bluuebunny/crossref_metadata_2025_split huggingface dataset:
TURBIDITES OF THE NORTHEAST PACIFIC1
Authors: HORN D. R. , EWING M. , DELACH M. N. , HORN B. M. 
Published: June 2006

ABSTRACTThe northeast corner of the Pacific Ocean is a region of turbidity‐current activity. Cores from this area are dominated by very fine‐grained sand and medium‐grained silt that grade upward to clay. The results presented in this article are based on 217 textural analyses of turbidite layers comprising 30 piston cores.It is possible to distinguish proximal and distal facies of turbidites using characteristics of layering, grading and texture. Features of the proximal facies include wide range of layer thickness, maximum layer thickness, non‐grading, truncation of grading, textural reversals, and sand at the base of graded layers. Areas beyond main routes of submarine flows are sites of episodic addition of silt‐through clay‐sized sediment. The proportion, thickness, and mean grain size of the silt decreases with increasing distance from the main avenues of flow.
NUMERICAL ESTIMATES OF ANCIENT WAVES, WATER DEPTH AND FETCH
Authors: TANNER WILLIAM F. 
Published: June 2006

ABSTRACTA series of carefully controlled marine experiments, in which sand of known grain diameter and essentially perfect sorting was exposed to waves of various sizes, was supplemented by study of lakes of various widths (and hence differing values for fetch), in an effort to obtain relationships between parameters measurable in sedimentary rocks (i.e., ripple‐mark spacing) and paleogeo‐graphic information (water depth, wave height, wave length, and fetch). The results were subjected to regression analysis.Two equations were obtained, relating ripple‐mark spacing to grain size, water wavelength and water depth, with predictive abilities higher than 80%. Two equations were obtained, relating ripple‐mark spacing to grain size, water wave‐height and water depth, with a predictive ability of 75%‐80%. Two useful equations involved water wave‐length, and two involved water wave‐height; in general those based on water wave‐length were superior to those based on water wave‐height.In shallow‐water work, the pairs of values which can be obtained from equations included in this paper are highly limited in range, and thus define the paleogeographic unknowns reasonably closely. These pairs (or single values, as may be appropriate) can be inserted into three additional equations, which relate fetch to various wave parameters.An application is made to Jurassic rocks (lower Morrison sandstones) in northern New Mexico, which are interpreted as deposits of a large, shallow lake. Shorelines, where they cannot be located by inspection of the rocks, can be inferred fairly closely from the fetch data.
AN APPLICATION OF REFLECTED‐LIGHT DIFFERENTIAL‐INTERFERENCE MICROSCOPY: BEACH STUDIES IN EASTERN LONG ISLAND (U.S.A.)
Authors: WARNKE DETLEF A. , STAUBLE DONALD K. 
Published: June 2006

ABSTRACTA significant recent advance in microscopy has been the introduction of differential‐interference contrast (DIC) optics. In reflected‐light instruments, one “Nomarski prism” (a modified Wollaston prism) is used both for beam splitting and combining. In effect, two deformed wave‐fronts are produced which are laterally separated by a distance below the resolving power of the microscope. They are brought to differential interference by the analyzer, the effect being one of oblique illumination of the object.This system can be used in the study of mineral‐grain surfaces. For this purpose, conventional replicas of the grains are placed on petrographic slides which in turn are placed over a silvered mirror on the microscope stage. The Nomarski prism is then adjusted until the best contrast is achieved.For a test study, samples were collected from the intertidal zone of the Atlantic shore of eastern Long Island, mostly at localities which earlier were sampled by Krinsley et al. (1964) and studied in a classical investigation of quartz‐grain surface features by transmission electron microscopy. In the present study, a semi‐quantitative evaluation of surface features was attempted, using as guide the criteria set up by Krinsley and his school. The results of this study are tentatively interpreted as reflecting pronounced erosion in the study area, and increasing energy levels from East Hampton to Montauk Point.
VOLCANIC QUARTZ AS INDICATOR MINERAL IN GRAYWACKES
Authors: REIMER THOMAS O. 
Published: June 2006

