摘要:

ABSTRACTOn experimentally deposited kaolinite, illite, and Ca‐bentonite consolidated under their own load or by additional vertical pressure, the progress of compaction in relation to excess pore water pressure, mass physical properties, gravitational mass movements in a tilted tank, and erodibility under running water in a flume were studied. The very low consolidated sediments near the mud/water interface do not obey the generally used theory in soil mechanics. They show a different, non‐linear relationship between void ratio or water content and depth below the sedimentary surface on the one hand, or effective overburden pressure and shear strength on the other. The same is true of other physical properties such as permeability, which changes considerably with depth and time of consolidation.High sedimentation rates on slopes induce shallow sediment flow, whereas at low rates and critical slope angles different types of slope failures including the breaking up of water‐rich sediment into sharp boundered blocks are observed.Flume studies on soft clay muds show three different types of erosion: continuously suspending, discontinuous erosion of crumbs or shreds, and wavy deformation of the clay surface with disintegration of particles from the crests. The critical tractive stress depends not only on clay type, void ratio, and shear strength, but significantly also on the ‘geologic history’of the clay (i.e. deposition from thin suspension or dense slurry, fabric, consolidation and swelling generating minute inhomogeneities etc.).The experiments may lead to a better understanding of all mechanical processe's including pore‐water flow taking place near or not far below the sediment/ wate

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02065.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe carbon and oxygen isotopic composition of seventy‐nine samples of biogenic carbonates from the Mainz Basin Tertiary (Oligocene and Lower Miocene) was analysed. Most samples were mollusc shells still consisting of aragonite. Assuming only small temperature effects, salinity trends derived from isotope data are consistent with palaeontological results from the region: a salinity cycle ranging from fresh water‐brackish (Lower Oligocene) towards marine (Middle Oligocene) and brackish‐fresh water (Upper Oligocene) was found. Within the Lower Miocene, a trend of decreasing salinities is suggested. Though the isotopic salinity trends coincide rather well with palaeontological salinities, the absolute oxygen isotope ratios indicate an unusual isotopic environment enriched in18O.Isotope fractionation is explained by evaporation of a closed basin (Rupelton excluded) with fresh water influx from surrounding land areas in a subtropical climate. Enrichment in18O by repeated evaporation processes is paralleled by increasing concentration of Sr. Increasing fresh water influx during the Oligocene is due to climatic changes with a trend of more humid conditions towards the younger rock s

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02066.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTMost efforts in the study of sea‐marginal sabkhas have concentrated on the Persian Gulf, but little is known about the sediments and mineralogy of sabkhas marginal to other seas. The purpose of this paper was to present some geochemical and mineralogical observations in a recent sabkha on the coast of Sinai along the Gulf of Suez. The sabkha is composed of coarse clastic sediments with marine‐derived groundwater at depth of about 1 m. The general morphology, climate and water salinity of the Gulf of Suez resemble those of the Persian Gulf, despite the fact that the content of authigenic evaporites in this sabkha is more sparse. The evaporite minerals accumulated only in the upper 30–40 cm of the sabkha, below that and down to the groundwater table, there is no accumulation of evaporites. Laterally, the salinity of the groundwater in the sabkha and the concentration of evaporites in the sediments above it increase constantly with distance from the shore.In contrast to the Persian Gulf where anhydrite is a major evaporite mineral, in Belayim gypsum is the only calcium sulphate mineral in the recent sabkha. Anhydrite is found only in an old elevated sabkha where it recrystallized from gypsum. The gypsum occurs as interstitial crystal concentrations or lithified horizons almost exclusively at the depth of 20–40 cm below the sabkha surface. Above that, in the uppermost horizons, there isin situaccumulation of interstitial halite crystals. The total concentrations of gypsum and halite are almost equal in this sabkha.The sea water recharge in El Belayim is almost exclusively by seepage through the sabkha sediments and not by flooding. The groundwater under this sabkha is only slightly more saline than the Gulf water, thus, not heavy enough for extensive downward refluxing. The major hydrodynamic process must be upward migration of the brines from the groundwater, precipitating on the way gypsum and later halite with some magnesite. Since the sediments of the sabkha are too coarse to support extensive capillary movement, the brines must, therefore, migrate upwards due to ‘evaporative

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02067.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

RÉSUMÉLe gypse, comme la plupart des minéraux, contient en inclusions des liquides contemporains de la cristallisation dont l'analyse permet de connaítre la composition du milieu de genèse—le rôle des circulations secondaires devant être discuté.Nous avons choisi de déterminer les rapports Cl/Br des inclusions car ce rapport est constant dans l'eau marine actuelle et bien connu dans de nombreux types d'eaux naturelles qu'il caractérise.L'activation neutronique permet de doser les très faibles quantités de chlore et de brome qui se trouvent dans les cavités mesurant en moyenne 10−6mm3.Cette technique n'a encore été que très rarement utilisée dans l'etude des inclusions et la méthode mise au point ici écarte tout risque de pollution et donne directement le rapport Cl/Br (á 10% près) après une seule irradiation par échantillon.Nous rapportons les résultats de 58 manipulations faites sur une douzaine de gisements de types différents; leur étude microcryoscopique avait été effectuée au préalable.La connaissance des salinités (en équivalents NaCl) et des rapports Cl/Br des inclusions liquides nous permet de proposer des hypothèses génétiques pour les gisements anciens d'origine discutée, aprés comparaison avec les gisements actuels ou récents.Ont étéétudiés des cristaux de gypse primaires de marais salants de France, de mangrove de Nouvelle‐Calédonie, de la Sebkha el Melah en Tunisie, ainsi que des cristaux éocènes du bassin de Paris, ol

