The Lower Cretaceous Ferry Lake Anhydrite is one of the most distinctive, widespread sedimentary units within the Gulf coastal plain. The formation extends from east Texas across southern Arkansas, northern Louisiana, central Mississippi, and southern Alabama, all the way to south Florida where it has been correlated with anhydrite beds of the Punta Gorda formation. The formation consists of alternating carbonates, claystones, and sulfate beds (altered from original gypsum to anhydrite during burial) deposited in a predominantly subaqueous environment within a broad lagoon located shoreward of an extensive reef fringing the shelf edge.

Highly resistive anhydrite beds within the Ferry Lake Anhydrite, and within formations above and below, may be correlated across east Texas, Arkansas, Louisiana, and Mississippi, using a network of closely spaced electrical logs. The geographic distribution of these anhydrite beds is variable. Some anhydrite beds may be traced across the entire area, whereas other beds are less widespread. The difference in geographic distribution of these beds reflects the variation in size and configuration of the extensive lagoonal sea in which they were deposited. Water depth, positive conditions around stable areas, subsidence, duration of each evaporitive pulse, and areal salinity variation are among the factors that controlled the thickness of individual beds accumulating within the lagoon.

End_of_Article - Last_Page 1428------------