Geologic Map of Alaska: Older clastic strata of the Porcupine River sequence of Brosgé and Reiser (1969)

Older clastic strata of the Porcupine River sequence of Brosgé and Reiser (1969)

Unit symbol:	Pzpr
Age range	lower Paleozoic (458.4 to 382.7 Ma)
Lithology:	Sedimentary
Group name:	Clastic and carbonate rocks of the Yukon Flats Basin

Light-gray, fine-grained orthoquartzite, pyritic laminated quartzite, quartz-rich siltstone, and olive micaceous shale at least 600 m thick. Also includes brown-weathering, dark-gray, silty micaceous shale and fine-grained, thin-bedded, pale yellow ferruginous sandstone, which are in an uncertain stratigraphic position relative to the quartzite. Unit is highly sheared along the Coleen River (Brosgé and Reiser, 1969). Similar quartzite, calcareous slate, argillite, and phyllite were mapped as part of the Strangle Woman Creek sequence, which is included here as part of units CPxwn and Dyp. No precise age control exists for these rocks, but they are spatially associated with carbonate rocks of Devonian and older age (unit DCkb)

Source map information

Source map	Mull, C.G., and Sonneman, H.S., 1968-1974, Unpublished data
Symbol	LPzpCq
Unit name	Quartzite, quartzitic sandstone, and phyllite
Description	Quartzite, quartzitic sandstone, calcareous schist, schistose sandstone, and phyllite; generally poor exposures in timber-covered hills in southeast corner of quadrangle. Autochthonous/parautochthonous
Lithology	Metamorphic

Correlated geologic units

Label	DCpu
Description	Older strata of the Porcupine River sequence, quartzite; might be equivalent, in part, to Road River Formation graptolitic shale in Yukon
Geologic age	Late-Ordovician to Middle-Devonian
Geologic setting	Sedimentary, marine, shallow to deep association, undivided

Lithology	Form	Importance
Quartzose-sandstone < Sandstone < Clastic < Sedimentary	Bed	Major
Shale < Mudstone < Clastic < Sedimentary	Bed	Minor
Siltstone < Clastic < Sedimentary	Bed	Minor