Structure and sediment distribution in the western Bering Sea     

Philip D. Rabinowitz  Alan Cooper 《Marine Geology》1977,24(4):309-320

Eleven seismic reflection profiles across Shirshov Ridge and the adjacent deep-water sedimentary basins (Komandorsky and Aleutian Basins) are presented to illustrate the sediment distribution in the western Bering Sea. A prominent seismic reflecting horizon, Reflector P (Middle—Late Miocene in age), is observed throughout both the Aleutian and Komandorsky Basins at an approximate subbottom depth of 1 km. This reflector is also present, in places, on the flanks and along the crest of Shirshov Ridge. The thickness of sediments beneath Reflector P is significantly different within the two abyssal basins. In the Aleutian Basin, the total subbottom depth to acoustic basement (basalt?) is about 4 km, while in the Komandorsky Basin the depth is about 2 km.Shirshov Ridge, a Cenozoic volcanic feature that separates the Aleutian and Komandorsky Basins, is an asymmetric bathymetric ridge characterized by thick sediments along its eastern flank and steep scarps on its western side. The southern portion of the ridge has more structural relief that includes several deep, sediment-filled basins along its summit.Velocity data from sonobuoy measurements indicate that acoustic basement in the Komandorsky Basin has an average compressional wave velocity of 5.90 km/sec. This value is considerably larger than the velocities measured for acoustic basement in the northwestern Aleutian Basin (about 5.00 km/sec) and in the central Aleutian Basin (5.40–5.57 km/sec). In the northwestern Aleutian Basin, the low-velocity acoustic basement may be volcaniclastic sediments or other indurated sediments that are overlying true basaltic basement. A refracting horizon with similar velocities (4.6–5.0 km/sec) as acoustic basement dips steeply beneath the Siberian continental margin, reaching a maximum subbottom depth of about 8 km. The thick welt of sediment at the base of the Siberian margin may be the result of sediment loading or tectonic depression prior to Late Cenozoic time.  相似文献   

Comparative biomonitors of coastal trace metal contamination in tropical South America (N. Brazil)     

e Silva CA  Smith BD  Rainbow PS 《Marine environmental research》2006,61(4):439-455

Samples of 5 bivalve molluscs (Crassostrea rhizophorae, Mytella charruana, Anomalocardia brasiliana, Anadara ovalis, Phacoides pectinata), 2 barnacles (Fistulobalanus citerosum, Balanus amphitrite) and leaves of the mangrove tree Rhizophora mangle were collected from up to 11 sites in two estuaries in Natal, Brazil--the comparatively contaminated Potengi estuary and the comparatively uncontaminated Curimataú estuary. Specimens were analysed for the trace metals Zn, Cu, Cd, Fe, Mn and Ni, and a comparative assessment made of the power of the different species as trace metal biomonitors. Four of the 5 bivalves (not P. pectinata) take up metals from solution and suspended material (food source), while P. pectinata as a lucinid with symbiotic chemosynthetic bacteria takes up metals from dissolved sources only. The organisms with the strongest net accumulation of particular metals showed the greatest discrimination between trace metal bioavailabilities between sites. Barnacles (F. citerosum) showed the best discrimination, but oysters (C. rhizophorae) are particularly recommended as biomonitors given their strong accumulation patterns for many trace metals, their large size and their local abundance.  相似文献   

The Stability Properties of Astrophysical Jets     

Philip E. Hardee 《Astrophysics and Space Science》2004,293(1-2):117-129

The basic theoretical stability properties and normal mode structures of astrophysical jets are reviewed. Simulations designed to examine the nonlinear development of instability and some results from comparison between simulations and theory are presented. The potential use of observed normal mode structures in jets is discussed.  相似文献   

EARLY CHALLENGES TO DAVIS'CONCEPT OF THE CYCLE OF EROSION     

Philip Tilley 《The Professional geographer》1968,20(4):265-269

  相似文献   

Sauer,Archives, and Recollections     

Philip W. Porter 《The Professional geographer》1988,40(3):337-339

  相似文献   

    

