PERMEABILITY AND CONSOLIDATION OF SEDIMENT MIXTURES AS FUNCTION OF SAND CONTENT AND CLAY MINERALOGY   总被引：1，自引：0，他引：1  

W. JACOBS W. G. M. VAN KESTEREN J. C. WINTERWERP 《国际泥沙研究》2007,22(3):180-187

The current study is the first step in a systematic experimental research on the erosion behaviour of sand-mud mixtures. It concerns the effect of a varying sand content and clay mineralogy on the porosity, structure, strength and permeability of artificially generated sediment mixtures. The permeability of a sediment mixture is an especially significant parameter concerning the type of erosion that occurs. It determines if the erosion of the bed is either a drained or an undrained process, respectively indicating surface erosion or mass erosion. Measurements on various mixtures concerning the consolidation coefficient and the permeability have been executed. Results show a distinct transition of behaviour between a sand-silt dominated network structure and a clay-water matrix. The occurrence of these two types of structures appears to depend on the porosity of the volume fraction of sand related to silt, which is, therefore, an important parameter concerning the type of erosion. Finally, the study provides a valuable data set that can be used as a reference for following stages of this research on the erosion behaviour of natural cohesive sediments.  相似文献   

Anatomy of a modern open-ocean carbonate slope: northern Little Bahama Bank   总被引：1，自引：0，他引：1  

HENRY T. MULLINS  KATHRYN C. HEATH†  H. MARK VAN  BUREN† CATHRYN R. NEWTON 《Sedimentology》1984,31(2):141-168

The open-ocean carbonate slope north of Little Bahama Bank consists of a relatively steep (4°) upper slope between water depths of 200 and 900 m, and a more gentle (1–2°) lower slope between depths of 900 and 1300+ m. The upper slope is dissected by numerous, small, submarine canyons (50–150 m in relief) that act as a line source for the downslope transport of coarse-grained carbonate debris. The lower slope is devoid of any well-defined canyons but does contain numerous, small (1–5 m) hummocks of uncertain origin and numerous, larger (5–40 m), patchily distributed, ahermatypic coral mounds. Sediments along the upper slope have prograded seaward during the Cenozoic as a slope-front-fill seismic facies of fine-grained peri-platform ooze. Surface sediments show lateral gradation of both grain size and carbonate mineralogy, with the fine fraction derived largely from the adjacent shallow-water platform. Near-surface sedimentary facies along the upper slope display a gradual downslope decrease in the degree of submarine cementation from well-lithified hardgrounds to patchily cemented nodular ooze to unlithified peri-platform ooze, controlled by lateral variations in diagenetic potential and/or winnowing by bottom currents. Submarine cementation stabilizes the upper part of the slope, allowing upbuilding of the platform margin, and controls the distribution of submarine slides, as well as the headward extent of submarine canyons. Where unlithified, sediments are heavily bioturbated and are locally undergoing dolomitization. Upper slope sediments are also ‘conditioned’eustatically, resulting in vertical, cyclic sequences of diagenetically unstable (aragonite and magnesian calcite-rich) and stable (calcite-rich) carbonates that may explain the well-bedded nature of ancient peri-platform ooze sequences. Lower slope sediments have prograded seaward during the Cenozoic as a chaotic-fill seismic facies of coarse-grained carbonate turbidites and debris flow deposits with subordinate amounts of peri-platform ooze. Coarse clasts are ‘internally’derived from fine-grained upper slope sediments via incipient cementation, submarine sliding and the generation of sediment gravity flows. Gravity flows bypass the upper slope via a multitude of canyons and are deposited along the lower slope as a wedge-shaped apron of debris, parallel to the adjacent shelf edge, consisting of a complex spatial arrangement of localized turbidites and debris flow deposits. A proximal apron facies of thick, mud-supported debris flow deposits plus thick, coarse-grained, Ta turbidites, grades seaward into a distal apron facies of thinner, grain-supported debris flow deposits and thinner, finer grained Ta-b turbidites with increasing proportions of peri-platform ooze. Both the geomorphology and sedimentary facies relationships of the carbonate apron north of Little Bahama Bank differ significantly from the classic submarine fan model. As such, a carbonate apron model offers an alternative to the fan model for palaeoenvironmental analysis of ancient, open-ocean carbonate slope sequences.  相似文献   

Accurate Determination of Gallium in South African Primary and Secondary Reference Samples by Ion Exchange Chromatography and Atomic Absorption Spectrometry     

T.N. VAN DER WALT  F.W.E. STRELOW 《Geostandards and Geoanalytical Research》1984,8(2):163-167

Results are presented for gallium in six South African primary rock standards (NIMROCS) and in twelve secondary rock standards (SAROCS). A selective ion exchange procedure is used to separate gallium completely from all other elements, except remaining traces of thorium. It is followed by a determination of gallium with flame atomic absorption spectrometry using the nitrous oxide-acetylene flame, after the addition of 2000 ppm lanthanum as ionization suppressor.  相似文献   

The hydraulic interpretation of turbidites from their grain sizes and sedimentary structures     

JAY VAN  TASSELL 《Sedimentology》1986,33(3):437-438

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Bedform migration and bed-load transport in some rivers and tidal environments     

