Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion

Pacific drill sites offshore Central America provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the Neogene. The temporal distribution of tephra layers established by tephrochonostratigraphy in Part 1 indicates a nearly continuous highly explosive eruption record for the Costa Rican and the Nicaraguan volcanic arc within the last 8 M.y. The widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large-magnitude explosive eruptions along the southern Central American Volcanic Arc (CAVA). We observe three pulses of enhanced explosive magmatism between 0-1 Ma at the Cordillera Central, between 1-2 Ma at the Guanacaste and at >3 Ma at the Western Nicaragua segments. Averaged over the long-term the minimum erupted magma flux (per unit arc length) is ∼0.017 g/ms. Tephra ages, constrained by Ar-Ar dating and by correlation with dated terrestrial tephras, yield time-variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion. The peak rate at >2.3 Ma near Osa particularly relates to initial Cocos Ridge subduction which began at 2.91±0.23 Ma as inferred by the 1.5 M.y. delayed appearance of the OIB geochemical signal in tephras from Barva volcano at 1.42 Ma. Subsequent tectonic re-arrangements probably involved crustal extension on the Guanacaste segment that favored the 2-1 Ma period of unusually massive rhyolite production

Structure and serpentinization of the subducting Cocos plate offshore Nicaragua and Costa Rica

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 12 (2011): Q06009, doi:10.1029/2011GC003592.The Cocos plate experiences extensional faulting as it bends into the Middle American Trench (MAT) west of Nicaragua, which may lead to hydration of the subducting mantle. To estimate the along strike variations of volatile input from the Cocos plate into the subduction zone, we gathered marine seismic refraction data with the R/V Marcus Langseth along a 396 km long trench parallel transect offshore of Nicaragua and Costa Rica. Our inversion of crustal and mantle seismic phases shows two notable features in the deep structure of the Cocos plate: (1) Normal oceanic crust of 6 km thickness from the East Pacific Rise (EPR) lies offshore Nicaragua, but offshore central Costa Rica we find oceanic crust from the northern flank of the Cocos Nazca (CN) spreading center with more complex seismic velocity structure and a thickness of 10 km. We attribute the unusual seismic structure offshore Costa Rica to the midplate volcanism in the vicinity of the Galápagos hot spot. (2) A decrease in Cocos plate mantle seismic velocities from ∼7.9 km/s offshore Nicoya Peninsula to ∼6.9 km/s offshore central Nicaragua correlates well with the northward increase in the degree of crustal faulting outboard of the MAT. The negative seismic velocity anomaly reaches a depth of ∼12 km beneath the Moho offshore Nicaragua, which suggests that larger amounts of water are stored deep in the subducting mantle lithosphere than previously thought. If most of the mantle low velocity zone can be interpreted as serpentinization, the amount of water stored in the Cocos plate offshore central Nicaragua may be about 2.5 times larger than offshore Nicoya Peninsula. Hydration of oceanic lithosphere at deep sea trenches may be the most important mechanism for the transfer of aqueous fluids to volcanic arcs and the deeper mantle.This work was funded by the U.S. National Science Foundation MARGINS program under grants OCE0405556, OCE 0405654, and OCE 0625178

Chronic widespread pain: A three year followup of pain distribution and risk factors

Objective. To describe the change of pain reports over time in 3 cohorts derived from the general population: (1) no chronic pain (NCP, n = 1156); (2) chronic regional pain (CRP n = 502) and (3) chronic widespread pain (CWP; n = 242). To identify risk factors that predict the development or persistence of chronic widespread pain. Methods. A 3-year followup from 1995 to 1998 with postal questionnaire to 2425 subjects of both sexes aged 20-74 years on the west coast of Sweden. Results. At followup, a larger proportion of subjects with initial CRP compared to initial NCP reported CWP (16.4 and 2.2%, respectively; p < 0.001). The majority of subjects (56.9%) who primarily reported CWP remained in that group at followup, but 26.8% had changed status to CRP and 16.3% to NCP. The number of painful regions (7-12 vs 0 regions) reported at baseline was the strongest predictor for the development of CWP with an odds ratio (OR) of 12,13 (95% CI 4.47-32.88). The development of CWP was also predicted by higher age (OR = 3.13, 95% CI 1.47-6.69, age-group 59-74 years vs age-group 20-34 years), and a family history of chronic pain (OR = 1.87, 95% CI 1.14-3.07). A habit of drinking alcohol weekly (OR = 0.42, 95% Cl 0.21-0.85) compared to the habit of never or seldom drinking alcohol was protective, as well as having personal social support (OR = 0.49, 95% CI 0.28-0.85). The persistence of CWP was predicted by the number of painful regions (13-18 vs 1-6 regions) at baseline (OR = 7.56, 95% CI 2.17-26.30), and being an immigrant (OR 3.22, 95% CI 1.33-7.77). Conclusion. Although the overall prevalence of CWP was stable over a 3-year period there was a considerable variation on an individual basis. This variability in expressing CWP was moderately predicted by a combination of risk factors. the most important being the number of painful regions at baseline. Future research will need to show how useful the identified factors are in clinical practice and whether intervention aimed at changing these factors will improve pain outcome

Health status as measured by SF-36 reflects changes and predicts outcome in chronic musculoskeletal pain: a 3-year follow up study in the general population

