The 13C/12C ratio in human collagen was determined for 19 individuals from Hopewell sites in Wisconsin, Illinois, and Ohio and compared with 27 new measurements from individuals of Archaic, Mississippian, and Late Woodland affiliation. Additional measurements were made of elements in the food chain and on experimental animals fed on a diet of known composition containing maize. The similarity of the Hopewell measurements to those of nonmaize diets indicates that corn was of little importance in the Hopewell diet for those populations tested.
On the basis of field observations and theoretical studies it is believed that the dense pall of local dust over northwestern India and West Pakistan is a significant factor in the development of subsidence over the desert. Archeological evidence derived from the northern portion of the desert within India suggests a pattern of intermittent occupation with the role of man being important in making the desert. As man has made the desert, so through surface stabilization can he reduce the dust and consequently modify the subsidence and precipitation patterns in the region. The social consequences of such climatic modification are briefly considered.
Procedures and equipment have been described in previous date lists. Except as otherwise indicated, wood, charcoal and peat samples are pretreated with dilute NaOH and dilute H: PO.I before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HC1 instead of HYO4.The dates reported have been calculated using 5568 as the half-life of '4C with 1950 as the reference year. The standard deviation quoted includes only the 1o-of the counting statistics of background, sample, and standard counts. Background methane is prepared from anthracite, standard methane from NBS oxalic acid. The activities of the dated samples for which 813C values are listed have been corrected to correspond to a 813C value of -25%0.Sample descriptions are based on information supplied by those who submitted samples. ACKNOWLEDGMENTS
Procedures and equipment of the laboratory have been described in previous date lists. Wood, charcoal, and peat samples are pretreated with dilute NaOH and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous samples are treated with dilute HCl instead of H3PO4.
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