Re-evaluating the origins of late Pleistocene fire areas on Santa Rosa Island, California, USA

Abstract

At the close of the Pleistocene, fire regimes in North America changed significantly in response to climate change, megafaunal extinctions, anthropogenic burning and possibly, even an extraterrestrial impact. On California's Channel Islands, researchers have long debated the nature of late Pleistocene “fire areas,” discrete red zones in sedimentary deposits, interpreted by some as prehistoric mammoth-roasting pits created by humans. Further research found no evidence that these red zones were cultural in origin, and two hypotheses were advanced to explain their origin: natural fires and groundwater processes. Radiocarbon dating, X-ray diffraction analysis, and identification of charcoal from six red zones on Santa Rosa Island suggest that the studied features date between ~ 27,500 and 11,400 cal yr BP and resulted from burning or heating, not from groundwater processes. Our results show that fire was a component of late Pleistocene Channel Island ecology prior to and after human colonization of the islands, with no clear evidence for increased fire frequency coincident with Paleoindian settlement, extinction of pygmy mammoths, or a proposed Younger Dryas impact event.

Fluvial sedimentary history of Arlington Canyon, Channel Islands National Park, California

“…The alluvial sediments in Arlington Canyon also contain numerous burned zones dating to the Pleistocene, as described above. Their presence, along with abundant charcoal dating to before the arrival of humans to the Channel Islands, underscores the findings of other researchers that fires represented in the sedimentary record of SRI and other Channel Islands were a part of natural cycles, rather than caused by humans (Johnson, ; Scott et al , ; Rick et al , ; Pigati et al , ; Hardiman et al , ). Additionally, the presence of charcoal in Pleistocene sediments and its relative absence in Holocene sediments likely reflects the change from a forested to a dominantly grassland environment (Anderson et al , ; Hardiman et al , ; Scott et al , ).…”

“…Quaternary Sci., Vol. 34(7) 499-508 (2019) the sedimentary record of SRI and other Channel Islands were a part of natural cycles, rather than caused by humans (Johnson, 1977;Scott et al, 2011;Rick et al, 2012;Pigati et al, 2014;Hardiman et al, 2016). Additionally, the presence of charcoal in Pleistocene sediments and its relative absence in Holocene sediments likely reflects the change from a forested to a dominantly grassland environment (Anderson et al, 2010;Hardiman et al, 2016;Scott et al, 2017).…”

“…However, recent surveys of more than 160 mammoth localities on the northern Channel Islands have failed to identify a single mammoth kill site or any mammoth bones exhibiting clear evidence of human butchery (Agenbroad et al , ). Although an alternative explanation for the origin of the red zones has been proposed (e.g., Cushing et al , ; Cushing, ), field observations and laboratory analyses by other researchers have demonstrated conclusively that most of the fire areas on the Channel Islands are indeed the result of thermal alteration of soil and burning of logs, shrubs, or other vegetation (Johnson et al , ; Wendorf, ; Scott et al , ; Rick et al , ; Pigati et al , ; Hardiman et al , ). Additionally, the ages of many fire areas predate the earliest known human occupation of the Channel Islands, indicating that, despite the low incidence of lightning‐induced fires in southern California today, naturally caused wildfires were relatively common on the islands during the late Pleistocene (Johnson, ; Scott et al , ; Rick et al , ; Pigati et al , ; Hardiman et al , ).…”

Evidence of Repeated Wildfires Prior to Human Occupation on San Nicolas Island, California

“…Wendorf (1982) reached the same conclusion shortly after Don conducted his research. A carefully conducted recent study that combined detailed stratigraphy, radiocarbon dating, paleobotany, and clay mineralogy reached the same conclusions about the fire areas on Santa Rosa Island (Rick et al 2012). Anderson et al (2010) reported evidence of Native American burning on Santa Rosa Island which increased in the late Holocene.…”

From forest fires to fisheries management: Anthropology, conservation biology, and historical ecology

“…Phil Orr argued that ancient peoples hunted mammoths, then cooked and processed them in mammoth fire‐roasting pits, some of which may have been 40,000 or more years old . These roasting pits or “fire areas” left reddish soil stains, some containing animal bones and other materials, which were later determined to be the result of either natural wildfires that burned through an area, or less likely staining from groundwater processes . Although the anthropogenic origins of the fire areas did not stand the test of time, more recent studies suggest that human‐induced burning may have increased during the Late Holocene, particularly after about 4,000 years ago on the Channel Islands .…”