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Eastern Basin (eastern + basin)
Selected AbstractsHudson Strait ice streams: a review of stratigraphy, chronology and links with North Atlantic Heinrich eventsBOREAS, Issue 1 2003John T. Andrews We review the literature on the occupation of Hudson Strait (800 km long by 90 km wide) by late Quaternary ice streams, and the importance of Hudson Strait as the major source for sediments associated with the North Atlantic Heinrich (H-) events. Glacial erosion of the Paleozoic outcrop on the floor of Hudson Strait and Ungava Bay resulted in the export of detrital carbonate-rich sediments to ice-proximal locations on the slope and floor of the NW Labrador Sea, mainly in meltwater and turbidite plumes, and to ice distal sites thousands of kilometres away largely as iceberg-rafted detritus (IRD). Erosion of bedrock from the Precambrian Superior and Churchill provenances of the Canadian Shield is also indicated by the isotopic analyses of sediments. The major late Quaternary H-events (H-4, H-2 and H-1) are represented in southeast Baffin Island slope sediments as detrital carbonate-rich intervals up to 40 cm in thickness and appear to represent flow along the axis of the Strait. However, the late marine isotope stage #3 event, H-3 (,27 ka), and a younger event (H-0, ,11 ka), are not as dominant in the sedimentary record and probably represent a different glaciological regime with flow across Hudson Strait from eastern Ungava-Labrador. The freezing-on of sediments by supercooling in the rise from the 900 m deep Eastern Basin to the 400 m sill is proposed as the source of the abundant carbonate-rich glaciomarine sediments some 250 km from the outcrop in Eastern Basin. Sediment transport by meltwater and turbidity currents was the major process during H-events in ice-proximal settings. IRD was not a key diagnostic process at sites fronting Hudson Strait. A key feature in the instability of this ice stream might be the great depth (600 m) at the shelf break, and the deep basin, which lies seaward of the outer Hudson Strait sill. [source] BARGEN continuous GPS data across the eastern Basin and Range province, and implications for fault system dynamicsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004Nathan A. Niemi SUMMARY We collected data from a transect of continuous Global Positioning System (GPS) sites across the eastern Basin and Range province at latitude 39°N from 1997,2000. Intersite velocities define a region ,350 km wide of broadly distributed strain accumulation at ,10 nstr yr,1. On the western margin of the region, site EGAN, ,10 km north of Ely, Nevada, moved at a rate of 3.9 ± 0.2 mm yr,1 to the west relative to site CAST, which is on the Colorado Plateau. Velocities of most sites to the west of Ely moved at an average rate of ,3 mm yr,1 relative to CAST, defining an area across central Nevada that does not appear to be extending significantly. The late Quaternary geological velocity field, derived using seismic reflection and neotectonic data, indicates a maximum velocity of EGAN with respect to the Colorado Plateau of ,4 mm yr,1, also distributed relatively evenly across the region. The geodetic and late Quaternary geological velocity fields, therefore, are consistent, but strain release on the Sevier Desert detachment and the Wasatch fault appears to have been anomalously high in the Holocene. Previous models suggesting horizontal displacement rates in the eastern Basin and Range near 3 mm yr,1, which focused mainly along the Wasatch zone and Intermountain seismic belt, may overestimate the Holocene Wasatch rate by at least 50 per cent and the Quaternary rate by nearly an order of magnitude, while ignoring potentially major seismogenic faults further to the west. [source] Seasonal Dynamics of Picocyanobacteria and Picoeukaryotes in a Large Shallow Lake (Lake Balaton, Hungary)INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2006Andrea Mózes Abstract The abundance and composition of autotrophic picoplankton (APP) were studied between February 2003 and March 2004 in Lake Balaton. Water samples were taken fortnightly in the eutrophic western basin and mesotrophic eastern basin. Our study, which took more than one year, revealed pronounced seasonal pattern of the picoplankton abundance and composition. According to our results there were three types of picoplankton in Lake Balaton: 1. Phycoerythrin-rich coccoid cyanobacteria (PE), dominant summer picoplankters in the mesotrophic lake area; 2. Phycocyanin-rich cyanobacteria (PC), the most abundant summer picoplankters in the eutrophic lake area; 3. Picoeukaryotes, dominant winter picoplankters in the whole lake. The observed abundance of picoeukaryotes (3 × 105 cells ml,1) was one of the highest ever found. Our study confirms that in Lake Balaton the colonial autotrophic picoplankton (colonial APP) become dominant in summer in the nutrient limited period. We have found strong negative relationship between the concentrations of available nitrogen forms (NH4,N, NO3,N, urea-N) and the colonial APP abundance. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large-scale distribution and activity patterns of an extremely low-light-adapted population of green sulfur bacteria in the Black SeaENVIRONMENTAL MICROBIOLOGY, Issue 5 2010Evelyn Marschall Summary The Black Sea chemocline represents the largest extant habitat of anoxygenic phototrophic bacteria and harbours a monospecific population of Chlorobium phylotype BS-1. High-sensitivity measurements of underwater irradiance and sulfide revealed that the optical properties of the overlying water column were similar across the Black Sea basin, whereas the vertical profiles of sulfide varied strongly between sampling sites and caused a dome-shaped three-dimensional distribution of the green sulfur bacteria. In the centres of the western and eastern basins the population of BS-1 reached upward to depths of 80 and 95 m, respectively, but were detected only at 145 m depth close to the shelf. Using highly concentrated chemocline samples from the centres of the western and eastern basins, the cells were found to be capable of anoxygenic photosynthesis under in situ light conditions and exhibited a photosynthesis,irradiance curve similar to low-light-adapted laboratory cultures of Chlorobium BS-1. Application of a highly specific RT-qPCR method which targets the internal transcribed spacer (ITS) region of the rrn operon of BS-1 demonstrated that only cells at the central station are physiologically active in contrast to those at the Black Sea periphery. Based on the detection of ITS-DNA sequences in the flocculent surface layer of deep-sea sediments across the Black Sea, the population of BS-1 has occupied the major part of the basin for the last decade. The continued presence of intact but non-growing BS-1 cells at the periphery of the Black Sea indicates that the cells can survive long-distant transport and exhibit unusually low maintenance energy requirements. According to laboratory measurements, Chlorobium BS-1 has a maintenance energy requirement of ,1.6,4.9·10,15 kJ cell,1 day,1 which is the lowest value determined for any bacterial culture so far. Chlorobium BS-1 thus is particularly well adapted to survival under the extreme low-light conditions of the Black Sea, and can be used as a laboratory model to elucidate general cellular mechanisms of long-term starvation survival. Because of its adaptation to extreme low-light marine environments, Chlorobium BS-1 also represents a suitable indicator for palaeoceanography studies of deep photic zone anoxia in ancient oceans. [source] | |||||||||||||