Hard Bed Research Articles

Monolithologic erosion of hard beds by temperate glaciers

AbstractThe old problem of erosion by temperate glaciers is reviewed. We restrict ourselves to a monolithologic erosion of hard beds where chemical weathering is almost negligible. Rock fracture, either subglacial or otherwise, may have occurred during a previous cold episode, allowing long-lasting quarrying by the temperate glacier, but, once all the loosened material had been dragged away, grooving becomes the main erosional process. The theory of locally stress-controlled temperatures leads to the idea that very small particles found in the bottom ice cannot reach the bed. Therefore, abrasion and polishing come from rock chips due to grooving or sand grains freed by suglacial chemical weathering. In the steady regime, clasts that are able to groove come from the surrounding rock walls. Most of them do not enter the bergschrund, but are embedded in a bottom layer, which melts progressively over several kilometres. After being in contact with the bed over some distance, they are sufficiently blunted to become unable to groove. This distance. λ, increases with the boulder size, and the largest ones are not yet worn out at the glacier terminus. The mechanics of grooving is roughly modelled to estimate, for any stone size, the grooved volume per unit time and the grooving distance λ. From these estimations, and the size distribution, the erosion rate without quarrying as a function of the distance from the head wall, is calculated. It goes through a maximum when all the debris-laden bottom layer has just melted, and thus an overdeepening might form in a steady way. However, two unknown parameters enter the theory the probability ∏ for a stone able to groove which is in contact with the bed to groove and the ratiokof the volume of grooved rock before the stone is worn out to the volume of the stone. Experiments that may allow us to determine them are indicated below.

Monolithologic erosion of hard beds by temperate glaciers

AbstractThe old problem of erosion by temperate glaciers is reviewed. We restrict ourselves to a monolithologic erosion of hard beds where chemical weathering is almost negligible. Rock fracture, either subglacial or otherwise, may have occurred during a previous cold episode, allowing long-lasting quarrying by the temperate glacier, but, once all the loosened material had been dragged away, grooving becomes the main erosional process. The theory of locally stress-controlled temperatures leads to the idea that very small particles found in the bottom ice cannot reach the bed. Therefore, abrasion and polishing come from rock chips due to grooving or sand grains freed by suglacial chemical weathering. In the steady regime, clasts that are able to groove come from the surrounding rock walls. Most of them do not enter the bergschrund, but are embedded in a bottom layer, which melts progressively over several kilometres. After being in contact with the bed over some distance, they are sufficiently blunted to become unable to groove. This distance. λ, increases with the boulder size, and the largest ones are not yet worn out at the glacier terminus. The mechanics of grooving is roughly modelled to estimate, for any stone size, the grooved volume per unit time and the grooving distance λ. From these estimations, and the size distribution, the erosion rate without quarrying as a function of the distance from the head wall, is calculated. It goes through a maximum when all the debris-laden bottom layer has just melted, and thus an overdeepening might form in a steady way. However, two unknown parameters enter the theory the probability ∏ for a stone able to groove which is in contact with the bed to groove and the ratio k of the volume of grooved rock before the stone is worn out to the volume of the stone. Experiments that may allow us to determine them are indicated below.

Internal melting and ice accretion at the bottom of temperate glaciers

AbstractTemperate glacier ice is neither dry nor impermeable, as the standard theory of glacier sliding assumes. This fact leads to the already published concept of locally stress-controlled temperatures. Why the temperature is determined by the highest principal pressure, why the microscopic stress equals more or less the macroscopic one, and why water may flow in the capillary network even when water lenses at grain boundaries are freezing is explained. The new concept is applied to ice sliding on a hard bed having a sine profile, without cavitation. First, the stress field for a Newtonian viscous material and a vanishing roughness are used; next, an improved one, that takes into account the non-linear viscosity of ice and the finite amplitude of the micro-relief. It appears that water migrates from the stoss sides of the bumps to the lee sides within a bottom layer of thicknesshw. Moreover, there is less ice melting at the sole on the former ones than ice accretion on the latter, a fact that yields a trend of ice accretion at the glacier sole. It is balanced by internal melting near the bed and water oozing at the interface from the soaked ice. Consequently, a thin layer of accreted regelation ice with a constant mean thicknesshishould exist at the interface. Modelling realistically mountain glaciers,hw∼ 20 cm andhi∼ 3.5 cm are found.

