scholarly journals Geologic mapping in the Talkeetna Mountains and Eastern Alaska Range: A story of mineralization and deformation (presentation): Alaska Geological Society Luncheon, February 21, 2017

2017 ◽  
Author(s):  
Evan Twelker
Keyword(s):  
Geologic Mapping ◽  
Alaska Range ◽  
Geological Society ◽  
Talkeetna Mountains

scholarly journals Overview of the new 1:25,000-scale geologic mapping of the McCallum-Slate Creek fault system, Eastern Alaska Range, Alaska

2019 ◽  
Author(s):  
R.J. Gillis ◽  
P.G. Fitzgerald ◽  
K.D. Ridgway ◽  
B.M. Keough ◽  
J.A. Benowitz ◽  
...  
Keyword(s):  
Fault System ◽  
Geologic Mapping ◽  
Alaska Range

There's more Wrangellia - Magnetic characterization of southern Alaska crust

2021 ◽  
Author(s):  
Richard W. Saltus ◽  
Travis Hudson
Keyword(s):  
Lower Jurassic ◽  
Magnetic Potential ◽  
Magnetic Data ◽  
Magnetic Characterization ◽  
Alaska Range ◽  
Volcanic Arc ◽  
South Central ◽  
Fourier Filtering ◽  
Talkeetna Mountains ◽  
Bearing Part

In southern Alaska, Wrangellia-type magnetic crustal character extends from the Talkeetna Mountains southwest through the Alaska Range to the Bristol Bay region. Magnetic data analyses in the Talkeetna Mountains showed that there are mid-crustal differences in the magnetic properties of Wrangellia and the Peninsular terrane. After converting total field magnetic anomaly data to magnetic potential, we applied Fourier filtering techniques to remove magnetic responses from deep and shallow sources. The resulting mid-crustal magnetic characterization delineates the regional magnetic potential domains that correspond to the Wrangellia and Peninsular terranes throughout southern Alaska. These magnetic potential domains show that Wrangellia-type crust extends southwest to the Illiamna Lake region and that it overlaps the mapped Peninsular terrane. Upon reconsidering geologic ties between Wrangellia, Peninsular, and Alexander terranes we conclude that Peninsular terrane is part of what we here call Western Wrangellia. Western Wrangellia contains the Lower Jurassic Talkeetna volcanic arc and is similar to Wrangellia of the Vancouver Island area, Canada (Southern Wrangellia) which contains the Lower Jurassic Bonanza volcanic arc. Others have previously made this correlation and proposed that the Talkeetna arc-bearing part of southern Alaska was displaced from the Bonanza arc-bearing part of Canada. We generally agree and propose that about 1000 km of dextral displacement along ancestral Border Ranges fault segments and other faults of south-central Alaska separated Western Wrangellia from Southern Wrangellia. We think this displacement was mostly in the Late Jurassic and earliest Cretaceous, perhaps between about 160 and 130 Ma.

Clyde Wahrhaftig and Allan Cox (1959) Rock glaciers in the Alaska Range. Bulletin of the Geological Society of America 70(4): 383–436

2013 ◽  
Vol 37 (1) ◽  
pp. 130-139 ◽  
Author(s):  
Melanie Stine
Keyword(s):  
20Th Century ◽  
High Elevation ◽  
Rock Glacier ◽  
Alaska Range ◽  
Geological Society ◽  
Geomorphic Features ◽  
Rock Glaciers ◽  
Firm Basis ◽  
Scientific Attention ◽  
Geomorphic Processes

Rock glaciers are one of the most prominent geomorphic features in high-elevation areas and affect numerous hydrologic, ecologic, and geomorphic processes. However, little scientific attention was focused on rock glaciers during the first part of the 20th century. In 1959, Clyde Wahrhaftig and Allan Cox published a paper titled ‘Rock glaciers in the Alaska Range’, which initiated worldwide interest in these features and a subsequent surge of publications addressing rock glaciers. Wahrhaftig and Cox (1959) provided a detailed and encompassing study on rock glacier features, origins, classifications, relations to climate, movement, and composition. Their data and descriptions established a firm basis for further advancement of rock glacier research. This paper aims to assess the influence that Wahrhaftig and Cox (1959) had on subsequent publications and studies of rock glaciers.

scholarly journals Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology

Geosphere ◽  
2020 ◽  
Author(s):  
James V. Jones ◽  
Erin Todd ◽  
Stephen E. Box ◽  
Peter J. Haeussler ◽  
Christopher S. Holm-Denoma ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Geologic Mapping ◽  
Localized Deformation ◽  
Alaska Range ◽  
South Central ◽  
Wrangellia Terrane ◽  
Terrane Accretion ◽  
Latest Eocene ◽  
Slab Window

