Showing papers in "Journal of Sedimentary Research in 1971"
TL;DR: In this paper, the settling velocities in water of 216 glass spheres ranging in size from 50mu to 5000mu in diameter were determined and an empirical equation was derived to give the relationship between sphere size and settling velocity.
Abstract: The settling velocities in water of 216 glass spheres ranging in size from 50mu to 5000mu in diameter were determined. The size, density, and shape of these spheres were accurately known. All timing precisions were better than 1/2% and the combined precision (size, shape, density, timing, etc.) of the velocity measurements was less than 2% at a 95% confidence level. Based on this data an empirical equation was derived to give the relationship between sphere size and settling velocity. The range of usefulness of the equation includes from 0.1mu to 6 mm. diameter spheres and, with correction factors, is extended to 50 mm. diameter spheres. Practical tables are presented for various sphere diameters, water temperatures, sphere densities, and fluid salinities. The equation and sphere data are proposed for use as a basis of standardization of settling tube data and as a basis for determining the sedimentation diameter.
490 citations
TL;DR: In a high-energy coastal environment where long-period swell enters a nearshore uncomplicated by offshore bars, sedimentary structures develop on the seafloor in facies that trend parallel to the zones of different wave activity as mentioned in this paper.
Abstract: The marginal marine environment consists of an offshore where the wave form is approximately sinusoidal and a nearshore where the wave form is either solitary or that of a bore. Within the nearshore, shoaling waves become progressively higher and steeper until they break. After breaking, the waves progress as bores through a surf zone; these bores ultimately terminate within a swash zone on the beach itself. In a high-energy coastal environment where long-period swell enters a nearshore uncomplicated by offshore bars, sedimentary structures develop on the seafloor in facies that trend parallel to the zones of different wave activity. In the offshore, small sand ripples are the most common depositional structure, but in the nearshore larger bed forms predominate. Seaward from the line of breakers, in the zone of wave build-up, are landward-oriented lunate megaripples. Near the outer portion of the surf zone the bed form is planar (outer planar facies), but, in the inner portion of the zone, a area of large-scale bed roughness (inner rough facies) commonly is present. Within the swash zone, the bed form is again planar (inner planar facies). The boundaries of the facies shift in response to changes in waves or tide, and certain of the zones are sometimes missing. The relative position of the zones, however, is invariable. The major features of the bed forms can be interpreted in terms of flow regime. The stronger of the two opposing transient currents caused by passing waves produces structures analogous to those produced by continuous, unidirectional currents. Landward wave surge is dominant in the outer three structural facies, whereas seaward surge predominates in the innermost (inner planar) facies. Wave surge over the intermediate inner rough facies is more complex, and the direction of strongest surge may be variable. In the outer three facies, the landward sequence from small asymmetric ripples to lunate megaripples to plane bed suggests an increase in flow regime from the lower part of the lower regime to the upper regime; this shoreward increase in flow regime is associated with a shoreward increase in orbital velocity at the bottom. The inner planar facies is produced by flow in the upper regime. The inner rough facies, situated between two zones of flow in the upper regime, is apparently a product of flow in the upper part of the lower regime. Within each of the structural facies a distinctive set of internal structures is produced. Internal structure of the asymmetric ripple facies consists of shoreward-inclined ripple cross-lamination and gently inclined cross-stratification. The lunate megaripples produce medium-scale landward-dipping foresets. Within the outer planar facies bedding is nearly horizontal. Structures in the inner rough facies produce medium-scale foresets that mostly dip directly or obliquely seaward, although landward-dipping foresets also occur. Within the inner planar facies bedding is gently inclined seaward. Migration of the facies in response to changes in waves or tide produces distinctive assemblages of structures where the facies overlap. These assemblages provide criteria for paleoenvironmental i terpretation, particularly where interrelated assemblages occur in a meaningful spatial distribution.
409 citations
TL;DR: Debris flows, observed during movement and emplacement, deposit debris which is poorly sorted, has an unsupported framework, may contain elongate fragments which are roughly aligned parallel to bedding, and may show inverse grading as discussed by the authors.
Abstract: Field, laboratory, and theoretical investigations of fluids with very high concentrations of solid particles in water (up to 90%) show that they exhibit the property of strength, have high apparent viscosities which vary with velocity, have high bulk densities, and flow in laminar fashion or with greatly reduced turbulence. Debris flows, observed during movement and emplacement, deposit debris which is poorly sorted, has an unsupported framework, may contain elongate fragments which are roughly aligned parallel to bedding, and may show inverse grading. On low slopes, debris flow deposits commonly overlie easily eroded materials with little or no features of erosion. Subaqueous deposits in the geologic record which show these or somewhat similar features were probably emplaced as highl concentrated dispersions.
263 citations
TL;DR: In this article, it was shown that length-slow chalcedony, having its c-axis parallel to the fibers, is unusual in nature and occurs almost exclusively in association with sulphates and evaporites.
