Geology of the Sleetmute A-5, A-6, B-5, and B-6 quadrangles, southwestern Alaska

Decker, J. E.; Robinson, M. S.; Waythomas, Christopher F.; Clough, J. G.

doi:10.14509/2280

Cited by 1 publication

(4 citation statements)

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“…About 20 of these complexes, which range from as small as 8 km 2 to as large as 650 km , crop out in a broad, 450-km-long, northeast-trending belt (Miller et al 1989;Moll-Stalcup 1994;Bundtzen and Miller 1997). rocks range from about 76 to 63 Ma (Moll et al 1981;Miller and Bundtzen 1994;Decker et al 1995; Bundtzen et al 1999). The comagmatic plutons yield ages ranging from about 71 to 67 Ma, although some younger ages (to 60 Ma) have been reported (Moll et al 1981;Miller and Bundtzen 1994;Decker et al 1995;Bundtzen et al 1999).…”

Section: In Thementioning

confidence: 99%

“…rocks range from about 76 to 63 Ma (Moll et al 1981;Miller and Bundtzen 1994;Decker et al 1995; Bundtzen et al 1999). The comagmatic plutons yield ages ranging from about 71 to 67 Ma, although some younger ages (to 60 Ma) have been reported (Moll et al 1981;Miller and Bundtzen 1994;Decker et al 1995;Bundtzen et al 1999). There is no significant time break between deposition of the uppermost Kuskokwim Group (Campanian) and…”

Section: In Thementioning

confidence: 99%

“…88, Field relations in the Chuilnuk Mountains (fig. 5) show that some dextral movement took place in Late Cretaceous time. In the aureole of the 68-Chuilnuk pluton (Decker et al 1995), hornfels metasedimentary rocks of the Kuskokwim Group are folded about closely spaced, upright, northtrending axes; the pluton truncated the folds, indicating that folding predated pluton emplacement.…”

Section: Displacement Historiesmentioning

confidence: 99%

“…Geologic map of the Chuilnuk and Kiokluk Mountains area near the Denali fault. North-trending folds in the contact aureole of the Chuilnuk pluton suggest pre-68 Ma dextral motion on the nearby Denali fault system.Adapted fromDecker et al (1995).in the Cantwell Basin (fig. 1)were erupted from 59.…”

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confidence: 99%

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Late Cretaceous through Cenozoic Strike‐Slip Tectonics of Southwestern Alaska

Miller¹,

Bradley²,

Bundtzen³

et al. 2002

The Journal of Geology

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New geologic mapping and geochronology show that marginparallel strike-slip faults on the western limb of the southern Alaska orocline have experienced multiple episodes of dextral motion since-100 Ma. These faults are on the upper plate of a subduction zone-350-450 km inboard of the paleotrench. In southwestern Alaska, dextral displacement is 134 km on the Denali fault, at least 88-94 km on the Iditarod-Nixon Fork fault, and perhaps tens of kilometers on the Dishna River fault. The strike-slip regime coincided with Late Cretaceous sedimentation and then folding in the Kuskokwim basin, and with episodes of magmatism and mineralization at ~ 70 ,-60, and-30 Ma. No single driving mechanism can explain all of the-95 millionyear history of strike-slip faulting. Since-40 Ma the observed dextral sense of strike slip has run contrary to the sense of subduction obliquity. This may be explained by northward motion of the Pacific Plate driving continental margin slivers into and/or around the oroclinal bend. From 44 to 66 Ma, oroclinal rotation, perhaps involving large-scale flexural slip, may have been accompanied by westward escape of crustal blocks along strike-slip faults. However , reconstructions of this period involve unproven assumptions about the identity of the subducting plate , the position of subducting ridges, and the exact timing of oroclinal bending, thus obscuring the driving mechanisms of strike slip. Prior to 66 Ma , oblique subduction is the most plausible driving mechanism for dextral strike slip. Cumulative displacement on all faults of the western limb of the orocline is at least 400 km, about half that on the eastern limb; this discrepancy might be explained by a combination of thrusting and unrecognized strike-slip faulting. l\t Figure 1. Map of Alaska, the northeastern Pacific, and parts of Canada and the Russian Far East showing key features mentioned in text. Geologic offsets and A' (Tintina fault), Band B' (Denali fault), and C and C' (Kaltag fault) are indicated. BRF Border Ranges fault; Castle Mountain fault. Strike-slip faults of Beringian margin after Worrall (1991).

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