The North Falkland Basin: An Extension of the Petrolific South Atlantic Lacustrine Rift Plays

Abstract

The North Falkland Basin is an intracratonic failed rift associated with the opening of the South Atlantic in the Early Cretaceous. It exhibits many similarities with other South Atlantic basins, although it is not often included in analyses of the South Atlantic. The northern rift displays simple shear extension setting up a series of half graben structures. The basin fill typifies that seen in many rift basins, starting with fluvial and alluvial fan deposition evolving to lacustrine and eventually becoming marine. There is a proven hydrocarbon system with discoveries and current exploration is focused on the lacustrine system. It is generally accepted that the primary controls on lacustrine rift systems are tectonics and climate, which provide both the accommodation and the fill (water + sediment). There are still disagreements as to whether the “climate” component is dominantly driven by local climate (at the lake) or the climate in the drainage basin of the fluvial systems feeding the lake. The South Atlantic lake systems, including the NFB, span 48 degrees of latitude. Because climate inherently varies by latitude, similarities and differences between these lacustrine systems will also vary by latitude if the primary driver is the local climate. The NFB lacustrine play contains a rich oil prone Type I source rock with little evidence of terrestrial plant input. The waxy black oil that is generated clearly indicates a dominantly algal component in a likely stratified lake setting. The reservoirs are both narrow, point sourced turbidites, as well as stacked basin floor fans derived from the bounding fault margin. The associated deltaic systems demonstrate strong progradational signatures with some aggradation. The lake widens through time, but is still very deep at the time of deposition of these reservoirs. These characteristics are strikingly similar to equivalent plays in basins along both the South American and African margins. Given the latitudinal range, there should be little similarity between the NFB lacustrine system and those in northern South Atlantic. In fact, we find the opposite to be true. We will explore the parallels between the NFB and the lacustrine systems from Potiguar to Campos on the South American side, and from Gabon to Benguela on the African side, and discuss local vs extrabasinal controls as they pertain to source, reservoir, and seal play elements.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016