The Middle Jurassic-Lower Cretaceous Fossil Bluff Group of Alexander Island, Antarctica represents the fill of a fore-are ba sin unconformably overlying an accretionary complex. Like most fore-are basins, this example had been considered to have a passive origin, as a topographic hollow between the are and the trench-slope break. Recent discoveries of igneous rock coeval with sedimentation have altered this view. Oxfordian-Kimmeridgian basaltic and rhyolitic sills and lava flows are found in a restricted area at the north of the basin, within a single formation. Chemically, most basalts are high-Nb types, which cannot have originated in a supra-subduction zone setting. Since the age of emplacement of these rocks coincides with a gap in the record of plutonism in the Antarctic Peninsula volcanic are, it is concluded that a late Jurassic pause in subduction led to active rifting to form the fore-are basin.
|Number of pages||8|
|Publication status||Published - 1999|
- GONDWANA BREAK-UP
- ALKALINE MAGMAS
- MAFIC DYKES