CHARACTERIZING THE CONTINENTAL-SCALE STRATIGRAPHIC ARCHITECTURE OF AFRICA AND THE MIDDLE EAST USING SLOSS-TYPE SEQUENCES

Sequences are defined as discrete packages of sedimentary rock bounded by interregional erosional surfaces. They are the ideal stratal units for regional stratigraphic study, but few continent-wide studies have been published. We present a new continental-scale study of the six, Sloss-type sequences across Africa and the Saudi Arabian Peninsula, with emphasis on stratigraphic architecture.

Details of the sediments across Africa and the Saudi Arabian Peninsula, including offshore shelf regions, were compiled using available publications, seismic data and well records. RockWorks 17 software was used to track sequence boundaries, lithologic data and locations. A three-dimensional lithology model was created along with isopach maps and basal sequence lithology maps for each of the six sequences.

Results show siliciclastics dominated deposition in the earliest three sequences (Sauk, Tippecanoe and Kaskaskia). However, their areal extent was primarily limited to North Africa and the Middle East. Likewise, the volume of siliciclastics deposited in the first three sequences was also limited, averaging only about 5.8 million km³ per sequence. In contrast, the latter three sequences (Absaroka, Zuni and Tejas) show a more diverse mix of carbonates and siliciclastics and a dramatic increase in both areal extent and sediment volume, with a peak total of over 57.2 million km³ of sediment deposited in the Zuni sequence. Siliciclastic deposition within the Absaroka sequence totaled 11.8 million km³, reached a peak in the Zuni with 38.7 million km³ and fell back to 13.0 million km³ in the Tejas. The Zuni sequence contains 42.5% of all sandstone and 52.2% of all shale deposited across Africa and the Middle East.

Carbonate deposition reflected a similar pattern in the latter sequences with 5.2 million km³ deposited in the Absaroka, 16.3 million km³ in the Zuni and 6.7 million km³ in the Tejas. The relative amount of carbonate deposition increased with every sequence, but showed a sharp increase in the Absaroka (26.3% of the total carbonate deposition) and continued through the Zuni (28.3% of the total) and the Tejas (29.4% of the total). Isopach maps and lithology models show most of the deposition in the latter three sequences was spread across central Africa, the continental margins and offshore.