A Petrologic Perspective of Kilauea Volcano's Summit Magma Reservoir

Two hundred years of magmatic history are documented by thelavas and tephra sampled from K     

O2-O2云反演算法及其在TROPOMI上的应用

利用遥感技术对大气环境污染进行监测时,云是影响痕量气体反演精度的重要因素,因此在痕量气体反演中需要对云的影响进行校正,通常使用的云参数主要是有效云量和云压。本文基于O₂-O₂ 477 nm吸收波段构建了O₂-O₂云反演算法：首先,根据有效云量和云高与连续反射率和O₂-O₂斜柱浓度之间的对应关系,结合假定的云模型利用VLIDORT辐射传输模型建立关于有效云量和云压的查找表;然后,通过差分吸收光谱技术拟合卫星载荷观测的大气层顶辐射,获得O₂-O₂斜柱浓度并计算连续反射率;最后,结合辅助数据,根据查找表进行插值反演获得有效云量和云压。通过将算法应用到OMI观测数据,将反演结果与OMCLDO2产品进行对比验证,有效云量和云压空间分布一致,相关系数R均超过0.97;并还将该算法应用于下一代大气成分监测仪器TROPOMI,与FRESCO+产品对比,有效云量和云压空间分布基本一致,当地表类型为海洋时,有效云量相关系数R大于0.97,云压相关系数R大于0.94,云压反演结果存在一定的区别;通过将O₂-O₂云反演算法和FRESCO+云压反演结果与CALIOP Cloud Layer产品进行对比,结果表明,在低云情况下,O₂-O₂云反演算法线性回归方程斜率为0.782,截距为198.0 hPa,相关系数R为0.850,算法表现优于FRESCO+。而在高云情况下,FRESCO+反演结果更接近CALIOP云压结果。在OMI和TROPOMI上的应用表明O₂-O₂云反演算法在大气云反演中具有较高的准确性和可行性,可以为大气痕量气体反演的校正提供云参数,并为中国同类型卫星载荷的云反演算法提供算法参考。     

Early Weichselian (MIS 5d and 5c) temperatures and environmental changes in northern Fennoscandia as recorded by chironomids and macroremains at Sokli,northeast Finland

Engels, S., Helmens, K. F., Väliranta, M., Brooks, S. J. & Birks, H. J. B. 2010: Early Weichselian (MIS 5d and 5c) temperatures and environmental changes in northern Fennoscandia as recorded by chironomids and macroremains at Sokli, northeast Finland. Boreas, Vol. 39, pp. 689–704. 10.1111/j.1502‐3885.2010.00163.x. ISSN 0300‐9483. A 25‐m‐long sediment record spanning the time from the Eemian to the Holocene was recovered from Sokli, northeast Finland. This study focuses on a 6‐m‐long sediment interval that is dated to the Early Weichselian period (MIS 5d and 5c) and consists of lacustrine and fluvial deposits. Using chironomid remains, botanical and zoological macroremains as well as sediment lithology, we were able to reconstruct past changes in the environment, including climate. The results indicate that the site was situated on a flood‐plain during the latter stages of MIS 5d (Herning Stadial) and that summer temperatures might have been ～6 °C lower than at present. Although this value should be treated with caution, as numerical analysis shows that it has a very poor fit‐to‐temperature, this low reconstructed value concurs with several other reconstructions that are available from western Europe. During MIS 5c (Brørup interstadial), the depositional environment changed into a lake system, initially with stratification of the water and subsequently with complete mixing and a strong influence of streams. Both chironomid‐based and macroremain‐based temperature inferences indicate past July air temperatures that were significantly higher than at present. This result is in contrast to other (low‐resolution) reconstructions from northern Fennoscandia that indicate past temperatures 6–7 °C lower than present using fossil coleopteran assemblages. However, several central European sites indicate that there was a phase during the Brørup interstadial that was characterized by high summer temperatures, and a comparison between the high‐resolution reconstructions from western Europe and the results presented in this study suggests that the north–south July air temperature gradient between the mid‐ and high‐latitudes was much weaker during the Brørup interstadial than it is at present. High solar insolation values (particularly the obliquity) during the Brørup interstadial might explain the low summer temperature gradient over the European continent. A return to fluvial conditions occurred in the upper parts of the sediment sequence, and, after a brief interval of gyttja deposition under cooling conditions, the site became glaciated during MIS 5b.     

Comparison of four meteorite penetration funnels in the Campo del Cielo crater field,Argentina

Abstract– More craters may be discovered in the future, but as it is currently known, the Campo del Cielo crater field is 18 km long by 4 km at its widest point. Such a distribution of craters suggests that the parent meteoroid entered and traversed the atmosphere at a very low angle relative to horizontal. The crater field contains at least 20 small craters produced by the larger fragments of the parent meteoroid. Four of these are explosion analog craters and the rest are penetration funnels. During four field seasons, we have constructed topographic and magnetic maps of four of the penetration funnels as found, and then dug trenches across them to learn their original structures and recover meteorites preserved within them. Structures of these penetration funnels indicate very low angles of impact, i.e., 9–16° relative to horizontal. This supports the idea that the parent meteoroid traversed the atmosphere at a low angle. Data given here for the four penetration funnels include projectile masses, lengths, widths, depths, and estimates of impact angles and azimuths. One of the penetration funnels described here (No. 6) can almost be classified as an explosion analog crater.     