Internal melting and ice accretion at the bottom of temperate glaciers

AbstractTemperate glacier ice is neither dry nor impermeable, as the standard theory of glacier sliding assumes. This fact leads to the already published concept of locally stress-controlled temperatures. Why the temperature is determined by the highest principal pressure, why the microscopic stress equals more or less the macroscopic one, and why water may flow in the capillary network even when water lenses at grain boundaries are freezing is explained. The new concept is applied to ice sliding on a hard bed having a sine profile, without cavitation. First, the stress field for a Newtonian viscous material and a vanishing roughness are used; next, an improved one, that takes into account the non-linear viscosity of ice and the finite amplitude of the micro-relief. It appears that water migrates from the stoss sides of the bumps to the lee sides within a bottom layer of thickness hw. Moreover, there is less ice melting at the sole on the former ones than ice accretion on the latter, a fact that yields a trend of ice accretion at the glacier sole. It is balanced by internal melting near the bed and water oozing at the interface from the soaked ice. Consequently, a thin layer of accreted regelation ice with a constant mean thickness hi should exist at the interface. Modelling realistically mountain glaciers, hw ∼ 20 cm and hi ∼ 3.5 cm are found.

Subglacial hydraulic conditions and their possible impact upon subglacial bed formation

In reviewing hypotheses of subglacial bed formation it becomes apparent that a close relationship must exist between the development of these bedforms and subglacial hydraulic conditions. A speculative classification of subglacial temperate beds is presented. Subglacial beds are subdivided into “H”, “Q”, and “M” beds. “H” beds are typically hard beds in which Upper interface meltwater activity dominates. “M” beds are those in whichd soft mobile subglacial debris conditions prevail and in which advective pervasive f flow of saturated debris occurs. In “Q” beds both of the other bed types occur but are of a spatially and temporally transitory nature. Thus this latter bed type may be the most common beneath ice masses. It is under an “M”-bed state that many drumlin subglacial bedforms and associated forms are thought to develop. Discussion on the processes involved in mobile debris entrainment and the effect of changing rheological parameters are developed. It is argued that such bedform initiation occurs due to anisotropic rheological variations within the mobile debris setting up a “feedback effect”. Such conditions are thought to be found most likely at the Lower interface of a fast moving ice mass possibly typical of an ice stream. In using empirical analyses of mobile debris conditions a limited set of relationships between subglacial meltwater flux rates, basal ice velocity, debris porosity and bed width are established with reference to mobile debris thicknesses. Using this relationship, a set of possible parameter values that would allow bed formation to be achieved are presented. The impact of bed formation under these conditions upon possible sedimentological facies and deformation structures is postulated. The wider effect of “M”-bedd conditionsd on subglacial sedimentology is introduced and the need to investigate subglacial hydraulic and bed conditions under past glaciations from the evidence of their glacial sediments and landforms emphasised.

Carbonate slide deposits in the Middle Jurassic of Portugal

A Bajocian to Callovian carbonate sequence at Mareta Beach, Sagres, Portugal, contains slide deposits laid down on the southern continental slope of the Iberian Meseta. Translational slide deposits form nine discrete zones up to 6 m thick. Intercalated hard and soft beds in lobate slide masses were deformed into megascopic recumbent folds, isolated fold noses, and imbricate slabs, in a partially coherent to incoherent manner. A prominent lineation on planar and folded surfaces is due to microfold and microfault sets which formed while the beds were semi-consolidated. Bioturbated omission surfaces overlie some slide deposits suggesting that slides incorporated near-surface sediments and formed topographically high sea floor features. Early partial cementation of the hard beds may have contributed to sliding by increasing pore pressure. A rotational slide scar closely associated with the deformed zones and low-angle truncation surfaces beneath some zones suggest that rotational failure may have initiated the translational slides. A southerly paleoslope toward the Tethys Ocean is indicated by orientations of folds, bedding-plane lineations, and slide scars.

