Peralkaline felsic magmatism at the Nemrut volcano,Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV     

Ray?MacdonaldEmail author  Mari?Sumita  Hans-Ulrich?Schmincke  Bogus?aw?Bagiński  John?C.?White  S?awomir?S.?Ilnicki 《Contributions to Mineralogy and Petrology》2015,169(4):34

Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO₂ close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas.  相似文献   

Glacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial     

Susan Ivy-Ochs  Hanns Kerschner  Peter W. Kubik  Christian Schlüchter 《第四纪科学杂志》2006,21(2):115-130

The Gschnitz stadial was a period of regionally extensive glacier advance in the European Alps that lies temporally between the breakdown of the Last Glacial Maximum piedmont lobes and the beginning of the Bølling warm interval. Moraines of the Gschnitz stadial are found in medium to small catchments, are steep‐walled and blocky, and reflect a snowline lowering of 650–700 m in comparison to the Little Ice Age reference snowline. ¹⁰Be surface exposure dating of boulders from the moraine at the type locality at Trins (Gschnitz valley, Tyrol, Austria) shows that it stabilised no later than 15 400 ± 1400 yr ago. The overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500 ± 300 yr, indicating that the Gschnitz cold period began approximately 15 900 ± 1400 yr ago, if not somewhat earlier. This is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15 400 ¹⁴C yr BP (18 020–19 100 cal. yr) and 13 250 ¹⁴C yr BP (15 360–16 015 cal. yr). A palaeoclimatic interpretation of the Gschnitz glacier based on a simple glacier flow model and statistical glacier‐climate models shows that precipitation was about one‐third of modern‐day precipitation and summer temperatures were about 10 K lower than today. In comparison, during the Younger Dryas, precipitation in this area was only about 10% less and T_s (summer temperature) was only 3.5–4 K lower than modern values. Based on the age of the moraine and the cold and dry climate at that time, we suggest that the Gschnitz stadial was the response of Alpine glaciers to cooling of the North Atlantic Ocean associated with Heinrich Event 1. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Holocene evolution of the Triftje- and the Oberseegletscher (Swiss Alps) constrained with <Superscript>10</Superscript>Be exposure and radiocarbon dating     

Olivia Kronig  Susan Ivy-Ochs  Irka Hajdas  Marcus Christl  Christian Wirsig  Christian Schlüchter 《Swiss Journal of Geoscience》2018,111(1-2):117-131

To develop a more precise understanding of Alpine glacier fluctuations during the Holocene, the glacier forefields of the Triftjegletscher and the Oberseegletscher east of Zermatt in the Valais Alps, Switzerland, were investigated. A multidisciplinary approach of detailed geological and geomorphological field mapping combined with ¹⁰Be exposure and radiocarbon dating was applied. A total of twelve samples of boulders and bedrock were taken from both Little Ice Age (LIA) landforms, as documented by the Dufour map published in 1862, and from landforms outside of the LIA. The resulting ¹⁰Be ages range between 12590 ± 350 a and 420 ± 170 a. A piece of wood found embedded in the Little Ice Age moraine gave radiocarbon ages that range between 293 cal years BP up to modern (356–63 cal years before 2013). Based on these results, four tentative steps of the Holocene evolution could be distinguished. An early Holocene stage, which documents the decay of the Egesen stadial glaciers when the first parts of the study area became ice free. This was followed by a phase with no evidence of glacier advance. Then in the late Holocene, the glaciers advanced (at least) twice. An advance around 1200 a, as shown by several moraine ages, coincides with the Göschenen II cold phase. A more extensive readvance occurred during the LIA as shown on the historical maps and underpinned by one ¹⁰Be exposure age and the radiocarbon age. This later advance destroyed or overprinted the earlier landforms in most parts of the area.  相似文献   

Lateglacial and early Holocene surface exposure ages of glacial boulders in the Taiwanese high mountain range     

Robert Hebenstreit  Susan Ivy-Ochs  Peter W. Kubik  Christian Schlüchter  Margot Böse 《Quaternary Science Reviews》2011,30(3-4):298-311

