Late Cenozoic Uplift of Denali and Its Relation to Relative Plate Motion and Fault Morphology

Abstract

Apatite fission-track analysis of samples that cover a 4-kilometer vertical section from the western flank of Denali (Mount McKinley), North America's highest mountain, suggests that the mountain massif was formed by rapid uplift (> 1 kilometer per million years) beginning approximately 6 million years ago (Ma). Uplift was a result of the morphology of the Denali fault and a change in motion of the Pacific plate with respect to North America at approximately 5 Ma, which created opposing tangential vectors of relative movement along the fault and forced the intervening crustal blocks upward.

Persistent long-term ( c. 24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

“…of the landmark vertical-transect AFT studies (Fitzgerald et al 1993). The results clearly indicate a change in exhumation rate at approximately 6 Ma, which is interpreted as the beginning of the uplift of the Central Alaska Range.…”

“…The exhumation event is correlated with the inferred depositional age of the 1000 m-thick Nenana Gravel of the Tanana Basin, located about 150 km to the east (Wahrhaftig et al 1994). The question remains whether the limited spatial scope of the Fitzgerald et al (1993) study (restricted to Mt McKinley, with no samples dated from the vicinity of the Denali Fault) was sufficient to capture the full exhumation history of the region considering the large variation in exhumation patterns found in other major orogens (e.g. Little et al 2005;Yin 2006;Tricart et al 2007).…”

“…Little et al 2005;Yin 2006;Tricart et al 2007;Seeber et al 2010). Thus, orogen-scale interpretations of tectonic processes based on thermochronological analyses of a single vertical transect (Fitzgerald et al 1993;O'Sullivan & Currie 1996;Haeussler et al 2008) or a single rock sample (Richter et al 1990) may not capture the spatial and temporal variability inherent to broad-scale orogenesis. Although spatially restricted sampling for thermochronology can provide first-order information on the timing of orogenesis, can the total exhumation history of an orogen be constrained by such a practice?…”

“…Many data interpretation methods regarding orogenic tectonothermal histories have been standardized; including the time-averaged time-temperature (T-t) plots of one sample (McAleer et al 2009) or numerous samples from one vertical mountain transect (Fitzgerald et al 1993). Typically, any significant changes in timeaveraged cooling rates (i.e.…”

Apatite thermochronology in modern geology

“…In areas of substantial block uplift, thermochronological ages may be disrupted across tectonic structures. Such offsets in the palaeo-isotherm/-depth stratigraphy can be used to determine relative uplift between different blocks and the amount of throw on bounding faults (Fitzgerald & Gleadow 1988Dumitru 1991;Foster & Gleadow 1992aFitzgerald et al 1993;O'Sullivan et al , 2000Johnson 1997;Rahn et al 1997;Wagner et al 1997;Thomson 1998;Kohn et al 1999;Redfield et al 2007;Ventura et al 2009;Xu et al 2009). Moreover, the timing of tectonic activity may be determined by the direct dating of faults, lineaments or pseudotachylites (Harman et al 1998;O'Sullivan et al 1998;Raab et al 2002Raab et al , 2009Zwingmann & Mancktelow 2004;Tagami 2005;Timar-Geng et al 2009;Yamada et al 2009).…”