Provenance and Magmatic-Metamorphic Evolution of a Variscan Island-Arc Complex: Constraints from U-Pb Dating, Petrology, and Geospeedometry of the Kyffhauser Crystalline Complex, Central Germany     

ZEH  ARMIN; GERDES  AXEL; WILL  THOMAS M.; MILLAR  IAN L. 《Journal of Petrology》2005,46(7):1393-1420

The Kyffhäuser Crystalline Complex, Central Germany, formspart of the Mid-German Crystalline Rise, which is assumed torepresent the Variscan collision zone between the East Avalonianterrane and the Armorican terrane assemblage. High-precisionU–Pb zircon and monazite dating indicates that sedimentaryrocks of the Kyffhäuser Crystalline Complex are youngerthan c. 470 Ma and were intruded by gabbros and diorites between345 ± 4 and 340 ± 1 Ma. These intrusions had magmatictemperatures between 850 and 900°C, and caused a contactmetamorphic overprint of the sediments at P–T conditionsof 690–750°C and 5–7 kbar, corresponding toan intrusion depth of 19–25 km. At 337 ± 1 Ma themagmatic–metamorphic suite was intruded by granites, syenitesand diorites at a shallow crustal level of some 7–11 km.This is inferred from a diorite, and conforms to P–T pathsobtained from the metasediments, indicating a nearly isothermaldecompression from 5–7 to 2–4 kbar at 690–750°C.Subsequently, the metamorphic–magmatic sequence underwentaccelerated cooling to below 400°C, as constrained by garnetgeospeedometry and a previously published K–Ar muscoviteage of 333 ± 7 Ma. With respect to P–T–D–tdata from surrounding units, rapid exhumation of the KCC canbe interpreted to result from NW-directed crustal shorteningduring the Viséan. KEY WORDS: contact metamorphism; U–Pb dating; hornblende; garnet; Mid-German Crystalline Rise; P–T pseudosection  相似文献   

Hydrological variations on the Central Tibetan Plateau since the Last Glacial Maximum and their teleconnection to inter‐regional and hemispheric climate variations          下载免费PDF全文

THOMAS KASPER  TORSTEN HABERZETTL  JUNBO WANG  GERHARD DAUT  STEFAN DOBERSCHÜtz  LIPING ZHU  ROLAND MÄUSBACHER 《第四纪科学杂志》2015,30(1):70-78

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Landscape sensitivity and ecological change in western Zambia: The long‐term perspective from dambo cut‐and‐fill sediments          下载免费PDF全文

S. L. BURROUGH  D. S. G. THOMAS  E. A. ORIJEMIE  K. J. WILLIS 《第四纪科学杂志》2015,30(1):44-58

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Establishment of modern circulation pattern at c. 6000 cal a BP in Disko Bugt,central West Greenland: opening of the Vaigat Strait     

KERSTIN PERNER  MATTHIAS MOROS  IAN SNOWBALL  JEREMY M. LLOYD  ANTOON KUIJPERS  THOMAS RICHTER 《第四纪科学杂志》2013,28(5):480-489

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Global ENSO-streamflow teleconnection,streamflow forecasting and interannual variability     

FRANCIS H. S. CHIEW  THOMAS A. McMAHON 《水文科学杂志》2013,58(3):505-522

Abstract

El Niño Southern Oscillation (ENSO) has been linked to climate anomalies throughout the world. This paper presents an overview of global ENSO-streamflow teleconnection and identifies regions where the relationship may be exploited to forecast streamflow several months ahead. The teleconnection is investigated by fitting a first harmonic to 24-month El Niño streamflow composites from 581 catchments worldwide and the potential for forecasting is investigated by calculating the lag correlation between streamflow and two indicators of ENSO. The analyses indicate clear ENSO-streamflow teleconnections in many catchments, some of which are consistent across large geographical regions. Strong and regionally consistent ENSO-streamflow teleconnections are identified in Australia and New Zealand, South and Central America, and weaker signals are identified in some parts of Africa and North America. The results suggest that the ENSO-streamflow relationship and the serial correlation in streamflow can be used to successfully forecast streamflow. The streamflow forecasts can be used to help manage water resources, particularly in systems with high interannual variability in Australia, southern and drier parts of Africa and some areas of North America.  相似文献   

Metamorphism of Calcic Pelitic Schists, Strafford Dome, Vermont: Compositional Zoning and Reaction History   总被引：3，自引：2，他引：3  

