Geology Commons^™

Geology Of The Mafic/Ultramafic Transition, Table Mountain, Western Newfoundland, Suzanne O'Connell

Geology Theses and Dissertations

A thin (<200 m.) mafic suite and well developed mafic/ultramafic transition zone are exposed above a flat lying peridotite contact on northwestern Table Mountain. The igneous layering and sedimentary features indicate mineral deposition under conditions which promoted adcumulate growth, were capable of minor transport, and were subjected to at least minor tectonic activity during consolidation. Feldspathic,. mafic, and ultramafic dikes and veins cross-cut the layering. Microscopic futures indicate deformation at elevated temperature and/or low strain rates. Deformation is best developed within the transition zone, but cataclastic zones are most common in the hornblende gabbros. Orientations of layering, foliation, and lineation indicate a variable mafic/ultramafic transition and macroscopic folding. Geometric analysis indicates three distinct fold axis orientations: an east-west horizontal fold axis, a northeast trending modestly plunging axis, and a vertical though poorly defined axis. Such features demonstrate that an apparently simple contact relationship may be extremely complex. This has important implications for ocean floor accretion. The relatively simple ocean floor seismic stratigraphy masks very complex petrological and structural processes. Such processes may involve deposition in an actively convecting magma chamber with a differentially subsiding wedge (Dewey and Kidd, 1977), in which folding occurs in response to the steepening angle between the cumulate banding and the base of the magma chamber. The instability is enhanced by the different accumulation rates and densities of the minerals involved. The lineation may originally be a sedimentary feature indicative of transport direction from the convection cell, and perpendicular to the compressive stress which produced. the folding. The different orientations of lineations and fold axes could be produced by rotation of the ocean crustal blocks during lateral transport along the ocean floor and/or obduction. Further detailed study of ophiolite complexes will continue to shed light upon the nature and development of oceanic crust.

Petrology And Mineral Chemistry Of Some Jan Mayen Volcanics, Carla A. White

Geology Theses and Dissertations

The island of Jan Mayen is the northernmost active volcano on the Mid-Atlantic Ridge. The rocks of Jan Mayen belong to the potassic series of the alkaline rocks and appear to belong to the straddle type association. The ankaramites and alkali olivine basalts are characterized by the presence of large xenocrysts of rimmed chromium diopside, titaniferous salite, olivine (Fo83 to Fo88), magnetite and sometimes plagioclase (bytownite rimmed by labradorite). Phenocrysts of olivine (Fo74) and plagioclase (andesine) are present in several rocks. These and phenocrysts lie in a matrix composed of` titaniferous salite, olivine (Fo58), plagioclase (andesine), magnetite, biotite and sometimes …

Geology Of The Lucea Inlier, Western Jamaica, Jack Grippi

Geology Theses and Dissertations

The Lucea Inlier exposes a Santonian to Campanian 4 km + thick sequence of shale-siltstone, resedimented volcaniclastics, lenses of shallow-water limestone, micritic limestone, pebbly mudstone and sandy pebble to boulder conglomerate. Clastics were deposited by a variety of gravity flow mechanisms. Petrographically sandstones are lithic or feldspathic arenites and contain only very small amounts of detrital quartz. Structurally the inlier is characterized by simple, open, east-west trending folds. A spaced, vertical axial-planar cleavage is developed in shales and fine siltstones. Two major east-west trending left-lateral fault zones, the Fat Hog Quarter and Maryland faults, cut the inlier into three blocks, …

Petrology Of The Oceanographer Fracture Zone (35ºn35ºw), Tsugio Shibata

Geology Theses and Dissertations

During a geological and geophysical survey of the Oceanographer Fracture Zone (35°N, 35°W), seventeen dredge hauls containing a variety of rocks were obtained. Petrographic study shows that these rock samples can be classified into six main rock types: fresh basalt, weathered basalt, metabasalt, gabbro, metagabbro, and serpentinite. Most of the dredge hauls were positioned on the steep, southern wall of the fracture zone, and an inference from the dredging results suggests that basalt is the most abundant rock type which outcrops at the junction between the rift valley and the fracture zone; however, as we move away from the junction, …