Abstract: Length-slow chalcedony, having its c-axis parallel to the fibers, is unusual in nature. Occurrences so far investigated reveal that this rare type of optically fibrous silica occurs almost exclusively in association with sulphates and evaporites. Often the evaporite minerals have been totally removed, and thus the survival of resistant length-slow chalcedony reveals the presence of former salt-flat, sabkha or sulphate-rich environments where none were before suspected. This type of chalcedony also in some instances forms in semi-arid, alkaline soils. Discovery of this simple criterion has led to development of an additional series of characteristics for identification of silicified evaporites. All siliceous deposits should be re-examined for presence of this important genetic m rker.
240 citations
TL;DR: In this article, the proportions of clay, silt and sand are used to define four major groups: claystone (clay), siltstone (silt), mudstone (mud) and sandstone (sand).
Abstract: Classifications of fine-grained sediments and sedimentary rocks are based on combinations of several criteria. These include: (1) texture, (2) fissility, (3) tectonic association or environment of deposition, (4) mineral composition, (5) color, (6) chemical composition and (7) degree of metamorphism. None of the classifications are generally used, however. For field studies, texture is the most significant property. The proportions of clay, silt and sand are used herein to define four major groups: claystone (clay), siltstone (silt), mudstone (mud) and sandstone (sand). Claystone, siltstone and sandstone are rocks containing more than 50 percent of clay-, silt- or sand-sized material, respectively. Mudstone contains less than 50 percent of clay, slit or sand. Silty and sandy are useful modifiers of claystone when clay-sized material is less than 75 percent but more than 50 percent. Clayey and sandy are used to modify siltstone when silt-sized material is less than 75 percent but more than 50 percent. The expression good sorting is applied to fine-grained clastic rocks that contain more than 90 percent silt or clay-sized material. Fair-sorted rocks contain 75 to 90 percent silt or clay. Poorly sorted siltstone or claystone contains less than 75 percent silt or clay. If fissile, fine-grained clastic rocks are so designated. The mineral composition of most fine-grained clastic rocks can be determined reliably with the petrographic microscope and by X-ray diffraction. Therefore, where possible, they should also be named according to one of the sandstone classifications and on the dominant clay mineral present. Color, bedding types and sedimentary structures, fossil content, type of cement and fissility should be included in complete descriptions. An example of a good field and laboratory description is: clayey siltstone, illite-subarkose, poor sorting, grayish red (5R4/2), dolomite cement, slabby, horizontal lamination, pelecypods.
147 citations
TL;DR: The shape of the head of a turbidity current is consistent with an inflow of the ambient medium into the current along clefts and tunnels regularly spaced along and back from the overhanging front of the turbidity head as discussed by the authors.
Abstract: The shape of the head of a turbidity current is consistent with an inflow of the ambient medium into the current along clefts and tunnels regularly spaced along and back from the overhanging front of the head. The rate of inflow of the ambient medium into the head is expressed mathematically, and it is shown that the bed shear stresses exerted in the region of the head vary transversely across the region with a spatial periodicity. The deducd force structure of the head region explains the hitherto puzzling occurrence on turbidite soles of regular bands or clusters of flute marks aligned parallel with flow. It is also shown that the near-bed flow in the head is strongly three-dimensional, and this may help to explain the commonly observed non-parallelism of the sole markings observed n single bedding surfaces. The rates of inflow of the ambient medium into the head are found to be large enough to account for the density reduction necessary for the transformation of a liquified sediment slump into a turbidity current in a journey down the continental slope and upper rise.
97 citations
TL;DR: In this paper, the authors use depth and mean velocity to characterize bed configurations in uniform open-channel flow over a loose sediment bed, leading to a three-dimensional diagram, with dimensionless measures of depth, mean velocity, and sediment size as coordinates, with the property of one-to-one correspondence between possible bed configurations and points in the diagram.
Abstract: Use of depth and mean velocity to characterize bed configurations in uniform open-channel flow over a loose sediment bed leads to a three-dimensional diagram, with dimensionless measures of depth, mean velocity, and sediment size (or these three variables themselves) as coordinates, with the property of one-to-one correspondence between possible bed configurations and points in the diagram, thus eliminating overlapping of fields in diagrams involving bed shear stress. The diagram is most readily visualized by means of depth-velocity sections for a series of sediment sizes. Depth-velocity diagrams plotted from U. S. Geological Survey flume data for five sediment sizes ranging from fine sand to very coarse sand show contiguous but nonoverlapping fields for ripples, dunes, transition, and flat bed (is the finer sands) and lower flat bed, dunes, transition, and upper flat bed (in the coarser sands), with increasing mean velocity; field boundaries are almost parallel to the depth axis or slightly inclined. Each of these fields is truncated by a field for standing waves and antidunes at smaller depth or higher velocity. A size-velocity section for a depth of 0.2 m constructed from the depth-velocity sections shows more clearly the relations among the bed-configuration fields with varying sediment size. Several lines of evidence indicate that the dune field, which lies between the fields for ripples and flat bed in the fine to medium sand range, wedges out with decreasing sediment size at about 0.08 mm; in finer sediments, ripples pass directly into a flat bed. The relations between the ripple field for finer sands and the lower flat-bed field for coarser sands is unclear. If the densities of fluid and sediment are varied, then there is a different depth-velocity-size diagram for each ratio of sediment density to fluid density. The wide gap in density ratio between the cases of sand in water and sand in air on Earth might be bridged by experiments at intermediate density ratios.
