Named for Card Sound, an arm of Biscayne Bay. Type section is Sinclair No. 1 Williams well, sec. 24, T59S, R40E, Monroe Co., FL., interval between 5280 and 6690 ft. Occurs in southernmost FL. Consists of tan to gray, fine- to medium-grained, crystalline dolomite. Top of formation is defined by change in lithology from calcareous or dolomitic chalk above to medium crystalline dolomite below. Base is defined by change from medium crystalline dolomite above to argillaceous limestone below. Report includes type logs and sections. Age is Late Cretaceous (Gulfian).

Source: GNU records (USGS DDS-6; Reston GNULEX).

Late Cretaceous Card Sound Dolomite overlies Early Cretaceous Naples Bay Group and underlies Late Cretaceous Plantation Tongue (new) of the Rebecca Shoal Dolomite in the subsurface of southeastern FL.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Card Sound Tongue assigned to the base of Rebecca Shoal Dolomite in Winston (1989) and in this report. Unit has been penetrated in only two wells in the FL Keys and three wells on the Sarasota arch, but there is no evidence to connect the two locales. Seismic investigation is prohibited seaward of the Keys and is the only method that might confirm the presence of the Card Sound between the two areas. In one well, the younger Plantation Tongue has coalesced with the Card Sound and in several other wells the still younger Tavernier Tongue has coalesced with the Plantation. Shown in fig. 1 to overlie the Grassy Point limestone. No paleontologic data available to determine the age of the Rebecca Shoal or its three tongues. Earliest appearance of Card Sound Tongue is 100 ft above the Lower Cretaceous. This establishes an early Late Cretaceous age for this lower reef section.

Source: GNU records (USGS DDS-6; Reston GNULEX).