Short Notes on Alaskan Geology 1991

doi:10.14509/2291

Cited by 4 publications

(6 citation statements)

References 19 publications

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“…2) consists of Lower-Middle Devonian platform facies of the Nixon Fork that overstepped older Dillinger basinal facies (Dumoulin et al, 2000). Upper Devonian carbonate and siliciclastic rocks overlie older Devonian strata in areas C through F (Reed and Nelson, 1980;Gilbert, 1981;Bundtzen and Gilbert, 1991;Bundtzen et al, 1994Bundtzen et al, , 1997 and include distinctive minerals such as barite and phosphate that typically form in highly productive oceanographic settings. Rare shallow-water carbonate rocks of Mississippian, Pennsylvanian, Permian, and Triassic ages are found chiefly on and adjacent to the Nixon Fork platform (areas A through C, western area D; Patton et al, 1980;McRoberts and Blodgett, 2002;Gilbert, 1981;Bundtzen et al, 1994).…”

Section: Stratigraphy Of the Mystic Subterranementioning

confidence: 99%

“…3). These strata make up map units Ds and Dcs in the northern Lime Hills quadrangle (Gilbert et al, 1990;Bundtzen and Gilbert, 1991), part of the lower Sheep Creek Formation in the McGrath quadrangle (Bundtzen et al, 1997), and an interval in the lower part of map unit Pzus in the Talkeetna quadrangle (Reed and Nelson, 1980). Lithologies include dark gray to black shale, siltstone, and varicolored chert.…”

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

“…1, Fig. 4) includes an interval of bedded barite ~50 m thick (Gagaryah deposit; Bundtzen and Gilbert, 1991). Barite textures range from massive to laminated to nodular (Figs.…”

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

“…5A-5D). Frasnian (early Late Devonian) brachiopods have been identified in silty sandstone 50-60 m stratigraphically above the deposit (Gilbert et al, 1990;Bundtzen and Gilbert, 1991).…”

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

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The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska

et al. 2018

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The youngest part of the Farewell terrane in interior Alaska (USA) is the enigmatic Devonian-Cretaceous Mystic subterrane. New U-Pb detrital zircon, fossil, geochemical, neodymium isotopic, and petrographic data illuminate the origin of the rocks of this subterrane. The Devonian-Permian Sheep Creek Formation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability peaks between ca. 460 and 405 Ma, and overall age spectra like those from the underlying Dillinger subterrane. Samples are sandstones rich in sedimentary lithic clasts, and differ from approximately coeval strata to the east that have abundant volcanic lithic clasts and late Paleozoic detrital zircons. The Permian Mount Dall conglomerate has mainly carbonate and chert clasts and yielded youngest detrital zircons of latest Pennsylvanian age. Permian quartz-carbonate sandstone in the northern Farewell terrane yielded abundant middle to late Permian detrital zircons. Late Triassic-Early Jurassic mafic igneous rocks occur in the central and eastern Mystic subterrane. New whole-rock geochemical and isotopic data indicate that magmas were rift related and derived from subcontinental mantle. Triassic and Jurassic strata have detrital zircon age spectra much like those of the Sheep Creek Formation, with major age populations between ca. 430 and 410 Ma. These rocks include conglomerate with clasts of carbonate ± chert and youngest detrital zircons of Late Triassic age and quartz-carbonate sandstone with youngest detrital zircons of Early Jurassic age. Lithofacies indicating highly productive oceanographic conditions (upwelling?) bracket the main part of the Mystic succession: Upper Devonian bedded barite and phosphatic Upper Devonian and Lower Jurassic rocks. The youngest part of the Mystic subterrane consists of Lower Cretaceous (Valanginian-Aptian) limestone, calcareous sandstone, and related strata. These rocks are partly coeval with the oldest parts of the Kahiltna assemblage, an overlap succession exposed along the southern margin of the Farewell terrane. Our findings support previous models suggesting that the Farewell terrane was proximal to the Alexander-Wrangellia-Peninsular composite terrane during the late Paleozoic, and further suggest that such proximity continued into (or recurred during) the Late Triassic-Early Jurassic. But middle to late Permian detrital zircons in northern Farewell require another source; the Yukon-Tanana terrane is one possibility.

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Section: Stratigraphy Of the Mystic Subterranementioning

confidence: 99%

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

“…1, Fig. 4) includes an interval of bedded barite ~50 m thick (Gagaryah deposit; Bundtzen and Gilbert, 1991). Barite textures range from massive to laminated to nodular (Figs.…”

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

“…5A-5D). Frasnian (early Late Devonian) brachiopods have been identified in silty sandstone 50-60 m stratigraphically above the deposit (Gilbert et al, 1990;Bundtzen and Gilbert, 1991).…”

Section: Middle-upper Devonian Stratamentioning

confidence: 99%

See 2 more Smart Citations

The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska

et al. 2018

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show abstract

“…Instead, shallow-water carbonate rocks and limestone turbidites make up most of the Devonian section in the Farewell terrane, along with subordinate heterolithic sandstones. Upper Devonian strata in the Mystic subterrane have features indicating a high-productivity setting, such as phosphatic nodules and sedimentary barite deposits (Reed and Nelson, 1980;Bundtzen and Gilbert, 1991;Dumoulin et al, 2014b); these distinctive deposits have no counterparts in the Alexander terrane or Arctic Alaska.…”

Section: Silurian-devonianmentioning

confidence: 99%