探地雷达技术对表层岩溶带典型剖面组构刻画与界面识别   总被引：1，自引：0，他引：1  

高强山  彭韬  付磊  王世杰  曹乐  程倩云 《中国岩溶》2019,38(5):759-765

表层岩溶带是岩溶研究的重要对象,以往研究以剖面调查半定量为主,文章利用探地雷达属性技术对其发育情况进行定量研究。选取3个表层岩溶带的典型剖面（浅裂隙土、深裂隙土、厚土层覆盖）,并采集探地雷达数据,通过提取相干体属性和均方根振幅属性来挖掘雷达数据中的潜在信息,用于区分介质组构和识别发育深度界面。结果表明,均方根振幅属性较好地区分出了浅裂隙土型和深裂隙土型的岩土介质,厚土层覆盖型的犁耕层与非犁耕层土壤介质;相干体属性能较好地识别出表层岩溶带和下部完整基岩,定量化其发育厚度。   相似文献   

First results obtained with DENIS     

E. Copet  B. De Batz  N. Epchtein  P. Fouqué  F. Lacombe  T. Le Bertre  D. Rouan  D. Tiphène  J. Borsenberger  S. Kimeswenger 《Astrophysics and Space Science》1994,217(1-2):25-26

We briefly report on the first astronomical results obtained with the DENIS camera at the ESO 1 meter telescope.  相似文献   

Vereinfachte Berechnung der Radioaktivität und der zugehörigen Streuung (inkl. Vertrauensintervall und Vertrauensgrenzen) mit Hilfe eines speziellen Rechenschiebers und passender Rechentabellen     

M. M. Bezzegh-Galántai  H. L. Le Roy 《Aquatic Sciences - Research Across Boundaries》1965,27(2):368-376

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Dynamics of an Abra alba population (bivalve-scrobiculariidae) in the Bay of Brest     

C. Hily  H. Le Bris 《Estuarine, Coastal and Shelf Science》1984,19(4):463-475

The Abra population studied, lived in a muddy-sand Melinna palmata community in the vicinity of the harbour of Brest. There were two periods of spawning in the year: June to August and end of autumn. Individuals 12 mm long can spawn after the first winter. Recruitment was regularly observed in 1 mm mesh sieves in May and September–October. Growth rings were formed in winter; a second growth ring in summer was correlated with spawning. The modal analysis showed a decreasing growth rate and maximum length for the successive cohorts over the three years surveyed. Growth characteristics observed in this population seem to be due to disturbances brought about by neighbouring dredgings which had just ended at the beginning of the study.  相似文献   

Remarks on the homogeneity of a sample used to determine the Hubble parameterH 0     

Gérard Le Denmat 《Astrophysics and Space Science》1976,45(1):159-161

In a recent series of papers, Sandage and Tammann reach the conclusion according to which the Hubble constant is everywhere the same. This result arises from the analysis of two samples (a nearby one and a remote one) of Sc-type galaxies, each sample separately giving the same <H ₀> mean value. We attempt to check whether or not the whole data from both the samples together are consistent with theH ₀=constant hypothesis at a suitable level of statistical significance.  相似文献   

Resistance of a coastal ecosystem to increasing eutrophic conditions: the Bay of Brest (France), a semi-enclosed zone of Western Europe     

Olivier Le Pape  Yolanda Del Amo  Alain Menesguen  Alain Aminot  Bernard Quequiner  Paul Treguer 《Continental Shelf Research》1996,16(15):1885-1907

The Bay of Brest is a semi-enclosed coastal ecosystem receiving high nutrients loading from freshwater inputs. In order to analyse the response of phytoplankton stocks to increasing eutrophic conditions, a survey of the annual cycle of hydrographic properties, nutrients and chlorophyll a concentrations, and carbon uptake rates was performed at four stations in 1993. This database has been compared to earlier measurements performed during several comparable surveys within the last 20 years. As compared to the seventies, a doubled nitrate loading is now entering this ecosystem, which is related to increased agricultural activities on the drainage basins, while the geographical origin of the nitrate input has been modified. As a result of these anthropogenic modifications, summer averaged Si/N stoichiometric balance has decreased during the two last decades but, contrary to what has been observed in other coastal ecosystems, phytoplankton stocks have not increased. Several ecological factors have hindered eutrophication: the high hydrodynamic mixing with adjacent marine waters, caused by the macrotidal regime, induces important nutrients losses, temperature and mostly light limit primary production while Si and P high recycling maintain nitrogen limitation in this ecosystem. Conjunction of these non-anthropogenic factors explains the global stability of phytoplankton stocks.  相似文献   

The Cretaceous–Tertiary transition in Guatemala: limestone breccia deposits from the South Petén basin     

W. Stinnesbeck  G. Keller  J. de la Cruz  C. de León  N. MacLeod  J. E. Whittaker 《International Journal of Earth Sciences》1997,86(3):686-709

