Paleomagnetic directions have been obtained from 190 Middle Miocene (12-20 Ma) mafic volcanic flows in 16 mountain ranges in the Mojave-Sonora desert region of western Arizona and southeastern California. These flows generally postdate Early Miocene tectonic deformation accommodated by low-angle normal faults but predate high-angle normal faulting in the region. After detailed magnetic cleaning experiments, 179 flows yielded characteristic thermal remanent magnetism (TRM) directions. Because of the episodic nature of basaltic volcanism in this region, the 179 flows yield only 65 time-distinct virtual geomagnetic poles (VGPs). The angular dispersion of the VGPs is consistent with the angular dispersion expected for a data set that has adequately averaged geomagnetic secular variation. The paleomagnetic pole calculated from the 65 cooling unit VGPs is located at 85.5°N, 108.9°E within a 4.4° circle of 95% confidence. This pole is statistically indistinguishable (at 95% confidence) from reference poles calculated from similar-age rocks in stable North America and from a paleomagnetic pole calculated from similar-age rocks in Baja and southern California. From the coincidence of paleomagnetic poles from the Mojave-Sonora and adjacent areas, we can conclude that: (1) vertical-axis tectonic rotations have not accompanied high-angle normal faulting in this region; (2) there has been no latitudinal transport of the region since 12-20 Ma; and (3) long-term nondipole components of the Miocene geomagnetic field probably were no larger than those of the recent (0-5 Ma) geomagnetic field. In contrast, paleomagnetic data of other workers indicate vertical-axis rotations of similar-age rocks in the Transverse Ranges, the Eastern Transverse Ranges, and the Mojave Block. We speculate that a major discontinuity in the vicinity of the southeastward projection of the Death Valley Fault Zone separates western areas affected by vertical-axis rotations from eastern areas that have not experienced such rotations.

This thesis looks at the pueblo theory as it was presented: whether there is anything supporting Rogers' theory, whether a pueblo could have existed in the area, and why the claim has been generally accepted by the archaeological community.

A series of severe and prolonged droughts occurred throughout the Northern Hemisphere between approximately 1150 BP to 600 BP. This phenomenon is referred to as the Medieval Climatic Anomaly and has been shown to have differentially impacted various regions of the world. Previous studies have suggested causal links between the Medieval Climatic Anomaly and observed culture change. The goal of this study was to examine the Antelope Valley region of the Mojave Desert for evidence of impacts on human populations related to the Medieval Climatic Anomaly. To achieve this goal, a sample selection of archaeological sites was chosen from lands within Edwards Air Force Base. These sites represented occupations which occurred immediately before, during, and after the Medieval Climatic Anomaly. Site assemblages were analyzed and compared by cultural period, with cross-comparisons made of artefactual and ecofactual constituents. Site densities and areal extents were also examined and compared. These analyses showed the emergence of trends concurrent with the introduction of the Medieval Climatic Anomaly. The data supports the hypothesis that humans who populated the Antelope Valley region of the Mojave Desert during this period may have engaged in population aggregation, with a tethered nomadism subsistence strategy. The data also shows evidence that upon the amelioration of the environment after the Medieval Climatic Anomaly, site characteristics within the region saw a significant shift. While the evidence generated by this study does suggest a link between climatic change experienced during the Medieval Climatic Anomaly and change observed within the archaeology of the Antelope Valley, it does not suggest climate as a sole, or even primary, causal factor. Rather, the intent of this study was to identify one possible variable responsible for observed change that occurred in the region. With this in mind, the Medieval Climatic Anomaly was found to have been significant enough to have either directly or indirectly impacted the prehistoric occupants of the study region.

For more than two centuries, humans have been spewing “greenhouse gases” into the atmosphere through the burning of fossil fuels, deforestation, and the development of land, causing the planet’s surface temperature to increase at an accelerated rate. Climate change is one of the most pressing issues that the world is facing today, and in order to combat the effects of climate change, it is necessary to adopt the use of more renewable technology, namely solar energy. The United States' best region for solar development is the Mojave Desert, and many large-scale projects are being built or proposed to be built in the area. However, the deployment of solar technology in the Mojave Desert comes with significant ecological, socioeconomic, and political impacts. This paper is intended to provide an overview of the issues surrounding solar development in the Mojave Desert.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.

