Clayey Beds Research Articles

Behaviour of embedded model screw anchors in soft clays

In recent years helical anchors have been used extensively in the construction of transmission tower foundations, pipelines and braced excavations. This Paper describes an experimental programme carried out to show the behaviour of multiple helical anchors at different embedment ratios in soft marine clays. The number of helical plates, their diameters and spacings are varied. Pullout tests were conducted by anchors installed in a soft marine clayey bed prepared in test tanks and at embedment ratios of 0-10. The results indicate that the anchor capacity increases with embedment ratio. The uplift capacity at any embedment ratio is explained in terms of the contribution of cohesive resistance between the top and bottom helical plates, the bearing resistance of the top helical plate alone and the shaft adhesion above. Based on embedment ratio and observations during testing, the anchors are classified as shallow, transit and deep anchors. Formulations are suggested for estimating and calculating the capacities of helical anchors which agree well with the results of previous investigators. Depuis quelques années, les ancrages hélicoïdaux ont été largement utilisés dans la construction de fondations de tours de transmission, de conduites et d'excavations armées. L'article décrit le programme expérimental mis en oeuvre pour montrer le comportement d'ancrages hélicoïdaux, dans des argiles molles marines, pour différents encastrements. Le nombre des plaques hélicoïdales, leur diamètre et l'espacement entre plaques sont variables. Des essais d'arrachement ont été réalisés sur des ancrages mis en place dans des lits d'argile molle marine préparés dans des cuves expérimentales, et ce pour des valeurs d'encastrement variant de 0 à 10. Les résultats obtenus montrent que la charge admissible des ancrages augmente avec le rapport d'encastrement. La charge verticale pour différents rapports d'encastrement peut être expliquée par une contribution de la résistance de cohésion entre le sommet et la base des plaques hélicoïdales, par la résistance ultime au sommet de la plaque et par l'adhérence latérale au dessus de celle-ci. A partir des rapports d'encastrement et des observations faites au cours des essais, les ancrages ont été répartis en trois groupes: ancrages superficiels, intermédiaires et profonds. Des équations permettant d'estimer et de calculer la charge des ancrages hélicoïdaux sont proposées. Elles se révèlent être en bon accord les résultats trouvés par les autres chercheurs.

Composition and genesis of the clays associated with quartz sand deposits at Paganico (Grosseto, Central Italy)

The clays associated with quartz sands at Paganico (Grosseto, Central Italy) are interesting both for their genesis and their potential uses. The Paganico deposits, ranging in age from Pliocene to Quaternary, mostly consist of very pure quartz sands derived from the erosion of Verrucano metasandstones sedimented in small lacustrine basins. Locally a clayey facies, made up of a soapy and white clay, is associated with the coarser detrital facies. The clayey beds are 2–3 meters thick and of limited extent, but their components may be recovered in great quantities from setting ponds, where they accumulate as tailings of quartz sand washing processes. The clay consists of kaolinite (up to 30%) and illite (10–70%), with subordinate amounts of alunite (5–10%), the remaining being mostly quartz. The genesis of these clays is complex. All the Paganico quartz sand and clay deposits are detrital in origin, being formed by Verrucano debris sedimentation in lacustrine basins. In some cases the deposition has been followed by gley-forming-like processes, involving seeping of organic-rich waters inducing leaching and partial removal of iron. In these cases partially iron-depleted, mottled quartz sand bodies were formed. The associated clays, when present, have not been affected by noticeable modifications, being mostly illitic in composition. In other quarries evidences of hydrothermal actions are present; extensive silica precipitation close to observed or inferred faults, abundance of alunite, complete leaching of iron, presence of nearby stibine mineralizations point to a hydrothermal fluid action. Kaolinite and illite are major constituents of these clays. The presence of alunite hinders the use of clays in the ceramic industry.

