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Are large oceanic depth anomalies caused by thermal perturbations?

Carol A. Stein and Seth A. Stein
Are large oceanic depth anomalies caused by thermal perturbations? (in The interdisciplinary Earth; a volume in honor of Don L. Anderson, Gillian R. Foulger (editor), Michele Lustrino (editor) and Scott D. King (editor))
Special Paper - Geological Society of America (July 2015) 514: 187-195

Abstract

The average depth and heat flow of oceanic lithosphere as functions of age are well described by cooling plate models in which old lithosphere approaches an asymptotic thermal structure, causing average depth and heat flow to flatten. However, some areas are significantly shallower or deeper than the global average for their age. One possibility is that the deviations reflect variations in lithospheric temperature structure. Another is that the deviations reflect processes including excess volcanism or dynamic effects of mantle flow. The first hypothesis assumes that the average flattening reflects thermal perturbations to halfspace cooling, so the temperature structures of areas that are unusually deep for their age reflect continued halfspace cooling and thus should have lower heat flow. Although this hypothesis predicts lower heat flow at deeper sites in old lithosphere, the deep sites are divided approximately evenly between ones with high and low heat flow. Instead, the anomalously deep sites occur primarily at passive continental margins, perhaps because of dynamic topography due to sublithospheric mantle processes, and in only a few cases thinner crust formed at slow spreading rates immediately after rifting. Similarly, preferentially high heat flow is essentially not observed at anomalously shallow sites, primarily on hotspot swells, indicating that the swells do not result from hotspots significantly reheating the lithosphere. Thus, in general, neither shallow nor deep areas reflect primarily perturbed lithospheric thermal structure. Hence a plate model is more useful than a halfspace model in describing how ocean depth and heat flow vary with lithospheric age, and excluding the vast majority of the seafloor while ascribing significance to the small fraction matching the halfspace model is pointless.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 514
Title: Are large oceanic depth anomalies caused by thermal perturbations?
Title: The interdisciplinary Earth; a volume in honor of Don L. Anderson
Author(s): Stein, Carol A.Stein, Seth A.
Author(s): Foulger, Gillian R.editor
Author(s): Lustrino, Micheleeditor
Author(s): King, Scott D.editor
Affiliation: University of Illinois, Chicago, Department of Earth and Environmental Sciences, Chicago, IL, United States
Affiliation: Durham University, Department of Earth Sciences, Durham, United Kingdom
Pages: 187-195
Published: 20150702
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 52
Accession Number: 2015-109560
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
Secondary Affiliation: Universita degli Studi di Roma La Sapienza, ITA, ItalyVirginia Tech, USA, United StatesNorthwestern University, USA, United States
Source Note: American Geophysical Union Special Publication 71
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201547
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