Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilis and Mammuthus columbi), Channel Islands National Park, California, USA

Authors

Daniel R. Muhs, U.S. Geological SurveyFollow
Kathleen R. Simmons, U.S. Geological SurveyFollow
Lindsey T. Groves, Natural History Museum of Los Angeles County
John McGeehin, US Geological Survey
R. Randall Schumann, U.S. Geological Survey
Larry D. Agenbroad, Mammoth Site of Hot Springs, South Dakota, Inc

Date of this Version

2015

Citation

Quaternary Research 83 (2015) 502–521

doi 10.1016/j.yqres.2015.03.001

Comments

US government work

Abstract

Fossils of Columbian mammoths (Mammuthus columbi) and pygmymammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace withMIS 5.1, a time of relatively high sea level.Mammoths likely immigrated to the islands by swimming during the glacial periodsMIS 6 (~150 ka) orMIS 8 (~250 ka),when sea levelwas lowand the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/ Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.