Faster seafloor spreading and lithosphere production during the mid-Cenozoic

Concurrent changes in seawater chemistry, sea level, and climate since the mid-Cretaceous are thought to result from an ongoing decrease in the global rate of lithosphere production at ridges. The present-day area distribution of seafloor ages, however, is most easily explained if lithosphere produc...

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Bibliographic Details
Published in:Geology (Boulder) 2007-01, Vol.35 (1), p.29-32
Main Authors: Conrad, Clinton P, Lithgow-Bertelloni, Carolina
Format: Article
Language:English
Subjects:
Cenozoic
crust
Farallon Plate
Geological time
Geology
Geophysics
lithosphere
Marine
mid-ocean ridges
middle Cenozoic
ocean floors
oceanic crust
oceanic lithosphere
Pacific Ocean
Pacific-Farallon Ridge
Plate tectonics
rates
sea-floor spreading
Seismology
solid Earth (tectonophysics)
subduction
time factor
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Summary:Concurrent changes in seawater chemistry, sea level, and climate since the mid-Cretaceous are thought to result from an ongoing decrease in the global rate of lithosphere production at ridges. The present-day area distribution of seafloor ages, however, is most easily explained if lithosphere production rates were nearly constant during the past 180 m.y. We examined spatial gradients of present-day seafloor ages and inferred ages for the subducted Farallon plate to construct a history of spreading rates in each major ocean basin since ca. 140 Ma, revealing dramatic Cenozoic events. Globally, seafloor spreading rates increased by ∼20% during the early Cenozoic due to an increase in plate speeds in the Pacific basin. Since then, subduction of the fast-spreading Pacific-Farallon ridge system has led to a 12% decrease in average global spreading rate and an 18% or more decrease in the total rate of lithosphere production by the most conservative estimates. These rapid changes during the Cenozoic defy models of steady-state seafloor formation, and demonstrate the time-dependent and evolving nature of plate tectonics on Earth.
ISSN:0091-7613
1943-2682
DOI:10.1130/G22759A.1