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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 485

Last Page: 485

Title: Morphostratigraphy of Foraminifera Via Automated Image Analysis: ABSTRACT

Author(s): N. Healy-Williams, L. Robbins, R. Ehrlich


Morphologic variability of foraminifera is a virtually unexploited resource for definition of biozones, morphozones, and phylozones. The morphologic information contained within foraminiferal tests can result in a zonation based on subspecific characters and therefore can more finely divide stratigraphic sequences in comparison with more conventional biostratigraphic techniques. This morphozonation is extremely valuable for time intervals characterized by long ranging species and thick sedimentary sequences with few evolutionary marker events. Biozones can be used to identify sequences within a basin which have common ecomorphologic imprints. Through this precise measurement and determination of a common original shape, morphozones afford the possibility of evaluating dia enetic gradients.

The advantage of using foraminiferal morphometrics lies in great abundance of forams in relatively small samples, thus permitting measurement and evaluation of large numbers of forams in a narrow chronostratigraphic range. Measurement of such samples requires the use of automated image analysis procedures, by which large numbers of specimens can be measured in a short period of time. The development of automated image analyzers now allows for rapid and precise analysis of foraminiferal morphological changes. Our image analyzer is a TV signal fast analog-to-digital converter installed in a Z80-based microprocessor. It is capable of locating and digitizing foraminifera at the rate of more than 150 specimens per hour. The subsequent analysis of shape changes is via closed-form Fourier se ies and multivariate statistical techniques. Through the use of both image analysis and statistical methods, a precise quantification of morphological change is possible.

We have analyzed more than 12,000 specimens of 15 species of planktonic and benthic foraminifera from Holocene and Pleistocene sedimentary environments. The results clearly indicate that the quantification of morphological change is capable of precisely delineating common shapes within a zone which are related to changing environmental or evolutionary influences.

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Copyright 1997 American Association of Petroleum Geologists