Abstract: Evaporitic Lithofacies Continuum--Continental to Subaqueous Deposits

B. C. Schreiber, R. Catalano, E. Schreiber

Evaporitic deposits have been typified as either supratidal or as subaqueous, and these two realms curiously never seem to meet. In the Messinian deposits of Sicily, however, the depositional continuity is complete. This region shows the results of the synchronous formation of subaerial sulfate deposits landward of the basin margins, supratidal sulfate, carbonate and salt deposits on the landward edges, inter- and subtidal sulfate, carbonate and salt deposits seaward of the margins, and basinal sulfates, carbonate-rich shales and salts out in the deeper waters. Clastic detritus, reworked from adjacent continental areas and from shallow water are among the sediments commonly observed. These clastic components also include some of the carbonate and sulfate formed in the shallow-water en ironments of the sea. It must be noted that a paucity of skeletal material, other than algal debris and the shells of a few varieties of specialized gastropods, was produced within the hypersaline sea. The only exceptions to this were in marginal lagoons or in isolated arms of the sea, into which considerable fresh water flowed.

A complication in this tidy model is the fact that a large hypersaline basin is in a delicate balance between evaporation and influx. A small variation in this balance will result not only in a marked salinity change but also may produce a significant change in sea level (i.e., drawdown). Indeed the shoreline of a hypersaline basin may migrate from time to time, probably pausing successively at certain elevations, the configurations of which represent more or less stable points in the water budget. The result of this sea-level and salinity fluctuation pattern is reflected in marked vertical changes in deposition at any given site.

AAPG Search and Discovery Article #90978©1975 GCAGS-GC Section SEPM Annual Meeting, Jackson, Mississippi