Sediment Constituents Research Articles

Bottom Sediments of Georges Bank

ABSTRACT A survey of Georges Bank bottom sediments was undertaken to provide basic data for use in studying the relationships between substrate composition and the occurrence of benthic animals, especially those which are common foods of fishes. Particle side composition is the principal sediment character that was studied. Six statistical measures of particle size composition are given in order to designate the main features of the size-frequency distribution of each sample. These measures are: median diameter, mean diameter, coefficient of sorting, kurtosis, and two measures of skewness. In addition to these parameters, organic content, shell content, color, and textural classifications are included. In the presentation and discussion of the data, special emphasis is given to the geographic distribution of the various sediment constituents and particle size composition.

Distribution of organic constituents in the shelf sediments off Yamagata Prefecture

Distribution of extractable organic matters, hydrocarbon content and some other organic compounds in the bottom sediments which were collected from the continental shelf off kamo and Fukura, Yamagata Prefecture, has been studied with reference to the distance from the coast, and the lithologic features of the sediments. The small quantities of lipoid substances were obtained from all the selected 67 bottom samples. they are generally subject to the distribution of sediments which can be divided into three zones such as near-shore fine sand to the depth of nerly 40m (average value 0.04%), off-shore coarse sand between 40 to 70 m (0.06%), and silt and clay below 100m depth (0.08%). The high extractable contents are concentrated in the submarine basin in the east side of Tobishima Island, and in the narrow trough running in NNE direction in the south of this basin (0.07 to 0.18% of the samples). In these places, there are also relatively high hydrocarbons and asphaltene contents of the column chromatographic fractions. Besides, the high contents are partly extracted in sapropelic mud contained in the off-shore coarse sand zone off Kamo, but the rate of chromatographic fractions is not always high. Free sulfur was obtained from the samples of the regions above mentioned. It seems that the free sulfur is contained within the bottom samples characterized by high extractable fractions. the column chromatographic fractions of these lipoid substances show the high hydrocarbons and asphaltenes in composition, and the high paraffinic in hydrocarbon proportions are more than that of the lagoon sediments from the Hachiro-gata.

Organic constituents of recent sediments (2nd report)

The lagoon sediments of Hachiro-gata, near Akita City, consist of a copropelic facies accumulation of peat, peaty silt, and dark grey or green colored clay, in which carbonaceous matter, plant fragments, and shell remains etc. are widely distributed. Extractable organic matter, hydrocarbon content, and some other organic compounds of the 45 specimens collected from these sediments were determined. Hydrocarbon fractions were separated from extractable organic matter by liquid chromatography on alumina. It is ascertained that the contents of hydrocarbons increases and the amounts of extractable organic matter decreases with increasing depth of burial below the floor of the lagoon. In this paper, their stratigraphical distribution and some alteration of organic matters in sediments are described.

Studies on the organic constituents of recent sediments (1st report).

Studies on the organic constituents of recent sediments (1st report).

Nature and origin of the pyrite deposits of Saint Lawrence and Jefferson counties, New York

In St. Lawrence and Jefferson Counties, New York, there are 19 known occurrences of pyrite concentration of sufficient magnitude to warrant consideration as possible sources of sulfur. The important deposits occur in a belt about 35 miles long and three to four miles wide extending northeast from the vicinity of Antwerp. This belt lies within the Grenville Low-lands region of the northwest Adirondacks, southeast of the St. Lawrence River.The bedrock is principally Precambrian Grenville metasediments and associated granitic rocks, but abundant small outliers of flat-lying Cambrian Potsdam sandstone occur throughout the region. The rocks of the isoclinally folded Grenville series have a marked foliate structure parallel to the northeast regional trend of the lithologic units and major folds, and generally dip northwest within the pyrite belt. The Grenville series is 15,000-16,000 feet thick in the Lowlands region.The earliest pyrite mining in the region was in 1883-4 at the Stella mine; it ceased in 1921, at which time about 600,000 long tons of concentrates averaging about 40 percent sulfur had been produced. Pyrite and lesser amounts of pyrrhotite are essentially the only sulfides present. The deposits occur in rusty-weathering pyritic gneisses, which are essentially chloritic and graphitic quartz-feldspar-mica gneisses containing more or less disseminated pyrite. The ore veins represent concentrations of pyrite within the rusty gneisses and occur as thin sheets parallel to the gneissic foliation. Thirteen analyses indicate a sulfur content from 20.2 to 35.6 percent, and average 25.6 percent sulfur.The pyrite of the ores crystallized later than the gangue minerals, with the possible exception of sericite, and partially replaces them, chlorite being the most readily replaced. The graphite content of the ores characteristically parallels increases in the pyrite content.The pyrite deposits are considered to be concentrations of iron sulfides formed from inherent constituents of the parent sediments from which the rusty gneisses were derived. It is believed that the parent sediments were argillaceous sandstones containing abundant organic impurities and some intercalated calcareous layers. The late-stage formation of abundant chlorite and the evident mobilization and recrystallization of sulfides and graphite well after the period of metamorphism are attributed to the circulation of aqueous solutions.

