Thesis (M.S.) University of Alaska Fairbanks, 2006The Alpha-Mendeleev Ridge is an aseismic ridge bisecting the Amerasian Basin, Arctic Ocean. There is no widely accepted theory of formation. Gravity and bathymetry data from the poorly understood ridge are used to constrain the isostatic compensation of the feature in the frequency domain. Spectral analysis of the cross correlation between gravity and bathymetry along nine data transects collected from submarines and ice breakers over the ridge yield an average crustal thickness estimate of 30 km and density estimate of 2.75 g-cm⁻³. It also suggests compensation by local isostasy, as a near-ridge oceanic plateau or an extended fragment of continental shelf. These parameters are used to constrain gravity models of crustal structure. The analysis suggests no difference between the compensation of the Alpha and Mendeleev Ridges. These results are discussed in the broader tectonic context of the Amerasian Basin, in light of the current controversy over the formation of the ridge.1. Introduction -- 1.1. Tectonic history of the Arctic Ocean -- 1.2. The Alpha-Mendeleev Ridge -- 1.3. Purpose -- 2. Spectral analysis -- 2.1. Introduction to spectral analysis -- 2.1.1. Historical results -- 2.1.2. Theory -- 2.1.2a. Calculating admittance -- 2.1.2b. Theoretical isostatic models -- 2.1.3. Methods & data reduction -- 2.2. Shiptrack data -- 2.3. The Alpha-Mendeleev Ridge Complex -- 2.3.1. Results of spectral analysis -- 2.3.2. Isostatic models for the Alpha-Mendeleev Ridge complex -- 2.4. Alpha-Mendeleev Ridge sections -- 2.4.1. Results of spectral analysis -- 2.4.2. Isostatic models for Alpha and Mendeleev Ridges -- 2.5. Discussion of results -- 2.6. Data grids -- 3. Gravity modeling -- 3.1. Introduction -- 3.2. Methods : 3.2.1 2-D Shiptrack models -- 3.3. Results -- 3.3.12-D Crustal models -- 3.3.2. Grid crustal models -- 4. Discussion -- 4.1. Near spreading center hotspot activity -- 4.2. Rifted continental fragment -- 4.3. Consistent tectonic models of the Amerasian basin -- 5. Conclusions -- References -- Appendix