ABSTRACTSamples from an uninterrupted sequence of Early Precambrian graywackes were investigated in order to disclose whether the amount of “volcanic” quartz, i.e., quartz without undulatory extinction, can give indications of quantitative changes in the composition of the source area. As non‐undulatory quartz usually is enriched in the smaller‐size fractions, only grains with an above average grain size were considered. The minimum grain size was fixed at 0.1 mm. In each thin section 100 grains were counted and separated into two groups, one without and one with undulatory extinction. Their relation to each other was then determined and plotted in a stratigraphic column. In the same column the relation of porphyry and tuff fragments to lava fragments was plotted. The resulting similarity of the two curves shows that the quartz ratio, as introduced here, can give indications about changes in the source area of graywackes.
COMPARISON OF SIEVING AND SETTLING TECHNIQUES FOR SIZE ANALYSIS, USING A BENTHOS RAPID SEDIMENT ANALYZER
Authors: SANFORD ROBERT B. , SWIFT DONALD J. P. 
Published: June 2006

ABSTRACTGrain‐size distributions of sand samples by means of a Benthos Rapid Sediment Analyzer were determined, using SCHLEE'S (1966) fall times. The results were compared with analysis of the same samples by sieving. The Rapid Sediment Analyzer (RSA) consistently overestimated the mean diameter of fine samples and underestimated the diameter of coarse samples relative to sieving. Since we used a wider settling column and a smaller sample weight than did Schlee, we infer that the differences were due to weaker grain interaction effects in our analyzer. Thus, by using Schlee's fall times, we overcompensated for these effects. We conclude that the “new grain parameter” of fall velocity (SENGUPTA and VEENSTRA, 1968) is indeed valuable. MIDDLETON'S (1967) psi transform is more convenient than the analogous phi transform in that it yields Middle‐ton sand classes of 0 to 5 psi, as compared to Wentworth‐Krumbein sand classes of ‐1 to 4 phi. However, use of fall velocity does not completely obviate the need to determine grain diameter, since this is the most expedient criterion with which to correct fall velocity to standard fall velocity.
AEOLIAN BEDFORMS—THEIR DEVELOPMENT AND ORIGINS
Authors: WILSON IAN G. 
Published: June 2006

ABSTRACTBedforms are defined and their variety outlined. Aeolian bedforms are shown to arise spontaneously by a two‐way interaction between surface form and airflow involving piecemeal material transfer between them. They eventually reach a dynamic equilibrium and transverse elements migrate downwind.Aeolian bedforms may be compounded of elements from four groups i.e., draas, dunes, aerodynamic ripples and impact ripples, each subdivided into transverse and longitudinal elements. There are no transitional forms between the elements of one of these eight subgroups and those of another and they are interpreted as being formed by different mechanisms. The possible nature of these mechanisms is considered and qualitative models for the development of generalised transverse and longitudinal elements given. Transverse and longitudinal elements may be combined in three different ways according to whether or not one element is displaced half a wavelength on crossing the other.
FEATURES OF THICK‐BEDDED SANDSTONES IN A PROXIMAL FLYSCH SEQUENCE, UPPER CAMBRIAN, SOUTHWEST TASMANIA
Authors: CORBETT K. D. 
Published: June 2006

ABSTRACTThe Upper Cambrian Singing Creek Formation, southwest Tasmania, includes a number of thick‐bedded, generally non‐graded or poorly graded sandstones as well as normal graded sandstones (turbidites), laminated siltstones, conglomerates, and numerous slump sheets. Most of the thick beds occur in composite units up to 30 m or so thick, within which there is interfingering and inter‐grading with thinner sandstones, and frequent amalgamation of beds. The composite units are separated by siltstone sequences, and in some cases at least appear to be large lenses. They are interpreted as being mainly channel deposits in a submarine fan complex.Many of the thick beds are either structureless throughout or have only a thin division of flat lamination (with parting lineation) near the top, followed in some cases by ripple mark. Some beds, however, show unusual wavy lamination or “dish structure” beneath the flat lamination, and this in turn may be underlain by contorted lamination. Narrow vein‐like de‐watering channels (elutriation columns) occur in the wavy‐laminated division of some beds.The thick beds form a gradational series with the normal graded beds, and apparently represent the over‐thickened basal parts of such beds, i.e., they are lateral variants of the normal turbidites. Similar beds called “grain‐flow deposits” by Stauffer (1967) also appear to be proximal turbidites. The origin of the wavy lamination and dish structure is problematical but could be related to mass shearing and dewatering during consolidation in the manner observed by Middleton (1967) for experimental high‐concentration underflows.
ARAGONITIC OOIDS1: EXPERIMENTAL PRECIPITATION FROM SEAWATER IN THE PRESENCE OF HUMIC ACID2.
Authors: SUESS ERWIN , FÜTTERER DIETER 
Published: June 2006

