Supplemental Material: Neogene sedimentary record of the evolution of a translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development, and regional tectonics of southern Alaska

Ar/Ar geochronologic and U-Pb detrital zircon geochronologic ages.

Deformation between the highly oblique Yakutat–North American plate boundary and the Eastern Denali fault

This study investigates the spatial and temporal pattern of rock exhumation inboard of the highly oblique Yakutat–North American plate boundary. We aim to quantify how far deformation is transferred inboard of the Fairweather transform plate boundary and across the Eastern Denali fault. We present new detrital apatite and zircon fission track data from 27 modern drainages collected on both sides of the Eastern Denali fault and from the Alsek and Tatshenshini River catchments that drain the mountainous region between the Fairweather fault and the Eastern Denali fault. By integrating our data with published bedrock and detrital geochronology and thermochronology, we show that exhumation reaches much farther inboard (>100 km) of the Fairweather fault than farther north in the St. Elias syntaxial region (<30 km). This suggests that the entire corridor between the Fairweather and Eastern Denali faults exhumed since mid-Miocene time. The Eastern Denali fault appears to be the backstop, and late Cenozoic exhumation northeast of the fault is very limited.

Supplemental Material: Neogene sedimentary record of the evolution of a translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development, and regional tectonics of southern Alaska

Ar/Ar geochronologic and U-Pb detrital zircon geochronologic ages.

Supplemental Material: Deformation between the highly oblique Yakutat–North American plate boundary and the Eastern Denali fault

All peak fitting results from this study and previously published catchments (Table S1) and the single-grain data of the new data (Table S2).

Supplemental Material: Deformation between the highly oblique Yakutat–North American plate boundary and the Eastern Denali fault

All peak fitting results from this study and previously published catchments (Table S1) and the single-grain data of the new data (Table S2).

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

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.

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

Topics of discussion raised by Lowey (2021) include the correlation of ultramafic-intermediate intrusions hosted within the Clearwater metasediments/Dezadeash Formation and their displacement by the Denali fault. These topics were not main points of Waldien et al. (2021), but instead logical extrapolations of the information presented and synthesized therein. Here we re-emphasize the key findings of Waldien et al. (2021) and discuss only the relevant aspects of the ultramafic-intermediate intrusions and their displacement.

Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali and Totschunda faults in central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value, if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elements to model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.