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The Buzzard Field: Breaking from Traditional Conventions in Turbidite Concepts

Chantale K. McIntosh
Heriot-Watt University, Edinburgh, United Kingdom

Turbidite facies models have been constantly evolving since pioneering work in the 1960's and 70's. Originally presented as a vertical sequence of sedimentary structures, models have more recently been applied to spacial distributions and longitudinal facies trends from proximal to distal, in order to describe theoretical and observed patterns in turbidite deposits. The dominant trend in all of these models is the persistence of massive sandstone facies in the most proximal regions with an increase in tractional structures in a down-dip (distal) direction. In contrast to this model, the broad distribution of facies in the Buzzard Field displays the reverse trend, with thick accumulations of parallel-laminated sandstones in the proximal regions and massive sandstones prevailing further basinward. This unusual development of thick, parallel-laminated sandstones in proximal regions could be attributed to: (1) by-pass by repeated, short-lived flows in the most proximal regions, (2) basinal palaeobathymetry imparting some control on facies development, or (3) flow acceleration in a sustained event in proximal, base of slope, regions, with minor deposition and accumulation and reworking by the overriding flow. A lack of major erosive surfaces within the laminated sandstone facies and its presence in proximal regions of other basins with little bathymetric control (e.g. Eocene deposits in Spitsbergen and the Mount Messenger Formation, New Zealand), suggest that (3) is the most probable explanation. By implication, the majority of sand introduced to the Buzzard sub-basin would have been transported and deposited basinward of the proximal laminated sandstone facies.