HR: 0830h
AN: T31D-0872    [PDF]
TI: Formation of the Jan Mayen Microcontinent, the Norwegian Sea
AU: * Rey, S S
EM: sebassre@vbpr.no
AF: Volcanic Basin Petroleum Research, Forskningsparken Gaustadalleen 21, Oslo, 0349 Norway
AU: Eldholm, O
EM: olav.eldholm@geo.uib.no
AF: Department of Earth Science, University of Bergen, Allegaten 41, Bergen, 5007 Norway
AU: Planke, S
EM: planke@vbpr.no
AF: Volcanic Basin Petroleum Research, Forskningsparken Gaustadalleen 21, Oslo, 0349 Norway
AB: We have conducted a global study of microcontinents, which we define as crustal fragments with continental-like structure and composition, isolated in oceanic crust, with an extent of less than 10${^6}$ km ${^2}$. Microcontinents are formed in both extensional and transtensional tectonic regimes, and exhibit a range of distinct features such as (1) bathymetric highs, (2) positive free-air anomalies, (3) magnetic quiet zones, (4) prograding sedimentary sequences on the flanks, (5) older than surrounding crust, and (6) different heat flow signatures than the surrounding crust. They commonly also contain some amount of magmatic complexes. Only eight structures worldwide are true microcontinents by our definition, including the Jan Mayen microcontinent in the Norwegian Sea. The Jan Mayen microcontinent is a 500 km long and 160 km wide NNE-trending structure, comprising the bathymetric prominent Jan Mayen Ridge in the NE and a western and southern part with a more subdued bathymetric expression. Its crustal thickness reaches a maximum of 15 km with a lower crustal root displaced 10 km east of the axis of the ridge. The root has seismic velocities in the range from 6.7 to 7.0 km/s and is associated with a magnetic quiet zone, both suggesting a continental origin. A new continent-ocean boundary delimiting the microcontinent has been interpreted based on the extent of the magnetic quiet zone, the free-air gravity anomaly signature, seismic reflection data, and the velocity distribution. The Jan Mayen microcontinent separated from the volcanic rifted Voring and More margins off mid-Norway during Early Tertiary continental breakup and sea floor spreading. Close to the Eocene-Oligocene transition, the Kolbeinsey Ridge spreading axis started to propagate northwards from the Reykjanes Ridge into the East Greenland margin, thus constituting a prograding-retreating pair of axes with the Aegir Ridge. Sea floor spreading along the entire Kolbeinsey Ridge was obtained near the Oligocene-Miocene transition, leading to complete separation of the Jan Mayen microcontinent from the East Greenland continental margin. This event was concurrent with the extinction of the Aegir Ridge.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8105 Continental margins and sedimentary basins
DE: 9325 Atlantic Ocean
SC: Tectonophysics [T]
MN: 2003 Fall Meeting