摘要:

ABSTRACTAfter summarizing the vast analytical material it was possible to establish the differences in rare‐earth element (REE) distribution in geosynclines and on platforms. It is shown that the heavier REE composition in sediments of geosynclines and the lighter one in sediments of platforms was initially created by processes of endogenic differentiation and then inherited by sedimentary series of these zones. On the basis of the calculation of the REE content in rocks of various shells of the Earth crust the increase of the role of heavy lanthanides into the depths of the crust is shown. The obtained estimate of REE abundance in the lithosphere led to the conclusion that the crust of our planet, despite the repeated reworking of its matter by sedimentary processes, metamorphism and granitization, has inherited features peculiar to products of tholeiitic magmatism—the most widely spread type of mantle fus

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02055.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTA study of cores from thirty‐three coreholes drilled in various parts of the Niger delta has showntidal channel sandto be the dominant lithofacies type in the uppermost 30 m of the deltaic complex. Below 30 m fluviatile sand becomes predominant. Coastal barrier sand is present in the uppermost 5 m of the present coastal belt, but chances for preservation of this lithofacies appear to be small.The Post‐Glacial deltaic sediments can be divided into three units.1Alluvial valley‐fill sands and conglomerates deposited during the strong Post‐Glacial sea level rise.2An onlapping complex of lower coastal plain deposits which contains a lower member of fine grained lagoonal and mangrove swamp deposits and an upper member of tidal channel and coastal barrier sands. This complex is thought to have been deposited during the strong Post‐Glacial rise in sea level and is locally as much as 25 m thick.3An offlapping complex of fluviomarine and coastal deposits which contains a lower member of marine clay and silt and an upper member of tidal channel and coastal barrier sand. The presence of this late Holocene complex indicates that deltaic progradation was resumed as soon as the rapid rise in sea level slowed down. The offlapping complex is locally as much as 3

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02056.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTTo present a model for flysch deposition involves the simultaneous representation of many parameters. The most significant of these are arenite‐lutite bed thickness ratio, mean and variance of arenite‐bed thickness, mean palaeocurrent direction and the primary directional structures yielding them.Field and flume data suggest that arenite‐bed thickness decreases exponentially away from source, with a complementary increase in siltstone bed thickness in a turbidite fan.IfHA,HL.are arenite and lutite bed thicknesses in a couplet (the unit of bedding at a flysch outcrop), thenwheremandRare constants of the outcrop in the turbidite wedge. Field evidence suggestsm= 1, so thatR‐values allow for a classification of couplets at an outcrop or within a zone. MaximumHA,HL.values are indicative of proximal deposition from turbidites, and usually provide transverse directional structures, as does (HA) max.Arenite bed thickness can be considered as thick beds or thin beds according to whether they exceed a chosen thickness, saytcm. If 15 cm be chosen, the percentage thick arenite‐bed thicknessHA1and thin arenite bed thickness percentage,HA2can be represented withHL.(siltstone bed thickness percentage) over twenty‐five couplets, as one point on a triangular diagram. The mean palaeocurrent directionNφ° E is represented as an arrow through the point, a colour (point or arrow) being used to distinguish the directional structure (flute, ripple, groove, foreset, etc.) producing it.Flysch examples from Ordovician, Silurian and Devonian in Central Victoria are thus interpreted in terms of proximal and distal emplacement. In cases where bedding detail is clear, A + B, C and D + E divisions substitute forHA1HA2andHL.respectively, for a unit of 1 m thickness of outcrop on the triangular diagram.If thick arenite bed thickness percentage be plotted against total arenite bed thickness percentage, the linear plot of points for outcrop samples results on log‐log paper. Limiting lines of the form logHA1= m logHA+ logC(m, Cconstants) demarcate the field. Parallel and equally spaced lines with valuesC1,C2,C3,…Cnsubdivide this into sub‐fields. If the determinations forHA1in any one sub‐field be plotted on a locality map considering only MAXIMUMHA1values, and theHA1H values conveniently contoured, trends emerge which closely agree with the modal palaeocurrent directions in the case of the Llandovery Deep Creek Flysch 25 km NNW of

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02057.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe mineralogy and geochemistry of clastic sediments in the 1000 m thick Lower Palaeozoic marine sequence of the Oslo Region is discussed on the basis of 200 chemical (XRF) and mineralogical (X‐ray diffractometer) analyses. The composition of these sediments is considered to largely be a function of the relative supply from land of the continental shield (Baltic Shield) and from island are systems to the NW in the Trondheim Region. The relative abundance of chlorite and illite is discussed in light of recent knowledge about their distribution in modern oceans.Middle Cambrian to Lowermost Ordovician black shales contain only illite as the dominant clay mineral and have a high potassium content. These sediments are thought to be derived from land on the continental shield, which during this period probably had a low relief and a warm climate where chlorite is not stable. Chlorite is introduced first in the Arenigan (L. Ordovician) and this is interpreted as evidence for transport of clastic chlorite from a developing island arc system in the Trondheim Region to the west. The highest chlorite/illite ratio in the Middle and Upper Ordovician sediments of the Oslo Region corresponds to a Taconic orogenic phase. The content of clastic chlorite in the Lower Palaeozoic of the Oslo Region is thus shown to be a sensitive indicator of palaeoenvironment and tectonic evolution of the Caledonian geosyncline.This conclusion is also supported by a systematic increase in Mg, Fe, Ni, and Cr from Lower to Middle and Upper Ordovician beds. High Cr values exceeding 0–1 % Cr in the Middle/Upper Ordovician shales are due to small grains of clastic chromite resembling those in the serpentinites of the Trondheim Region. This also suggests transport from exposed island arcs onto the epicontinental sh

