Uranium in rivers and estuaries of globally diverse, smaller watersheds

Data for uranium concentrations in 29 rivers and eight estuaries are presented. The river data expands the existing database on riverine uranium transport to include more smaller watersheds which collectively account for a large portion of material transport from the continent to the oceans. Riverine concentrations for these smaller watershed range from less than 50 to 660 pM. The results for these systems, when combined with previously published data on mostly larger rivers, do not change significantly the calculated global riverine flux and thus earlier estimates by Palmer and Edmond [Palmer, M.R., Edmond, J.M., 1993. Uranium in river water. Geochim. Cosmochim. Acta, 57, pp. 4947–4955] are substantiated. Uranium transport through eight diverse estuaries was studied to assess the importance of estuarine removal in the global marine uranium budget. Results indicate that uranium is conservatively transported in most systems studied. Results reported here for the Savannah estuary, however, indicate significant uranium removal. Our results suggest that uranium is removed in salt marsh estuaries at a rate of ca. 70 μmol/m². This compares to a rate of 15 μmol/m² for Delaware salt marshes [Church, T.M., Sarin, M.M., Fleisher, M.Q., Ferchlman, T.G., 1996. Salt marshes: an important sink for dissolved uranium. Geochim. Cosmochim. Acta, 60, pp. 3879–3887]. We suggest that uranium removal to salt marsh sediments is due to anaerobic microbially mediated processes. We use these results to estimate the global significance of the salt marsh sink in the oceanic budget of uranium. We estimate that 2.7×10⁷ mol of uranium are removed to salt marshes annually as compared to an annual global riverine input of 3–6×10⁷ mol estimated by Palmer and Edmond [Palmer, M.R., Edmond, J.M., 1993. Uranium in river water. Geochim. Cosmochim. Acta, 57, pp. 4947–4955].     

Chicxulub impactites: Geochemical clues to the precursor rocks

Abstract— The 65 Ma Chicxulub impact structure, Mexico, with a diameter of ～180 km is the focus of geoscientific research because of its link to the mass extinction event at the Cretaceous‐Tertiary (K/T) boundary. Chicxulub, now buried beneath thick post‐impact sediments, is probably one of the best‐preserved terrestrial impact structures known. Because of its inaccessibility, only limited samples on the impact lithologies from a few drill cores are available. We report major element and Sr‐, Nd‐, O‐, and C‐isotopic data for Chicxulub impact‐melt lithologies and basement clasts in impact breccias of drill cores C‐1 and Y‐6, and for melt particles in the Chicxulub ejecta horizon at the K/T boundary in Beloc, Haiti. The melt lithologies with SiO₂ ranging from 58 to ～63 wt% show significant variations in the content of Al, Ca, and the alkalies. In the melt matrix samples, δ¹³C of the calcite is about ?3%o. The δ¹⁸O values for the siliceous melt matrices of Y‐6 samples range from 9.9 to 12.4%o. Melt lithologies and the black Haitian glass have rather uniform ⁸⁷Sr/⁸⁶Sr ratios (0.7079 to 0.7094); only one lithic fragment displays ⁸⁷Sr/⁸⁶Sr of 0.7141. The Sr model ages T^SrUR for most lithologies range from 830 to 1833 Ma; unrealistic negative model ages point to an open Rb‐Sr system with loss of Rb in a hydrothermal process. The ¹⁴³Nd/¹⁴⁴Nd ratios for all samples, except one basement clast with ¹⁴³Nd/¹⁴⁴Nd of 0.5121, cluster at 0.5123 to 0.5124. In an ?_Nd‐?_Sr diagram, impactites plot in a field delimited by ?_Nd of ?2 to ?6, and ?_Sr of 55 to 69. This field is not defined by the basement lithologies described to occur as lithic clasts in impact breccias and Cretaceous sediments. At least one additional intermediate to mafic precursor component is required to explain the data.     

The Geography of Italian Pasta

Pasta is as much an institution as a food in Italy, where it has made a significant contribution to national culture. Its historical geography is one of strong regional variations based on climate, social factors, and diffusion patterns. These are considered herein; a taxonomy of pasta types is presented and illustrated in a series of maps that show regional variations. The classification scheme divides pasta into eight classes based on morphology and, where appropriate, filling. These include the spaghetti and tubular families, pasta shells, ribbon forms, short pasta, very small or “micropasta” types, the ravioli family of filled pasta, and the dumpling family, which includes gnocchi. Three patterns of diffusion of pasta types are identified: by sea, usually from the Mezzogiorno and Sicily, locally through adjacent regions, and outwards from the main centers of adoption. Many dry pasta forms are native to the south and center of Italy, while filled pasta of the ravioli family predominates north of the Apennines. Changes in the geography of pasta are reviewed and analyzed in terms of the modern duality of culture and commercialism.     

青藏高原东缘活动构造

青藏高原东缘由岷山断块和龙门山构造带构成。以活动构造地貌学为主线,在解析该地区主干断裂晚第四纪以来活动的地质地貌表现的基础上,对一批断裂运动学和史前强震活动的定量数据进行分析研究,结果表明:在岷山断块中,虎牙断裂的平均左旋滑动速率为1.4 mm/a,垂直滑动速率为0.3 mm/a。岷江断裂的平均垂直滑动速率介于0.37 mm/a~0.53 mm/a之间,左旋位错量与垂直位错量大致相当;在龙门山构造带中,茂汶-汶川断裂、北川-映秀断裂和彭县-灌县断裂的平均垂直滑动速率均在1 mm/a左右,且几条主干断裂的右旋位错量与垂直位错量相当。结合震源机制解结果和GPS测量资料,建立晚新生代以来青藏高原东缘向南东方向逸出的构造变形模式。     

Calculation Of The Height Of The Stable Boundary Layer In Practical Applications

Currently used and newly proposed calculation techniques for the heightof the stable boundary layer (SBL), including the bulk-Richardson-numbermethod, diagnostic equations for the equilibrium SBL height, and a relaxation-typeprognostic equation, are discussed from the point of view of their physical basis andrelevance to experimental data. Among diagnostic equations, the best fit to data exhibits an advanced Ekman-layer height model derived recently with due regard to the role of the free-flow stability. Its extension to non-steady regimes provides a prognostic equation recommended for use in practical applications.     

Campanian Climatic Change: Isotopic Evidence from Far East, North America, North Atlantic and Western Europe

Paleoclimatic settings have been reconstructed for the Campanian using original oxygen-isotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes (95, 98, 102, 390A, and 392A) in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific (to 24.2°C) and the eastern circum-Pacific (to 26.4°C) areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland (22.4–25.5°C), which agrees with the data on the Campanian Barykovskaya flora in high latitudes (Golovneva and Herman, 1998) and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska (19.4°C) and the Koryak Upland (22.4–25.5°C), we also expect Latest Campanian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main climatic tendency during the Campanian (with the exception of Latest Campanian) has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin (Krilyon) marine basin. In contrary to Huber’s et al. (2002) assumption, we expect warm greenhouse conditions during the most part of the Campanian.