Levels of Reservoir Heterogeneity in a Mississippi River Meander Belt Sand System: ABSTRACT

Six levels of heterogeneity are present in a Mississippi River meander belt sand system near Dorena, Missouri, and these levels can be applied to reservoir description models. On an oil-field scale, the meander belt (13 million acre-ft of which 9 million acre-ft is sand), with its multiple abandoned channels, is the first level of heterogeneity. Level 2, represented by meander loop sands (1.2 million acre-ft) and single abandoned clay-filled channels, is on a stacked reservoir scale. Individual point bars (70,000 acre-ft) with extensive mud sheets (single reservoir or pool scale) constitute level 3. Lobe sheet units (40 acre-ft) of single well scale contain numerous reactivation surfaces and isolated mud drapes and are the fourth level of heterogeneity. Bedding units (< 10 acre-ft) with impervious bedset boundaries, of flow unit or perforated interval scale, constitute level 5. The sixth level of heterogeneity, individual laminae with variations in textural properties (cubic inches), is associated with interparticle fluid flow. The distribution of permeability barriers and nature of bounding surfaces control vertical and lateral reservoir continuity at the various levels. Poor sorting within and between foreset lamina, as well as infiltrated clay (level 6), are responsible for reducing permeabilities 10-50%. Large planar foresets andmore » trough cross-beds (levels 4 and 5) have permeabilities ranging from 90 to 160 Darcys. Permeabilities measured in clayey sand, silt, and sandy silt beds from the levee, crevasse, and abandoned channel fill range from several millidarcys to 50 darcys, and interbedded clayey silt and clay constituting channel plugs, chute fills, and mud sheets (levels 1, 2, and 3) have essentially no permeability.« less

Fire Lake depression: a glacially eroded feature in southwestern Saskatchewan, Canada

Fire Lake depression, which is 9 km long, 5 km wide, and about 100 m deep, was formed by surface removal of about 40 m of drift, mainly till, and 60 m of Cretaceous sands, silts, and clays. The depression, which was formed during the last glaciation, was partly filled with hummocky glaciolacustrine sands and silts. The bedrock beneath the depression is slickensided, folded, brecciated, softened, and gouged, typical of structures formed by shear.The physical dimensions, stratigraphy, structure, and age (last glaciation) indicate that the Fire Lake depression was formed by glacial erosion. The folding, faulting, brecciation, gouge, and softening of the bedrock beneath the depression are indicative of shear and suggest glacial thrusting. The process of glacial thrusting was not verified, however, because the sediments excavated from the depression were not found. The fact that the base of the depression corresponds to the uppermost, most clayey bed (least shear resistance) suggests that the depression was formed during one episode of glacial erosion.

Organic Matter in the Paleogene West European Rift: Bresse and Valence Salt Basins (France): ABSTRACT

The Bresse and Valence basins are two adjacent segments of the West European rift. They contain thick Paleogene halite sequences including intercalated and interfingering siliciclastic material and carbonate and sulfate deposits. Source rock samples in this study were mainly taken from the depocenters because of maximum sampling coverage. Organic matter (OM) is generally immature and occurs primarily within intercalated nonhalitic beds. The Bresse basin seems to contain more OM in (1) the Intermediate Salt Formation (Priabonian), composed of alternating laminated carbonate and halite beds; (2) the upper part of the Upper Salt Formation (clayey carbonate beds; Rupelian), affected by synsedimentary halite solution; and (3) the solution breccia which immediate overlies the salt sequence. In the Valence basin, the organic-rich layers are concentrated in the Subsalt Formation (carbonate beds; Priabonian), and the upper part of the Lower Salt Formation (laminates; Rupelian). In both basins, type III organic matter is associated with terrigenous facies. Type I is abundant in the Valence basin (laminites), and type II seems to be more abundant in the Bresse basin. The amount of OM varies considerably, and we suppose it is higher toward the basin margins. From studies made in evaporite basins in other region, which aremore » also known to have significant amounts of organic matter, we find a similar range of organic composition. Such studies are of interest because of their petroleum potential and for understanding precise depositional environments and waste disposal problems (gas generation with local heat source).« less

