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Thermal Development and Rejuvenation of the Marginal Plateaus Along the Transtensional Volcanic Margins of the Norwegian- Greenland Sea

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Thermal Development and Rejuvenation of the Marginal Plateaus Along the Transtensional Volcanic Margins of the Norwegian- Greenland Sea City University of New York (CUNY) CUNY Academic Works All Dissertations, Theses, and Capstone Projects Dissertations, Theses, and Capstone Projects 1995 Thermal Development and Rejuvenation of the Marginal Plateaus Along the Transtensional Volcanic Margins of the Norwegian- Greenland Sea Nilgun Okay The Graduate Center, City University of New York How does access to this work benefit ou?y Let us know! More information about this work at: https://academicworks.cuny.edu/gc_etds/3901 Discover additional works at: https://academicworks.cuny.edu This work is made publicly available by the City University of New York (CUNY). Contact: [email protected] INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. A Bell & Howell Information Company 300 North Z eeb Road. Ann Arbor. Ml 48106-1346 USA 313/761-4700 800/521-0600 THERMAL DEVELOPMENT AND REJUVENATION OF THE MARGINAL PLATEAUS ALONG THE TRANSTENSIONAL VOLCANIC MARGINS OF THE NORWEGIAN-GREENLAND SEA by NILGON OKAY A dissertation submitted to the Graduate Faculty in Earth and Environmental Sciences in partial fulfillment of the requirement for the degree of Doctor of Philosophy, The City University of New York 1995 0MI Number: 9605644 Copyright 1995 by Okay, Nilgun All rights reserved. UMI Microform 9605644 Copyright 1995, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 © 1 9 9 5 NILGUN OKAY All Rights Reserved This manuscript has been read and accepted for the Graduate Faculty in Earth and Environmental Sciences in satisfaction of the dissertation requirement for the degree of Doctor of Philosophy. [Signature] D ate / J Professor Kathleen Crane ' Chair of Examining Committee [Signature] t/Z91 Date Professor Frederick C. Shaw Executive Officer [Signature] Professor Kathleen Crane [Signature] Professor Sonidcv BhattacharjV [Signature] Professor Millard F. Coffin Supervisory Committee THE CITY UNIVERSITY OF NEW YORK A bstract THERMAL DEVELOPMENT AND REJUVENATION OF MARGINAL PLATEAUS ALONG THE TRANSTENSIONAL VOLCANIC MARGINS OF THE EASTERN NORWEGIAN-GREENLAND SEA by Nilgun Okay Adviser: Professor Kathleen Crane The predominance of large-scale paleo-shear zones in the Norwegian- Greenland Sea is thought to be the major cause of asymmetric seafloor spreading in this region. Plate reconstructions suggest that nascent mid-ocean ridges propagated into these obliquely oriented shear zones causing transtension to occur. The asymmetric evolution of the northern Norwegian-Greenland Sea is evident from both the morphology of the seafloor as well as its geophysical characteristics. The eastern passive margins of the northern Norwegian-Greenland Sea are punctuated by volcanic plateaus which have significantly higher heat flow than the western passive margins. It is hypothesized that marginal volcanic plateaus formed originally in response to deviatoric stress developed at nascent mid-ocean ridge/shear zone intersections along transtensional margins causing lava to pond upwards on the eastern flank of the intersections. In addition, not only did paleo-shear zones serve as loci for the extrusion of seafloor basalts, but the distal limbs of these shear zones appear to be present-day sites for the emanation of heat from the seafloor thus thermally rejuvenating the eastern margins in the process. Heat flow analyses suggest that the thermal interactions between the Aegir and paleo-Mohns Ridges with the Eastern Jan Mayen Fracture Zone System created the Voring Plateau and rejuvenated the adjacent continental crust (to a thermal age of 16 my). The subsequent northward propagation of the paleo-Mohns Ridge into/and along the paleo-Senja Shear Zone, probably underplated the Svalbard Platform, and thus caused a broad thermal swell in the region. Multiple intrusions from this northward propagating asthenosphere probably occurred along deep-seated faults in and adjacent to the Svalbard Platform and the northern Svalbard-Nordaustlandet margin. Thermal modeling results also reveal that a secondary detachment fault system cuts the southern Yermak Plateau and intersects the Spitsbergen Shear Zone and could have acted as a conduit for the upward propagation of the Knipovich Ridge-related asthenosphere. Recent northward propagation of the Knipovich Ridge caused rejuvenation