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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 25 (1941)

Issue: 10. (October)

First Page: 1921

Last Page: 1933

Title: Relation of Organic Matter to Color of Sedimentary Rocks

Author(s): H. Previous HitWhitmanTop Patnode (2)


Sedimentary rocks may be classified as to color by their reflectivity, which is the percentage of light that they reflect. Compilation of measurements of about 3,000 samples shows that light-colored sediments have a low organic content and dark-colored sediments a high organic content. Since the organic content of sediments can not be measured directly, the reduction number and the nitrogen content, which are measures of the organic content, were used in the compilations. The data show that the relation of reflectivity to reduction number and reflectivity to nitrogen content vary with respect to the ratio of nitrogen to reduction number; sediments of the same color which have low reduction numbers being relatively poor in nitrogen. The reflectivity of sediments is not onl affected by the quantity of organic matter present, but also by the texture and the content of mineral pigments. A regional classification of the samples indicates that the average organic content of sediments of the same color is not the same for all areas. Despite the influence of several factors upon the color of sediments, measurements might be used advantageously to supplement descriptions of well samples and also as an aid to correlation.

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