Thinly laminated siltstone and sandy siltstone are major components of the Upper Permian Brushy Canyon Formation, west Texas and south New Mexico. These rocks have been variously interpreted as the deposits of low-den...Thinly laminated siltstone and sandy siltstone are major components of the Upper Permian Brushy Canyon Formation, west Texas and south New Mexico. These rocks have been variously interpreted as the deposits of low-density turbidity currents or as windblown sediment deposited over water. Nevertheless, all models agreed that this lithology was deposited without subsequent reworking by bottom currents or burrowing organisms. These siltstones, thus, are ideal test units for quantitatively estimating hydraulic properties of the flows that formed them. In particular, the Zr/Ti ratio was tested as a geochemical proxy for flow size and transport distance. In situ geochemical abundance and grain size of particles with contrasting susceptibility to erosion—Zr- and Ti-rich particles—were mapped and measured by X-ray fluorescence analytical microscopy, μXRF. Lamination thickness was measured from Fe fluorescence intensity, which increased sharply at the top of each layer. Within the same sample, zircon grains were systematically finer than rutilated quartz grains. Zr/Ti fluorescence ratio positively correlated with lamination thickness, not particle sizes. In other words, Zr/Ti fluorescence ratio fluctuations resulted from variations in mineral abundance. Therefore, variations of Zr/Ti fluorescence ratio in these siltstones are likely caused by fluctuations in the intensity of erosional events rather than transport distance. High Zr/Ti ratios and thick laminations reflect periods of enhanced erosion. The average wind velocity during typical events was estimated to be at least 150 km?hr<sup>?1</sup>, or the equivalent of a Category 1 hurricane. The method used here could be applied to both outcrop and subsurface strata correlation.展开更多
Sedimentary processes have direct effects on the geometry, distribution, and geophysical and geochemical properties of sedimentary rocks. Being able to qualitatively and quantitatively visualize the movement vector of...Sedimentary processes have direct effects on the geometry, distribution, and geophysical and geochemical properties of sedimentary rocks. Being able to qualitatively and quantitatively visualize the movement vector of sediments in fluid media is essential for understanding the complicated earth surface processes. Nonintrusive measuring and observing the interaction between the movement of fluid media and particles by a laser sheet flow visualization technique requires a light source that is thin and monochromatic. Yet, an ideal laser sheet generator is rather expensive and inaccessible, especially for schools and universities residing in low-income countries. This project is proposing a less-expensive option for a laser sheet source for nonintrusive flow visualization and modeling. Here, cylindrical lens is used to convert from point laser into sheet laser. Multiple combinations of laser diodes of various wavelength (nanometer) and power (milliwatt) and cylindrical lenses of various dimensions are analyzed. The pair that is able to produce the thinnest and brightest light sheet is not only effective but also affordable. The combination of manufactured laser module of 532 nm 50 mW and a single rod lens is able to generate a light sheet that is less than 4 mm thick. When choosing a laser module, this research recommends one at a wavelength of 532 nm with any electric power (high wattage results in high lumens).展开更多
文摘Thinly laminated siltstone and sandy siltstone are major components of the Upper Permian Brushy Canyon Formation, west Texas and south New Mexico. These rocks have been variously interpreted as the deposits of low-density turbidity currents or as windblown sediment deposited over water. Nevertheless, all models agreed that this lithology was deposited without subsequent reworking by bottom currents or burrowing organisms. These siltstones, thus, are ideal test units for quantitatively estimating hydraulic properties of the flows that formed them. In particular, the Zr/Ti ratio was tested as a geochemical proxy for flow size and transport distance. In situ geochemical abundance and grain size of particles with contrasting susceptibility to erosion—Zr- and Ti-rich particles—were mapped and measured by X-ray fluorescence analytical microscopy, μXRF. Lamination thickness was measured from Fe fluorescence intensity, which increased sharply at the top of each layer. Within the same sample, zircon grains were systematically finer than rutilated quartz grains. Zr/Ti fluorescence ratio positively correlated with lamination thickness, not particle sizes. In other words, Zr/Ti fluorescence ratio fluctuations resulted from variations in mineral abundance. Therefore, variations of Zr/Ti fluorescence ratio in these siltstones are likely caused by fluctuations in the intensity of erosional events rather than transport distance. High Zr/Ti ratios and thick laminations reflect periods of enhanced erosion. The average wind velocity during typical events was estimated to be at least 150 km?hr<sup>?1</sup>, or the equivalent of a Category 1 hurricane. The method used here could be applied to both outcrop and subsurface strata correlation.
文摘Sedimentary processes have direct effects on the geometry, distribution, and geophysical and geochemical properties of sedimentary rocks. Being able to qualitatively and quantitatively visualize the movement vector of sediments in fluid media is essential for understanding the complicated earth surface processes. Nonintrusive measuring and observing the interaction between the movement of fluid media and particles by a laser sheet flow visualization technique requires a light source that is thin and monochromatic. Yet, an ideal laser sheet generator is rather expensive and inaccessible, especially for schools and universities residing in low-income countries. This project is proposing a less-expensive option for a laser sheet source for nonintrusive flow visualization and modeling. Here, cylindrical lens is used to convert from point laser into sheet laser. Multiple combinations of laser diodes of various wavelength (nanometer) and power (milliwatt) and cylindrical lenses of various dimensions are analyzed. The pair that is able to produce the thinnest and brightest light sheet is not only effective but also affordable. The combination of manufactured laser module of 532 nm 50 mW and a single rod lens is able to generate a light sheet that is less than 4 mm thick. When choosing a laser module, this research recommends one at a wavelength of 532 nm with any electric power (high wattage results in high lumens).
