Monitoring Subsurface Microbial Ecology in a Sulfate-Amended, Gasoline-Contaminated Aquifer   总被引：3，自引：0，他引：3  

Kerry Sublette  Aaron Peacock  David White  Greg Davis  Dora Ogles  David Cook  Ravi Kolhatkar  Dennis Beckmann  Xiaomin Yang 《Ground Water Monitoring & Remediation》2006,26(2):70-78

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Surface Ice Flow Velocity and Tide Retrieval of the Amery Ice Shelf using Precise Point Positioning   总被引：8，自引：1，他引：8  

Xiaohong Zhang  Ole B. Andersen 《Journal of Geodesy》2006,80(4):171-176

Five days of continuous GPS observation data were collected in the frontal zone of the Amery ice shelf and subsequently post-processed using precise point position (PPP) technology based on precise orbit and clock products from the International GNSS service. The surface ice flow velocity of the observed point was derived from PPP to be 2.25 m/day toward the northeast with an azimuth of 41°. Major semi-diurnal and diurnal oceanic tide constituents could be recovered from the 5 days of PPP-derived height variations and compared well with a hydrodynamic ocean tide model. The PPP technique can replace double-difference GPS positioning in remote or hostile environments, and be used to retrieve the surface ice flow velocity without any reference station. Furthermore, the solution can be derived epoch-by-epoch with accuracy in the centimeters to decimeter range.  相似文献   

Simulation of the Ku-band Radar altimeter sea ice effective scattering surface     

Tonboe  R. Andersen  S. Pedersen  L.T. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(2):237-240

A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model is initialized with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73/spl deg/W; 85/spl deg/N). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard, and ice thickness estimation.  相似文献   

Reconstructing the marine Os/Os record and the particulate flux of meteoritic osmium during the late Cretaceous     

Greg Ravizza 《Geochimica et cosmochimica acta》2007,71(5):1355-1369

Paired analyses of Os isotope composition and concentration of bulk sediment and leachable Os in a metalliferous pelagic clay sequence from the North Pacific, ODP Site 886C, are used to reconstruct the marine Os isotope record and the particulate meteoritic Os flux between 65.5 and 78 Ma. Measured ¹⁸⁷Os/¹⁸⁸Os of bulk sediments ranges from approximately 0.64 to 0.32 and those of leach analyses are very similar to bulk analyses. Hydrogenous Os dominates the sedimentary Os inventory throughout most of the studied interval. As a result the measured ¹⁸⁷Os/¹⁸⁸Os of leachable Os approximates that of contemporaneous seawater. The ODP 886C record shows rising ¹⁸⁷Os/¹⁸⁸Os in the deepest portion of the core, with a local maximum of 0.66 close to 74 Ma. The 67-72 Ma portion of the record is characterized by nearly constant ¹⁸⁷Os/¹⁸⁸Os ratios close to 0.6. The structure of the marine Os isotope record from ODP 886C differs markedly from the seawater ⁸⁷Sr/⁸⁶Sr curve, which rises monotonically throughout the time interval studied here. Calculated particulate meteoritic Os fluxes are between 0.5 and 2 pg cm⁻² kyr⁻¹ throughout most of the studied interval. Two discrete intervals of the core (one of which is within Cretaceous Tertiary, boundary KTB interval) are characterized by higher fluxes of meteoritic Os. Excluding these two intervals, the average background flux of particulate meteoritic Os is roughly half of that estimated from analyses of Cenozoic marine sediments. These are the first Os isotope data to provide evidence of resolvable temporal variations in the background flux of particulate meteoritic material to the Earth.  相似文献   

IAG Newsletter     

O. B. Andersen 《Journal of Geodesy》1998,72(11):666-671

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IAG Newsletter     

Ole Baltazar Andersen 《Journal of Geodesy》1998,72(4):245-250

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IAG Newsletter     

O. B. Andersen 《Journal of Geodesy》1998,72(9):557-560

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IAG Newsletter     

Ole Baltazar Andersen 《Journal of Geodesy》1998,72(5):313-321

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Tertiary compressional structures on the Faroe–Rockall Plateau in relation to northeast Atlantic ridge-push and Alpine foreland stresses     

L. O. Boldreel  M. S. Andersen 《Tectonophysics》1998,300(1-4):13-28

A number of compressional anticlinal structures are identified in the western and northern part of the Faroe–Rockall Plateau. These structures occur on that part of the Faroe–Rockall Plateau which was above sea level during the latest phase of Paleocene plateau basalt extrusion. Three post-basalt compressional phases have affected the plateau. Most of the compressional structures in the northern part of the plateau are related to NE–SW- to ENE–WSW-oriented stress which we date to Late Paleocene–Early Eocene. The Oligocene phase is interpreted as resulting from N–S-directed compressional stress which also mainly affected the compressional structures on the northern part of the plateau. Compressional stress from the northwest seemed to affect the whole of the Faroe–Rockall Plateau and we suggest it to be of Miocene age. It is proposed that during the Late Paleocene–Early Eocene phase of compression local structure, and anomalously oriented gravitational ridge-push from the now extinct Aegir Axis contributed to a local NE–SW compressional stress system. The two later deformation phases were apparently connected to the regional northwest European stress system with small local modifications.  相似文献   

Origin of the Blue Ridge escarpment along the passive margin of Eastern North America   总被引：1，自引：0，他引：1  

James A. Spotila  Greg C. Bank  Peter W. Reiners†  Charles W. Naeser‡  Nancy D. Naeser‡  Bill S. Henika 《Basin Research》2004,16(1):41-63

The Blue Ridge escarpment is a rugged landform situated within the ancient Appalachian orogen. While similar in some respects to the great escarpments along other passive margins, which have evolved by erosion following rifting, its youthful topographic expression has inspired proposals of Cenozoic tectonic rejuvenation in eastern North America. To better understand the post‐orogenic and post‐rift geomorphic evolution of passive margins, we have examined the origin of this landform using low‐temperature thermochronometry and manipulation of topographic indices. Apatite (U–Th)/He and fission‐track analyses along transects across the escarpment reveal a younging trend towards the coast. This pattern is consistent with other great escarpments and fits with an interpretation of having evolved by prolonged erosion, without the requirement of tectonic rejuvenation. Measured ages are also comparable specifically to those measured along other great escarpments that are as much as 100 Myr younger. This suggests that erosional mechanisms that maintain rugged escarpments in the early post‐rift stages may remain active on ancient passive margins for prolonged periods. The precise erosional evolution of the escarpment is less clear, however, and several end‐member models can explain the data. Our preferred model, which fits with all data, involves a significant degree of erosional escarpment retreat in the Cenozoic. Although this suggests that early onset of topographic stability is not required of passive margin evolution, more data are required to better constrain the details of the escarpment's development.  相似文献