DAVIES, RICHARD J., KEVIN J. STEPHEN, and JOHN R. UNDERHILL, Univ. of Edinburgh, Department of Geology and Geophysics, Edinburgh, Scotland, UK

ABSTRACT: The Integrated Tectono-Sedimentary Sequence Stratigraphy of the Bathonian to Kimmeridgian (Early Rift) Succession, Moray Firth Basin, North Sea

The Middle-Late Jurassic succession of the Moray Firth basin was deposited in a variety of marine a paralic environments during a significant (second order) transgressive episode, related to deflation of the North Sea thermal dome. Successful application of sequence stratigraphic methodology using detailed biostratigraphic data, electrical well logs, cores, onshore exposures and seismic data has enabled this interval to be sub-divided into at least ten third-order depositional sequences. The distribution and sedimentary style of these sequences is complex with sequence architecture being largely controlled by variable and increased subsidence rates related to the onset of rifting in the late Oxfordian and differential sedimentation rates associated with the sympathetic erosion of upli ted footwall shoulders.

The methodology adopted here has allowed for a new detailed and unifying correlation from the Inner Moray Firth into the Witch Ground Graben. The results highlight a number of existing anomalies between inter-field correlations and show that most of the reservoir horizons are shallow marine sandstones incised into the shelf during sea-level lowstands. The construction of a new stratigraphic template enables the production of more accurate palaeogeographic and isopach maps which give important insights into the timing and nature of the progressive eastward migration of facies belts from the Inner to Outer Moray Firth. They also demonstrate the role of fault movements in controlling local sediment dispersal patterns. As such, this study clearly shows the resolving and predictive power o the sequence stratigraphic technique which should enable more accurate reservoir predictions in this economically-significant area.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.