Abstract
Along most of the Pacific Coast of North America, sand dunes are dominantly silicate-rich. On the California Channel Islands, however, dunes are carbonate-rich, due to high productivity offshore and a lack of dilution by silicate minerals. Older sands on the Channel Islands contain enough carbonate to be cemented into aeolianite. Several generations of carbonate aeolianites are present on the California Channel Islands and represent the northernmost Quaternary coastal aeolianites on the Pacific Coast of North America. The oldest aeolianites on the islands may date to the early Pleistocene and thus far have only been found on Santa Cruz Island. Aeolianites with well-developed soils are found on both San Miguel Island and Santa Rosa Island and likely date to the middle Pleistocene. The youngest and best-dated aeolianites are located on San Miguel Island and Santa Rosa Island. These sediments were deposited during the late Pleistocene following the emergence of marine terraces that date to the last interglacial complex (~ 120,000 yr to ~ 80,000 yr). Based on radiocarbon and luminescence dating, the ages of these units correspond in time with marine isotope stages [MIS] 4, 3, and 2. Sea level was significantly lower than present during all three time periods. Reconstruction of insular paleogeography indicates that large areas to the north and northwest of the islands would have been exposed at these times, providing a ready source of carbonate-rich skeletal sands. These findings differ from a previously held concept that carbonate aeolianites are dominantly an interglacial phenomenon forming during high stands of sea. In contrast, our results are consistent with the findings of other investigators of the past decade who have reported evidence of glacial-age and interstadial-age aeolianites on coastlines of Australia and South Africa. They are also consistent with observations made by Darwin regarding the origin of aeolianites on the island of St. Helena, in the South Atlantic Ocean, more than a century and a half ago.
| Original language | English |
|---|---|
| Pages (from-to) | 38-76 |
| Number of pages | 39 |
| Journal | Palaeogeography, Palaeoclimatology, Palaeoecology |
| Volume | 491 |
| DOIs | |
| State | Published - 1 Feb 2018 |
| Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2017
Funding
This study was supported by the Climate and Land Use Change Research and Development Program of the U.S. Geological Survey (USGS) and is a contribution to the “Geologic Records of High Sea Levels” Project. Sincere thanks go to the U.S. National Park Service, Channel Islands National Park, and Kate Faulkner in particular, for field access and logistical support. Ian Williams, George Roberts, Lulis Cuevas, Mark Senning, Ed Smith, Sarah Chaney, Dave Begun, and Kelly Minas (all U.S. National Park Service) were knowledgeable and gracious hosts who assisted with field work during our many trips to San Miguel Island, Santa Rosa Island, and Santa Cruz Island. DeAnna Laurel (Colorado State University) and Sabine Faulhaber (NPS volunteer, then of UCSB) assisted with field work. Thanks go to Dave Loope (University of Nebraska-Lincoln) who examined our photographs of hypothesized mammoth tracks and confirmed their likely origin. A very special thank-you goes to our good friend and retired USGS colleague Jack McGeehin, who generated all of the radiocarbon ages presented here. Bob Halley (USGS, retired), editor Paul Hesse, John Wehmiller (University of Delaware), an anonymous reviewer, and Janet Slate (USGS) all made helpful comments on an earlier version of the manuscript, which we appreciate. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government.
| Funders | Funder number |
|---|---|
| Geologic Records of High Sea Levels | |
| U.S. Geological Survey |