88 citations
TL;DR: In this article, the carbonate components of relict continental margin sediments off North and South Carolina show abundant evidence of microborings related to endolithic fungi and algae, and the relative abundance of carbonates in Carolina shelf sediments is not only related to skeletal productivity and degree of dilution by clastics, but also to the degree of organic erosion to which sediments have been subjected.
Abstract: Carbonate components of relict continental margin sediments off North and South Carolina show abundant evidence of microborings related to endolithic fungi and algae. Microborings were observed in bottom sediments collected from 165 sites ranging in depth from the intertidal to 780 meters. Forty-two of these samples were fixed in buffered formaldehyde to preserve endolithic organisms which were subsequently isolated for study through decalcification of skeletal substrates. Plastic impregnated thin sections and etched slabs, the latter revealing three dimensional models of boring networks, were also used to distinguish three main types of microborings: a) fungi, 1-4 microns in diameter, b) a septate green alga, 10 microns in diameter, and c) a diagnostic siphonaceous green alga, 15-20 icrons in diameter. Of these endolithic plants, fungi were the most abundant as well as most widespread. A distinctive, siphonaceous green alga defined three linear bands of highly bored sediments believed to reflect nearshore zones of high algal boring activity. The innermost zone, extending from the present day intertidal to depths of approximately 25 meters, is considered to be presently active; the outer two zones on the shelf are interpreted as marking relict shoreline positions associated with lower sea level stands. In situ organic erosion by microboring organisms is believed to be an important source of carbonate fines in Carolina shelf sediments. Molluscan components are being selectively attacked and removed from the carbonate fraction through the activity of endolithic fungi and algae. The relative abundance of carbonates in Carolina shelf sediments is therefore believed to be not only related to skeletal productivity and degree of dilution by clastics, but also to the degree of organic erosion to which sediments have been subjected.
75 citations
TL;DR: In this article, the effect of compaction and differential compaction on coal is analyzed using a graph of porosity versus depth of burial, which is a composite of published data on compaction tests, drill cores, and cores of unlithified clayey sediments.
Abstract: Analyzing the effects of compaction and differential compaction can give "wholesale returns of conjecture. One kind of analysis depends on calculating a "decompaction number" which, when multiplied by present thickness of a compacted interval, will yield the original thickness. The simplest parameter for this is grain proportion (complement of porosity, or dry bulk density divided by solid grain density), because thickness times grain proportion remains constant during compaction of a bed. The decompaction number for clayey sediments is the present grain proportion divided by earlier or initial grain proportion. Initial grain proportion averages 0.22 (78 percent porosity), and solid grain density averages 2.66 gm/cc. Other kinds of analysis are aided by a graph of porosity versus depth of burial. The graph is a composite of published data on compaction tests, drill cores, and cores of unlithified clayey sediments. Differential compaction lends itself to empirical analysis, especially where compacted coat or shale inter-tongues with noncompacted sand. Tentative decompaction numbers for coal are cited from unpublished data. Several conjectures are drawn from compaction features in southwest Vermont, involving Cambro-Ordovician argillites and distal sandy interbeds of an inferred submarine fan. Shallow scouring is revealed by restoring initial geometry. The decompaction number argues against tectonic thinning. Porosity of the argillites was perhaps 30 percent during gravity sliding of this slice of the Taconic klippe, was reduced by tectonic overburden, and was eliminated by mild Acadian metamorphism.
69 citations
67 citations
TL;DR: In this article, the polyframboidal texture of pyrite is defined and dispersed and concentrated occurrences in graywackes are described and explained as being, respectively, of early diagenetic, authigenic origin and the product of seafloor working of turbidite sediments already containing such pyrites.
Abstract: The polyframboidal texture of pyrite is defined. Dispersed and concentrated occurrences in graywackes are described and explained as being, respectively, of early diagenetic, authigenic origin and the product of seafloor working of turbidite sediments already containing such pyrite.
TL;DR: Analyses of 355 surface sediment samples (top cm) from lakes Ontario, Erie and Huron were carried out for organic carbon, carbonate carbon, Eh, pH, nitrogen and sediment texture as mentioned in this paper.
Abstract: Analyses of 355 surface sediment samples (top cm) from Lakes Ontario, Erie and Huron were carried out for organic carbon, carbonate carbon, Eh, pH, nitrogen and sediment texture. Similar analyses were carried out on a representative core from each lake at close intervals down to 20 cm. The distribution of organic matter in the sediments of each lake was related to the topographic features of the lakes. Organic carbon content was found to be directly proportional to the clay content of the sediment, ranging from less than 1 percent in the coarse nearshore sands to over 4 percent in the fine clay muds within the individual lake sub-basins. The organic carbon content of Lake Erie sediments was generally lower than that of Lakes Huron and Ontario, and is attributed to dilution of the sedi ents with coarser non-clay particles. Nitrogen was directly proportional to organic carbon with carbon-nitrogen ratios ranging from 7 to 13 in the surface sediment. Organic carbon and nitrogen decreased sharply from the surface down to about 10 cm in each core. The decrease is due partly to mineralization of organic matter by bottom organisms and partly to an increasing input of organic matter to the lakes in the last 30 years.
TL;DR: A wave effectiveness parameter defined as the product of theoretical instantaneous sediment transport rate times frequency is given for wave action at the sea bed as mentioned in this paper, where high values of this parameter are found in waters shallower than 18 m.
Abstract: A wave effectiveness parameter defined as the product of theoretical instantaneous sediment transport rate times frequency is given for wave action at the sea bed. High values of this parameter are found in waters shallower than 18 m. (10 fm.) in the southern North Sea and are held to be responsible for absence of sand waves at these depths. On the other hand, mud deposition does occur in certain shallow areas of the southern North Sea where the concentration of suspended sediment is high. Farther offshore, where suspended sediment concentration is low and wave activity moderate (as defined by the effectiveness parameter), no mud deposits are found. With increasing depth to a low wave effectiveness region, more mud is found in the bottom sediment below 30 m. (16 fm.). In the Celtic Se the wave effectiveness parameter has the same value at 73 m. (40 fm.) as it does in the North Sea at 30 m. (16 fm.). This is close to the sand/mud boundary in the bottom sediments of both areas. Wave activity is only one factor--others being suspended sediment concentration and current velocity--influencing deposition of mud. Some ancient mudstone could have been deposited in shallow waters off exposed coasts.
TL;DR: In this article, the carbonate cements in a specimen from the living cup-shaped algal reefs of Bermuda were studied with scanning electron and light microscopes, showing that the micrite cement crystallizes directly within voids and is not the recrystallization product of earlier carbonate cement.
Abstract: The carbonate cements in a specimen from the living cup-shaped algal reefs of Bermuda were studied with scanning electron and light microscopes. These small cup reefs positioned on the margins of the platform are built by encrusting organisms; principally coralline algae, secondaril hydrocorals, gastropods and worm tubes; tire cavities of this framework are partly to completely filled with internal sediment. The principal cement is a mosaic of anhedral high-magnesium calcite, 15 tool % MgCO3 that lines and fills pores of skeletons, borings, and interstices of internal sediments. The size frequency maxima of the crystals is 2-4µ, the range of micrite. The other much less common cement is fibrous aragonite whose preferred habitat is as linings and fillings of gastropod shells. The SEM micrographs show that the micrite cement crystallizes directly within voids and is not the recrystallization product of earlier carbonate cement. The micrographs also show all stages from initial linings to complete fillings of voids as well as multiple generations of micrite. The crystallization of micrite within voids offers an alternative explanation to the accepted view that fossil micrites result from recrystallization. Because the cup reefs are extremely permeable and are located on the seaward margins of an oceanic platform where there is strong and continual wave surge, the cement must form from seawater of oceanic position. The predominance of repeated generations of micrite-sized crystals indicates that the mechanism and chemistry of precipitation must be studied within voids and on the scale of microns.
TL;DR: In this article, the authors subdivide the Lower Fine-grained Quartzite (Middle Dalradian) of Islay, Scotland into two facies, one consisting of massive-bedded, cross-stratified and rippled orthoquartzites and the other consisting of siltstone and mudstone.
Abstract: The Lower Fine-grained Quartzite (Middle Dalradian) of Islay, Scotland is subdivided into two facies. Facies 1 consists of massive-bedded, cross-stratified and rippled orthoquartzites. The basal portion is massive, planar bedded, with asymmetrical wavy surfaces on the tops of each bed. The middle and upper portions of Facies I are characterized by sharp-based and sharp-topped trough and planar sets of cross-stratification whose orientation is bimodal-hipolar. Upper sets of cross-stratification are rounded; some sets are drapped with mudstone beds. Both straight-crested and ladder ripples are common. Micro-cross-laminated sets are separated by wavy and bifurcated flaser bedding. Facies 2 consists of siltstone and mudstone, with accessory fine-grained orthoquartzite. Ubiquitous mudracks, isolated flat and thick lenticular bedding, tidal bedding and burrowing structures are common to this facies. The two facies are organized into a sharp-based, fining-upward sequence with Faces 1 at the base and Facies 2 at the top. The base of the sequence consists of a sharp contact overlain with massive sandstones (Interval A), which grades into cross-stratified sandstone (Interval B). Next above is a thin set of microcross-laminated orthoquartzite (Interval C) whose orientation is 90° or 180° to the underlying crossstratified set. Some of the cross-bedded and micro-cross-laminated orthoquartzites are draped with thin mudstone (Interval D). The top of the fining-upward sequence consists of Facies 2 mudstones and siltstones (Interval E). The depositional environments of both Facies 1 and 2 are interpreted to be tide-dominated. The sandstones of Facies 1 were deposited in both a tide-dominated shallow, sub-tidal and intertidal low tidal flat or low tidal sand bar environment, whereas Facies 2 siltstones and mudstones were deposited in a high tidal flat environment. The sharp-based, fining-upward sequences are regressive sequences consisting of basal shallow subtidal sandstones (interval A), intertidal sand flat or sand bar sandstones (Intervals B, C, D) and high tidal flat mudstones (Interval E). Comparison of the sedimentary features of the Lower Fine-grained Quartzite with sedimentary features from both Recent tidal areas of the North Sea and of the Minas Basin of the Bay of Fundy, and 45 documented intertidal and tide-dominated clastic sedimentary rocks, confirms the tidal origin of these beds. The depositional environments of many orthoquartzites may be similar to the tidal environments of the lower Fine-grained Quartzite.
TL;DR: The combined seasonal activities of both species result in an estimated 5.1 mm new layer of reworked sand in certain exposed areas of the braided lower Platte and Loup Rivers in eastern Nebraska as mentioned in this paper.
Abstract: Through their burrowing activities, the staphylinid beetles Bledius pallipennis and B. bellicosus\ remove significant quantities of loose, easily eroded sand from beneath cohesive surficial layers. The combined seasonal activities of both species result in an estimated 5.1 mm new layer of reworked sand in certain exposed areas of the braided lower Platte and Loup Rivers in eastern Nebraska.
TL;DR: A detailed petrographic examination of sand-sized stream sediment in Elk Creek reveals that most schist fragments are mechanically destroyed by less than 15 miles of transport (8 airline miles) in the high gradient portion of the stream as mentioned in this paper.
Abstract: Elk Creek is 120 stream miles (70 airline miles) in length and flows eastward from the northern Black Hills to join the Cheyenne River. The drainage basin encloses 601 sq. mi., of which 95.1 percent is underlain by Paleozoic and Mesozoic sedimentary rocks, 2.3 percent by Precambrian metamorphic rocks, and 1.8 percent by Tertiary felsitic siliceous hypabyssal rocks ("volcanics"). Cenozoic terrace gravels overlie approximately 25 percent of the sedimentary rocks. A detailed petrographic examination of sand sized stream sediment in Elk Creek reveals: (1) most schist fragments are mechanically destroyed by less than 15 miles of transport (8 airline miles) in the high gradient portion of the stream; (2) "volcanic" rock fragments are durable and there is no noticeable loss from mechanical abrasion during the initial 100 miles of transport; (3) rounding of "volcanic" rock fragments due to mechanical abrasion occurs only in sediment coarser than 1mm.
TL;DR: In this paper, a semi-empirical analysis was conducted to delimit the areas of wave refraction and the bottom orbital velocity variations in the Gironde estuary, and the textural parameter distribution patterns of the sands coincide with and reflect the different energy zones.
Abstract: The bottom sediments in the marine portion of the Gironde estuary have been extensively sampled and studied in relationship to the local wave and tidal current patterns. A semi-empirical analysis was conducted to delimit the areas of wave refraction and the bottom orbital velocity variations. Compilation of the current and wave energy data from on-site measurements show that distinct energy zones exists, each characterized by different current strength and type. These zones are controlled by the morphological features of the estuary, the tidal and wave energy zones being mutually exclusive. Most of the tidal current discharge occurs in the deeper channels, whereas the shoal areas are the site of important wave energy. Most of the sediments are sands (phi mean between 2.0 and 0.5). A large gravel deposit however was observed at the entrance of the estuary. The textural parameter distribution patterns of the sands coincide with and reflect the different energy zones. The distinct combination of energy type in a particular zone will cause a distinct textural pattern in the sediments found within it. Moreover, comparison of tim time-averaged tidal velocities with standard sediment erosion curves show that the grain size distribution of the sands seems to be in equilibrium with the hydraulic environment. The gravel deposit is inferred to be a fossil alluvial terrace because it does not seem to be in accord with the present-day current patterns. A marked functionality exists between the more significant parameters of size, sorting and skewness and the ratio of wave to tidal energy. This is particularly evident in parameter distribution maps. The mean grain size, sorting, and skewness of the sands are inversely proportional to the ratio of wave to tidal activity. The inferred transportational processes seem also to reflect the established energy zones. A CM curve analysis indicates a graded suspension transport mode for zones where wave energy predominates, and bedload transport for areas influenced by tidal currents. This effect seems to be corroborated by consideration of the orbital bottom wave velocity as a function of depth. The depth limit for the transportational processes due to wave activity seems to be about 15 meters. Beyond this depth, the sediment is transported mainly by the tidal currents. It is concluded that textural patterns are good indicators of energy variations, even in complex, multi-environmental areas such as estuaries. Future research will probably establish quantitative relationships between energy type and distribution and the resutling textural parameters.
TL;DR: In this article, chemical analyses of recent sediments from Banderas Bay, Mexico, show that the non-exchangeable Mg content of the clay fraction is higher, and the Fe content is lower, in strongly reducing environments than in similar sediment from less reducing environments.
Abstract: Chemical analyses of Recent sediments from Banderas Bay, Mexico, show that the non-exchangeable Mg content of the clay fraction is higher, and the Fe content is lower, in sediments from strongly reducing environments than in similar sediments from less reducing environments. Clay mineralogy (52% montmorillonite, 28% kaolinite, 20% illite) does not vary significantly among the different environments. The total cation-exchange capacity of the clays does not differ in the different environments although exchangeable Na is markedly lower in clays from the sulfide-rich sediments. A possible explanation for these effects is that in a strongly reducing environment, Fe leaves the montmorillonite structure to form a sulfide, and Mg enters the same sites from the surrounding water, so that gros clay mineralogy is unchanged. Mg is depleted in the interstitial water of the anoxic sediments and Mg must be diffusing into the sediment from the overlying sea-water to account for the increased Mg content of the clay. Analysis of clay minerals separated by continuous particle electrophoresis indicates that the "montmorillonite" contains approximately 1.2% K2O, and that the non-exchangeable Mg content of the montmorillonite in sediment from 1 m below the surface is 10% higher than in surface sediment. Alkali-soluble Al2O3 and SiO2 in the clay fraction of the sediments ("amorphous material") decreases with depth in the cores, but there is no evidence that this represents a reaction which removes cations from sea water. Apart from initial ion exchange and glauconite formation, there is no evidence for uptake of K or Na by land-derived clay minerals.
TL;DR: In this article, a cross-sectional model was constructed from surface exposures across the Upper Cretaceous Gallup shoreline in the Ship Rock area of northwestern New Mexico, showing lower Gallup regressive-beach sandstone overlain unconformably by upper Gallup transgressive offshore-bar sandstones.
Abstract: To provide an example of ancient deposits across a sand-beach shoreline for comparison with both Recent and other ancient deposits, a cross-sectional model was constructed from surface exposures across the Upper Cretaceous Gallup shoreline in the Ship Rock area of northwestern New Mexico. Tile model shows lower Gallup regressive-beach sandstone overlain unconformably by upper Gallup transgressive offshore-bar sandstones. Landward, the beach sandstone interfingers with coal-swamp deposits or is truncated and overlain by dune standstone. Seaward, the beach sandstone grades through shoreface sandstone into a transition that gives way to offshore siltstone and mudstone. Offshore siltstone and mudstone overlie and in part grade laterally into offshore-bar sandstone, which has no contiguous landward equivalents and transgresses all beach and related facies. Within their particular stratigraphic frameworks, sedimentary structures, supported by lithologic and paleontologic data, identify both the beach and the offshore-bar sandstones as well as their related facies. Both the beaches and the offshore bars consist of imbricate patterns of parallel beds. Beds in the backshore beach consist of cross laminae that dip either in diverse directions or landward and that compose laminasets, which are swale fillings; cross laminae in the foreshore beach dip uniformly seaward at low angles. Beds of shoreface sandstone are either churned by burrowing organisms or composed of large-scale truncated wave-ripple laminae. in the transition between shoreface and offshore siltstone and mudstone, beds of mudstone interfinger with bells of sandstone and siltstone, which show small-scale truncated wave-ripple laminae and churned structure. Siltstone and mudstone beds alternate in offshore rocks, and the siltstones contain both current-ripple and truncated wave-ripple laminae, except where burrowing organisms have destroyed the laminae. Most beds of offshore-bar sandstone are churned, but some show high-angle cross laminae that dip parallel with the length of the bar and approximately parallel with the distant shoreline. Burrowing organisms have completely churned the muddy sandstone beds of the offshore-bar transition.
TL;DR: In this article, a 12-inch bed comprised of horizontal laminae examined in a river bank is believed to have formed by accretion of low amplitude sand waves on a floodplain during slowly increasing flood stages.
Abstract: Thin sand sheets with downstream foresets form in very shallow depths in the Platte River and resemble small sand waves. They produce internal horizontal stratification which is superficially similar to upper flow regime plane bed deposits except that the grains are differentiated into alternating coarse and fine laminations by sorting processes at the foreset. A 12-inch bed comprised of horizontal laminae examined in a river bank is believed to have formed by accretion of low amplitude sand waves on a floodplain during slowly increasing flood stages.
TL;DR: The relationship between environment, fossil algae, and algal structures are not well understood, and the descriptive terminology is becoming more complicated as mentioned in this paper, but they have been examined from a paleoecologic viewpoint.
Abstract: For many years, algal limestone bodies have been known in the Point Peak and San Saba Members of the Wilberns Formation (Late Cambrian (Dresbachian) to Early Ordovician) in the Llano Uplift region of central Texas, but they have never been studied in detail. The relationships between environment, fossil algae, and algal structures are not well understood, and the descriptive terminology is becoming more complicated. The writer has examined algal macrostructures along with their corresponding microfabrics and fossil algae from a paleoecologic viewpoint. Several previously unknown microfabrics have been found that reflect the growth patterns of various algal taxa in response to different hydrologic conditions. For example, fossil algae with wispy or tufted growth forms are found in nonlaminated algal macrostructures (limited hydrologic stress) while laminated macrostructures such as stromatolites exhibit tightly laminated microfabrics (considerable hydrologic stress). The various environmentally produced structures are found commonly in sequences that depict the long-term paleoecologic history of the algal reefs from their inception (commonly in the sublittoral) to their culmination (commonly in the intertidal). Four different genera of fossil algae, Girvanella, Epiphyton, Renalcis and Nuia , were found in this study.
TL;DR: In this paper, three dolomite standards were selected from which 33 mixtures (11 each) of calcite and calcite were prepared in triplicate (99 total).
