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Redacted for Privacy Abstract Approved: John V AN ABSTRACT OF THE THESIS OF MIAH ALLAN BEAL for the Doctor of Philosophy (Name) (Degree) in Oceanography presented on August 12.1968 (Major) (Date) Title:Batymety and_Strictuof_thp..4rctic_Ocean Redacted for Privacy Abstract approved: John V. The history of the explordtion of the Central Arctic Ocean is reviewed.It has been only within the last 15 years that any signifi- cant number of depth-sounding data have been collected.The present study uses seven million echo soundings collected by U. S. Navy nuclear submarines along nearly 40, 000 km of track to construct, for the first time, a reasonably complete picture of the physiography of the basin of the Arctic Ocean.The use of nuclear submarines as under-ice survey ships is discussed. The physiography of the entire Arctic basin and of each of the major features in the basin are described, illustrated and named. The dominant ocean floor features are three mountain ranges, generally paralleling each other and the 40°E. 140°W. meridian. From the Pacific- side of the Arctic basin toward the Atlantic, they are: The Alpha Cordillera; The Lomonosov Ridge; andThe Nansen Cordillera. The Alpha Cordillera is the widest of the three mountain ranges. It abuts the continental slopes off the Canadian Archipelago and off Asia across more than550of longitude on each slope.Its minimum width of about 300 km is located midway between North America and Asia.In cross section, the Alpha Cordillera is a broad arch rising about two km, above the floor of the basin.The arch is marked by volcanoes and regions of "high fractured plateau, and by scarps500to 1000 meters high.The small number of data from seismology, heat flow, magnetics and gravity studies are reviewed.The Alpha Cordillera is interpreted to be an inactive mid-ocean ridge which has undergone some subsidence. The Lomonosov Ridge is a narrow mountain range which extends from the continental slope off the Lincoln Sea to the Eurasian slope off the New Siberian Islands.In the middle of the basin, the Lomonosov Ridge is only 40 to 75 km wide.It becomes broader at the continental margins, where it merges with the Alpha Cordillera. In cross section, the Ridge has side slopes convex upward to a rounded crest.The minimum water depth on the Lomonosov Ridge is about 750 meters.It has a relief of about 3,200 meters above the floor of the basin.Aeromagnetic data indicates that the Ridge is not of volcanic rock and earthquake distribution data show that it is aseismic.The Lomonosov Ridge is interpreted to be a continental outlier in the Arctic basin. The Nansen Cordillera is an extension of the Mid-Atlantic Ridge across the Arctic basin.It extends from the passage between Greenland and Svalbard (The Lena Trough) to the Eurasian continental slope off the Lena River.Its axis lies on a great circle between these two points.In cross section, the Nansen Cordillera is about 200 km wide.It is made up of volcanoes or ridges standing about 1500 meters above the basin floor.There are V-shaped rifts in the Cordillera which are 1500 meters deeper than the basin floor (to 5500 meters water depth).Earthquake study shows that essentially all epicenters in the Arctic basin are in the Nansen Cordillera. Aeromagnetic data indicate that its rocks are only weakly magnetic. The Nansen Cordillera is interpreted to be an'embryonic" mid- ocean ridge.The basin floor is being rifted, but no uplift has occurred as yet. The three mountain ranges divide the Arctic basin into four sub-basins, each floored by a plain. From the Pacific-side of the Arctic basin these are:1) The Canada Basin, bounded by the conti- nental slopes of Alaska and Siberia and the Alpha Cordillera and floored by Canada Plain; 2) The Makarov Basin, bounded by the Alpha Cordillera and the Lomonosov Ridge and floored by Fletcher Plain; 3) The Fram Basin, bounded by the Lomonosov Ridge and the Nansen Cordillera and floored by Hakkel' Plain; and, 4) the Nautilus Basin, bounded by the Nansen Cordillera and the continental slope of Europe and floored by the Sverdrup Plain.Each of these plains is close to 4000 meters deep.Echograms show that they have slopes of only about 1:4000, but minor 'bumps" and swales of some ten meters relief are also shown. There are three regions of a few hundred meters depth on the margin of the Arctic basin.These are called the Arctic Rises.The largest of these is the Chukchi Rise, which appears to be an exten- sion of the Continental Shelf between Alaska and Siberia.The other two rises flank the Lena Trough.The Morris Jesup Rise, north of Greenland, appears to be a part of the Lomonosov Ridge.The Yermak Rise