The age and structural setting of limestones and basalts on the Main Ring Fault in southeast Rhum

AbstractIn southeast Rhum, a Mesozoic/Tertiary sequence is preserved as a fault-bounded and rotated wedge. This is juxtaposed between Precambrian rocks (Torridonian sediments and Lewisian gneiss) and caught up in the complex structure of the Tertiary Main Ring Fault (MRF), which shows three distinct phases of movement. The Mesozoic rocks comprise fossiliferous limestone, sandstone and shale, which show differing degrees of thermal metamorphism depending on their relationships to the Layered Complex. On the basis of faunal and lithological evidence the Mesozoic sediments have been correlated with the Lower Liassic Broadford Beds. The Rhum sediments are overlain by sheared Tertiary basalts, the contact between them probably representing the original landscape unconformity. The presence of these younger strata caught up along the MRF provides crucial evidence for a major phase of central subsidence in the early history of the Rhum Tertiary volcanic centre.

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A Discussion on the evolution of the Precambrian crust - Introductory remarks

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1973.0002 ◽

1973 ◽

Vol 273 (1235) ◽

pp. 316-316 ◽

Cited By ~ 2

Keyword(s):

Early History ◽

Geological Time ◽

Precambrian Rocks ◽

The Past ◽

Geological Processes ◽

The Earth ◽

Large Numbers ◽

The World ◽

History Of

The realization that the behaviour of the Earth has changed radically during geological time has come about largely in the last decade. This development, which constitutes one of the major advances in geological thinking, results from the study of Precambrian phenomena in many parts of the world and in particular from the work of a small number of geochronologists. In the last ten years as large numbers of unfossiliferous Precambrian rocks have been dated, it has become clear that the nature of geological processes has varied throughout geological time and that one of the cardinal doctrines of geology - the concept that the present is the key to the past — could not be applied to the study of the early history of the Earth.

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Early history of the Fermilab Main Ring

10.2172/15020142 ◽

1983 ◽

Author(s):

E. Malamud

Keyword(s):

Early History ◽

Main Ring ◽

History Of

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The early igneous and tectonic history of the Rhum Tertiary Volcanic Centre

Geological Magazine ◽

10.1017/s0016756800035378 ◽

1985 ◽

Vol 122 (5) ◽

pp. 451-457 ◽

Cited By ~ 17

Author(s):

C. H. Emeleus ◽

W. J. Wadsworth ◽

N. J. Smith

Keyword(s):

Fault System ◽

Volcanic Centre ◽

Acid Magma ◽

The Core ◽

Tectonic History ◽

Early Tertiary ◽

Main Ring ◽

Igneous Activity ◽

History Of ◽

Structural Levels

AbstractEarly Tertiary igneous activity on Rhum was preceded by doming and the formation of a major arcuate fault system, the Main Ring Fault (MRF), within which Lewisian gneisses, Torridonian sediments and younger rocks were uplifted by as much as 2 km. Doming and uplift are attributed to the diapiric rise of acid magma which ultimately formed the granophyres and felsites of Rhum. Felsite emplacement was accompanied and immediately preceded by the formation of explosion breccias and tuffisites. This phase involves massive gas escape along the MRF fractures; it marked a period of major subsidence within the MRF during which fossiliferous Jurassic sediments and relics of Tertiary lava flows were brought to low structural levels within the MRF. Finally, a further period of uplift, again of about 2 km, took place once more bringing gneisses and basal Torridonian sediments within the MRF to high structural levels. The driving force for this last phase of uplift may have been provided by a further uprise of acid magma or, more realistically, may have been directly connected with emplacement of layered ultrabasic rocks which now form the core of the Rhum centre.

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Some early history of replica techniques for electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130018 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1076-1077

Author(s):

Robert M. Fisher

Keyword(s):

Thin Film ◽

Electron Microscopy ◽

Optical Microscope ◽

Early History ◽

Bulk Materials ◽

Thin Sections ◽

Transmission Electron ◽

Reflected Light ◽

History Of ◽

Electron Microscopes

By 1940, a half dozen or so commercial or home-built transmission electron microscopes were in use for studies of the ultrastructure of matter. These operated at 30-60 kV and most pioneering microscopists were preoccupied with their search for electron transparent substrates to support dispersions of particulates or bacteria for TEM examination and did not contemplate studies of bulk materials. Metallurgist H. Mahl and other physical scientists, accustomed to examining etched, deformed or machined specimens by reflected light in the optical microscope, were also highly motivated to capitalize on the superior resolution of the electron microscope. Mahl originated several methods of preparing thin oxide or lacquer impressions of surfaces that were transparent in his 50 kV TEM. The utility of replication was recognized immediately and many variations on the theme, including two-step negative-positive replicas, soon appeared. Intense development of replica techniques slowed after 1955 but important advances still occur. The availability of 100 kV instruments, advent of thin film methods for metals and ceramics and microtoming of thin sections for biological specimens largely eliminated any need to resort to replicas.

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