Deep Borehole Lithostratigraphy and Basin Structure of the Southern Karoo Basin Re-Visited

Linol, Bastien; Chere, Naledi; Muedi, Thomas; Nengovhela, Vhuhwavhohau; Wit, Maarten J. de

doi:10.1007/978-3-319-40859-0_1

Cited by 8 publications

(14 citation statements)

References 30 publications

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“…The Ecca Group is marked by the lowermost black, organic-rich shales directly above the Dwyka Group. Linol et al (2016) pointed out that the lowermost shale of the Ecca Group represents short-lived marine environment that resulted from rapid deglaciation of ice cap during Late Devonian to Middle Carboniferous. The middle to upper most units of the Ecca Group are more arenaceous, thicker and reflects transition into fluvial environments (Linol et al, 2016;Visser, 1989).…”

Section: Stratigraphymentioning

confidence: 99%

“…Linol et al (2016) pointed out that the lowermost shale of the Ecca Group represents short-lived marine environment that resulted from rapid deglaciation of ice cap during Late Devonian to Middle Carboniferous. The middle to upper most units of the Ecca Group are more arenaceous, thicker and reflects transition into fluvial environments (Linol et al, 2016;Visser, 1989). These units consist of dark-grey silty shales intercalated with fine grained sandstone and carbonaceous mudstones (Visser, 1989).…”

Section: Stratigraphymentioning

confidence: 99%

“…The final model was inspected to see if it was geologically reasonable. The models were constrained using the densities values, stratigraphic thickness from outcrops and SOEKOR borehole as well as seismic refraction and magnetotelluric images provided in Stankiewicz et al (2008) and Linol et al (2016). The Moho depth have been indicated to vary between 40-45 km below the sea level Stankiewicz and de Wit, 2013).…”

Section: Profile Selection and 2½ D Gravity Modelsmentioning

confidence: 99%

“…The Cape Fold Belt comprises of the Palaeozoic clastic sedimentary rocks of the Cape Supergroup that rests unconformably on the Precambrian basement rocks ( Bachtadse et al., 1987 ) and are in turn overlain by the rocks of the Karoo Supergroup ( Tankard et al., 2012 ). The Cape Supergroup is reported to have been deposited during the rising and falling of the ocean along a shallow continental-shelf that flanks the southern margin of Gondwana ( Linol et al., 2016 ).

Figure 1 Geological map of South Africa as compiled by the Council for Geosciences showing distributions of lithostratigraphic units and the location of geophysical profiles in the Karoo Basin.…”

Section: Introductionmentioning

confidence: 99%

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Variations in isochore thickness and depositional surface of the Dwyka, Ecca and Beaufort Groups in the Western Cape Province of South Africa as deduced from 2.5D gravity profile models

Nxantsiya

Gwavava

Baiyegunhi

2021

Heliyon

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A 2.5D gravity modelling along seven selected profiles that covers the Western Cape Province of South Africa was carried out to deduce the depositional surface and isochore (true vertical) thickness of the Dwyka, Ecca and Beaufort Group sediments. The results revealed that the Karoo Basin deepens to a depth of about 4600 m in the southwestern region, near the front of the Cape Fold Belt. Also, the model gives indication that the Karoo dolerite intrusions are interconnected at depth and are mostly concentrated at the centre of the basin. The isochore thickness maps show that the Beaufort Group is the thickest group in the Karoo Supergroup, with a maximum thickness of about 6046 AE 277 m, followed by the Ecca and Dwyka Groups with thicknesses of around 3720 AE 183 m and 765 AE 69 m, respectively. The maximum depositional surface (elevation) for the Dwyka, Ecca and Beaufort sediments are approximately 1696 m, 1247 m and 1491 m, respectively, whereas the maximum depth below sea level are around 3668 m, 3209 m and 480 m, respectively. Furthermore, the isochore thickness maps indicate that the Ecca Group, which is the main target for hydrocarbon exploration in the Karoo, thickens toward the south, away from the centre of the basin and reaches thickness of greater than 3680 m. The correlation of the depositional surfaces with the isochore thickness maps revealed that the sediments in structural high areas were subsided, eroded and deposited in structural low areas. Consequently, the structural low areas are characterised by thick sediments cover and vice versa.

