Skip to main content
×
Home
    • Aa
    • Aa

Strontium Isotope Ages of the Marine Merced Formation, near San Francisco, California

  • B. Lynn Ingram (a1) and James C. Ingle (a2)
Abstract

The strontium isotopic compositions of foraminifers ( Elphidiella hannaiwere determined to refine the age of coastal sediments of the Merced Formation and to evaluate the relation between transgressive–regressive cycles and Pleistocene glacio-eustatic sea-level fluctuations. Relatively good age resolution (± 0.1 myr) is possible in the upper part of the section. The Sr isotope ages provide strong supporting evidence for the fission track ages of an ash layer at the top of the formation (0.45 myr), as well as recent age estimates for the mammoth fossil of ∼0.45 myr. Sr isotope ages in the upper part of the section also confirm that marine/nonmarine cyclic sedimentation in the Merced Formation is controlled by glacial–interglacial cycles. Good age resolution for the lower part of the section is not possible, due to little variation of the87Sr/86Sr ratio in global sea water between 2.4 and 4.3 myr. The age of the base of the formation is constrained only between 2.4 and 4.8 myr. Sediment accumulation rates in the upper portion of the Merced Formation (between 0 and 720 m) are significantly higher than those calculated for the basal portion (between 720 and 1670 m). The change in accumulation rate may be due to increased continental weathering rates and/or increased tectonic subsidence beginning about 0.8 myr ago.

Copyright
Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

R.C. Capo , and D.J. DePaolo (1990). Seawater strontium isotopic variations from 2.5 million years ago to the present. Science 249, 5155.

H.E. Clifton , R.E. Hunter , and J.V. Gardner (1988). Analysis of eustatic, tectonic and sedimentologic influences on trangressive and regressive cycles in the late Cenozoic Merced Formation, San Francisco, California. New Perspectives in Basin Analysis Springer-Verlag, New York.p. 109–128

D.J. DePaolo (1986). Detailed record of the Neogene Sr isotopic evolution of seawater from DSDP Site 590B. Geology 14, 103106.

B.L. Ingram , and D. Sloan (1992). Strontium isotopic composition of estuarine sediments as paleosalinity-paleoclimate indicator. Science 255, 6872.

S.G. Lucas (1996). The Thornton Beach mammoth: Consistency of numerical age and morphology. Quaternary Research 45, 332333.

R.Z. Poore (1981). Temporal and spatial distribution of ice-rafted mineral grains in Pliocene sediments of the North Atlantic: Implications for late Cenozoic climatic history. J.E. Warme , R.G. Douglas , E.L. Winterer The Deep Sea Drilling Project: A Decade of Progress. Society for Economic Paleontology and Mineralogy, 505515.

A.M. Sarna-Wojcicki , C.E. Meyer , J.W. Hillhouse , N.T. Hall , and G.H. Curtis (1996). Age of the Thornton Beach, California, mammoth fossil updated. Quaternary Research 45, 327331.

A.M. Sarna-Wojcicki , C.E. Lajoie , C.E. Meyer , D.P. Adam , and H.J. Rieck (1991). Tephrochronologic Correlation of upper Neogene Sediments along the Pacific Margin, Conterminous United States. Geological Society of America, Boulder.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Quaternary Research
  • ISSN: 0033-5894
  • EISSN: 1096-0287
  • URL: /core/journals/quaternary-research
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×

Metrics

Abstract views

Total abstract views: 14 *
Loading metrics...

* Views captured on Cambridge Core between 20th January 2017 - 22nd August 2017. This data will be updated every 24 hours.