Figure 7
Comparison of observed and modelled spatial distributions of thermochronological ages overlaid on the topography of southeast Alaska and shown with major faults35,36. (a–b) Compilation of measured bedrock AHe (a) and AFT (b) ages in the southern Alaskan plate corner (see Supplementary Table 1 and references therein). Note that the area of most rapid and deep exhumation (marked by the pinkish polygon with dashed outline) was observed from detrital zircon fission track (ZFT) data from glacial outwash, i.e., from catchment elevations including low, ice-covered elevations where bedrock cannot be sampled directly (see refs.18,43,52 for details). Importantly, the very young AHe ages along the area referred to as “shallow fault-thrust belt exhumation” in panel “a” are the result of exhumation along the shallow particle paths in the fold-and-thrust belt32 in combination with high precipitation on the coast and therefore should not be considered for comparison with the model data. CAR—Central Alaska Range, CM—Chugach Mountains, EAR—Eastern Alaska Range, TM—Talkeetna Mountains, WAR—Western Alaska Range, WR—Wrangell Mountains. White ellipse: CC—Chugach Core. (c) Predicted AHe ages for model 4 (fluvial erosion; half upper plate advance). Note that three observed zones of relatively young thermochronological ages (the Fairweather fault/St. Elias syntaxis, the Chugach Core, and the Alaska Range) find their modelled equivalent in the similar relative positions of isolated regions above the main structures of localized deformation in the crust and mantle of the overriding lithosphere (from east to west: transform fault, decollement, and orogenic wedge; see Fig. 3b). The westernmost zone of young predicted ages (associated with the orogenic wedge) does not exactly match the Alaska Range, where there is insufficient measured data for a good comparison. AM—Aleutian megathrust, BRF—Border Ranges fault, CCF—Connector fault, CMF—Castle Mountain fault, CSEF—Chugach-St. Elias fault, FWF—Fairweather fault, PFZ—Pamplona fault zone, TF—Totschunda fault.
