A complete vertical column of the 2.8 mm. thick shale grading upward into the Upper Mississippian Second Abden Limestone at Fife, Scotland, was studied in an attempt to elucidate changes in its depositional environment and fauna from that of a near-shore terrestrial area (represented by the underlying fireclay) to the minor reefal development in the limestone.

Three thousand macrofossils belonging to 50 species, and 8,000 microfossils comprising 70 species were collected. The relative abundance of all species was calculated for equal quantities of rock in each of the 125 shale layers, which are approximately 2 cm. thick.

On the basis of certain indigenous macrofossils as well as on the microfauna and lithologic character, 4 topozones were recognized: (1) Lingula squamiformis and Streblopteria ornata; (2) Crurithyris urei and L. squamiformis; (3) Schizophoria resupinata and Eomorginifera longispina; (4) E. longispina, corals and bryozoans. Each succeeding topozone is more truly marine than its predecessor. The lowest (number 1) indicates deposition in conditions similar to those of the intertidal Wattenschlick deposits of the north German coast whereas the uppermost topozone (number 4) reflects conditions fast approaching those developing in the overlying limestone.

The succession of faunas in the shale indicates the marine transgression of the area. Reversal of such a series would indicate regression of the sea on shoaling. Recognition of a similar succession of faunas--perhaps over a much longer stratigraphic interval--may be useful in determining the position of the margins of former basins of sedimentation and in determining former transgressions and regressions of the sea.

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