A recently identified mass-transport deposit stack in the Guaymas Basin, Gulf of California (México), and its implication in the basin tectonics

A large mass transport deposit (MTD) stack has been identified in the Guaymas Basin using seventeen high-resolution seismic reflection profiles and sediment core analysis. Guaymas Basin is a young, marginal basin characterized by active seafloor spreading in the central Gulf of California, Mexico. The large stack includes five distinct MTD units of variable thickness, area, and volume, characterized by a predominantly transparent seismic reflection facies with small sections of laterally discontinuous reflectors and bumpy upper and erosional lower surfaces. Based on analysis of sediment cores from Site U1551A from International Ocean Discovery Program Expedition 385, we define MTD lithofacies and use sand provenance to infer that the MTD stack originated from the Yaqui Delta region of the Sonoran margin, transporting material to the south-west. We suggest that a combination of high sedimentation rates and active tectonics contributed to the MTD events. ‘Flower structures’ observed in margin-crossing profiles indicate that the MTD stack buried a part of the transform fault separating the Guaymas Basin and the continental Sonoran margin. Seismic reflection interpretations suggest that part of the MTD stack filled the southern graben applying local stresses that drove a change of the sediment surface expression of plate spreading in the sediment-filled basin. In response to the MTD emplacement and the southern graben fill, an additional northern seafloor graben in the Guaymas Basin developed. Our results contribute to the understanding of the interactions among high sedimentation rates, continental slope stability, and active tectonics; and the influence of those interactions on the surface expression of plate spreading in the Guaymas Basin.