of the southern Yermak Plateau (35-11 mybp). SeaMARC-II, and geophysical data also suggest diffuse intrusion and thermal rejuvenation along the northern Svalbard-Nordaustlandet margin creating the Yermak Seamount, Mosby Peak and the Nordaustlandet Volcanic Terrain (20-37 mybp) in the process. PREFACE "Everything can be found at sea according to the sprit o f your quest. " Joseph Conrad The world's ocean is an important part of the global environment; because of its size and shape. It interacts with the earth's atmosphere and land masses so that it is vital to man's existence. The world's ocean resources have created a tremendous interest in recent years. This interest has accelerated the growth of the earth sciences and oceanography. New sea-floor mapping techniques and shipboard geophysical sensors have greatly improved the study of the world oceans in the last thirty years. Indeed, the first detailed seafloor maps are only thirty-five years old. The early scientists, aboard H. M. S. Challenger, accomplished the first ocean wide survey. This famous expedition (1872-1876) opened the era of ocean exploration. The Challenger, with its crew and seven scientists, crossed the Atlantic, Pacific, and Antarctic Oceans to observe weather, currents, water chemistry, temperature, bottom topography, sediments, and marine life on a global scale. These measurements have provided the factual foundation for the science of oceanography. The Norwegian North Polar Expedition into the Arctic Ice which took place a century ago aboard the Fram, and was lead by the Norwegian explorer Fridtjof Nansen between the years 1893-1896. The first detailed knowledge of the Arctic Ocean’s oceanography was obtained during this expedition. Nansen (1904) defined the bathymetry of the Fram Strait as a deep passage for exchange of the deepest water masses between the Arctic Ocean and Norwegian-Greenland Sea. He also postulated the existence of a 1500 m-deep sill; the so called Nansen Sill at 80°-81°N, The first results from this systematic survey were published by Louise Boyd in 1948. Bathymetric data has continued to accumulate since then by such investigators as Stocks (1950), Litvin (1964), and Johnson and Eckhoff(1966). Johnson and Heezen (1967) described the evolution of the region in the context of seafloor spreading. Vine and Matthews (1963) introduced the relationship of marine magnetic lineations to seafloor spreading, and Pitman and Heirtzler (1966) established the first magnetic time scale for the region. Depth measurements have appeared on maps as early as 1504. Magellan made the first deep-sea sounding in the Pacific Ocean in possibly 1521. He used the technique of tossing the lead, used to this day. An electronic sounding device, called an echo sounder or sonic depth finder, was developed in the 1920's. The SS Velekari under the leadership of Louise Boyd made the first systematic echo-sounding profiles of the Nordic Seas in 1937-1938 (Boyd, 1948). Development of the echo-sounder has resulted in improvements including high resolution digital imagery and accurate bathymetry across swaths of ensonified sea-floor: the side-scanning sonar. It constantly scans the seafloor beneath and to the sides of the research vessel. Sea mapping and remote characterization, carried out by the SeaMARC-II, sonar system combines the best abilities of the long-range side- viii looking sonar, GLORIA, and SeaBeam, the multibeam hull-mounted echo-sounding systems. More than 30 years ago, shortly after the first transpolar voyage under the ice by the USS Nautilus, nuclear-powered submarines were first recognized as unique platforms for conducting Arctic Ocean research. Since the legendary Alexander the Great descended (in 310 b.c) into the sea in a glass berry-like bell (Thurman, 1991), the use of manned submersibles such as ALVIN has contributed significantly to new . discoveries in the world oceans. However, adequate surveys on the Arctic Ocean seafloor have not happened, and I propose that only multi-national submarines operating under the ice in a systematic manner can collect the quality of data required to fill in the large data gaps. ACKNOWLEDGMENTS I believe this thesis will prove to be a significant contribution to the scientific community especially during the Nansen Arctic Centennial Anniversary. This is the first dissertation on marine geophysics in the City University of New York. I would like to thank my research adviser Prof. Kathleen Crane for introducing me to this study and counseling in my work. I thank my committee members, Prof.
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