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Chapter 36 Neoproterozoic glacial record in the Mackenzie Mountains, northern Canadian Cordillera - Photograph supplement

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Title: Chapter 36 Neoproterozoic glacial record in the Mackenzie Mountains, northern Canadian Cordillera - Photograph supplement
Author: Hoffman, Paul F.
Abstract: Companion photographs to the book chapter Hoffman, Paul F. and Halverson, Galen P. 2011. “Neoproterozoic glacial record in the Mackenzie Mountains, northern Canadian Cordillera.” In: Arnaud, E., Halverson, G. P. and Shields-Zhou, G. (eds) The Geological Record of Neoproterozoic Glaciations. Geological Society, London, Memoirs, 36, 397-411.
URI: http://hdl.handle.net/10214/9424
Date: 2011
Rights Holder: The copyright of the photo rests with the author(s) of the chapter or, where stated, the person who took the photo.


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Ch36_Photo_1_Hoffman.jpg 745.7Kb JPEG image Thumbnail Typical section of Windermere Supergroup on the hangingwall of the Plateau Thrust system near Cranswick River (65°07'01"N, 132°24'34"W). Approximately 3 km of Cryogenian and lower Ediacaran strata are shown, including glacigenic strata of the Shezal Formation (Rapitan Group) and the Stelfox Member of the Ice Brook Formation, along with their respective postglacial ‘cap’ carbonates (Photo credit: Paul Hoffman).
Ch36_Photo_2_Hofffman.jpg 680.0Kb JPEG image Thumbnail Massive diamictite and subordinate bedded periglacial facies of the Shezal Formation (Rapitan Group) near Stoneknife River (64°41'50"N, 129°53'31"W). The glacigenic strata are disconformably underlain by thrombolitic limestone of the Copper Cap Formation (Coates Lake Group) and conformably overlain by limestone turbidites of the lower Twitya Formation (Photo credit: Paul Hoffman).
Ch36_Photo_3_Hoffman.jpg 947.9Kb JPEG image Thumbnail Rapitan Group looking northward from the ridge of its type section (Gabrielse et al. 1973) near Hayhook Lake (63°34'10"N, 127°05'09"W). Basinal maroon siltstone of the Sayunei Formation lies disconformably on carbonate of the Copper Cap Formation. Hæmatite jaspilite at the top of the Sayunei Formation is overlain disconformably by mainly massive diamictite of the Shezal Formation. No limestone (‘cap’ carbonate) occurs at the base of the Twitya Formation in this section (Photo credit: Paul Hoffman).
Ch36_Photo_4_Hoffman.jpg 436.4Kb JPEG image Thumbnail Basinal maroon mudstone of the Sayunei Formation (Rapitan Group) near Hayhook Lake (63°34'36"N, 127°04'27"W), with siltstone turbidites and small dolomite lonestones. Eisbacher (1985) inferred this facies to have been deposited in a permanently ice-covered rift basin, implying ice-shelf rather than iceberg rafting of the lonestones (Photo credit: Paul Hoffman).
Ch36_Photo_5_Hoffman.jpg 422.4Kb JPEG image Thumbnail Marinoan glacial record in the upper Windermere Supergroup near Shale Lake (64°31'20"N, 129°29'51"W). The glacial horizon is at the top of the Keele Formation, a mixed carbonate and clastic shelf assemblage. Carbonate-clast diamictite and associated facies (Stelfox Member) are recessive, only a few meters thick and generally covered by pale straw-coloured scree (far ridge) from the conformably overlying postglacial ‘cap’ dolostone (Ravensthroat Formation). The scree darkens where the pale dolostone is conformably overlain by dark-grey limestone (Hayhook Formation), in which sea-floor cement (crystal fans), pseudomorphosed after aragonite, is locally the dominant component. The final 10 cm of the Ravensthroat Formation contains sea-floor barite rosettes, variably calcitized, which are intimately associated with ferruginous peloidal dolostone. The sea-floor barite is conformably overlain by micritic limestone with sea-floor cement (Hayhook Formation). For photos of Ravensthroat and Hayhook formation sedimentary facies, go to Chapter 5 (Photo credit: Paul Hoffman).
Ch36_Photo_6_Hoffman.jpg 944.5Kb JPEG image Thumbnail Marinoan glacial record in the far northern MackenzieMountains near Arctic Red River (64°55'52"N, 131°03'44"W). A thin carbonate-clast diamictite (Stelfox Member) disconformably overlies Keele Formation dolostone. Pale straw-coloured, macro- to micropeloidal dolostone (Ravensthroat Formation) with giant wave ripples is conformably overlain by red shale, greenish and greyish shales with limestone turbidites, and black shale of the Sheepbed Formation. The red-green-grey shale sequence mimics the contemporaneous (basal Ediacaran) sequences in East Greenland (lower Canyon Formation) and northeast Svalbard (lower Dracoisen Formation), but contrasts with the Hayhook Formation to the south in the Mackenzie Mountains (Photo credit: Paul Hoffman).
Ch36_Photo_7_Hoffman.jpg 876.8Kb JPEG image Thumbnail Marinoan glacial record looking northeast (palaeolandward) towards the edge of the Keele platform (“breakaway scarp” of Aitken 1991b) on Stelfox Mountain (63°35'55"N, 127°52'51"W). Polymictic carbonate-clast diamictite (Stelfox Member of the Ice Brook Formation), 28 m thick, is conformably overlain by the Ravensthroat Formation ‘cap’ dolostone and a thick sequence of black shale (Sheepbed Formation). The diamictite disconformably overlies greenish-grey siltstone (Delthore Member of the Ice Brook Formation), not shown, which lacks glacigenic features. The Ravensthroat ‘cap’ dolostone oversteps the palaeoscarp with little change, but the Stelfox diamictite is less than 3 m thick on the far (up) side of the palaeoscarp, where it disconformably overlies carbonate strata of the Keele Formation (Photo credit: Paul Hoffman).
Ch36_Photo_8_Hoffman.jpg 866.5Kb JPEG image Thumbnail Polymictic carbonate-clast diamictite of the Stelfox Member (Ice Brook Formation) on Stelfox Mountain (63°35'45"N, 127°52'59"W). Pale dolostone and dark limestone clasts are derived from the Keele Formation to the northeast, as are the abundant silt and rounded sand-size quartz grains in the diamictite matrix, suggesting that the Keele clastics were unlithified at the time of the Stelfox glaciation. Note preferred (lower left-upper right) orientation of small tabular clasts in palaeohorizontal section (Photo credit: Paul Hoffman).

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