Deep incision in an Aptian carbonate succession indicates major sea‐level fall in the Cretaceous

Bover‐Arnal, Telm; Salas, R.; Guimerà, Joan; Moreno‐Bedmar, Josep Anton

doi:10.1111/sed.12105

Cited by 41 publications

(23 citation statements)

References 116 publications

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“…This present model continues earlier studies by Broughton (2013aBroughton ( , 2015 proposes that fluvio-estuarine point bars accumulated along deeply incised valleys that resulted from sealevel drops followed by rapid rebounds possibly linked to a Late Aptian global sea-level fall (sensu Maurer et al 2013;Bover-Arnal et. al.…”

supporting

confidence: 91%

Alignment of fluvio-tidal point bars in the middle McMurray Formation: implications for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, northern Alberta

Broughton

2016

Can. J. Earth Sci.

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The northern Athabasca Oil Sands Deposit accumulated on sub-Cretaceous structure partially configured by multistage pre-Cretaceous salt dissolutions in Prairie Evaporite (Middle Devonian) substrate that continued concurrent with deposition of McMurray Formation (Aptian) strata. Dissolution fronts only 250 m below advanced along NW- and NE-oriented fracture–fault lineaments that coalesced into larger salt removal areas. This structural grain was transmitted to the overlying dissected Upper Devonian karst topography draped by lower McMurray braided rivers along a lattice-like channel network. The dominant NW structural grain continued during middle McMurray deposition, with fluvial-estuarine point bars aligned along subparallel tidal channels. Regional salt removal fronts concurrent with middle McMurray deposition migrated north of the Bitumount Trough, resulting in the 200 km2 central collapse. The northern Athabasca Deposit area was configured as a funnel-shaped lower estuary structure consisting of aligned Upper Devonian – lower McMurray fault block terraces that stepped down northward into the central collapse. Sinuous river channels of the upper estuary, constrained along stable substrate of the main paleovalley, flowed northward onto the unstable floor of this funnel-form lower estuary. The main paleovalley fairway branched into multiple tens of kilometres long subparallel fluvio-estuarine tidal channels aligned parallel to the NW structural grain. Sand transport fairways cascaded over the step-down terraces and permitted aggradations of overlying fluvio-tidal point bars to accumulate into giant commercially attractive sand complexes. The internal architecture of these tens of metres thick sand deposits included deposit-wide erosion surfaces resulting from cycles of collapse–subsidence, stabilized substrate and erosion, and renewed subsidence and aggradation.

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supporting

confidence: 91%

Alignment of fluvio-tidal point bars in the middle McMurray Formation: implications for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, northern Alberta

Broughton

2016

Can. J. Earth Sci.

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“…The existence of an incised valley system at the top of the Shu'aiba Formation at the Alshaheen field, offshore Qatar, has been recorded by high resolution seismic and horizontal drilling (Raven et al, 2010). A similar incised valley system in Aptian carbonates has also been reported from the Maestrat Basin, Iberia (Bover-Arenal et al, 2014).…”

Section: Erosional Featuressupporting

confidence: 79%

Characterization of the Late Aptian Top‐dariyan Disconformity Surface Offshore Sw Iran: A Multi‐proxy Approach

Naderi-Khujin

Seyrafian

Vaziri‐Moghaddam

et al. 2016

Journal of Petroleum Geology

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The late Aptian disconformity at the top of the carbonate‐dominated Dariyan Formation is a regional‐scale surface recognised throughout SW Iran and adjacent areas to the south. This study investigates the disconformity using wireline logs, petrographic analyses, SEM observations, and CL and stable isotope data from an oilfield offshore SW Iran. The top‐Dariyan surface in the studied field is characterised by erosional incisions and clastic‐filled fissures which, together with secondary porosity in the underlying carbonates, uranium enrichment and meteoric infill cements, are interpreted as subaerial exposure‐related features. The clastic‐filled fissures were identified from gamma‐ray logs in horizontal wells, and infill material is composed of argillaceous carbonates, clays, quartz and iron‐bearing minerals. The correlation of GR logs in 19 vertical wells resulted in the recognition of erosional incisions (up to about 16 m deep) on the top‐Dariyan surface, together with thickening of siliciclastic sediments in the overlying basal part of the Kazhdumi Formation. Back‐filled sediments in erosional incisions may form potential exploration targets. Secondary porosity in the uppermost 20 m of the Dariyan Formation was created by meteoric processes during subaerial exposure. Cathodoluminescence microscopy of diagenetic cements, carbon and oxygen isotope data and elemental analyses were used to reconstruct the diagenetic history of the carbonates in the Upper Dariyan interval.

