SOFIA - MGS-Perkins 1968, Second Annual Field Trip of the Miami Geological Society, February, 1968

Second Annual Field Trip of the Miami Geological Society, February, 1968

Compiled By

Ronald D. Perkins

FIELD TRIP INTRODUCTION

The first geological exploration of the Caloosahatchee River was conducted by Angelo Heilprin in 1886. "Heilprin (1887, p. 28) believed these deposits to be the most remarkable yet discovered in the state and paleontologically perhaps the most significant deposits east of the Mississippi River. On the basis of ratio of extinct to extant molluscan species, Heilprin designated the lower beds the Floridan and assigned them a Pliocene age. These lower beds have subsequently been referred to as the Caloosahatchee Formation (Matson and Clapp, 1909, p. 123). The overlying Pleistocene deposits consisting of alternations of freshwater, brackish, and marine marls and limestones were subsequently grouped as the Fort Thompson Formation (Sellards, 1919, p. 71).

Heilprin's assignment of the Caloosahatchee Formation to the Pliocene was accepted by Dall (1887) and, in general, by most later workers. However, DuBar (1958, p. 95) seriously questioned the assignment of the Caloosahatchee to the Pliocene and, "on the basis of the vertebrate fauna and to a lesser degree on the molluscan fauna and stratigraphic relationships," assigned the Caloosahatchee to the Pleistocene. Olsson and Petit (1964, p. 513) reviewed the problem and concluded "the age assignment of the Caloosahatchee to the mid-Pleistocene ....is, therefore, wholly incompatible with existing information, and the true position of the Caloosahatchee in the upper Tertiary as held by all earlier workers remains more firmly established than ever."

A paper presently in progress by Druid Wilson (noted in Olsson and Petit, 1964, p. 513) focuses attention on a new stratigraphic unit (Unit A) between the Caloosahatchee and Fort Thompson Formations and separated from these units by sharp unconformable contacts. Unit A is considered to be the earliest Pleistocene in south Florida. Brooks (1967, personal communication; 1968, this publication) has recently suggested a reorganization of stratigraphic nomenclature for the Caloosahatchee River area in which the Caloosahatchee Formation has been subdivided into two members, the lowermost of which is assigned to the Pliocene, the uppermost to the Pleistocene.

With this historical background in mind, it seems appropriate that the Caloosahatchee age problem be reappraised at this time, incorporating some of the more recent work. We are pleased that Dr. H. Kelly Brooks, Dr. Axel A. Olsson, Dr. Jules R. DuBar, and Dr. Druid Wilson have agreed to participate as field trip leaders. It is the intent of this field excursion to bring these prominent workers together for a stimulating, free exchange of ideas and for a reevaluation of the field evidence bearing on the problem. With but one exception, all the articles contained within this guidebook have been especially prepared for this field conference and several interpretations are being presented for the first time.

The greatest portion of our trip will be devoted to exposures along the Caloosahatchee River between Ortona Lock and Fort Denaud. Recent widening of the river by the U. S. Army Corps of Engineers has produced numerous fresh exposures, while at the same time destroying older, more weathered localities. The type section of the Fort Thompson Formation has been completely destroyed by this most recent dredging operation (see photograph on title page).

On Saturday evening, Mr. Walter L. Erwin of the Sun Oil Company will address the group on the "Techniques, History, and Economics of Oil Exploration in Florida." This talk will provide an introduction to the second part of our trip which deals with the Sunoco-Felda and Sunniland oil fields of Hendry and Collier Counties. A brief article on these fields has been prepared by Clarence V. Babcock of the Florida Geological Survey.

The final portion of our trip will include stops along the recently completed Everglades Parkway (Alligator Alley) between Naples and Andytown. New exposures produced by dredging operations along the road will be examined and interpreted stratigraphically.

A detailed road log is included in the Appendix along with graphic sections for stops along the Caloosahatchee River.

(The entire report is available below)