T72 Tectonics and Sedimentation of the Central Gulf of California, Mexico, and Surrounding Regions

Sunday, 22 September 2024
1:30 PM - 5:30 PM
303A

IODP DRILLING DURING EXPEDITION 385 SHOWS GUAYMAS BASIN TO BE GOLDEN: EXCITING INSIGHTS INTO THE WORKINGS OF A YOUNG, OBLIQUELY RIFTED, ACTIVE CONTINENTAL MARGIN

Paper number: T72-4
Program: Technical Sessions
Time: 2:10 PM – 2:25 PM

Authors

Abstract

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 two surficial grabens and subsurface sills developed in the sediment fill both within and beyond the axial grabens. 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. A broad overview of the basin and its workings is presented through the lens of shipboard discoveries and post-cruise research. 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!

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402895

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