کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9522316 | 1634964 | 2005 | 16 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Southward-younging apatite (U-Th)/He ages in the northern California Coast Ranges due to a northward-migrating crustal welt
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم زمین و سیاره ای (عمومی)
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چکیده انگلیسی
(U-Th)/He in apatite dating of Franciscan Formation samples from between 39°47â²N and 39°08â²N in the northern California Coast Ranges (NCCR) reveals a southward- and downward-younging pattern of ages (21.8 ± 0.6 Ma to 7.9 ± 0.9 Ma). These ages are interpreted to represent a northward or northeastward dipping fossil He partial retention zone that was tilted and exhumed by a northward-migrating pulse of crustal thickening that begins â¼150-200 km ahead of the migrating Mendocino Triple Junction (MTJ) [K.P. Furlong, R. Govers, Ephemeral crustal thickening at a triple junction: the Mendocino crustal conveyor, Geology 27 (1999) 127-130). The â¼8 Ma ages from the southern end of the sample transect are interpreted to come from rocks that were immediately below the He partial retention zone when crustal thickening began, â¼5 my before the MTJ passed by; these rocks have now reached the surface, â¼3 my after passage of the MTJ. The older ages from the central and northern portions of the sample transect are interpreted to represent rocks that were within the He partial retention zone prior to crustal thickening ahead of the MTJ, and which therefore record ages transitional from older subduction-related cooling and exhumation to more recent transform-related cooling and exhumation. In addition to providing support for the model of a migrating crustal welt associated with the MTJ, the existence of an essentially intact, gently tilted fossil partial retention zone in the northern California Coast Range raises the possibility of using isochronous surfaces as neotectonic structural markers in this geologically complex and heavily vegetated region.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 235, Issues 1â2, 30 June 2005, Pages 107-122
Journal: Earth and Planetary Science Letters - Volume 235, Issues 1â2, 30 June 2005, Pages 107-122
نویسندگان
Robert J. Brady, James A. Spotila,