Ar Dating of Near-Surface Faulting

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9980459HallRadiometric dating of ductile shear zones has revolutionized understanding of fault evolution and deep-crustal processes, however use of radiometric methods to date brittle, near surface faulting has not been generally utilized, as several factors make the interpretation of the data much more problematic. One of the major problems at near-surface conditions is the presence of mineral phases that are both detrital (primary) and authigenic (secondary) in origin. Therefore, radiometric dating of such rocks typically results in an "age" that reflects a mixture of primary and secondary clay forming events. This project will use such mixed-source age spectra along with methodology to determine the percentages of detrital vs. authigenic phases to calculate the authigenic end member age. Results should refine this approach and provide preliminary field applications to several important shallow-level faults.