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Section: Stratigraphymentioning

confidence: 99%

Section: Stratigraphymentioning

confidence: 99%

Section: Profile Selection and 2½ D Gravity Modelsmentioning

confidence: 99%

Figure 1 Geological map of South Africa as compiled by the Council for Geosciences showing distributions of lithostratigraphic units and the location of geophysical profiles in the Karoo Basin.…”

Section: Introductionmentioning

confidence: 99%

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Variations in isochore thickness and depositional surface of the Dwyka, Ecca and Beaufort Groups in the Western Cape Province of South Africa as deduced from 2.5D gravity profile models

Nxantsiya

Gwavava

Baiyegunhi

2021

Heliyon

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“…In the Laingsburg depocentre (Figure ), the Permian Lower Ecca Group comprises the Prince Albert, Whitehill and Collingham formations, which record an overall deepening of the basin and increasing siliciclastic supply during an icehouse to greenhouse transition (Johnson et al., ; Linol, Chere, Muedi, Nengovhela, & de Wit, ; Scheffler, Buehmann, & Schwark, ). The overlying Upper Ecca Group comprises a 1800‐m‐thick progradational succession from basin‐plain deposits (Vischkuil Formation; van der Merwe, Flint, & Hodgson, ; van der Merwe, Hodgson, & Flint, ; van der Merwe, Hodgson, & Flint, ) and basin‐floor fans (Units A–B, Laingsburg Formation; Sixsmith, Flint, Wickens, & Johnson, ; Flint et al., ), through a channelized submarine slope (Units C–G; Fort Brown Formation; Brooks, Hodgson, Brunt, Peakall, Poyatos‐Moré et al., ; Grecula, Flint, Potts, Wickens, & Johnson, ; van der Merwe et al., ) to shelf‐edge and shelf deltas (Waterford Formation; Jones et al., ; Poyatos‐Moré et al., ) (Figure ).…”

Section: Geological Settingmentioning

confidence: 99%

Clinoform architecture and along‐strike facies variability through an exhumed erosional to accretionary basin margin transition

et al. 2019

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Exhumed basin margin‐scale clinothems provide important archives for understanding process interactions and reconstructing the physiography of sedimentary basins. However, studies of coeval shelf through slope to basin‐floor deposits are rarely documented, mainly due to outcrop or subsurface dataset limitations. Unit G from the Laingsburg depocentre (Karoo Basin, South Africa) is a rare example of a complete basin margin scale clinothem (>60 km long, 200 m‐high), with >10 km of depositional strike control, which allows a quasi‐3D study of a preserved shelf‐slope‐basin floor transition over a ca. 1,200 km2 area. Sand‐prone, wave‐influenced topset deposits close to the shelf‐edge rollover zone can be physically mapped down dip for ca. 10 km as they thicken and transition into heterolithic foreset/slope deposits. These deposits progressively fine and thin over tens of km farther down dip into sand‐starved bottomset/basin‐floor deposits. Only a few km along strike, the coeval foreset/slope deposits are bypass‐dominated with incisional features interpreted as minor slope conduits/gullies. The margin here is steeper, more channelized and records a stepped profile with evidence of sand‐filled intraslope topography, a preserved base‐of‐slope transition zone and sand‐rich bottomset/basin‐floor deposits. Unit G is interpreted as part of a composite depositional sequence that records a change in basin margin style from an underlying incised slope with large sand‐rich basin‐floor fans to an overlying accretion‐dominated shelf with limited sand supply to the slope and basin floor. The change in margin style is accompanied with decreased clinoform height/slope and increased shelf width. This is interpreted to reflect a transition in subsidence style from regional sag, driven by dynamic topography/inherited basement configuration, to early foreland basin flexural loading. Results of this study caution against reconstructing basin margin successions from partial datasets without accounting for temporal and spatial physiographic changes, with potential implications on predictive basin evolution models.

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Constraining Plateau Uplift in Southern Africa by Combining Thermochronology, Sediment Flux, Topography, and Landscape Evolution Modeling

et al. 2021

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The southern African Plateau is a dominant feature of African topography reaching heights of >3,000 m, with an average elevation of 1,000 m in the predominantly low relief plateau interior. The elevated margins of the plateau drop through higher relief regions to the coastal plain (Figure 1). However, extensive debate remains regarding when and how it formed. The long wavelength topographic high in absence of collisional tectonism combined with Cretaceous kimberlite activity and a large low shear velocity province (LLSVP) in the deep mantle below southern Africa have led many to suggest uplift related to mantle processes. Given that surface uplift may be related to LLSVP development (e.g., Lithgow-Bertelloni & Silver, 1998), better

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Deep Borehole Lithostratigraphy and Basin Structure of the Southern Karoo Basin Re-Visited

Cited by 8 publications

References 30 publications

Variations in isochore thickness and depositional surface of the Dwyka, Ecca and Beaufort Groups in the Western Cape Province of South Africa as deduced from 2.5D gravity profile models

Variations in isochore thickness and depositional surface of the Dwyka, Ecca and Beaufort Groups in the Western Cape Province of South Africa as deduced from 2.5D gravity profile models

Clinoform architecture and along‐strike facies variability through an exhumed erosional to accretionary basin margin transition

Constraining Plateau Uplift in Southern Africa by Combining Thermochronology, Sediment Flux, Topography, and Landscape Evolution Modeling

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