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531.
Mu Ramkumar Doris Stüben Zsolt Berner Jens Schneider 《Journal of Earth System Science》2010,119(1):1-17
The Ariyalur-Pondicherry sub-basin of the Cauvery basin comprises a near complete stratigraphic record of Upper Cretaceous-Lower
Tertiary periods. Earlier studies have documented variations of clay mineral assemblages, change in microtexture of siliciclasts
and many geochemical and stable isotopic anomalies far below the Cretaceous-Tertiary boundary (KTB) in these strata. This
paper documents the occurrences of two positive 87Sr/86Sr anomalies preceding K-T boundary in this basin and discusses plausible causes. Analysis of trace elemental and stable isotopic
profiles, sedimentation history, petrography and mineralogy of the rocks reveal that while both the anomalies may be due to
increased detrital influx caused by sea level and climatic changes, the second anomaly might have been influenced by Deccan
volcanism which in turn predated KTB. Record of such anomalies preceding K-T boundary supports the view of multi-causal step-wise
extinction of biota across KTB. 相似文献
532.
Vincent Sastre Jean-Luc Loizeau Jens Greinert Lieven Naudts Philippe Arpagaus Flavio Anselmetti Walter Wildi 《Swiss Journal of Geoscience》2010,103(1):33-42
The current topographic maps of the Rhone Delta—and of Lake Geneva in general—are mainly based on hydrographic data that were
acquired during the time of F.-A. Forel at the end of the nineteenth century. In this paper we present results of a new bathymetric
survey, based on single- and multi-beam echosounder data. The new data, presented as a digital terrain model, show a well-structured
lake bottom morphology, reflecting depositional and erosional processes that shape the lake floor. As a major geomorphologic
element, the sub-aquatic Rhone Delta extends from the coastal platform to the depositional fans of the central plain of the
lake at 310 m depth. 9 canyons cut the platform edge of the delta. These are sinuous (“meandering”) channels formed by erosional
and depositional processes, as indicated by the steep erosional canyon walls and the depositional levees on the canyon shoulders.
Ripples or dune-like morphologies wrinkle the canyon bottoms and some slope areas. Subaquatic mass movements are apparently
missing on the delta and are of minor importance on the lateral lake slopes. Morphologies of the underlying bedrock and small
local river deltas are located along the lateral slopes of Lake Geneva. Based on historical maps, the recent history of the
Rhone River connection to the sub-aquatic delta and the canyons is reconstructed. The transition from three to two river branches
dates to 1830–1840, when the river branch to the Le Bouveret lake bay was cut. The transition from two to one river branch
corresponds to the achievement of the correction and dam construction work on the modern Rhone River channel between 1870
and 1880. 相似文献