ABSTRACT: Sequence Stratigraphy of the Synrift Fill, Danish Central Graben, North Sea

SELF, GREGORY A., Amoco Production Research, Tulsa, OK

Rifting in the Danish Central Graben began in the Early Triassic and ended during the Late Cretaceous. During rifting, six different tectonic phases resulted in deposition of one or more seismic stratigraphic sequences. The sequences deposited during a single tectonic phase of rifting often have common physical seismic stratigraphic characteristics and are referred to collectively as a tectonostratigraphic bundle.

Deposition of the initial sequence in a bundle is the product of change in the regional stress regime. Deposition of subsequent sequences within a bundle is controlled by either local tectonics, spatial variations in sedimentation patterns, sea level fluctuation, or a combination of several of these factors. The Upper Jurassic Phase II and Lower Cretaceous Phase IV are characterized by stratigraphic bundles best described as prograding depositional systems tracts, stacked in a cyclic vertical succession. Progradation is perpendicular to the footwall source area, defined by downlap and onlap along the basal boundary and toplap along the upper boundary. The physical stratigraphic observations, integrated with lithologic and paleontological data, indicate a shallow marine, deltaic enviro ment existed during both phases. Bidirectional downlap along strike suggests that the depositional axis becomes parallel to the rift axis away from the footwall source.

Structural inversion may reverse the relationship between sediment source area and depocenter. During tectonic Phases V and VI in the Late Cretaceous, erosion along an inversion axis resulted in the deposition of sedimentary wedges onto the adjacent rift margin. The wedges are characterized by subtle progradation away from and perpendicular to the axis of inversion with onlap and downlap onto an erosional base.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)