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The Tamiami Fossil Reefs

MikeR

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Belying its status as the third most populous state in the nation and America’s self-proclaimed vacation wonderland, Florida was perhaps the last paleontological frontier in the lower 48 states. South Florida in particular was thought of as a vast impenetrable swamp and it was not until the Academy of Natural Sciences 1886 scientific expedition led by Angelo Heilprin along Florida’s southwestern coast and interior that it was discovered that South Florida until quite recently was submerged. It was along a cut channel on the Caloosahatchee River that Heilprin found vast deposits of fossil shells similar to but in many ways different than the modern molluscan fauna found on the coasts today. He named these beds the Caloosahatchee Marl and later workers expanded upon his work describing similar shell beds below the Caloosahatchee (Tamiami/Pinecrest) and above (Bermont Formation) each holding unique faunas. Geologists through much of the 20th century described these beds as an example of layer cake stratigraphy, a geologically inert region in which sediments are deposited upon each other like layers of a cake. This interpretation however was shown to be more complex in the late 70s when Jack Meeder, a doctoral student at the University of Miami, first described zonated fossil reef tracks found during the construction of the Golden Gate housing development east of Naples, Florida. Later in the 80s Ed Petuch described a similar coral rich fauna west of Miami during construction of the Meadows of the Lake housing development on Bird Road as well as in the west near Immokalee in the Mule Pen Quarry. The molluscan fauna, particularly that at Bird Road, contained species found in the Duplin Formation of the Carolinas suggesting a Late Pliocene age. Petuch correlated these coral reefs which ringed the southern Florida peninsula with Pacific island atolls. By definition an atoll is a ring of coral reefs surrounding a lagoon formed by the collapse of an inactive volcano. Although not fitting this description, he named these coral reefs a psedoatoll for the lagoon they formed and which through land building on top of the Pliocene coral reefs would one day impound the Everglades Basin forming the southern rim of the Florida Pennisula. The coral facies would eventually be grouped as a member of the Tamiami Formation by Missimer (1992) and named the Golden Gate Member. Petuch has commented that the Golden Gate has as many as 120 different coral species (in his publications he lists about half that number), more than any other fossil deposit of any age in the United States with an interesting mix of corals also found in the Pinecrest, Cuba and Dominican Republic Pliocene and the Lower Pleistocene Caloosahatchee (http://nmita.iowa.uiowa.edu/nmita/generaList.page?classification=NMITA&taxonName=Zooxanthellate+Coral&getGenButton=Get+Genera).

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Figure 1. Corals from the Golden Gate Member of the Tamiami Formation.

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Figure 2. Mollusks from the Golden Gate Member of the Tamiami Formation.

In the construction of my Pliocene Project, it has been my desire for the past several years to sample deposits which could expand upon the fauna list that I have been compiling. In 2014 that included collection from the latest Piacenzian deposits in the Chowan River Formation in North Carolina. This year the plan was to increase my collection of the Duplin Formation from South Carolina which has been limited so far to two localities in Bladen County, North Carolina, however a hectic work schedule had kept me from that goal. I always thought that the Golden Gate member would be out of my reach in the foreseeable future as many of the quarries that mined the member such as Mule Pen had closed and Florida had gone through a devastating housing bust. That dream however became a reality when conversations with forum member jehussey revealed the existence of two exposures in Collier County, one an old spoil pile still collectable and lake construction for a new housing development, the other. A business trip to South Florida allowed me to meet up with Jim, a retired geologist, for a brief exploratory trip to the sites. This led to an extended vacation the following month where we could collect more extensively at the new site (Locality 1043). In addition we had the added pleasure of meeting up with FossilDawg who happened to be in Fort Lauderdale for a conference and whose extensive knowledge of paleontology and biology along with Jim’s geology background led to one of the more enjoyable trips that I ever had pleasure to attend.

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Figure 3. Locality 1043. Golden Gate Member of the Tamiami Formation, Collier County, Florida.

In July, Jim and I explored an old site (Locality 1044) which was dug to form lakes in a housing development in the early 2000s. Although heavily stained by the elements this site exhibits the classic nature of the Golden Gate member; partially lithified carbonate sediments indicative of reefs rich in scleractinian corals and mollusks preserved whole and as internal casts. The back end of the new construction site (locality 1043) that we briefly visited that day was much fresher with excellently preserved Pliocene shells and solitary corals as well as echinoids and shells suggesting some earlier Pleistocene deposits on top of the Golden Gate. One month later, the morning Don and I headed out from Fort Lauderdale across the Everglades to meet with Jim, the day was projected to be a scorcher, well into the upper 90s. When we all met and headed to the new construction site, the lake excavation was well underway exposing much more material than Jim and I had seen the prior month and although unbearably hot we all collected many invertebrate specimens from the Golden Gate. In his description of the Everglades Pseudoatoll, Petuch diagramed a zonated reef track reminiscent of a true atoll with a high energy reef crest containing low encrusting corals, a reef platform with large coral heads and the quiet back reef with solitary corals. The two sites we collected suggest this interpretation as the older site contained coral species indicative of the reef platform while the new site was rich in solitary species found in the back reef. Later we retired to Jim’s place for cold drinks and to marvel at the material Jim had collected from the older site when productive, many of which he kindly donated to Don and I and which contributed to the list below.

Golden Gate species list 103115.pdf

Collecting from these sites demonstrate the difficulty in proper species identification due to the mixture of differentially aged sediments from the digging process. Some of the species that I found are indicative of later units for example Fasciolaria okeechobeensis which is a guide fossil for the Bermont Formation and the extant echinoid Clypeaster rosaceus which originates in the Caloosahatchee. Quite a few of the mollusks collected are known primarily from the Caloosahatchee however I cross referenced these with both the Neogene Digital Atlas (neogeneatlas.org) and the Florida Museum of Natural History Invertebrate Paleontology database (http://www.flmnh.ufl.edu/invertpaleo/search.asp) to find records of their existence in the Tamiami. Although I am not completely confident that these species are Pliocene or Pleistocene I have listed them for now in the Golden Gate list.

References

Meeder, J., 1979, Pliocene reef of SW Florida, a field guide with road log. Miami Geological Society Guidebook, 19 p.

Missimer, Thomas M. 1992. Stratigraphic relationships of sediment facies within the Tamiami Formation of Southwest Florida: Proposed intraformational correlations. Plio-Pleistocene Stratigraphy and Paleontology of Southern Florida, Florida Geological Survey Special Publication No. 36.

Petuch, E. J. 1986. The Pliocene Reefs of Miami: Their Geomorphological Significance in the Evolution of the Atlantic Coastal Ridge, Southeastern Florida, U.S.A. Journal of Coastal Research 2(4):391–408.

Petuch, Edward J. 1987. The Florida Everglades: A Buried Pseudoatoll? Journal of Coastal Research 3(2): pp. 189-200.

Petuch, Edward J. 2004. Cenozoic Seas. CRC Press.

Petuch, Edward J. 2007. The Geology of the Everglades and Adjacent Areas. CRC Press.

Weisbord, Norman E. 1974. Late Cenozoic Corals of South Florida. Bulletins of American Paleontology 66 (285) 544 pp.



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Another excellent contribution! That day was certainly a scorcher, but well worth it.

Don

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Mike, I always thoroughly enjoy your blog presentations. Your documentation ethic and research serve as an example for fossil-related articles. Thank you for taking the time to share your project.

John

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