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

Stratigraphy and paleontology of Pliocene-Pleistocene strata at Punta Perico, Baja California Sur

Paper number: 17-6
Program: Technical Sessions
Time: 10:50 AM – 11:05 AM

Authors

Abstract

The opening of the Gulf of California created unique marine ecosystems characterized by high endemism and complex oceanographic dynamics. This study aims to characterize the stratigraphy and biodiversity of an as yet undocumented Pliocene-Pleistocene succession at Punta Perico, east of La Paz, Baja California Sur. The research involved detailed stratigraphic logging and geological mapping of conglomerate, calcarenite, and coquina that unconformably overlies an eroding granodioritic basement.

Using an integrated approach of field observations, macrofossil collections, and sediment screening for micromollusks within carefully measured stratigraphic sections, we revealed more than 100 species of macroinvertebrates. The fauna is dominated by bivalves and gastropods, in addition to decapods, clypeasteroids, and scattered marine vertebrates (isolated shark, ray, and marine mammal elements). Lithofacies and macrofossil paleoecology indicate a coastal onlap sequence with fluctuations between nearshore and offshore depositional environments. Periodic high-energy conditions are evidenced by poorly sorted clastic sediments and crushed rhodolith beds, indicating localized transport by recurrent storm events. A precise and finely resolved age for the extensive coastal section is difficult because of a lack of well-established biostratigraphic index fossils, but the echinoid Clypeaster bowersi and associated pectinid bivalves draws comparison with assemblages on nearby Ceralvo Island, supporting a middle to upper Pliocene age for basal strata. A lack of Pliocene index fossils in the conformably overlying upper part of section points to a likely early Pleistocene age for those strata. The distinctive indurated Pliocene-Pleistocene unit is unconformably overlain by Quaternary terrace deposits in a number of locations.

While containing several extinct taxa, the Punta Perico assemblage is fairly modern in composition, suggesting that it marks a transition between typical Pliocene faunas of the proto Gulf of California and those more characteristic of the Pleistocene. A comparison with assemblages of overlying Quaternary terrace deposits provides a clear contrast between this proto-Gulf and modern fauna.  

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

doi: 10.1130/abs/2026CD-410961

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