Physical Sciences and Mathematics Commons^™

The Geology Of The Southern Part Of The North Arm Mountain Massif, Bay Of Islands Ophiolite Complex, Western Newfoundland With Application To Ophiolite Obduction And The Genesis Of The Plutonic Portions Of Oceanic Crust And Upper Mantle, John F. Casey

Geology Theses and Dissertations

The Bay of Islands Ophiolite Complex forms a discontinuous belt of highly allochthonous mafic and ultramafic massifs in southwestern Newfoundland. The North Arm Mountain Massif contains the only significant exposures of sedimentary rocks overlying the ophiolite and also contains the most extensive exposures of plutonic rocks in the Bay of Islands Complex. Mapping has shown that sedimentary rocks, here named the Crabb Brook Group, rest with a pronounced erosional unconformity on ophiolitic rocks. Lithologic,paleontologic, facies, structural, and tectonic relationships indicate that this Group was deposited on the back of the ophiolite allochthon as it was being obducted onto the early …

Saratoga: The Bubbles Of Reputation And Their Implications For An Embryonic Rift System In The Upper Hudson River Valley, James R. Young

Geology Theses and Dissertations

Carbonated, alkaline, saline waters occur over a wide area in the upper Hudson River Valley approaching 1,000 square miles. Through the sampling (spring and fall) of 39 locations, half of which were hitherto unsampled, the waters are shown to be a complexly mixed system with at least five major components.
They are:
1) a gaseous phase consisting primarily of CO2;
2) a fluid (containing the dissolved CO2) possibly analogous to a metamorphic brine whose major chemistry is HCO3>Na>Cl;
3) formational waters of variably low salinities which may be the end products of progressive dilution of Paleozoic connate brines …

Structural Geology Of The Fort Miller, Schuylerville And Portions Of The Schaghticoke 7½' Quadrangles, Eastern New York, And Its Implications In Taconic Geology; And Experimental And Theoretical Studies Of Solution Transfer In Deforming Heterogeneous Systems, William P. Bosworth

Geology Theses and Dissertations

Stratigraphies previously proposed for the Taconic sequence of southern Washington County, eastern New York, have incorrectly defined and positioned lower Cambrian black slate units. The proper sequence of Cambrian (?) through Cambrian lithologies is (terminology from Jacobi, 1977): Bomoseen green wacke, Truthville green slate, Browns Pond black slate, Mettawee purple and green slate, and West Castleton and Hatch Hill black slates. This and the entire Taconic sequence is conformable within the western Giddings Brook slice. The detailed lithostratigraphy reported by Jacobi (1977) and Rowley (1980) in northern Washington County can be followed at least some 45 kilometers to the south …

Petrography, Mineral Chemistry And Microstructures Of Gabbros From The Mid-Cayman Rise Spreading Center, Frieda L. Malcolm

Geology Theses and Dissertations

The suite of gabbroic rocks collected by the DSRV ALVIN in 1976 and 1977 from the walls of the Mid-Cayman Rise spreading center were studied in detail to provide the best available data on plutonic rocks sampled directly from the ocean floor. The rock types studied include variably deformed and altered gabbros, orthopyroxene gabbros, olivine gabbros and troctolites, and a few amphibolites. Mineral chemical analyses suggest that the various rock types are representative of a fractionation trend from magnesian troctolites through olivine and clinopyroxene gabbros to iron-enriched orthopyroxene gabbros. Within many individual samples, the primary mineral phases are apparently chemically …

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.

Paleoclimatic Implications Of Oxygen Isotope And Sedimentological Study Of Late Miocene And Early Pliocene Sediments From The South Atlantic, Western Indian Ocean, And The Gulf Of Aden, Kathryn M. Scanlon

Geology Theses and Dissertations

Previous work by many authors has implied that the Antarctic ice sheet underwent a major expansion in the latest Miocene. It was intended in the present study to use the oxygen isotope event, which could be expected to accompany this glacial expansion, as a stratigraphic marker to aid in the correlation of several DSDP Sites. Samples were taken at approximately 100,000 year intervals throughout the latest Miocene and early Pliocene sections at Sites 237 and 249 in the western Indian Ocean, Site 360 in the South Atlantic and Site 231 in the Gulf of Aden. Oxygen isotope analyses were done …

Geometry And Kinematics Of Continental Deformation In Zones Of Collision: Examples From Central Europe And Eastern Mediterranean, Ali Mehmet Celâl Sengör

Geology Theses and Dissertations

Consideration of world-wide epicenter distribution has shown that deformation in continental lithosphere is not narrowly confined to well-defined plate boundaries but is present in wide, diffuse plate boundary zones. Early studies on the seismicity of the peri-Mediterranean area resulted in the division of the lithosphere in that region into a number of small plates, or microplates. Later studies in central Asia, which integrated seismicity with Quaternary geology, indicated, however, that a continuum approach may be more realistic to describe continental tectonics. This study concentrates on geometry and timing of continental deformation that resulted from continental collision in Central Europe and …

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 …

The Development Of Foliations In Low, Medium And High Grade Metamorphic Tectonites, William J. Gregg