ABSTRACTHumic acid dissolved in artificial seawater influenced the morphology, internal structure, and composition of aragonite when precipitation was induced with dilute Na2CO3 solution. At sodium humate concentrations of around 20 mg/1, numerous brownish spherical aragonite bodies developed within one day at 25 °C. The spheres ranged in size from 10–100 microns and resembled natural marine ooids. They formed with gentle agitation of the solution as well as with no water movement at all. The typical structure of natural ooids consisting of concentric alternating aragonite and organic laminae was experimentally duplicated as layers of aragonite crystals alternating with humate membranes; however, in contrast to natural ooids, the individual aragonite crystals here were oriented radially with their c‐axes. The aragonite of the spheres contained about 20 wt. % more strontium than the aragonite precipitated experimentally without the addition of sodium humate, and organic carbon content of the spherical aragonite was about 7% by weight.
An appraisal of the computation of statistical parameters in grain size analysis
Authors: SEWARD‐THOMPSON B. L. , HAILS J. R. 
Published: June 2006

ABSTRACTA computer program has been written to overcome the limitations of two published programs that compute statistical parameters in grain size analysis. This program uses all available data, obtained from standard sedimentological analyses, regardless of phi interval, and computes statistical parameters by direct integration of a linear approximation to the cumulative curve. This has the advantage that the distribution curve is known and hence the limitations of the parameters obtained can be assessed. Furthermore, it is argued, with examples, that this approximation introduces no greater degree of inaccuracy than is already present in standard sampling and analytical procedures.
Clay mineralogy of Triassic sediments in southern Israel and Sinai
Authors: HELLER‐KALLAI L. , NATHAN Y. , ZAK I. 
Published: June 2006

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).
Incorporation of uranium in modern corals
Authors: AMIEL ABRAHAM J. , MILLER DONALD S. , FRIEDMAN GERALD M. 
Published: June 2006

ABSTRACTUranium occurs in corals at three sites: 1, in organic matter; 2, adsorbed on the surfaces of skeletal aragonite; and 3, in the aragonite lattice. Organic matter incorporates from sea water by chelation 40–70 ppm uranium; skeletal aragonite incorporates only 3 ppm. However, as the organic fraction is low (0·1%), its high concentration of uranium does not significantly affect the total concentration of uranium in the coral. A negligible concentration of uranium, 40–60 ppb, is adsorbed on skeletal aragonite from which it is readily leached or exchanged. This low concentration of adsorbed uranium (<2% of the total uranium in skeletal aragonite) is related to the very small specific surface area (1·5–1·8 m2/g of the corals.
Diagenetic development of a Precambrian limestone as interpreted from a modern analogue
Authors: MÜLLER GERMAN , SCHÖLL WALTER U. , TIETZ GERD 
Published: June 2006

ABSTRACTA strong correlation in the geometry and mineralogy of two cement generations of a Quaternary with a Precambrian calcarenite enables us to reconstruct the diagenetic history of the Precambrian limestone. Both calcarenites contain two cement generations (A and B) of which A consists of dolomite, B of calcite.The following diagenetic stages can be recognized: after deposition of the allochems in a shallow marine environment, cementation in the intertidal zone with magnesian calcite (cement A) led to the formation of beachrock (Stage 1).By lowering of the sea level, the beach rock was shifted into the supratidal zone, but still remained under the predominant influence of the sea water (breakers, spray). During longer periods of aridity, the magnesian calcite of cement A and of the allochems was transformed into dolomite by brines derived from sea water with very high Mg/Ca ratio (> 15), whereas aragonite and calcite remained unaffected.After further lowering of the sea, an increasing influence of meteoric water caused the wet transformation of aragonitic allochems to sparry calcite and to the precipitation of sparry calcitic cement B.
Phase differences between bed configuration and flow in natural environments, and their geological relevance
Authors: ALLEN J. R. L. 
Published: June 2006

