Mid-Cenozoic post-breakup deformation in the 'passive' margins bordering the Norwegian-Greenland Sea

摘要

Since the initial breakup of the Norwegian-Greenland Sea in Early Eocene time (Chron 24B, 53.7 Ma), the conjugate 'passive' margins have been subject to compression, extension, magmatism, and broad uplifts and subsidence. Mid-to Late Cenozoic compressional doming basin inversion and reverse faulting occurred predominantly offshore within the rheologically weak deep Cretaceous depocenters. On the Norwegian margin, the domes seem to have formed primarily in Middle Eocene to Early Oligocene, and in Early Miocene, while doming in the Faroes-Rockall region developed in Late Paleocene to Early Eocene, Oligocene, and Mid- to Late Miocene. We suggest that the main driving force was plume-enhanced ridge push. A testable working hypothesis is that discrete phases of compression were associated with periods of high plume flux. In addition, the Oligocene (Chron 13, 35 Ma) change in plate motion appears to have generated local shear adjustments along pre-existing basement weaknesses, forming compressional structures in the overlying sedimentary section. This change in plate motion was first manifest by significant extension between be SW Barents Sea and the conjugate NNE Greenland margin, and led to spreading along the Knipovitch Ridge. Mid-Cenozoic extension and magmatism also preceded the development of the Kolbeinsey Ridge. The associated separation of the Jan Mayen microcontinent from East Greenland must have been strongly influenced by the position of the Iceland Plume center, in addition to the change in extension direction. With respect to initial breakup of the Norwegian-Greenland Sea in Early Ecocene time, the mid-Cenozoic extension and magmatism is a post-breakup phenomena. Widely spaced areas of Neogene uplift occurred along all bordering margins. These enigmatic uplifted areas acted as nucleation sites for growth of ice caps, and initiated large glacial deposits that built out on the adjacent shelves.