Primary migration of hydrocarbons from clayey beds during tectonic inversions

Primary migration of hydrocarbons from clayey beds during tectonic inversions

On the response of a Coulomb‐damped poroelastic bed to water waves

Abstract The problem of forced vibration of a slightly inelastic porous bed by water waves is treated analytically on the basis of a linearized expression of the nonlinear damping term for the grain‐to‐grain friction in bed soils and the linear theory by Biot (1962a [Jour. Appl. Physics, 33:1482–1498]) on the elastic wave propagation in porous media. A dispersion relation of water waves is obtained as a function of wave frequency, water depth, permeability, Poisson's ratio, rigidity, and specific loss of bed soil. Three types of elastic waves are induced in a bed by water waves: a shear wave and a compressional wave in the skeletal frame of soil, and a compressional wave in the pore fluid. The compressional wave, due to the motion of the pore fluid relative to the skeletal frame of soil, is highly damped by the viscosity of pore fluid and only a short range effect near the boundaries of discontinuity, such as a sea‐seabed interface. The seabed response to water waves is characterized by the two Mach numbers, i.e., the ratio of water‐wave speed to shear‐wave speed in soil and the ratio of water‐wave speed to compressional‐wave speed in soil. Most of the water‐wave propagation problems fall into the subsonic flow condition, where elastic waves in the bed travel faster than water waves. For sandy beds, generally the speeds of compressional and shear waves are much higher than the phase velocity of the water wave. For this case, the solution of the Coulomb‐damped poroelastic bed response presented in this paper approaches the solution of the massless poroelastic bed response in Yamamoto et al. (1978 [Jour. Fluid Mech., 87(1): 193–206]). The damping of water waves due to internal grain‐to‐grain friction is equally or more significant than the damping due to percolation in sand beds. For clay beds, the speed of the shear wave in soil becomes low and comparable to the phase speed of the water wave. The bed motion for this case is considerably amplified due to the near‐resonance vibration of shear mode of bed vibration. The water wavelength on a clay bed is significantly shortened compared to the water wavelength over a rigid bed. The water wave damping due to internal grain‐to‐grain friction in soil becomes much larger compared to the water wave damping due to percolation in clay beds. Long water waves over a soft clayey bed attenuate within several wavelengths of travel distance.

Environment of Deposition and Reservoir Properties of Woodbine Sandstone at Kurten Field, Brazos County, Texas: ABSTRACT

combination of stratigraphic and diagenetic events has trapped oil in thin-bedded, clayey sandstones of the Upper Cretaceous Woodbine-Eagle Ford Formations. Five sandstone units occur in Kurten field and are designated from top to bottom as A through E. Foraminifera and nannofossils indicate these units to be late Turonian. The C and D units are elongate north to south, 4.5 mi (7.2 km) wide, over 10 mi (16 km) long, and 40 ft (12 m) thick. The B and E units are thinner and trend northeast to southwest. Grain size coarsens upward in the B, C, and D units, averaging 0.14 mm and ranging from 0.09 to 0.18 mm. Grain size fines upward in the E unit. The sandstone's average composition is 66% quartz, 1% feldspar, 2% rock fragments, and 28% matrix. Sedimenta y structures in the B, C, and D units grade upward from laminated and bioturbated siltstones to clean sandstones with flaser cross-beds. The E unit consists of repeated bedsets similar to cde turbidite divisions. Sedimentary structures and bioturbation indicate that the units are offshore bars which have been formed by a combination of river mouth bypassing, storm-surge turbidity flows, and longshore currents. The porosity is largely diagenetic and occurs in the clayey beds. It appears to have been formed by freshwater leaching along an erosional unconformity overlain by the Austin Chalk. Permeability becomes progressively poorer away from the unconformity and a permeability barrier ultimately forms a poorly defined updip limit for the field, making Kurten a combination diagenetic and stratigraphic trap. Relatively widespread occurrences of offshore bars suggest that similar traps may be fairly common in ancient shelf sediments. End_of_Article - Last_Page 1681------------

Caractéristiques minéralogiques et géotechniques de lits argileux expansifs à l'origine de glissements de terrain

Many landslides have occurred at slope cuts-embankments adjacent to the Amman-Na'ur-Dead Sea and Irbid-Jerash-Amman highways in Jordan, especially during the last four years that were characterized by exceptional raifall during winter. Clayey beds found in the foundations of the failing areas were responsible for the occurrence of these landslides.