ABSTRACTIn nature where unsteady flows prevail, the characters of bed configurations lag, or differ in phase from, the flow conditions. This is demonstrated from quantitative data for dune beds in the Fraser River (Canada) and the Gironde Estuary (France), where the flow conditions change ahead of the bed form by as much as 1/4 period. Qualitative evidence for lag abounds, for instance, substantially unmodified dunes exposed during low water.The existence of lag appears to confuse attempts to establish from field data the relationships between bed‐form properties and flow conditions and, at the same time, makes difficult the confident application to field situations of formulae based on steady‐state experiments or theories. Unfamiliar types of field study and experiments are needed to increase understanding of the degree and precise significance of lag.
Size and shape sorting in a Dutch tidal inlet
Authors: WINKELMOLEN A. M. , VEENSTRA H. J. 
Published: June 2006

ABSTRACTA tidal inlet system with an outer tidal, delta, situated between two barrier islands along the north coast of Holland was studied for size and shape sorting. With size data different sand types can be distinguished and in individual samples distinct grain populations can be recognized in some cases. Graphs of shape values, plotted against the size intervals of samples also reveal the presence of different grain populations, together with their genetical significance.The following conclusions could be drawn.There is no sand transport directly from island to island. Sand up to 400 μm enters the tidal inlet, is sorted out in the tidal flat area and partly re‐enters the sea via the outer tidal delta. On the delta, the sediment is split up again in different populations. A lag deposit is left behind on the frontal part of the delta. The rest of the sand either re‐enters the tidal inlet cycle or contributes to the beach building of the next island. In the offshore environment, sand movement by wave‐induced currents is restricted to the shallow zone. In deeper water, part of the sediment is relatively immobile and has preserved inherited characteristics from the early Holocene transgressive phase. In front of Ameland, fossil barrier‐face deposits‐are present, off Schiermonnikoog the sea floor contains old tidal channel deposits.
Les minerais de fer de l'Ordovicien inférieur du bassin de Bretagne‐Anjou, France*
Authors: CHAUVEL JEAN‐JACQUES 
Published: June 2006

RÉSUMÉLes ressources en mineral de fer du bassin de Bretagne‐Anjou proviennent essentiellement de quatre couches de mineral sédimentaire situées dans le grès armoricain (Arénig). Les paragenèses les plus fréquentes réunissent le quartz, la magnétite, la sidérite et des silicates (bavalite, stipnomélane). La paragenèse à hématite et la paragenése à pyrite sont plus rares. L'étude pétrographique permet en outre de définir deux types de minerais: un type à allochems et un type sans allochems.L'examen des variations de paragenèses et de puissance des couches de minerai permet de reconstituer en partie l'histoire de la sédimentation ferrifère: le fer est mis en solution sur les reliefs cadomiens émergés. Lors de la transgression paléozoïque le fer parvient dans le bassin de sédimentation qui est peu profond et encombré d'iîles et de hauts‐fonds. Suivant les conditions locales le fer précipite alors soit sous ses formes oxydées (magnétite, hématite), soit sous ses formes réduites (bavalite, sidérite, pyrite). Les facteurs essentiels de la différenciation des paragenèses sont l'épaisseur de la tranche d'eau, l'agitation de l'eau et la teneur du sédiment en matiére organique. Dans certains cas un phénomène de concrétionnenment au sein du sédiment donne naissance aux allochems qui peuvent alors être repris, mis en suspension et déposés.
Non‐combustible suspended matter in surface waters off eastern Asia*
Authors: HONJO SUSUMU , EMERY K. O. , YAMAMOTO SATOSHI 
Published: June 2006

ABSTRACTA total of about 1100 well‐distributed samples of suspended matter in surface waters off the length of eastern Asia are available. From these samples, 180 were selected for detailed examination of the non‐combustible fraction using optical and electron microscopy along with computer methods of particle measurement and counting. The results showed that, generally, all major components of the suspended matter are most abundant in the nearshore belt (combustible fraction, mineral grains of silt size, skeletal debris, and clay minerals), the result of mechanical transport of detrital sediment and chemical transport of nutrients from the land. Mineral grains of silt size average about 2%, skeletal debris plus clay minerals—23%, and combustible organic matter—75% of total sample weights, but the last two categories vary over a wide range depending upon geographical positions of the samples. Most evident is an oceanward decrease in percentage and concentration of the total noncombustible fraction and an oceanward increase in median diameter of the mineral grains.
Early marine lithification of the nodular limestones in the Silurian of New Brunswick
Authors: NOBLE J. P. A. , HOWELLS K. D. M. 
Published: June 2006

