Impregnated samples taken from three different post depositional regimes within the Mariana Mounds hydrothermal area in the Mariana Trough were observed in the back-scattered mode in the SEM. Intensity gradient orientation analysis methods have been adapted to study the orientation patterns within the sediments representing one of the first applications of such quantitative microfabric methods to the study of natural materials. Orientation was specified by two separate parameters, an index of anisotropy and a direction of orientation. The index is generally low for any single image, but by plotting the direction and anisotropy as a vector centered on the relevant specimen co-ordinates, consistent patterns of orientation were observed in the samples. Differences between the orientation patterns from the three environmental regimes were noted. A new dispersion ratio parameter was used to assess within sample variations. In a complementary study, objective thresholding methods based on Kohler's relative histogram method were used to segment the images. Assessments of porosity showed differences which were generally consistent with the trends noted from orientation analysis. While this paper uses image analysis techniques to examine deep sea sediments, the methods of analysis described are equally applicable to sediments on the continental shelf. © 2002 Elsevier Science Ltd and INQUA. All rights reserved.
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