The Neogene stratigraphy of the glaciated European margin from Lofoten to Porcupine

Preface ] Introduction ] Unified Stratigraphy ] Pre-Neogene Framework ] Miocene to Lower Pliocene ] Lower Pliocene To Holocene ] High-Resolution Stratigraphy ] Key Geoseismic Sections ]

Key Boreholes ] Figure 7 ] WP1 ] Figure 8 ] WP2 ] Figure 9 ] WP3 ] Figure 10 ] WP1 - Stratigraphic Range ] Figure 11 ] WP2 - Stratigraphic Range ] Figure 12 ] WP3 - Stratigraphic Range ] Figure 13 ] [ Event Stratigraphy ] Figure 14 ]

EVENT STRATIGRAPHY

Any attempt to understand the Neogene stratigraphic development of the Atlantic margin of NW Europe has to consider the regional tectonic setting. Megasequence development and regional unconformities (megasequence boundaries) tend to reflect major phases of continental margin evolution, commonly in response to tectonic events that modified sedimentation patterns, palaeoceanographic circulation and may even have influenced climatic change. On the scale of a continental margin, plate-tectonic processes probably drive such changes. Since the onset of sea-floor spreading in the NE Atlantic Ocean, the NW European margin has occupied a buffer zone between the spreading ridge to the west, and the Africa–Europe convergence zone to the SE (Knott et al. 1993). Consequently, the margin has largely been subjected to a compressive stress regime (Cloetingh et al. 1987), thus making it susceptible to any changes in the intra-plate stress field. Late Alpine orogenic activity and plume-enhanced ridge push are two possible mechanisms that may affect the intra-plate stress field, the response to which may include differential uplift and subsidence, and changes in the water-circulation pattern (Cloetingh et al. 1990). 

A preliminary chart has been compiled (Fig. 14) that shows a number of Neogene tectonic and other events, together with some of the key aspects of the NW European Atlantic margin succession. The compilation of the chart is based on several synthesis papers (Doré et al. 1999; McDonnell & Shannon 2001; Stoker et al. 2001; Lundin & Doré 2002) and the references therein. The sea-level curves and indication of global ice extent is from Abreu & Anderson (1998), and the timescale is from Berggren et al. (1995). The purpose of Fig. 14 is to try and identify any potential linkages between the development of the megasequence boundaries and possible forcing mechanisms: tectonic, oceanographic, or climatic. Whilst a detailed appraisal of the event stratigraphy is beyond the scope of this atlas, a brief summary is presented below of some of the observations that must be incorporated into any general model of Neogene evolution of the NW European Atlantic margin.

Early Neogene events

The punctuated record of Miocene sedimentation (Fig. 11, Fig. 12 and Fig. 13) reflects not only later Neogene erosion, but is probably also in response to inversion. Uplift and doming occur throughout a large part of the area, and thus reflect a regional phenomenon. However, the timing of doming may be locally variable, which results in a varied record of sedimentation between areas. This makes regional correlation problematic. According to Lundin & Doré (2002) the domes may have been formed in discrete phases of intra-plate compression linked to periods of high plume flux. However, inspection of Fig. 14 also shows other tectonic events, such as the Late Alpine orogeny, the separation of Jan Mayen and Greenland, and the rearrangement of the spreading axis about the Faroe-Iceland–Greenland Ridge. The regional influence of these events remains unclear. 

One very significant event that does have a bearing on the NW European Atlantic margin is the submergence of the Greenland-Scotland Ridge (GSR), which includes the Wyville-Thomson Ridge at its SE end, and the initiation of deep-water exchange between the Arctic and North Atlantic oceans. Whilst the timing of the onset of North Atlantic Deep Water (NSDW) formation remains ambiguous — early Oligocene (Davies et al. 2001) or Neogene (Eldholm 1990) — our study clearly indicates that major sediment-drift accumulation largely dates from the mid-Miocene, coincident with the submergence of the GSR. Whether or not this marks the onset of NSDW overflow, it certainly marks the establishment of a stable oceanographic regime. Moreover, it may be no coincidence that there was a progressive cooling of Northern Hemisphere climate from this time. 


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Late Neogene events

The formation of the early Pliocene unconformity, as represented throughout this study by the BNU, INU and C10 boundaries, links the instigation of shelf-margin progradation along the entire NW European Atlantic margin. Additionally, a vigorous pulse of widespread deep-water erosion in the Faroe-Shetland Channel, Rockall Trough and Porcupine Seabight is a less well documented (Stoker 2002; Stoker et al. 2002) but equally significant expression of change at this time. The deep-water basins would have been especially sensitive to changes in oceanographic circulation. Such a regionally synchronous event suggests that the mechanics behind this phenomenon must be of a plate-tectonic nature. Epeirogenic uplift has been cited by several authors (Doré et al. 1999; Japsen & Chalmers 2000; Lundin & Doré 2002) as a major factor influencing the Plio-Pleistocene development of the continental margin, although the uplift mechanism remains unknown. Regardless of uplift mechanism, the uplifted areas were a topographic prerequisite for the nucleation and growth of ice sheets as the climate deteriorated (Eyles 1996). Although there is a degree of diachroneity in the development of widespread shelf glaciation within the study area, as might be expected over such a latitudinal range, glacial sediments form a major component of all of the prograding wedges. 

