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项目编号0230383
An Apatite/Zircon (U-th)/He Thermochronometric Study of the Rapid Tectonic Denudation of an Oblique Crustal Section-Southern Sierra Nevada, California
Jason Saleeby
主持机构California Institute of Technology
开始日期2002-12-01
结束日期2005-11-30
资助经费268873(USD)
项目类别Continuing Grant
资助机构US-NSF(美国国家科学基金会)
项目所属计划Tectonics
语种英语
国家美国
英文简介PROJECT SUMMARY
The PI's propose to produce a series of (U-The)/He apatite and zircon thermochronologic profiles in the southernmost Sierra Nevada region as a test of the very rapid tectonic denudation of the Sierran batholithic rocks by low-angle detachment faulting in latest Cretaceous-early Paleogene time. This phase of denudation exposed an oblique crustal section through the southernmost Sierra Nevada batholith to a paleodepth of ~35 km. Apatite He studies in the greater Sierra Nevada region to the north have revealed the persistence of a high standing orogenic plateau with long wavelength-high relief fluvial dominated topography during the same time interval. In marked contrast the deepest level exposures of the batholith to the south had subsided to marine conditions by early Eocene time in conjunction with tectonic denudation. These profound along strike variations in the paleogeomorphology of the Sierran magmatic arc can be linked to the tectonic removal of the sub-batholithic mantle lithosphere beneath the southernmost Sierra-northern Mojave Desert region by a shallow flat-slab segment of the subducting
oceanic plate, and the related tectonic underplating of Franciscan trench-affinity
metamorphic assemblages. The PI's have identified an array of known and apparent high-
level batholithic detachment sheets along the southernmost Sierra and northern Mojave
Desert region that appear to represent part of the upper crustal rocks that were displaced
by the detachment system. They have also identified modern topographic anomalies and
anomalous structural-textural overprints in the basement rocks of the southern Sierra
region which correspond to the onset of steep gradients in batholith emplacement
barometry and its implicit depth of denudation. They interpret these areas to represent the
remnants of footwall complexes proximal to the breakaway zones where the northernmost detachment sheets calved off the edge of the orogenic plateau. Vertical
apatite and zircon thermochronologic profiles are proposed across these zones as a test of
very rapid cooling and tectonic denudation. These profiles will be extended southward
along constant elevation profiles to the deepest exposed levels of the batholith in order to
further test for regional rapid cooling, and to test for a possible southward migration in
progressively deeper levels of denudation with time. The broader goals are to relate the
paleogeomorphic evolution of the southern Sierra region to lithosphere-scale tectonics
and dynamics, and to relate these findings to the globally important problem of the
upward migration and surface exposure of deep crystalline basement rock as related to
uplift, erosion, tectonic denudation, and the evolution of lower crust and upper mantle.
The proposed research program runs for a period of three years and includes a vigorous
program of sample collecting, mineral separation, geochemical analysis, and the
synthesis of the new data with existing geological and geochemical data sets. The project
will entail partial efforts of the joint PI's and their technical staff, and constitute a major
component of a Caltech Ph.D. Dissertation.
来源学科分类Geosciences
URLhttps://www.nsf.gov/awardsearch/showAward?AWD_ID=0230383
资源类型项目
条目标识符http://119.78.100.177/qdio/handle/2XILL650/342291
推荐引用方式
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Jason Saleeby.An Apatite/Zircon (U-th)/He Thermochronometric Study of the Rapid Tectonic Denudation of an Oblique Crustal Section-Southern Sierra Nevada, California.2002.
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