Locomotion and feeding traces in Champlain Sea subaqueous outwash deposits near Ottawa, Canada

1990 ◽  
Vol 27 (11) ◽  
pp. 1495-1503 ◽  
Author(s):  
Dana L. Naldrett
Keyword(s):  
Depositional Environment ◽  
Close Association ◽  
Circular Cross Section ◽  
Fine Sand ◽  
Bedding Plane ◽  
Life Forms ◽  
Silty Clay ◽  
Bedding Planes ◽  
Algae And Bacteria ◽  
Medium Silt

Locomotion and feeding traces (repichnia and fodichnia) observed on bedding planes of rhythmically bedded subaqueous outwash deposits in the Brazeau sand pit, Nepean, Ontario, Canada, are the first bedding-plane traces described in detail from the western Champlain Sea. The Planolites–Palaeophycus-like and Taenidium-like traces are cylindrical with circular cross section, smooth sided, unlined, sinuous, sometimes branching, and sometimes meniscate. Organisms producing the traces are tentatively identified as errant polychaetes or nemerteans. The enclosing sediments are rhythmic couplets of alternating fine sand and silt layers overlain by silty clay and fine–medium silt layers. The occurrence of traces within the uppermost portion of the coarse unit, and within the coarser, upper portion of the overlying fine unit, and the rhythmic alternation of coarse and fine layers suggest these deposits may be varves. The traces formed during the more biologically suitable summer months but were preserved only during the latter portion of the summer. Traces are distributed on bedding planes in close association with bedforms and show a high correlation with the substrate and possibly the hydrodynamic regime. This is interpreted as indicating a strong preference in feeding behaviour. The presence of traces in the subaqueous outwash environment necessitates rethinking of the depositional environment to include the presence of errant polychaetes, nemerteans or similar organisms, and the lower life-forms such as epontic algae and bacteria on which they live.

Tectonic ripples and associated minor structures in the Silurian rocks of Denbighshire, North Wales

1970 ◽  
Vol 107 (1) ◽  
pp. 51-60 ◽  
Author(s):  
P. T. Warren ◽  
R. K. Harrison ◽  
H. E. Wilson ◽  
E. G. Smith ◽  
M. J. C. Nutt
Keyword(s):  
Bedding Plane ◽  
Linear Structures ◽  
Regional Stress ◽  
Bedding Planes ◽  
North Wales ◽  
Tectonic Origin

SummaryStructures affecting certain bedding planes, and simulating sedimentary ripples, have been found at a number of horizons in the Wenlock and Ludlow rocks of Denbighshire, North Wales. The megascopic appearance of the ripples, including their association with linear structures and their miscroscopical fabric are described in detail; and it is concluded that they are of tectonic origin, being manifestations of bedding-plane slip. The orientations of the ripples and other minor structures suggest that the stress responsible was the regional stress that produced folding, faulting and cleavage.

Well Shear Associated with Conventional and Unconventional Operations: Diagnosis and Mechanisms

2021 ◽  
pp. 1-18
Author(s):  
Russell T. Ewy
Keyword(s):  
Cross Sections ◽  
Slip Surface ◽  
Bedding Plane ◽  
Vertical Stress ◽  
Natural Fracture ◽  
Shear Deformations ◽  
Horizontal Fracture ◽  
Bedding Planes ◽  
Shear Slip ◽  
Fluid Pressurization

Summary Wells are sometimes deformed due to geomechanical shear slip, which occurs on a localized slip surface, such as a bedding plane, fault, or natural fracture. This can occur in the overburden above a conventional reservoir (during production) or within an unconventional reservoir (during completion operations). Shear slip will usually deform the casing into a recognizable shape, with lateral offset and two opposite-trending bends, and ovalized cross sections. Multifinger casing caliper tools have a recognizable response to this shape and are especially useful for diagnosing well shear. Certain other tools can also provide evidence for shear deformation. Shear deformations above a depleting, compacting reservoir are usually due to slip on bedding planes. They usually occur at multiple depths and are driven by overburden bending in response to reservoir differential compaction. Shear deformations in unconventional reservoirs, for the examples studied, have been found to be caused by slip on bedding planes and natural fractures. In both cases, models, field data, and physical reasoning suggest that slip occurs primarily due to fluid pressurization of the interface. In the case of bedding plane slip, fracturing pressure greater than the vertical stress (in regions where the vertical stress is the intermediate stress) could lead to propagation of a horizontal fracture, which then slips in shear.

