlantic Igneous Province (NAIP) as an influence on environmental systems on a global scale. Ar-Ar and Pb-U isotopic age data show that the main period of continental flood basalt volcanism in the NAIP extended from c. 60.5 Ma through to c. 54.5 Ma (Table 1 ). Biostratigraphical analysis of these volcanic-sedimentary sections ( Jolley et al. 2002 ) shows that the onset of this interval equates to the Late Paleocene Thermal Maximum (LPTM). New isotopic dating of the oldest part of the volcanic sequence on the Faroe Islands, the Lower Formation, by Waagstein et al. has further confirmed the age

Abstract Development of the rifted continental margins and subsequent seafloor spreading in the North Atlantic was dominated by interaction between the Iceland mantle plume and the continental and oceanic rifts. There is evidence that at the time of breakup a thin sheet of particularly hot asthenospheric mantle propagated beneath the lithosphere across a 2500 km diameter region. This event caused transient uplift, massive volcanism and intrusive magmatism, and a rapid transition from continental stretching to seafloor spreading. Subsequently, the initial plume instability developed to an axisymmetric shape, with the c. 100 km diameter central core of the Iceland plume generating 30–40 km thick crust along the Greenland-Iceland-Faroes Ridge. The surrounding 2000 km diameter region received the lateral outflow from the plume, causing regional elevation and the generation of thicker and shallower than normal oceanic crust. We document both long-term (10–20 Ma) and short-term (3–5 Ma) fluctuations in the temperature and/or flow rate of the mantle plume by their prominent effects on the oceanic crust formed south of Iceland. Lateral ridge jumps in the locus of rifting are frequent above the regions of hottest asthenospheric mantle, occurring in both the early history of seafloor spreading, when the mantle was particularly hot, and throughout the generation of the Greenland-Iceland-Faroes Ridge.

Abstract The development of rifted and sheared segments on the Norwegian continental margin between 62 and 75°N is spatially related to a distinct along-margin segmentation which is governed by transfer zones formed during the Late Jurassic-Early Cretaceous rift episode. In fact, these structures may represent a repeated structural inheritance going back to the Proterozoic. Complete lithospheric breakup near the Paleocene-Eocene transition was preceded by a rift episode which was probably initiated in the early to middle Campanian. It culminated with a massive, regional magmatic event during breakup characterized by eruption of thick lava sequences covering large areas along the continent-ocean transition. The Norwegian volcanic margin belongs to the North Atlantic Large Igneous Province formed by impingement of the Iceland plume on a lithosphere under extension. Offsets in the initial plate boundary, combined with late rift uplift and subsequent construction of emerged marginal highs during breakup, provide key constraints on the Palaeogene water mass circulation, basin evolution and sedimentation during a period of progressive environmental deterioration following early Eocene greenhouse conditions.

Abstract Heavy mineral assemblages in deepwater Paleocene sandstones of the Foinaven Sub-basin (west of Shetland) reflect the influence of three main provenance and dispersal systems. The Schiehallion system has relatively uniform characteristics and persisted through much of the early-mid Paleocene. Its sphere of influence was centred on the Schiehallion Field, but it progressively encroached into the Foinaven area with time. Its main source was the Triassic Foula Formation, with minor supply from Lewisian and Moine basement rocks. The Foinaven system shows marked changes in character, related to evolution of the source area. The earliest sands were derived from a heavily weathered late Cretaceous regolith, and represent the onset of uplift and exhumation of the Shetland Platform. Progressive unroofing led to the incorporation of increasing amounts of Lewisian- and Moine-sourced detritus. Following deposition of the main reservoir sandstones in Foinaven and Schiehallion, there was a progressive change in provenance, with a gradual increase in the amount of sediment shed directly from metamorphic basement. Pulsing of the proto-Icelandic plume has been proposed as the mechanism for repeated influx of sand to the basins around Scotland. However, on the basis of available geochronological data, there does not appear to be a direct link between events in the British Tertiary Igneous Province (BTIP) and changes in provenance in the Foinaven Sub-basin. The initial influx of sediment from a weathered land surface may have been coeval with the onset of magmatism in the BTIP, but the cessation of supply through the Foinaven system at c. 59 Ma does not appear to be related to magmatic events in the BTIP. The waning of magmatism in the BTIP around 58 Ma is broadly coincident with a gradual increase of first-cycle basement detritus.

