Abstract
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.
Highlights
Comment and ReplyPlutonic Suite represents the roots of the Chitina magmatic arc, and the Kluane Ranges
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
Waldien et al (2021) suggest that the Clearwater metasediments formed part of a Mesozoic flysch basin that collapsed during north-to-south accretion of the Wrangel composite terrane with the western margin of North America, and that the metasedimentary rocks were sourced from the Talkeetna arc and Chitina arc, which were emplaced along the outboard margin of the Wrangellia composite terrane
Summary
Plutonic Suite represents the roots of the Chitina magmatic arc, and the Kluane Ranges. For. Saint Elias Plutonic Suite, far right vertical gray bars correspond to U-Pb zircon ages for the Talkeetna arc, south-central Alaska (from Rioux et al., 2003, 2007) and biotite Ar/Ar ages for the Gravina (=Chitina) arc, southeastern Alaska Horizontal gray bar across Kluane Ranges Plutonic Suite corresponds to Ar-Ar age of basalt in Chisana Formation, southern Alaska (after Short et al, 2005). Dodds and Campbell (1988) provide an interpretation of the intrusive rocks, suggesting that the Pyroxenite Creek ultramafic complex and Shorty Creek pluton are part of the 117–106 Ma Kluane Ranges plutonic suite that represents the roots of the Chisana magmatic arc (Fig. 1). The Kluane Ranges plutonic event of 117–106 Ma is not quite the same as the 115–100 Ma generalization proffered by Waldien et al (2021) for ultramafic and intermediate rocks throughout southeastern Alaska and southwest Yukon
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
