Thin-Bedded Turbidites of the Tanqua Karoo&lt;subtitle&gt;Physical and Depositional Characteristics&lt;/subtitle&gt;

Basu, Debnath; Bouma, Arnold H.

doi:10.1306/m72703c23

Cited by 4 publications

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“…Low N:G environments are more difficult to study than their proximal counterparts due to the increase in abundance of thin beds (3-10 cm thick) which, in turn, commonly create poorly exposed outcrops where primary sedimentary structures are difficult to discern. Nevertheless, event bed-scale reservoir heterogeneity in distal environments is well below the resolution of most standard logging tools (Basu & Bouma, 2000) and typical seismic data, making detailed outcrop studies the only way to quantify thin-bedded, submarine lobe deposits. Borehole data (e.g.…”

Section: Total Sand Low Highmentioning

confidence: 99%

“…Nevertheless, event bed‐scale reservoir heterogeneity in distal environments is well below the resolution of most standard logging tools (Basu & Bouma, 2000) and typical seismic data, making detailed outcrop studies the only way to quantify thin‐bedded, submarine lobe deposits. Borehole data (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…core, logs) are the highest resolution data available from an industry perspective, but they only provide a one‐dimensional view of a three‐dimensional problem. Despite the increased importance of thin‐bedded submarine deposits as hydrocarbon reservoirs (Basu & Bouma, 2000; Stow et al, 1990), very few studies have both performed outcrop‐based correlations at the event bed scale (Fonnesu et al, 2015, 2018; Marini et al, 2015) and compiled quantitative information on the lateral thickness variability of turbidite deposits (Clark, 1998; Fryer & Jobe, 2019; Tökés & Patacci, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the lateral heterogeneity of distal submarine lobe deposits, Point Loma Formation, California: Implications for subsurface lateral facies prediction

Kus

2021

The Depositional Record

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Section: Total Sand Low Highmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantifying the lateral heterogeneity of distal submarine lobe deposits, Point Loma Formation, California: Implications for subsurface lateral facies prediction

Kus

2021

The Depositional Record

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Anatomy, geometry and sequence stratigraphy of basin floor to slope turbidite systems, Tanqua Karoo, South Africa

et al. 2001

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The Tanqua area of the Karoo basin, South Africa, contains five Permian deep‐water turbidite fan systems, almost completely exposed over some 640 km2. Reconstruction of the basin‐fill and fan distributions indicates a progradational trend in the 450 m+ thick succession, from distal basin floor (fan 1) through basin‐floor subenvironments (fans 2, 3 and 4) to a slope setting (fan 5). Fans are up to 65 m thick with gradational to sharp bases and tops. Facies associations include basin plain claystone and distal turbidite siltstone/claystone and a range of fine‐grained sandstone associations, including low‐ and high‐density turbidite current deposits and proportionally minor debris/slurry flows. Architectural elements include sheets of amalgamated and layered styles and channels of five types. Each fan is interpreted as a low‐frequency lowstand systems tract with the shaly interfan intervals representing transgressive and highstand systems tracts. All fans show complex internal facies distributions but exhibit a high‐frequency internal stratigraphy based on fan‐wide zones of relative sediment starvation. These zones are interpreted as transgressive and highstand systems tracts of higher order sequences. Sandy packages between these fine‐grained intervals are interpreted as high‐frequency lowstand systems tracts and exhibit dominantly progradational stacking patterns, resulting in subtle downdip clinoform geometries. Bases of fans and intrafan packages are interpreted as low‐ and high‐frequency sequence boundaries respectively. Facies juxtapositions across these sequence boundaries are variable and may be gradational, sharp or erosive. In all cases, criteria for a basinward shift of facies are met, but there is no standard ‘motif’ for sequence boundaries in this system. High‐frequency sequences represent the dominant mechanism of active fan growth in the Tanqua deep‐water system.

