Abstract:
Stichocorys peregrina (Riedel) contributes to paleoceanography as a valuable stratigraphic tool for correlation of deep-sea siliceous sediments in world oceans and as a paleoceanographic indicator. This paper documents the evolutionary morphologic changes of the S. peregrina lineage from the middle Miocene to late Pliocene in the eastern equatorial and eastern North Pacific (IODP Site U1335 and ODP Site 887, respectively). The size and shape changes show that there are at least two geographical variations in the S. peregrina lineage. In the eastern equatorial Pacific, two significant morphological shifts took place about 11.0 and 7.0 Ma, but the morphology remained relatively stable from 7.0 to 3.0 Ma. Coincident with morphological changes in the S. peregrina lineage were changes in biogenic productivity. These changes suggest that there is a close correspondence between major paleoceanographic events in the late Neogene and evolutionary changes of the S. peregrina lineage in the low latitudes. In the high latitudes, the ratio of the third segment to fourth segment in width and height showed a maximum from 9.5 to 8.0 Ma, and decreased stepwise at about 8.0 and 6.5 Ma. However, the radiolarian data in the high latitudes do not show a clear relationship between the paleoceanographic events and size variation of this lineage. The evolutionary transition from Stichocorys delmontensis to S. peregrina can be used as a primary biostratigraphic marker in the low latitudes. However, it is not easy to use the evolutionary transition for biostratigraphic correlation and age determination in the high latitudes, because there is no obvious change in the ratio of the third to fourth segment widths that can be used to distinguish S. delmontensis from the descendant S. peregrina. Abstract Copyright (2012) Elsevier, B.V.