New U-Pb and 40Ar/39Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Farewell terrane, Triassic and Jurassic plutonic and volcanic rocks of the Peninsular terrane, and Jurassic and Cretaceous siliciclastic strata of the Kahiltna assemblage. Plutonic rocks of different ages also host economic mineralization including intrusion-related Au, porphyry Cu-Mo-Au, polymetallic veins and skarns, and peralkaline intrusion-related rare-earth elements. The oldest intrusive suites were emplaced ca. 104–80 Ma into the Peninsular terrane only prior to final accretion. Deformation of the northern Kahiltna succession and underlying Farewell terrane occurred at ca. 97 Ma, and more widespread deformation ca. 80 Ma involved south-ver­gent folding and thrusting of the Kahiltna assemblage that records collisional accretion of the Peninsular-Wrangellia terrane and juxtaposition of sediment wedges formed on the inboard and outboard terranes. More widespread mag­matism ca. 75–55 Ma occurred in two general pulses, each having distinct styles of localized deformation. Circa 75–65 Ma plutons were emplaced in a transpressional setting and stitch the accreted Peninsular and Wrangellia terranes to the Farewell terrane. Circa 65–55 Ma magmatism occurred across the entire range and extends for more than 200 km inboard from the inferred position of the continental margin. The Paleocene plutonic suite generally reflects shallower emplacement depths relative to older suites and is associ­ated with more abundant andesitic to rhyolitic volcanic rocks. Deformation ca. 58–56 Ma was concentrated along two high-strain zones, the most prominent of which is 1 km wide, strikes east-northeast, and accommodated dextral oblique motion. Emplacement of widespread intermediate to mafic dikes ca. 59–51 Ma occurred before a notable magmatic lull from ca. 51–44 Ma reflect­ing a late Paleocene to early Eocene slab window. Magmatism resumed ca. 44 Ma, recording the transition from slab window to renewed subduction that formed the Aleutian-Meshik arc to the southwest. In the western Alaska Range, Eocene magmatism included emplacement of the elongate north-south Mer­rill Pass pluton and large volumes of ca. 44–37 Ma andesitic flows, tuffs, and lahar deposits. Finally, a latest Eocene to Oligocene magmatic pulse involved emplacement of a compositionally variable but spatially concentrated suite of magmas ranging from gabbro to peralkaline granite ca. 35–26 Ma, followed by waning magmatism that coincided with initiation of Yakutat shallow-slab subduction. Cretaceous to Oligocene magmatism throughout the western Alaska Range collectively records terrane accretion, translation, and integration together with evolving subduction dynamics that have shaped the southern Alaska margin since the middle Mesozoic.

scholarly journals Oligocene-Neogene lithospheric-scale reactivation of Mesozoic terrane accretionary structures in the Alaska Range suture zone, southern Alaska, USA: Comment

2021 ◽  
Author(s):  
Grant Lowey
Keyword(s):  
Suture Zone ◽  
Ultramafic Rocks ◽  
Metamorphic Rocks ◽  
Geologic Mapping ◽  
Alaska Range ◽  
Denali Fault ◽  
South Central ◽  
Ultramafic Complex ◽  
History Of ◽  
Ultramafic Intrusion

Waldien et al. (2021) present new bedrock geologic mapping, U-Pb geochronology, and 40Ar/39Ar thermochronology from the eastern Alaska Range in south-central Alaska to determine the burial and exhumation history of metamorphic rocks associated with the Alaska Range suture zone, interpret the history of faults responsible for the burial and exhumation of the metamorphic rocks, and speculate on the relative importance of the Alaska Range suture zone and related structures during Cenozoic reactivation. They also propose that ultramafic rocks in their Ann Creek map area in south-central Alaska (herein referred to as the “Ann Creek ultramafic complex”) correlate with the Pyroxenite Creek ultramafic complex in southwestern Yukon, and that this correlation is “consistent with other estimates of >400 km” of offset on the Denali fault. However, despite Waldien et al.’s (2021) claim that the purportedly offset ultramafic rocks are “similar” and that characteristics of the Ann Creek ultramafic complex “make a strong case” for a faulted portion of an Alaska-type ultramafic intrusion, their paper gives short shrift in describing the Pyroxenite Creek ultramafic complex and in discussing previous estimates of displacement on the Denali fault. In Addition, Waldien et al. (2021) are either unaware of or ignore several key references of the Pyroxenite Creek ultramafic complex and estimates of displacement on the Denali fault. As a result, Waldien et al.’s (2021) claim of a “correlation” between allegedly offset ultramafic rocks is suspect, and their reference to “other estimates of >400 km” of offset on the Denali fault is incorrect, or at the very least misleading.

scholarly journals U-Pb geochronology of igneous and detrital zircon samples from the Tok River area, eastern Alaska Range, and Talkeetna Mountains, Alaska

2020 ◽  
Author(s):  
C.S. Holm-Denoma ◽  
K.R. Sicard ◽  
Evan Twelker
Keyword(s):  
Detrital Zircon ◽  
Alaska Range ◽  
Talkeetna Mountains

scholarly journals U-Pb and Lu-Hf isotope, age, and trace-element data from zircons at four sites in the western Alaska Range and Talkeetna Mountains, Alaska

2017 ◽  
Author(s):  
Erin Todd ◽  
Andrew Kylander-Clark ◽  
Alicja Wypych ◽  
Evan Twelker ◽  
K.R. Sicard
Keyword(s):  
Trace Element ◽  
Hf Isotope ◽  
Trace Element Data ◽  
Alaska Range ◽  
Element Data ◽  
Isotope Age ◽  
Talkeetna Mountains

scholarly journals Geologic Mapping and Mineral Resource Assessment of the Healy and Talkeetna Mountains Quadrangles, Alaska Using Minimal Cloud- and Snow-Cover ASTER Data

2007 ◽  
Author(s):  
Bernard E. Hubbard ◽  
Lawrence C. Rowan1 ◽  
Cynthia Dusel-Bacon ◽  
Robert G. Eppinger
Keyword(s):  
Mineral Resource ◽  
Snow Cover ◽  
Resource Assessment ◽  
Geologic Mapping ◽  
Aster Data ◽  
Mineral Resource Assessment ◽  
Talkeetna Mountains
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