The Neogene stratigraphy of the glaciated European margin from Lofoten to Porcupine
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The Neogene stratigraphy of the glaciated European margin from Lofoten to Porcupine |
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PREFACEThis stratigraphic atlas is one of two major products of the EC-supported STRATAGEM project; STRATAGEM is an acronym for 'Stratigraphic Development of the Glaciated European Margin'. The second main product of the project will be an evolutionary model for the area covered by the study, which will build upon the regional stratigraphic framework. This volume presents a unified stratigraphic scheme for the Neogene (Miocene–Holocene) succession preserved along the Atlantic margin of NW Europe. The format and layout of this volume closely follows the style of presentation adopted for similar atlases published by the British Geological Survey (BGS), e.g. Stoker (1999), off NW Britain. This study combines lithostratigraphic and biostratigraphic data with a seismic-sequence stratigraphic framework derived from the integration of regional grids of high-resolution and commercial seismic-reflection profiles. The overall aim of this work has been to produce a Neogene stratigraphic framework that can be applied both to seismic and borehole/well data, and which will have the widest acceptance within the scientific community and industry. An additional element to this volume is a summary of the high-resolution stratigraphy for the middle Pleistocene–Holocene sediment record. The area covered by this volume is the European Atlantic continental margin that has been influenced by glaciation, extending southwards from the Lofoten Islands off Mid-Norway (about 68ºN) to the Porcupine Seabight (about 50ºN) off SW Ireland. The continental margin is here taken to include the middle to outer shelf and slope of the Vøring, Møre, northern North Sea, Faroe–Shetland, Hebrides, Malin, Irish, Porcupine and Rockall margins and the adjacent deep-water areas of the Norwegian Basin, Faroe-Shetland/Faroe Bank Channel, Rockall Trough and Porcupine Seabight (Fig. 1). The database utilised in the establishment of the Neogene framework consists of tens of thousands of line-kilometres of seismic-reflection data, 20 BGS shallow boreholes, 9 BGS rockdrill cores, 4 Irish shallow boreholes, 2 Deep Sea Drilling Project (DSDP) sites, 4 Ocean Drilling Program (ODP) sites and 37 released commercial wells and geotechnical borings (Fig. 2). Supplementary information was derived from published sources. Additionally, 36 short cores and 3 commercial geotechnical borings were utilised for the high-resolution stratigraphy. The fundamental objectives of this study were to simplify the stratigraphic nomenclature and establish a unified regional stratigraphic classification and framework. To achieve an effective stratigraphic analysis, it was essential to recognise the correct level and method of correlation. Seismic-sequence stratigraphy represents the most practical approach to subdividing and correlating the Neogene succession on a regional basis, as this technique produces the most realistic stratigraphic correlation over large geographic areas, especially in frontier regions such as the NW European Atlantic margin. The seismic-sequence stratigraphic concept used in this volume follows the Geological Society's guide to stratigraphic procedure (Whittaker et al. 1991). The basis of the method is to use an integrated geological/geophysical database to define the sedimentary record in terms of depositional sequences. Emphasis has been placed on the establishment of megasequences, which bring together units that constitute important genetic packages. This level of mapping was deemed most appropriate in the establishment of a regional framework, as the development of megasequences tends to reflect major changes in continental margin evolution. Major phases of change are typically manifest by regional unconformities that form the megasequence boundaries (Hubbard et al. 1985). These boundaries are key elements in offshore sub-surface analysis and provide a first-order control on regional correlation. It should be noted that the Neogene succession has previously been subdivided into a multitude of seismic-stratigraphic units at various locations along the margin (e.g. Stoker et al. 1993; Rokoengen et al. 1995; King et al. 1996; McNeill et al. 1998; Andersen et al. 2000; Evans et al. 2002) which, over time, has resulted in a confusing plethora of stratigraphic terms. This new scheme aims to greatly simplify the stratigraphic nomenclature, yet provide a