On the clay minerals at the landslide occurred in Chichibu Formation

After the heavy rain the landslide occurred at the beside of local road near Kuroda village, Manba-cho, Tano-Gun, Gunma Prefecture in J apan on the middle of June, 1974.By the boring for geological survey and prospect working of this place, we recognized the nature of the test pieces of rocks and clay minerals.This area mainly consists of schalstein of paleozoic system as we called Chichibu formation including thin layers of slate and chert.Not only the test boring but also the observations on local tohography, it was considered that many landslides has been occurred from early times.We can fined the two kinds of clay minerals in the cracks and joints of altered strata. One of them (sample No.1002 and 1003) has the elements of fine minerals derived from country rocks and also ammounts of clay minerals (micaceous clay minerals and chlorite) and occured from the horizontal thin cracks and joints in the country rocks, not so long continued.The other (sample No.1001) comes from the more thick clayey beds of altered zone of schalestein strata, consists of chlorite, micaceous clay and little ammount of montmollironite.Especially we can recognized the random mixed-layers of mica-montmollironite minerals.The landslide of this place is considered by such clay minerals as random mixed-layer mica-montmollironite, montmollironite, mica clay minerals and chlorite filling up the pore of rock bed.

Investigation of the stability of a clayey foundation bed by means of screens

Investigation of the stability of a clayey foundation bed by means of screens

Geologic Factors Affecting Compaction of Deposits in a Land-Subsidence Area

In the west-central San Joaquin Valley, California, pumping of ground water has changed water levels, thereby increasing the stresses that tend to compact alluvium by as much as 50 percent and creating a large area of intense land subsidence. The estimated 1943–1960 specific unit compaction (compaction during a time period, per unit thickness, per unit applied-stress increase) of the deposits in a northern subarea is four times that of a southern subarea, which suggests marked differences in the compressibility of the deposits. A third of the compressibility difference is real and is due to less prior total applied stress in the northern than in the southern subarea. The other two-thirds of the compressibility difference is only apparent and is attributed to different water-expulsion rates in the clayey beds of different depositional environments. In the northern subarea, the deposits are mainly flood-plain sediments that contain extensive sand beds and thin clayey beds that are dewatered relatively quickly under increasing effective stress. In the southern subarea, the sediments are mainly alluvial-fan deposits that contain thick clayey sequences adjacent to lensing sandy beds. These deposits are de-watered more slowly than those in the northern subarea. Variations of mean lithology in the chief compacting zone could not be correlated with variations in the specific unit compaction of the deposits.

