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排序方式: 共有50条查询结果,搜索用时 31 毫秒
41.
42.
Stephanie Koch Henning Schroeder Matthias Haeckel Christian Berndt Joerg Bialas Cord Papenberg Dirk Klaeschen Andreia Plaza-Faverola 《Geo-Marine Letters》2016,36(3):187-196
This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO2 reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone. 相似文献
43.
Muhammad MURTAZA Abdul Hadi Abd RAHMAN Joerg MUTTERLOSE Najiatun NAJLA Mazshurraiezal Bin NASIR 《《地质学报》英文版》2021,95(2):333-341
Discovery of the remains of belemnites referred to the Hibolithes sp. from the Jurassic–Cretaceous Pedawan Formation in Sarawak, on the island of Borneo(Malaysia) comprises four fragments of belemnite rostra. The specimens are characterized by multiple fractures and vein filling. Two fragments measuring about 130 mm are relatively intact, with only part of the alveolar region missing; a third piece represents the middle part of a rostrum, and the fourth specimen is too fragmentary to be assigned to any specific part of the rostrum. Based on specimen characteristics, a Tithonian–Hauterivian age is plausible. The sedimentary succession that yielded the belemnite material comprises thick shale that reflects the Te division of Bouma sequence. The occurrence of a Hibolithes taxon in the uppermost Jurassic to lowermost Cretaceous Pedawan Formation sediments in Borneo reflects a near to global palaeobiogeographic distribution of this genus. 相似文献
44.
Gordon R.M. Bromley Joerg M. Schaefer Gisela Winckler Brenda L. Hall Claire E. Todd Kurt M. Rademaker 《Quaternary Science Reviews》2009,28(23-24):2514-2526
Whether or not tropical climate fluctuated in synchrony with global events during the Late Pleistocene is a key problem in climate research. However, the timing of past climate changes in the tropics remains controversial, with a number of recent studies reporting that tropical ice age climate is out of phase with global events. Here, we present geomorphic evidence and an in-situ cosmogenic 3He surface-exposure chronology from Nevado Coropuna, southern Peru, showing that glaciers underwent at least two significant advances during the Late Pleistocene prior to Holocene warming. Comparison of our glacial-geomorphic map at Nevado Coropuna to mid-latitude reconstructions yields a striking similarity between Last Glacial Maximum (LGM) and Late-Glacial sequences in tropical and temperate regions.Exposure ages constraining the maximum and end of the older advance at Nevado Coropuna range between 24.5 and 25.3 ka, and between 16.7 and 21.1 ka, respectively, depending on the cosmogenic production rate scaling model used. Similarly, the mean age of the younger event ranges from 10 to 13 ka. This implies that (1) the LGM and the onset of deglaciation in southern Peru occurred no earlier than at higher latitudes and (2) that a significant Late-Glacial event occurred, most likely prior to the Holocene, coherent with the glacial record from mid and high latitudes. The time elapsed between the end of the LGM and the Late-Glacial event at Nevado Coropuna is independent of scaling model and matches the period between the LGM termination and Late-Glacial reversal in classic mid-latitude records, suggesting that these events in both tropical and temperate regions were in phase. 相似文献
45.
Brent M. Goehring Øystein Strand Lohne Jan Mangerud John Inge Svendsen Richard Gyllencreutz Joerg Schaefer Robert Finkel 《第四纪科学杂志》2012,27(1):89-96
We present a new regional calibration of the 10Be production rate from two well‐dated surfaces in southern Norway: a rock avalanche with 14C‐dated wood and a precisely dated Younger Dryas moraine. Calculated 10Be production rates are 4.26 ± 0.13 and 4.65 ± 0.14 at g?1 a?1 for the Lal/Stone and Lifton scaling models, respectively. Our regional production rate for southern Norway is 5% lower than the canonical global 10Be production rate with lower uncertainties. Our 10Be production rate agrees with regional 10Be production rates from north‐eastern North America and New Zealand. The 10Be production rate estimate presented here can be used to improve the precision and accuracy of exposure‐dated ice‐marginal features, as well as other surfaces, in northern Europe. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
46.
47.
Prof. C. B. Gregor Prof. Dr. Alan E. M. Nairn Dr. Joerg F. W. Negendank 《International Journal of Earth Sciences》1975,64(1):948-958
A sampling of Plio-Pleistocene and Upper Cretaceous basalts in SE Sicily yielded the following informationAssuming that the Cretaceous direction is reversed, the confidence oval for the virtual pole overlaps that for the Cretaceous pole of Africa determined from the Mlanje Syenite byMcElhinny et al. If SE Sicily was attached to Africa when these Upper Cretaceous lavas erupted, this result implies that extensive relative movement between the two is not likely to have occurred subsequently.
Zusammenfassung Die Aufsammlung und Untersuchung plio-pleistozäner und oberkretazischer Basalte in SE-Sizilien ergab die folgende paläomagnetische InformationUnter der Annahme einer inversen kretazischen Feld-Richtung überlappt der Konfidenzkreis des virtuellen Pols den kretazischen magnetischen Pol für Afrika, der vonMcElhinny et al. an den Gesteinen des Mlanje Syenites bestimmt wurde.Wenn SE-Sizilien zur Zeit der Extrusion dieser oberkretazischen Laven an Afrika angeheftet war, dann besagt dieses Ergebnis, da\ eine extensive relative Bewegung zwischen diesen beiden schwerlich nacheinander stattgefunden hat.
Résumé La compilation et l'analyse de basaltes d'âge plio-pleistocène et crétacique supérieur dans la SE-Sicile fournit l'information paléomagnétique suivanteDans l'acceptation d'un champ inversé au Crétacique, le cercle de confidence du pÔle virtuel recouvre le pÔle magnétique crétacique pour l'Afrique, tel queMcElhinny et al. l'ont déduit des roches de la Syénite de Mlanje. Si l'on rattache le SE de la Sicile à l'Afrique au moment de l'éruption de ces laves du Crétacique supérieur, ce résultat signifie qu'il est peu probable qu'un mouvement relatif extensif ait eu lieu entre les deux.
- - , , Elhinny . Mlanje Syenites. - «» , , - .相似文献
48.
Irene Schimmelpfennig Joerg M. Schaefer Brent M. Goehring Nathaniel Lifton Aaron E. Putnam David J. A. Barrell 《第四纪科学杂志》2012,27(7):671-674
In situ cosmogenic 14C (in situ 14C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ~25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C production rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate 10Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms 14C (g quartz)?1 a?1 and a 14C/10Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
49.
Salt and ice crystallisation in porous sandstones 总被引:1,自引:0,他引:1
Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect
of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing
scientific research done during the past century has shown that there are numerous parameters that have an influence on the
weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its
material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally,
laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done
to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation,
and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed
detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings
can help to understand the damaging mechanisms. 相似文献
50.
Gert Finger Frank Eisenhauer Reinhard Genzel Christopher Mandla Ian Baker Domingo Alvarez Antonio Amorim Wolfgang Brandner Christophe Dupuy Casey Deen Derek Ives Leander Mehrgan Manfred Meyer Karin Perraut Guy Perrin Jörg Stegmeier Christian Straubmeier Harald J. Weller Vincent Isgar 《Astronomische Nachrichten》2023,344(8-9):e20230069
Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e−APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is mk = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10−3 e−/s have been demonstrated with 1Kx1K e−APD arrays and 2Kx2K e−APD arrays have already been developed, the possibilities and adaptations of e−APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed. 相似文献