Barium is a relatively abundant element in the crustal environments, Ba quantities can range from anywhere between 200ppm to 900ppm. Most common forms of Ba-minerals found in the environment are barite (BaSO4), witherite (BaCO3) and hollandite (Ba2Mn8O16). Ba is a useful element; it is used in various industries as a component in drilling fluids, in medical research and in manufacturing of various substances such as glass, ceramics, printing paper etc. However high quantity of Ba can be potentially toxic for the human body and can impair plant growth. It is therefore, important to review the terrestrial biogeochemical cycle of Ba, which is less studied and less understood than the oceanic biogeochemical cycle of Ba. Additionally, terrestrial systems face a diverse climate and are not as stable as the oceanic systems. Due to this the terrestrial biogeochemical cycle of barium is continuously changing and is more dynamic than the oceanic cycle. By studying one part of the cycle, i.e. the interaction of Ba in the atmosphere with the geosphere in the Mojave desert, NV, I propose a study to test the hypothesis that occurrence of, Ba-mineral, barite, in desert soils is mainly driven by dust flux. The proposal includes methodology for dust collection, sample analysis using XRF, XRD and SEM.EDS techniques and potential budget and timeline. Evidence supporting this claim would suggest that dust transports such minerals, affects the soil chemistry of desert soils and the interaction of various terrestrial systems.

No description available.

Geoarchaeology -- Pre-Clovis archaeology -- Site search strategies.

No description available.

Currently the size and frequency of wildfires are increasing at a global scale, including arid ecosystems that exhibit great sensitivity to disturbance. Fire effects on plant pollination and reproductive success in deserts are largely unknown. Plant dependence on animal pollinators for reproduction can increase the risk of reproductive failure if pollination services are hindered or lost. Species that depend on few taxonomically related pollinator species are expected to be most negatively affected by disturbances that disrupt pollination interactions. To assess fire and isolation effects on reproductive success in desert plant communities, and how wildfire influences the pollination success of generalist and specialist pollinated plants, the number of flowers, fruits, and viable seeds produced by plants surviving in burned and unburned desert landscapes were compared. Fire increased flower production for wind and generalist pollinated plants, and did not affect specialist plant flower production. Increases may be associated with positive physiological responses exhibited by plants surviving in burned areas. Fire did not affect pollination services. Wildfire effects on fruit production were neutral or positive, and overall seed:ovule ratios varied by 3% or less in burned and unburned areas for each pollination strategy. Increasing isolation within burned areas did not affect fruit production for generalist or specialist pollinated plants, suggesting that pollination services are functional across expansive burned desert landscapes. Annual reproductive output varied between years in burned and unburned areas, and shifts likely resulted from variation in annual precipitation patterns. Reductions in landscape reproductive output may be partially compensated by increased per plant fruit and seed production and maintaining pollinator services across burned landscapes, providing native shrub communities the possibility to naturally recover from fire disturbances. Habitat disturbances can influence plant interactions with herbivores, in addition to pollinators. To understand how fire and ungulate herbivory affect reproductive success of specialist pollinated desert plants, reproductive effort, floral herbivory, and pollinator visitation and success, were compared for Yucca baccata, and Yucca brevifolia in burned and unburned areas of the Mojave Desert. Fire increased Y. baccata flowering from 12% to 22% of plants in burned areas, but had no effect on the number of flowers or fruits produced per plant. Fruit set and pollinator collection failed at all sampled Y. baccata individuals, while fire and herbivory had no effect on Y. brevifolia flower, fruit, and pollinator collection. Herbivores consumed 50% and 67% of floral stalks produced by Y. baccata in unburned and burned areas. Herbivores pose a clear threat to successful sexual reproduction for Y. baccata. Removal of ungulate herbivores during important flowering periods may still result in failed fruit and seed production if local pollinator reserves have been drastically reduced or lost.