Late Paleogene and Neogene radiolarian biostratigraphy of the Southern Ocean
Olson, Christopher J. (Student of geology)
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Biostratigraphic analysis of radiolarians from the highlatitude Southern Ocean has been documented for two piston cores. ARA Islas Orcadas Core 0775-47, located on the Maurice Ewing Bank at the eastern edge of the Falkland Plateau off South America,is older than the middle Miocene age assigned by Ciesielski and Wise (1977). A new zone, Stylosphaera haeckeliana (?), of late Oligocene age is proposed for the lower section of the core. A major late Miocene erosional unconformity separating lower Miocene sediments below from lower Pliocene sediments above represents a time loss of approximately 10 M.Y. and is related to increased bottom current activity associated with glaciation on the Antarctic continent. Paleomagnetic history for a second core, Eltanin 27-3, located on the south flank of the Albatross Cordillera, off Cape Adare in the Pacific Ocean sector suggests that sedimentation rates have been nearly constant since middle Gilbert (Pliocene) time. Absence of key, high-latitude zonal taxa in this core seems to be related to fluctuations in the geographical distribution of some radiolarian species in response to changing climatic conditions around Antarctica rather than the presence of sedimentary hiatus.