Shark fauna and depositional environment of the earliest Cretaceous Vitabäck Clays at Eriksdal, southern Sweden

2002 ◽  
Vol 93 (1) ◽  
pp. 59-71 ◽  
Author(s):  
Jan Rees
Keyword(s):  
Depositional Environment ◽  
The Other ◽  
Silty Clay ◽  
Southern Sweden ◽  
Lower Salinity ◽  
Shark Teeth ◽  
Large Bulk ◽  
Single Tooth ◽  
Main Portion ◽  
Fin Spines

ABSTRACTA section of the Vitabäck Clays at Eriksdal in southern Sweden was sampled for vertebrate fossils. Large bulk samples were collected from three horizons, including two coquina beds, VC3 and VC11, and a silty clay bed, VC7. Shark teeth are very common and constitute the main portion of the vertebrate material discussed herein. The selachian tooth faunas are almost exclusively represented by hybodonts, although a single tooth from a neoselachian shark, Squatinidae indet., was recorded from one horizon (VC3). Hybodont species identified from the Vitabäck Clay samples include Egertonodus basanus, Hybodus parvidens and Parvodus rugianus. Hybodont remains, other than teeth, include five morphotypes of placoid scales, incomplete cephalic spines and fragmentary fin spines.Other fossil groups represented in the sieved residues from the bulk samples include bivalves, gastropods and bony fish. Together with the selachians, they indicate fluctuating palaeosalinities in the area. The lower coquina bed, VC3, includes taxa indicating mesohaline conditions while the composition of the fauna in the other coquina bed, VC11, suggests oligohaline settings. In bed VC7, the presence of amphibian remains and the rarity of selachian fossils indicate an even lower salinity. Palynomorphs from the basal part of the section, immediately below bed VC3, indicate an earliest Cretaceous (Berriasian) age.

scholarly journals Influence of Bedding Planes on the Mechanical Characteristics and Fracture Pattern of Transversely Isotropic Rocks in Direct Shear Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Lei Xia ◽  
Yawu Zeng ◽  
Rong Luo ◽  
Wei Liu
Keyword(s):  
Mechanical Characteristics ◽  
Numerical Models ◽  
Transversely Isotropic ◽  
Bedding Plane ◽  
Particle Flow Code ◽  
Fracture Plane ◽  
Direct Shear ◽  
Geometrical Properties ◽  
Bedding Planes ◽  
Fracture Patterns

Bedding planes are the primary control on the anisotropy of mechanical characteristics and fracture patterns in rock. To analyze the influence of the geometrical properties of bedding planes on the direct shear strength characteristics and fracture patterns of transversely isotropic rocks, numerical models were established using an improved modeling method using Particle Flow Code. The results of the numerical model were in good agreement with those of the physical experiments of an artificial rock mass containing a single bedding plane. The results show that the shear fractures with a range of bedding plane geometries can be divided into two patterns. When the inclination angles of the bedding planes were larger or smaller, a thoroughgoing fracture plane was formed near the preexisting shear fracture plane. On the other hand, the intact rock was broken into many parallel sheets.