Depositional Environment of Limestones and Intercalated Marls, Arcola Interval (Campanian) of Mooreville Chalk, Upper Cretaceous, Central Alabama: ABSTRACT

The Upper Cretaceous Arcola interval (Campanian) of the Mooreville Chalk, central Alabama Gulf Coastal Plain consists of 5 to 7 thin limestone beds (rather than the 2 and 3 beds reported previously), with intervening marl units up to 1.5 m thick. The limestones are algal-calcispheric packstones, whereas the intercalated marls are composed primarily of clay, mica, quartz, and a pelagic microfauna that provides a significant carbonate component. The limestones are hard Thalassinoides-bearing beds up to 40 cm thick, which can be traced laterally into limestone rubble zones. The rubble zones contain blocks 10-18 cm across that show conchoidal fracturing. Evidence of comminution means the limestone beds formed well above storm wave base and supports the hypotheses that the limestones were cemented on the sea floor and owe their lateral continuity in part to syndepositional brecciation and scattering of debris. The contact between the overlying marl unit (OMU) and the limestone is sharp, whereas gradational contacts exist between the underlying marl unit (UMU) and each limestone bed. Analysis of bulk composition using x-ray diffraction and thermogravimetric analysis shows that the UMUs contain, on the average, 69.8% of calcite and 13.3% of quartz and mica. These numbers differ significantly from the OMUs,more » which average 50.3% of calcite and 23.9% of quartz and mica. The limestone beds average 86.9% of calcite and 9.3% of quartz and mica. The increase of quartz and mica and the decrease in percentage of calcite in the OMUs result from increased terrigenous influx. These increases may coincide with regressive pulses in sea level.« less

Bed design and its effect on chronic low back pain — A limited controlled trial

This study examines the effect of 4 different types of beds on chronic low back pain patients' symptoms and signs. The beds employed were an "orthopedic" hard bed with 720 reinforced coils and a built-in bed board, a softer 500 coil bed, a standard 10 in. thick waterbed, and a hybrid bed of foam and water. Subjectively the majority of patients preferred the hard bed and felt that their back pain improved to a greater extent after 2 weeks on the hard bed as compared to the other beds. The next largest group of patients to show improvement used the waterbed. Limitations in performing the straight leg raising test coincided with the subjective complaints. Significantly improved straight leg raising was observed after use of the hard bed or waterbed in 25% of the patients using those beds. No other objective signs were altered. The 500 coil bed and the hybrid bed proved of no benefit to any patient in this study group. This limited study indicates that hard beds should remain the first choice of patients with chronic low back pain. However, if relief is not obtained for these chronic pain patients, a trial on a waterbed may prove beneficial.

Relief of Back Pain

To the Editor.— How often have you heard from your patients or friends with a chronic back problem: No matter how firm a surface sleep on, at times it is impossible to find a comfortable position, or I wake up with a low back ache even if sleep on a hard surface or sleep with my hips and knees slightly flexed. was recently in such a condition myself and happened to be living in a house that uses hammocks as extra beds. One night, after everything else had failed, decided to try a hammock and, for the first time in weeks, slept comfortably and woke up free of low back ache. have continued to sleep in a hammock for six months now, and it continues to be more comfortable for my back than a hard bed. As a long-term sufferer, have read much

