Phyllite, slate, and black shale

Unit symbol: Dyp
Age range Devonian? (419.2 to 358.9 Ma)
Lithology: Sedimentary
Group name: Clastic and carbonate rocks of the Yukon Flats Basin
Dark-gray to black phyllite and schistose siltstone interbedded with subordinate amounts of quartz wacke and sheared slate- and chert-pebble conglomerate (Brosgé and others, 1973; Brosgé and Reiser, 2000) in northeast Alaska. In the Coleen quadrangle, unit consists of laminated dark-gray, light-gray, and greenish-gray clay and silt phyllite; minor very fine-grained, thin-bedded sandstone Brosgé and Reiser (1969). In the Christian quadrangle, Brosgé and Reiser (2000) subdivided the unit along the East Fork of the Chandalar River; on the east the unit contains more siltstone, is darker-colored, and locally recrystallized. Brosgé and Reiser (2000) assigned the entire unit to the Venetie terrane in the Christian quadrangle, whereas Moore and others (1994) assigned the unit to the slate- and graywacke-bearing Slate Creek terrane of the southern Brooks Range. The rocks in the Beaver quadrangle were assigned to the Slate Creek thrust sheet of the Angayucham-Tozitna terrane by Patton and others (1994a). As shown here, all of the rock units assigned to this map unit are spatially associated with the Angayucham, Tozitna, and Innoko assemblages and Rampart Group units of this map

Source map information

Source map Brosge, W.P., and Reiser, H.N., 2000, Geology of the Christian quadrangle, Alaska: U.S. Geological Survey Open-File Report 00-192, 13 p., 1 sheet, scale 1:250,000.
Symbol Dpm
Unit name Phyllite and metamorphosed sandstone of Venetie Subterrane of Arctic Alaska Terrane
Description WEST OF EAST FORK OF CHANDALAR RIVER: Black phyllite interbedded with schistose sandstone. Phyllite, in zones up to 200 feet (60 m) thick, comprises about half the unit. Schistose sandstone is gray, limonitic, and weathers yellow and brown; most is fine- to medium-grained and thin-bedded EAST OF EAST FORK CHANDALAR RIVER: Black phyllite and siltstone interbedded with schistose sandstone. Minor quartzite. Schistose sandstone is dark-gray, very fine- to medium-grained, thin-bedded, foliated, and locally recrystallized to quartz and muscovite
Lithology Metamorphic

Correlated geologic units

Label Dyp
Description Phyllite, slate or black shale
Geologic age Early-Devonian to Late-Devonian
Geologic setting Metasedimentary, low-grade
Lithology Form Importance
Phyllite < Metaclastic < Metasedimentary < Metamorphic Major
Black-shale < Shale < Mudstone < Clastic < Sedimentary Bed Major
Slate < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major