--> Abstract: Early Cretaceous to Late Tertiary Tectonics and Uplift in the Central Brooks Range, Alaska: Apatite Fission Tract Studies, by J. M. Murphy and P. B. O'Sullivan; #91012 (1992).

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ABSTRACT: Early Cretaceous to Late Tertiary Tectonics and Uplift in the Central Brooks Range, Alaska: Apatite Fission Tract Studies

MURPHY, JOHN M., and PAUL B. O'SULLIVAN, La Trobe University, Bundoora, Victoria, Australia

Contrary to current thinking that deformational and cooling events in the Brooks Range had ceased before the Paleocene, new apatite fission track data show conclusively that these processes have reoccurred throughout the Tertiary and as recently as the Late Oligocene. Here we summarize data from sample profiles in: (1) the Doonerak Window (n = 6); (2) the Endicott allochthon in the Atigun Pass and Killik River regions (n = 16); and (3) the Chandalar (n = 13), Arrigetch (n = 6), and Igikpak (n = 8) gneissic bodies.

Fission track data from the Doonerak Window indicate rapid cooling at ~28 Ma. Estimated uplift is ~2-3 km in ~3-5 m.y. Data from Atigun Pass and Killik River areas indicate two phases of rapid cooling at ~99 and ~69 Ma. Data from the Chandalar plutons indicate two phases of rapid cooling at ~60 Ma and <48 Ma. Data from the Arrigetch and eastern Igikpak plutons indicate rapid cooling at ~27 Ma while westward, across a fault, cooling occurred within the Igikpak pluton at ~36 Ma. The combined data from all areas indicate the central Brooks Range has experienced multiple cooling events at ~99, ~69, <48, ~36, and ~28 Ma.

These data are consistent with larger fission track data sets from the North Slope, Yukon-Koyukuk, Seward Peninsula, and Ruby regions of northern Alaska, which also show evidence of previously unrecognized major Tertiary tectonic events. In light of these data, one must reinterpret the importance of Tertiary tectonics in the structural development of northern Alaska.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)