Om spektrokemisk analys av sediment och bergarter

Abstract A brief survey is given of the laboratory studies on analytical technique by means of combined chemical and spectrographic methods for the determination of major and minor constituents in sediments and igneous rocks. For details the reader is referred to a paper: On the spectrochemical analysis of igneous rocks, sediments, and ores by S. Landergren and W. Muld. Microchimica Acta 1955 (in press).

The age of the sediment collected at Challenger (1875) Station 225 and the distribution of Ethmodiscus rex (Rattray)

The sediment sample collected by H.M.S. Challenger in 1875 at her Station 225 is shown to be from an outcrop of Middle Tertiary age. Therefore the presence of the diatom Ethmodiscus rex (Rattray) in this sediment sample is not the result of its having lived in the overlying waters in Recent geological time. In two other recorded occurrences, this diatom is believed to be associated with other sedimentary constituents which are, at least in part, of Tertiary age. Five of the Radiolaria occurring at Challenger Station 225 are discussed briefly.

On the spectrochemical analysis of silicate rocks

In this laboratory, methods have been worked out for the spectrochemical analyses of the major and minor constituents of rocks, sediments and ores. The samples to be analysed are fused with potassium or sodium hydroxide in a silver crucible and then dissolved in dilute nitric or hydrochloric acid. For the spectrochemical determination of the major constituents in this solution two methods have been employed alternatively. (1) In a high voltage spark between a graphite rod an upper electrode and a slowly rotating graphite disc the solution is carried into the spark column by the rotation of the disc dipping in the solution. (2) The solution is dispersed by means of an atomiser and injected into an arc or spark column through a small bore, 1.5 mm diam. in the purified carbon rod which serves as the lower electrode, and is 4 mm diam. The counter electrode is a purified graphite rod 6.6 mm diam. turned to a conical tip with included angle of 120°. For the determination of the major constituents a Feussner controlled spark is used. When recording the spectra photographically the accuracy of the method is measured by a standard deviation of about 3.5% for the SiO 2 determination; for the other major constituents of rocks (Al, Fe, Ca, Mg and the alkali metals) a standard deviation of 2–2.5% is obtainable.

The Contribution of Clay Mineralogy to the Study of the Diagenesis of Sediments

History repeats itself. Forty years ago, when the coarser detrital and authigenic constituents of sediments were first being systematically examined, it became evident that their significance could not be assessed until we knew, in broad outline at least, the characters of the assemblages in all the major stratigraphical divisions. The more finely-grained materials were at that time in the main intractable: their investigation has had to await the development of the now familiar techniques utilized by the Group.

