Santa Cruz Island field trip: Geology, history, and research opportunities
Published:May 18, 2020
Thomas L. Davis*, Richard J. Behl†, Katie M. O’Sullivan†, Sarah Raskin, Stephen Bryne, 2020. "Santa Cruz Island field trip: Geology, history, and research opportunities", From the Islands to the Mountains: A 2020 View of Geologic Excursions in Southern California, Richard V. Heermance, Joshua J. Schwartz
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This field trip provides a rare opportunity to visit outcrops and structures that highlight the geology, history, and natural beauty of Santa Cruz Island, a remnant of prehistoric California isolated off Santa Barbara. Santa Cruz Island provides some of the most southwestward positioned subaerial outcrops of the North American landmass, while displaying a rare glimpse of prehistoric coastal southern California and picturesque and seldom accessible exposures of Tertiary strata. Most of the stops are difficult to reach and many are closed to public access. Stops 1, 9, 9B, 9C, 13, and 13B are within the Channel Islands National Park, and access to the park portion of the island is by public boat transport (Island Packers) from Ventura Harbor to Prisoners Harbor. Stop 1 is near the pier at Prisoners Harbor and easily accessible; however, the other stops require roundtrip hikes of at least 10 miles from the pier. One of the goals of this four-day trip is to visit as much of the island’s varied geology as possible. A significant body of widely recognized geologic research has been done on the island from late Quaternary sea-level and climate changes to the tectonic evolution of the western North American plate boundary, and in particular the transformation of a subduction to transform plate boundary along a continental margin. Discovery that SCI and the western Transverse Ranges have rotated ~90° clockwise since the early Miocene (Kamerling and Luyendyk, 1979, 1985; Luyendyk et al., 1980) brought on an intense period of research on the island from the late 1970s through the 1990s. Much of this work has been published in both the formal and informal literature. Two decades later, this field trip is an opportunity to review much of these additions to geologic understanding with the advantage of gains in knowledge since then. The guide will emphasize each stop’s importance, offer questions for future research, and showcase the island’s earth science educational opportunities. This four-day trip requires 4WD vehicles and includes some 3–6 km (~2–4 mile) hikes.
Dedicated to Dr. Lyndal Laughrin, Santa Cruz Island Reserve Director, Emeritus, The Sage of Santa Cruz Island
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From the Islands to the Mountains: A 2020 View of Geologic Excursions in Southern California
This volume includes five geologic field-trip guides in the Los Angeles region associated with the 2020 GSA Cordilleran Section Meeting that was scheduled for May 2020, in Pasadena, California. The guides are organized in a generally counterclockwise order around the Los Angeles Basin. The first guide by Burgette et al. provides new slip rates, age constraints, and observations of the active Sierra Madre fault zone that borders the northern side of the San Gabriel and San Fernando Valleys. The Nourse et al. guide takes a new look at the San Gabriel Mountains from a basement and geomorphologic perspective. Further west, Keller et al. provide one of the first published field-trip guides focused on the 9 January 2018 Montecito debris flows that caused 23 deaths. The volume then moves south to Santa Cruz Island, where Davis et al. provide an updated review of the island’s geology within the California borderlands. The final guide returns to the east, where Platt et al. present the unique geology of Santa Catalina Island with a focus on the subduction-related Catalina Schist.