Sediment Mass Budget for the Middle Jurassic “Brent Delta” Sediment Routing System, Northern North Sea

Abstract

Sediment Mass Budget for the Middle Jurassic “Brent Delta” Sediment Routing System, Northern North Sea

Ikenna C. Okwara*, Gary J. Hampson, Alex C. Whittaker, and Gareth G. Roberts

Department of Earth Science and Engineering, Imperial College London, United Kingdom

(* corresponding author: [email protected])

Sediment mass-balance analysis offers first-order quantification of the influence of sediment supply and accommodation generation on stratigraphic architecture, and associated tectonic and climatic signals. Here, we investigate the stratigraphic architecture and reservoir distribution of the Middle Jurassic “Brent Delta” sediment routing system in the embryonic Viking Graben, North Sea basin, offshore UK and Norway, using the concepts of sediment mass-balance analysis and downsystem grain-size fractionation.

Published sequence stratigraphic studies are synthesized to provide an age-constrained framework of the “Brent Delta” system over a depositional length of c. 350 km. The framework consists of four chronostratigraphic intervals, each of duration 2-8 Myr, and that together span 179 – 157 Ma. Unit 1 corresponds to coeval eastward and westward progradation of coarse-grained fan deltas from the margins of the basin, sourced from the Shetland Platform and Norwegian Landmass, respectively. Units 2 and 3 correspond to the relatively rapid northward progradation and subsequent aggradation of the “Brent Delta” along the basin axis, sourced from the uplifted Mid-North Sea Dome to the south, together with contributions from the western and eastern basin margins. Unit 4 records the drowning of the “Brent Delta” in response to the onset of active rifting within the basin.

Sediment budgets, facies partitioning, and grain-size fractionation are estimated for the four chronostratigraphic intervals along depositional transects that are constrained by published paleogeographic maps, isopachs, and sedimentologic analysis of core and well-log data. We assess the degree to which temporal changes in both the volume and grain-size distribution of sediment was influenced by both catchment area characteristics (hinterland tectonics and climate) and basin tectonics, and how these controls resulted in observed stratigraphic architecture. The results of this study provide quantitative parameters that can be used to calibrate and/or test forward stratigraphic models of the “Brent Delta” system, and illustrate how the concepts of sediment mass-balance analysis and downsystem grain-size fractionation can be used to refine stratigraphic architecture and assess reservoir distribution in paleo-sediment routing systems.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019