Burrowed Phacops rana from the Moscow Formation of New York

1988 ◽  
Vol 62 (2) ◽  
pp. 311-312 ◽  
Author(s):  
Paul D. Zell
Keyword(s):  
New York ◽  
Visual Field ◽  
Bedding Plane ◽  
Sediment Surface ◽  
Bedding Planes

The trilobite Phacops rana has previously been documented in two life positions: horizontally outstretched and enrolled (Hall and Clarke, 1888). A specimen of Phacops rana was recovered in an unusual life position from the Windom Member of the Moscow Formation (Figure 1). It was collected from a borrow pit along Castle Hill Road, 1 km east of Earlville in Chenango County, New York. The trilobite appears to have burrowed tail first into the substrate, with only part of the cephalon and one or two thoracic segments exposed above the sediment surface. The orientation of the eyes indicate that the visual field was horizontal. The thorax angled into the substrate at an angle of approximately 50° from the horizontal, with the pygidium tilted dorsally relative to the thorax. Compaction effects appear to be slight. Because the specimen was found in situ, no doubt exists as to its orientation with respect to bedding. It is also evident from bedding plane surfaces that this trilobite had burrowed, and was not simply draped over an uneven substrate, as it intersects three bedding planes. There is no evidence of any object over which it could have been draped. No burrow trace, lining, or scratch marks are preserved. No other specimens of Phacops in this position have been reported.

scholarly journals Foraminiferal Analysis of the Late Miocene- Early Pleistocene Mangaopari Mudstone, South Wairarapa, New Zealand

2021 ◽  
Author(s):  
◽  
Shelby Stoneburner
Keyword(s):  
New Zealand ◽  
Late Miocene ◽  
Depositional Environment ◽  
Early Pleistocene ◽  
Tectonic Event ◽  
Early Pliocene ◽  
Two Samples ◽  
Different Parts ◽  
Medium Silt

<p>The foraminiferal content of thirty-two samples from the late Miocene-early Pleistocene Mangaopari Mudstone within the southern Wairarapa region have been examined with the aim of determining the age and depositional environment of the unit. In particular the study addressed whether or not there were glacioeustatic cycles present in the unit. Integrating foraminiferal faunal distributions and sedimentological analysis provided geological, paleoclimactic, and paleoceanographic evidence to aid in the reconstruction of the paleoenvironment. The data was then compared with conclusions from previous studies.  The section was divided into two different parts (upper and lower) based on changes in foraminiferal assemblages and grainsize distributions. The age and depositional environment of the Mudstone is suggested by the presence of several genera and species of foraminifera which is supported by grainsize analysis. The presence of Martinottiella communis and Karreriella cylindrica between 0-157.1m stratigraphically suggest that accumulation began in bathyal conditions at depths greater than 400m between. This is supported by grainsize analysis which indicates a medium silt with a high percent mud content ranging from 91.5-100%. This demonstrates deposition beginning in the late Miocene-early Pliocene at bathyal depths greater than 400m. The upper part of the mudstone (157.6-216.3) illustrates a regressive sequence with a distinctive shift to a much shallower depositional environment at outermost shelfal depths likely of 150-200m. This is represented with the presence of Truncorotalia sp. and Zygochlamys delicatula. Grainsize also support this discovery with a shift to very fine sandy silts with a percent mud content ranging from 83-93%.  Previous findings conclude that this distinctive shift was caused by glacioeustatic cycles yet our data do not correlate with our glacioeustatic findings. Therefore, this shift is believed to be triggered by a tectonic event.</p>

scholarly journals Experimental study on the cracking process of layered shale using X-ray microCT

2017 ◽  
Vol 36 (2) ◽  
pp. 297-313 ◽  
Author(s):  
Shengxin Liu ◽  
Zongxiu Wang ◽  
Linyan Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Compressive Loading ◽  
Bedding Plane ◽  
Fracture Networks ◽  
Microscopy Imaging ◽  
X Ray ◽  
Bedding Planes ◽  
Cracking Process ◽  
Scanning Electron

