Plate Tectonics and the Oceans

Another interesting article in the March issue of the NCGT Journal (see www.ncgt.org/newsletter.php page 56-60. It is on the origin of oceans and how they don't conform to the idea of new oceans by the separation of the continents. The age of young oceanic crust is defined from Jurassic to Holocene in accordance with the magnetic stripes found on the sea bed. Young oceans are said by mainstream to originate due to the stretching of continental crust (in association with subduction and rifting). Opinion on the origin of young oceans as a result of sea floor spreading is mostly based on the age of magnetic anomalies – but problems exist. For example, rocks at the N American continental margin of the Pacific are Miocene to Pleistocene in age whereas magnetic anomalies assign the region to the Palaeogene (and so on). The conclusion of the authors, Khotov, Schlezinger and Udintsov, is that a primary ocean would best fit the facts and sea floor spreading is not required. They also claim the mid ocean ridges emerged in the Palaeogene as zones of anomalous mantle eruption through oceanic crust.