Silicoflagellate abundance in ODP Holes 162-982B and 162-907B

• Main Author: Amigo, Alejandro E
• Format: Dataset
• Language: English
• Published: PANGAEA 1999
• Subjects: Ocean Drilling Program; ODP; Rockall Plateau; Iceland Plateau; Iceland
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.804999; https://doi.org/10.1594/PANGAEA.804999

Silicoflagellate assemblages were analyzed for the Miocene intervals recovered during Ocean Drilling Program (ODP) Leg 162. The middle and late Miocene are represented in Holes 907B (Iceland Plateau) and 982B (Rockall Plateau) by well-preserved silicoflagellates. A zonal scheme is presented, which improves previous attempts to establish a comprehensive silicoflagellate stratigraphy for this realm, based on an increased resolution given by the analysis of this largest-ever number of samples for the given interval (about three times as many as those studied for ODP Leg 104). The most important change is the replacement of the last appearance of Corbisema triacantha by the first appearance of Bachmannocena circulus apiculata as the top of the upper C. triacantha Zone/bottom of the B. c. apiculata Zone. In addition, two important bioevents (the first appearance of Bachmannocena diodon nodosa and the last appearance of Distephanus crux stradneri) allow the subdivision of the B. c. apiculata Zone into three new subzones: Caryocha spp. Subzone, D. c. stradneri Subzone, and B. d. nodosa Subzone (oldest to youngest, respectively). This zonal scheme is correlated with the standard calcareous nannoplankton zonation and tentatively correlated with the magnetic polarity time scale. A qualitative analysis of the changes in surface-water characteristics is given, based on the variation in abundances of the several silicoflagellate groups. This shows a replacement of silicoflagellates that are adapted to warm surface waters by those adapted to temperate surface waters during the middle Miocene. In turn, the latter are gradually replaced by those adapted to cool surface waters during the late Miocene. The taxonomy of the taxa encountered has been revised in an effort to bring together differing schools. Only one new taxon, Distephanus crux lockerii, is described herein.