Skip to Main Content
Book Chapter

The evolution of Miocene surface and near-surface marine temperatures: Oxygen isotopic evidence

By
Samuel M. Savin
Samuel M. Savin
Search for other works by this author on:
Linda Abel
Linda Abel
Search for other works by this author on:
Enriqueta Barrera
Enriqueta Barrera
Search for other works by this author on:
David Hodell
David Hodell
Search for other works by this author on:
James P. Kennett
James P. Kennett
Search for other works by this author on:
Margaret Murphy
Margaret Murphy
Search for other works by this author on:
Gerta Keller
Gerta Keller
Search for other works by this author on:
John Killingley
John Killingley
Search for other works by this author on:
Edith Vincent
Edith Vincent
Search for other works by this author on:
Published:
January 01, 1985

Oxygen isotopic analyses of planktonic foraminifera have provided a picture of many aspects of the evolution of the temperature structure of surface and near-surface oceans during the Miocene. In time slice studies oceanographic conditions have been interpreted from synoptic maps of isotopic data at between 22 and 27 locations in the Atlantic, Pacific and Indian Oceans. Three time slice intervals were examined: 22 Ma (foraminifera! zone N4B) and 16 Ma (N8) in early Miocene time; and 8 Ma (N17) in late Miocene time. In time series studies, the evolution of oceanographic conditions at single localities during an extended period of time were inferred from δ18O values of planktonic foraminifera.

Surface waters warmed throughout the early Miocene at almost all localities examined. At 22 Ma, the Pacific Ocean was characterized by relatively uniform temperatures in the equatorial region but a marked east-west asymmetry in the tropical South Pacific, with higher temperatures in the west. Between 22 Ma and 16 Ma, tropical Pacific surface waters warmed, but warmed more in the east than the west. At 16 Ma, the asymmetric distribution of temperatures in the South Pacific Ocean remained, and the latitudinal temperature gradient, inferred from the isotopic data, was gentler than that of either the late Miocene or Modern ocean.

Between the late early Miocene and late Miocene, surface waters at most low-latitude Pacific sites warmed while those at high latitudes cooled or remained unchanged. However, surface waters at high northern latitudes in the Atlantic Ocean as well as in the eastern equatorial Atlantic cooled, while water temperatures remained relatively unchanged at most South Atlantic sites. Surface waters warmed in the southernmost Atlantic, off the tip of South Africa. By 8 Ma, the east-to-west asymmetry of the temperature distribution in the tropical South Pacific Ocean had lessened. Surface water temperatures had become quite similar to those of the Modern ocean except that those in the equatorial Pacific Ocean were lower than today’s. This is reflected in the latitudinal gradient of surface temperatures at 8 Ma which is less steep than that of modern temperatures.

The pattern of surface temperatures and their evolution through the Miocene is consistent with the biogeographic distributions of planktonic foraminifera described by Kennett et al. (this volume). The isotopic data provide a more detailed picture of the evolution of Miocene surface temperatures than had been hitherto available, and serve as a framework against which hypotheses can be tested regarding the cause of the middle Miocene cooling of deep waters and the formation of the East Antarctic ice sheet.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Memoirs

The Miocene Ocean: Paleoceanography and Biogeography

James P. Kennett
James P. Kennett
Search for other works by this author on:
Geological Society of America
Volume
163
ISBN print:
9780813711638
Publication date:
January 01, 1985

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal