Cosmogenic nuclides in the Košice meteorite: Experimental investigations and Monte Carlo simulations

Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides (⁷Be, ²²Na, ²⁶Al, ⁴⁶Sc, ⁴⁸V, ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co) in 19 fragments of the Ko?ice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic‐ray particles in the space affecting radionuclides with different half‐lives. Monte Carlo simulations of the production rates of ⁶⁰Co and ²⁶Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Ko?ice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Ko?ice meteorite is 5–7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Ko?ice is a regolith breccia. The agreement between the simulated and observed ²⁶Al activities indicate that the meteoroid was mostly irradiated by a long‐term average flux of galactic cosmic rays of 4.8 particles cm^?2 s^?1, whereas the short‐lived radionuclide activities are more consistent with a flux of 7.0 protons cm^?2 s^?1 as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall.     

术语“Karst”的起源和演化

对于术语＂karst＂的起源和演化,不少文献（包括手册、教科书、字典等）仍有不准确、不一致甚至错误的论述。鉴于此,本文不仅重述了众所周知的关于＂karst＂起源的事实,而且介绍了＂karst＂起源和演化的最新语言学研究结果。＂karst＂是由喀尔斯（Kras）高地的名称演化而来的。喀尔斯位于亚得里亚海的里雅斯特湾（Gulf of Trieste）达尔马提亚（Dal matia）海岸地区,其大部分属于斯洛文尼亚。喀尔斯是一处海拔150~450 m,覆盖面积550 km2（长约40 km,宽约13 km）的碳酸盐岩高地。斯洛文尼亚语、意大利语和德语分别称之为Kras、Carso和Karst。喀尔斯高地表面大致平坦,但从局部看,喀斯特洼地遍布,各种典型的喀斯特地貌形态随处可见,包括坡立谷、大小溶斗（包括大的塌陷溶斗）、喀斯特干谷和溶洞。这些形态规模较小,起伏平缓。喀尔斯高地的名称起源于前罗马时期,其古典拉丁语名称（也是目前已知最早的名称）为Carsus。该词的词根＊kar（u）s-是由意思为＂石头或岩石＂的词根＊kar-演化而来。从欧洲众多文献中可以发现有许多名词来自前印欧语系的词根kar（r）a/gar（r）a。这些词根最初意思指石头或岩石,而后发展为石头筑成的遮盖物——一间房屋,一座城堡,甚至一个村落,这些词根还演化成喀斯特相关术语。由Carsus的宾格形式Carsum演变成现代意大利语名称Carso;同样的宾格依据前斯洛文尼亚语言规则（即r或l出现在元音和辅音字母之间时,须将其移至元音字母之前。）演变成Kras;德语Karst则是由意大利语Carso依据德语变化规则（以s结束的单词末尾须添加t）演变而来。由此可见,Kras、Karst和Carso均源于古拉丁文Carsus,该词含有词根＊kar（u）s-。印刷技术的改进和新大陆的发现,带动了地图和地图集的出版。喀尔斯高地的名称不仅出现在地方性地图上,而且被大尺度区域性地图所标示出来,德文Karst甚至被用作区域地图的标题,足见喀尔斯高地的重要性。喀尔斯高地之所以比其它更大的地区重要且较早为人们所认识,与历史的地缘政治形势有关。16至19世纪,地中海东海岸大多由威尼斯共和国管辖,的里雅斯特港口和内陆地区则隶属于奥地利和土耳其帝国。对于奥地利帝国的公民,大部分中欧人和小部分东欧人来说,通向地中海唯一可行的途径就是从维也纳穿过卢布尔雅那市（Lju-bljana）,经喀尔斯高地,至的里雅斯特镇。1719年,当的里雅斯特港宣布成为自由港后,这条道路变得更为重要。与此同时,喀尔斯高地不寻常的地貌和恶劣的自然环境给途经的旅行者和学者留下了深刻的印象。在他们的旅行记录中对Kras有近乎相同的描述：＂碳酸盐岩裸露,岩洞繁多,没有水和土壤,夏暑冬寒,冬季强烈的冷风暴有时让高地无法通行......＂。此后,当描述其他喀斯特地区时,作者们往往会将其与Kras（Karst）相类比。1830年F.J.H.Hohenwart在《Postojna岩洞导游手册》中,第一次确切地写道＂喀斯特地貌不仅存在于Karst高地,它从Friuli平原一直延伸至希腊岛……＂。十九世纪上半叶,地质、地理和水文学者开始了对喀尔斯高地的详细研究,出版了喀斯特地质地貌方面的著作,并开始使用一些喀斯特术语。自1830年起,由于这些记述性的文字和专业著作大多用德语撰写,德语名称Karst逐渐为更多地区的人们所了解。19世纪末20世纪初,可以说＂karst＂已经成为国际科技术语。对＂karst＂加入国际术语行列影响最大的可能是毕业于维也纳大学的Jovan Cviji′c教授,他是最重要的学者之一,也是著名地形学教授A.Penck的学生。他最重要的喀斯特著作＂Das Karstphanomen＂（The phenomenon of Karst）的书名中就使用了＂karst＂。＂karst＂就这样由一个地名逐渐演变为学术名词,然后成为国际科技术语。     