Urhobo Mats in Praise of Daughters

ust south of the bustling markets of Warri, in places more quickly reached by canoe than by the circuitous tarmac roads, are the Urhobo villages of the Udu and Ughievwen clans, known throughout midwestern Nigeria for their strong and beautifully patterned mats. There the women make a variety of mats that are used every day. Rough, undecorated ones become rugs or impromptu umbrellas, and softer, simply patterned mats transform hard beds into comfortable sleeping areas. But the finest examples, boldly patterned in red-orange, black and white, are used in ceremonies for girls as they become women (Figs. 2, 3). During this time of honor, when a young woman is known as opha, the ewhere opha, or mat for opha, decorates her bed chamber. Another less common, strikingly beautiful mat given the girl is the multicolored ere opha, also mat for opha but called the weaver's mat in this article (Fig. 4). This type is freely patterned in a virtuoso display of a mat-maker's talent. It seems fitting indeed that the most elegant mats made by Urhobo women honor girls as they take on the responsibilities of womanhood. All Urhobo mats are made with the same simple twining technique. First the warp fibers are cut to the desired length and laid out evenly. Then two weft threads are tied to the first warp fiber, one above it and the other below it. These two threads are twisted so the one that was above the warp passes below it while the one that was below it goes above (Fig. 1). The twisting is repeated across the warp. M. O. Otedoh, an Urhobo botanist, has authoritatively identified the plants used in Urhobo mats.1 He describes in detail how the men gather leaflets of the palm Raphia hookeri from surrounding forests, and how the women and girls peel the leaflets and lay the strips in the sun to dry before tinting them with imported dyes (Otedoh 1972:174-182). Raffia is prepared for twining by rolling it between thumb and forefinger until it is a tight, twinelike thread. Although today, prepared and dyed raffia can be purchased at the market, some mat-makers still prefer to buy plain raffia and dye it at home.

Charles Nicolle and Inapparent Infections

Charles Nicolle was born in Rouen, Normandy in 1866, where he later became a reluctant graduate in medicine. He did not find his true niche until he reached the age of 36, when he was appointed Director of the Pasteur Institute of Tunis. In that crowded city he quickly became acquainted with a great variety of infectious diseases, and in the Tunisian countryside—the Bled—he learnt about their origins. He was entranced by the African bush and its motley inhabitants; he became inured to the hard beds, the bugs, the fleas, the lice and the aerial ballet (as he called it) of flies, mosquitoes, Phlebotomus and Stomoxys.In such surroundings, Nicolle inevitably met the unexpected; he had little or no equipment and had continually to improvise. He practised tropical medicine in the raw. His experiences are vividly related in “L'expérimentation dans l'étude des maladies infectieuses.” It might be said that his work for 24 years in the country resulted in “La Nicollonisation de Tunisie!”

Clay mineralogy of Triassic sediments in southern Israel and Sinai

ABSTRACTThe clay mineral composition of Triassic sediments in the Negev and Sinai depends upon the environment of deposition. Kaolinite predominates in continental and epicontinental sediments. The mineralogical composition of the marine clays resembles that of corresponding samples from North Africa and Europe, which comprise various mixtures and interstratifications of illite, montmorillonite, vermiculite and chlorite. Evaporitic sediments are poor in clay minerals and those present are largely detrital.The results presented suggest that chlorite was formed diagenetically by prolonged percolation of seawater through pervious layers overlying impervious ones (hard beds).