A Study Of Some Petrologic And Structural Aspects Of The East Dover Ultramafic Bodies, South Central Vermont, Mark Allen Hoffman

Geology Theses and Dissertations

INTRODUCTION (pp.1-4)

Mineralogical, textural and chemical changes of ultramafic rocks in response to regional deformation and metamorphism are, at best, imperfectly known (Miyashiro, 1973, p. 30). In Vermont, which has an extremely prominent and well-exposed belt of ultramafics (fig. 1), investigation of these rocks has largely been directed toward such processes as serpentinization, steatitization, and the formation of metasomatic zones at the contacts with country rocks. With few exceptions, there is a lack of detailed descriptions of regional metamorphic textures, mineralogy, and structures developed in the Vermont ultramafic rocks. It is the main purpose of this thesis to describe the …

Structural Studies In The Mafic And Ultramafic Rocks Of The Lewis Hills, Western Newfoundland, Jeffrey A. Karson

Geology Theses and Dissertations

Table of contents:
CHAPTER I. INTRODUCTION
CHAPTER II. REGIONAL GEOLOGY
CHAPTER III. THE LEWIS HILLS COMPARED TO THE NORTHERN AREAS OF THE BAY OF ISLAND COMPLEX
CHAPTER IV. PETROGRAPHY
CHAPTER V. STRUCTURAL GEOLOGY
CHAPTER VI. SUMMARY, CONCLUSIONS, AND SPECULATIONS
BIBLIOGRAPHY
APPENDIX I. CONTOURED STEREOGRAPHIC PROJECTIONS OF FOLIATIONS AND LINEATIONS IN THE HINES POND AREA

Petrography, Metamorphism, And Geochemistry Of The Bermeja Complex And Related Rocks In Southwestern Puerto Rico And Their Significance In The Evolution Of The Eastern Greater Antillian Island Arc, Victor J.B. Lee

Geology Theses and Dissertations

Chapter I. Introduction and previous work 1
Chapter II. Geological setting and the petrography of the igneous and metamorphic rocks from southwestern Puerto Rico 6
Chapter III. Metamorphism in southwestern Puerto Rico and relations to the Eastern Greater Antilles 46
Chapter IV. Geochemistry of the Bermeja complex 84
Chapter V. Secular compositional changes of the volcanic rocks in Puerto Rico and other islands in eastern West Indies and the significances of the Bermeja complex 179
Appendix A-E: Petrographic data of the analyzed samples of the Bermeja complex 222
References cited 231

The Bedrock Geology Of The Southwest Part Of The Kachess Lake Quadrangle, Washington, David Carl Lofgren

Dissertations and Theses

The southwestern part of the Kachess Lake quadrangle lies between Lakes Cle Elum and Kachess, on the east flank of the central Cascade Range of Washington. The region lies between the North and South Cascade petrologic provinces, and includes rocks typical of each. Pre-Tertiary Easton Schist (called the Shuksan Suite farther north), and the Late Cretaceous-Paleocene Swauk Formation occur widely in the North Cascades, while the Tertiary Silver Pass Volcanics and Teanaway Basalt are typical of South Cascade volcanic sequences. Diabasic dikes of the Teanaway dike swarm occur throughout the vicinity.

The area is bounded on the west by a …

Petrology And Regional Relationships Of The Ordovician Kinnikinic Formation And Equivalents, Central And Southern Idaho, William Calvin James

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Kinnikinic Formation of central Idaho is a sedimentary unit consisting principally of orthoquartzite. From its maximum measured thickness of 2285 feet in the central Lemhi Range near Gilmore, Idaho, it thins westward to 376 feet at the type section and southward to 326 feet near Arco, Idaho. Northeast of the Lemhi Range it occurs only as erosional remnants, due to pre-Devonian erosion. Both the lower and upper contacts of the Kinnikinic Formation are disconformable.

