Earth Sciences Seminar Series
Friday October 11, 2024
12:30PM
McHugh 301
IODP DRILLING YIELDS EXCITING INSIGHTS INTO THE WORKINGS OF A YOUNG, OBLIQUELY RIFTED, ACTIVE CONTINENTAL MARGIN
The Gulf of California (GOC) marks a young transtensional plate boundary in western Mexico between the North American and Pacific plates. Obliquely rifted continental margins such as this are rare today, but thought to have been more common in the past—for example, during the Mesozoic development of the Atlantic Ocean. Study of the older margins is hindered by subsidence and thick sediment cover, so less sedimented GOC basins are more accessible analogues. Deep sea exploration through scientific ocean drilling in the GOC has focused in the centrally located Guaymas Basin, first in 1978 on the Glomar Challenger during Deep Sea Drilling Project (DSDP) Leg 64 and later in 2019 on the JOIDES Resolution during International Ocean Discovery Program (IODP) Expedition 385. In this basin, seafloor spreading is manifested in surficial graben and subsurface sills developed in the sediment fill. Leg 64 was renowned for recovering the first ~150 m of hydraulically-piston-cored (HPC) sediment at Site 480 on the Sonoran slope. Forty years later, Expedition 385 scientists marveled at the same fine mm-scale lamination preserved in HPC-cored biosiliceous sediment fill of the basin. Sites drilled during DSDP Leg 64 on the northern continental slope as well as across the northern and southern grabens were augmented during Expedition 385 by a series of eight sites (~4 km of recovered core). They link north to south and expand east to west—far from the spreading center—providing a broader picture of basin sedimentation and off-axis magmatism. This deeper and more extensive view provides new insights into the nature and distribution of sedimentary facies and volcanism in the basin, including sill-sediment contact zones and gravity-mass flow deposits. Such event beds warrant further study, as they are potentially linked to seismic and storm processes acting across the narrow confines of the Gulf of California. I will present a broad overview of the basin and its workings through the lens of shipboard discoveries and post-cruise research, including that of my students and colleagues. These studies might suggest that Guaymas is the “Goldilocks” Basin of the Gulf of California: you decide if it is just right or too much of a good thing!
For more information, contact: Christin Donnelly at christin.donnelly@uconn.edu