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Oil exploration began in Florida in 1901, but no oil was found until 1943. In November of that year, Humble Oil and Refining Co. made a discovery near Sunniland in southern Florida. This field and the producing zone were called Sunniland. No further discoveries were made in southern Florida until 1954 when the Forty-Mile field was discovered by Gulf Oil Co. Ten years later, in 1964, the Sunoco Felda field was discovered by Sun Oil Co., followed by West Sunoco Felda field in 1968. Since that time, nine new fields have been discovered all from the same formation although none are as large as the Sunoco fields.
The examination of numerous cores and thin sections of this formation, both from producing fields and wildcat wells, reveals a sequence of deposition in the Sunniland formation. It has been reported that tintinnids or calpionellids have been observed in the lower mud section, but investigation of many thin sections from this section revealed only ostracod particles. Above the mudstone, the section becomes increasingly plentiful in fragmented microbored rudist particles and forams such as Orbitolina texana, Dictyoconus floridanus, and Coskinolina sunnilandensis. Above this section the sequence is considered regressive and consists of pellets and forams with a few mollusk fragments. This section is interpreted as the basal unit of a grainstone bar shoal. The grainstone bar shoal is made up of reworked particles of oysters (Texigryphea), coated caprinid fragments, forams, and echinoid fragments. This unit was deposited initially as a tidal bar shoal and then exposed to subaerial leaching.
For some years, the rocks of the Sunniland formation have been considered reefal, but based on the results of this study, these rocks are interpreted to be a barrier tidal-shoal bar deposited well behind the main reef crest, which lies farther offshore at the edge of the Florida escarpment.
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