Coals peripheral to opening and closure of the northern Western Interior Seaway: depositional signatures recording interplay between Milankovitch orbital forcing and salt dissolution collapse-subsidence structures with responsiveness to craton deformation and eustatic sea-level

Broughton, Paul L.

doi:10.1007/s13146-021-00679-9

Cited by 3 publications

(3 citation statements)

References 118 publications

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“…The uppermost interval of the lower McMurray Formation accumulated extensive paralic peat mires, now represented by a nearly continuous interval of 3-5 m thick lignite. The coals thicken to as much as 20-25 m within salt dissolution-collapse sinkholes and along sinkhole valleys distributed across the northern area of the Athabasca Oil Sands deposit (Broughton, 2013(Broughton, , 2015(Broughton, , 2021Rinke-Hardekopf et al, 2019, 2021.…”

Section: Mcmurray Formation Stratigraphymentioning

confidence: 99%

“…The depositional environment of the McMurray Formation changed with the onset of tidal influenced deposits of the middle interval and, resulted in a disconformable contact with fluvial and lacustrine deposits of the lower interval (Durkin et al, 2017;Hein et al, 2000Hein et al, , 2001Hein et al, , 2013. Middle and upper interval deposits accumulated proximal to the now eroded shoreline of the southward advance of the Boreal Sea along the northern reaches of a continental-scale river system that extended across the interior of the North American craton (Benyon et al, 2014(Benyon et al, , 2016Fustic et al, 2021;Rinke-Hardekopf et al, 2019, 2021. The middle interval strata include an extensive distribution of multi-kilometre long and 10-40 m thick point bars (Broughton, 2015(Broughton, , 2016Hein et al, 2013).…”

Section: Mcmurray Formation Stratigraphymentioning

confidence: 99%

“…This flow migrated to the level of the lake bottom sediment below, an anoxic lacustrine depositional site associated with the pervasive peat mire terrain. (Broughton, 2021; Rinke‐Hardekopf et al, 2019). This microbial redox depositional environment resulted in siderite precipitation as densely packed spherulites.…”

Section: Interpretation and Depositional Modelmentioning

confidence: 99%

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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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Section: Mcmurray Formation Stratigraphymentioning

confidence: 99%

Section: Mcmurray Formation Stratigraphymentioning

confidence: 99%

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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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Astronomical forcing in the coal-bearing Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China

Tang,

Zhang,

Zhou

et al. 2023

Ore Geology Reviews

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Migrations of Devonian brine up-section and the origin of calcite-cemented sand in the Lower Cretaceous McMurray Formation, Athabasca Oil Sands

Broughton

2022

Can. J. Earth Sci.

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Calcite-cemented sand intervals are widely distributed in the lower interval of the McMurray Formation of the Lower Cretaceous Athabasca Oil Sands deposit, northeastern Alberta. Flows of Devonian brine were driven up-section upon mixture with meteoric-charged groundwater that came in contact with the Prairie Evaporite Formation only 200 m below. Voluminous migrations of carbonate-saturated Devonian formation water during lower McMurray Formation deposition account for the distribution of decimetre to multi-metre thick calcite-cemented sand intervals and giant concretions within the syndepositional fill of the Bitumount Trough, a 100 km long salt dissolution-collapse structure that floored the northern Athabasca Oil Sands deposit. Precipitations of calcite cement concurrent with deposition of the lower McMurray Formation provide insight into the eventual disposition of the voluminous brine that would have resulted from the dissolution of as much as 130 m of Middle Devonian salt section below the Bitumount Trough in contrast to deep basin storage elsewhere. Breccia pipes developed in Middle-Upper Devonian carbonate beds flooring the Bitumount Trough provided migration pathways up-section for the carbonate-saturated Devonian brines. Giant concretions of calcite-cemented sand, 1-2 m across, developed in homogeneous sands proximal to collapse-breccia pipes that vent along the Trough floor, whereas brine flows directed along heterogeneous sands resulted in tabular calcite-cemented beds. Similar but volumetrically less significant Quaternary brine migrations diluted with glacial meltwater were discharged at the surface as saline springs along the modern river valleys, resulting in geochemical trends characterized by concentration of total dissolved solids but without associated precipitations of calcite cement.

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Coals peripheral to opening and closure of the northern Western Interior Seaway: depositional signatures recording interplay between Milankovitch orbital forcing and salt dissolution collapse-subsidence structures with responsiveness to craton deformation and eustatic sea-level

Cited by 3 publications

References 118 publications

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

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

Astronomical forcing in the coal-bearing Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China

Migrations of Devonian brine up-section and the origin of calcite-cemented sand in the Lower Cretaceous McMurray Formation, Athabasca Oil Sands

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