G. M. Philip  D. F. Watson 《Mathematical Geology》1986,18(1):93-117

Components of geostatistical estimation, developed as a method for ore deposit assessment, are discussed in detail. The assumption that spatial observations can be treated as a stochastic process is judged to be an inappropriate model for natural data. Problems of semivariogram formulation are reviewed, and this method is considered to be inadequate for estimating the function being sought. Characteristics of bivariate interpolation are summarized, highlighting kriging limitations as an interpolation method. Limitations are similar to those of inverse distance weighted observations interpolation. Attention is drawn to the local bias of kriging and misplaced claims that it is an optimal interpolation method. The so-called estimation variance, interpreted as providing confidence limits for estimation of mining blocks, is shown to be meaningless as an index of local variation. The claim that geostatistics constitutes a new science is examined in detail. Such novelties as exist in the method are shown to transgress accepted principles of scientific inference. Stochastic modeling in general is discussed, and purposes of the approach emphasized. For the purpose of detailed quantitative assessment it can provide only prediction qualified by hypothesis at best. Such an approach should play no part in ore deposit assessment where the need is for local detailed inventories; these can only be achieved properly through local deterministic methods, where prediction is purely deductive.EDITOR-IN-CHIEF'S NOTE: The Editorial Board has long recognized the desirability of greater open discussion and comment of timely topics in the journal. Therefore, I solicited the following contribution from Professors Philip and Watson and a response to their paper from Professor Journel. In addition, Journel sent to me comments by a student, Srivastava. None of these three papers has undergone reviewing by other workers in the field as normally is required byMathe-matical Geology. We thank these authors for their papers and hope that these discussions will be beneficial to all our readers.  相似文献   

Galaxy magnitudes     

Gerald E. Kron  C. D. Shane 《Astrophysics and Space Science》1976,39(2):401-407

Systematic corrections to the magnitudes of galaxies in the Zwicky and the Shapley-Ames catalogues have been determined and are tabulated here. The corrections are based on the photographic measures by Holmberg, published photoelectric measures, and 392 photoelectric measures by Kron and Shane. These latter are mostly in the fainter magnitude range. The corrections for Volume I of the Zwicky Catalogue differ substantially from those for Volumes II to VI.  相似文献   

Some photometric properties of the Martian south polar cap region during the 1971 apparition     

Kari Lumme  Philip B. James 《Icarus》1984,58(3):363-376

High-quality Earth-based photographs from the Lowell Observatory Planetary Research Center collection have been analyzed to derive some photometric parameters for the Martian south polar cap region during the 1971 apparition. The optical thickness of the atmosphere above the cap varied with wavelength from 0.35 ± 0.05 in red light to 0.58 ± 0.06 inuv light. The effective geometric albedo is calculated from the 30° phase data assuming isotropic scattering; it varies from 0.85 ± 0.04 (in red light) to 0.63 ± 0.05 (in uv light).  相似文献   

A sonic well log of the basement complex of the Walvis Ridge     

Philip D. Rabinowitz  Peter E. Borella 《Geo-Marine Letters》1984,3(1):1-7

A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ∼-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval.  相似文献   

Measures of variability for geological data     

D. F. Watson  G. M. Philip 《Mathematical Geology》1989,21(2):233-254

Diverse global and local measures of variability appear in the geological literature and, along with methods used to apply them, have been subject to some debate. Measures of variability for three data types—replicate, locational, and compositional—are considered; the source and nature of the variability determine the appropriate type of measure. To illustrate the effects of these measures and expose their inadequacy when improperly applied, the variability of a three-column data set is interpreted under three different suppositions. Geologists need to be aware of the confusion and misleading results that can develop from the use of variance as a measure of variability for locational or compositional data.  相似文献