In the Santa Clara Avenue oil field, the nonmarine Sespe Formation of Oligocene age has produced 4 million barrels of oil trapped by a Miocene mafic igneous intrusion that cuts across bedding. Throughout most of the oil field, the Miocene and older beds dip about 15° northwest. The intrusion may be related to the outpouring of Conejo Volcanics throughout much of the southern Ventura basin. The Pacific Farms #1 well penetrated 1000 feet of igneous rocks below 5100 feet, whereas wells less than 500 feet to the northwest penetrated Sespe Formation over this interval. The western wall of the intrusion is located by 10 wells which pass repeatedly through the Sespe-intrusive contact. Structure contours on the intrusive contact with the Sespe on the northwest show Redacted for Privacy that the contact varies from N20°E,80°SE in the southern portion of the field, to N90°E,85°S in the northern end of the field. The southeast wall of the intrusion is not cut by wells, but its location is controlled by a well about 1200 feet southeast of the northwest wall. If the intrusive contact is rotated to its position when it was intruded prior to tilting of the middle and late Miocene Modelo Formation, the Sespe overhangs the igneous body along a contact with a paleo-dip of 80°NW. Lateral closure in the field may be due to early Miocene normal faulting of the Sespe Formation. In the Las Posas area, two faults are documented. Both faults cut the entire Miocene section but do not cut the Pliocene-Pleistocene Pico Formation. The Miocene Vaqueros is found only on the south side of the Las Posas fault. Intra-Sespe correlations show that the upthrown block of the Las Posas fault lost to erosion 1000 feet of Sespe in addition to the Vaqueros Formation. The Epworth syncline and Beryiwood anticline were folded prior to the deposition of the Pico Formation. / Graduation date: 1986

Indiana University-Purdue University Indianapolis (IUPUI) / The objectives of this study are, generally, to analyze and understand internal processes that produce melts in an oceanic-continental subduction setting; and, specifically, to understand the assembly of a Cretaceous magmatic arc pluton (Palms pluton), including the timing of melt emplacement(s) and melt evolution from the source. SiO2 concentrations vary from ~ 69-76 % by weight. Whole rock trace element concentrations vary up to 7 times. Zircon analysis shows a minimum age difference in the pluton of 3 my, if considering the uncertainties of the oldest and youngest samples. According to the model made from the HEAT program, this is approximately six times longer than the estimated crystallization time of one batch of melt with the same physical properties as the Palms pluton. Two distinct sources, perceived from chemical analysis of premagmatic zircons, are found throughout the pluton. REE compositional patterns show a hybridization of Proterozoic and Mesozoic sources in some, but not all, Palms pluton granites. This data suggests that the pluton formed from multiple intrusions and the Proterozoic source remained relatively consistent throughout the pluton’s assembly with few additions of younger Mesozoic source material.