Bedload transport and bed resistance associated with density and turbidity currents

Turbidity currents in the ocean are driven by suspended sediment. Yet results from surveys of the modern sea floor and turbidite outcrops indicate that they are capable of transporting as bedload and depositing particles as coarse as cobble sizes. While bedload cannot drive turbidity currents, it can strongly influence the nature of the deposits they emplace. This paper reports on the first set of experiments which focus on bedload transport of granular material by density underflows. These underflows include saline density flows, hybrid saline/turbidity currents and a pure turbidity current. The use of dissolved salt is a surrogate for suspended mud which is so fine that it does not settle out readily. Thus, all the currents can be considered to be model turbidity currents. The data cover four bed conditions: plane bed, dunes, upstream‐migrating antidunes and downstream‐migrating antidunes. The bedload transport relation obtained from the data is very similar to those obtained for open‐channel flows and, in fact, is fitted well by an existing relation determined for open‐channel flows. In the case of dunes and downstream‐migrating antidunes, for which flow separation on the lee sides was observed, form drag falls in a range that is similar to that due to dunes in sand‐bed rivers. This form drag can be removed from the total bed shear stress using an existing relation developed for rivers. Once this form drag is subtracted, the bedload data for these cases collapse to follow the same relation as for plane beds and upstream‐migrating antidunes, for which no flow separation was observed. A relation for flow resistance developed for open‐channel flows agrees well with the data when adapted to density underflows. Comparison of the data with a regime diagram for field‐scale sand‐bed rivers at bankfull flow and field‐scale measurements of turbidity currents at Monterey Submarine Canyon, together with Shields number and densimetric Froude number similarity analyses, provide strong evidence that the experimental relations apply at field scale as well.     

Late Pleistocene stratigraphy at Boliden, northern Sweden

Till-covered sand and silt sediments with organic material from Boliden, northern Sweden, have been resampled and reinvestigated. Texture and petrographic analyses demonstrated one till bed overlying, and one underlying the sandy sediments. Low frequencies of diatoms were noted, representing freshwater, halophilous and brackish water taxa. The diatoms may be allochthonous or autochthonous, or redeposited from older deposits. Pollen analysis revealed a new picture of the composition of the vegetation, as compared with earlier investigations. The flora consisted of an arctic-subarctic treeless shrub and herb vegetation dominated by Salix, Betula nana , Gramineae and Cyperaceae. Artemisia and several arctic-alpine herbs were important elements. The identification of Salix wood as well as fruits and fruit scales of Betula nana and Betula cf. humilis is in agreement with the pollen-analytical results, as is the occurrence of Nordicboreal species of Coleoptera. Two radiocarbon datings resulted in an age of c. 45,000 B. P. and >40,000 B.P. The Boliden till-covered sediments were most probably deposited during an Early or Middle Weichselian interstadial, but the initial or final stage of an interglacial (Eemian) is also possible.     

An investigation of soil erosion and redistribution in a Mediterranean lowland agricultural catchment using caesium-137

This study sought to contribute to an improved understanding of soil erosion and redistribution on Mediterranean agricultural land, where traditional soil conservation practices have been applied over millennia to provide effective protection of cultivated land. The study was undertaken in the Na Borges catchment, a groundwater-dominated lowland limestone basin (319 km2), located in the northeastern part of Mallorca, Spain. The average sediment yield from the basin, based on river sediment load data, is 1 t/km2·yr. The 137Cs technique was used to quantify soil redistribution rates over the past 40 years and to identify the key factors involved in soil erosion and redistribution processes. To estimate erosion and deposition rates and to elucidate the main factors affecting soil redistribution, samples were collected from six slope transects representative of the local land use and slope gradients and the presence or absence of soil conservation practices. A mass balance and a profile distribution conversion model were used for cultivated areas and areas of natural vegetation, respectively, to derive point estimates of the soil redistribution rates from the 137Cs inventories measured for individual soil bulk cores. In areas without soil conservation practices, the estimated mean soil erosion rates ranged from 12.7 to 26.4 t/ha·yr, which correspond to the slight and moderate erosion classes. The erosivity of Mediterranean climatic conditions combined with the influence of agricultural practices and slope gradient on soil erosion, represent the main factors responsible for the variation of soil losses documented for the cultivated land located in downslope areas, in the absence of soil conservation practices. Deposition dominated for those transects affected by soil conservation practices, with rates ranging between 18.8 and 96.6 t/ha·yr. However, this situation does not mean that soil conservation measures retain all the sediment, but rather that agriculture and urbanization (i.e. new rural paths and stone boundaries) modified the micro-topography and diverted sediment from other upslope zones towards the slopes where sampling transects were located.     

