Geology Commons^™

A Linear Modulation Osl Study Of The Unstable Ultrafast Component In Samples From Glacial Lake Hitchcock, Massachusetts, Usa, R. J. Goble, Tammy M. Rittenour

Geosciences Faculty Publications

Optical ages were determined for samples from delta and sand dune deposits associated with Glacial Lake Hitchcock near Amherst, Massachusetts using the single aliquot regenerative-dose (SAR) optically stimulated luminescence (OSL) technique. However, a strong unstable ultrafast component caused initial rejection of data from a large proportion of aliquots. A linearly modulated blue OSL (LM-OSL) study was undertaken on the sample with the strongest ultrafast component, with the data modelled using the equation of Bulur et al. (2000) as 5 fast, medium and slow components, and 1 ultrafast component.

The ultrafast component dominates the LM–OSL, almost completely obscuring the fast component. …

Using Fill Terraces To Understand Incision Rates And Evolution Of The Colorado River In Eastern Grand Canyon, Arizona, J. L. Pederson, M. D. Anders, Tammy M. Rittenour, W. D. Sharp, J. C. Gosse, K. E. Karlstrom

Geosciences Faculty Publications

The incision and aggradation of the Colorado River in eastern Grand Canyon through middle to late Quaternary time can be traced in detail using well-exposed fill terraces dated by a combination of optically stimulated luminescence, uranium series, and cosmogenic nuclide dating. This fluvial history provides the best bedrock incision rate for this important landscape and highlights the complications and advantages of fill terrace records for understanding river long-profile evolution and incision. The use of fill terraces, as distinct from strath terraces, for calculating incision rates is complicated by the cyclic alluviation and incision they record. In the example of the …

Structural Evolution And Vorticity Of Flow During Extrusion And Exhumation Of The Greater Himalayan Slab, Mount Everest Massif, Tibet/Nepal: Implications For Orogen-Scale Flow Partitioning, M. J. Jessup, R. D. Law, M. P. Searle, Mary S. Hubbard

Geosciences Faculty Publications

The Greater Himalayan Slab (GHS) is composed of a north-dipping anatectic core, bounded above by the South Tibetan detachment system (STDS_ and below by the Main Central thrust zone (MCTZ). Assuming simultaneous movement on the MCTZ and STDS, the GHS can be modelled as a southward-extruding wedge or channel. New insights into extrusion-related flow with the GHS emerge from detailed kinematic and vorticity analyses in the Everest region. At the highest structural levels, mean kinematic vorticity number (Wm) estimates of 0.74-0.91 (c. 45-28% pure shear) were obtained from sheared Tethyan limestone and marble from the Yellow Band on Mount Everest. …

Mineralogical Characterization Of Protolith And Fault Rocks From The Safod Main Hole, John G. Solum, Stephen H. Hickman, David A. Lockner, Diane E. Moore, Ben A. Van Der Pluijm, Anja M. Schleicher, James P. Evans

Geosciences Faculty Publications

Washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the San Andreas Fault Observatory at Depth (SAFOD). Both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology, P-T conditions, deformation mechanisms, and fluid composition and abundance. Regions of distinct neomineralization bounded by faults may record alteration associated with fluid reservoirs confined by faults. In addition, both smectites occurring as mixed-layer phases and serpentine minerals are found in association with active strands of the San Andreas Fault that were intersected during drilling, although …