The major pre-Mississippian unconformity in Rock Canyon, central Wasatch Range, Utah

2014 ◽  
Vol 1 ◽  
pp. 1-5 ◽  
Author(s):  
David Leigh Clark ◽  
Drew D. Derenthal ◽  
Bart J. Kowallis ◽  
Scott M. Ritter
Keyword(s):  
Upper Devonian ◽  
Large Size ◽  
Preliminary Work ◽  
Mississippian Rocks

In central Utah, the major pre-Mississippian unconformity is fairly well understood at most of the localities where it is recognized. However, the unconformity is more enigmatic in Rock Canyon of the central Wasatch Range. At this locality, dolomitization of most pre-Mississippian rocks obscures stratigraphic identification of Devonian and older units. The absence of any identifiable angular relationship further complicates resolution. Because of this, both identification of the stratigraphic level of the unconformity and, consequently, its magnitude remain controversial. Large-size dolomite samples taken in Rock Canyon at closely spaced intervals for the 3.6-m directly below definite Upper Devonian rocks yield microfossils, including conodonts, in the uppermost 1.6-m of that interval that indicate no unconformity exists between the Cambrian Maxfield Limestone and the Upper Devonian-Lower Mississippian Fitchville Dolomite at the horizon previously identified as unconformable. Rather, an unknown thickness of dolomitized Upper Devonian Pinyon Peak Formation and probable older rock (possibly Bluebell Dolomite and Victoria Formation) occurs between the top of definite Maxfield and base of the Fitchville. The identification of the unconformity horizon remains unknown. Our preliminary work outlines a promising procedure for future understanding of the magnitude and stratigraphic level of the unconformity.

The major pre-Mississippian unconformity in Rock Canyon, central Wasatch Range, Utah

2014 ◽  
Vol 1 ◽  
pp. 1-5
Author(s):  
David Clark ◽  
Drew Derenthal ◽  
Bart Kowallis ◽  
Scott Ritter
Keyword(s):  
Upper Devonian ◽  
Large Size ◽  
Preliminary Work ◽  
Mississippian Rocks

In central Utah, the major pre-Mississippian unconformity is fairly well understood at most of the localities where it is recognized. However, the unconformity is more enigmatic in Rock Canyon of the central Wasatch Range. At this locality, dolomitization of most pre-Mississippian rocks obscures stratigraphic identification of Devonian and older units. The absence of any identifiable angular relationship further complicates resolution. Because of this, both identification of the stratigraphic level of the unconformity and, consequently, its magnitude remain controversial. Large-size dolomite samples taken in Rock Canyon at closely spaced intervals for the 3.6-m directly below definite Upper Devonian rocks yield microfossils, including conodonts, in the uppermost 1.6-m of that interval that indicate no unconformity exists between the Cambrian Maxfield Limestone and the Upper Devonian-Lower Mississippian Fitchville Dolomite at the horizon previously identified as unconformable. Rather, an unknown thickness of dolomitized Upper Devonian Pinyon Peak Formation and probable older rock (possibly Bluebell Dolomite and Victoria Formation) occurs between the top of definite Maxfield and base of the Fitchville. The identification of the unconformity horizon remains unknown. Our preliminary work outlines a promising procedure for future understanding of the magnitude and stratigraphic level of the unconformity.

scholarly journals Enigmatic encrusting fossils from the Upper Devonian of Russia: probable Rothpletzella microproblematica preserved in three dimensions

2018 ◽  
Author(s):  
Michał Zatoń ◽  
Emilia Jarochowska
Keyword(s):  
Low Ph ◽  
Bacterial Activity ◽  
Upper Devonian ◽  
Three Dimensions ◽  
Thin Sections ◽  
Central Devonian Field ◽  
Large Size ◽  
First Time ◽  
Hard Substrates ◽  
Animal Taxon

Intriguing microfossils encrusting certain Upper Devonian brachiopod shells from the Central Devonian Field, Russia, are reported for the first time. The fossils are pyritized, have fan-shaped morphologies and are formed by tightly-packed branches which divide dichotomously at different points in their development. The organisms preserved grew horizontally on shelly substrates. Comparisons with similar fossils known from the literature indicate that they do not represent any animal taxon commonly encrusting hard substrates. Instead, the morphology, organization and growth mode of these fossils are most similar to microfossils known under the name Rothpletzella, which so far have only been known from thin sections. Rothpletzella is a problematicum for which algal affinities have been proposed. The preserved branches of the fossils described here are too large for cyanobacterial cells. Their large size suggests their placement, along with other described Rothpletzella fossils, within the green algae order Bryopsidales. It is suggested that originally, these organisms possessed thalli encased within a thin, delicate calcified sheath. After burial the thalli underwent pyritization via sulphate reduction mediated by bacterial activity within low pH, dysoxic microenvironment, and their sheath dissolved. As three-dimensionally preserved, these algae provide a new, previously unrecognized, component within the Devonian encrusting communities.

