FOSSIL VERTEBRATES FROM PLEISTOCENE TERRESTRIAL DEPOSITS ON THE NORTHERN CHANNEL ISLANDS, SOUTHERN CALIFORNIA

Author(s):  
Daniel A. Guthrie
1995 ◽  
Vol 60 (2) ◽  
pp. 287-308 ◽  
Author(s):  
L. Mark Raab ◽  
Katherine Bradford ◽  
Judith F. Porcasi ◽  
William J. Howard

Marine paleotemperature is a significant factor in the subsistence productivity of many coastal regions and may be an important factor in the evolution of maritime societies. A California paleotemperature model, spanning 8,000 calendar years, correlates periods of high sea surface temperatures with decreased marine subsistence productivity. A recent case study involving this model identified warming conditions between A.D. 1150 to 1300 as a major cause of subsistence distress for dwellers of the northern Channel Islands. These results are questionable, based on a comparison with data from other sites and periods of high sea temperature. Research at the Little Harbor site, one of the most extensively researched in the Channel Islands, shows that high sea temperature about 5,200 calendar years ago may have introduced warm-water faunas but not starvation conditions. Evidence from other sites occupied during subsequent warming cycles, including the event between A.D. 1150 to 1300, points to similar conclusions. Understanding the effects of long- and short-term ocean temperature cycles, a focus on only a small segment of the Holocene paleotemperature curve, and weak evidence that food abundance was affected by sea temperature are problems that must be overcome before the validity of the paleotemperature model can be accepted.


1986 ◽  
Vol 26 (2) ◽  
pp. 207-217 ◽  
Author(s):  
John Cushing ◽  
Adrian M. Wenner ◽  
Elmer Noble ◽  
Marla Daily

Pleistocene areas of red sediments and carbonized vegetation on the Northern Channel Islands, California, have in the past been interpreted as caused by fires of either natural or human origin. Some are associated with darkened mammoth and bird fossils, and these fossils have been considered as having been burned by early man. Reevaluation of these so-called “fire areas” indicates that the above phenomena are the result of low-temperature (≤100°C), nonheating processes occurring in groundwater. Evidence for this conclusion is derived from field observations on fossil carbonized vegetation, and the geology of the areas. Additional evidence derives from experiments on the red sediments and fossil wood, X-ray diffraction analyses, magnetic analyses, studies on the clay minerals smectite and illite, and the demonstration that fossil mammoth bone contains sufficient Fe and Mn to account for their discoloration. Much of the carbonization of vegetation probably occurred in water rather than in fire. Radiocarbon dates from the islands will probably need to be reevaluated. These data provide evidence contrary to the concept of the occurrence of significant fires, either natural or set by early man, on the Northern Channel Islands.


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