Abstract Outcrop sections containing excellent physical and biogenic sedimentary structures within the Late Permian Ecca Group are exposed within the Tanqua Karoo that show the transition from shelf margin delta through to slope and basin floor fans. The Tanqua submarine fan complex comprises six regionally distinct fan systems, five of which form a progradational stack with the sixth fan, to the south, downlapping onto the fifth fan. Progradation of the deltaic deposits across the basin has been in response to a decrease in accommodation space created by relatively high rates of sedimentation within the foreland basin setting. The sedimentology and sequence stratigraphy of the Hangklip Fan represents a shelf margin delta feeding downdip slope fan deposits. Wave ripples, swaley cross-stratification and trace fossils, including Gyrochorte , suggest substantially shallower depositional conditions than slope fan deposits, which are devoid of such features. Erosional slump scars, cutting into laminated shale with chaotic infill of sand intraclasts, point toward slope depositional processes that are not in evidence in the underlying submarine fan deposits.

Abstract The Permian Tanqua and Laingsburg subbasins in the southwestern Karoo Basin, South Africa, had near-contemporaneous formation and filling. Five submarine fan systems are in the broad, shallow Tanqua subbasin and four in the more typical foredeep-style Laingsburg subbasin. Petrologic and micro-probe analysis of the sandstones indicates a distant source area. Tectonic events led to varying sea-floor topography that directed sediment transport to the subbasins. Tectonic activity was low to nonexistent during deposition of any one or more of the submarine fans and indicates that the depositional cycle is much shorter than a tectonic cycle. The tectonic style of a basin may not always define the sedimentary characteristics of turbidite systems deposited in that basin.

Abstract The Permian Tanqua fan complex, SW Karoo Basin, South Africa, is unde-formed and well exposed, allowing 3-D viewing of outcrops that are laterally continuous over tens of kilometers. The complex consists of six sand-rich tur-bidite systems, separated by basin shales. The first five form an incrementally prograding, laterally compensating set, whereas the sixth fan, located to the south, downlaps onto Fan 5. Although deposited in a basin flanked by an oro-genic belt, the Tanqua fan complex has depositional characteristics similar to fans deposited in passive margin settings. It is a fine-grained, mud-rich bypass system deposited within an unconfined basinal setting. The deposits show architectural and reservoir character changes as they occur from the base-of-slope to their distal termination.

Abstract The Late Permian Ecca Group (1300 m thick) in the Tanqua Karoo consists of a basin floor fan complex (400 m thick), overlain by river-dominated deltaic deposits and associated updip fluvial deposits. This succession is subdivided into two “third-order” depositional sequences with several superimposed high-frequency, “fourth-order” depositional sequences. The Tanqua submarine fan complex contains six regionally distinct fan systems (24 to 60 m thick), five of which form a progradational stack, as revealed by their spatial distribution and regional facies variation. The sixth fan is situated to the south and downlaps onto the fifth fan. This long-term (third-order) progradational pattern records a combination of reduced accommodation space and/or increased sediment supply. Each fan system is assigned to the lowstand systems tract of each high-frequency, fourth-order sequence, and the particular attributes of each fan system are a consequence of their respective positions within the lower-frequency third-order sequence.

Abstract Superb sections of submarine fan deposits within the Late Permian Ecca Group are exposed within the Tanqua Karoo basin. Five discrete fan systems are capped by shales and deltaic deposits of the Kookfontein and equivalent Koedoesberg formations. Progradation of the deltaic deposits across the basin was in response to a decrease in accommodation space created by relatively high rates of sedimentation within the foreland basin setting. Evidence for the transition from submarine fans to deltaic deposition has been enigmatic, with limited evidence of sediments representative of slope deposition. The sedimentology and sequence stratigraphy of the Hangklip Fan represents a slope fan and channel complex that shallows up into deltaic deposits, coincident with decresing accomodation space. Erosional slump scars, cutting into laminated shale with chaotic infill of sand intraclasts, point toward slope depositional processes that are not in evidence in the underlying submarine fan deposits. Wave ripples and the trace fossil Gyrochorte suggest substantially shallower depositional conditions than either the submarine fan or slope fan deposits, which are devoid of such features.

ABSTRACT The Permian Tanqua subbasin in the southwestern Karoo Basin, South Africa, contains five basin-floor fans and one slope fan. The total outcrop area is about 650 km in size; the individual outcropping fans range in size from about 150 km 2 to 450 km 2 . The arenaceous fans have a high sandstone/shale ratio of about 75-90%, range in individual thickness from 20-60 m, and are separated by 20-75m thick basin shales. Deposition of each fan is in response to a 4th-order, tectonically controlled relative sea-level lowering within a 3rd order transgressive systems tract. Two basin-floor fans show mid-fan channel complexes with levee-overbank deposits which change in downdip direction into non-channelized, sheet-like outer fan depositional lobes. Simultaneously, the sandstone/shale ratio increases in the same direction. The other three basin-floor fans contain outer fan depositional lobes. Four of the basin-floor fans show paleocurrent directions from SSW and S, whereas one was fed from the W-WNW. Absence of folding provides ideal lateral correlation; cliff-type outcrops occur over a distance of 34 km. Three 8-12 km long E-W outcrops with only minor regional tilt complete the major data source. A channel complex, assumed to be deposited at the base-of-slope, is found in the most proximal area. The complex comprises both large and small, rather shallow, channel fills with erosional contacts and remnants of probable thin-bedded levees. The single channels are embedded in thin-bedded turbidite series; some are connected physically to the channel fill. Such levee deposits can be composed of very clean sands with thin shales, and have well-developed cross bedding and climbing ripples. They show a significant issuing angle (25-35°) in paleocurrent direction from the channel. The sheet sands comprise bundles of 6-8 very flat, often amalgamated, lenticular sandstone beds. The amalgamated contacts change laterally into thin shales. Sheet sand bundles are slightly lenticular which is extremely difficult to discern on cursory examination of photo-mosaics of long outcrops, but can be demonstrated by careful bed tracing. The long outcrops make it possible to collect field data required to 1) improve our understanding of the overall architecture of fine-grained, “low” sandstone/shale ratio submarine fans, and 2) to carry out detailed reservoir simulation programs.