On a larger scale, it is interesting to note that the closure of the Isthmus of Panama also occurred in the early Pliocene. The significance of this event is that the equatorial currents from the Atlantic Ocean could no longer enter the Pacific Ocean. Essentially, the oceanographic circulation pattern in the North Atlantic changed from a circumequatorial to an interpolar circulation. Thus an increased volume of tropical water was deflected northwards, which arguably triggered an intensification of glaciation in the Northern Hemisphere. Exploring all of these potential linkages is a challenge for the future.

References

Abreu, V.S. & Anderson, J.B. 1998. Glacial eustasy during the Cenozoic: sequence stratigraphic implications. American Association of Petroleum Geologists Bulletin, 82, 1385-1400.

Berggren, W.A., Kent, D.V., Swisher, III, C.C. & Aubry, M-P. 1995. A revised Cenozoic geochronology and chronostratigraphy. In: Berggren, W.A., Kent, D.V., Aubry, M-P. & Hardenbol, J. (eds), Geochronology, Time Scales And Stratigraphic Correlation: Framework For An Historical Geology. Society for Economic Palaeontologists and Mineralogists Special Publication 54, 129-212.

Cloetingh, S., Lambeck, K. & McQueen, H. 1987. Apparent sea-level fluctuations and a palaeostress field for the North Sea region. In: Brooks, J. & Glennie, K. (eds), Petroleum Geology of North West Europe, (London: Graham & Trotman), 49-57.

Cloetingh, S., Gradstein, F.M., Kooi, H., Grant, A.C. & Kaminski, M. 1990. Plate reorganisation: a cause of rapid late Neogene subsidence and sedimentation around the North Atlantic? Journal of the Geological Society, London, 147, 495-506.

Davies, R., Cartwright, J., Pike, J. & Line, C. 2001. Early Oligocene initiation of North Atlantic Deep Water formation. Nature, 410, 917-920.

Doré, A.G.D., Lundin, E.R., Jensen, L.N., Birkeland, Ř., Eliassen, P.E. & Fichler, C. 1999. Principal tectonic events in the evolution of the northwest European Atlantic margin. In: Fleet, A.J. & Boldy, S.A.R. (eds), Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference. Geological Society, London, 41-61.

Eldholm, O. 1990. Paleogene North Atlantic Magmatic-Tectonic Events: Environmental Implications. Memorie della Societa Geological Italiana, 44, 13-28.

Eyles, N. 1996. Passive margin uplift around the North Atlantic region and its role in Northern Hemisphere late Cenozoic glaciation. Geology, 24, 103-106.

Japsen, P. & Chalmers, J.A. 2000. Neogene uplift and tectonics around the North Atlantic: overview. Global and Planetary Change, 24, 165-173.
Knott, S.D., Burchell, M.T., Jolley, E.W. & Fraser, A.J. 1993. Mesozoic to Cenozoic plate reconstructions of the North Atlantic and hydrocarbon plays of the Atlantic margins. In: Parker, J.R. (ed), Petroleum Geology of Northwest Europe: Proceedings of the 4th conference. Geological Society, London, 953-974.

Lundin, E. & Doré, A.G. 2002. Mid-Cenozoic post-breakup deformation in the 'passive' margins bordering the Norwegian-Greenland Sea. Marine and Petroleum Geology, 19, 79-93.

McDonnell, A. & Shannon, P.M. 2001. Comparative Tertiary stratigraphic evolution of the Porcupine and Rockall basins. In: Shannon, P.M., Haughton, P.D.W. & Corcoran, D.V. (eds), The Petroleum Exploration of Ireland's Offshore Basins. Geological Society, London, Special Publications, 188, 323-344.

Stoker, M.S. 2002. Late Neogene development of the UK Atlantic margin. Doré, A.G.D., Cartwright, J., Stoker, M.S., Turner, J.P. & White, N. (eds) In press. Exhumation of the North Atlantic Margin: Timing, Mechanisms and Implications for Petroleum Exploration. Geological Society, London, Special Publications, 196, in press.

Stoker, M.S., Van Weering, T.C.E. & Svaerdborg, T. 2001. A Mid- to Late Cenozoic tectonostratigraphic framewrok for the Rockall Trough. In: Shannon, P.M., Haughton, P.D.W. & Corcoran, D.V. (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.


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Key Boreholes ] Figure 7 ] WP1 ] Figure 8 ] WP2 ] Figure 9 ] WP3 ] Figure 10 ] WP1 - Stratigraphic Range ] Figure 11 ] WP2 - Stratigraphic Range ] Figure 12 ] WP3 - Stratigraphic Range ] Figure 13 ] [ Event Stratigraphy ] Figure 14 ]

Preface ] Introduction ] Unified Stratigraphy ] Pre-Neogene Framework ] Miocene to Lower Pliocene ] Lower Pliocene To Holocene ] High-Resolution Stratigraphy ] Key Geoseismic Sections ]


This page was Last updated 17 September 2002