Abstract The Palaeogene Erlend Volcano subcrops in the Faroe-Shetland Basin on the NE Atlantic Margin and was first recognized on the basis of its pronounced positive gravity and magnetic anomalies. Three hydrocarbon exploration wells (209/3-1; 209/4-1A; 209/9-1) have penetrated thick sequences of subaerial facies basaltic lavas and subaqueous volcanic breccias (the ‘Basaltic Suite’), overlying Palaeogene (Thanetian) and Cretaceous (Maastrichtian and Campanian) sedimentary rocks interbedded with medium to fine-grained silicic igneous rocks (the ‘Acidic Suite’). Detailed palynological and petrological analysis indicates that the basaltic rocks were contemporaneous with the Faroes Lower Lava Formation at c. 56.6-55 Ma, and were erupted into environments ranging between dry land and brackish to freshwater lagoons at the margin of a marine channel separating the Erlend Volcano from the Brendan’s Volcano to the north. The subjacent Acidic Suite is interpreted as a series of sills emplaced approximately contemporaneously with the volcanic rocks on the basis of their diachronous relationship with interbedded sedimentary rocks, together with high Thermal Alteration Index values of in situ fossils.

Abstract Based upon dinoflagellate cyst and nannofossil data, a detailed zonation of the Lower Paleocene succession in the Nuussuaq Basin, onshore West Greenland has been established. The succession is divided into the five dinoflagellate cyst zones: Trithyrodinium evittii, Cerodinium pannuceum, Senegalinium iterlaaense, Palaeocystodinium bulliforme and Alisocysta margarita . The dinoflagellate cyst zones are correlated with nannoplankton zones. The stratigraphically most important nannofossils recorded include Chiasmolithus cf. bidens, Neochiastozygus modestus, N. perfectus, N. saepes, Prinsius martinii and Zeugrhabdotus sigmoides . A new zonal scheme has been erected and resolves previous problems relating biostratigraphic and 40 Ar/ 39 Ar data in the region. The Upper Maastrichtian-Lower Paleocene succession records faulting and valley/submarine canyon incision resulting from pre-volcanic rifting and regional uplift of the basin. Two Early Paleocene tectonic phases have been recognized during NP1–NP3. These uplift phases were followed by rapid subsidence during NP4. Initiation of volcanism onshore West Greenland is broadly concurrent with the Alisocysta margarita Zone indicating that volcanism began during late NP4, in accordance with recent palaeomagnetic results and 40 Ar/ 39 Ar dating of the volcanics. On the basis of the first occurrence datum of the dinoflagellate cyst species Cerodinium kangiliense and Alisocysta margarita , it is possible to correlate the lowermost volcanic Anaanaa Member hyaloclastites from the southwestern part of Nuussuaq with sediments of the Eqalulik Formation from the northern coast of Nuussuaq.

Abstract The initial stages of Palaeogene volcanism in the Nuussuaq Basin in West Greenland were characterized by eruption of basaltic and picritic magmas through sediments of Cretaceous to early Paleocene age into a marine or lowlying coastal environment. Recent magnetostratigraphic work has recognized the C27n-C26r transition (estimated duration less than 10 ka and here assumed to be 5 ka) as a c. 170 m thick zone within a succession of thin picritic lava flows. Multimodel photogrammetry combined with chemical and lithological analysis of the volcanic rocks has allowed detailed 3D analysis of the facies variation within this narrow time window. Subaerial lavas flowed eastwards over a more than 40 km wide front. On northern Disko they covered an existing lava plateau and buried a subaerial landscape of dipping Cretaceous sandstones, while on Nuussuaq they flowed into an up to 700 m deep marine embayment and formed prograding hyaloclastite fans passing into fine-clastic mass flows. With a progradation rate of 0.5–1 m a −1 the palaeogeography of the basin changed considerably during the short time interval. In addition to substantial basin subsidence, the volcanic facies changes have also preserved a record of synvolcanic differential movement of extensional fault blocks. The following parameters are estimated for the volcanism within the Nuussuaq Basin during the C27n-C26r transition: Production rate c. 0.042 km 3 a −1 , productivity c. 1.2 × 10 −3 km 3 a −1 km −1 (rift), volcanic aggradation c. 33 m ka −1 , subsidence c. 25 m ka −1 . If the volcanism evolved continuously at this high aggradation rate, all of the Vaigat Formation could have erupted in 70 ka. However, the complex geological record indicates a much longer total duration, and the volcanism must have had an intermittent character.