Colloidal Soap as Proposed Primary Migration Medium for Hydrocarbons

Aqueous solution of hydrocarbons appears necessary to explain primary migration of liquid hydrocarbons in argillaceous source beds. However, relatively high solubility within the depth ranges of origin and primary migration (5,000-10,000 ft or more) is necessary to account for the known crude oil reserves. Colloidal soap greatly enhances hydrocarbon solubility, but its role has been questioned for several reasons: (1) lack of observations of micelles in the sedimentary section; (2) requirement of many times more soap than hydrocarbons for hydrocarbon solubilization; (3) problem of explaining the fate of the large quantities of soap required; (4) adsorption of soap on host rocks in specific cases; (5) doubt that soap concentrations in fluids at depth are sufficiently high for micelle formation; (6) conclusion by some authors that the more acidic, potentially soap-forming bitumen remains in source beds; (7) the extremely small interstitial pore spaces of fine-grained sediments, which constitute a mechanical barrier to micellar migration; and (8) an electrical barrier to migration due to n gative charges on both the ionic micelles and clay minerals. It is concluded that (1) search for micelles in presumed source beds has not yet been attempted; (2) a potential source of large amounts of soap exists in source beds; (3) after entering the reservoir, soap could be transformed to intermediate- and high-molecular-weight hydrocarbons and the asphaltenes and resins of crude oil; (4) relatively high temperature and electrolytic character of source-bed fluids at depth should promote solubility of soap; (5) soap concentrations in source-bed fluid should be sufficiently high for micelle formation; and (6) patterns with depth of organic elements (C, H, N, S, O, etc.), hydrocarbons, and acidic bitumen are compatible with soap formation. The most perplexing problems are the extremely small pore spaces and the electrical barrier in clayey source beds. Pore sizes are so minute that even the small ionic micelles and large hydrocarbon molecules would encounter difficulty in migrating during late compaction. The semi-permeable membrane effect on electrolytic fluids during late compaction apparently is caused by negative charges on closely spaced clay-mineral grains. Hence pore-to-pore migration of the negatively charged ionic micelles would be resisted. Clay mineral transformations, accompanied or followed by microfracture formation, perhaps could overcome these barriers. This postulate needs further testing by experimental and subsurface investigations. The large amounts of bitumen generated from kerogen contain high percentages of acid-enriched asphaltenes and resins. Known depth patterns of increasing amounts of asphaltenes and resins in organic matter, coupled with decreasing O+N+S content, could reflect, in part, a transfer of acids to interstitial waters by saponification. The higher the soap concentration, the larger would be the hydrocarbon solubilization capacity of each mole of soap present. Moderately high temperatures and release of bound water from clays should increase true solution of hydrocarbons which further enhances soap micelle formation. Transformation with depth of montmorillonite to increasing proportions of illite in mixed-layer clays should release additional saponifiable organic matter. Experiments demonstrate an adequate degree of hydrocarbon solubilization in concentrated soap solutions. Increases in salinity to above normal marine values progressively enhance micelle generation and hydrocarbon solubilization. Variations from brackish to well above normal marine salinities apparently exist at depth in marine source bed section. The accompanying moderately high temperature would promote transformation of the organic component, desorption of organic matter and water for migration, and decrease in micellar size. Eh, pH, and cation content of fluids in the major hydrocarbon migration depth intervals should be suitable for soluble soap formation. The low Eh is related to fine-grained character, clay content, and amounts and types of organic matter. In downdip Gulf Coast areas of Louisiana, pH is about 8.0, or between 8.0 and 9.0, at depths of several thousand feet and more. Calcium and magnesium cation concentrations are quite low and pore waters are of the sodium bicarbonate type. After source-bed fluids enter a reservoir system, several mechanisms could be responsible for breaking the soap colloid and freeing hydrocarbons. The most probable mechanisms are dilution of soap, decrease in pH, and increase in alkali-earth cation concentrations. If micelles persist until the moving reservoir fluid reaches a trap, the predominant mechanisms, triggered by water leakage into the caprock, would be increase in salinity, increase in calcium-ion concentration, and decrease in pH. Future research should assess the simultaneous effects of temperature, pressure, salinity, and other factors on micelle formation, hydrocarbon solubilization, and primary migration. Modeling should simulate subsurface conditions as closely as possible.

Petrographie und feinstratigraphie des unteren muschelkalkes in südniedersachsen und nordhessen

Petrographie und feinstratigraphie des unteren muschelkalkes in südniedersachsen und nordhessen

Characterization and Genetic Study of a Dennis and a Parsons Soil

AbstractThe Dennis series is comprised of deep, well‐drained Prairie soils developed in slightly acid to neutral, silty, and clayey shales of the Pennsylvanian Age. Dennis develops in materials of intermediate texture on gently sloping, erosional uplands, whereas Parsons, a Prairie Planosol, develops in more clayey beds on gentle slopes and flats. They occur naturally associated and extensively in Oklahoma, Kansas, and Missouri.A modal profile of each series was sampled in detail. Morphological, chemical, physical, and clay mineralogical studies were made on each subhorizon. The clay was separated into two fractions: 2 to 0.1µ (coarse clay) and &lt; 0.1µ (fine clay). Analyses were made for ethylene glycol retention, nonexchangeable K, cation exchange capacity, differential thermal, and X‐ray diffraction. Computations were made for clay mineral composition.Results show several times as much fine clay as coarse clay. In the Dennis the maximum clay accumulation occurs from 26 to 31 inches and in the Parsons from 22 to 28 inches. In the Dennis, coarse clay gradually decreases with horizonation and weathering, whereas in Parsons, it accumulates. Montmorillonitic‐type minerals dominate the fine clays of both profiles while kaolinitic and illitic types are dominant in the coarse clays.

