Late Cenozoic development of the Knipovich Ridge (North Atlantic)

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Peyve, Alexander; Chamov, Nikolay
Holding Date 02 September 2008

Studying of the Knipovich ridge structures during expedition of R/V "Academik Nikolaj Strahov" in ۲۰۰۶ has shown that modern kinematics of its northern part is determined by right-lateral shift along the Molloy fracture zone (۳۱۵°). Such deformations are superimposed by system linked with rifting and lateral extension of the Knipovich rift structures (۳۶۰°). Thus in this region structures formed in two stress fields are combined. Stress filed of the regional right-lateral shift is implemented in multiple oblique north-east structures (normal faults and normal faults with shift component) which divide rift structures into different segments. Their orientation (۲۰-۳۰°) corresponds to the system of secondary antithetic left-lateral strike-slip faults. Studying of deformations in deposits and taking into account morphological relief features testifies that in the Knipovich ridge area extensional deformations (normal faults) prevail, compression results in the form of upthrusts and gentle folds in deposits are seen less often. Both from our point of view are the result of global right-lateral shift movements in an area between the Spitsbergen and Greenland, localized in various structures and existing for long time (Low Paleocene rocks are touched by these movements). Picks of tectonic activity separated by ۵۰-۶۰ Ma intervals are seen both in modern and older sediments. Depressions located ۴۰ km to the west from the rift axis can be interpreted as paleo rift zone that is connected at ۷۸°۰۷’ N and ۵°۲۰’ E with north-west trending fault that has marked the main right-lateral shift. Stress field of that period was similar to the modern. Rift jumped to the east (to modern position) about ۲ Ma if we assume spreading rate about ۰.۷ cm/year. Basalts composing heights to the west of the Knipovich rift valley can characterize initial stage of extension between Greenland and Spitsbergen with formation of diffuse spreading structures. Local basalt volcanism took place in formed multiple-aged rift structures. In the beginning of Miocene basic stretching zone has been localized within the modern rift valley of the Knipovich ridge. Thus absence of magmatic material to the north of ۷۷°۵۴’ N probably testify about amagmatic stage of the most northern ridge segment. Here thinning of continental crust is not enough for generation and outflow of oceanic basalts. To the south, despite occurrence of volcanic activity signs in the form of volcanic constructions and flows, slopes of the rift valley are substantially composed of Oligocene - Miocene lithified sedimentary rocks. Molloy basin located to the north can be considered also as a result of initial stage of extension of crushed Spitsbergen western continental margin which has not reached stage of generation and outflow of basaltic melts.

tags: etc