Modern Radiocarbon Levels for Northwestern Mexico Derived from Tree Rings: A Comparison with Northern Hemisphere Zones 2 and 3 Curves
AuthorBeramendi-Orosco, Laura E.
Santos-Arevalo, Francisco J.
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CitationBeramendi-Orosco, L. E., Gonzalez-Hernandez, G., Villanueva-Diaz, J., Santos-Arevalo, F. J., Gómez-Martinez, I., Cienfuegos-Alvarado, E., ... & Urrutia-Fucugauchi, J. (2010). Modern radiocarbon levels for Northwestern Mexico derived from tree rings: A comparison with Northern Hemisphere zones 2 and 3 curves. Radiocarbon, 52(3), 907-914.
DescriptionFrom the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.
AbstractThe radiocarbon variation for northwestern Mexico during the period 1950-2004 was studied by accelerator mass spectrometry (AMS) and liquid scintillation counting (LSC) analyses of tree rings. Two tree-ring sequences of Pseudotsuga menziesii, sampled in a site isolated from urban centers and active volcanoes (26.18 degrees N, 106.3 degrees W, 3000 m asl), were dendrochronologically dated and separated in annual rings prior to 14C analysis. Results obtained show a similar profile to the values reported for the Northern Hemisphere (NH), having significant correlation coefficients with the compilation curves for NH zone 2 (r = 0.987, p < 0.001) and NH zone 3 (r = 0.993, p < 0.001). The maximum peak is centered at 1964.5 with a ∆14C value of 713.15 +/- 9.3‰. The values obtained for the period 1958-1965 are lower than zone 2 values and higher than zone 3 values. For the period 1975-2004, the values obtained are higher than the NH compilation curve and other NH records. We attribute the first divergence to the North American monsoon that may have carried 14C-depleted air from the south during the summer months; the second divergence may be attributable to 14C-enriched biospheric CO2.