Limestone breccia deposits in southern Mexico, Guatemala and Belize have recently been interpreted as proximal to distal ballistic fallout deposits, generated by a bolide impact that struck Yucatan at K/T boundary time. We review the age, lithology and the depositional environment of five K/T boundary sections in the South Petén area of Guatemala (Caribe, Aserradero, Chisec, Actela, Chemal) in order to evaluate the nature and origin of K/T limestone breccia deposition. The sections are located 500?km south of the proposed impact site at Chicxulub and trend in an east–west direction from the Guatemala/Mexico border to southern Belize. In four of the five sections examined, a breccia unit up to 50?m thick overlies reef-bearing shallow-water limestones of late Cretaceous (Campanian-Maastrichtian) age. Rhythmically bedded limestones, marls and siltstones of early Danian age overlie the breccia and were deposited under middle-to outer-neritic conditions. The breccia consists of differently coloured layers of shallow-water limestones. Clast size generally decreases upsection to thin layers of predominantly rounded clasts, and these fine-grained rudstones grade into grainstones at the top. In at least one section (EI Caribe) diagenetically altered glass spherules are present in the uppermost layers of the grainstone. These glass spherules are of stratigraphic position and chemical composition similar to black and yellow glass from Beloc, Haiti and Mimbral, Mexico, which some workers have chemically linked to melt glass within the breccia of the Chicxulub cores. We suggest that breccia deposition in Guatemala may have been multi-event, over an extended time period, and related to the collision of the Yucatan and Chortis plates as well as related to a major impact or volcanic event at the end of the Cretaceous.  相似文献   

关于L—Fuzzy子群     

刘龙章  乐励华 《华东地质学院学报》1997,20(3):293-300

本文利用模型子群概念，引入了Ｌ－Ｆｕｚｚｙ子群概念。基于模糊集合的层次结构特征，得到Ｌ－Ｆｕｚｚｙ了群若干重要性质；给出并证明Ｌ－Ｆｕｚｚｙ子群的一系列等价刻划；文章最后讨论Ｌ－Ｆｕｚｚｙ子群同态性质 。  相似文献   

赣东北地区重要火成岩的40Ar／39Ar年龄   总被引：11，自引：0，他引：11  

赵崇贺 《地球科学》1997,22(3):257-260

在赣东北蛇绿混杂岩带发现含晚古生代放射虫硅夺，测定了该带内的和带外几个关键地点的火山岩和辉长岩的＾４０Ａｒ／＾３０Ａｒ同位素地南年龄，获得了以下结果：火山岩的坪年龄为４３４．９－４８６．７Ｍａ，辉长岩的坪年龄为２３２．５－２６６．３Ｍａ，因此可以肯定赣东北地区有早生代晚期的火山活动，证实了上述火成冉不是中、新元古代的产物，它们中的一部分与晚古生代硅质岩都是蛇绿岩套的成员，属该区晚古生代洋壳的组成部  相似文献   

The effects of source rocks and chemical weathering on the petrogenesis of siliciclastic sand from the Neto River (Calabria, Italy): implications for provenance studies     

Emilia Le Pera  Josè Arribas  Salvatore Critelli  & Amparo Tortosa 《Sedimentology》2001,48(2):357-378

Plutonic and gneissic rocks of the Sila Massif in the uppermost portion of the Neto drainage basin (Calabria, Southern Italy) weather and erode under a humid Mediterranean climate. During the development of weathering profiles, a combination of chemical weathering and granular disintegration processes occurred. Chemical weathering involves a loss of both plagioclase (mainly during grus generation) and K-feldspar (mainly during soil formation). This loss is attributed to transformation of plagioclase to clay minerals and to leaching and dissolution of K-feldspar. Sand composition is quartzofeldspathic and nearly homogeneous along the main channel of the Neto River, even where the river cuts across a blanket of sedimentary cover. Thus, fluvial transport does not alter sand composition within the Neto drainage basin. Petrographic indices are effective in (1) discriminating between contributions from similar (granite and gneiss) source rocks (Qm/F); (2) relating the provenance of plutoniclastic and gneissiclastic sand found in the headwaters to grus horizons (Qm/F; Q/Rg); and (3) distinguishing between upstream first-cycle and downstream multicycle sand (Q/Rg). This last distinction is further emphasized by considering both aphanitic and phaneritic varieties of rock fragments (RgRmRs diagram). Chemical weathering is the main sand producer within the regolithic environment in northern Calabria. In addition, rapid erosion resulting from steep slopes removes weathered products, and rapid and short transport leads to minimal sediment maturation. In general, the F/Q index is climate and relief dependent; thus, it should be used in conjunction with palaeoclimatic and palaeophysiographic evidence for provenance interpretations of ancient quartzofeldspathic sandstones.  相似文献