Abstract

Application of a multidisciplinary stratigraphic approach has significantly improved understanding of the vertical and lateral distribution of reservoir sandstone bodies and associated sediment pathways of the Sea Lion Field in the North Falklands Basin (NFB). Bio- and chemical stratigraphy combine to provide a robust framework capable of providing subseismic resolution to sandstone layering within the lacustrine setting of the basin, as well as highlighting the geochemical link between the timing of sandstone deposition and specific sediment supply points. The Barremian–Aptian mudrocks that host the Sea Lion reservoirs are uniform deep-water, anoxic shales with limited regional, chronostratigraphic resolution. In the absence of marine planktonic groups and with the scarcity of age diagnostic taxa, use has been made of locally correlative bioevents that have provided resolution to characterize and correlate most of the Sea Lion reservoir units or to provide some further subdivision of seismically defined units.

Chemical stratigraphic analysis (X-ray fluorescence (XRF)) initially yielded a highly variable set of data that cross-correlated biostratigraphic and seismic data, indicating that the controls on elemental character were not primarily stratigraphically controlled. An innovative approach to interpretation is described that brings together stratigraphic and geographical geochemical variation, and, by accommodating diachroneity, has resulted in a detailed sequencing of the individual turbidite fan systems, from the perspective of evolving and migrating sediment supply points into the NFB. The use of geochemical data has also provided a basis for the subseismic resolution and subdivisions of sandstone units.

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