Abstract: The observation that X-ray methods currently in use for determination of calcite and dolomite in rocks and sediments often give inconsistent results led us to structure an experiment to evaluate their relative accuracy. Three dolomite standards were selected from which 33 mixtures (11 each) of calcite and dolomite were prepared in triplicate (99 total). The intensities of the major calcite and dolomite reflections of each slide were measured by four methods: by fixed-time count on the peak maximum, integral count of a fixed interval across the peak, ruler measurement of peak height and planimeter measurement of peak area. The parameter "dolomite/dolomite plus calcite" was computed for each diffraction pattern. A curve of best-fit and the standard error of this parameter, as a function of weight percent dolomite, were computed for various combinations of individual and average data to determine the relative accuracy of the several types of intensity measures. Results of previous investigators were compared with our data to estimate their relative precision. It is concluded that X-ray peak-height (fixed time) intensity measurement provides the most rapid and precise procedure for determination of calcite and dolomite. Composite data for all types of measurement yield a calibration curve which gives results in terms of weight percent dolomite of about ±6 at the 95% confidence level. Its true accuracy is probably better. Replicate analysis of unknowns yield mean values with standard deviations of about 3, expressed as percent dolomite. Most of the curves presented by prior investigators compare well with ours; that is, they lie within our documented confidence interval, and data derived from them can probably be considered reliable within the limits of accuracy established by this study.
TL;DR: In this article, it was shown that the Ferron river was about 300 feet wide and 25 feet deep, with meander lengths of 2,500 to 4,100 feet.
Abstract: Interpretation of sedimentary structures and detailed stratigraphic relations of the fluvial facies of the Upper Cretaceous Ferron Sandstone in the Castle Valley in east-central Utah permits reasonable reconstruction of many parameters of a Late Cretaceous alluvial system. After the width and depth of flow of the ancient Ferron river have been estimated from the geometry of preserved sedimentary structures, and the type of sediment transported by the river has been determined by study of the sandstone texture, various relationships of modern streams empirically derived by Schumm are used to estimate channel sinuosity, meander length, mean annual discharge, mean annual flood, channel slope, and flow velocity. Values derived for the slope and velocity are supported by other indirect met ods based on the Manning equation. It appears likely that the Late Cretaceous Ferron river was about 300 feet wide and 25 feet deep, and that it was highly sinuous, with meander lengths of 2,500 to 4,100 feet. As the 200-mile-long river drained an area to the southwest of 6,000 to 8,000 square miles, it had a mean annual discharge of approximately 6,000 to 7,000 cubic feet per second and a mean annual flood of about 22,000 cubic feet per second. Although only 2 percent of the total river load was bedload, the flow velocity of between 2.0 and 4.6 feet per second in the upper part of the lower flow regime caused the fine- to medium-grained sand to be in a dune bed configuration. Some caution is advised in using this approach because of unresolved questions of applying modern stream relations to pre-Quaternary deposits and because of uncertainties in determining the cross-sectional shape and sediment texture of the ancient Ferron river.
TL;DR: The dominant direction of littoral transport of sand-size sediments has been to the north at least during the past 18,000 years as discussed by the authors, and the observed dispersal patterns of heavy minerals may be indicative of more efficient Littoral processes during the last major sea level lowering.
Abstract: Heavy mineral analysis of the rivers of Oregon and northern California has been used to outline four major sources of sediments on the Oregon continental shelf. These sources include the Columbia River Basin, the Oregon Coast Range, the Klamath-Siskiyou Mountains, and terrace deposits along the central Oregon coast. Dispersal patterns of sand-size sediments show that the dominant direction of littoral transport has been to the north at least during the past 18,000 years. Sands were transported 170 miles to the north on the continental shelf during the end of the Late Wisconsin regression and the beginning of the Early Holocene transgression. The observed dispersal patterns of heavy minerals may be indicative of more efficient littoral processes during the last major sea level lowering Reduction of sand supply to the littoral zone and natural obstacles, such as erosionally resistant headlands, to the littoral transport of sand have apparently limited the northward transport of sand during the past 3,000 years.
TL;DR: In this article, experiments were conducted on Chesil Beach in 1969 and 1970 using natural beach material introduced onto Chesil beach from other areas. The 1969 trials used approximately 17,000 quartz granulites; 1970 trials used two batches of approximately 6000 quartzite-jasper conglomerates and one batch of over 5000 basalts.
Abstract: This paper discusses experiments undertaken in 1969 and 1970 using natural beach material introduced onto Chesil Beach from other areas. The 1969 trials used approximately 17,000 quartz granulites; 1970 trials used two batches of approximately 6000 quartzite-jasper conglomerates and one batch of over 5000 basalts. In 1969 one site was used; in 1970 two were chosen to provide comparisons. Trial searches showed variability in recovery rates reflecting both the nature of the introduced material and the effect of the size of the background pebbles. The experiments showed: i) Rates of movement for the quartz granulites at Wyke reached 343m per day but after 165 days the farthest travelled was only 3952m from its origin. This reflects both the proportion of time that material is out of circulation by being above or below the zone of wave action and transport opposite to the prevailing direction from time to time. The 1970 experiments showed different periods of burial for the two trial sites and less consistent direction of movement at Portland where wave approach is more nearly at rightangles to the shore. Data show that lateral movement of individual pebbles is not necessarily greater under storm conditions. ii) Recovery patterns indicate concentrations of experimental material at high and low water marks. There are also concentrations along the beach which may be related either to anomalies in beach curvature or to the time available for longshore movement. iii) Maximum recovery rates occur under long, low ground swell conditions. Under these circumstances, where the pebbles are larger than the natural background material they are 'rejected' from it and lie on the surface. As a consequence they are available for 'attack' by beach processes for a disproportionate length of time. Recovered material is not necessarily typical of that injected initially being differentially selected depending upon the particular wave conditions. The percentage of high specific gravity basalts recovered differs from that of other types of added material since the basalt pebbles work their way into the beach only to be exhumed at a later date. iv) There is a relationship between pebble size and longshore movement. Correlations have been found in both directions. Short diameter is most sensitive to changes in wave period and direction. v) Shape sorting and shape abrasion do not appear to play an important part on this beach. This is possibly the effect of the pebble traction carpet and the high wave energy at the site. vi) Size sorting is probably affected in the vertical plane by phase difference. Longshore sorting is most likely achieved by a vector imparted by the direction of wave approach. This vector is more effective at Wyke than at Portland, since it is more oblique to the coast and the traction carpet is composed of finer material.