Origin and Weathering of Late Pleistocene Ash Deposits on St. Vincent, B.W.I

The island of St. Vincent consists of an active volcano and the remains of two or more that are extinct. Late Pleistocene subaerial ash deposits forming the uppermost geologic unit over much of the island are the object of the present study. Most of the deposits are between 20 and 40 feet thick, but they reach a maximum thickness of at least 120 feet. They consist of andesitic lithic, crystal, and vitric material or their weathered equivalents. Plagioclase ($$An_{50-100}$$), hypersthene, augite, and olivine are the most abundant minerals. The ash was erupted from the Soufrière. The pattern of grain size and thickness suggests that it was distributed by northwesterly Pleistocene winds quite different from those of the present. Four lithologic fades have been separated on the basis of sorting, grain size, and degree of weathering-namely, the Soufrièreslope, eastern-coastal, western-coastal, and upland facies. Differences between them can be explained by primary distribution of the ash and subsequent removal of the fine material on steeper slopes by sheet wash. The facies of ash therefore reflects the topography of the underlying land surface. Soils developed and were buried while the ash accumulated to form a sequence of fossil soils. The vitric material and much of the plagioclase in the ash have been weathered to halloysite$$\cdot 4H_{2}O$$, and much olivine has been weathered to iddingsite. All the pyroxene and many of the olivine and plagioclase crystals have been etched by solution. Fine vitric ash was altered first, then plagioclase of composition ($$An_{80-100}$$). Olivine of composition $$(Fo_{74})$$ was the first ferromagnesian mineral to alter and was followed by more magnesian olivine ($$Fo_{78-85}$$), hypersthene, and augite, all of which were destroyed at about the same rate. Hornblende weathered more slowly. Plagioclase phenocrysts in pumiceous fragments altered more rapidly than did discrete crystals of the same composition. Minerals are more etched and otherwise altered in poorly drained clayey beds than in permeable beds, probably because the poorly drained beds provide a moist soil environment. Initial permeability differences in newly deposited ash seem adequate to account for differences in the degree to which the vitric ash has been altered to clay.

Basal Claiborne of Texas, Record of Appalachian Tectonism During Eocene

The Carrizo formation and the superjacent Newby member of the Reklaw formation (Eocene, Claiborne group) are lithologically similar sandstone units which crop out in Bastrop County, central Texas. The basal Carrizo is a strongly cross-bedded, poorly to moderately sorted, granular medium sandstone; it grades upward into moderately to well sorted fine sandstone, very fine sandy siltstone, and silty carbonaceous shale. The average lower Newby sample is a moderately to well sorted fine sandstone, and the middle Newby section includes clayey siltstone and carbonaceous shale beds which grade upward into cross-bedded, glauconitic sandstone lenticularly laminated with chocolate shale. Both Carrizo and Newby units are texturally submature to mature chert-bearing subgraywackes containing 65-75 per cent quartz, 5-10 per cent potash feldspar, 5-25 per cent phyllite, slate and metaquartzite fragments, and 5-10 per cent chert; there is little or no clay or silt matrix. The non-opaque heavy-mineral fraction consists of subangular kyanite and staurolite, angular and rounded zircon and tourmaline, and smaller amounts of garnet and rutile. Glauconite and authigenic feldspar are common in the upper, more marine part of the section. Most of the Carrizo and Newby detritus in Texas was originally derived from erosion of parts of the Ouachita foldbelt and particularly from uplift of the southern Appalachian Mountains--not from the Laramide orogenic belt as has been previously supposed. Sources north and west contributed reworked sedimentary material, but volcanic quartz and some feldspar were probably transported to the area of Bastrop County from a local source on the south. In Texas the Carrizo formation rests disconformably on the Wilcox (Eocene), and is placed in the Claiborne group. On the Sabine uplift and eastward, the Carrizo reportedly lies conformably on the Wilcox, and is considered the uppermost formation of the Wilcox group. This apparently local disconformity was probably produced by uplift and erosion of an uppermost Wilcox beach sand in south and central Texas. Erosion of this beach produced the subangular, highly polished grains which were reworked to form a large part of the Carrizo and Newby sandstones in Bastrop County. The region of maximum uplift may exist as a subsurface Wilcox high between Bastrop County and the Rio Grande embayment. On the basis of this study, augmented by petrographic examination of scattered samples throughout the rest of Texas Eocene sediments, a large-scale uplift of the southern Appalachian area is believed to have begun during the Midway or Sabine age and culminated during deposition of the great volume of upper Wilcox and lower Claiborne sediments in the western Gulf Coast.