context for future, more detailed subdivision and meaningful correlation of the succession. In this volume, the Neogene megasequence terminology builds upon a number of recent regional stratigraphic studies that have focused on mid-Norway (McNeill et al. 1998; Evans et al. 2002), the Faroe–Shetland region (Stoker et al. In press), and the Rockall Trough (Stoker et al. 2001). Off mid-Norway, the previously established formation nomenclature, i.e. Naust and Kai formations, has been retained. In contrast, a new terminology is introduced for the Faroe–Shetland (i.e. FSN-1 and FSN-2), and Rockall–Porcupine (i.e. RPa and RPb) regions, which reflects the integration and unification of former localised and separate schemes in these areas. This regional two-fold subdivision of the Neogene is assigned ages of Miocene to lower Pliocene (Kai, FSN-2 and RPb) and lower Pliocene to Holocene (Naust, FSN-1 and RPa). The volume is divided into a number of sections. It begins with an overview of the NW European Atlantic margin, with specific emphasis on the following: 1) the nature of the database; 2) the tectonic, physiographic and oceanographic setting; 3) the main controls on Neogene sedimentation; and, 4) an introduction to the stratigraphic scheme. This is followed by a summary of the unified stratigraphic scheme. This highlights the key boreholes and wells used to calibrate the primary seismic reflections that represent the regional unconformities, and hence delineate the megasequence boundaries. A number of seismic/geoseismic panels further exemplify the megasequences and their bounding surfaces. A summary of all of the lithological data used in the establishment of the Neogene stratigraphic framework is presented as a series of stratigraphic-range charts for the Norwegian, Faroe–Shetland and Rockall–Porcupine regions. The potential linkage between significant tectonic, climatic, eustatic and oceanographic events is explored with respect to passive margin development in the NE Atlantic region. The pre-Neogene framework presents a summary of the post-rift structural setting of the continental margin upon which the Neogene evolution can be placed. The following two sections summarise the details of the Miocene–lower Pliocene and lower Pliocene–Holocene megasequences in terms of their distribution, seismic-sequence stratigraphic features, and their lithological and biostratigraphic characteristics. The penultimate section presents some preliminary information on high-resolution stratigraphy along the continental margin. Whilst the record locally extends back to 1.1Ma offshore Norway, the main focus across most of the margin is on the mid-Pleistocene to Holocene, glacial-interglacial regime, essentially the last 0.5Ma. The sediment cores that form the basis of this framework are presented as a series of high-resolution stratigraphic-range charts. The final section presents a number of geoseismic/seismic panels intended to provide the context to the Neogene megasequence framework in the form of regional transects across the margin. Project organisation The partners involved in this international project come from six countries; they represent national geological surveys, research institutes and universities: British
Geological Survey (co-ordinators) In addition, Svitzer Ltd was subcontracted for data management and report production. The European Commission (EC) has supported STRATAGEM through Contract Number EVK3-CT-1999-00011 through its 5th Framework Programme. It is a three-year programme that started on 1st March 2000, and forms part of the cluster of margin-related EC projects known as OMARC (Ocean Margin Deep-Water Research Consortium). As well as support from the EC, STRATAGEM has received additional support from the oil industry through four joint industry projects (JIPs) that together represent a considerable number of oil companies active in the region. The JIPs, who have contributed either financially and/or through the contribution of data and interpreted datasets, are listed in the acknowledgements: STRATAGEM has been organised such that the study area has been subdivided into three 'Work Package' (WP) areas (Fig. 1): North Sea
Fan–Vøring region WP1 Individual stratigraphic reports have been produced for each of these areas, and this volume has been compiled based on the input from them. The STRATAGEM partners involved in the WP1–3 tasks and WP4 compilation process have been: British Geological Survey (BGS) Dan Evans
(STRATAGEM co-ordinator)
Tove Nielsen
(WP2 co-ordinator and geologist) Royal Netherlands Institute for Sea Research (Royal NIOZ) Tjeerd van
