Geologic map of the Livengood quadrangle, Alaska

Abstract

Qa Alluvium (Holocene) Silt, sand, and granule-to boulder-sized material having minor amounts of organic debris, gray, yellowish-gray to brown, well -sorted and -stratified. Alluvium shows fining-upward cycles. Underlies active stream beds or floodplain, locally frozen in silty channels; includes placer-mine tailings on sections of Quail, Troublesome, Ophir, and Nome Creeks, streams in Livengood village area, and southeast of Chatanika River in Fairbanks mining district; 0.3 m to approximately 15 m thick.Qg Reworked creek gravels in placer mining areas (Holocene) Placer-mine tailings derived from buried stream gravels worked for gold by methods of pick and shovel, mechanized surface, underground drifting, or dredging methods; shown, as map scale permits, on Fairbanks and Livengood Creeks, elsewhere included in Qa. Commonly less than 9 m thick.Qab Abandoned or inactive flood plain deposits (Holocene) Silt, sand, granule-to pebblesize gray gravel, and organic material. Abandoned stream channels 0.6 to 4.5 m topographically higher than active channels of Qa, elsewhere flat to hummocky and many bogs. Includes small alluvial fans, deposited by minor side streams, and intermixed alluvial sediments and very silty natural stream levees from cyclical flooding of Minto Flats.Commonly frozen. As thick as 30 m. QdSand dune deposits (Holocene) Sand, moderate yellowish-brown, well-sorted, eolian. Grains 65 to 85 percent quartz, yellowish-white, clear to opaque, angular to round; dark gray to black rock fragments, chert, mica, traces of feldspar and light-colored rock fragments. Isolated dunes mostly covered by eolian silt and stabilized by vegetation. As thick as 9 m. QsSwamp deposits (Holocene) Humus, peat, and silt in poorly-drained areas having abundant stagnant water; generally frozen below a depth of about a meter; some small swampy areas included in units Qa, Qab, and Qsu. As thick as tens of meters. QafAlluvial fan deposits (Holocene) Sand, gravel, and boulders, gray to brown, poorly-to wellsorted and stratified, coarse-grained, rounded to angular; clasts locally-derived and deposited under high-energy conditions below major decrease in slope. Locally covered by reworked silt and small amount of vegetation. Thickness varies greatly; only largest alluvial fans shown on map. Qsu Silt, undifferentiated, contains reworked loess, swamp and organic-rich deposits (Holocene) Silt, pale yellowish brown, largely eolian, and in part, locally retransported to lower slopes and valley bottoms by alluvial and solifluctional processes. Local brown to grayish black organic rich layers, masses, and disseminated debris. Poorly drained and frozen as abundant horizontal and vertical sheets, wedges, and irregular masses of ground ice. Thickness ranges from 1 to 61 m. QIC Loess and colluvium Including minor upland alluvium (Holocene) Unsorted mixture of local bedrock fragments and loess, light-gray to brown, angular or subrounded; partially frozen, fairly well-drained, locally occurs as mixture of reworked loess and colluvium in drainage chan...

Ordovician sponges from west-central and east-central Alaska and western Yukon Territory, Canada

“…The exposures that contain the conglomeratic beds at Locality 2 were placed questionably in the Dq unit (Quail unit) by Weber et al (1992), and unquestionably in this unit by Weber et al (1994). One of us (Blodgett) now dis-agrees with this unit assignment, as the rocks here at Locality 2 are quite unlike conglomerates of the Late Devonian Quail unit typically exposed to the west in the Livengood B-6 Quadrangle.…”

The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

“…Continued displacement, west of the Tintina fault, on a décollement of this nature, would create a zone of contractional deformation, a fold and thrust belt, at its leading edge in eastern Alaska. In east‐central Alaska, a fold and thrust belt with north to northwest directed thrusts, including the Beaver Creek and White Mountain faults (BC‐WM, Figure ) is interpreted as a western segment of the Mackenzie Mountains fold and thrust belt (Dover, , ; Weber et al, , ). Seismic refraction/wide‐angle reflection data from the U.S. Geological Survey Trans‐Alaska Crustal Transect (Figure ) suggest that the belt is underlain by a NW shallowing (~8‐ to 13‐km deep) décollement (Beaudoin et al, ).…”

Neoproterozoic–early Paleozoic provenance evolution of sedimentary rocks in and adjacent to the Farewell terrane (interior Alaska)

“…1), as defined in Silberling et al (1994), have lithologic and faunal features that suggest ties to the Farewell terrane (Blodgett et al, 2002;Dumoulin et al, 2014a). Lower Paleozoic rocks in the White Mountains terrane comprise a mafic volcanic succession (Ordovician Fossil Creek Volcanics) overlain by shallow-water carbonate strata (Silurian-Devonian Tolovana Limestone; Weber et al, 1992). Partly coeval rocks in the Livengood terrane include the Ordovician Livengood Dome Chert (Weber et al, 1992).…”

“…Lower Paleozoic rocks in the White Mountains terrane comprise a mafic volcanic succession (Ordovician Fossil Creek Volcanics) overlain by shallow-water carbonate strata (Silurian-Devonian Tolovana Limestone; Weber et al, 1992). Partly coeval rocks in the Livengood terrane include the Ordovician Livengood Dome Chert (Weber et al, 1992).…”

“…1 and 14 volcaniclastic conglomerate, with subordinate limestone and feldspathic sandstone, make up the Fossil Creek Volcanics, thought to have formed in an extensional setting along a continental margin Weber et al, 1992). Abundant fossils have been interpreted to indicate an age of early Early Ordovician (Tremadoc) for the lower part of the unit and late Late Ordovician (Ashgill) for the upper beds (Blodgett et al, 1987;Weber et al, 1994); the age of magmatism is uncertain.…”