排序方式： 共有12条查询结果，搜索用时 15 毫秒
1.
2.
Mörner, N.‐A. and Lind, B., 2011. Reply: Comments on ‘Heimdall's stones at Vitemölla in SE Sweden and the chronology and stratigraphy of the surroundings’ by Mörner et al. (2009). Geografiska Annaler: Series A, Physical Geography, 93, 197–199. DOI: 10.1111/j.1468‐0459.2011.00429.x 相似文献
3.
ABSTRACT The purpose of an hydrometric network is to obtain data giving answers to problems raised by the use of water. The methodology suggested in this paper is essentially based on the regional identification of the actual and potential uses of water, on the estimate of the intensity of their use and on the determination of the hydrological characteristics related to this demand. The level of accuracy required for these characteristics is an important feature in the rationalization procedure. The various types of stations are defined according to the purpose of their use and the network considered is on a dynamic basis depending on the evolution of uses. The major results obtained for Quebec by the application of this method are described. 相似文献
4.
BY NILS-AXEL MÖRNER BOB G. LIND GÖRAN POSSNERT 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):205-213
Heimdall's Stones at Vitemölla is an archaeological monument of stones arranged in circles and where sightlines can be identified of the sunrise and sunset at winter and summer solstices and spring and autumn equinoxes. Therefore, this stone monument is likely to have served as an archaeoastronomic observatory. It is founded in a fossil land surface now covered by half a metre of eolian sand. In order to date this sand drift, sediment coring was performed in the nearby Sandefloen bog. Seven levels were subjected to AMS C14 dating. The first sand drift, correlated with the sand drift covering Heimdall's Stones, was dated at 500–600 cal. bc . Consequently, the observatory has to date back to the Bronze Age, fitting well with its Sun cult and with the rock carvings recorded on the individual stones. At the seashore 500 m east of the observatory and the bog, we were able to reconstruct the sea-level changes. In conclusion, we combine the recorded sea-level changes with the C14-dated bog stratigraphy and the observed stratigraphy at Heimdall's Stones (covering an area of 500×500 m) into one unified picture. The chronostratigraphic position of Heimdall's Stones agrees well with the dating of the Kivik grave. The Vitemölla area is likely to have been an important cultural centre in the Bronze Age. 相似文献
5.
6.
7.
Alexander N. KROT Kevin D. McKEEGAN Sara S. RUSSELL Anders MEIBOM Michael K. WEISBERG Jutta ZIPFEL Tatiana V. KROT Timothy J. FAGAN Klaus KEIL 《Meteoritics & planetary science》2001,36(9):1189-1216
Abstract— The metal‐rich chondrites Hammadah al Hamra (HH) 237 and Queen Alexandra Range (QUE) 94411, paired with QUE 94627, contain relatively rare (<1 vol%) calcium‐aluminum‐rich inclusions (CAIs) and Al‐diopside‐rich chondrules. Forty CAIs and CAI fragments and seven Al‐diopside‐rich chondrules were identified in HH 237 and QUE 94411/94627. The CAIs, ～50–400 μm in apparent diameter, include (a) 22 (56%) pyroxene‐spinel ± melilite (+forsterite rim), (b) 11 (28%) forsterite‐bearing, pyroxene‐spinel ± melilite ± anorthite (+forsterite rim) (c) 2 (5%) grossite‐rich (+spinel‐melilite‐pyroxene rim), (d) 2 (5%) hibonite‐melilite (+spinel‐pyroxene ± forsterite rim), (e) 1 (2%) hibonite‐bearing, spinel‐perovskite (+melilite‐pyroxene rim), (f) 1 (2%) spinel‐melilite‐pyroxene‐anorthite, and (g) 1 (2%) amoeboid olivine aggregate. Each type of CAI is known to exist in other chondrite groups, but the high abundance of pyroxene‐spinel ± melilite CAIs with igneous textures and surrounded by a forsterite rim are unique features of HH 237 and QUE 94411/94627. Additionally, oxygen isotopes consistently show relatively heavy compositions with Δ17O ranging from ?6%0 to ?10%0 (1σ = 1.3%0) for all analyzed CAI minerals (grossite, hibonite, melilite, pyroxene, spinel). This suggests that the CAIs formed in a reservoir isotopically distinct from the reservoir(s) where “normal”, 16O‐rich (Δ17O < ?20%0) CAIs in most other chondritic meteorites formed. The Al‐diopside‐rich chondrules, which have previously been observed in CH chondrites and the unique carbonaceous chondrite Adelaide, contain Al‐diopside grains enclosing oriented inclusions of forsterite, and interstitial anorthitic mesostasis and Al‐rich, Ca‐poor pyroxene, occasionally enclosing spinel and forsterite. These chondrules are mineralogically similar to the Al‐rich barred‐olivine chondrules in HH 237 and QUE 94411/94627, but have lower Cr concentrations than the latter, indicating that they may have formed during the same chondrule‐forming event, but at slightly different ambient nebular temperatures. Aluminum‐diopside grains from two Al‐diopside‐rich chondrules have O‐isotopic compositions (Δ17O ? ?7 ± 1.1 %0) similar to CAI minerals, suggesting that they formed from an isotopically similar reservoir. The oxygen‐isotopic composition of one Ca, Al‐poor cryptocrystalline chondrule in QUE 94411/94627 was analyzed and found to have Δ17O ? ?3 ± 1.4%0. The characteristics of the CAIs in HH 237 and QUE 94411/94627 are inconsistent with an impact origin of these metal‐rich meteorites. Instead they suggest that the components in CB chondrites are pristine products of large‐scale, high‐temperature processes in the solar nebula and should be considered bona fide chondrites. 相似文献
8.