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02058.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTVesiculated tuffs are tuffs that contain vesicles between the ash particles. Formation of the vesicles is the result of trapping of steam, the transporting agent of volcanic base surges, in wet, muddy or sticky ash deposited by the base surges. Vesiculated tuffs are described from various maars and tuff‐rings in Europe (Iceland, France, Germany) and USA together with associated surface features such as: gravity flowage ripples, mud flow channels, current ripples, and current ridges. Other features described are: plastering of ash against obstacles and vesiculated accretionary lapilli, the latter containing vesicles in the outer layer.Vesiculated base surge deposits probably contained as much as 20–30% of interstitial water and fell out of the base surge cloudsen masseowing to non‐free flow and consequent accr

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02059.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTAn association of structures is documented from a Lower Proterozoic carbonate sequence in South Africa: this is dominated by finely laminated material which may display flat (smooth), small domical (blister), crinkled (tufted) and pustular (mamillate) surface. The lamination may display overfolded structures and contain flat encapsulated features. Lens‐like flat‐pebble breccias are common, while edgewise breccias were seen less frequently. Small‐scale features suggestive of vertical algal moulds were also recorded. This facies is considered to be analogous to contemporary tidal flat sedimentation developed in specific settings at Shark Bay in Western Australia, and at Abu Dhabi where it is the dominant growth form. This analogy is most notably clear in relation to the protected embayments at Shark Bay, and as a result, an inner intertidal to marginal supratidal environment is suggested for the specific horizons under consideration from the Transvaal Dolomite.Other structures are associated with this facies. These include larger domes, coarser bedding, oolites, ripple‐marks and, in one case, columnar stromatolites. Using the basic facies as an environmental datum, a model is developed in which these latter structures extend into the outer intertidal zone. They are also considered to be associated with varying states of turbulence in the intertidal

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02060.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTBagnold's (1954) and Kawamura's (1951) formulae may be used for the calculation of the sand movement on a natural beach, provided the shear stress velocityU*>0·D4 m/s. Great discrepancies have been found between calculated and measured sand transport rates forU*<0·D4 m/s, mainly because of the capillary forces acting on a wet beach.The measured critical shear velocityU*cat the beginning of sand movement on a clean dry beach agrees very well with that predicted by Bagnold's formula. On a dry beach where the sand grains are stuck together,U*cwas found to be about 10% higher. On a wet beachU*cappeared to depend on the moisture content of the surface layer. Grain size is a determining parameter in theU*c‐moisture content relation.When the angle a between the wind direction at sea and the dune face is between 15° and 85° the streamlines of the wind will bend in the vicinity of the dune face. In consequence this may influence the direction of sediment mov

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02061.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe thickness frequency distribution of stratigraphic layers intersected by the Apollo 15 deep core suggests that the majority of impact events reworking the lunar soil are small and produce ejecta blankets with an average thickness of less than 1·D5 cm. The energy frequency distribution of the meteorites producing the layers may be bimodal. The impacting meteorites produce both normal and reverse graded beds which appear to be the end products of two depositional mechanisms. First, the normally graded beds appear to be produced in base surges as escaping gases fluidize the flowing debris and larger particles move downwards in response to Stokes Law. Second, if the gas loss from the base surge is excessive the fluidization may cease and inertial grain flow dominates. In this situation the beds are reverse graded as larger particles move under dispersive pressure to the region of minimum shear stress at the upper boundary of the base surge. The same processes also produce measurable shape sorting of the particles in the beds

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02062.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTDetrital particles were found as a sand‐silt layer in a deep‐sea Messinian Stage (Upper Miocene) salt deposit in the Mediterranean Basin (Balearic Sea). These particles include worn and limonite‐coated quartz, feldspar, glauconite, volcanic glass, reworked Messinian foraminifera and some lutecites. The lutecites are not original to the salt and taken in their association with the other detritus, especially the foraminifera, suggest syndepositional reworking of exposed Messinian evapo

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02063.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The Mechanics of Erosion.By M. A. Carson.Estuaries: A Physical Introduction.By Keith R. Dyer.‘Meteor’Forschungsergebnisse, Reihe CNos. 9 and 10. Edited by E. Seibold and H. Cl

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1974.tb02064.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY