Collaborative Research: Testing hypotheses of latest Pleistocene paleo-environmental collapse, Northern Channel Islands, California

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Testing a Hypothesis of Latest Pleistocene Paleo-environmental Collapse, Northern Channel Islands, CaliforniaThis research will describe the nature and timing of dramatic paleo-environmental changes that occurred on the Northern Channel Islands (NCI) of California during the latest Pleistocene. In particular, we will test the primary hypothesis that deforestation of the islands, fluvial aggradations, landsliding, and widespread burning were synchronous events caused by a sharp change in fire regime - per haps associated with the arrival of the first humans and the extinction of mammoths. Other secondary hypotheses will be tested, including changes caused by gradual climate change, gradual climate-driven increases in fire frequency, ecosystem reduction due to sea-level rise, or an impact event at ~13ka. Recent research on the NCI has seen a growing convergence in the ages of key events around 13, 00 cal yBP, including (1) a paleobotanical shift from conifer cover to non-arboreal vegetation, (2) onset of lowland aggradations, (3) Pleistocene landsliding: (4) deposition of charcoal and disseminated carbon; (5) arrival of the first humans, and (6) extinction of mammoths on the NCI. Another research group has suggested an impact event at ~12.9 ka. This work will test these hypotheses through: detailed description of the stratigraphy of latest Pleistocene sequences, OSL and radiocarbon dating, palynology and paleobotany, local mapping of the post-OIS2 transgression, characterization of charcoal deposition, and systematic sampling of microspherules and other potential extraterrestrial indicators through the latest Pleistocene-Holocene sequence. Fire is a documented mechanism by which small numbers of humans may have large impacts on natural systems. Regional anthropogenic environmental impacts at the vanguard of human migration into the New World might imply a timing and magnitude not previously recognized.