Fernvale and Viola Limestones of South-Central Oklahoma

The Fernvale and Viola limestones of south-central Oklahoma are exposed in the Arbuckle and Wichita mountains, and are found in the subsurface in much of the Mid-Continent region. Fernvale (Richmond) and Viola (Trenton) strata are chiefly limestone with varying amounts of chert, dolomite, detrital quartz sand, and minor sedimentary constituents. Isopachous and lithologic characteristics of these Ordovician formations indicate that the strata were deposited in the northwest-trending Arbuckle geosyncline having a broad platform in the Seminole area. The Fernvale limestone is thickest in a northwesterly trend extending from the Wapanucka graben to the Pauls Valley anticline, whereas the Viola limestone is thickest in a northwesterly trend approximately parallel and corresponding with the zone of maximum sedimentation in pre-Viola basins of deposition in the Arbuckle geosyncline. The Fernvale limestone contains abundant detrital quartz sand where thickest and the crystallinity ranges from very coarse on the platform to medium in the basin. The Viola limestone is predominantly dolomitic on the platform, cherty on the platform slope, and siliceous in the basin. Fernvale and lower Viola limestones are essentially planar-bedded in the area of maximum deposition, whereas the upper and middle Viola beds are irregularly bedded in most of south-central Oklahoma. Regionally correlatable lithologic characteristics of the Viola limestone indicate that the formation is divisible into four principal members of which the uppermost and the lowermost wedge out north-eastward from the basin to the platform. With a few local exceptions, such as the Franks and Wapanucka grabens, all members of the Viola limestone thicken regularly from the platform to the basin. The Viola limestone of the Arbuckle facies is areally divisible into six sub-facies to which the following names are applied: Seminole, McAlester, Fitts, Wapanucka, Tishomingo, and Ardmore. Though there are significant differences in Viola sections of the six stratigraphic provinces, their boundaries are gradational and any suite of Viola cuttings or surface samples may be assigned to its correct province through lithologic characteristics alone, without the aid of specific location on a map. End_Page 2183------------------------------ Fig. 1. Composite stratigraphic diagram of south-central Oklahoma. End_Page 2184------------------------------ Isopachous studies of the Fernvale and Viola limestones show that the orogenies which caused the folds and faults of the Arbuckle Mountains, and adjacent subsurface anomalies, had no effect upon the original Fernvale-Viola basins during the deposition of those strata. The significant lack of correlation between Viola production and maximum intercrystalline porosity, or location of the wedge-edges of the members, suggests that productive Viola reservoirs are present in localities of fortuitous orogenic shattering rather than in broad areas where maximum porosity may occur because of lithogenesis of the carbonate sediments.

Studies on Redox Potential of Marine Sediments

The redox potential of sediments may be used advantageously in the study and interpretation of the morphology, general nature, and chemical processes in unconsolidated sediments. The redox potential is believed to have a pronounced effect on the diagenesis of sedimentary materials, including the conversion of organic matter into petroleum. The modern concepts of oxidation, reduction, and redox potentials are discussed. The redox potential is measured in volts and is expressed as an Eh value, Eh being the e.m.f. of an oxidation-reduction system referred to a standard hydrogen half-cell. The Eh of a system is a quantitative expression of its oxidizing or reducing intensity. Redox potential may be defined as the electron-escaping tendency of a reversible oxidation-reduction system, and thus is an intensity factor. The reducing or oxidizing capacity of sediments is independent of the redox potential, although there is a relation between the intensity and capacity factors. The pH and temperature at which measurements are made influence the redox potential of sediment samples. The Eh of sediments, like the pH, can be measured either colorimetrically or electrometrically. A description of the methods of measuring the Eh of sedimentary materials helps to clarify the concepts of redox potentials. Methods of measuring the capacity as well as the intensity factor are given. Data on more than 1,000 samples of bottom deposits indicate that each type of sediment has its own characteristic Eh and pH. Eh values ranging from +0.350 to -0.500 volt have been observed in samples of recent sediments in which the pH ranged from 6.4 to 9.5. As a very general rule, the pH of sediments increases with core depth and the Eh decreases, or conditions become more alkaline and more reducing with core depth. The reducing capacity decreases with core depth. Positive Eh values are generally characteristic of bottom deposits which are well oxygenated, those which consist of coarse sediments, or those which are poor in organic matter. Negative Eh values are characteristic of bottom deposits rich in organic matter and which consist largely of fine sediments. An abundance of readily decomposable organic matter appears to promote reducing conditions. In the presence of organic matter, bacteria and allied microorganisms create reducing conditions. Such conditions are maintained by certain organic compounds, ferrous iron, reduced manganese, hydrogen sulphide, and other inorganic constituents of sediments. End_Page 477------------------------------