Timothy J. FAGAN Kevin D. McKEEGAN Alexander N. KROT Klaus KEIl 《Meteoritics & planetary science》2001,36(2):223-230
Abstract— In situ io n microprobe analyses of spinel in refractory calcium‐aluminium‐rich inclusions (CAIs) from type 3 EH chondrites yield 16O‐rich compositions (δ 18O and δ 17O about‐40‰). Spinel and feldspar in a CAI from an EL3 chondrite have significantly heavier isotopic compositions (δ 18O and δ 17O about ?5‰). A regression through the data results in a line with slope 1.0 on a three‐isotope plot, similar to isotopic results from unaltered minerals in CAIs from carbonaceous chondrites. The existence of CAIs with 16O‐rich and 16O‐poor compositions in carbonaceous as well as enstatite chondrites indicates that CAIs formed in at least two temporally or spatially distinct oxygen reservoirs. General similarities in oxygen isotopic compositions of CAIs from enstatite, carbonaceous, and ordinary chondrites indicate a common nebular mechanism or locale for the production of most CAIs. 相似文献
9.
Abstract A canonical correlation method for determining the homogeneous regions used for estimating flood characteristics of ungauged basins is described. The method emphasizes graphical and quantitative analysis of relationships between the basin and flood variables before the data of the gauged basins are used for estimating the flood variables of the ungauged basin. The method can be used for both homogeneous regions, determined a priori by clustering algorithms in the space of the flood-related canonical variables, as well as for “regions of influence” or “neighbourhoods” centred on the point representing the estimated location of the ungauged basin in that space. 相似文献
10.
Abstract— Like calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous and ordinary chondrites, enstatite chondrite CAIs are composed of refractory minerals such as spinel, perovskite, Al, Ti‐diopside, melilite, hibonite, and anorthitic plagioclase, which may be partially to completely surrounded by halos of Na‐(±Cl)‐rich minerals. Porous, aggregate, and compact textures of the refractory cores in enstatite chondrite CAIs and rare Wark—Lovering rims are also similar to CAIs from other chondrite groups. However, the small size (<100μm), low abundance (<1% by mode in thin section), occurrence of only spinel or hibonite‐rich types, and presence of primary Ti‐(±V)‐oxides, and secondary geikelite and Ti, Fe‐sulfides distinguish the assemblage of enstatite chondrite CAIs from other groups. The primary mineral assemblage in enstatite chondrite CAIs is devoid of indicators (e.g., oldhamite, osbornite) of low O fugacities. Thus, high‐temperature processing of the CAIs did not occur under the reducing conditions characteristic of enstatite chondrites, implying that either (1) the CAIs are foreign to enstatite‐chondrite‐forming regions or (2) O fugacities fluctuated within the enstatite‐chondrite‐forming region. In contrast, secondary geikelite and Ti‐Fe‐sulfide, which replace perovskite, indicate that alteration of perovskite occurred under reducing conditions distinct from CAIs in the other chondrite groups. We have not ascertained whether the reduced alteration of enstatite chondrite CAIs occurred in a nebular or parent‐body setting. We conclude that each chondrite group is correlated with a unique assemblage of CAIs, indicating spatial or temporal variations in physical conditions during production or dispersal of CAIs. 相似文献