The Kinnikinic Formation is light colored, predominately fine to medium grained, thin to medium bedded, and largely cemented by silica overgrowths. Some metamorphic recrystallization has …

Petrology And Geochemistry Of The Morrison Formation, Dinosaur Quarry Quadrangle, Utah, Sue Ann Bilbey

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Mineralogical and petrographic analyses of the upper Jurassic - lower Cretaceous units in the vicinity of the Dinosaur National Monument quarry near Jensen, Utah, have elucidated their characteristics and the locations of formational boundaries. The lower part of the Morrison Formation is distinguished by a decreased amount of illite and an increased amount of kaolinite. In contrast, the underlying Curtis Formation contains an approximately equal mixture of illite and kaolinite. The lower Salt Wash Member and the upper Brushy Basin Member of the Morrison are both lithologically and mineralogically identifiable in this area. Above the boundary between the two, kaolinite …

Petrology Of The Ordovician Swan Peak Formation, Southeastern Idaho And North-Central Utah, Warren J. Schulingkamp Ii

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Swan Peak Formation in southeastern Idaho and north-central Utah is a sedimentary unit consisting of orthoquartzite, sandstone, siltite, shale, and limestone. The formation is divisible into three members, and the lower two members each are divisible into two informal lithologic subunits.

The lower member consists of a lower subunit of gray, calcareous sandy siltite composed of subangular to subrounded quartz grains cemented by quartz overgrowths, calcite, or iron oxide, and an upper subunit of black shale with minor interbedded silty quartzose sandstone and biomicrite (limestone).

The middle member consists of a lower subunit of interbedded pale green shale and …

Petrology Of The Nemeiben Lake Ultramafic And Associated Nickel-Sulphide Deposits, Anantaramam Peddada

Geology Theses and Dissertations

The Nemeiben Lake ultramafic body is located in the center of Saskatchewan, Canada, within the Churchill Province of the Canadian Shield. The ultramafic rocks consist of serpentinites, partly serpentinized and uralitized pyroxenite, and unaltered pyroxenite. Associated sulphide mineralization is of disseminated, net texture, and fracture filling types. The ore minerals present are pyrrhotite, pentlandite, chalcopyrite, pyrite, marcasite, violarite, bravoite and native copper. The sulphides are considered to be initially of magmatic origin formed from a sulphide melt separated at a late stage during crystallization of the ultramafic rocks. Subsequent serpentinization has locally redistributed the ores.
Serpentinization in the Nemeiben Lake …

Origin Of The Mount Merino Chert And Shale, Middle Ordovician, Eastern New York State, Dorothy M. Lang

Geology Theses and Dissertations

Mount Merino Chert and Shale, Middle Ordovician, is one of the most siliceous units of the Taconic sequence (eastern New York and western Vermont); it is composed of interbedded shale, siliceous hale, argillite and chert. Non-clastic quartz — aggregates of quartz having a.mosaic or felted texture — predominates in all beds, except `shale. All siliceous beds are finely laminated; most laminae are distinguished from adjacent laminae by the texture of the quartz groundmass, and the amount of clastics, carbonates, chlorite and sulphides. Statistical comparison of the textures of the quartz aggregates which occur with the other mineral components suggests that …

A Detailed Economic Investigation Of Geochemical And Aeromagnetic Anomalies North Central Maine, W. F. Stickney, R. S. Young, L. A. Wing

Maine Collection

A Detailed Economic Investigation of Geochemical and Aeromagnetic Anomalies North Central Maine

W.F.Stickney, R.S.Young and L.A.Wing

Special Economic Series No.4, Maine Geological Survey, Department of Economic Development, Augusta, Maine (March 1965).

Contents: Foreword / Part I - Geology (W.F. Stickney) / Part II - Geophysics (R.S. Young) / Part III - Geochemistry (L.A. Wing) / References

Genetic Study Of Some Pyrrhotite Deposits Of Maine And New Brunswick, Dept. Of Development Of Industry And Commerce

Maine Collection

Genetic Study of Some Pyrrhotite Deposits of Maine and New Brunswick

by Robert S. Houston

Maine Geological Survey - Bulletin 7

Department of Development of Industry and Commerce, Augusta, Maine (January, 1956).

Contents: Abstract / Introduction / Field and Laboratory Studies / Regional Geography / Regional Geology / Pyrrhotite Deposits / Description of Individual Deposits / Literature Cited

Report Of The State Geologist 1953-1954, Maine Geological Survey

Maine Collection

Report of the State Geologist 1953-1954.

