Devonian salt dissolution-collapse breccias flooring the Cretaceous Athabasca oil sands deposit and development of lower McMurray Formation sinkholes, northern Alberta Basin, Western Canada

Broughton, Paul L.

doi:10.1016/j.sedgeo.2012.11.004

Cited by 69 publications

(139 citation statements)

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“…The northeastern area of the Lower Cretaceous Athabasca Oil Sands Deposit overlies a segment of the 1000 km long and 150 km wide regional salt dissolution trend. Modified from Meijer Drees (1994) and Broughton (2013).…”

Section: Methodsmentioning

confidence: 99%

“…Location of the Bitumount Trough across the southern study area and trace of the regional cross-section B-B' are illustrated. Adapted from Broughton (2013). …”

Section: Fig 2 Geologic Overview Of the Athabasca Oil Sands Depositmentioning

confidence: 99%

“…An earlier study by Broughton (2013) described salt dissolution structuring that fragmented the Upper Devonian strata into troughs that floored the McMurray Formation deposits across the northern Athabasca Oil Sands Deposit (Fig. 3).…”

Section: Introductionmentioning

confidence: 96%

“…Large areas of this pre-Cretaceous paleotopography that were subsequently covered by Lower Cretaceous sands were configured by salt dissolution trends within the Middle Devonian Prairie Evaporite substrate. Episodic salt dissolution events resulted in collapsesubsidence of the overlying 175-250 m thick Upper Devonian strata (Broughton 2013), and reconfigured a rugged sub-Cretaceous karst topography onto which the McMurray Formation sands accumulated. These Devonian salt removal areas underlie the northern one-third of the Athabasca Oil Sands Deposit ( Fig.…”

Section: Introductionmentioning

confidence: 99%

“…It is generally accepted that most of the tens-of-kilometres long, salt dissolution structures were pre-Cretaceous events that configured the sub-Cretaceous paleotopography, and they were catchment lows for subsequent lower McMurray deposits (Hein et al 2001(Hein et al , 2013Ranger and Gingras 2001, 2003, although it is recognized that dissolution along the salt scarp (Fig. 2) continued during the Cretaceous (Broughton 2013(Broughton , 2014Hein et al 2013) and is continuing to the present day (Gibson et al 2013). Generally accepted interpretations of McMurray deposition do not consider salt dissolution-collapse structuring to have continued at any significant regional scale during the Early Cretaceous, or to have resulted in any regional McMurray syndepositional structural trends other than localized sags.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

“…Location of the Bitumount Trough across the southern study area and trace of the regional cross-section B-B' are illustrated. Adapted from Broughton (2013). …”

Section: Fig 2 Geologic Overview Of the Athabasca Oil Sands Depositmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Broughton

2015

Can. J. Earth Sci.

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Special Features Associated with Evaporites

2022

Karst Hydrogeology, Geomorphology and Caves

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Salt dissolution tectonism and origin of lacustrine carbonate beds: Mn‐Fe‐calcite and Mn‐siderite micro‐spherulite fabrics of the Lower Cretaceous McMurray Formation, Athabasca Oil Sands deposit, western Canada

Broughton

2022

The Depositional Record

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Several lacustrine carbonate beds, each a metre-thick interval of densely packed Mn-rich sideritic micro-spherulites or Mn-rich ferroan calcite micro-spherulites, are recorded for the first time within strata of the Lower Cretaceous McMurray Formation of the northern Athabasca Oil Sands deposit, western Canada. A lower McMurray lacustrine carbonate deposit is characterised by a metre-thick bed fabric of Mn-rich siderite micro-spherulites. The middle and upper interval McMurray beds developed fabrics of Mn 2+ -rich ferroan calcite micro-spherulites. These carbonate beds represent saline lacustrine depositional environments that resulted from the lake bottom sediments ingressed from below by Mn 2+ -Fe 2+ -rich carbonate-saturated brines. These up-section migrations of Devonian formation water were sourced from dissolution trends developed in limestone and haliteanhydrite beds of the underlying Devonian Prairie Evaporite during Cordilleran deformation of the Alberta Basin foreland. These brines ascended to the overlying McMurray Formation sediments along dissolution-collapse structures such as breccia pipes, sinkholes and margins of differentially subsided Upper Devonian fault blocks. The up-section migration of a sulphate-saturated Fe 2+ and Mn 2+ -rich brine resulted in the ingress of a lower McMurray lacustrine bottom sediment at a site associated with the development of a peat mire terrain. Microbial redox of the lake bottom sediment resulted in a carbonate bed of micro-spherulitic fabrics of Mn-rich siderite interwoven with pyrite laminae. Subsequent salt dissolution events and up-section migrations of Devonian brine during deposition of the middle and upper McMurray intervals resulted in similar carbonate-saturated but sulphate-poor chemistry. These saline flows also ingressed lacustrine bottom sediments below, and resulted in limestone beds of densely packed spherulitic fabrics of Mn-ferroan calcite, not siderite. These deposits provide insight into largely unknown dispositions of voluminous brine resulting from salt dissolution trends | 657 BROUGHTON How to cite this article: Broughton, P.L. (2022) Salt dissolution tectonism and origin of lacustrine carbonate beds: Mn-Fe-calcite and Mn-siderite micro-spherulite fabrics of the Lower Cretaceous McMurray Formation,

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Devonian salt dissolution-collapse breccias flooring the Cretaceous Athabasca oil sands deposit and development of lower McMurray Formation sinkholes, northern Alberta Basin, Western Canada

Cited by 69 publications

References 29 publications

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

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

Special Features Associated with Evaporites

Salt dissolution tectonism and origin of lacustrine carbonate beds: Mn‐Fe‐calcite and Mn‐siderite micro‐spherulite fabrics of the Lower Cretaceous McMurray Formation, Athabasca Oil Sands deposit, western Canada

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