Glacial landforms and sediments mapped in three presently unglaciated mountain massifs, the Nanhuta Shan, the Hsueh Shan and the Yushan, support the concept of repeated, multi-stage glaciations in the Taiwanese high mountain range during the late Pleistocene. New results from surface exposure dating using in situ produced cosmogenic ¹⁰Be measured in samples taken from erratic and moraine boulders in Nanhuta Shan at altitudes between 3100 and 3500 m are presented here. The results confirm independent and previously reported Optically Stimulated Luminescence (OSL) ages and ¹⁰Be exposure ages from glacial deposits in the same area and suggest a Lateglacial and early Holocene glaciation, the so called Nanhuta glacier advance with two substages at about 12–15 ka and 9.5 ka BP. The respective equilibrium line altitudes (ELA) were calculated at 3340 m and 3440 m with corresponding ELA depressions of 610 ± 100 m and 510 ± 100 m relative to the present day (theoretical) ELA, which is estimated to be at about 3950 ± 100 m in Taiwan. Large-scale erosional landforms indicate a much wider glacier extent during an earlier stage, which is not dated in Nanhuta Shan so far. Luminescence dating from near Hsueh Shan suggests an age of marine isotope stage (MIS) 4 for this stage.  相似文献   

Sorption of inorganic mercury and monomethyl mercury in an iron–humus podzol soil of southern Norway studied by batch experiments     

K. Schlüter 《Environmental Geology》1997,30(3-4):266-279

Considerable fractions of the Hg content of lake and river systems in Scandinavia are discharged from the soil of the catchments. An important soil type in Scandinavia is the iron–humus podzol. The sorption characteristics of this soil type for inorganic Hg(II) and monomethyl mercury were investigated by batch experiments. The solubility of Hg²⁺ and CH₃Hg⁺ in the soil horizons containing organic matter increases with increasing pH of the soil solution by favoring the formation of solute organic matter–mercury complexes. While the solubility of Hg²⁺ is strongly dependent on complexation to dissolved organic matter, the solubility of CH₃Hg⁺ is more dependent on ion exchange. The concentration of solute inorganic Hg(II) increased with increasing temperature probably because of an increase in the concentration of dissolved organic carbon. There was no effect of temperature on the concentration of solute CH₃Hg⁺. At pH values where inorganic mercury–hydroxo complexes are formed, inorganic Hg(II) is efficiently sorbed to the metal oxides of the mineral soil. The soil–water distributions of inorganic Hg(II) in the different soil horizons were described by Freundlich isotherms or linear isotherms for common and contaminated mercury contents in the soils.  相似文献   

Land subsidence in Mashhad Valley, northeast Iran: results from InSAR, levelling and GPS     

Mahdi Motagh  Yahya Djamour  Thomas R. Walter  Hans-Ulrich Wetzel  Jochen Zschau  Siavash Arabi 《Geophysical Journal International》2007,168(2):518-526

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青藏高原若干地点的第四纪冰川年代学^* ——深切怀念孙殿卿院士   总被引：1，自引：1，他引：1  

赵志中  钱方  刘宗秀  田国强  李名则  苗琦  谭征兵  J.M.Schaefer  P.Oberholzer  S.Strasky  Ch.Schlüechter  吴锡浩 《第四纪研究》2007,27(5):669-673

青藏高原第四纪冰川时空演化问题广受关注。应用宇宙成因核素暴露年龄测定方法开展高原古冰川的年代学研究,对青藏高原聂拉木、唐古拉山、义敦海子山和折多山等4个地区的第四纪冰碛物进行了\{¹⁰ Be\},²⁶ Al和²¹ Ne暴露年龄测定,获得了青藏高原不同地点第四纪冰川发育的年代学数据,结果表明青藏高原出现了多期第四纪冰期,分别为YD事件、末次冰期晚阶段、末次冰期早阶段、倒数第2次冰期和倒数第3次冰期。  相似文献   

Air-Sea Interaction over the Indian Ocean During the Two Contrasting Monsoon Years 1987 and 1988 Studied with Satellite Data     

M. R. Ramesh Kumar  P. Schlüssel 《Theoretical and Applied Climatology》1998,60(1-4):219-231

Summary The air-sea interaction processes over the tropical Indian Ocean region are studied using sea surface temperature data from the Advanced Very High Resolution Radiometer sensor onboard the NOAA series of satellites. The columnar water-vapour content, low-level atmospheric humidity, precipitation, wind speed, and back radiation from the Special Sensor Microwave Imager on board the U.S. Defense Meteorological Satellite Program are all examined for two contrasting monsoon years, namely 1987 (deficit rainfall) and 1988 (excess rainfall). From these parameters the longwave radiative net flux at the sea surface and the ocean-air moisture flux are derived for further analysis of the air-sea interaction in the Arabian Sea, the Bay of Bengal, the south China Sea and the southern Indian Ocean. An analysis of ten-day and monthly mean evaporation rates over the Arabian Sea and Bay of Bengal shows that the evaporation was higher in these areas during the low rainfall year (1987) indicating little or no influence of this parameter on the ensuing monsoon activity over the Indian subcontinent. On the other hand, the evaporation in the southern Indian Ocean was higher during July and September 1988 when compared with the same months of 1987. The evaporation rate over the south Indian Ocean and the low-level cross-equatorial moisture flux seem to play a major role on the ensuing monsoon activity over India while the evaporation over the Arabian Sea is less important. Since we have only analysed one deficit/ excess monsoon cycle the results presented here are of preliminary nature. Received November 5, 1997 Revised March 20, 1998  相似文献   

From seamount to oceanic island, Porto Santo, central East-Atlantic     

Ralf Schmidt  Hans-Ulrich Schmincke 《International Journal of Earth Sciences》2002,91(4):594-614

The uplifted and deeply eroded volcanic succession of Porto Santo (central East-Atlantic) is the product of a wide spectrum of dynamic processes that are active in shoaling to emergent seamounts. Two superimposed lapilli cones marking the base of the exposed section are interpreted as having formed from numerous submarine to subaerial phreatomagmatic explosions, pyroclastic fragmentation being subordinate. The lower basaltic and the upper mugearitic to trachytic sections are dominated by redeposited tephra and are called 'lapilli cone aprons'. Vertical growth due to accumulation of tephra, voluminous intrusions, and minor pillowed lava flows produced ephemeral islands which were subsequently leveled by wave erosion, as shown by conglomerate beds. Periods of volcanic quiescence are represented by abundant biocalcarenite lenses at several stratigraphic levels. The loose tephra piles became stabilized by widespread syn-volcanic intrusions such as dikes and trachytic to rhyolitic domes welding the volcanic and volcaniclastic ensemble into a solid edifice. Shattering of a submarine extrusive trachytic dome by pyroclastic and phreatomagmatic explosions, accentuated by quench fragmentation, resulted in pumice- and crystal-rich deposits emplaced in a prominent submarine erosional channel. The dome must have produced an island as indicated by a collapse breccia comprising surf-rounded boulders of dome material. Subaerial explosive activity is represented by scoria cones and tuff cones. Basaltic lava flows built a resistant cap that protected the island from wave erosion. Some lava flows entered the sea and formed two distinct types of lava delta: 1. closely-packed pillow lava and massive tabular lava flows along the southwestern coast of Porto Santo, and 2. a steeply inclined pillow-hyaloclastite breccia prism composed of foreset-bedded hydroclastic breccia, variably-shaped pillows, and thin sheet flows capped by subhorizontal submarine to subaerial lava flows along the eastern coast of Porto Santo.The facies architectures indicate emplacement: 1. on a gently sloping platform in southwestern Porto Santo, and 2. on steep offshore slopes along high energy shorelines in eastern Porto Santo.Growth of the pillow-hyaloclastite breccia prism is dominated by the formation of foreset beds but various types of syn-volcanic intrusions contributed significantly. Submarine flank eruptions occurred in very shallow water on the flanks of the hyaloclastite prism in eastern Porto Santo. The island became consolidated by intrusion of numerous dikes and by emplacement of prominent intrusions that penetrate the entire volcanic succession. Volcanic sedimentation ended with the emplacement of a debris avalanche that postdates the last subaerial volcanic activity.  相似文献   

Reflection Seismic Investigations In the Volcaniclastic Apron of Gran Canaria and Implications For Its Volcanic Evolution     

Thomas Funck  Thomas Dickmann  Roland Rihm  Sebastian Krastel  Holger Lykke-Andersen  Hans-Ulrich Schmincke 《Geophysical Journal International》1996,125(2):519-536

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