Distribution of radioactivity in ancient sediments

By the use of beta-ray counters a method has been developed for the determination of the three radioactive constituents in ancient sediments—potassium, thorium, and uranium. Owing to the high efficiency of the counters to beta radiation only 3 grams of sample are required. The apparatus is calibrated with radioactive standards. Over 300 samples representing several distinct types of sedimentary rocks have been measured. The highest concentration of all three radioactive constituents was found in the Antrim formation, an organic black shale of Mississippian-Devonian age in Michigan. Similar characteristics were observed in the Chattanooga formation from wells in Oklahoma. These black shales show maxima of organic matter, uranium, thorium, potassium, colloidal size grades, and thorium/uranium ratio. The radioactivity measurements are complicated by the high emanating power of these shales. Logs of beta-ray activity, alpha-ray activity, and estimated per cent black shale have been made on cuttings from Pure No. 3 Gingrich, Osceola County, Michigan, between depths of 1600 and 3200 feet. These logs include the Marshall and Ellsworth formations, the Antrim shale, and the Traverse limestone. The results indicate significant variations in the distribution of radioactive elements and organic materials in these sedimentary rocks. It is concluded that the principal loci of radioactivity are (1) in heavy minerals in sands and sandstones, (2) in potassium-bearing sediments, and (3) in sediments of colloidal deposition. These relationships are of possible importance in defining the source beds of petroleum.

Persistence of Heavy Minerals and Geologic Age

The apparent increase in complexity of the heavy-mineral suites of arenaceous sediments with decrease in age of the deposit is confirmed by compilation from published records. Such increase in number of mineral species in the younger deposits is due to (a) greater complexity of terrane from which the younger sediments were derived or (b) disappearance by solution of the less stable species in the older deposits. The latter alternative is shown to be the correct explanation, since the order of persistence of the common rock-making heavy minerals worked out from the tabulation is identical with Goldich's series, which is the order of survival of minerals subject to weathering. The stability series is expanded to twenty-five common constituents of sediments.

Mineral Analyses of Some Ordovician Rocks from Carnarvonshire

Very little work seems to have been done on the petrology of the rarer constituents of the older Palaeozoic sediments and their associated igneous rocks, partly no doubt on account of the extra amount of work entailed in crushing these extremely hard compact rocks, and partly owing to the comparative paucity of the “heavy” residues obtained, which give small reward for the energy expended. Such work, however, is highly important as indicating further sources of supply, to which workers on the petrology of the newer rocks may look, and it may be here emphasized that Wales has unfortunately suffered neglect in this respect. It is to help remedy this defect that the present paper is put forward.

The Petrography of the Cretaceous and Tertiary Outliers of the West of England

T he significance of the outliers of Cretaceous and later age resting on the Palæozoic strata of Devon and Cornwall has been frequently noted, especially with reference to the evidence yielded by them of the extent of the great marine transgressions. The details of their petrology, considered in relation to their present altitude and geographical location, are dealt with in this communication, and an attempt is made to throw light on the conditions of their deposition and the source of their constituents. Lying as they do, around and among some of the most important igneous masses in the country, they may be expected to afford evidence regarding the stability of detrital minerals and of the source of constituents in sediments of the same age, but of wider geographical distribution. A comparison of the petrography of these outliers with that of the Greensand, Eocene, and Pliocene strata farther east has therefore been instituted. These outliers in the West Country may be grouped thus :— Cretaceous (Upper Greensand). Great Haldon Hills (Devon). Little Haldon Hills (Devon). Eocene (? Bagshot). (?) Marazion, near Penzance (Cornwall). Buckland Brewer, near Bideford (Devon). Great Haldon Hills. Little Haldon Hills. Oligocene (Aquitanian). Petrockstrow, near Torrington (Devon). Bovey Tracey and Newton Abbot (Devot). Pliocene. St. Erth and Lelant (Cornwall). Crouza Down, near St. Keverne (Cornwall). St. Agnes (Cornwall), together with certain deposits age (see p. 223). The respective heights of the upper and lower surfaces of the deposits above Ordnance-datum are as follows :— II. E vidence