Paleomagnetic data were collected from Miocene volcanic rocks in the Turtle Mountains, Clipper Mountain, Colton Hills, and Piute Range of the southern Basin and Range (SBR) province in southeastern California as well as in the Soledad Mountains of the Mojave block in southern California. The data from these two tectonic provinces yield significantly different paleomagnetic directions, which probably indicates the existence of a major crustal and /or lithospheric discontinuity in the area between the Barstow Basin and the Clipper Mountain. Comparing the mean direction from the SBR data to the Miocene expected direction indicates no statistically significant rotation (R = -0.2° ± 18.2°) or flattening (F = -6.5° ± 9.2°). A similar comparison for the Soledad Mountain data, which were combined with data of Burke et al. (1982) from the Barstow Basin, yields a significant rotation of -43.5° ± 12.9° and flattening of 19.3° ± 10.6° for the Mojave block. These Mojave block values may be exaggerated a few degrees due to inadequate averaging of secular variation and possible improper structural corrections.

In the Mojave Pegmatite district, located in northwestern AZ, numerous pegmatites intrude syn- to post-collisional Paleoproterozoic granitic rocks. The slightly older Cerbat plutons are associated with the suturing of the Mojave and Yavapai terranes whereas Aquarius granites were emplaced during the Yavapai Orogeny as the sutured terranes docked with North America. A detailed study of 5 pegmatites shows that they are zoned with composite cores and contain REE minerals characteristic of NYF pegmatites. However, they exhibit characteristics atypical for NYF pegmatites including F depletion, white microcline, an absence of columbite and, in the Rare Metals pegmatite, have muscovite and beryl. With the exception of the Kingman pegmatite, they exhibit normal LREE-HREE distributions. The Kingman pegmatite is extremely LREE enriched, HREE depleted and exhibits an unusual Nd enrichment which, in some cases, is sufficiently high that allanite is Nd dominant, thus a new mineral species, allanite-Nd.

Mesozoic Cordilleran arc magmatism along the western margins of North and South America shows similar patterns of episodic activity, but differences in tectonic setting, in composition, and in peak magnitudes of magma fluxes. The development of iron oxide(-copper-gold) (‘IOCG’) mineralization accompanies the pulse of arc magmatism in North and South America, but is most prolific during the early to middle Mesozoic pre-orogenic phases of the Cordillera. The focus of this work is to better understand the episodic nature of Cordilleran magmatism, controls to magma sources and compositions, and controls to Cordilleran IOCG mineralization. The objectives of this study are accomplished by focusing on two regions of the Cordillera that experienced similar early-middle Mesozoic tectonic settings, but display very different magmatic fluxes, compositions, and development of IOCG systems. The Coastal Batholith of northern Chile was investigated for the timing, composition, and fluxes of magmatism at three scales of observation including 1:1M scale between ~18°S to 34°S, 1:100K scale between 26°S to 28°S, and 1:20K scale along a transect at ~27.5°S where new major elemental, trace elemental, and Nd, Sr, and O isotope data were acquired. From the western United States magmatic fluxes and compositions were compiled from the literature, as were characteristics of Jurassic IOCG occurrences in the central Mojave Desert, California. Geologic framework analysis at 1:250K scale and new 1:5K scale mapping of the hydrothermal features associated with Jurassic IOCG occurrences were conducted in the central Mojave Desert, California. Results from northern Chile reveal that the Coastal Batholith formed in a dominantly extensional setting, had episodic magma fluxes that were dominantly mafic (dioritic-quartz dioritic) during peak output, and has uniformly depleted mantle-like Nd and Sr isotopes regardless of magma composition. Published compilations from coeval arcs of North America indicate that they display the opposite relationships to Chile between tectonic setting, magmatic fluxes, and magmatic compositions. Results from mapping in the southern Palen Mountains, California, and synthesis of composite exposures across the central Mojave Desert, California demonstrates that IOCG systems in this region are vertically zoned and genetically related Jurassic intrusions ranging from diorite/gabbro to granite in composition. The mineralized occurrences have intermediate depth (1–4 km), cores of magnetite±hematite mineralization with sparse Fe(-Cu) sulfides, and zone upward to acid-altered tops and downward to Fe-depleted, metal-poor, Na±Ca-altered roots. These patterns resemble those observed in IOCG systems throughout the Cordillera of the Americas.

