Factors controlling the Cenozoic sequence development in the eastern parts of the North Sea

Abstract

The causal relationship between the Cenozoic sequence development in the southeastern North Sea Basin and sea-level changes, climatic fluctuations and tectonic events is unravelled by relating variations in the relative sea level and base level, based on interpretations of seismic surveys, to published δ 18 O variations and eustatic changes. The latter curve is based on the Earth's orbital forcing, and here informally termed as the GSI curve. The analysis shows that the Cenozoic sequence development in the southeastern North Sea was influenced by climatically and tectonically induced sea-level changes. The major Cenozoic sequence stratigraphic boundaries (lower order) are highly influenced by tectonic events, e.g. uplift of Fennoscandia and increased subsidence rates in the basin centre. Reactivation of Mesozoic fault zones controlled the deposition of minor sand bodies transported to the centre of the basin during the Late Palaeocene by mass flows. The location of an Oligocene mound structure, which constitutes part of a sequence, is controlled by the overall palaeotopography of the basin and local fault-related depressions. Correlation between (i) the ages of our sequences and the δ 18 O variations in the Oligocene succession, and (ii) the GSI curve and the base-level fluctuations of the late Miocene and younger sequences, show that the generation of the higher order sequence boundaries were driven by glacio-eustatic sea-level changes. A climatic control of the sequence formation due to glacio-eustatic sea level changes is therefore suggested for the Oligocene and Pliocene sequences, and probably also for the Upper Miocene sequences.

The early Quaternary North Sea Basin

“…In the southern end of the basin, however, with an initial water depth of c. 300 m, only 350 m of sediment accumulated to fill the earliest Pleistocene accommodation. This part of the basin fill is a direct continuation of the rapid progradation that filled in the southeastern North Sea Basin during the post-middle Miocene (Clausen et al 1999;Harding 2015). It is thus likely that flexural loading by the Pliocene clinoforms may have already preloaded this part of the basin, thus limiting the vertical isostatic component.…”

Deep structure of the northern North Sea and southwestern Norway based on 3D density and magnetic modelling

“…Finally, the central part of the North Sea has been affected by a regional subsidence with deposition of more than 3 km of sedimentary rocks during the Cenozoic (e.g., Maystrenko et al, 2012). The nature of this Cenozoic subsidence is still under debate, possibly involving the cumulative effect of several tectonic processes (White, 1989;Morgan, 1990;Ziegler 1990;Clausen et al, 1999;Jordt et al, 2000;Kyrkjebø et al, 2000;Frederiksen et al, 2001b;Hansen & Nielsen, 2003;Scheck-Wenderoth & Lamarche, 2005).…”

A morphometric analysis of tunnel valleys in the eastern North Sea based on 3D seismic data

“…The basin floor was blanketed by a thick layer of chalk during late Cretaceous time, preceding the last stage of infill during the Paleogene-Neogene, which resulted in some 3 km of Cenozoic siliciclastic deposits in the central North Sea. The last phase of sedimentation prior to the mid-late Pleistocene glacial period was characterised by pro-deltaic and deltaic sediments which gradually filled the basin from southern Scandinavia towards the southwest (Oligocene), then gradually shifting southwestwards (early Miocene) and west (late Miocene-Pliocene), leaving the North Sea region as a dominantly continental to shallow marine basin with a narrow central trough by the end of the Pliocene (Gibbard, 1988;Sørensen et al, 1997;Clausen et al, 1999;Huuse, 2002). The margins of the epicontinental basin were progressively exhumed during the Cenozoic giving rise to a distinctly symmetrical pattern of the Pleistocene subcrop, increasing in age towards and across the basin margins (Nielsen et al, 1986;Japsen, 1998).…”