1. The Foraminifera are grouped into three principal biofacies and one subfacies in the Mississippi Delta area.

    • The following species are confined to the marsh facies.

      • Ammoastuta inepta (Cushman and McCulloch)

      • Arenoparrella mexicana (Kornfeld)

      • Leptodermella variabilis Parker

      • Miliammina fusca (H. B. Brady)

      • Trochammina macrescens H. B. Brady

    • The Breton Sound facies is characterized by the abundance of various species of Ammobaculites, and also by Ammoscalaria pseudospiralis (Williamson) and Gaudryina exilis Cushman and Bronnimann. Elphidium incertum mexicanum Kornfeld and E. matagordanum (Kornfeld) also are largely confined to this facies.

    • The open-gulf facies is characterized by the following species.

      • Bigenerina irregularis Phleger and Parker

      • Bolivina lowmani Phleger and Parker

      • Buccella hannai (Phleger and Parker)

      • Buliminella cf. bassendorfensis Cushman and Parker

      • Cibicidina strattoni (Applin)

      • Epistominella vitrea Parker

      • Nonionella atlantica Cushman

      • N. opima Cushman

      • Nouria polymorphinoides Heron-Allen and Earland

      • Proteonina atlantica Cushman

      • P. sp. A

      • Virgulina pontoni Cushman

    • The offshore “subfacies” is characterized by the following species which are either restricted to it or occur there in greater abundance than elsewhere.

      • Bigenerina irregularis Phleger and Parker

      • Cibicidina strattoni (Applin)

      • Epistominella vitrea Parker

      • Nouria polymorphinoides Heron-Allen and Earland

      • Proteonina atlantica Cushman

  2. Facies transition areas

    • The average boundary between the open-gulf and Breton Sound facies extends south from Breton Island to Main Pass. There is a mixing of many typical open-gulf and Breton Sound species through a zone 10-15 miles wide extending on either side of this boundary.

    • The bays and other nearshore areas contain a Breton Sound fauna with marsh species.

    • Distribution of the living population of the various species seems to show good correlation with the distribution of the dead population. This suggests little large-scale post-mortem transportation of the tests.

    • The total living population varies from 1116/sample to 0/sample. The northernmost area generally has the smallest standing crop of Foraminifera, approximately 10–50/sample, the middle area averages approximately 100/sample, and the largest living populations occur at the inshore open-gulf stations.

    • The per cent ratios between living and total populations are grouped into four types of frequency areas. These show a general correlation with presumed sedimentation rates.

  3. It is believed that the distributions of the Foraminifera facies in this east delta area reflect the average distributions of the open gulf, Breton Sound, and marsh-river water masses.

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