Morphologic Architecture of a Coarse-Grained Turbidite: An Outcrop Study of the Scotland Formation, Barbados, West Indies

Chaderton, Nysha A. N.¹, Lesli Wood² (1) The University of Texas at Austin, Austin, TX (2) University of Texas at Austin, Austin, TX

The Scotland Formation is a turbidite succession composed of coarse-grained sandstones and shales. The only exposures of this formation are located in the northeast part of the island of Barbados, where the Pleistocene limestone cap has been eroded to expose the Tertiary rocks of the Barbados accretionary prism. These units are thought to form the reservoir in the Woodbourne oilfield, which is located onshore Barbados and is the only productive oilfield in the world known from an accretionary prism.

Outcrop characterization of the Scotland Formation integrates photomosaic architectural panels and measured sections that investigate architecture of the formation, facies distributions, vertical successions, gamma response, and patterns of the unit.

Some sand bodies observed in outcrop are laterally continuous for over 100 m, and others show erosional bases and channelized character. Six facies have been identified in outcrop: silty shales; laminated, centimeter-scale sandstones interbedded with silts and shales; cross-stratified sandstones; massive, medium- to coarse-grained sandstones; very coarse grained sands with gravel or pebbles; and rare conglomerates. These facies, combined with architectural elements such as channels, levees, slumps, and depositional lobes, produce highly variable geometries within the system and are indicative of a slope-apron to midfan depositional setting

An integrated study of the measured sections and well logs forms the basis of a new geologic model of the subsurface reservoir units within the Woodbourne oilfield.