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02068.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe Upper Calcareous Grit, the last of the four upward shallowing cycles that comprise the Corallian Beds of southern England, is relatively enriched in iron minerals, having local developments of chamosite oolite mudstone and much more widespread deposits of sand and mud containing variable amounts of siderite and disseminated chamosite. The chamosite oolite mudstones have a restricted fauna dominated by oysters and probably accumulated in slightly hyposaline lagoons where the ooids formed from mixed iron‐, alumina‐ and silica‐bearing gels. Siderite was produced during diagenesis from iron carried on the surface of clay minerals. This intimate association with the terrigenous clay fraction means that siderite occurs in sediments deposited in a variety of environments ranging from offshore shelf to lagoonal.The most important factor responsible for ironstone development was a very low rate of clastic supply throughout Upper Calcareous Grit times. The iron was probably derived by normal processes of weathering and erosion of sedimentary rocks exposed around the basin margin, but this cannot be conclusively proved and quite different iron sources may have been inv

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02069.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTPrimary sedimentary structures and sedimentary textures of the Pleistocene fluvial sediments of the Columbia Formation were investigated both in the outcrops and in the subsurface. Three hundred and thirty‐one subsurface samples, taken from forty holes, and fifty‐six outcrop samples were analysed in the laboratory and the results were statistically treated. Unknown sedimentary structures were recognized in the subsurface by correlating some textural parameters (mean grain size, skewness, and kurtosis) of the drilling (subsurface) samples with those of the outcrop samples where the sedimentary structures were known. The utilization of both the sedimentary structures and the textures made it possible to recognize major morphologic elements of a Pleistocene stream system (channels, channel bars, floodbasins, and channel‐fills) in the subsurface and to reconstruct, in a general way, the events that occurred during the existence of the stream system. It seems that in the initial stages of the Columbia deposition, the streams were confined to the valleys in the underlying surface made up of the Palaeocene‐Eocene glauconitic greensands. After the valleys were filled with the Pleistocene sediments, the streams were able to shift their channels freely throughout the study area; at least two new tributary streams were added to the system and a major flood occurred during that time.Although the technique of the recognition of primary sedimentary structures in the subsurface employed in this study has shown useful in the interpretation of the fluvial sedimentary bodies, it needs further testing before it can be accepted as a new geolog

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02070.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTClay minerals of about 600 samples from drill cores in the Tertiary shales of the Rhinegraben, were analysed by X‐ray diffraction methods. It was found that the abundance of smectite decreases with increasing amounts of mixed layer clays and illites, suggesting a diagenetic alteration of smectite with increasing temperatures of the sediments as was also observed in other sedimentary basins.As for the relation between smectite alteration and temperatures as measured in sample depths, in the marine Graue Schichtenfolge (Middle Oligocene) when temperatures reach 70°C and over, smectite no longer is to be found. In the limnic Bunte Niederröderner Schichten (Upper Oligocene) the maximum temperature of smectite occurrence is about 80°C. These temperatures also fit the results of former field studies of the thermal stability of smectite.In the brackish to limnic Obere and Untere Hydrobienschichten (Lower Miocene) however, smectite seems to have disappeared already at a temperature of over 30°C. Although the smectite distribution in the latter formations may depend partly on its inhomogenous deposition there is also evidence for the diagenetic alteration of smectite in these formations. The rapid disappearance of smectite in these formations was possibly caused by a greater availability of potassium ions since high permeability of these strata provide extraordinarily good mobility of the pore solutions.In the older Lymnäenmergel formation (Upper Eocene) a more advanced stage of smectite alteration is found as compared to the other formations at corresponding temperatures. This is considered to be the consequence of the longer duration of diagenesis and the rock salt inclusions of this saline formation which might have enriched the pore solutions with potassiu

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02071.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTA core from the southern mesotrophic basin of Lake George, New York, shows enrichment in the concentration of trace elements near its top. By contrast, a core from the northern oligotrophic basin shows, with the exception of manganese, an almost constant trace‐element concentration throughout the core. Man's activities in the watershed surrounding the southern basin are responsible for enrichment in the trace‐element concentration of newly deposited bottom sediments. Increase in trace‐element concentration is not paralleled by increase in organic‐carbon concen

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02072.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTFissility in shales appears directly related to the parallel orientation of mineral grains in the rock fabric. In two shale sequences examined, fissility increases along a gradient of decreasing bioturbation. Normal marine mudrocks should be characterized by lack of fissility due to the randomized fabric produced by bioturbation, while azoic marine mudrocks should exhibit good fissility due to the lack of biogenic reworking and the preservation of an originally horizontal particle arrangement.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02073.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Sedimentary Carbonate Minerals.By F. Lippmann.An Introduction to Crystallography.By F. C. Phillips.Marine Evaporites, Origin, Diagenesis, and Geochemistry.Edited by Douglas W. Kirkland and Robert Evans.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02074.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY