Is Deposition of Continental Reservoirs Driven by Mega-Monsoonal Oscillations?—Upper Triassic of Canada, Morocco, and Algeria

Nadine Katja Mader and Jonathan Redfern
Manchester University, UK, Manchester, United Kingdom

This study of Upper Triassic (Carnian-Norian) continental fluvio-aeolian reservoirs assesses controlling factors on sediment distribution on a regional scale in a comprehensive study of time and facies equivalent siliciclastic deposits within geographically separate basins that developed on the super continent Pangaea. The study provides an outcrop analogue for the prolific TAGI (Triassic Argilo-Gréseux Inférieur) which is currently one of the main hydrocarbon reservoirs in Algeria, and tests alternative methods to improve correlation in continental settings. The separation of local from regional controls (tectonics versus climate) on cyclicity is in the spotlight, testing the hypothesis that sediment deposition in low palaeolatitudes of ~15-25° N on the supercontinent was driven by mega-monsoonal oscillations. Outcrop, core and well-log data is integrated on a basin-by-basin scale comparing the Fundy-Minas Basin (E Canada) and the Agadir-Essaouira Basins (SW Morocco) with subsurface data from the Berkine Basin (Central Algeria).

Results of outcrop analogue studies from the Upper Wolfville Formation (Canada) and the Tadrart Ouadou Sandstone Member (T6) (Morocco) are compared. Both sequences consist of synrift deposits related to the break-up of Pangaea. Although the deposits show high lateral variability in sedimentary facies over short distances, the sections reveal three to four, vertically stacked sedimentary units recognisable both in Morocco and Canada. It is suggested that the observed sedimentary cycles were influenced by palaeoclimatic alternations from humid to arid conditions within an overall trend of increasing aridity during the Upper Triassic on a regional scale, while tectonics and subsidence affected the long-term stratigraphic evolution of these basins.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005