Loggerhead sea turtles (Caretta caretta) as bioturbators in neritic habitats: an insight through the analysis of benthic molluscs in the diet

Molluscs are a diverse and ubiquitous group of organisms which contribute to the formation of biogenic sediments and are one of the major prey taxa for the neritic‐stage loggerhead sea turtles (Caretta caretta) worldwide. Here we investigated to what degree molluscs contribute to the diet of individual turtles, and what role the feeding strategy of loggerheads might play in bioturbation, one of the key processes in nutrient transport in marine ecosystems. We performed a detailed analysis of benthic molluscs from the digestive tracts of 62 loggerhead sea turtles (curved carapace length: 25.0–85.4 cm) found in the Northern Adriatic Sea. From 50 of the turtles that contained benthic molluscs, we identified 87 species representing 40 families and three classes (Gastropoda, Bivalvia and Scaphopoda), including 72 new dietary records for loggerhead turtle. Most of the identified molluscs were small‐sized species (shell length ≤ 3 cm) and were often found in a subfossil condition. Their intake may be considered a byproduct of infaunal mining, while larger molluscs were mainly found crushed into smaller fragments. Through such foraging behaviour loggerheads actively rework sediments, increase the surface area of shells and the rate of shells disintegration, acting as bioturbators in this system. We conservatively estimate that loggerheads in the neritic zone of the Adriatic Sea bioturbate about 33 tonnes of mollusc shells per year, and hypothesize about the possible effects of bioturbation reduction on environmental changes in the Northern Adriatic ecosystem.     

Multi-proxy reconstruction of the Holocene vegetation and land use dynamics in the Julian Alps,north-west Slovenia

Small mountain lakes are natural archives for understanding long-term natural and anthropogenic impact on the environment. This study focused on long-term (last ca. 13 000 years) vegetation changes and sedimentary processes in the catchment area of Lake Planina pri jezeru (1430 m a.s.l.) by using mineralogical, geochemical and palynological methods. Palynological results suggest that regional vegetation between 12 900 and 11 700 cal a bp was a herbaceous–forest tundra (Pinus, Artemisia, Poaceae ). Climate warming at the beginning of the Holocene (ca. 11 700 cal a bp ) caused the transition from a wetland (Cyperaceae) to an eutrophic lake with alternating anoxic (pyrite) and oxic conditions (gypsum). In addition, the surrounding area became forested (Picea, Larix, Ulmus). Fagus expanded at 10 200 cal a bp and Abies at 8200 cal a bp. Between 7500 and 4300 cal a bp , human impact on the environment was barely noticeable and mostly limited to grazing. During 4300–430 cal a bp human impact became more evident and gradually increased. The greatest influence was observed from 430 cal a bp onwards, when excessive exploitation of the surrounding area (logging and grazing) severely eutrophicated the lake.     

Mineral and chemical composition of the Jezersko meteorite—A new chondrite from Slovenia

The Jezersko meteorite is a newly confirmed stony meteorite found in 1992 in the Karavanke mountains, Slovenia. The meteorite is moderately weathered (W2), indicating short terrestrial residence time. Chondrules in partially recrystallized matrix are clearly discernible but often fragmented and have mean diameter of 0.73 mm. The meteorite consists of homogeneous olivine (Fa_19.4) and low‐Ca pyroxenes (Fs_16.7Wo_1.2), of which 34% are monoclinic, and minor plagioclase (Ab₈₃An₁₁Or₆) and Ca‐pyroxene (Fs₆Wo_45.8). Troilite, kamacite, zoned taenite, tetrataenite, chromite, and metallic copper comprise about 16.5 vol% of the meteorite. Phosphates are represented by merrillite and minor chlorapatite. Undulatory extinction in some olivine grains and other shock indicators suggests weak shock metamorphism between stages S2 and S3. The bulk chemical composition generally corresponds to the mean H chondrite composition. Low siderophile element contents indicate the oxidized character of the Jezersko parent body. The temperatures recorded by two‐pyroxene, olivine‐chromite, and olivine‐orthopyroxene geothermometers are 854 °C, 737–787 °C, and 750 °C, respectively. Mg concentration profiles across orthopyroxenes and clinopyroxenes indicate relatively fast cooling at temperatures above 700 °C. A low cooling rate of 10 °C Myr^?1 was obtained from metallographic data. Considering physical, chemical, and mineralogical properties, meteorite Jezersko was classified as an H4 S2(3) ordinary chondrite.     

