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Miocene and younger sediments of the Gulf Coast locally contain numerous arenaceous Foraminifera. Certain genera and species are particularly useful in subsurface stratigraphy. Arenaceous forms present especially difficult problems in identification. These problems are compounded by the fragmentary condition of specimens present in the washed residues usually available to industrial paleontologists. Special care in washing is required if arenaceous forms are to reach the paleontologist in identifiable condition.
Bigenerina, Clavulina, and Martinotiella commonly can be identified when only uniserial fragments are available. These three genera are valuable guides in the recognition of depositional energy regimes. Bigenerina is typically found in high-energy lithotopes. Specimens are commonly present in beach and offshore-bar deposits. Clavulina requires a lower energy regime. It can be found in protected bays, or seaward from the surf zone on the open marine shelf. Martinotiella is restricted to low-energy environments. It is a minor component of middle Miocene and younger outer neritic faunas. Whereas all three genera are locally useful as stratigraphic markers, they have a broader utility in suggesting probable sand conditions. Under most conditions, the higher the energy level of the deposit onal environment, the more abundant and coarser the sand.
Several species of arenaceous Foraminifera used by oil industry paleontologists for subsurface correlations on the Gulf Coast are found in the same relative stratigraphic positions at least as far as the Caribbean basin. Textularia crassisepta, which marks the Pliocene-Pleistocene contact (Valvulina "H" datum) in offshore Louisiana, seems to have a similar level in Jamaica. Textularia subplana is typical of middle Pliocene (Buliminella "l") deposits in Louisiana. Specimens from samples of the same(?) age were found in northern Colombia and in Jamaica. Bigenerina humblei, a middle Miocene index species in Texas and Louisiana, may be a junior synonym for Textularia falconensis Cushman and Renz, a Venezuelan stratigraphic marker. Renz believed the latter to be useful throughout the Carib ean region.
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