Abstract The volcanic succession in the inland Prinsen af Wales Bjerge contains the oldest known onshore lava flows (61 Ma) of the Palaeogene East Greenland flood basalt province. These flows and interbedded sediments define the Urbjerget Formation and are found in the southernmost part of Prinsen af Wales Bjerge. Flows of the Urbjerget Formation are chemically similar to the coastal Vandfaldsdalen Formation flows and the two formations may be chronostratigraphical equivalents. The Urbjerget Formation is overlain by the < 57 Ma tholeiitic basalts of the Milne Land Formation. Four regional volcanic formations are found along the Blosseville Kyst, but the Milne Land Formation is the only one present in the southern Prinsen af Wales Bjerge. Flows of the absent formations (Geikie Plateau, Rømer Fjord and Skrænterne formations) may not have been able to enter the area due to local uplift, more distal located eruption sites or possibly topographic features. A high-Si (SiO 2 > 52 wt%) lave flow succession in the Milne Land Formation consists of crustally contaminated magmas which were arrested in crustal chambers as the magma supply rate from the mantle decreased, either due to a general lowering of potential mantle temperatures or a decrease in the rate of continental rifting. Tholeiitic high-Ti flows (MgO: 10–15 wt%, TiO 2 : 5–6 wt%) within the Milne Land Formation are unique to the Prinsen af Wales Bjerge region, and equivalents have not been reported from other flood basalt provinces. Local flow composition variations in the Milne Land Formation can be explained as the result of melting under lithosphere of variable thickness, small-scale variations in mantle composition and mixing in small magma chambers. Unconformably overlying the Milne Land Formation is a succession of c. 53 Ma alkaline flows, known as the Prinsen af Wales Bjerge Formation. Several crater sites are known from this flow succession and this suggests that the Prinsen af Wales Formation was only covered locally by later volcanic or sedimentary units. The duration of alkaline volcanic activity in the Prinsen af Wales Bjerge is not well constrained but may have been less than 2.5 Ma. The hiatus between the Urbjerget and Milne Land formations is a regional feature in the North Atlantic as it occurs at a similar stratigraphic level at Nansen Fjord, the Faroe Islands and in the ODP Leg 152 volcanic succession off SE Greenland at c. 63°N. It represents a 3–4 Ma long cessation of, or very low frequency of activity in East Greenland/Faroese volcanism and may be explained as the time interval between two pulses in the palaeo-Icelandic plume.

Abstract The Paleocene flood basalts of the Faroe Islands form a central part of the North Atlantic Igneous Province, but have proven difficult to date because of very low-grade burial metamorphism in the chabazite-thomsonite to the laumontite zeolite zone. We present 17 replicated K/Ar and 8 Ar/Ar whole-rock analyses of basalts from the >3 km thick lower basalt formation, the age of which has been debated for years. Samples are from the massive core of thick, exposed flows, and two boreholes (Vestmanna-1 and Lopra-1). Six samples are drill cuttings. Extensive microprobe work and mass balance calculations show that roughly 60% of the potassium of the dated basalts resides in plagioclase, interstitial cryptocrystalline rhyolite and smectitic clay, the rest mainly forming thin rims of alkali feldspar on plagioclase. Six basalts fulfil the following criteria: (1) they are almost homogeneous in K and Ar (ages on different splits vary by <4 Ma); (2) the only low-temperature phase present is smectite (saponite±minor interstratified chlorite-smectite); and (3) max. c. 6% of total K occurs in smectite. This smectite replaced metastable interstitial glass during early burial and has a trivial effect on measured ages. The six basalts give mean K/Ar whole-rock ages of 56.5 ± 1.3 to 58.9 ± 1.3 Ma (1σ), which are interpreted as igneous ages consistent with mapped palaeomagnetic reversals and unpublished Ar/Ar dates. They suggest that the oldest drilled lavas erupted at 58.8 ± 0.5 Ma (1σ) in the later part of magnetochron C26r accumulating at >2 km Ma −1 , and that the volcanism came to a slow end at 56.4 ± 0.5 Ma in the beginning of chron C24r. The Lower Basalt Formation is overlain by 10m of coal-bearing sediments and 2 km syn-breakup lavas, deposited in early C24r (>55 Ma). The remaining 11 basalts are either inhomogeneous, carry > 10% of the total K in clay, have C/S > saponite or contain traces of zeolites, secondary quartz, dioctahedral smectite or celadonite as probable indicators of prolonged alteration, and they give low or variable K/Ar ages. The Ar/Ar analyses include five of these poor samples plus three of the first group. They give a plateau age of 55.7 ± 0.9 Ma (1σ) for two exposed flows assigned to chron C25n, but of 60–63 Ma for six drilled lavas assigned to C26r. We argue that the later Ar/Ar ages are too high due to 39 Ar recoil loss out of the sample (0–25%) or relocation during irradiation and should be ignored.

