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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Glauconite pellets are a major constituent of the sediments of the continental slope southwest of Point Conception, California. In areas where other sedimentation is limited, it may constitute more than 90 percent of the surface sediment. Such material commonly is interpreted as relict, but a possible evolutionary sequence of glauconite types is present. Initially, glauconite occurs as a filling or as recognizable internal molds of small shells, particularly those of benthic foraminifers. In later stages, the glauconite appears to be consolidated and concentrated as fecal pellets, mostly of burrowing echinoderms. Five transitional grades of glauconite are defined in the surface sediment. The initial stages disappear with depth in cores.
All evidence indicates that the depositional environment of these glauconites is completely normal bathyal marine. The U.S. Navy Civil Engineering Laboratory has sampled bottom water intensively in areas of high glauconite concentration. The temperature, salinity, dissolved oxygen, Eh, and pH of the bottom waters are normal for the appropriate depths in the northeastern Pacific. The oxygen minimum layer coincides with one area of glauconite concentration, but abundant glauconite occurs at other depths. A current meter in one area of high glauconite concentration registered near-bottom currents averaging 5 cm/sec predominantly parallel with the slope. The fauna is normal benthic, primarily echinoderms and polychaetes. No sign of anoxic conditions is seen in the water column or in the s diments. If the glauconite is authigenic, authigenesis must occur either in normal marine water or in the intestines of the mud-eating fauna.
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