EVALUATION OF THE WINDALIA SAND, BARROW ISLAND AN EMPIRICAL APPROACH

The Barrow Island oilfield derives 97 percent of its 46,000 barrels per day production from the Lower Cretaceous Windalia Sand. The lithology of the sand, which is 110' + 20' thick across the field, is very finegrained, glauconitic sandstone, shaly and silty in parts and varying from moderately unconsolidated to firm. Thin, hard beds of dolomitic and calcareous, sandstone occur throughout. The sand has high porosity and low permeability.The argillaceous and unconsolidated nature of the formation precludes the use of log interpretation methods based on standard parameters, and it was decided to develop an empirical log evaluation method. In order to calibrate the logs, sixteen of the early wells were fully cored and logged, and the data compared using the Holgate method, which allows two parameters to be correlated to determine their relationship. In the example which is the subjert of this paper, core porosity was correlated against both sonic transit time and bulk density and hence calibration of these log parameters was obtained.The best fit straight line relating porosity and sonic transit time has its origin at 76 microseconds per foot and extrapolates to 246 microseconds per foot at 100 percent porosity. The bulk density — porosity cross plot gives a grain density of 2.71 grams per cubic centimetre and fluid density of 1.16 grans/ cc. The deviations from the standard parameters of delta-t matrix = 56. delta-t fluid = 189, grain density = 1.65, fluid density = 1.0 are explained by the shaliness and lack of compaction of the formation. Using charts for the calculation of water saturation and porosity from induction conductivity and sonic transit time (or bulk density) at 2' intervals through the sand, backed up with traced SP and caliper curves, an evaluation plot of standard format is developed. Intervals of nett effective pay are then chosen.Other evaluation techniques used during the development of the Windalia Poo! include a modified movable oil plot, used in the water injection wells where a saturated saline drilling fluid was employed, and a Sonic-Neutron log comparison for the identification of suspected gas columns in the Windalia.440 wells have now been drilled at Barrow Island, and the empirical evaluation methods evolved have enabled the definition of beds of producible hydrocarbons in all cases.

The Pleistocene History of Some Rivers in Western Iceland

Little detailed work has been carried out so far on the profiles of Icelandic rivers, mainly because of lack of survey information. During the course of a geomorphological investigation in Western Iceland in the summer of 1961 an area which included parts of two rivers was surveyed in detail (Ashwell, 1964) and the results of this survey have interesting implications both for Icelandic Pleistocene history and for the study of worldwide marine levels. The surveyed area (Fig. 1) covers the boundary between the highland plateau of Central Iceland, which in this district forms a Pliocene erosion surface at 3-400 m above sea-level (Einarsson, 1958, pp. 19-20) and the coastal lowland of Western Iceland. Structurally it forms part of the Tertiary basalt province of Western Iceland, in which the beds of lava dip at about 5? to the SSE. Although the amount of dip is small, horizontal erosion surfaces show up well against it. The structure exerts an important control on the relief (Fig. 2) in that outstanding rock features can often be traced to the same hard beds of basalt, while the rivers have in some cases cut along the strike of the basalt beds where intercalations of tholeeite basalt or soft sandstone occur. Faulting may have been widespread since many landscape features run parallel to the strike of the basalts. One of these is important to this study, since it forms a cliff, about 40 m in height, between the highland valley of Flokadalur, running between the ridges of Kroppsmuli in the north and Varmalaekjarmuli in the south, and the coastal lowland. This cliff is referred to as the Brekkurl cliff. This type of threshold occurs in two of the other valleys running parallel to Flokadalur. It does not appear, however, that the valley of Fl6kadalur or most of the landscape features in

THE PRELIMINARY STUDIES ON THE BEACH ROCK OF THE NORTHERN PART OF AMAMI OSHIMA, SOUTH-WEST JAPAN

The author visited 81 beaches of Amami Oshima, one of the South-west Islands of Japan, in December 1962, and found beach rocks at 35 beaches. Their sites are shown in Fig. 1. Beach rocks are classified into 1) typical ones, dipping seaward at 5-7 degrees, showing microcuestas, 2) ones having level beds, 3) hard beds lying under the ground of villages, 4) white calcareous rocks covering the black old rocks, forming small patches but no beds, 5) beaches where only fragments of beach rock are seen. There seems to be no relation between the existence of the beach rock and the components of the beach material. There are five types of beaches in northern Oshima, A) small deltas facing the ocean, B) large deltas facing the ocean, C) small deltas facing the inner bay, D) large deltas facing the inner bay, E) plains lying at the foot of the Pleistocene terrace facing the ocean. Types A) -D) are submerged coasts while types E) are the uplifted. We can see the beach rock at each beach of type A, C and E. Beach rocks are no longer seen at the present beaches of type B and D. Perhaps they were embedded by delta deposits. The author should think type 3) may be the embedded beach rocks.