The Petrology and Geochemistry of Mafic Igneous Rocks in the Anorthosite-Bearing Adirondack Highlands, New York

Igneous rocks of broadly basaltic composition are widely distributedin the anorthosite-bearing Adirondack Highlands of New York.They constitute a mafic series of rocks that occurs on the marginsof the anorthosite series and up to 50 km away from the anorthosite.On an Sr reference diagram, the mafic series has an apparentinitial ⁸⁷Sr/⁸⁶Sr value of 0.7036, which is consistent with1100 Ma subcontinental mantle. The series was probably emplacedin the interval 1150–1100 Ma, during which time anorthositeand granitic magmas were also emplaced. The rocks were metamorphosedshortly thereafter ({small tilde} 1088 Ma) under upper-amphiboliteand granulite facies conditions. Individual bodies of maficrocks range in thickness from small enclaves and layers >>1 m thick to large lensoid masses several tens of meters thick.Despite deformation and metamorphic recrystallization, manyof the rocks retain chiHed margins, cross-cutting relationships,and relict igneous textures. Selected samples of the mafic series have been analyzed fortheir major and trace element compositions. Metamorphism didnot significantly alter the igneous geochemical relationships,and the rocks retain mantle-like values for Zr/Nb, K/Zr, K/Rb,Rb/Sr, and ⁸⁷Sr/⁸⁶Sr. The most primitive rocks of the seriesare silica-undersaturated gabbroic troctolites, and the moreevolved rocks are basaltic in composition. The mafic seriesas a whole has high abundances of A1₂O₃, FeO, the light rareearth elements (LREE), and other incompatible trace elements.Even the most geochemically primitive compositions have highFeO contents. The Fe enrichment and Si depletion that are shownby chemically evolved compositions are consistent with a Fennertrend of fractionation. Low levels of normative di indicatethat high Fe is not a result of the extensive fractionationof cpx. The geochemical trends that are defined by the traceelements, including the REE, suggest the basaltic rocks maybe differentiates of a parental magma of gabbroic troctolitecomposition. The main compositional trend of the mafic seriescan be simulated by 61% crystallization of olivine and plagioclaseof a gabbroic troctolite, followed by 13% crystallization ofolivine, plagioclase, clinopyroxene, and titanomagnetite atthe final stages. The modelled ratio of olivine to plagioclasecrystallization changes from 1–8: 1 to 0–64: 1.These non-cotectic ratios may reflect a delay in the crystallizationof plagioclase relative to olivine, possibly as a result oflow nucleation rates. At later stages of differentiation, plagioclasewas more important in the crystallization of the series. Delayedcrystallization of plagioclase may also have resulted in thehigh A1₂O₃ contents and enhancement of Eu and Sr relative toother trace elements at early stages of differentiation. The mafic series and the silica-saturated anorthosite seriestogether form an anorthosite-norite-troctolite (ANT) suite.More than one mantle composition may have been involved in generatingthe Adirondack mafic magmas. The rocks retain geochemical evidenceof a source that was depleted in basaltic components (cpx) butenriched in Fe, Ti, K, and the LREE. Previously documented evidenceof anticlockwise cooling paths (Bohlen, 1987) and of a regionalgravity high centered beneath the Adirondack region (Simmons,1964) suggests that of the continental crust by basaltic magmasmay have underplating of the continental crust by basaltic magmasmay have been an important feature of the tectonic evolutionofthe region. A model of mantle upwelling beneath thinning continentalcrust explains the geochemically hybrid nature of the maficseries magmas. It is also consistent with a tectonic settingof incipient or failed continental rifting, to which the generationof the anorthosites is commonly attributed.     

Flora, vegetation and climate at Sokli, northeastern Fennoscandia, during the Weichselian Middle Pleniglacial

A 2 m thick laminated lacustrine deposit of silt and clay recovered from the high-latitudinal site at Sokli (northern Finland) provides a unique mid-Weichselian fossil record for Fennoscandia. High-resolution botanical and zoological analyses of the lacustrine deposit allow detailed reconstruction of the regional vegetational development and of the history of the lake and the wetland ecosystem within the Sokli basin during the early part of the Weichselian Middle Pleniglacial (=equivalent to Marine Isotope Stage (MIS) 3). The inferred terrestrial vegetation represented by the Sokli MIS 3 sequence (so-called Tulppio Interstadial) was probably low-arctic tundra, treeless but with shrub elements including juniper, willow, dwarf birch, ericoids, lycopods and a rich herb flora with a variety of arctic–alpine taxa and heliophilous, pioneer elements. The presence of herbs such as Rubus chamaemorus, Epilobium palustre, Potentilla palustris and Sphagnum, Drepanocladus and other mosses suggests that the lake was fringed by wet meadows and peatlands or peaty telmatic communities. The distributional ranges of pine and tree birch were probably only a few hundred kilometres south or southeast of Sokli. This is concordant with evidence for the presence of boreal tree taxa during the MIS 3 in the Baltic countries and further east in Europe, but contradicts with the commonly inferred treeless tundra or grass-dominated steppe conditions in central Europe.