Upper devonian-lower carboniferous conodont biostratigraphy of the Earn Group and overlying units, northern Canadian Cordillera

Irwin, S E B; Orchard, Michael J.

doi:10.4095/132438

Cited by 9 publications

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“…Age and facies variations in the Earn Group, Glenlyon-Tay River area Detailed mapping of the Glenlyon-Tay River area provides new constraints on the stratigraphy of the Earn Group in central Yukon. Fossils collected for this study add to extensive collections from other parts of Yukon and are consistent with the late Early Devonian to earliest Mississippian age indicated for the Earn Group by previous studies (e.g., Abbott 1983;Irwin and Orchard 1991;Gordey and Anderson 1993;Gordey 2013a). Macrofossils recovered from limited exposures of the lower Earn Group in the study area indicate that this unit is restricted to the Early to Middle Devonian (late Pragian to Givetian; Figs.…”

Section: Discussionsupporting

confidence: 89%

“…However, farther east near the NWT boundary, fossil collections indicate that the Portrait Lake Formation spans the entire Devonian and locally overlaps with the range of conodonts recovered from strata of the Prevost Formation (Fig. 17; Abbott 1983;Irwin and Orchard 1991;Gordey and Anderson 1993). These relationships indicate that at the regional scale formations in the Earn Group, as defined by their lithologic characteristics (Gordey and Anderson 1993), represent in part lateral facies variations rather than simple stratigraphic superposition.…”

Section: Discussionmentioning

confidence: 96%

“…Near the NWT boundary at Macmillian Pass (Fig. 1), conodont collections from the Portrait Lake Formation have ages ranging from late Pragian to early Tournaisian (Abbott 1983;Irwin and Orchard 1991). Barite horizons in the Earn Group between Macmillan Pass and Howard Pass yielded Givetian and Frasnian conodonts (Dawson and Orchard 1982), and an ammonoid found in scree above the Portrait Lake Formation is Frasnian (Gordey et al 1982).…”

Section: Biostratigraphic Constraintsmentioning

confidence: 99%

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Late Devonian magmatism and clastic deposition in the upper Earn Group (central Yukon, Canada) mark the transition from passive to active margin along western Laurentia

et al. 2021

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The Earn Group of central Yukon records the transition from a passive to an active margin along western Laurentia in the Late Devonian. Fine-grained clastic rocks and chert of the lower Earn Group contain late Early to Middle Devonian fossils and were deposited in an offshelf environment. The upper Earn Group comprises a mixture of sandstone and conglomerate, fine-grained siliciclastic rocks, and widespread crystal lithic tuff. Zircon from this succession are precisely dated using CA-ID-TIMS methods on igneous (ca. 363 Ma) and detrital (ca. 378-363 Ma) grains and confirmed by Frasnian to Famennian fossils. Abrupt, along-strike facies changes within the upper Earn Group of the Glenlyon–Tay River area occur across mapped faults that are inferred to have originated as syn-depositional extension faults in the Late Devonian. Occurrences of ca. 363 Ma tuff horizons within all facies of the upper Earn Group provide a temporal correlation across the area. Diorite plutons intrude lower Paleozoic rocks in the area and have U-Pb zircon crystallization dates of ca. 364 Ma. The diorite has calc-alkaline composition consistent with arc magmatism or crustal contamination. The Late Devonian magmatism in the Earn Group is coincident with onset of arc magmatism in the allochthonous Yukon-Tanana terrane, and extension related to rifting and opening of the Slide Mountain ocean in a back-arc setting. Magmatic rocks in the Earn Group of central Yukon thus represent part of a remnant continental arc and back-arc stranded behind the Slide Mountain ocean in the Mississippian.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 96%

Section: Biostratigraphic Constraintsmentioning

confidence: 99%

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Late Devonian magmatism and clastic deposition in the upper Earn Group (central Yukon, Canada) mark the transition from passive to active margin along western Laurentia

et al. 2021

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“…Klapper and Foster Jr. (1993) synonymized Pa. barba Ziegler and Sandberg, 1990 andPa. redana Irwin andOrchard, 1991. The latter is an extreme variant with a spine-like side lobe oriented at < 45°t o the carina and with a reduced posterior carina.…”

Section: Descriptionmentioning

confidence: 99%

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

Saupe

Becker

2022

Palaeobio Palaeoenv

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The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical Frasnian goniatite and conodont zonations, has been restudied in order to document the microfacies development and to refine the conodont stratigraphy around the global semichatovae Event/Transgression, the proposed level to define a future upper Frasnian substage. More than 8.000 platform elements were identified and include new taxa. Palmatolepis jamieae is subdivided into the subspecies Pa. jamieae jamieae, Pa. jamieae savagei n. ssp., Pa. jamieae rosa n. ssp., and Pa. jamieae ssp. δ. Another new species, Pa. adorfensis n. sp., was previously partly identified as Pa. jamieae, while Pa. descendens n. sp. has previously been described in open nomenclature from Inner Mongolia. Morphotypes are defined in Icriodus symmetricus, Pa. ljaschenkoae, and Pa. proversa. A global literature survey shows that the eustatic semichatovae Event can be recognised in more than 20 regions of all continents with (sub)tropical Upper Devonian outcrops. At Martenberg, the transgression is preceded by a thin but distinctive interval with unconformities, microbial mats, sheet cracks, and currents that brought in the regionally youngest volcaniclastics. The new conodont data confirm that no typical Pa. jamieae (sensu the holotype) occur in the two beds originally supposed to represent the jamieae Zone in its reference section. We fully support the conclusion of Ovnatanova and Kononova (2020) that the jamieae Zone should be abandoned. Early Pa. jamieae subspecies and the related new taxa enter at Martenberg and in a few other regions in the globally easily recognisable Frasnian Zone 10 (= plana Zone). Frasnian Zone 11 (feisti Zone) is subdivided into subzones FZ 11a (= feisti Subzone) and FZ 11b (= nasuta Subzone). The base of the latter coincides with the semichatovae Transgression, the semichatovae Subzone of more shallow shelf settings, and is proposed to define in future the upper Frasnian substage base. On a global scale, the Martenberg section is currently the best bed-by-bed documented section for facies changes, conodont and goniatite biostratigraphy at the middle/upper Frasnian transition. Therefore, it is a prime candidate for a future GSSP selection. A global literature survey identified more than 20 other pelagic conodont successions that have the potential for precise correlation and a better understanding of the environmental changes associated with the semichatovae Event.

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Open system sulphate reduction in a diagenetic environment – Isotopic analysis of barite (δ34S and δ18O) and pyrite (δ34S) from the Tom and Jason Late Devonian Zn–Pb–Ba deposits, Selwyn Basin, Canada

Magnall

Gleeson

Stern

et al. 2016

Geochimica et Cosmochimica Acta

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Upper devonian-lower carboniferous conodont biostratigraphy of the Earn Group and overlying units, northern Canadian Cordillera

Cited by 9 publications

References 0 publications

Late Devonian magmatism and clastic deposition in the upper Earn Group (central Yukon, Canada) mark the transition from passive to active margin along western Laurentia

Late Devonian magmatism and clastic deposition in the upper Earn Group (central Yukon, Canada) mark the transition from passive to active margin along western Laurentia

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

Open system sulphate reduction in a diagenetic environment – Isotopic analysis of barite (δ34S and δ18O) and pyrite (δ34S) from the Tom and Jason Late Devonian Zn–Pb–Ba deposits, Selwyn Basin, Canada

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