Evidence of a major environmental change recorded in a macrotidal bay (Marennes-Oléron Bay, France) by correlation between VHR seismic profiles and cores     

Isabelle Billeaud  Eric Chaumillon  Olivier Weber 《Geo-Marine Letters》2005,25(1):1-10

New, very high-resolution (25 cm) seismic profiles have revealed the internal architecture of the infilling of a macrotidal bay, the Marennes-Oléron Bay, France. Within this geometry, a major seismic unconformity has been correlated with core data. This correlation provides evidence that the seismic unconformity corresponds to a sharp grain-size decrease. Both seismic and core data indicate that this change of grain size can be interpreted as a record of a recent (around 1,000 years b.p.) decrease in hydrodynamical energy with time and/or a larger supply of fine-grained material. This recent environmental change can be related to natural infilling of the Marennes Oléron Bay, and to tidal prism decrease, increasing human activities (e.g. land reclamation, deforestation, agricultural land use) and climate fluctuations during the late Holocene, such as the transition between the cold period of the Dark Ages (1,550–1,050 years b.p.) and the Medieval warm period (1,050–550 years b.p.).  相似文献   

A few months-old storm-generated turbidite deposited in the Capbreton Canyon (Bay of Biscay, SW France)   总被引：1，自引：1，他引：1  

T. Mulder  O. Weber  P. Anschutz  F. Jorissen  J.-M. Jouanneau 《Geo-Marine Letters》2001,21(3):149-156

A gravity core taken in the canyon of Capbreton shows a succession of sedimentary facies which can be interpreted as three superimposed Bouma sequences. The turbiditic sequences are covered by an oxidised layer which contains live benthic foraminiferal faunas indicating a reprisal of hemipelagic deposition. Activities of ²³⁴Th and ²¹⁰Pb suggest that the most recent turbidite was deposited between early December 1999 and mid-January 2000. During this period, the most probable natural event able to trigger a turbidity current was the violent storm which affected the French Atlantic coast on 27 December 1999. The turbidity current could have been caused by a sediment failure due to an excess in pore pressure generated by the storm waves, an increase of the littoral drift, or the dissipation of the along-coast water bulge through the canyon. This sub-recent turbidite shows that the canyon experiences modern gravity processes, despite the lack of a direct connection with a major sediment source.  相似文献   

6′x 10′ Free air gravity anomalies of Europe including marine areas     

W. Torge  G. Weber  H. -G. Wenzel 《Marine Geophysical Researches》1984,7(1-2):93-111

A set of 103 997 free air gravity anomalies in 6′x 10′ blocks has been compiled covering Europe including the Mediterranean Sea, North Sea, Norwegian Sea, Baltic Sea and parts of the North Atlantic Ocean. Concerning sea areas, this data set is based on a collection of point free air gravity anomalies. Anomalies for land areas have been compiled resp. computed from free air gravity anomaly maps or Bouguer anomaly maps and partly from supplied mean values of convenient small block size. Remaining gaps have been interpolated by means of least squares prediction filtering. The precision of the compiled mean free air gravity anomalies is estimated to ±7 mgal, verified by a comparison of independent gravity anomaly sets.  相似文献   

I. Erdöl Ergebnisse der erdölgeologischen Erforschung Nordwestdeutschlands 1932–1947, ein Überblick     

Alfred Bentz  A. Meyer-Gürr  Helmut Fahrion  Walter Rühl  Wilhelm Kehrer  Hermann Deecke  H. Schlüter  Rolf Behrmann  Hans Weber  Herbert Lögters  Oswald Schmidt 《International Journal of Earth Sciences》1948,35(2):167-170

Ohne Zusammenfassung  相似文献   

Die Interpretation von seismischen Refraktionsmessungen im Grenzfallc 0=0     

Priv.-Doz. Dr. Max Weber 《Pure and Applied Geophysics》1961,49(1):119-128

Zusammenfassung Es wird im Anschluss an «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) die Interpretation von seismischen Refraktionsmessungen im Grenzfallc _o=0 eingehend behandelt.

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Summary In pursuance of «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) the special interpretation problem withc _o=0 is generally treated.

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New insights into the history and origin of the southern Maya block,SE México: U–Pb–SHRIMP zircon geochronology from metamorphic rocks of the Chiapas massif     

Bodo Weber  Alexander Iriondo  Wayne R. Premo  Lutz Hecht  Peter Schaaf 《International Journal of Earth Sciences》2007,96(2):253-269