is an extension of the continent north of Svalbard. Two plains at intermediate depth (2000 to 3000 meters) are located on the flanks of the Alpha Cordillera at its intersection with the continental slope of Eurasia.These are named the Chukchi Plain and the Wrangel Plain.Each appears to be ponded sediment. The Lomonosov Ridge is taken as a boundary to divide the Arctic basin into two major sub-basins.The Fram and Nautilus Basins together make up the Eurasia Basin.The Makarov and Canada Basins together form the Amerasia Basin. The continental slopes and rises around the margins of the Arctic basin are described and illustrated.The slopes generally are steep and broken and the rise poorlydeveloped except for the section off the Mackenzie River and north of Alaska. Geophysical data from the Arctic basin are few and do not provide good geographical coverage.The data are reviewed and related to the physiography of the basin.It is hypothesized that the entire floor of the Arctic basin formed on the Alpha Cordillera following fracturing of a continent by mantle upwelling.Following formation of the basin by sea floor spreading, the cell centered beneath the Alpha Cordillera ceased to convect and is now in a cooling phase. A new phase of mantle convection is now thought to be begin- ning beneath the Nansen Cordillera. The geographical arrangement of the ocean floor features in the Arctic basin is discussed.It is suggested that the Arctic Rises and the Lomonosov Ridge are composed of fragments of the Arctic Paleozoic Fold Belts.This in turn indicates that the continental block was fractured in the Paleozoic Fold Belts rather than in the Precambrian Shields. Possible former extensions of the mantle convection cell, which is thought to have existed beneath the Arctic basin, are discussed.Evidence is presented for a "circular" termination of the cell at the Eurasian end of the Alpha Cordillera.Toward the Atlantic, the axis of the former convection cell is traced through Baffin Bay and into the Labrador Sea. A farther extension to an intersection with the Mid-Atlantic Ridge at 28° N. Lat.is suggested.The possible size and extent of the former convection cell is discussed and the name Wegener Rise proposed for its manifestation in the Earth's crust.The time of the formation of the Arctic basin is considered, although there are no unique data for age dating avail- able from the basin itself. Bathymetry and Structure of the Arctic Ocean by Miah Allan Beal A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1969 APPROVED: Redacted for Privacy Professo\ of Oceanography \ in charge of mjOr Redacted for Privacy Chairm n of the Departmeof Ocean?py Redacted for Privacy Dean clf graduate School Date thesis is presented August 12, 1968 Typed by Marion F. Palmateer for Miah Allan Beal AC KNOW LE DGEME NT I am deeply indebted to many people for assistance in the col- lection of the data upon which this study is based.Above all, great credit must be given to the officers and ratings of the nuclear sub- marines: The men who probed into the unknown regions beneath the ice pack to gather knowledge where none had existed before. A debt to Dr. Waldo K. Lyon, Civilian Research Director for the Arctic submarine expeditions is gratefully acknowledged.It was due to his careful planning that a reonaissance of all parts of the Arctic basin was accomplished.Mr. Arthur Molloy participated in most of the submarine cruises and in the processing of the echo- grams.His contribution to this study cannot be over emphasized. I have profited greatly from discussions with Dr. Ned A. Ostenso, Dr. Arthur Lachenbruch and Dr. Kenneth Hunkins, three of the foremost students of the Arctic basin.Each has been generous with his thoughts and with the unpublished data referenced in this study.The interpretation of these data is, of course, entirely my responsibility. Dr. John V. Byrne has guided this research and has had con- siderable influence on its content.Under his guidance, I have been encouraged to avoid the easy way and to enter controversial regions at the forefront of geological knowledge in the data interpretation. This freedom and encouragement are much appreciated, but it is even more incumbent than usual on the writer to stress that he is solely responsible for any errors in judgement in the study. Finally, I am privileged to acknowledge the debt that I owe to my wife, Phyllis, for her support and encouragement.She has as cheerfully lived with me on the shore of the Arctic Ocean as in San Diego, and has struggled alone with home and hearth while I was on board icebreakers and submarines for months at a time in carrying out my studies.
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