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The study describes a large (kilometre-scale) composite mud volcano system within the North Sea Chalk Group, containing both intrusion and extrusion features. The upper part of the system consists of three stacked constructive components. At the top, a Late Palaeocene mound-shaped extrusion with subtle onlaps is observed. Below, a Danian near-surface intrusion caused forced-folding of the c. 100 m thick overburden. This is underlain by a shallow intrusion. The lower part of the mud volcano system is defined by a depletion-related depression and the fluid conduit. Seismic data suggest that the source unit for the linked intrusion--extrusion is to be found either within a Lower Cretaceous diapiric siliciclastic structure or within the fine-grained carbonates of the Chalk Group. The latter is more probable, implying that chalk may generate hitherto undocumented intrusions and extrusions comparable with siliciclastic mud volcano systems. Remobilization is inferred to have been driven by finidization caused by the influx of mainly pore water expelled from the Lower Cretaceous succession. A distinct depositional variation within the Chalk Group caused early diagenetic differences in porosity preservation and mechanical properties of the chalk units, allowing the remobilization of certain chalk units even at burial depths as great as 200 m. doi: 10.1144/0016-76492010-037.

The study presented in this paper aims to investigate the prospects of using bender elements in the offshore industry for determining shear wave velocity of fragmented, fragile and brittle clay samples and cuttings. The result from the study shows that the laboratory-measured S-wave velocities of intact samples of Søvind Marl, a sedimentary stiff Palaeogene clay, in general, are lower than those determined from in-situ seismic cone penetration testing. The reason may be unavoidable volume-constant distortion and changes to effective stress conditions experienced by the natural clay upon sampling and subsequent sample preparation. Correlation between the size of the samples and velocity is not noticed. In contrast, the S-wave velocities for natural samples that were remoulded and then reconstructed are observed to be comparable with the in-situ seismic measurements, however, the results are found to be dependent on sample density. The influence of cross-talk, near-field, and boundary effects on the results is assessed. [ABSTRACT FROM AUTHOR]