Ground-Water Problems of the Coastal Plain

The broad lowland belt that extends along the Atlantic and Gulf coasts from New York to the Rio Grande is underlain by sedimentarystrata ranging in age from Cretaceous to Recent. These strata consist chiefly of alternating beds of sand or gravel and clay, but also include much limestone and also other kinds of rock. They are largely of marine origin, showing that during much of the time since the early Cretaceous the Coastal Plain has been at least partly below sea level. As a rule the beds dip gently toward the sea, and successively younger formations appear as one approaches the sea. Many of the sand and gravel beds and some of the limestones contain large quantities of water which they yield freely. The clayey beds function as confining beds. Thus, as a rule, the water-bearing beds are replenished by rain and snow at their outcrops; thence, the water percolates down the dip, and on the lower lands, nearer the sea, it is under sufficient artesian pressure to rise to the surface when wells are drilled into the water-bearing formations. Throughout the Coastal Plain ground water, recovered from pumped or flowing wells, is extensively utilized for domestic and industrial supplies; most of the public water supplies are obtained from wells, including a large majority of the smaller municipalities and some of the large cities, such as San Antonio, Houston, Memphis, Jacksonville, Savannah, and Camden; and west of the Mississippi, large supplies for the irrigation of rice and other crops are obtained from wells. For example, during the irrigation season, the daily pumpage from wells in the Grand Prairie rice district, in Arkansas, is about equal to the daily water consumption of the entire city of New York.

VIII.—Note On Some Post - Tertiary Mollusca From Ceylon

Some marine shells, associated with crab-remains,1 Balani, and small thread-like annelid tubes, from the Post-Pliocene deposits of north-eastern Ceylon, have been entrusted to me for determination by Dr. H. Woodward, F.K.S. They were collected by Mr. A. K. Coomaraswamy, B.Sc, Director of the Mineralogical Survey of Ceylon, and his description of the deposits containing the fossils forms the preface of this communication. Lithologically it is observable that there are two sets of specimens-those that occur in hard, water-worn nodules of clay, and others that were obtained from soft, dark, clayey beds found in situ. The fossils found in the clayey material may perhaps be rather older than those found in the nodules, but as two of the shells are common to each, viz. Placuna placenta and Potamides fluvialilis, it is certain that no great distinction in age is to be recognised.An examination of the species represented in the collection goes to prove that they belong to the existing fauna of the Indian Ocean, being similar to the life which is found in the creeks and back-watersof that sea, and consequently bearing a littoral or an estuarine facies.It is interesting to know of the presence of corresponding Post-Tertiary deposits crowded with shells forming the coastal areas of the Madras Presidency of India, particularly at Pondicherry, Cuddalore, Tangore, etc., for the history of which we are mainly indebted to the late Mr. H. F. Blanford (Mem. Geol. Surv. India, 1862, vol. iv, pt. 1, pp. 192,193). So numerous are the mollusca of these beds that they are utilised by the natives for the manufacture of lime.

The Sweetland Creek Beds

Previous articleNext article FreeThe Sweetland Creek BedsJ. A. UddenJ. A. Udden Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 7, Number 1Jan. - Feb., 1899 Article DOIhttps://doi.org/10.1086/608294 Views: 59Total views on this site PDF download Crossref reports no articles citing this article.