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Resolution of Paleobathymetric Trends Using Benthic Foraminiferal Morphometrics

A. C. Gary, N. Healy-Williams

Foraminiferal species exhibit a wide range of morphological characteristics, some of which are a reflection of the environment of their habitat. These ecophenotypic responses may provide a powerful clue to determining past depositional environments. In most morphologic studies of benthic foraminifera, relationships have been shown between test size and water depth and between surface sculpture and water depth. We applied an automated imaging system to examine the morphology of three species of Bolivina from the northwestern Gulf of Mexico. Two of the three species analyzed displayed clear relationships with test shape and water depth. Overall test shape appeared to be the most important discriminator of depth, but changes in the periphery (i.e., spinosity) of the foramini era were also noted in one species. All of these results clearly indicate that the test shape of benthic foraminifera hold the possibility of providing facies information to paleontologists. Importantly, these results indicate that imaging techniques are capable of distinguishing changes in shape with depth. The quantification of these changes offers the possibility of precise and rapid depth determinations with an accuracy and resolution not possible with many other techniques.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.