THE HOMOGENEITY (OR LACK THEREOF) OF THE DIKES OF THE WESTERN SANTA MONICA MOUNTAINS, CALIFORNIA

The Conejo Volcanics are a series of basaltic-dacitic deposits created by transtensional tectonics during the middle Miocene - the stratigraphy of which is cut by a series of hypabyssal dikes. This study attempted to validate prior observations on the dikes’ origin by assessing their orientations and mineralogy. The strikes and dips of 31 dikes across the western Santa Monica Mountains were measured, three of which were sampled for thin section analysis. A strong correlation in dike orientation was observed, suggesting that they came from a similar source. However, their compositions were highly variable, suggesting the chemistry of this magma source evolved over time.