Potassium-Argon Dating at Olduvai Gorge

Potassium-Argon Dating at Olduvai Gorge

Recognition of Folds and Faults on Rock Surfaces beneath the Sea

INFORMATION about the folding and faulting of the rock layers beneath the sea can be obtained by geophysical techniques, used in conjunction with sampling; but it is not easy to give a precise position of the geological boundaries on the floor, and only large faults can be inferred. The required detail can be obtained, however, by means of a geologists' asdic, where there are rock floors which consist of alternations of hard and soft beds and the former, being resistant to erosion, stand proud as ridges. In the English Channel, the Purbeck, Portland, Kimmeridge, Corallian beds and the ancient rocks occurring as shoals to east and west of Eddystone give good results, while Tertiary, Chalk and New Red Sandstone beds are too homogeneous to be suitable.

The Army of Nicholas I: Its Role and Character

VOLTAIRE'S description of Prussia as a country that did not have an army, as the army had the country, to a considerable degree applies to the Russia of Nicholas I. The empire, with a population of some sixty to seventy millions, supported a force of over one million under arms. Probably no contemporary army could equal it in the magnificence of its great parades, the masses of resplendent cavalry, or the perfection of a complicated system of drill and maneuver. Furthermore, it added to the glory won in the stubborn defense against Napoleon's Grande Armee and its victorious march to Paris in I8I4 by gaining new laurels through victories over Persians, Turks, Poles, and insurgent Magyars. It was by virtue of its prestige and power that for nearly thirty years Nicholas could play the role of gendarme of Europe. There is no need to define the role of this army as an instrument of foreign policy, as it is well known. Its functions within Russia are less familiar. It was the favorite agency of the emperor, who always wore a uniform, slept on a hard camp bed, and surrounded himself with soldiers. Not only did he have an unprecedented number of aides, adjutants, and other military flunkies around him, he even staffed his ministries with generals of his suite. In the I840's military men held ten of the thirteen ministerial portfolios, and there is some reason to think that he would gladly have filled the ministries of justice, education, and foreign affairs with generals if he had had any capable of holding them.1 It should be said that many of these soldiers in ministerial armchairs were not field commanders, but rather court generals.2 Some, however, had smelled

Mississippian Succession in Mount Head Area, Alberta: ABSTRACT

The Mississippian rocks of Mount Head area in the Southern Foothills of Alberta are included in the standard formations of the Alberta Rocky Mountains, the Banff, Rundle, and Rocky Mountain formations. The succession differs in several respects from that of the type region at Banff, these variations being, in part, of economic interest. The Banff formation is Kinderhookian in age. The Rundle formation is raised to group status to include two formations, the Livingstone and Mount Head. The Livingstone formation, of Osagian age, is divided into two members, Pekisko and Turner Valley, and the latter member into the following groups of beds: Banner, Dark Lime, Lower Porous, Middle Hard, and Upper Porous beds. The Mount Head formation of Meramecian age contains the following members: Wileman, Baril, Salter, Loomis, Marston, and Carnarvon. The Rocky Mountain formation is divided into a lower or Etherington member, Chesterian in age, and an Upper member of Pennsylvanian or Permian age. The Mississippian succession throughout the Southern Foothills of Alberta resembles that of the Mount Head area. Its division into several formations and members permits detailed correlation and study of the lateral variations of the beds. End_of_Article - Last_Page 418------------

COMPOSITE REFLECTIONS

This paper discusses the development of a method of reflection seismic prospecting based on the use of the seismic PS phase—a disturbance which has traveled from the shot to the reflecting bed as a dilatational wave and from the reflecting bed to the earth’s free surface as a shear wave, where it is picked up by horizontal component geophones. The reflection occurs on the seismogram in the otherwise quiet region between the dilatational waves and the ground roll and thus is never obscured by the ground roll. The reflection is quite clear and capable of spot correlation from spread to spread. The use of the method in delineating the Homer and Cotton Valley structures, near Minden, Louisiana, is described in detail. The method appears to be applicable to regions where an unconsolidated subsurface extends downwards from the earth’s surface to a single hard bed serving as a reflector. Criteria for identifying the disturbance as a composite reflection are given and the advantages and limitations of the method are discussed.