ABSTRACTA sequence of irregular nodular limestones in the Silurian of northern New Brunswick appear to have undergone early marine lithification. Nodules and crusts formed soon after deposition in the argillaceous lime sediments by sporadic diagenetic precipitation of calcium carbonate and were subsequently modified by differential compaction and minor flowage.While lack of both borings and encrusting organisms on the nodules indicates they were not ‘hard grounds’, computed porosities at the time of lithification based on the ratio of carbonate to insoluble residues suggest lithification depths within a few tens of feet of the sediment‐water interface. Consideration of the availability of calcium carbonate suggests lithification very close to the sediment surface.
Interdistributary bay sequences and their genesis
Authors: ELLIOTT T. 
Published: June 2006

ABSTRACTInterdistributary bay sedimentation is dominated by flood‐generated incursions from the distributaries. There are three processes by which sediment‐laden flood waters can be transferred to the bay: overbank flooding, crevassing and avulsion. These processes combine to produce a family of sedimentary sequences, the majority of which are small‐scale coarsening upwards sequences representing infilling of the bay. Subordinate related sequences include those of small‐scale (crevasse) channels and larger scale (distributary) channels. Spits or beaches at the mouth of open interdistributary bays produce larger scale, wave‐dominated coarsening upwards sequences.A model of bay sedimentation concerning a recently initiated (hypothetical) distributary is presented. Four phases of sedimentation (overbank flooding, crevasse splay, minor mouth bar—crevasse channel couplets and avulsion) characterize the history of the distributary, and it is postulated that the phases are genetically related to alluvial ridge development.
Vesiculated tuffs and associated features
Authors: LORENZ V. 
Published: June 2006

ABSTRACTVesiculated tuffs are tuffs that contain vesicles between the ash particles. Formation of the vesicles is the result of trapping of steam, the transporting agent of volcanic base surges, in wet, muddy or sticky ash deposited by the base surges. Vesiculated tuffs are described from various maars and tuff‐rings in Europe (Iceland, France, Germany) and USA together with associated surface features such as: gravity flowage ripples, mud flow channels, current ripples, and current ridges. Other features described are: plastering of ash against obstacles and vesiculated accretionary lapilli, the latter containing vesicles in the outer layer.Vesiculated base surge deposits probably contained as much as 20–30% of interstitial water and fell out of the base surge clouds en masse owing to non‐free flow and consequent accretion.
Vanished evaporites: revisited
Authors: SCHREIBER B. CHARLOTTE 
Published: June 2006

ABSTRACTDetrital particles were found as a sand‐silt layer in a deep‐sea Messinian Stage (Upper Miocene) salt deposit in the Mediterranean Basin (Balearic Sea). These particles include worn and limonite‐coated quartz, feldspar, glauconite, volcanic glass, reworked Messinian foraminifera and some lutecites. The lutecites are not original to the salt and taken in their association with the other detritus, especially the foraminifera, suggest syndepositional reworking of exposed Messinian evaporites.
Quartz‐sandy, grazing‐contoured stromatolites from coastal embayments of Mauritania, West Africa
Authors: SCHWARZ HANS‐ULRICH , EINSELE GERHARD , HERM DIETRICH 
Published: June 2006

ABSTRACTA new occurrence of Recent stromatolites different from those known up to now has been discovered on tidal flats of the Bay of Saint‐Jean (near Cape Timiris). Their most remarkable features are predominance of quartz sand instead of carbonate, characteristic surface‐contouring by grazing fish, absence of cementation, intensive reworking by crabs, and connection with saline sabkha deposits.Entrapment of sand grains and great resistance of the algal sheaths are most important for stromatolitic growth, although today destruction appears to prevail over accretion. Quartz sand of aeolian dunes and carbonatic pellets of aragonitic ooze feeders are the main constituents of the stromatolitic sediments.According to the tidal range the following zonation of the algal mat exists: (A) knoll and cuspate zone, (B) flat zone, (C) gas‐domed zone, and (D) crinkle zone.