The cracking process in Longmaxi formation shale was experimentally studied during uniaxial compressive loading. Both the evolution of the three-dimensional fracture network and the micromechanics of failure in the layered shale were examined as a function of the inclination angle of the bedding plane. To visualize the cracking process, the test devices presented here used an industrial X-ray CT scanner that enabled scanning during the uniaxial compressive loading. Scanning electron microscopy and environmental scanning electron microscopy imaging techniques were used to observe the microscopic characteristics of fractured surfaces of failed specimens. The combination of these observations clearly illustrated the micromechanics of the failure process in the anisotropic shale. The experimental results suggest that the cracking process could be divided into two stages under uniaxial loading, and the microstructures and bedding planes of the shale played an important role in the cracking process of layered shale. In the first stage of deformation, the cracking mainly occurred as smaller microcracks (such as intergranular, microcracks), and the propagation of the newly formed microcracks was controlled by the bedding plane of the shale specimen. The microscopic imaging study showed that the microscopic damage was mainly dominated by microtensile fractures under uniaxial compression. In the second stage, with the increase in loading, the extensive development and coalescence of the microcracks led to the formation of complex fracture networks. The complexity of the fracture networks was related to the microstructure of the sample. The coalescence of the microcracks could be divided into three levels in the spatial scale, and the coalescence patterns included both tensile and shear patterns.

scholarly journals Evidence for surface sediment remobilization by earthquakes in the Nankai forearc region from sedimentary records

2018 ◽  
Vol 477 (1) ◽  
pp. 37-45 ◽  
Author(s):  
Natsumi Okutsu ◽  
Juichiro Ashi ◽  
Asuka Yamaguchi ◽  
Tomohisa Irino ◽  
Ken Ikehara ◽  
...  
Keyword(s):  
Surface Sediment ◽  
Fine Sand ◽  
Turbidity Currents ◽  
Silty Clay ◽  
Submarine Landslides ◽  
Sedimentary Processes ◽  
Piston Core ◽  
Radiocarbon Age ◽  
Sedimentary Records ◽  
Forearc Region

AbstractSubmarine landslides triggered by earthquakes can generate turbidity currents. Recently, several studies have reported that the remobilization of surface sediment triggered by earthquakes can also generate turbidity currents. Such sedimentary processes may be influenced by sediment characteristics, seafloor morphology and seismic motions. Here, we verify surface sediment remobilization using sedimentary records from the Nankai forearc region, SW Japan. We collected multi-core and piston core samples from a small confined basin, mainly composed of silty clay or very fine sand. Radiocaesium measurements of the multi-core show consistently high values in the upper 17 cm and low values below this depth. Rapid sediment deposition after 1950 is assumed, and the most likely cause is the 2004 off the Kii Peninsula earthquake. Based on calculations using bathymetric maps and palaeocurrent data, settlement of the upper 17 cm can be explained by redeposition of the surface (c. 1 cm) slope sediment around the basin. Muddy turbidites are also identified in the piston core. The gap in radiocarbon age observed around 2.0 m bsf (metres below seafloor) implies similar sedimentary processes. Our study represents the first examination of surficial remobilization from sedimentary cores in the Nankai forearc region.

Manuring of potatoes on fen silt soils in Holland, Lincolnshire

1973 ◽  
Vol 80 (2) ◽  
pp. 269-281 ◽  
Author(s):  
C. Berryman ◽  
T. Batey ◽  
T. H. Caldwell ◽  
D. A. Boyd
Keyword(s):  
Crop Production ◽  
Soil Analysis ◽  
Organic Matter Content ◽  
Fine Sand ◽  
Coarse Sand ◽  
Matter Content ◽  
Silty Clay ◽  
Alluvial Deposits ◽  
K Fertilizer ◽  
P Fertilizer