Abstract Palaeogene volcanism on the NW margin of the Faroe-Shetland Basin is represented by the Faroes Lava Group, within an age range of 57.5–60.56 Ma. The volcanic sequence comprises >1000 m of basaltic volcaniclastic rocks deposited in estuarine or marginal lagoons, overlain by three laterally-extensive formations of subaerial facies basaltic lavas: Lower, c. 3250 m; Middle, c. 1400 m; Upper, at least 900 m (top not preserved). The Lower and Upper formations comprise high-volume sheet flows, commonly with ferrallitized tops, interbedded with reddened, thin, fluvial claystone and basaltic siltstone deposits. Laterally-impersistent coals occur within the Lower Lava Formation. The Coal-bearing Formation ( c. 20 m) was deposited in an overbank floodplain environment during an hiatus in the volcanism between the Lower and Middle formations. The Volcaniclastic Sandstone Sequence comprises hydroclastic and pyroclastic deposits which post-date the Coal-bearing Formation and represent a return to volcanism, prior to the eruption of the Middle Lava Formation which is mainly characterized by inflated pahoehoe flows. The onshore sequence of the Faroes Lava Group can be correlated with basaltic flows within the Faroe-Shetland Basin, where lavas in Well 205/9-1 are interpreted to be of Lower Lava Formation affinity, possibly erupted from a local vent system. Seismic and gravity mapping and modelling suggest that the offshore extension of the Lower Lava Formation, together with the oldest part of the Middle Lava Formation, comprise subaqueous hyaloclastites deposited in a prograding Gilbert-type lava delta system. The youngest part of the Middle Lava Formation and all of the Upper Lava Formation occur as subaerial facies lavas within the basin.

Abstract An extensive suite of igneous sills, collectively known as the Faroe-Shetland Sill Complex, has been intruded into the Cretaceous and Tertiary sedimentary section of the Faroe-Shetland Channel area. These sills have been imaged offshore by three-dimensional (3D) reflection seismic surveys and penetrated by several exploration boreholes. Data from wireline log measurements in these boreholes allow us to characterize the physical properties of the sills and their thermal aureoles. The borehole data has been compiled to produce new empirical relationships between sonic velocity and density, and between compressional and shear sonic velocities within the sills. These relationships are used to assist in calculation of synthetic seismic traces for sills intruded into sedimentary section, in order to calibrate the seismic response of the sills as observed in field data. This paper describes how the seismic amplitude response of the sills can be used to predict sill thickness where there is some nearby well control, and use this technique to estimate the volume of one well-imaged sill penetrated by Well 205/10-2b. Since the sills have a high impedance contrast with their host rocks, they return strong seismic reflections. 3D seismic survey data allow mapping of the morphology of the sills with a high level of confidence, although in some instances disruption of the downgoing seismic wavefield causes the seismic imaging of deeper sills and other structures to be very poor. Examples of sub-circular and dish-shapes sills, and also semi-conical and sheet-like intrusions, which are highly discordant are shown. The introduction of intrusive rocks can play an important role in the subsequent development of the sedimentary system. An example is shown in which differential compaction or soft sediment deformation around and above the sills appears to have controlled deposition of a reservoir quality sand body. The positioning of the sills within sedimentary basins is discussed, by constructing a simple model in which pressure support of magma from a crustal magma chamber provides the hydrostatic head of magma required for intrusion at shallow levels. This model is made semi-quantitative using a simple equation relating rock densities to intrusion depth, calibrated to observations from the Faroe-Shetland area. The model predicts that sills can be intruded at shallower levels in the sedimentary section above basement highs, which agrees with observations detailed in this paper.

Abstract The North Faroe-Shetland Basin (NFSB) Sill Complex is of late Paleocene/earliest Eocene age and was emplaced within Cretaceous and Paleocene sedimentary rocks, in places to depths as shallow as a few hundred metres below the contemporaneous basin floor. Intersections of the Complex occur in exploration wells drilled by the oil industry and indicate tholeiitic basaltic compositions. High quality 3D seismic data, obtained during hydrocarbon exploration along the NE Atlantic Margin, provide a unique view of an uneroded suite of these sheet-like intrusions in UK Quadrants 218 and 219 and indicate the multi-centred nature of the NFSB Sill Complex, with upward-fingering terminations from broad bowlshaped foci of intrusion. Where the intrusion depth is very shallow, depending upon the host lithology, sill emplacement has lead to the development of structures on the contemporaneous basin floor interpreted as submarine hyaloclastite-dominated vents, up to c. 2 km across and with heights of up to c. 100 m. Where intrusion depth is greater, ‘seismic chimney’ structures are interpreted as the fluidescape feeders of sedimentary-hydrothermal mounds. Subsequent differential compaction of sedimentary sections, with and without shallow-emplaced sills, has given rise to distinctive ‘eye’ structures, as seen in seismic sections.