Maine Geological Survey - Maine Development Commission, Augusta, Maine - July 1955.

Contents: Joseph M. Trefethen -- Review of Maine Mineral Outlook / Henry W. Allen -- Limestone Investigations, 1953-54 / Wm.T. Forsyth -- Airbourne Magnetometer Survey in Eastern Maine / Gary M. Boone -- Petrology of the Farmington, Maine Area / Joseph M. Trefethen, Henry Allen, and Wm. T. Forsyth -- Scheelite Occurrences in Maine / Wm.T. Forsyth -- Beneficiation Tests on the Warren Sillimanite Gneiss / Wm. T. Forsyth -- Pyrrhotite Mineralization at Iron Hill, Gardiner, Maine / Joseph M. Trefethen -- …

Maine Geological Survey - Bulletin 6 : Pegmatites And Associated Rocks In The Newry Hill Area, Oxford County, Maine., Vincent E. Shainin, Louis F. Dellwig

Maine Collection

Maine Geological Survey - Bulletin 6 : Pegmatites and Associated Rocks in the Newry Hill Area, Oxford County, Maine.

Joseph M. Trefethen, State Geologist.

by Vincent E. Shainin, University of Maine and Louis F. Dellwig, U.S. Geological Survey.

Maine Development Commission, Augusta, Maine, 1955

Report Of The State Geologist 1951-1952, Maine Geological Survey

Maine Collection

Report of the State Geologist 1951-1952.

Maine Geological Survey - Maine Development Commission, Augusta, Maine - December, 1953.

Contents: Joseph M. Trefethen -- New England Mineral Resources / Henry Allen -- Progress Report of Limestone Survey, Knox County / Wm. Forsyth -- Mineralogical Variations of the Ellsworth Schist in Blue Hill, Maine / Lawrence A. Wing -- Preliminary Report on Eastern Maine Granites / Kern Jackson -- A Preliminary Report on the Geology of a Portion of the Rumford Quadrangle, Maine / Robert M. Zink -- Certain Aspects of the Ecology of Venus and Mya at Bunganuc and at Morgan …

Report Of The State Geologist 1947-1948, Maine Geological Survey

Maine Collection

Report of the State Geologist 1947-1948.

Maine Geological Survey - Maine Development Commission, Augusta, Maine - March 1949.

Contents: Activity of the Maine Geological Survey, 1947-48 / Joseph M. Trefethen -- Review of the Aroostook County Manganese Deposits / Joseph M. Trefethen -- Notes on Ground Water Conditions in Maine / Joseph M. Trefethen -- The Desert of Maine / Henry Allen and Elbert Pratt -- Reconnaissance Surveys of Limestones in Franklin County, Maine / Lawrence Wing and Arthur Dawson -- Preliminary Report on Asbestos and Associated Rocks of Northwestern Maine / Lawrence Goldthwait -- Clay Survey 1948 / Earl …

Petrology Of The Upper Marietta And Hundred Sandstones In Southeastern Ohio, Wayne Dudley Martin

Graduate Theses, Dissertations, and Problem Reports (ETD)

A petrographic study was made of two Lower Permian (Dunkard Series) sandstones in southeastern Ohio. The sandstone members with which the investigation was concerned are the Upper Marietta sandstone and the Hundred sandstone. The study was made in order to determine the origin of the sandstones and the practicability of applying geologic methods to the grindstone industry. The results of the study indicate that although some of the constituents of these sandstones were derived from igneous and sedimentary source rocks, a relatively large amount of material was derived from metamorphic rocks. The detritus was transported from the east and deposited …

Maine Geological Survey - Bulletin 3 : Petrology Of The Columbia Falls Quadrangle, Me., Ruth D. Terzaghi

Maine Collection

Maine Geological Survey - Bulletin 3 : Petrology of the Columbia Falls Quadrangle, Me.

Joseph M. Trefethen, State Geologist

by Ruth D. Terzaghi

Maine Development Commission, Augusta, Maine, March 1, 1946.

The Structure, Lithology And Genesis Of The Magnesian Series Of The Northwestern States, C. W. Hall

Journal of the Minnesota Academy of Science

No abstract provided.