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Changes in outbuilding directions and shifts in sediment provenance are key factors for understanding the development of the Cenozoic succession in the central and northern North Sea. By establishing a seismic stratigraphic framework for the Cenozoic succession, and through utilization of velocity data and analyses of sediment compositions, these factors are investigated. Sequence geometries and reflection terminations are identified and related to basin-floor geometry and variations in erosional base level. Mineralogical and geochemical analyses of sediment samples from selected wells are compared with their seismic sequences. Paleogene clastic wedges rich in smectite were built from the East Shetland Platform and probably drained a source area west and northwest of the present North Sea. Outbuilding from southern Norway took place during Late Paleocene-Early Eocene and in Oligocene to mid-Miocene time. In mid-Miocene time outbuilding from the west stopped and subsequently sediments with a high content of feldspar, detrital chlorite and carbonate were deposited from easterly directions in the central and northern North Sea. The seismic velocity of the Cenozoic sediments increases down to a mid-Miocene unconformity, but the velocities of Oligocene and Eocene sediments below are lower and nearly unaffected by burial depth, resulting in a marked velocity inversion. Two tectonic subsidence events, late Eocene-early Oligocene and late Miocene-early Pliocene, have been identified subsequent to general eustatic sea-level lows. These subsidence events cannot be explained by thermal subsidence, and they may have crucial implications for the understanding of hydrocarbon generation, migration and trapping in the Tertiary and deeper stratigraphic levels.

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Clay-mineral compositions have been analyzed in samples from the Danish, Norwegian, British, and Dutch North Sea sectors and from onshore Denmark and Germany, comprising both wells and outcrops (clay pits and cliff sections). The time slices investigated comprise from the Paleogene, the post-Ekofisk Fm. interval of the Paleocene, the entire Eocene, and the entire Oligocene. The Neogene time slices investigated comprise the following Miocene intervals: the Vejle Fjord Fm., the Klintinghoved Fm., the Arnum Fm., and the Gram Fm. There were not enough samples from offshore wells to make a detailed stratigraphic subdivision of the Paleogene. It was, however, possible to refer Miocene samples to specific lithostratigraphic units. The onshore Danish nomenclature was applied, and seismic sections were used to correlate between wells and outcrops. Existing biostratigraphic data were used to control the stratigraphic interpretation. The distribution of the most dominant clay minerals-smectite, chlorite, kaolinite and illite-are shown on maps comprising the Paleocene, Eocene, Oligocene, and the formations Vejle Fjord Fm., Klintinghoved Fm., Arnum Fm., and Gram Fm. from the Miocene.The investigation has shown that the source-rock composition plays an important role in the clay-mineral content of the sediments. For example, smectite makes up a higher proportion in periods with substantial supply of volcanic material, especially in the Paleocene and early Eocene. In source areas, where metamorphic rocks dominate, chlorite is present in the sediment adjacent to these areas. The illite content in sediments increases where the source area is dominated by granites and/or gneisses. Sorting of the supplied suspended material generally controls the depositional area for the minerals. For example, the larger particles of kaolinite are generally more abundant in nearshore areas, whereas the relatively small smectite particles normally dominate in the central parts of the sedimentary basins. Illite and chlorite are relatively abundant in areas between those rich in smectite, present in the central part of the basin, and those rich in kaolinite, present in the marginal parts of the basin. Climatic conditions during erosion and deposition seem to play an important role, especially in the distribution of chlorite, which is rather sensitive to chemical weathering. This means that chlorite makes up a greater proportion of the sediment in periods with colder climate, such as in the Oligocene and late Miocene.

This thesis entitled "Compaction of siliceous sediments-Implications for basin modeling and seismic interpretation" has been submitted to the Department of Geosciences at the University of Oslo in agreement with the requirements for the degree of Philosophiae Doctor (Ph.D.) The work presented in this study was completed as part of a large research project funded by The Research Council of Norway within the PETROMAKS program (Program for Optimal Management of Petroleum Resources) entitled "Petrophysical properties of mudstones and sandstones and their seismic response". The study is based on results from well log data in natural sediments from the Norwegian continental shelf. The derived compaction results have been integrated with results from experimental compaction studies performed within the same PETROMAKS project (Mondol, 2007). In addition, some of the work presented herein was completed in collaboration with a FORCE research project (Norwegian Sea Research Consortium) sponsored by ConocoPhillips, Gaz de France, Norsk Hydro and Statoil. The thesis comprise of an introduction together with six individual papers. A brief scientific introduction to the topic, the main objectives, summary of the papers enclosed, and finally some concluding remarks are given in the introduction. Three of the papers vi