Ron J. Steel¹, Donatella Mellere², Piret Plink³
(1) University of Wyoming, Laramie, WY
(2) Statoil, Stavanger, Norway
(3) University of Gothenburg, Gothenburg, Sweden

Abstract: Towards prediction of deepwater sands on slope and basin floor

Four types of clinoform, with amplitudes up to about 350 meters, have been documented along seismic scale (10km x 1km) moutainside exposures in Spitsbergen's Central Tertiary Basin. The clinoforms record the infill of the foreland basin from the fold-and thrust belt side. The trajectory of the shelf edge, traced through successive clinoforms, varies from subhorizontal to gently rising. Only few of the clinoforms have significant thicknesses of associated deepwater sands. A database of facies variability along the 3 segments (shelf, slope and basin floor) of the studied clinothems allows an approach to a predictive model for the likely absence or presence of deepwater slope and basin-floor sandstones.

Basin-floor turbidite accumulations and slope turbidite wedges, associated with only some of the clinoforms, reach thicknesses of up to 80 meters. The former sandbodies include thick, high-density sandy flows, extend up to 10 km from the base of slope and are at least 2-3 km in width after they emerge from the base of slope. The slope wedges are made up of rapidly thinning, lower density turbidites generated from hyperpycnal flows and small slumps. Water depths at the base of slope varied from 200 to 400 meters, and the slopes reached angles of 4 degrees.

Criteria which need to be known for the prediction of the presence or absence of slope or basin-floor sands include the nature of the shelf regime, and the trajectory of the shelf edge through time. Clinoform amplitude, slope and geometry are less important criteria.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana