Orbit and origin of the LL7 chondrite Dishchii'bikoh (Arizona)     

Peter Jenniskens  Nick Moskovitz  Laurence A. J. Garvie  Qing‐Zhu Yin  J. Andreas Howell  Dwayne L. Free  Jim Albers  David Samuels  Marc D. Fries  Prajkta Mane  Daniel R. Dunlap  Karen Ziegler  Matthew E. Sanborn  Qin Zhou  Qiu‐Li Li  Xian‐Hua Li  Yu Liu  Guo‐Qiang Tang  Kees C. Welten  Marc W. Caffee  Henner Busemann  Matthias M. M. Meier  David Nesvorny 《Meteoritics & planetary science》2020,55(3):535-557

The trajectory and orbit of the LL7 ordinary chondrite Dishchii'bikoh are derived from low‐light video observations of a fireball first detected at 10:56:26 UTC on June 2, 2016. Results show a relatively steep ~21° inclined orbit and a short 1.13 AU semimajor axis. Following entry in Earth's atmosphere, the meteor luminosity oscillated corresponding to a meteoroid spin rate of 2.28 ± 0.02 rotations per second. A large fragment broke off at 44 km altitude. Further down, mass was lost to dust during flares at altitudes of 34, 29, and 25 km. Surviving meteorites were detected by Doppler weather radar and several small 0.9–29 g meteorites were recovered under the radar reflection footprint. Based on cosmogenic radionuclides and ground‐based radiometric observations, the Dishchii'bikoh meteoroid was 80 ± 20 cm in diameter assuming the density was 3.5 g/cm³. The meteoroid's collisional history confirms that the unusual petrologic class of LL7 does not require a different parent body than three previously observed LL chondrite falls. Dishchii'bikoh was ejected 11 Ma ago from parent body material that has a 4471 ± 6 Ma U‐Pb age, the same as that of Chelyabinsk (4452 ± 21 Ma). The distribution of the four known pre‐impact LL chondrite orbits is best matched by dynamical modeling if the source of LL chondrites is in the inner asteroid belt in a low inclined orbit, with the highly inclined Dishchii'bikoh being the result of interactions with Earth before impacting.  相似文献   

Mapping mountain areas: learning from Global,European and Norwegian perspectives     

Martin F.PRICE  Tor ARNESEN  Erik GL?ERSEN  Marc J.METZGER 《山地科学学报》2019,(1):1-15

Defining the spatial extent of mountain areas has long been a challenge. In the present century, the availability of digital elevation models(DEMs) incorporated into geographic information systems(GIS) has allowed the definition of mountain areas based on topographic and other criteria. This paper presents the various delineations of mountains that have been prepared at three scales – global, regional(Europe), and national – and explores the reasons and processes leading to these delineations, and how they have been used. A detailed case study is then presented for Norway. Overall, two types of approaches to mapping mountains have been taken: first, considering mountains per se, based on elevation and/or topography; second, considering them among other categories, e.g., landforms or biogeographical, environmental or landscape zones. All attempts to map mountain areas derive essentially from the objectives of those commissioning and/or undertaking the work; a unitary definition remains unlikely.  相似文献   

Annama H chondrite—Mineralogy,physical properties,cosmic ray exposure,and parent body history          下载免费PDF全文

Tomáš Kohout  Jakub Haloda  Patricie Halodová  Matthias M. M. Meier  Colin Maden  Henner Busemann  Matthias Laubenstein  Marc. W. Caffee  Kees C. Welten  Jens Hopp  Mario Trieloff  Ramakant R. Mahajan  Sekhar Naik  Josep M. Trigo‐Rodriguez  Carles E. Moyano‐Cambero  Michael I. Oshtrakh  Alevtina A. Maksimova  Andrey V. Chukin  Vladimir A. Semionkin  Maksim S. Karabanalov  Israel Felner  Evgeniya V. Petrova  Evgeniia V. Brusnitsyna  Victor I. Grokhovsky  Grigoriy A. Yakovlev  Maria Gritsevich  Esko Lyytinen  Jarmo Moilanen  Nikolai A. Kruglikov  Aleksey V. Ishchenko 《Meteoritics & planetary science》2017,52(8):1525-1541

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar‐Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short‐lived radionuclides are compatible with an atmospheric pre‐entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The ¹⁰Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre‐entry radius.  相似文献   

SPIRIT. SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies during the fourth International Polar Year (2007–2009)     

Jérôme Korona  Etienne Berthier  Marc Bernard  Frédérique Rémy  Eric Thouvenot 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(2):204-212

Monitoring the evolution of polar glaciers, ice caps and ice streams is of utmost importance because they constitute a good indicator of global climate change and contribute significantly to ongoing sea level rise. Accurate topographic surveys are particularly relevant as they reflect the geometric evolution of ice masses. Unfortunately, the precision and/or spatial coverage of current satellite missions (radar altimetry, ICESat) or field surveys are generally insufficient. Improving our knowledge of the topography of Polar Regions is the goal of the SPIRIT (SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies) international polar year (IPY) project. SPIRIT will allow (1) the acquisition of a large archive of SPOT 5 stereoscopic images covering most polar ice masses and, (2) the delivery of digital terrain models (DTM) to the scientific community.Here, we present the architecture of this project and the coverage achieved over northern and southern polar areas during the first year of IPY (July 2007 to April 2008). We also provide the first accuracy assessments of the SPIRIT DTMs. Over Jakobshavn Isbrae (West Greenland), SPIRIT elevations are within ±6 m of ICESat elevations for 90% of the data. Some comparisons with ICESat profiles over Devon ice cap (Canada), St Elias Mountains (Alaska) and west Svalbard confirm the good overall quality of the SPIRIT DTMs although large errors are observed in the flat accumulation area of Devon ice cap. We then demonstrate the potential of SPIRIT DTMs for mapping glacier elevation changes. The comparison of summer-2007 SPIRIT DTMs with October-2003 ICESat profiles shows that the thinning of Jakobshavn Isbrae (by 30–40 m in 4 years) is restricted to the fast glacier trunk. The thinning of the coastal part of the ice stream (by over 100 m) and the retreat of its calving front (by up to 10 km) are clearly depicted by comparing the SPIRIT DTM to an ASTER April-2003 DTM.  相似文献   

The importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs   总被引：14，自引：0，他引：14  

Daniel J.K. Ross  R. Marc Bustin 《Marine and Petroleum Geology》2009

The effect of shale composition and fabric upon pore structure and CH₄ sorption is investigated for potential shale gas reservoirs in the Western Canadian Sedimentary Basin (WCSB). Devonian–Mississippian (D–M) and Jurassic shales have complex, heterogeneous pore volume distributions as identified by low pressure CO₂ and N₂ sorption, and high pressure Hg porosimetry. Thermally mature D–M shales (1.6–2.5% VRo) have Dubinin–Radushkevich (D–R) CO₂ micropore volumes ranging between 0.3 and 1.2 cc/100 g and N₂ BET surface areas of 5–31 m²/g. Jurassic shales, which are invariably of lower thermal maturity ranging from 0.9 to 1.3% VRo, than D–M shales have smaller D–R CO₂ micropore volumes and N₂ BET surface areas, typically in the range of 0.23–0.63 cc/100 g (CO₂) and 1–9 m²/g (N₂).  相似文献   

Influence of food supply on the δ13C signature of mollusc shells: implications for palaeoenvironmental reconstitutions     

Franck Lartaud  Laurent Emmanuel  Marc de Rafelis  Stephane Pouvreau  Maurice Renard 《Geo-Marine Letters》2010,30(1):23-34

Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less commonly used as proxy for palaeoenvironmental reconstructions because shell δ¹³C is derived from both dissolved inorganic (seawater) and organic carbon sources (food), and interactions between these two pools make it difficult to unambiguously identify any independent effect of either. The main purpose of this study was to demonstrate any direct impact of variable food supply on bivalve shell δ¹³C signatures, using low/high rations of a ¹³C-light mixed algal diet fed to 14-month-old (adult) cultured Japanese Crassostrea gigas under otherwise essentially identical in vitro conditions during 3 summer months (May, June and July 2003, seawater temperature means at 16, 18 and 20 °C respectively) in experimental tanks at the Argenton laboratory along the Brittany Atlantic coast of France. At a daily ration of 12% (versus 4%) oyster dry weight, the newly grown part of the shells (hinge region) showed significantly lower δ¹³C values, by 3.5‰ (high ration: mean of −5.8  ± 1.1‰, n = 10; low ration: mean of −2.3  ± 0.7‰, n = 6; ANOVA Scheffe’s test, p < 0.0001). This can be explained by an enhanced metabolic activity at higher food supply, raising ¹³C-depleted respiratory CO₂ in the extrapallial cavity. Based on these δ¹³C values and data extracted from the literature, and assuming no carbon isotope fractionation between food and shell, the proportion of shell metabolic carbon would be 26  ± 7 and 5  ± 5% for the high- and low-ration C. gigas shells respectively; with carbon isotope fractionation (arguably more realistic), the corresponding values would be 69  ± 14 and 24  ± 9%. Both groups of cultured shells exhibited lower δ¹³C values than did wild oysters from Marennes-Ol éron Bay in the study region, which is not inconsistent with an independent influence of diet type. Although there was no significant difference between the two food regimes in terms of δ¹⁸O shell values (means of 0.1  ± 0.3 and 0.4  ± 0.2‰ at high and low rations respectively, non-significant Scheffe’s test), a positive δ¹³C vs. δ¹⁸O relationship recorded at high rations supports the interpretation of a progressive temperature-mediated rise in metabolic activity fuelled by higher food supply (in this case reflecting increased energy investment in reproduction), in terms not only of δ¹³C (metabolic signal) but also of δ¹⁸O (seawater temperature signal). Overall, whole-shell δ¹⁸O trends faithfully recorded summer/winter variations in seawater temperature experienced by the 17-month-old cultured oysters.  相似文献   

Geologic control of natural marine hydrocarbon seep emissions, Coal Oil Point seep field, California   总被引：2，自引：1，他引：1  

Ira Leifer  Marc J. Kamerling  Bruce P. Luyendyk  Douglas S. Wilson 《Geo-Marine Letters》2010,30(3-4):331-338

High-resolution sonar surveys, and a detailed subsurface model constructed from 3D seismic and well data allowed investigation of the relationship between the subsurface geology and gas-phase (methane) seepage for the Coal Oil Point (COP) seep field, one of the world’s largest and best-studied marine oil and gas seep fields, located over a producing hydrocarbon reservoir near Santa Barbara, California. In general, the relationship between terrestrial gas seepage, migration pathways, and hydrocarbon reservoirs has been difficult to assess, in part because the detection and mapping of gas seepage is problematic. For marine seepage, sonar surveys are an effective tool for mapping seep gas bubbles, and thus spatial distributions. Seepage in the COP seep field occurs in an east–west-trending zone about 3–4 km offshore, and in another zone about 1–2 km from shore. The farthest offshore seeps are mostly located near the crest of a major fold, and also along the trend of major faults. Significantly, because faults observed to cut the fold do not account for all the observed seepage, seepage must occur through fracture and joint systems that are difficult to detect, including intersecting faults and fault damage zones. Inshore seeps are concentrated within the hanging wall of a major reverse fault. The subsurface model lacks the resolution to identify specific structural sources in that area. Although to first order the spatial distribution of seeps generally is related to the major structures, other factors must also control their distribution. The region is known to be critically stressed, which would enhance hydraulic conductivity of favorably oriented faults, joints, and bedding planes. We propose that this process explains much of the remaining spatial distribution.  相似文献   

Numerical implementation and sensitivity analysis of a wave energy converter in a time-dependent mild-slope equation model     

Charlotte Beels  Peter Troch  Griet De Backer  Marc Vantorre  Julien De Rouck 《Coastal Engineering》2010

Several Wave Energy Converters (abbreviated as WECs) have intensively been studied and developed during the last decade and currently small farms of WECs are getting installed. WECs in a farm are partly absorbing, partly redistributing the incident wave power. Consequently, the power absorption of each individual WEC in a farm is affected by its neighbouring WECs. The knowledge of the wave climate around the WEC is needed to predict its performance in the farm. In this paper a technique is developed to implement a single and multiple WECs based on the overtopping principle in a time-dependent mild-slope equation model. So far, the mild-slope equations have been widely used to study wave transformations around coastal and offshore structures, such as breakwaters, piles of windmills and offshore platforms. First the limitations of the WEC implementation are discussed through a sensitivity analysis. Next the developed approach is applied to study the wave height reduction behind a single WEC and a farm. The wake behind an isolated WEC is investigated for uni- and multidirectional waves; it is observed that an increase of the directional spread leads to a faster wave redistribution behind the WEC. Further the wake in the lee of multiple WECs is calculated for two different farm lay-outs, i.e. an aligned grid and a staggered grid, by adapting the performance of each WEC to its incident wave power. The evolved technique is a fast tool to find the optimal lay-out of WECs in a farm and to study the possible influence on surrounding activities in the sea.  相似文献   

New sedimentological and palynological data from the Yarkand-Fergana Basin(Kyrgyz Tian Shan): Insights on its Mesozoic paleogeographic and tectonic evolution     

Julien Morin  Marc Jolivet  Dave Shaw  Sylvie Bourquin  Elena Bataleva 《地学前缘(英文版)》2021,12(1):183-202

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Isothermal compression of an eclogite from the Western Gneiss Region (Norway)     

Martin Simon  Pavel Pitra  Philippe Yamato  Marc Poujol 《Journal of Metamorphic Geology》2023,41(1):181-203

In the Western Gneiss Region in Norway, mafic eclogites form lenses within granitoid orthogneiss and contain the best record of the pressure and temperature evolution of this ultrahigh-pressure (UHP) terrane. Their exhumation from the UHP conditions has been extensively studied, but their prograde evolution has been rarely quantified although it represents a key constraint for the tectonic history of this area. This study focused on a well-preserved phengite-bearing eclogite sample from the Nordfjord region. The sample was investigated using phase-equilibrium modelling, trace-element analyses of garnet, trace- and major-element thermobarometry and quartz-in-garnet barometry by Raman spectroscopy. Inclusions in garnet core point to crystallization conditions in the amphibolite facies at 510–600°C and 11–16 kbar, whereas chemical zoning in garnet suggests growth during isothermal compression up to the peak pressure of 28 kbar at 600°C, followed by near-isobaric heating to 660–680°C. Near-isothermal decompression to 10–14 kbar is recorded in fine-grained clinopyroxene–amphibole–plagioclase symplectites. The absence of a temperature increase during compression seems incompatible with the classic view of crystallization along a geothermal gradient in a subduction zone and may question the tectonic significance of eclogite facies metamorphism. Two end-member tectonic scenarios are proposed to explain such an isothermal compression: Either (1) the mafic rocks were originally at depth within the lower crust and were consecutively buried along the isothermal portion of the subducting slab or (2) the mafic rocks recorded up to 14 kbar of tectonic overpressure at constant depth and temperature during the collisional stage of the orogeny.  相似文献