Slide Block(?) of Jurassic Sandstone and Submarine Channels in Basal Upper Cretaceous of Viking Graben: Norwegian North Sea

K. A. Alhilali, John E. Damuth

An apparent slide block of Jurassic-age Brent Group strata plus two large submarine channels are recognized in a seismically anomalous sequence of mid-Cretaceous (Cenomanian-Turonian) basin fill in the northern Viking graben, Norwegian North Sea (Lease Block 34/8). This slide block(?) apparently detached from the upthrown fault block bounding the west side of the graben (34/8 structure) and slid down the fault scarp onto the graben floor. The strongest evidence that this feature is an allochthonous block of Brent strata is the highly reflective, well-stratified internal seismic character that often exactly matches, in every detail, the seismic character of in-situ Brent Group strata observed within the upthrown fault block (34/8 structure). Additional evidence is the limi ed regional extent of the slide block(?) as well as apparent disturbance or deformation of basin-fill strata at the toe of the block. The slide block(?) was apparently detached and displaced to its present position either solely by sliding or by a combination of faulting and sliding associated with normal fault movements along the graben flank during middle Cretaceous time. If the slide block(?) is composed of Brent Group strata, as suggested here, then the block represents an additional hydrocarbon prospect (~ 100 MMBO) in Block 34/8 because the Brent Group is the main hydrocarbon reservoir in this region. In addition to the slide block(?), the mid-Cretaceous basin-fill sequence also contains two broad submarine channels that trend southward from the southern tip of the slide block(?) i to the graben floor. These channels appear to head along the boundary fault scarp of the graben and are erosional features formed by turbidity currents and mass-wasting processes in a deep-water environment.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.