17 Paleoceanography and paleoclimate of the Gulf of California and how they resonate with the evolution of other marginal seas

This session features studies on the climatic and marine history of the Gulf of California and its connections to the global climate and ocean system, utilizing multidisciplinary geological, micropaleontological, geochemical, and numerical modeling proxies.

Thursday, 23 April 2026
9:30 AM - 12:00 PM
LMH, Deli

BIODIVERSITY OF MARINE TERRACES AT BAHIA COYOTE, BAJA CALIFORNIA SUR AND AN EXPLORATION OF LATE PLEISTOCENE BIOGEOGRAPHY IN THE GULF OF CALIFORNIA

Paper number: 17-7
Program: Technical Sessions
Time: 11:05 AM – 11:20 AM

Authors

Abstract

Extensive marine terrace deposits exposed along the coastal plain of Bahia Coyote, near La Paz on the shores of the Gulf of California, in Baja California Sur, have not been adequately documented with respect to their apparent rich macrofossil biodiversity to date. These marine deposits vary in thickness across Bahia Coyote, reflecting deposition in pre-existing erosional channels, depressions in the Pleistocene landscape, and the development of Porites-dominated coral bioherms. Sedimentary facies include cobble conglomerates with oyster shells, poorly bedded molluscan-rich bioclastic sands and coral rubble, massive Porites in growth positions, rhodolith-rich bioclastic sands, and oyster mounds are encountered.

The faunal composition of these terraces was surveyed by the authors through collection of hand specimens, bulk samples, and field observations. Collectively this effort has resulted in the documentation of 304 species of mollusks, including 159 gastropods, 138 bivalves, 6 scaphopods, and a single chiton. Other fauna recognized at this site include corals, echinoderms, decapods and barnacles. U/Th dating of corals in this marine terrace suggest deposition during the last interglacial, marine isotope stage (MIS) 5e sea level high stand.

Collectively this is the most diverse Quaternary fauna in the southern Gulf of California, and one of the most diverse in the broader Baja California region. The Bahia Coyote assemblage has high similarity with both Quaternary and modern faunas of the Central and Southern gulf biogeographic regions, and little similarity with that of the Pacific coast of the southern Baja peninsula. The extraordinary diversity of the Bahia Coyote terraces is the result of excellent preservation and accordingly high assemblage-level richness, but also the wide range of depositional environments preserved throughout the study area, which included patch reefs, oyster mounds, subtidal rhodolith beds, subtidal and intertidal boulder shorelines, and lagoonal, nearshore, and beach sands. Most taxa are associated with nearshore and lagoonal sands, or rocky intertidal settings, but notably also mangrove and coral reef habitats.

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

doi: 10.1130/abs/2026CD-410996

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