MENARD  THOMAS; SPEAR  FRANK S. 《Journal of Petrology》1993,34(5):977-1005

Four assemblages from calcic pelitic schists from South Strafford,Vermont, have been studied in detail to determine the relationshipbetween reaction history and compositional zoning of minerals.The lowest-grade assemblage is garnet + biotite + chlorite +plagioclase + epidote + quartz + muscovite + graphite + fluid.Along a path of isobaric heating, the net reaction is Chl +Ms + Ep + Gr = Grt + Bt + Pl + fluid. Garnet grows with decreasingFe/(Fe + Mg) and X_Spa, (from 0•2 to 0•05), X_Gra staysnearly constant between 0•20 and 0•25, and plagioclasegrows with X_An increasing from peristerite to 0•2–0•5. The subsequent evolution depends on whether chlorite or epidotereacts out first. If chlorite is removed from the assemblagefirst, the net reaction along an isobaric heating path becomesGrt + Ms + Ep + Qtz + Gr = Bt + Pl + fluid. X_An of plagioclaseincreases to 0•20–0•70, depending on the bulk-rockcomposition and changes in pressure and temperature. If epidoteis removed first, the assemblage becomes a simple pelite andthe net reaction becomes Chl + Pl + Ms + Qtz = Grt + Bt + H₂O.Plagioclase is consumed to provide Ca for growing garnet, andX_An, Fe/(Fe + Mg) of garnet, X_Gra, and X_Spa all decrease. Afterboth chlorite and epidote are removed, continued heating upto the metamorphic peak of {small tilde}600C produces littleprogress of the reaction Grt + Ms = Bt + Pl; and X_An increases. The four assemblages have been numerically modeled using theGibbs method starting with measured compositions. The modelssuccessfully predict the observed compositional zoning and trendsof mineral growth and consumption along the computed P–Tpaths. The models also predict the compositional mineral zoningthat would have resulted from other P–T paths. ^* Present address: Department of Geology, University of Alabama, Tuscaloosa, Alabama 35487  相似文献   

Carbon uptake experiments with a zonally-averaged global ocean circulation model   总被引：1，自引：0，他引：1  

THOMAS F. STOCKER  WALLACE S. BROECKER  DANIEL G. WRIGHT 《Tellus. Series B, Chemical and physical meteorology》1994,46(2):103-122

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Wind sedimentation in the Jafurah sand sea, Saudi Arabia   总被引：2，自引：0，他引：2  

STEVEN G. FRYBERGER  ABDULKADER M. AL-SARI  THOMAS J. CLISHAM†  SYED A. R. RIZVI  KHATTAB G. AL-HINAI 《Sedimentology》1984,31(3):413-431

The Jafurah sand sea of the Eastern Province of Saudi Arabia extends along the Arabian Gulf coastline from Kuwait in the north to the Rub Al Khali in the south, a distance of about 800 km. Sand drifts southward to south-eastward from regions of high wind energy in the north to low wind energy in the south. The aeolian landscape is zoned, with areas of deflation, transport and deposition from north to south. Drift rates in the zone of transport, near Abqaiq, range from 2 m³ m-w^-1 yr^-1 on sabkhas, to 29 m³ m-w^-1 yr^-1 on the crests of dunes. Average drift rates of approximately 18 m³ m-w^-1 yr^-1 observed during the study can cause about 1 m of accumulation per 5500 yr in a 100 km zone of deposition downwind, not including the bulk transport represented by the forward advance of dunes. Dune advance ranged from 23 m (2.9 m high dune) to 3 m (23 m high dune) during April-October 1980. The study area consists of dune, interdune, sand sheet and siliciclastic sabkha terrains, each of which is characterized by differing drift rates, and differing rates of erosion or deposition. Sedimentation occurs by lateral movement of dunes and interdunes, and vertical accretion by sand sheets and sabkhas.  相似文献   

Interpretation of grain-size distributions from measured sediment data, Platte River, Nebraska     

THOMAS R. ESCHNER  JAMES E. KIRCHER 《Sedimentology》1984,31(4):569-573

Breaks in the slope of log-probability plots of cumulative grain-size distributions of bed material are compared with frequency distributions of bedload and suspended sediment over a range of discharges at two stations on the Platte River in south-central Nebraska. The break between suspension and intermittent suspension as determined from the bed-material curve coincides with the upper limit of the grain-size overlap between bedload particles and suspended-sediment particles, whereas the break between intermittent suspension and traction corresponds to the grain size at the lower limit of overlap of bedload particles and suspended-sediment particles. Although grain-size distributions of bedload change little with discharge, the size of the coarsest grains in suspension increases with increasing discharge. Thus, the length of overlap of bedload and suspended-sediment distributions increases with increasing discharge. The limits of grain-size overlap of bedload and suspended-sediment distribution curves associated with near-flood discharges most closely approximate the breaks in the bed material grain-size distribution.  相似文献   

An early Holocene caribou antler from northern Ellesmere Island, Canadian Arctic Archipelago   总被引：1，自引：0，他引：1  

THOMAS G. STEWART  JOHN ENGLAND 《Boreas: An International Journal of Quaternary Research》1986,15(1):25-31

During the last glaciation of northern Ellesmere Island many areas remained ice-free. A caribou antler from deglacial-marine sediments in Clements Markham Inlet dates 8,415 ± 135 B.P. (S-2501). If locally derived it places caribou at the northern limit of their contemporary range at the onset of deglaciation in this area. Immediately to the south, on the Hazen Plateau, ice remained at its limit until c . 8,000 B.P. Therefore, this antler may indicate the presence of caribou during full glacial time.  相似文献