Los depósitos minerales de la Cordillera Sur pueden asignarse a provincias metalogenéticas alineadas en dirección NNW. Estos y las rocas con las que están asociados se originaron por arcos magmáticos que migraron como respuesta a cambios en la interacción entre las placas tectónicas. El fechamiento isotópico de estas rocas estableció una secuencia cronológica de eventos geológicos que nos permite determinar las diferentes posiciones de los arcos magmáticos migrantes y construir mapas paleogeográficos. El emplazamiento de un cuerpo batolítico en la Sierra Madre del Sur durante el Pérmico (uno de los primeros eventos magmáticos) puede asociarse con el cierre del Proto-Atlántico. El primer arco magmático se estableció en la cordillera de Chiapas a Nevada y California durante el Jurásico Temprano, como indican los afloramientos que son notoriamente paralelos a la costa del Pacífico en distancias que varían desde 100 km en Chiapas a 500 km en Arizona... Para continuar, descargue el artículo completo en PDF.

New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0–10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).

It is well known that the magnetic field imbedded in the solar wind modulates the production of cosmogenic isotopes by galactic cosmic rays. Power spectral analysis yields evidence for fundamental periods relevant to this study including the Suess, Gleissberg, Hale and Schwabe cycles of ca. 210, 88, 22 and 11 years lengths. There is increasing evidence for an irradiance component accompanying each of these cycles. Assuming this is valid, we model the magnitude of irradiance change associated with these cycles that is compatible with the paleoclimate record. We conclude that the resultant model fit requires less than ±0.8‰ change in solar irradiance for each of these cycles even if we assume low climate sensitivity (0.5 °C(Wm−2)). Our solar irradiance model accounts for about 18% of 20th century global warming to 1997 and also predicts that the next maximum would occur in ad 2040 and contribute 0.2 °C to 21st century Northern Hemisphere warming.

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Temporal changes in atmospheric 14 C require high precision calibration of the radiocarbon time scale. The calibration process also provides Δ 14 C which is the age and fractionated corrected deviation of past atmospheric 14 C relative to an international standard. The dominant cause of atmospheric 14 C fluctuation is changes in the geomagnetic dipole moment. Detrending yields residual Δ 14 C which can be related to solar activity and climate change. The biogeochemical cycle of 14 C acts as a lowpass filter that greatly attenuates the high frequency components of solar activity. This attenuation is compensated by higher production rate and higher measurement precision relative to other cosmogenic isotopes. The spectrum of Δ 14 C contains many periods, overtones and combination tones. We are concerned here with the millennial and centennial periods. The Suess cycle (208 yr) and Gleissberg (88 yr) are discrete solar cycles that can be related to forcing of climate change whereas the millennial cycles do not appear to have an independent existence but are required by Fourier analysis to reconstruct the variance of the century scale cycles. We find the most effective way of demonstrating the relationship between residual Δ 14 C and climate is to match the pattern of residual Δ 14 C with the pattern of climate change.

The last decade has seen a revival of various hypotheses claiming a strong correlation between solar activity and a number of terrestrial climate parameters. Links have been made between cosmic rays and cloud cover, first total cloud cover and then only low clouds, and between solar cycle lengths and northern hemisphere land temperatures. These hypotheses play an important role in the scientific debate as well as in the public debate about the possibility or reality of a man‐made global climate change.Analysis of a number of published graphs that have played a major role in these debates and that have been claimed to support solar hypotheses [Laut, 2003; Damon and Peristykh, 1999, 2004] shows that the apparent strong correlations displayed on these graphs have been obtained by incorrect handling of the physical data. The graphs are still widely referred to in the literature, and their misleading character has not yet been generally recognized. Readers are cautioned against drawing any conclusions, based upon these graphs, concerning the possible wisdom or futility of reducing the emissions of man‐made greenhouse gases.

14 C abundance on the Earth can be modulated by both the solar wind and irradiance components of the solar cycle. The magnetic field component of the solar wind modulates 14 C production whereas the irradiance component can result in a change in the exchange rate between the various reservoirs of the carbon biogeochemical cycle. The effects would be nearly synchronous and difficult to separate. The 0.1% amplitude of irradiance variation during the two most recent solar cycles is well known. A 22-yr cycle exists also in the measured global temperature record. We have divided the University of Washington high-precision data onΔ 14 C in tree rings into three 91-yr intervals: AD 1540–1630, 1630–1720 and 1715–1805, before, during and after the Maunder Minimum. Unfortunately the AD 1540–1630 interval includes part of the Spörer Minimum as well as the intermediate interval of high solar activity. These data were analyzed by the DFT, MEM and MTM methods of spectral time series analysis. The ca. 22-yr cycle is prominent during the Maunder Minimum, whereas the 11-yr cycle is most prominent after the Maunder Minimum but totally suppressed during the Maunder Minimum. The lesser amplitude of the 11-yr cycle before the Maunder Minimum is most probably due to overlap with the Spörer Minimum. Vasiliev and Kocharov VK83 have previously suggested that the 22-yr cycle persists through the Maunder Minimum whereas the 11-yr cycle is suppressed. Our calculations show that irradiance forcing of the carbon cycle during the 11-yr cycle is negligible, so the observed 11-yr cycle inΔ 14 C must be the result of production rate changes. The presence of the 22-yr cycle and suppression of the 11-yr cycle during the Maunder Minimum is in accord with a model by Jokipii Jok91.

This compilation reports the results of 296 K-Ar analysis that were done during 1971-1991 on rock samples from throughout Arizona and, for a small number of samples, from bordering areas of adjacent states and from the Pinacate volcanic field of northwestern Sonora, Mexico. All of the reported analysis were done at the Laboratory ofIsotope Geochemistry at the Department of Geosciences, University of Arizona. Most of these dates have not been previously published. Those that have been published have not included analytical data. Some of these dates have not been released because, for various reasons, it seemed likely that they did not accurately represent rock age or cooling through the argon closure temperature. 57 pages.