TL;DR: The photo-extinction method of fine particle size analysis by hydrophotometer is significantly faster and more precise than pipette analysis as discussed by the authors, and can be performed by computer in fifteen minutes.
Abstract: The photo-extinction method of fine particle size analysis by hydrophotometer is significantly faster and more precise than pipette analysis. Six samples are analyzed per hour by the hydrophotometer and calculations can be performed by computer in fifteen minutes. Hydrophotometer reproducibility, expressed as the standard deviation of phi percentiles of the cumulative curve is 0.11 , whereas that of the pipette method is 0.45 . Precision of both methods increases, in the course of analysis, from silt to clay; and the ranges of precision, respectively, are 0.07-0.36 and 0.06-1.69 . Sample treatment for hydrophotometer analysis is non-destructive (no sample drying) and great versatility in the nature of the settling medium and dispersant is afforded.
TL;DR: The clay mineralogy of over ninety samples of Old Red Sandstone sedimentary and volcanic rocks from various parts of Scotland has been investigated by X-ray diffraction, differential thermal analysis, infrared spectroscopy and electron and optical microscopy as discussed by the authors.
Abstract: The clay mineralogy of over ninety samples of Old Red Sandstone sedimentary and volcanic rocks from various parts of Scotland has been investigated by X-ray diffraction, differential thermal analysis, infrared spectroscopy and electron and optical microscopy. The Downtonian stage of the Lower Old Red Sandstone is characterized by kaolinitic clays, mainly of detrital origin. Overlying Dittonian rocks contain little kaolinite and frequently yield a variety of interstratified minerals including chlorite-vermiculite, dioctahedral smectite-chlorite and illite-smectite, largely from fresh and altered volcanic debris. In the Middle Old Red Sandstone of Caithness the dominant clay minerals are illite and chlorite derived from erosion of micaceous and chloritic rocks in the source area. Sample from the Middle Old Red Sandstone of other areas, and from the Upper Old Red Sandstone, contain mainly kaolinite and interstratified illite-smectite often of diagenetic origin. Differential thermal analysis and electron microscopy show that there are two distinct types of illite-smectite. The first is characterized by normal temperatures of dehydroxylation (530-550°C.) and by an indeterminate platy morphology; the second dehydroxylates at abnormally high temperatures (670-680°C.) and occurs in slender, well-developed laths. The dominant iron oxide mineral is hematite, with minor goethite, and electron microscope observations indicate that both minerals, in part at least, crystallized after sediment deposition.
TL;DR: Isotopic analyses of 20 siderite spherulites, concretions and crystals from the continental Upper Cretaecous Whitemud and Edmonton Formations give C13 values between -2.7 and +12.8 per mil and O18 values between −14.9 and -7.0 per mil on the PDB scale as mentioned in this paper.
Abstract: Isotopic analyses of 20 siderite spherulites, concretions and crystals from the continental Upper Cretaecous Whitemud and Edmonton Formations giveC13 values between -2.7 and +12.8 per mil and O18 values between -14.9 and -7.0 per mil on the PDB scale. The carbon isotopic composition of these siderites is controlled by biogenic carbon dioxide produced during diagenesis and therefore is not indicative of the depositional environment of the sediments. The constant oxygen isotopic composition of well preserved siderites likely reflects the freshwater milieu of their formation. Partially oxidized siderites are depleted in O18 owing to secondary exchange reactions with "recent" percolating surface waters. Secondary changes of the carbon isotopic composition are less apparent because of the large spread of the primary C13 values.
TL;DR: In this paper, the authors measured 609 inclination angles and azimuth directions at seven sites on the coastal eolianites of Israel and found that about half of the cross-bedded Eolianite body is composed of steep avalanche bedded slipface laminae.
Abstract: Measurements of 609 inclination angles and azimuth directions at seven sites on the coastal eolianites of Israel indicate that about half of the crossbedded eolianite body is composed of steep avalanche bedded slipface laminae. About 10% are windward facing sets and the rest gentle leeward facing sets. The overall modal direction is in good agreement with the present, prevalently westerly and southwesterly wind regime. Shear stress differences seem responsible for the particle size sorting and lamination both on the rippled and slipface surfaces of the dunes. The proportion of steep avalanche bedded cosets seems to be a characteristic of the type of dune, decreasing in the order barchans > transverse ridges > seifs.