The histories of the pre-Mesozoic landmasses in southern México and their connections with Laurentia, Gondwana, and among themselves are crucial for the understanding of the Late Paleozoic assembly of Pangea. The Permian igneous and metamorphic rocks from the Chiapas massif as part of the southern Maya block, México, were dated by U–Pb zircon geochronology employing the SHRIMP (sensitive high resolution ion microprobe) facility at Stanford University. The Chiapas massif is composed of deformed granitoids and orthogneisses with inliers of metasedimentary rocks. SHRIMP data from an anatectic orthogneiss demonstrate that the Chiapas massif was part of a Permian (∼ 272 Ma) active continental margin established on the Pacific margin of Gondwana after the Ouachita orogeny. Latest Permian (252–254 Ma) medium- to high-grade metamorphism and deformation affected the entire Chiapas massif, resulting in anatexis and intrusion of syntectonic granitoids. This unique orogenic event is interpreted as the result of compression due to flat subduction and accretionary tectonics. SHRIMP data of zircon cores from a metapelite from the NE Chiapas massif yielded a single Grenvillian source for sediments. The majority of the zircon cores from a para-amphibolite from the SE part of the massif yielded either 1.0–1.2 or 1.4–1.5 Ga sources, indicating provenance from South American Sunsás and Rondonian-San Ignacio provinces.  相似文献   

The origin of rutile-ilmenite aggregates (“nigrine”) in alluvial-fluvial placers of the Hagendorf pegmatite province, NE Bavaria, Germany     

H. G. Dill  F. Melcher  M. Füßl  B. Weber 《Mineralogy and Petrology》2007,89(3-4):133-158

Summary Titanium placer deposits occur in alluvial-fluvial drainage systems which dissect Moldanubian gneisses intruded by Late Variscan pegmatites (Hagendorf province) in southern Germany. Based upon their texture (zonation, exsolution lamellae, intergrowth), microchemical data (Nb, Cr, Ta, V, Fe, W, Sn) and mineral inclusions, two major grain types of intergrown rutile and ilmenite have been established. Grains of type A are always zoned and consist of rutile cores enveloped by ilmenite containing small inclusions of wolframite. A core-rim transition zone is characterized by complex relations of rutile and ilmenite, with rutile lamellae being rich in Nb, V and Fe. Types B1 and B2 aggregates consist of ilmenite with lamellae of niobian rutile and/or ilmenorutile, and additionally have inclusions of ferrocolumbite, pyrochlore, betafite, sphalerite, pyrrhotite and Fe oxides. Such grain types featuring an intimate intergrowth of rutile and ilmenite were called nigrine. Type-C grains are quite similar in their morphological appearance but consist of W-enriched rutile devoid of mineral inclusions and reaction products. Pseudorutile and leucoxene replacing minerals of the nigrine aggregates are presumably caused by supergene alteration under fluctuating redox conditions. Phosphate and aluminum remobilized by supergene processes led to the formation of hydrous Ti-rich phases containing Al, P and Fe. High Nb and W concentrations in nigrine aggregates and in rutile type C may be taken as a marker for highly differentiated granites or pegmatites. This has implications for both, heavy-mineral-based provenance analysis and stream sediment exploration.  相似文献   

Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints   总被引：2，自引：2，他引：2  

V. Masson-Delmotte  M. Kageyama  P. Braconnot  S. Charbit  G. Krinner  C. Ritz  E. Guilyardi  J. Jouzel  A. Abe-Ouchi  M. Crucifix  R. M. Gladstone  C. D. Hewitt  A. Kitoh  A. N. LeGrande  O. Marti  U. Merkel  T. Motoi  R. Ohgaito  B. Otto-Bliesner  W. R. Peltier  I. Ross  P. J. Valdes  G. Vettoretti  S. L. Weber  F. Wolk  Y. YU 《Climate Dynamics》2006,26(5):513-529

Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to the range of temperature change expected from a quadrupling of atmospheric CO₂ concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative insights on global climate changes. An erratum to this article can be found at  相似文献   

Individual accessibility and distance from major employment centers: An examination using space-time measures   总被引：1，自引：0，他引：1  

J. Weber 《Journal of Geographical Systems》2003,5(1):51-70

 Distance has often been assumed to be an influence on intraurban accessibility, whether in traditional proximity-based measures of accessibility, or through expectations about distance-minimizing travel behavior and the logic of the monocentric model. This paper examines the importance of distance from major employment centers to individual accessibility in Portland, Oregon, using space-time accessibility measures computed using GIS. The results of this research indicate that distance from these locations has mixed results on individual accessibility. This appears to reflect the importance of time, both the time of day activities are scheduled as well as time constraints, to individual activity patterns. Received: September 2002 / Accepted: January 2003 The author gratefully acknowledges the contributions of two anonymous reviewers, whose comments greatly improved the content of this paper  相似文献   

Crustal shear velocity structure across the Dead Sea Transform from two-dimensional modelling of DESERT project explosion seismic data   总被引：3，自引：0，他引：3  

J. Mechie  K. Abu-Ayyash  Z. Ben-Avraham  R. El-Kelani  A. Mohsen  G. Rümpker  J. Saul  M. Weber 《Geophysical Journal International》2005,160(3):910-924

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