Geology Theses and Dissertations

Studies of foliation and associated microstructures are presented from a variety of rock types and localities in the metamorphic terrains of the northeastern United States.
At Islesboro, Maine cleavage is well developed in lower greenschist grade siltstones and interbedded pelites of lower Paleozoic age. Cleavage in the siltstone units consists of two types of discrete mica films: short film segments and lengthened mica film. Thick secondary mica-rich layers are also exhibited in some siltstones. The short film segments appear to be basic elements through which cleavage development progresses by a linkage process that is poorly understood. The linkage of these …

Geology Of The Badger Bay-Seal Bay Area, North-Central Newfoundland, K. Douglas Nelson

Geology Theses and Dissertations

Coastline in the Badger Bay-Seal Bay area of north-central Newfoundland exposes the thickest and least disrupted section of Ordovician rocks in Newfoundland's Central Volcanic Belt. The following conformable stratigraphic sequence is observed: 1) >5 km. of variegated mafic and silicic submarine volcanics and volcaniclastics of lower Ordovician age; 2) a thin (<.5 km.) sequence consisting of thin bedded red and green argillites, manganiferous cherts, bioturbated cherts and black sulferous graptolite-bearing argillites of Caradocian age; 3) >1.2 km. of quartz-rich sandstones of upper Ordovician age. Correlative sequences occur to the east in the Fortune Harbour Peninsula area and on New World Island. Together they record Early Ordovician island arc volcanism, Medial Ordovician cessation of volcanism and subsidence, and Medial through Late Ordovician uplift and …

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, …

Stratigraphy, Depositional Environment And Structure Of The Taconic Allochthon, Central Washington County, New York, Louise D. Jacobi

Geology Theses and Dissertations

The Taconic Allochthon contains rocks of Cambrian (?), Cambrian and Ordovician age. It measures approximately 200 kilometers by 25 kilometers and is located in contiguous sections of New York, Vermont, Massachusetts, and Connecticut. The rocks are predominantly slates with lesser amounts of arenites, wackes, limestone, chert, and conglomerates. All have been subjected to chlorite or biotite grade metamorphism and two tectonic deformations. The study area in central Washington County, New York, contains most of the Taconic sequence, and because of both natural and man-made exposure it is more accessible than most other locations. A lithostratigraphic column has been identified which …

Geology Of The Northern Lewis Hills, Western Newfoundland, Jeffrey Alan Karson

Geology Theses and Dissertations

The Lewis Hills is the southernmost of the four Bay of Islands Ophiolite Complex massifs. These massifs are considered to be the dissected remnants of a once nearly continuous thrust slice of oceanic crust and upper mantle of Early Ordovician age. The Lewis Hills Massif may be divided into three north south trending zones. The eastern zone (Bay of Islands Complex) is composed of variably deformed and recrystallized gabbro, troctolite, wehrlite and dunite cumulates and harzburgite tectonites. The western zone (Little Port Assemblage) consists of greenschist facies metagabbros, diabase dikes and minor quartz-diorite bodies. The central zone (Mount Barren Assemblage) …

Long-Distance Turbidite Correlations In The Horseshoe Abyssal Plain, William H. Hoyt

Geology Theses and Dissertations

Few studies on modern abyssal plain turbidites have attempted to assess the lateral extent of individual units and few have therefore been able to provide any information on the evolution of turbidity deposits across long abyssal plain distances. In the 4755 m-deep Horseshoe Abyssal Plain, ten distinct lithologic units (six of these Iberian Peninsula-derived turbidites) were delineated in nine piston cores on the basis of stratigraphic position, thickness (range of 20 cm to greater than 500 cm), color, sediment type, sedimentary structures, x-ray mineralogy, and the ubiquitous presence of units in all abyssal plain and supplying canyon piston cores. In …

Structural Studies In The Northern Chester Dome Of East-Central Vermont, Bruce Wallace Nesbit

Geology Theses and Dissertations

Rocks in the Eastern Vermont Sequence are highly metamorphosed and are said to range in age from Precambrian to Siluro-Devonian. The sequence outcrops on Keyes Mountain, about 6km Northwest of Felchville, Vermont, and an area on this mountain about 2km square was mapped in great detail.
The dominant rock type found is quartzofeldspathic gneiss, but schistose gneiss, amphibolite, quartzite and schist also occur. Most of these rocks are layered but layering has been transposed in many places and much of it is probably secondary. Layering and schistosity both dip dominantly to the north at about 25º.
A number of mesoscopic …

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, …

Structural Studies In The Moretown And Cram Hill Units Near Ludlow, Vermont, William J. Gregg

Geology Theses and Dissertations

The geology of the eastern limb of the Green Mountain Anticlinorium consists of a series of Paleozoic metasedimentary rocks with lithologic boundaries arranged in a remarkably straight trend approximately parallel to the axis of the Green Mountains. Published reports of the area, consisting largely of reconnaissance mapping, have treated this complex series of polyphase deformed rocks as an essentially upright autocthonous sedimentary sequence. Boundaries between rock units have, for the most part, been assumed to be primary in origin, as have various structural elements within the rock units. More recent work in selected areas within the Ludlow Quadrangle has revealed …

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

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 …

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

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 …