32-1 Signals of Tectonic and Climatic Events in Guaymas Basin Stratigraphy, Gulf of California

Session: Recent Advances in the Gulf of California Oblique Rift: Offshore and Onshore Studies // Avances Recientes en el Rift Oblicuo del Golfo de California: Estudios Marinos y Terrestres (Part II)

Presenting Author:

Authors:

Abstract:

Guaymas Basin (GB), in the Gulf of California, Mexico, is a young, transtensional marginal ocean basin characterized by thick biosiliceous to terrigenous sediments and sills that intrude the sediment fill. Descriptions of the ~4km of late Quaternary sediment core recovered at International Ocean Discovery Program Expedition 385 and Deep Sea Drilling Project Leg 64 drill sites document bed types and facies changes from the flank of a volcano, across a transform margin, in the pro-delta basin floor and deep central graben, and transecting a basin floor methane vent. The basin is seismically active and traversed by tropical storms with potential for event bed generation recorded in the basin fill which could be used for intersite correlation.  Core X-radiographs provide insight into the origin of these beds.

Cores from two sites near the northern transform margin are mainly biosiliceous mud characterized by a variety of silty to sandy laminae/thin beds of varying composition. The origin(s) of these are a focus of this study.  Maxima of event bed occurrences in the cores (~number/10m of core) at both sites correspond to previously dated, precession-controlled cycles of rapid alluvial-fan deposition documented onshore in Baja California that are attributed to increased tropical storm intensity and frequency by Antinao et al. (2016). Thus, these maxima could be attributed to enhanced storm activity augmenting average “background” bed/laminae generating events.

IODP cores also provide insights into the composition and structure of several GB MTDs identified in seismic profiles. At the base of the Yaqui Delta front and in the central western graben cored facies include massive (mud or sand) or variably deformed lithologies, and thick mud-dominated, graded to massive, mass-gravity flow deposits. These lithofacies are consistent with the seismic MTD interpretation based on comparison with outcrop examples of mass transport deposits (MTDs) described in the literature.

One unique bed type is observed throughout the basin in both IODP and DSDP cores, as first described by shipboard scientists. These beds feature abrupt-based, silty to sandy intervals overlain by thick, graded to massive beds of mixed biosiliceous and terrigenous mud capped by diatom ooze.  They are similar to “homogenite” or “megaturbidite” beds described in the central Mediterranean Sea which have been linked to seismic-generated tsunami activity also associated with MTDs. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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