Post‐stack diffraction imaging in vertical transverse isotropy media using non‐hyperbolic moveout approximations

Diffractions carry valuable information about local discontinuities and small‐scale objects in the subsurface. They are still not commonly used in the process of geological interpretation. Many diffraction imaging techniques have been developed and applied for isotropic media, whereas relatively few techniques have been developed for anisotropic media. Ignoring anisotropy can result in low‐resolution images with wrongly positioned or spurious diffractors. In this article, we suggest taking anisotropy into account in two‐dimensional post‐stack domain by considering P‐wave non‐hyperbolic diffraction traveltime approximations for vertical transverse isotropy media, previously developed for reflection seismology. The accuracy of the final images is directly connected to the accuracy of the diffraction traveltime approximations. We quantified the accuracy of six different approximations, including hyperbolic moveout approximation, by the application of a post‐stack diffraction imaging technique on two‐dimensional synthetic data examples.     

Hyperboloidal precession of a dynamically symmetric satellite. Construction of normal forms of the Hamiltonian

The Norma specialized program package, intended for normalization of autonomous Hamiltonian systems by means of computer algebra, is used in studies of small-amplitude periodic motions in the neighbourhood of regular precessions of a dynamically symmetric satellite on a circular orbit. The case of hyperboloidal precession is considered. Analytical expressions for normal forms and generating functions depending on frequencies of the system as on parameters are derived. Possible resonances are considered in particular. The 6th order of normalization is achieved. Though the intermediate analytical expressions occupy megabytes of computer's main memory, final ones are quite compact. Obtained analytical expressions are applied to the analysis of stability of small-amplitude periodic motions in the neighbourhood of hyperboloidal precession.     

Microtremor HVSR study for assessing site effects in the Bovec basin (NW Slovenia) related to 1998 Mw5.6 and 2004 Mw5.2 earthquakes

The Bovec basin, which is filled with glacial and fluvial sediments, has recently been struck by two strong earthquakes (1998 and 2004) which caused extensive damage (VII–VIII EMS-98). Strong site effects resulted in large variations in damage to buildings in the area, which could not be explained by the surface variations in Quaternary sediments. The microtremor horizontal-to-vertical-spectral ratio (HVRS) method was therefore applied to a 200 m dense grid of free-field measurements to assess the fundamental frequency of the sediments. Large variations in the sediment frequency (3–22 Hz) were obtained, with most of the observed values in the range 6–12 Hz. The observed frequencies cannot be related to the total thickness of Quaternary sediments (sand, gravel), but can be explained by the presence of conglomerate or lithified moraine at shallow depths. The results were compared also with the velocity structure derived from seismic refraction data. Microtremor measurements performed in several two and some three- and four-storey houses (masonry with RC floors), which prevail in the Bovec basin, have shown that the main building frequencies in the area are in the range 7–11 Hz. This indicates that damage to houses in both earthquakes in some parts of the basin was enhanced by site amplification and soil-structure resonance. Areas of possible soil-structure resonance were identified in the settlements Bovec–Brdo, Bovec–Mala vas, Čezsoča and Kal-Koritnica. Considerable changes in fundamental frequencies within short distances were established in the town of Bovec. Their values are as high as 22 Hz in the central part of the town, but diminish to 6–11 Hz in the adjacent Brdo and Mala vas districts. This is in agreement with the distribution of damage in both earthquakes, which was considerably higher in Brdo and Mala vas, although the houses in the central part of the town are older.

Microtremor investigations have proved an effective tool for assessment of site effects in cases of complex geological structure commonly encountered in young Alpine basins filled with glaciofluvial sediments which are partly cemented. Lithified layers can considerably change the fundamental frequency and, consequently, the site effects. By taking additional measurements in buildings possible soil-structure resonance can be identified.