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Modern Radiocarbon Levels for Northwestern Mexico Derived from Tree Rings: A Comparison with Northern Hemisphere Zones 2 and 3 Curves

Published online by Cambridge University Press:  18 July 2016

Laura E Beramendi-Orosco*
Affiliation:
Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico DF 04510, Mexico
Galia Gonzalez-Hernandez
Affiliation:
Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico DF 04510, Mexico
Jose Villanueva-Diaz
Affiliation:
Instituto Nacional de Investigaciones Forestales y Agropecuarias, CENID-RASPA, Gomez Palacio, Durango 35140, Mexico
Francisco J Santos-Arevalo
Affiliation:
Centro Nacional de Aceleradores (CNA), Avda. Thomas Alva Edison 7, Isla de la Cartuja, Seville 41092, Spain
Isabel Gómez-Martinez
Affiliation:
Instituto Nacional de Investigaciones Forestales y Agropecuarias, CENID-RASPA, Gomez Palacio, Durango 35140, Mexico
Edith Cienfuegos-Alvarado
Affiliation:
Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico DF 04510, Mexico
Pedro Morales-Puente
Affiliation:
Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico DF 04510, Mexico
Jamie Urrutia-Fucugauchi
Affiliation:
Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico DF 04510, Mexico
*
Corresponding author. Email: laura@geofisica.unam.mx.
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Abstract

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The 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°N, 106.3°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 δ14C 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.

Information

Type
Calibration, Data Analysis, and Statistical Methods
Copyright
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