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Lithostratigraphy and palaeoenvironments of the Cambrian in SW Wales

Rees

Thomas

Lewis

et al. 2014

Memoirs

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The classic Cambrian succession of SW Wales comprises a succession of clastic rocks some 1250 m thick that make up part of the Dyfed Supergroup. The existing lithostratigraphical framework owes much to the Nineteenth Century researchers, with relatively little detailed work having been published since. We here present a detailed, rationalized and revised lithostratigraphy for the Cambrian part of the Dyfed Supergroup of the area. Where possible and appropriate, we have retained original and well-known names for formations and other units in harmony with current usage. However, the recognition of four lithostratigraphical groups is overly complex and sometimes unworkable, and a two-fold subdivision is proposed instead. The Caerfai and much of the Lower and Middle Solva groups of earlier usage comprise conglomerates, pebbly sandstones and brightly coloured fine- to coarse-grained sandstones: all are here combined into a revised Caerfai Group. By excluding the silt-dominated Upper Solva division, the Caerfai Group is readily divided into lower and upper parts comprising conglomerates and/or pebbly sandstones, with sandstones and siltstones dominant in between. These rocks comprise the Ogof Golchfa (new), St Non's, Caerfai Bay, Caer Bwdy Bay, Newgale (new) and Porth Clais (new) formations. The following members (all new) are recognized within the Newgale Formation: the Trwyncynddeiriog, Pen-y-Cyfrwy and Cwm Mawr members. Ichnofossils from the upper part of the Ogof Golchfa Formation suggest that Cambrian deposition in the area began in Unnamed Cambrian Series 2 (C2) times. Body fossils and radiometric dating show that the Caerfai Bay to Porth Clais formations span the interval from Cambrian Series 2, Unnamed Cambrian Stage 3 (such stages are denoted by CS3, CS4 etc. below), probably to the Ptychagnostus gibbus Biozone (CS5). The former Upper Solva Group, Menevian Group and Lingula Flags comprise the newly erected Porth-y-rhaw Group, a 687 m-thick unit of fine sandstones, siltstones and mudstones, within which a further five formations are recognized. These are the Whitesands Bay, Menevia, Aber Llong (all new), Ogof Velvet (revised) and Treffgarne Bridge formations. The Porth-y-rhaw Group spans the Tomagnostus fissus Biozone (C3, Drumian) to the Olenus cataractes Biosubzone (Furongian, Paibian). The overall two-fold subdivision of the Cambrian part of the Dyfed Supergroup in the area accords broadly with the first lithostratigraphical scheme proposed for the area, and is comparable with the separation of the Harlech Grits and Mawddach groups in northern and central Wales.The oldest part of the Caerfai Group formed in a tectonically active context and records a transition from alluvial fan deposits, through braided stream environments, into transgressive nearshore marine sandstones. These sediments were derived from the west, and as well as locally-sourced material, include lithic clasts and grains derived from a presumed southwestwards extension of the Monian Composite Terrane. Above lie sedimentary deposits formed under a wide range of conditions, ranging from tidally-influenced to turbidites. Further evidence of active tectonism is found in the easterly-derived fan-delta sedimentary deposits of the higher part of the Caerfai Group and lower part of the Porth-y-rhaw Group. Deposition of the latter began with fine-grained turbidites deposited in a mid–outer shelf setting. These pass up first into hemipelagites, then into sedimentary rocks deposited on a storm-dominated shelf, and finally a very extensive shallow subaqueous delta platform formed in a passive margin setting.

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Thin-Bedded Turbidites of the Tanqua Karoo<subtitle>Physical and Depositional Characteristics</subtitle>

Cited by 4 publications

References 0 publications

Quantifying the lateral heterogeneity of distal submarine lobe deposits, Point Loma Formation, California: Implications for subsurface lateral facies prediction

Quantifying the lateral heterogeneity of distal submarine lobe deposits, Point Loma Formation, California: Implications for subsurface lateral facies prediction

Anatomy, geometry and sequence stratigraphy of basin floor to slope turbidite systems, Tanqua Karoo, South Africa

Lithostratigraphy and palaeoenvironments of the Cambrian in SW Wales

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