North Atlantic Late Miocene Stable-Isotope Stratigraphy, Biostratigraphy, and Magnetostratigraphy ...

• Main Authors: Keigwin, L. D., Aubry, Marie-Pierre, Kent, Dennis V.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Columbia University 1987
• Subjects: Geophysics; FOS: Earth and related environmental sciences; North Atlantic; Northeast Atlantic
• Online Access: https://dx.doi.org/10.7916/d8zg72rw; https://academiccommons.columbia.edu/doi/10.7916/D8ZG72RW

Upper Miocene foraminiferal nannofossil ooze and chalk from DSDP Hole 552A in the northeast Atlantic Ocean have been closely sampled for biostratigraphic, paleomagnetic, and stable-isotopic studies. Sampling at 10-cm intervals resulted in an uppermost Miocene isotope stratigraphy with a 1000- to 3000-yr. resolution. Covariance in benthic (Planulina wuellerstorfi) and planktonic (Globigerina bulloides) foraminiferal δ^O¸ records is taken as evidence for variability in continental ice volume. Our best estimate is that glacial maxima occurred at ~ 5.0 and ~ 5.5 Ma and lasted no more than 20,000 yrs. These events probably lowered sea level by 60 m below the latest Miocene average. There is little oxygen-isotope evidence, however, for a prolonged glaciation during the last 2 m.y. of the late Miocene. High- and low-frequency variability in the δ^13C record of foraminifers is useful for correlation among North Atlantic DSDP Sites 408, 410, 522, 610, and 611, and for correlation with sites in other oceans. Similar ...