Recognition of Paleogastroliths from the Lower Cretaceous Cedar Mountain Formation, Utah using a Scanning Electron Microscope

Ichnos ◽  
2008 ◽  
Vol 15 (2) ◽  
pp. 72-77 ◽  
Author(s):  
Rebecca L. Schmeisser ◽  
Tim P. Flood
Clay Minerals ◽  
1982 ◽  
Vol 17 (2) ◽  
pp. 255-258 ◽  
Author(s):  
R. H. S. Robertson ◽  
D. Tessier ◽  
J. L. White

It is generally agreed that the English mid-Jurassic and Lower Cretaceous fuller's earths were derived from volcanic ash. In the Lower Cretaceous fuller's earth of Woburn, Kerr (1932) recognized partially decomposed relics of shards in a matrix of montmorillonite, and Grim (1933, 1935) described montmorillonite pseudomorphs after glass fragments in the Bath fuller's earth of Bathonian age. Jeans et al. (1977) published twenty-two SEM pictures of pyroclasts, including sanidine, sphene, trachytic pumice, and a basaltic glass fragment. Photomicrographs of the Lower Cretaceous fuller's earth show shard relicts ranging in length from 0·8-1·26 mm (median ∼1·12 mm) and in thickness from 5-15µm (Jeans et al., 1977, fig. 14a). However, much remains obscure about the shape, size and mode of packing of the argillized vitric particles which make up the bulk of fuller's earths. This note describes the texture of an English fuller's earth which was freeze-fractured (Tessier, 1978), prior to examination with a scanning electron microscope.


2016 ◽  
Vol 86 (6) ◽  
pp. 734-748 ◽  
Author(s):  
James O. Buckman ◽  
Patrick W.M. Corbett ◽  
Lauren Mitchell

Abstract: Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique that can be induced through partial surface charge suppression of uncoated nonconductive samples, imaged with a suitable detector such as a gaseous secondary electron detector (GSED). The technique commonly produces results similar in style to that of SEM-cathodoluminescence (SEM-CL), providing information on zoning, twinning, annealed fractures, and subtle chemical changes. The current work outlines an example from a Brazilian Lower Cretaceous coquina limestone, in which both optical and SEM-CL imaging produces a limited response from much of the sample. Backscattered electron (BSE) imaging typically suggests only a hint of the cement present, whereas CCI clearly displays a rich and varied cement stratigraphy. The earliest cement displays strong CCI, but appears mainly dark under CL imaging conditions (SEM-CL and optical CL). Later-stage manganese-“enriched” carbonate cement displays luminescence with both optical and SEM-CL, as well as a CCI response. Therefore CCI can provide additional information on cement zonation in an area where CL cannot.


Author(s):  
R. E. Ferrell ◽  
G. G. Paulson

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.


Author(s):  
C. T. Nightingale ◽  
S. E. Summers ◽  
T. P. Turnbull

The ease of operation of the scanning electron microscope has insured its wide application in medicine and industry. The micrographs are pictorial representations of surface topography obtained directly from the specimen. The need to replicate is eliminated. The great depth of field and the high resolving power provide far more information than light microscopy.


Author(s):  
K. Shibatomi ◽  
T. Yamanoto ◽  
H. Koike

In the observation of a thick specimen by means of a transmission electron microscope, the intensity of electrons passing through the objective lens aperture is greatly reduced. So that the image is almost invisible. In addition to this fact, it have been reported that a chromatic aberration causes the deterioration of the image contrast rather than that of the resolution. The scanning electron microscope is, however, capable of electrically amplifying the signal of the decreasing intensity, and also free from a chromatic aberration so that the deterioration of the image contrast due to the aberration can be prevented. The electrical improvement of the image quality can be carried out by using the fascionating features of the SEM, that is, the amplification of a weak in-put signal forming the image and the descriminating action of the heigh level signal of the background. This paper reports some of the experimental results about the thickness dependence of the observability and quality of the image in the case of the transmission SEM.


Author(s):  
S. Takashima ◽  
H. Hashimoto ◽  
S. Kimoto

The resolution of a conventional transmission electron microscope (TEM) deteriorates as the specimen thickness increases, because chromatic aberration of the objective lens is caused by the energy loss of electrons). In the case of a scanning electron microscope (SEM), chromatic aberration does not exist as the restrictive factor for the resolution of the transmitted electron image, for the SEM has no imageforming lens. It is not sure, however, that the equal resolution to the probe diameter can be obtained in the case of a thick specimen. To study the relation between the specimen thickness and the resolution of the trans-mitted electron image obtained by the SEM, the following experiment was carried out.


Author(s):  
R. F. Schneidmiller ◽  
W. F. Thrower ◽  
C. Ang

Solid state materials in the form of thin films have found increasing structural and electronic applications. Among the multitude of thin film deposition techniques, the radio frequency induced plasma sputtering has gained considerable utilization in recent years through advances in equipment design and process improvement, as well as the discovery of the versatility of the process to control film properties. In our laboratory we have used the scanning electron microscope extensively in the direct and indirect characterization of sputtered films for correlation with their physical and electrical properties.Scanning electron microscopy is a powerful tool for the examination of surfaces of solids and for the failure analysis of structural components and microelectronic devices.


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