Flysch and quartzite, Kandik Group and equivalents

Unit symbol: Kkg
Age range Lower Cretaceous, Albian to Valanginian (145 to 100.5 Ma)
Lithology: Sedimentary
Group name: Flysch and quartzite, Kandik Group and equivalents
Kandik Group consists of the Keenan Quartzite, Biederman Argillite, and Kathul Graywacke in the Charley River quadrangle of east-central Alaska. Keenan Quartzite (Brabb, 1969) is medium-gray, white-weathering, massive, resistant, ridge-forming quartzite and sandstone containing a few interbeds of dark-gray siltstone and argillite. Thickness varies from 30 to 300 m and it locally contains abundant Buchia sublaevis of Valanginian age. Biederman Argillite (Brabb, 1969) is at least 1,500 m thick, rhythmically interbedded, dark-gray argillite and medium-gray, quartz arenaceous, carbonate-cemented siltstone and sandstone. Includes a few beds of chert-pebble conglomerate, siliceous shale, chert-limestone breccia and limestone. Convolute structures and cross-laminations are common. Contains very few pelecypods of Valanginian age near base. Kathul Graywacke (Brabb, 1969) consists of several thousand feet dark-greenish-gray, feldspathic graywacke, conglomerate, and dark-gray argillite and minor olive-gray shale and mudstone. Conglomerate clasts include chert, volcanic rocks, argillite, and sandstone in a matrix of graywacke or argillite. Contains a few stratigraphically long-ranging marine pelecypods. May be correlative with nonmarine rocks in Eagle quadrangle that contains plants of probable Albian age. Unit includes Wilber Creek unit of Weber and others (1992) in the Livengood quadrangle, which consists of interlayered siltstone, shale, sandstone, and conglomerate originally subdivided into coarse- and fine-grained units in the Livengood quadrangle. Siltstone and sandstone are medium- to medium-dark-gray and greenish-gray, moderately sorted, and very fine- to medium-grained. Conglomerate is dark-olive-gray to medium-dark-gray, iron-stained, polymictic, unsorted, subangular to well rounded, and grain size ranges from granules to cobbles. Clasts are of local derivation and consist of quartzite, limestone, mafic and felsic igneous rocks, greenstone, diorite and other intrusive rocks, sandstone, siltstone, phyllite, chert, rare grit, shale rip-ups, and very rare carbonatite. Beds are typically internally massive, thick- to medium-bedded, graded, and amalgamated and have planar tops and bases. Local small-scale trough-crossbeds internally fill large-scale troughs and fining-upward cycles are common. Conglomeratic graywacke occurs within lenses in unit. Minor small-scale scour fills locally fine upward into ripple-laminated medium-gray to black siltstone and dark-gray to black shale. Presence of Paragastroplites flexicostatus indicates an Albian age. Graywacke rich in volcanic detritus is locally characteristic of the Kathul Graywacke (Dover and Miyaoka, 1988). Wolverine quartzite of Weber and others (1992), which is exposed in the Livengood, western Circle, and eastern Tanana quadrangles, is light- to dark-gray, very fine- to medium-grained, well-sorted quartzite that contains interbedded black to dark-gray shale and medium-light- to medium-gray siltstone. Rare coquina-like beds contain poorly preserved fragments of Buchia and other fossils that provide limited age control. Includes Vrain unit of Weber and others (1992), which consists of dark-gray to black, pyritiferous shaly slate, or black fissile shale and minor medium- to dark-gray, olive- or greenish-gray siltstone. Closely resembles upper part of the Glenn Shale in the Charley River quadrangle, which is also included here. Upper part of Glenn Shale is a carbonaceous shale that contains minor thin beds (up to 5 m thick) of fine-grained sandstone. Early Cretaceous megafossils have been collected from several localities within the unit (Miyaoka, 1990). The Wilber Creek, Wolverine quartzite, and Vrain units are thought to be offset from the Kandik Group along the Tintina Fault System

Source map information

Source map Foster, H.L., 1992, Geologic map of the eastern Yukon-Tanana region, Alaska: U.S. Geological Survey Open-File Report 92-313, 26 p., 1 plate, scale 1:500,000.
Symbol Mza
Unit name Argillite
Description Dark grayish black carbonaceous argillite. Unit may include other rocks types but is incompletely mapped because of heavy vegetation cover. Age unknown, but may be equivalent to Glenn Shale
Lithology Metamorphic

Correlated geologic units

Label KJgu
Description Glenn Shale, upper unit, Early Cretaceous to Middle Jurassic
Geologic age Jurassic to Early-Cretaceous
Geologic setting Sedimentary, deltaic-and-nearshore
Lithology Form Importance
Shale < Mudstone < Clastic < Sedimentary Carbonaceous Indeterminate, major
Sandstone < Clastic < Sedimentary Bed Minor
Siltstone < Clastic < Sedimentary Bed Minor