Geology and geochronology of the Healy Quadrangle, south-central Alaska

Abstract

INTRODUCTION ACKNOWLEDGMENTS

Tectonic Underplating and Dismemberment of the Maclaren‐Kluane Schist Records Late Cretaceous Terrane Accretion Polarity and ~480 km of Post‐52 Ma Dextral Displacement on the Denali Fault

“…Accordingly, the mapping presented herein addresses the correlation between Mesozoic structures in the Clearwater Mountains (bold faults on Figure 2) and reactivated versions of those structures to the east (thin faults on Figure 2). The transition between reactivated and non-reactivated structures broadly coincides with the Maclaren River, which is also the location of a 1:250,000-scale quadrangle boundary (147°W) (cf., Csejtey et al, 1992;Nokleberg, Aleinikoff, Lange, et al, 1992;Wilson et al, 1998Wilson et al, , 2015. To our knowledge, our study is the first to attempt to correlate the geology across the region.…”

Tectonic Growth of the Late Paleozoic‐Middle Mesozoic Northwestern Margin of Laurentia and Implications for the Farewell Terrane: Stratigraphic, Structural, and Provenance Records From the Central Alaska Range

“…Due to abundant folds cut by high-angle KEOUGH AND RIDGWAY 10.1029/2021TC006764 13 of 35 faults (Figure 7b), stratigraphic thickness is extremely difficult to determine. Estimates based on regional geologic mapping studies suggest at least 500 m of stratigraphic thickness (Csejtey et al, 1986(Csejtey et al, , 1992.…”

“…The age of unit TRcs is best constrained by abundant, though poorly preserved, conodonts recovered from several locations in the central Alaska Range, three of which are within our study area. These collections yield an age range of late Carnian-middle Norian (Csejtey et al, 1986(Csejtey et al, , 1992Sherwood & Craddock, 1979;Till et al, 2007;Umhoefer, 1984). Unit Jf was previously mapped as part of unit KJf (Upper Jurassic-Lower Cretaceous) of Csejtey et al (1986Csejtey et al ( , 1992.…”

“…270 and 220 Ma. In this case, the arbitrary requirement for detrital ages to overlap in age in calculating a YC1σ MDA likely means that the YSG with a low uncertainty is a better estimation of the depositional age (e.g., Copeland, 2020); and (b) previous studies have documented abundant conodonts and radiolarians which constrain the age of unit TRcs to Late Triassic (late Carnian-middle Norian; Csejtey et al, 1986Csejtey et al, , 1992Csejtey et al, , 1992Sherwood & Craddock, 1979;Till et al, 2007;Umhoefer, 1984).…”

“…These assemblages were first defined by initial geologic mapping studies in the central Alaska Range including areas east of the Nenana River in the Wood River drainage (e.g., Bultman, 1972;Hickman, 1974;Sherwood, 1973Sherwood, , 1979Wahrhaftig, 1970aWahrhaftig, , 1970bWahrhaftig, , 1970c). These rocks have been interpreted to represent fault-bounded slivers of the ancestral North American/Laurentian margin (e.g., Csejtey et al, 1992;Sherwood & Craddock, 1979;Till et al, 2007), and also comprise parts of the Yukon-Tanana terrane of Foster et al (1994). More recent studies have interpreted these rocks as part of a parautochthonous assemblage related to the continental margin rather than allochthonous in the case of the Yukon-Tanana terrane proper (e.g., Nelson et al, 2013).…”