Weering (WP3 co-ordinator, geologist WP 3) Istituto Nazionale di Oceanographia e di Geofisica Sperimentale (OGS) Laura De
Santis (geologist, basin modeller WP1–3) University College Dublin (UCD) Pat
Shannon (geologist WP3) University of Bergen (UiB) Hans
Petter Sejrup (WP1 co-ordinator, geologist) University of Tromsø (UiT) Tore
O. Vorren (principal geologist WP1) Svitzer Ltd (subcontractors to BGS) Zara
Harrison (database co-ordinator) Acknowledgements The STRATAGEM partners would like to gratefully acknowledge the help of many organisations in the production of this report. These are as follows: The EC has funded STRATAGEM through its 5th Framework Programme, and we would particularly like to thank Gilles Ollier, the project officer, for his support and enthusiasm. STRATAGEM has received support through four joint industry projects (JIPs) that together represent a number of oil companies active in the region. The JIPs have contributed either financially and/or through the contribution of data and interpreted datasets, or in both ways. They are: The Seabed Project (Norway) — SP The individual companies represented by these JIPs, with their JIP membership shown in brackets (and many companies are members of more than one JIP), are as follows:
Other companies who have separately contributed data to the STRATAGEM project are:
Additionally we would like to acknowledge both the NW European JIP co-operation committee and other individuals from participating oil companies who have helped make the project possible and given their support both during the preparation and the active phase of the project:
Svitzer Ltd, who were subcontracted for data management and report production in STRATAGEM, are thanked for their work in the production of this report, in particular Zara Harrison, Susan Buchan, Neil White and Richard Salisbury. References Andersen, M.S., Nielsen, T., Sørensen, A.B., Boldreel, L.O. & Kuijpers, A. 2000. Cenozoic sediment distribution and tectonic movements in the Faroe region. Global and Planetary Change, 24, 239-259. Evans, D., McGiveron, S., Harrison, Z., Bryn, P. & Berg, K. 2002. Along-slope variation in the late Neogene evolution of the mid-Norwegian margin in response to uplift and tectonism. In: Doré, A.G., Cartwright, J., Stoker, M.S., Turner, J. & White. N. (eds). Cenozoic Exhumation of Atlantic Margins. Geological Society, London, Special Publications, in press. Hubbard, R.J., Pape, J. & Roberts, D.G. 1985. Depositional sequence mapping as a technique to establish tectonic and stratigraphic framework and evaluate hydrocarbon potential on a passive continental margin. In: Berg, O.R. & Woolverton, D. (eds), Seismic Stratigraphy II. American Association of Petroleum Geologists Memoir 39, 79-91. King, E.L., Sejrup, H.P., Haflidason, H., Elverhøi, A. & Aarseth, I. 1996. Quaternary seismic stratigraphy of the North Sea Fan: Glacially-fed gravity flow aprons, hemipelagic sediments and large submarine slides. Marine Geology, 130, 293-316. McNeill, A.E., Salisbury, R.S.K., Østmo, S.R., Lien, R. & Evans, D. 1998. A regional shallow stratigraphic framework off mid-Norway and observations of deep water 'special features'. 1998 Offshore Technology Conference, Houston, Tx, 1-13. Rokoengen, K., Rise, L., Bryn, P., Frengstad, B., Gustavsen, B., Nygaard, E. & Sætem, J. 1995. Upper Cenozoic stratigraphy of the Mid-Norwegian continental shelf. Norsk Geologisk Tidsskrift, 75, 88-104. Stoker, M.S. 1999. Stratigraphic nomenclature of the UK North West Margin. 3. Mid- to late Cenozoic stratigraphy. British Geological Survey, Edinburgh. Stoker, M.S., Hitchen, K. & Graham, C.C. 1993. United Kingdom offshore regional report: the geology of the Hebrides and West Shetland shelves and adjacent deep-water areas. (London: HMSO for the British Geological Survey). Stoker, M.S., van Weering, T.C.E. & Svaerdborg, T. 2001. A Mid- to Late Cenozoic tectonostratigraphic framework for the Rockall Trough. In: Shannon, P.M., Haughton, P.D.W. & Corcoran, D. (eds), The Petroleum Exploration of Ireland's Offshore Basins. Geological Society, London, Special Publications, 188, 411-438. Stoker, M.S., Nielsen, T., van Weering, T.C.E. & Kuijpers, A. 2002. Towards an understanding of the Neogene tectonostratigraphic framework of the NE Atlantic margin between Ireland and the Faroe Islands. Marine Geology, in press.
Whittaker, A., Cope, J.C.W., Cowie, J.W., Gibbons, W., Hailwood, E.A., House, M.R., Jenkins, D.G., Rawson, P.F., Rushton, A.W.W., Smith, D.G., Thomas, A.T. & Wimbledon, W.A. 1991. A guide to stratigraphical procedure.
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This page was Last updated 12 September 2002
