http://hdl.handle.net/2027.42/55461 2013-05-19T06:42:57Z http://hdl.handle.net/2027.42/97754 Assessing the role of the San Andreas fault in controlling the spatial distribution of erosion rates in the Transverse Ranges, Southern California Mueller, Megan In considering erosion rate controls, previous work has focused primarily on the geomorphic factors; here tectonic controls, particularly seismic shaking, are additionally considered, given the growing recognition that earthquakes may play a key role in generating landslides and erosion. We present new cosmogenic radionuclide data from the San Gabriel Mountains, combined with previously published data from the San Gabriel and San Bernardino Mountains, to resolve the parameters controlling erosion. Statistical analysis of erosion rate parameters reveals that one of the primary erosion rate controls in the San Gabriel and San Bernardino Mountains is catchment distance from the San Andreas fault, an analog for seismic shaking from the San Andreas fault. We hypothesize that seismically induced erosion plays a significant role in the sediment budget of the San Gabriel and San Bernardino Mountains. Thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Geological Sciences, with Honors. Department of Earth and Enviromental Sciences 2013-05-17T00:00:00Z http://hdl.handle.net/2027.42/97753 Permian Secular Variation of the Ayaguz formation in Kazakhstan Menzo, Zachary This study uses 60 individual volcanic flows from the Early Permian in eastern Kazakhstan with the intention of analyzing to what extent secular variation of the geomagnetic field may be reduced during the Kiaman (Permo-Carboniferous) Reversed Polarity Superchron (KRPS). Such a study can be important because the confirmation of a relationship between secular variation and polarity reversal frequency during the Permian would allow for the use of paleosecular variation (PSV) data to infer the dynamo stability in the past, something that is currently not possible for times earlier than 160 Ma. The samples analyzed for the study were collected from a thick pile in the Chingiz Range of NE Kazakhstan with a U/Pb age of 283±2.4 Ma. The resulting data were compared to the data obtained by Dr. Bazhenov, who collected samples from the same volcanic pile for a parallel investigation. Nearly all of the paleomagnetic directions obtained in thermal demagnetization are seen to be SW and up, with a mean paleopole position at longitude (331.4E), and south-latitude (-37.9) confirming the expected mean Permian pole position. The resulting data also matched the anticipated high precision parameter (49.4), indicative of a stable geodynamo. This study therefore validates the correlation between secular variation and polarity reversal frequency. Thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Geological Sciences, with Honors. Department of Earth and Enviromental Sciences 2013-05-17T00:00:00Z http://hdl.handle.net/2027.42/97752 Insights into the Position of Kyrgyzstan in the Silurian Mohd Razak, Syamil This study examined 101 cores from 16 basaltic flows from the Silurian in northern Kyrgyzstan with the aim of understanding the paleoposition of Kyrgyzstan. This is important as very little is known about the Kazakhstania terranes which comprises Kyrgyzstan in the early to middle Paleozoic. The result of this study may help us understand the amalgamation process of the island arcs and microcontinents that were thought to have joined together in the Ordovician. The magnetic behavior of the cores from this collection seems to suggest that both hematite and low-titanium magnetite are present as the magnetic carrier. Characteristic magnetization is carried by low-titanium magnetite while secondary magnetization is prominent and carried by hematite. The magnetic behavior of samples with hematite could reflect ancient magnetic directions but are poorly clustered. In contrast, samples with magnetite show steep magnetic directions that resemble Cenozoic magnetizations. To increase accuracy and credibility of the data, visual inspection and reliability criteria of Van der Voo (1990) were used to filter highly erroneous samples. Overall formation mean of the study sites gave paleomagnetic directions that are southerly and up and northerly and down. Scattered directions are present owing to undefined folding events and complicated tectonic history in the study area. U-Pb radiometric age analysis of zircon from the basalt revealed an age of 423 ± 5.4Ma with a confidence level of 96.1%. The expected direction from volcanic rocks of this locality is not steep if the age is Silurian; however this study has obtained both steep and shallow directions with noisy behavior in thermal demagnetization and failing a fold test. We attribute this disappointing remanence to late-stage alteration. By considering only characteristic magnetic directions, the final mean of site directions was calculated to have declination and inclination of 181.7° and -86.6° respectively with the a95 of 12.3° which does not agree with an expected direction of Silurian age. Thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Geological Sciences, Honors. Department of Earth and Enviromental Sciences 2013-05-17T00:00:00Z http://hdl.handle.net/2027.42/96849 Don't Leave Me Hanging: Read transparency in texting and response time Herson, Melanie