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The social, economic, and ecological costs of plant invasions are vast, through their ability to alter ecosystem structure and function. Invasive annual grasses are a nuisance in the American Southwest through promotion of the grass-fire cycle. Annual grasses such as Bromus rubens, Bromus tectorum, Schismus barbatus, and Schismus arabicus have invaded the Mojave Desert and increased fire occurrence, thus it is important to identify and characterize the areas where persistent invasion has occurred and subsequently fire risk is increased by understanding the distribution of these invasive grasses. Previous plot and landscape-scale research has revealed anthropogenic and biophysical correlates with the establishment and dominance of invasive annual grasses in the Mojave Desert. However, these previous studies have been limited in spatial and temporal scales. Here we use a remote sensing framework to map persistent and productive populations of invasive annual grass, called hot spots, in the entire Mojave Desert ecoregion over 12 years, identify important variables for predicting hot spot distribution, and identify the most invaded subregions. Hot spots were identified in over 5% of the Mojave Desert, and invasive grasses were detected in over 90% of the desert at least once. Our results indicate that soil texture, aspect, winter precipitation, and elevation are the most important predictive variables of invasive grass hot spots, while anthropogenic variables were the least useful. The most invaded subregions of the Mojave Desert were western Mojave basins, eastern Mojave mountain woodland and shrubland, western Mojave low ranges and arid footslopes, eastern Mojave basins, and eastern Mojave low ranges and footslopes.

xxviii, 463 p. : ill., maps. A print copy of this title is available through the UO Libraries under the call number: KNIGHT F868.M65 J45 1991 / The environmental context and chronology of the transition from Early Holocene Lake Mojave to Middle Holocene Pinto cultural complexes of the southern California deserts has long been debated. This dissertation re-examines that debate, based on excavations at two major sites, and a rethinking of our most basic assumptions concerning culture change, cultural ecology, site formation processes, and dating techniques. Archaeological data recovered from two Lake Mojave/Pinto sites at Fort Irwin, in the Central Mojave Desert, were analyzed in order to track chronologically sensitive shifts in Lake Mojave-Pinto artifact assemblages through time. The archaeological assemblages recovered from Rogers Ridge and the Henwood sites were carefully analyzed into 36 depositional/analytical components for this task. Defining and chronologically ordering these assemblages required systematic consideration of artifact distributions and the development and application of 3 obsidian hydration rates based on associations with twelve 14C dates. The analysis shows that the Pinto Complex occurred in three phases. Phase I, ca. 8,200 to 7,500 BP, is marked by the addition of Pinto points to the Lake Mojave assemblage and a continuation of the basic Lake Mojave settlementsubsistence patterns. Phase II, 7,500 to 5,000 BP, is marked by the gradual disappearance of Lake Mojave points from the archaeological assemblages. Dramatic decreases in assemblage size and increases in assemblage diversity mark changing logistical strategies to infrequent and specialized site use. Phase III, 5,000 to 4,000 BP, is marked by a strong predominance of Pinto points and slightly larger assemblages. Patterns of variation among assemblages suggest that logistical strategies continued to emphasize infrequent and specialized site useage. The link between environmental change and shifting settlement-subsistence strategies was apparently relatively direct during the Pinto period, Environmental changes during the Early Holocene (11,000 to 8,000 BP) Mojave Desert led to subsistence stress among populations of the Pinto Complex. Cultural adjustments resulted in smaller human populations moving through larger home territories. It is suggested that critical thresholds in communication and mating networks were crossed which resulted in the collapse of social systems in the Mojave Desert about 7,000 BP. / Committee in charge: C. Melvin Aikens, Ann Simonds, Don E. Dumond, and William Loy

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No description available.

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.

This report describes the results of an ethnographic study performed by Cultural Systems Research, Incorporated (CSRI) for US Ecology, Inc. The study was part of US Ecology's efforts to select a site for the disposal of Low Level Radioactive Waste (LLRW) for the State of California. Dr. Stoffle and his research team were responsible for conducting the Mohave, Navajo, and Southern Paiute portions of the study.