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“…Possible Aptian sea-level fluctuation is recognized by some researchers (Bover-Arnal et al 2014), but this did not necessarily result in the deep channel incisions that dissect the McMurray deposits. This model interprets middle and upper interval strata as a succession of parasequences that prograded northward across a relatively stable and low relief deltaic coastal plain.…”

Section: Tectono-stratigraphic Modelsmentioning

confidence: 98%

Syndepositional architecture of the northern Athabasca Oil Sands Deposit, northeastern Alberta

Broughton

2015

Can. J. Earth Sci.

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Salt dissolution collapse-subsidence is proposed as the dominant tectono-stratigraphic control on the deposition of major sand trends across the northern Athabasca Oil Sands Deposit. Salt removal along linear dissolution trends 200 m below in the Prairie Evaporite (Middle Devonian) halite beds resulted in the collapse of the overlying Upper Devonian strata. The collapse-induced differential subsidence of the fault blocks formed the floor underlying the McMurray deposits in the 50 km long V-shaped Bitumount Trough extending across the northern area of the Athabasca Oil Sands Deposit. The lower and middle-upper McMurray sand trends filled the accommodation created by collapses of a linear chain of Upper Devonian fault blocks along the northern margin of the western Trough. A pair of tens-of-metres thick and 20-30 km long sand trends developed parallel in overlying accumulations of the lower and middle-upper McMurray Formation (Aptian). This half-graben tilted northward as the dissolution trend in the underlying Prairie Evaporite salt scarp widened, and the scarp margin was deeply embayed. Salt dissolution-induced structures were the principal control that located the large sand complexes exploited by bitumen mining projects. Earlier models of McMurray architecture interpreted the underlying karst collapse to have been largely pre-Cretaceous. This new architectural model reinterprets the spatiotemporal balance between erosion at the pre-Cretaceous surface and within the buried salt beds. Extensive salt removal resulted in collapse of the underlying hypogene karst during the late Aptian age. This resulted in the over-thickened multi-kilometres long McMurray sand trends. The underlying karst collapse resulted in unstable deposition surfaces along the sub-Cretaceous trough floors. This tectono-stratigraphic architecture, called the syndepositional model in this study, is proposed as an alternative to two other models, one of which proposes that deeply incised channel valleys and fills resulted from multiple significant sea-level fluctuations, while the other proposes that stacked parasequences accumulated along overlying shallow channels that meandered across a stable fluvio-estuarine coast.Résumé : La dissolution de sel causant la subsidence / l'effondrement est proposée en tant que le contrôle tectonique / stratigraphique dominant de la tendance de la déposition du sable à travers le secteur nord du gisement des sables bitumineux de l'Athabasca. Le retrait du sel le long de tendances de dissolution linéaires à 200 m plus bas dans les lits de halite Prairie Evaporite (Dévonien moyen) a causé l'effondrement des strates du Dévonien supérieur qui se trouvaient au-dessus. La subsidence différentielle, engendrée par l'effondrement de blocs de faille, a formé le plancher sous les gisements McMurray dans la fosse Bitmount, laquelle a une longueur de 50 km et une forme en V. Cette fosse s'étend à travers le secteur nord du gisement de sables bitumineux de l'Athabasca. Les tendances de sable inférieures et moyennes-supérieures...

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Deep incision in an Aptian carbonate succession indicates major sea‐level fall in the Cretaceous

Cited by 41 publications

References 116 publications

Alignment of fluvio-tidal point bars in the middle McMurray Formation: implications for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, northern Alberta

Alignment of fluvio-tidal point bars in the middle McMurray Formation: implications for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, northern Alberta

Characterization of the Late Aptian Top‐dariyan Disconformity Surface Offshore Sw Iran: A Multi‐proxy Approach

Syndepositional architecture of the northern Athabasca Oil Sands Deposit, northeastern Alberta

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