Abstract: Historical Interval and Name Changes of the South Florida Sunniland Formation

Hugh J. Mitchell-Tapping

Many geologists working the Sunniland Trend may not understand some of the historical changes to the description of this formation as there are no formal records in the literature. This has caused great confusion resulting in misunderstanding and poor communication, especially in log correlation. Therefore, this study documents the various interval and name changes, and also outlines the field discoveries.

In southern Florida, the first exploration wells were rank wildcats and in order to understand the age of the rocks, geologists and paleontologists tried to equate the rock lithology to that of the rest of the Gulf Coast geology. Thus, on older logs the terms Trinity, Sligo, or Petit, etc., appear. Later, as more wells were drilled in this area, a separate lithologic column was developed among oil workers to describe certain intervals. One such Lower Cretaceous interval in southwestern Florida was named "Sunniland," a name formally given by Pressler in 1947 after oil was found in a well drilled by Humble Oil near the Sunniland railroad watering stop in Collier County. In 1954, Raasch, in a thesis on the Sunniland oilfield, formally called an interval that included an Upper Member (abo t 400 ft), a Middle Member (about 250 ft), and a Lower Member (about 500 ft), the "Sunniland Formation" based on a marker foraminifer. This interval is not what the oil industry calls the Sunniland Formation today. Later, in the 1970s after new fields were found and more wells drilled, the then Sunniland interval was formally redescribed by Winston in 1971 and only the Middle Member was called the "Sunniland Formation," while the Upper and Lower Members became the Lake Trafford and the Punta Gorda Formations, respectively. This is the classification used today.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas