Guaymas Basin Stratigraphy, Event Bed Origins, and Correlation: Maximizing Results from the 4 km of Core Recovered on IODP Expedition 385

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Ocean basins form and grow through the tectonic processes of continental rifting followed by seafloor spreading. The Gulf of California (GOC) is one of few places on earth where the sediment fill and volcanic products of a young ocean basin can be obtained through seafloor drilling. Then, the basin history can be studied from recovered sediment cores. The focus of this study is ~4 km of sediment cores recovered during recent drilling and exploration of the Guaymas Basin, Central GOC, Mexico. These will be analyzed and interpreted to find out what controlled the sediment composition, how the sediment was transported and deposited, and how to match the sedimentary layers among drill sites. This study helps to train women and underrepresented minorities in geoscience, supporting a research team of three master’s degree students mentored by two female professors. The work results will be communicated to the public through outreach activities in the Santa Monica Mountains National Recreation Area. This location is the largest urban park in the United States. The project team will create new geologic field-trip materials to help visitors learn about park geology. The field-trip stops will include outcrops with marine sedimentary and volcanic rocks similar to those found in the Guaymas Basin. Lithofacies and petrofacies analyses of International Ocean Discovery Program Expedition 385 cores and integration with prior Deep Sea Drilling Project Leg 64 drilling results are necessary steps for unraveling the patterns and controls of sediment delivery and accumulation in the Guaymas Basin. Integral to this basin analysis is the definition of potential datums, volcanic ashes and other sandy event (storm, seismic) beds, that can define packages of sediment that are linkable in time across the basin, to show patterns in sediment accumulation rates. Ash and epiclastic volcanic sand-silt beds newly discovered on Expedition 385 will be fingerprinted using a variety of petrographic and imaging techniques, and their provenance further documented using analyses of their major and minor element geochemistry, and elemental composition of mineral phases. Sandy gravity-mass flow beds in the deep basin will show facies and detrital mode patterns indicative of their delivery mechanisms, for example: A) delta-front flood and mass-wasting; B) seismic-induced mass wasting along the continental slope; and C) tropical storm flushing of coastal sediment. This study, in combination with other Expedition 385 research, will make the Guaymas Basin arguably the best studied young ocean basin in the world and a model for the early sedimentary history of nascent ocean basins.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.