The PIs will construct a series of digital GIS-based paleotectonic and paleogeographic maps that will track development of the Gulf of California - Salton Trough plate boundary in 2-million-year increments from 14 Ma to the present. One set of maps will be made for the period from 6 Ma to the present - a time for which the rate of relative plate motion and the total amount of plate-boundary offset are widely agreed upon. Two sets of maps will be developed for the period from 14 to 6 Ma to highlight two contrasting end-member models for the timing of rift initiation, marine incursion, total offset across the Gulf, and kinematics of plate boundary development: (1) modified strain-partitioning model, with marine incursion into the southern Gulf at ~8 Ma and into the northern Gulf at ~6 Ma; and (2) non-partitioned, integrated regional strain with marine incursion as early as ca. 12 Ma. Using this approach, the PIs will fully explore the numerous implications and predictions of the two end-member models and suggest new data that will be needed to address this major unresolved controversy in future studies. The reconstructions will highlight both recent advances in understanding as well as unresolved controversies. They hope that the map reconstructions will also challenge the research community to develop rigorous testable hypotheses for future work that will explore the underlying processes of continental rifting, birth of an ocean basin, and the possible role of strike-slip and/or transtensional strain in modulating those processes. This kind of synthesis of the Gulf of California-Salton Sea was recommended by the MARGINS review panels/program.
Broader impacts of the synthesis represent an important service to a broader Earth science community. It will enhance both research and education and will be available for instructors in Earth and environmental sciences and to the general public for potential ecotourism sites in the region. Graduate students will gain experience with collaborative scientific research, improve their GIS skills, and increase their knowledge of the focus site in general.
This research was designed to advance the methods that geoscientists use to create reconstructions of past regions and paleo-tectonic and paleogeographic maps of tecotnically complex regions. It was specifically aimed at using ArcGIS software to make maps of the Gulf of California to Salton trough plate tectonic boundary zone since it formed at 12 million years ago. Our primary results are that we favor an intermediate model for the total movement of Baja California away from mainland Mexico of about 400 kilometers in the south and about 360 km in the north. Our reconstructions and review of the literature suggest that the early Gulf of California seaway formed in jumps from south to north with major jumps from the Farallon basin to the Guaymas basin at 7.5 million years, and a final major jump to form a surprisingly narrow and long seaway at 6.5 - 6 million years ago. The next result is that even though the rupture of the continent in the Gulf of California occurred rapid (geologically), it took many million years for the main extension to localize along the individual spreading centers that currently form the southern plate boundary. The plate boundary localized in the southern Gulf by consistently forming spreading centers in the western of many pairs of basins along individual rift domains - this favoring of the western basins nearer the Baja California peninsula remains a muystery in terms of its cause.