SummaryThe fen silts bordering the Wash are among the most important soils for crop production in eastern England. Derived from marine alluvial deposits occurring naturally or as a result of reclamation, they form deep almost stoneless soils containing little coarse sand but much fine sand and silt.Seven textural classes, ranging from loamy fine sand to silty clay, can be distinguished, but these can be grouped into (1) light silts, typically deep very fine sandy loams with a large available water-holding capacity but weakly developed structure; (2) medium silts, silty loams; and (3) heavy silts, silt loams or silty clay loams, less porous and more retentive of moisture than the light silts.Formerly under grass, the silts were at first capable of growing good crops of potatoes with P fertilizer alone, but as their organic-matter content decreased, potatoes became increasingly responsive to N.In 18 potato manurial experiments on silt soils in Holland, Lincolnshire, done between 1953 and 1963, the mean response to N was much larger than on most English soils, but response differed greatly from site to site and year to year; in most trials N was particularly effective in increasing tuber size and yield of ware. With long-continued use of P fertilizer, residues have accumulated and, particularly on light and medium silts, responses were quite small and differed little between sites; P tended to increase tuber numbers, and so to decrease ware percentage. Most silt soils are rich in K, and only small responses to K fertilizer can be expected, but on a few sites on the light silts, identified by soil analysis as being comparatively poor in K, potatoes responded well. Using these experimental results, recommendations are given for the manuring of potatoes on silt soils.Cooking tests showed little consistent effect of manurial treatment on the amount or degree of tuber blackening.

Surface-mine Rehabilitation in the American West

1976 ◽  
Vol 3 (3) ◽  
pp. 179-183 ◽  
Author(s):  
C. Wayne Cook
Keyword(s):  
Three Dimensional ◽  
Life Forms ◽  
Climatic Conditions ◽  
Wildlife Habitat ◽  
Silty Clay ◽  
Topographic Map ◽  
Rehabilitation Plan ◽  
Complete Restoration ◽  
Method Of Planting ◽  
Selection Of Species

The rehabilitation plan for a surface-mined area should be in detail and prepared as part of the mining plan. The area to be disturbed should be identified as to its vegetation-types and potential for rapid and complete restoration. The rehabilitation plan should show, by means of topographic maps or three-dimensional maps prepared before the advent of mining, the general lay of the terrain and the reconfiguration after mining. Such maps will indicate how soil-slope regulations are being met, how aesthetic acceptability can be evaluated, and how ecological response-units for revegetation can be characterized.In order to prepare a detailed revegetation plan before mining, the following maps and information are needed: (1) a topographic map, (2) a soil-series map, (3) a vegetation-cover map, and details concerning (4) the wildlife that inhabits the area, (5) the prevailing climatic conditions such as wind and the amount and form of precipitation, and (6) the character of each geological stratum that lies above the coal-seams or whatever is to be mined—including its structure, depth, and possible toxicity.The detailed revegetation plan should identify where the topsoil or other plant-growth medium will be obtained, so that it can be stockpiled to be redistributed over the spoil material. Fine sandy loams, silty clay soils, and soils that are high in toxic elements or low in organic matter, should be avoided. It is recommended that topsoil material be redistributed over the spoil material to a minimum depth of 18 to 24 inches (457 to 610 mm), in order to furnish adequate depth for root concentration and for storage of reserve moisture following the spring snow-melt. The seedbed should be firm and free from competitive weeds. On harsh sites, water-holding basins or contour trenches should be constructed.The method of seeding should include either drilling or broadcasting the seed, with due provisions for seed coverage by soil, and the addition of fertilizers and mulches where appropriate. The selection of species should include both native and introduced species that are adapted to the site. A wide diversity of life-forms and species should be included, to ensure stabilization of the area and furnish the wildlife habitat requirements. The season of seeding should be the period prior to the incidence of the most dependable precipitation in the area. The quantities of different seeds in the mixture and the overall amount employed will vary from site to site and with the method of planting. Generally speaking, poorer sites require more seed than favourable sites, and broadcasting requires about twice as much seed as does drilling.Direct on-site costs for reclamation may vary from $250 to as much as $2,750 per acre (0.405 ha), depending upon saving and distributing the topsoil, shaping the overburden, seed-bed preparation, planting, fertilization, drainage control, mulching, and irrigation.

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