The SF-36 is a well-validated health status instrument measuring eight different health concepts. One aim of this study was to compare health status as measured by SF-36 in subjects from the general population with no chronic pain (NCP), chronic regional pain (CRP), and chronic widespread pain (CWP). A second aim was to assess if SF-36 could reflect changes in pain status over time. A third aim was to study if health status at baseline, measured by SF-36, could predict pain status 3 years later. The study was designed as a 3-year follow up with a postal questionnaire, including the SF-36 health survey, to 2357 subjects from the general population aged 20-74 years. The results were controlled for age, sex, co-morbidity, and socio-economic status. At baseline, all eight health concepts of SF-36 discriminated between subgroups with NCP, CRP and CWP. Changes in SF-36 over the 3-year follow up time coincided with improvement or deterioration of pain status. Baseline SF-36 scores predicted pain outcome 3 years later. These results support that both physical and mental aspects of health status as measured by SF-36 are affected by the burden of musculoskeletal pain, are sensitive to changes in pain status, and also predict the further development of pain. (C) 2003 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved

Causes of death between 1911-1950 in a Swedish province with a population characterized by longevity: Effects on life expectancy

Aims: Life expectancy in Sweden is among the highest in the world, and the province of Halland has the highest life expectancy in Sweden today. In an earlier paper the authors reported that life expectancy in the province of Halland in the south-west of the country was approx. 3.5 years above the national average between 1911 and 1950. The aim of this study was to explore the influence of different causes of death on life expectancy in Sweden and the distribution of these causes of death in Halland compared with Sweden as a whole during the same period of time. Method: Causes of death between 1911 and 1950 in the whole of Sweden and in Halland were obtained from the archives of Statistics Sweden. A trend analysis was performed on the impact of the various causes of death on life expectancy in Sweden. Calendar year, age, and sex were controlled for in a Poisson model. The distribution and incidence of the most frequent causes of death were compared between Halland and Sweden as a whole. Results: The decreasing mortality risk due to infectious diseases and the simultaneous increase in the risk of mortality from tumours and circulatory diseases contributed most to the change in life expectancy in Sweden. In Halland there was a lower mortality risk in the seven most important causes of death, which accounted for approx 80% of all deaths during the study period. Conclusions: The lower mortality risk from infectious diseases mostly favoured the improvement in life expectancy in Halland up to the mid-1930s. Thereafter, a low mortality risk from tumours and particularly circulatory diseases gained increasing importance although there was always a difference in favour of Halland from the beginning of the study period. Thus, the positive trend in life expectancy that favours Halland today seems to have existed for a long period of time

Allergic disease, immunoglobulins, exposure to mercury and dental amalgam in Swedish adolescents

High-dose exposure to inorganic mercury in man can influence the immune system and in rare cases cause immune-related disease. Some experimental animals also react with autoimmunity after low doses of inorganic mercury. Glomerulonephritis and an increased formation of immunoglobulin type E (IgE) are characteristic of these reactions. A recent study of 15-year-old adolescents demonstrated an association between immunoglobulin type A (IgA) and mercury concentration in plasma (P-Hg). There was also an association between allergic disease and IgA levels. The present study included 54 male and 23 female 19-year-old students who were recruited from a cohort that had been previously defined in a survey of allergic disease. Of the students, 39 (51%) had asthma, allergic rhinoconjunctivitis or eczema. Similar amalgam burden and P-Hg levels were observed in students with (n = 39) and without (n = 38) allergic disease (P = 0.48 and P = 0.98, respectively). As expected, IgE levels were significantly higher in the group with allergic disease (P = 0.006), but there was no association between P-Hg and IgE. The P-Hg levels were very low (median 1.50 nmol/l) and correlated significantly (r = 0.31) with the small number of amalgam surfaces (P = 0.007). Thirty-seven students had no amalgam fillings. P-Hg levels did not associate significantly with IgA, but did so with IgG2 (r = 0.33; P = 0.003). No conclusive correlation was observed between IgG2 and amalgam fillings. The findings of this study in 19-year-old subjects differ from earlier data obtained in a sample 4 years younger. The possibility of chance in the association between P-Hg levels and IgG2 must, however, be considered

Life expectancy in the province of Halland, Sweden, 1911-50: the progress of public health in a long-living population

Background: Life expectancy in Sweden is currently one of the longest in the world. The population of Halland has the longest life expectancy in Sweden. Aim: Life expectancy in the province of Halland and Sweden as a whole during 1911-50 was studied and the findings are discussed in the light of local historical data. Method: A trend analysis of risk ratio of death and life expectancy for Halland and Sweden was done for the period 1911-50 with regard to calendar year, age, and sex using a Poisson model. Results: The risk ratio between Halland and Sweden was 0.83 for 1911 and 0.76 for 1950. The risk ratio of death for women was lower compared with men and this difference increased over time. At the start of the study period life expectancy for men and women was higher in Halland (58.5 and 60.1 years, respectively) compared with Sweden (54.7 and 56.4 years, respectively) with a difference of approximately 3.8 years. At the end of the study period this difference in life expectancy for men and women in Halland (71.3 and 72.3 years, respectively) and the nation ( 68.0 and 69.2 years, respectively) had decreased to approximately 3.3 years. Conclusion: The long life expectancy seen in Halland today can be traced back to the early twentieth century. The starting point for this development seems to be a lower infant mortality in Halland compared with Sweden as a nation during the 1880-90. The basis for this might have been a greater increase of food production during the whole nineteenth century as well as other socioeconomic characteristics of Halland compared with the rest of the country