Studies have been made of about 1,300 glauconitic samples from the sea floor off southern California, in Monterey Bay, California, and off Cedros Island, Baja California. The principal depositional environments are continental terraces, banks, ridges, and basin slopes.

Clay aggregates that probably would be designated as glauconite, according to contemporary field usage of the term by geologists, grade from relatively soft, pale yellow-green, highly expandable montmorillonitic types to dark green, illitic types. As lattice thickness [d(001)] of these different types increases, the refractive index and potassium content decreases. The organic nitrogen content is greatest in highly expandable varieties.

Glauconite may compose from less than 1 per cent to about 80 per cent of the upper few centimeters of sediment. Maximum concentrations occur in the sediments from the outer shelf and upper slope areas, but the distribution is patchy, both areally and vertically, within these sediments. Glauconite is rare in water depths of less than 100 feet. Off southern California, glauconites that probably have been deposited from turbidity currents occur in near-surface sediments from the continental rise and on the abyssal floor.

Living benthonic Foraminifera of the same species as those that are filled with expandable glauconite occur in water depths that range from approximately 100 feet to 6,000 feet. Specimens of the genus Cassidulina are common in Foraminiferal faunas that contain abundant glauconite-filled tests.

Glauconite replaces argillaceous sedimentary rock, mineral grains, organic carbonate, and probable fecal pellets. Some spheroidal-ellipsoidal and irregular-papillate forms appear to be of accretionary origin. The mineralogy and morphology of fillings in Foraminifera indicate that they are probably deposited by direct precipitation. Distinctive morphological varieties of glauconite are not everywhere randomly distributed, but are commonly concentrated in localized areas, which indicates that variations in morphology may be caused by local conditions of origin.

Glauconites have been recognized that are reworked from Pliocene, and perhaps Miocene, submarine outcrops. Foraminiferal tests that are filled with glauconite range in age from Pliocene to Recent and from Pleistocene to Recent. No direct evidence of present-day formation of glauconite has been found.

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