Upper Devonian miospores from the Escuminac Formation, eastern Québec, Canada

1970 ◽  
Vol 7 (1) ◽  
pp. 29-45 ◽  
Author(s):  
Wayne W. Brideaux ◽  
Norman W. Radforth
Keyword(s):  
Middle Devonian ◽  
Russian Platform ◽  
Upper Devonian ◽  
New Combinations ◽  
Lower Carboniferous ◽  
The Third ◽  
Large Size ◽  
Assem Blages ◽  
Small Spore ◽  
Orcadian Basin

Miospores of early Frasnian age are described from the third unit of the Escuminac Formation in eastern Québec, Canada. The assemblage comprises 34 species, including 8 species proposed as new, 2 new combinations, and 12 sparsely represented forms not considered synonymous with previously described species.The assemblage is most closely comparable to a Middle Devonian assemblage from the Orcadian Basin, Scotland. Similarities are also noted with European and Russian assemblages, particularly from the Eifelian–Givetian of the Russian Platform. Except for five long-ranging species, elements of Lower Carboniferous assemblages are lacking. Evidence suggests a transitional nature for this Escuminac assemblage. Miospores of relatively large size, a feature of Middle Devonian assemblages, are present. Marked differentiation of large and small spore types, found in several other Upper Devonian assem blages is absent. Apiculate and anchor-spined species dominate the Escuminac assemblage.

Coherency loss in γ' precipitates in nickel-base superalloy

1983 ◽  
Vol 41 ◽  
pp. 244-245
Author(s):  
R. A. Ricks ◽  
Angus J. Porter
Keyword(s):  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Nickel Base Superalloy ◽  
Large Size ◽  
The Matrix ◽  
Nimonic 80A ◽  
Interfacial Dislocations ◽  
Nickel Base ◽  
Coherency Loss ◽  
Nimonic 115

During a recent investigation concerning the growth of γ' precipitates in nickel-base superalloys it was observed that the sign of the lattice mismatch between the coherent particles and the matrix (γ) was important in determining the ease with which matrix dislocations could be incorporated into the interface to relieve coherency strains. Thus alloys with a negative misfit (ie. the γ' lattice parameter was smaller than the matrix) could lose coherency easily and γ/γ' interfaces would exhibit regularly spaced networks of dislocations, as shown in figure 1 for the case of Nimonic 115 (misfit = -0.15%). In contrast, γ' particles in alloys with a positive misfit could grow to a large size and not show any such dislocation arrangements in the interface, thus indicating that coherency had not been lost. Figure 2 depicts a large γ' precipitate in Nimonic 80A (misfit = +0.32%) showing few interfacial dislocations.

Automatic analysis of Kikuchi diffraction patterns

1994 ◽  
Vol 52 ◽  
pp. 900-901
Author(s):  
H. Weiland ◽  
D. P. Field
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Spatial Resolution ◽  
Relevant Information ◽  
Crystalline Materials ◽  
Large Size ◽  
Transmission Electron ◽  
New Type ◽  
Diffraction Patterns ◽  
Orientation Determination

Recent advances in the automatic indexing of backscatter Kikuchi diffraction patterns on the scanning electron microscope (SEM) has resulted in the development of a new type of microscopy. The ability to obtain statistically relevant information on the spatial distribution of crystallite orientations is giving rise to new insight into polycrystalline microstructures and their relation to materials properties. A limitation of the technique in the SEM is that the spatial resolution of the measurement is restricted by the relatively large size of the electron beam in relation to various microstructural features. Typically the spatial resolution in the SEM is limited to about half a micron or greater. Heavily worked structures exhibit microstructural features much finer than this and require resolution on the order of nanometers for accurate characterization. Transmission electron microscope (TEM) techniques offer sufficient resolution to investigate heavily worked crystalline materials.Crystal lattice orientation determination from Kikuchi diffraction patterns in the TEM (Figure 1) requires knowledge of the relative positions of at least three non-parallel Kikuchi line pairs in relation to the crystallite and the electron beam.

Immunoprobe localization in mammalian embryos

1990 ◽  
Vol 48 (3) ◽  
pp. 32-33
Author(s):  
Patricia G. Calarco ◽  
Margaret C. Siebert
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Thin Sections ◽  
Relative Lack ◽  
Large Size ◽  
Mammalian Embryos ◽  
Antigen Localization ◽  
Difficult Challenge ◽  
Lowicryl K4m ◽  
Fertilized Egg

Visualization of preimplantation mammalian embryos by electron microscopy is difficult due to the large size of the ircells, their relative lack of internal structure, and their highly hydrated cytoplasm. For example, the fertilized egg of the mouse is a single cell of approximately 75μ in diameter with little organized cytoskelet on and apaucity ofor ganelles such as endoplasmic reticulum (ER) and Golgi material. Thus, techniques that work well on tissues or cell lines are often not adaptable to embryos at either the LM or EM level.Over several years we have perfected techniques for visualization of mammalian embryos by LM and TEM, SEM and for the pre-embedding localization of antigens. Post-embedding antigenlocalization in thin sections of mouse oocytes and embryos has presented a more difficult challenge and has been explored in LR White, LR Gold, soft EPON (after etching of sections), and Lowicryl K4M. To date, antigen localization has only been achieved in Lowicryl-embedded material, although even with polymerization at-40°C, the small ER vesicles characteristic of embryos are unrecognizable.

Vibration Isolator System for Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 182-183
Author(s):  
K. Ohi ◽  
M. Mizuno ◽  
T. Kasai ◽  
Y. Ohkura ◽  
K. Mizuno ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Fields ◽  
Environmental Conditions ◽  
Vibration Isolator ◽  
Air Conditioners ◽  
Vibration Isolators ◽  
Large Size ◽  
Electron Microscopes

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.

Sign in / Sign up

Export Citation Format

Share Document