| Abstract: | Recent multidisciplinary geophysical measurements over the Lomonosov Ridge close to the North Pole support the widely held belief that it was formerly part of Eurasia. The known lithologies, ages, P-wave velocity structure and thickness of the crust along the outer Barents and Kara continental shelves are similar to permitted or measured values of these parameters newly acquired over the Lomonosov Ridge. Seismic, gravity and magnetic data in particular show that the ridge basement is most likely formed of early Mesozoic or older sedimentary or low-grade metasedimentary rocks over a crystalline core that is intermediate to basic in composition. Short-wavelength magnetic anomaly highs along the upper ridge flanks and crest may denote the presence of shallow igneous rocks. Because of the uncertain component of ice-rafted material, seafloor sediments recovered from the ridge by shallow sampling techniques cannot be clearly related to ridge basement lithology without further detailed analysis. The ridge is cut at the surface and at depth by normal faults that appear related to the development of the Makarov Basin. This and other data are consistent with the idea that the Makarov Basin was formed by continental stretching rather than simple seafloor spreading. Hence the flanking Alpha and Lomonosov ridges may originally have been part of the same continental block. It is suggested that in Late Cretaceous time this block was sheared from Eurasia along a trans-Arctic left-lateral offset that may have been associated with the opening of Baffin Bay. The continental block was later separated from Eurasia when the North Altantic rift extended into the Arctic region in the Early Tertiary. The data suggest that the Makarov Basin did not form before the onset of rifting in the Artic. |