JAN H. VAN DEN  BERG 《Sedimentology》1987,34(4):681-698

Reliable field data obtained by directly measuring bed-load transport of fine- to coarse-grained bed material are extremely scarce, mainly because of the difficulty of sampling accurately. Therefore, the verification of bed-load transport formulae is largely based on flume experiments, which refer to unrealistic shallow-water conditions. In this study, some bed-load transport formulae were tested against data from natural environments. As an alternative to ascertaining the bed-load transport rate by sampling the bed-load, the transport rate was deduced from data on bedform height and bedform celerity. For this purpose, 43 sets of data from rivers, representing a wide range of bed material, bedform dimensions and hydraulic conditions were collected as were some sets of data from tidal settings. Two formulae were used for the prediction of the bed-load transport: the formula of Van Rijn (1981) and the Kalinske (1947) formula as approximated by Elzerman & Frijlink (1951) (and, in the present study, slightly modified for application to tidal waters). Both the bed-load function of Van Rijn and the modified formula of Kalinske-Frijlink require data which are easily obtained and that can be measured accurately. At those stages of the flow when bed-load transport was high the Van Rijn function tended to overestimate that transport. For flow stages when bed-load transport was low the opposite was true. The modified Kalinske-Frijlink function gave consistently good results: 86% of the transport rates predicted using the river data were within 0·5–2·0 times the values actually measured.  相似文献   

THERMAL NEAR-SURFACE EXPRESSION OF SHALLOW GEOLOGICAL FEATURES*     

J. PH. POLEY  J. VAN STEVENINCK 《Geophysical Prospecting》1971,19(4):695-697

It has been customary in geothermal studies to assume the surface to be an isothermal plane, though difficulties existed to explain the magnitude of thermal anomalies observed in the field under this assumption. Detailed investigations of temperatures at depths between 5 cm and 230 cm show that—after removal of the strong diurnal variations—sizeable anomalies persist right to the surface. Thus, the effective heat transfer (coefficient) at the surface might be lower than commonly assumed.  相似文献   

INFLUENCE OF AMPLITUDE AND PHASE ERRORS ON MIGRATION RESULTS*     

L. F. VAN DER WAL  A. J. BERKHOUT 《Geophysical Prospecting》1984,32(3):425-453

Random amplitude and phase errors in seismic input data introduce a coherent distribution of migration half-circles or “smiles”, the occurrence of which may cause a significant decrease of signal-to-noise ratio. In addition, the effect of quantization errors is discussed for different wordlengths, used both during acquisition and during data processing. Results of sign-bit recordings are shown.  相似文献   

Microbiota of Salt Lakes as Food for the Brine Shrimp Artemia     

Gilbert VAN STAPPEN  Thanh Toi HUYNH  Nguyen Van Ho  SUI Liying  DENG Yuangao  Peter BOSSIER 《《地质学报》英文版》2014,88(Z1):105-105

正The brine shrimp Artemia is often abundantly found in hypersaline environments.The larvae(‘nauplii’)hatching from its dormant embryos(‘cysts’)are a crucial live food item for the larval stages of fish and shrimp in aquaculture  相似文献   

Siliceous Cementation of Chlorite-Coated Grains in the Permian Sandstone Gas Reservoirs, Ordos Basin     

FAN Aiping  YANG Renchao  LI Jinbu  ZHAO Zhongjun  A.J. 《《地质学报》英文版》2017,91(3):1147-1148

<正>Objective It has long been controversial that whether authigenic chlorite coatings in sandstone reservoirs can prevent precipitation of siliceous cements.It is commonly believed that chlorite coatings(also called chlorite films,chlorite linings,or chlorite rims)may prevent quartz overgrowth,and thus help the preservation of original pores in sandstone reservoirs.Recently,however,this assumption has been challenged by reservoir geologists.This dispute cannot be solved by mere analysis of thin sections,nor by chemical equations and diagenesis analysis.The main objective of the present contribution is to shed light on this  相似文献   

EFFECT OF MODEL STRUCTURE ON THE ACCURACY AND UNCERTAINTY OF RESULTS FROM WATER QUALITY MODELS     

M. VAN DER PERK 《水文研究》1997,11(3):227-239

Eight one-dimensional steady-state models with different complexity, which describe the phosphate concentration as a function of the distance along a river, were examined with respect to accuracy and uncertainty of the model results and identifiability of the model parameters by means of combined calibration and sensitivity analysis using Monte Carlo simulations. In addition, the models were evaluated by the Akaike information criterion (AIC). All eight models were calibrated on the same data set from the Biebrza River, Poland. Although the accuracy increases with model complexity, the percentage of explained variance is not significantly improved in comparison with the model that describes the phosphate concentration by means of three parameters. This model also yields the minimum value of the AIC and the parameters could be well identified. Identification of the model parameters becomes poorer with increasing model complexity; in other words the parameters become increasingly correlated. This scarcely affects the uncertainty of the model results if correlation is taken into account. If correlation is not taken into account, the uncertainty of model results increases with model complexity. © 1997 by John Wiley & Sons, Ltd.  相似文献