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Structure, porosity and stress regime of the upper oceanic crust: Sonic and ultrasonic logging of DSDP Hole 504B

Tectonophysics

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, , , and

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Abstract

The layered structure of the oceanic crust is characterized by changes in geophysical gradients rather than by abrupt layer boundaries. Correlation of geophysical logs and cores recovered from DSDP Hole 504B provides some insight into the physical properties which control these gradient changes. Borehole televiewer logging in Hole 504B provides a continuous image of wellbore reflectivity into the oceanic crust, revealing detailed structures not apparent otherwise, due to the low percentage of core recovery. Physical characteristics of the crustal layers 2A, 2B and 2C such as the detailed sonic velocity and lithostratigraphic structure are obtained through analysis of the sonic, borehole televiewer and electrical resistivity logs. A prediction of bulk hydrated mineral content, consistent with comparison to the recovered material, suggests a change in the nature of the alteration with depth. Data from the sonic, borehole televiewer, electrical resistivity and other porosity-sensitive logs are used to calculate the variation of porosity in the crustal layers 2A, 2B and 2C. Several of the well logs which are sensitive to the presence of fractures and open porosity in the formation indicate many zones of intense fracturing. Interpretation of these observations suggests that there may be a fundamental pattern of cooling-induced structure in the oceanic crust. ?? 1985.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Structure, porosity and stress regime of the upper oceanic crust: Sonic and ultrasonic logging of DSDP Hole 504B
Series title:
Tectonophysics
Volume
118
Issue:
1-2
Year Published:
1985
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Tectonophysics
First page:
1
Last page:
42
Number of Pages:
42