This study contributes the first palcomagnetic data from dated Cretaceous units of the Coast Belt (51.3øN, 123.8øW) in which palcohorizontal bedding surfaces can be identified with certainty. We sampled 38 sites through a 1.5-km stratigraphic interval of Cenomanian Silverquick sedimentary strata and Cenomanian to Campanian Powell Creek volcanics in the Tatlow syncline in the Tyaughton-Methow Basin. Magnetizations at 21 sites have high unblocking temperatures (TUB) and pass the tilt test (precision k = 5 before untilting, maximum k = 48 after 100% untilting). Magnetic minerals of volcanics show original textures, mean declinations in volcanic and sedimentary rocks are statisticall•lelltlCal, and---'•: ........ ' •-• : ^,: •,.• • •o •.4 o pmanty is consistent + , 1101111•1,1. 111• mean lil•11natlon ..• _ •, probability P -0.05) of this pretilting magnetization is 20.1 ø _+ 4.0 ø shallower than that expected if the rocks were deposited in their present position relative to cratonic North America. Field and laboratory observations rule out other causes for these anomalous shallow inclinations. These rocks therefore have been displaced northward by 3000 +_ 500 km relative to cratonic North America since mid-Cretaceous time. This displacement is almost 3 times greater than that estimated from mid-Cretaceous volcanics in the nowadjacent Intermontane Belt. Evidently the two belts were not amalgamated until latest Cretaceous or Early Tertiary time. These results are inconsistent with all previous geologically based tectonic reconstructions of the Cordillera. Magnetizations at eight sites in Silverquick and Powell Creek beds have low Tus and directional characteristics similar to those in three younger diorite intrusions. Reversed and normal polarities occur, the rocks are commonly highly altered, and maximum precision occurs after 40% untilting. The magnetizations therefore are interpreted as overprints of latest Cretaceous age acquired during folding. magnetization direction to be corrected to the palcohorizontal plane, and (2) by obtaining observations from Cretaceous stratified rocks in which accurate bedding attitudes can be determined. The first test has already been carried out for the 96-93 Ma Mount Stuart batholith (Figure 1); Ague and Brandon [1992], on the basis of hornblende geobarometry, have corrected the palcomagnetic observations [Beck et al., 1981] for tilt and obtained an estimate of motion from the south of 2900 + 700 km. We describe the first palcomagnetic results from Cretaceous bedded rocks of the Coast Belt, which allow us to carry out the second test. The sedimentary and volcanic sequence studied is particularly suitable for six reasons. They contain thinly bedded, planar-laminated siltstones and fine-grained sandstones of fluvial overbank origin from which paleohorizontal surfaces can be determined with precision. The nøAr/39Ar data provide the age of the Powell Creek volcanics. The strata occur in a syncline, the Tatlow syncline (Figure 2), with an interlimb 6073 6074 WYNNE ET AL.' MOUNT TATLOW PA...
Objective To determine temporal trends in incidence and risk factors of nutritional rickets in a community-based population. Patients and Methods Rochester Epidemiology Project (REP) data were used to identify all children (<18 years) residing in Olmsted County, Minnesota between January 1, 1970 and December 31, 2009 with diagnostic codes corresponding to rickets, vitamin D deficiency, hypovitaminosis D, rachitis, osteomalacia, genu varum, genu valgum, craniotabes, hypocalcemia, hypocalcemic seizure, and tetany. Record abstraction was performed to select subjects with radiographic confirmation of rickets. Age- and gender-matched controls were identified for evaluation of risk factors. The main outcome measure was radiographic rickets without identifiable inherited, genetic, or non-nutritional causes. Incidence rates were calculated using REP census data. Results Of 768 children with eligible diagnostic codes, 23 had radiographic evidence of rickets; of these, 17 children had nutritional rickets. All were younger than 3 years and 13 (76%) were nonwhite. Clinical presentation included poor growth (n=12), leg deformity (n=8), motor delay (n=5), leg pain (n=3), weakness (n=3), and hypocalcemia or tetany (n=2). The incidence of nutritional rickets in children under 3 years was 0, 2.2, 3.7, and 24.1 per 100,000 for the decades beginning in 1970, 1980, 1990, and 2000, respectively (P=.003 for incidence trend). Nutritional rickets was associated with black race, breastfeeding, low birth weight, and stunted growth (P<.05 for all). Four of 13 (31%) who underwent 25-hydroxyvitamin D testing had values less than 10 ng/mL (25 nmol/L). Conclusion Nutritional rickets remains rare, but the incidence has dramatically increased after 2000. Not all cases can be attributed to vitamin D deficiency.
Objective To determine the incidence trend of 25-hydroxyvitamin D [25(OH)D] values >50 ng/mL and associated toxicity. Patients and Methods We conducted a retrospective, population-based study in Olmsted County, MN, from January 1, 2002 through December 31, 2011 (10 years) using the Rochester Epidemiology Project. Individuals were eligible if they resided in Olmsted County, MN, during the study period and had a measured 25(OH)D value >50 ng/mL (>125 nmol/L). The date of the first 25(OH)D value >50 ng/mL was considered the index date for incidence determination. Hypercalcemia, the primary vitamin D toxicity, was considered potentially associated with the 25(OH)D concentration if measured within 3 months of the 25(OH)D measurement, and such cases had medical record review. Results Of 20,308 total 25(OH)D measurements, 1714 (8.4%), 123 (0.6%), and 37 (0.2%) unique persons had 25(OH)D values >50, ≥80, and ≥100 ng/mL, respectively. The age- and sex-adjusted incidence of 25(OH)D values >50 ng/mL increased from 9 to 233 per 100,000 person-years from 2002 to 2011 (P<.001), respectively, and was greatest in persons of age ≥65 years (P<.001) and in females (P<.001). Serum 25(OH)D values were not significantly related with serum calcium values or with the risk of hypercalcemia. Medical record review identified four cases (0.2%) where 25(OH)D values >50 ng/mL were associated temporally with hypercalcemia, but only one had clinical toxicity associated with the highest observed 25(OH)D value of 364 ng/mL. Conclusion The incidence of 25(OH)D values >50 ng/mL increased significantly between 2002 and 2011, without a corresponding increase in acute clinical toxicity.
Foreland deformation, in the form of arches or uplifts, occurred throughout the eastern Rocky Mountains region during the Laramide orogeny . Arches with the same structural style developed in the mid-continent region, east of the Rocky Mountains, although these were subsequently buried by Tertiary sedimentary rocks. We attribute deformation in the Rocky Mountain foreland and continental interior to folding of the entire lithosphere (lithospheric buckling) as a result of horizontal endload on the western edge of North America. The observed wavelength of arches in the western United States is ca. 190 km, a spacing consistent with a lithospheric buckling interpretation. This buckling model provides a mechanical explanation for the distinction between "thin-skinned Sevier-style and "thick-skinned" Laramide-style deformation, which depends respectively upon the decoupling or coupling of lithospheric layers. Additionally, the buckling model explains concurrent tectonism east of the Rocky Mountains during Late Cretaceous time. Dextral shearing within the block uplifts indicates that the deformation was broadly transpressional during the Laramide orogeny.
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