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Centre for Earth and Environmental Science Research

Palaeobathymetry of the northern North Sea: Cretaceous to Recent

Executive Summary
Researchers Professor Gavin K. Gillmore,
Dr Tomas Kjennerud (Exploro Norway).
Funding Body/Source Exploro Norway
Duration 1999 - ongoing
Project SummaryThis research work is focussed on the development of basin reconstruction models utlising bath gemetric restoration and micropalaeontological palaeowater depths for the northern North Sea.

Kjennerud et al (2001) developed a 2D structural restoration method that has been further developed into a 3D palaeobathymetry approach (see Kjennerud & Sylta, 2001). The reconstruction approach is implemented in 'Palaeowater' software which is a module in the basin modelling tool Semi.

The method employed incorporates geological 'observations' derived fromseismic and well data that are used to form the basin shape.

The restoration method then integrates relevant information from:-

Micropalaeontological water depth estimates

Elphidium crispum, northern North Sea

This new eclectic approach (Gillmore et al., 2001) to micropalaeontological data utilises new ideas and evidence in order to greater understand palaeobathymetry and basin evolution. Palaeobathymetric curves with upper and lower depth limits are derived in part from statistical analyses of micropaleontological data to present the most likely depth variations through time in a region. Benthic foraminifera have often been used to estimate palaeowater depths, but in the past there has been a lack of substantial theoretical or observational basis for the depths proposed. This work goes some way towards addressing this imbalance. The measures used in this work to assess palaeowater depths includes the use of plankton: benthonic ratios (P;B%); P;B% versus non-calcareous agglutinants (NCA%); Tau values: data on ancient and modern tolerances of selected taxa; modern generic and assemblage analogues; morphogroups; measures of foraminiferal diversity; multivariate statistical approaches (e.g. constrained clustering).

This restoration method then utilises two main depositional scenarios:-

Passive infilling of a relief
Active progradation of sediments into a basin

Passive Infilling

The topography at the base of an infilling sequence is restored assuming that the overlying maximum sediment thickness will reflect the areas of maximum palaeo-waterdepth. Thus, the isopach of the overlying sedimentary unit will reflect the relative topography of a basin. This iscalibrated using areas of zero water depth and micropalaeontological estimates as the most relevant input parameters.

Active Progradation

In prograding sequences, sediment thickness is inversely correlated to palaeo-waterdepth , i.e. the maximum thickness will correspond to the shallowest area. The decompacted clinoform geometry is used to shape the proximal part of the basin, while the distal part may be restored according to the infilling approach described above. Micropalaeontological estimates are normally not given priority to in prograding settings, as geometry and height of the clinoform are regarded as certain bathymetry indicators.

Publications

Gillmore, G.K., Kjennerud, T., Kyrkjebo. R. 2001. The reconstruction and analysis of palaeowater depths: a new approach and test of micropalaeontological approaches in the post-rift (Cretaceous to Quaternary) interval of the northern North Sea. In: Martinsen, O. & Dreyer, T. (eds.): Sedimentary Environments offshore Norway - Palaeozoic to Recent. Norwegian Petroleum Society Special Publication, 10, 365-381.

Kjennerud, T., Faleide, J.I., Gabrielsen, R.H., Gillmore, G.K., Kyrkjebo, R., Lippard, S.J. & Loseth, H. 2001. Structural restoration of Cretaceous-Cenozoic (post-rift) palaoebathymetry in the northern North Sea. In: Martinsen, O. & Dreyer, T. (eds.): Sedimentary Environments offshore Norway - Palaeozoic to Recent. Norwegian Petroleum Society Special Publication, 10, 347-364.

Kjennerud, T. & Sylta, S., 2001. Application of quantitative palaeobathymetry in basin modelling. Petroleum Geoscience 7, 331-341.

Kjennerud T. & Gillmore G. K., 2003. Integrated Palaeogene palaeobathymetry of the northern North Sea. Petroleum Geoscience 9, 125-132.

Associated Research Groups

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