Trip 2, (6 hours)- LaBelle, FL, 7/6/14 Caloosahatchee River marl (Plio-Pleistocene boundary)
Caloosahatchee River about 3/4 way down Florida West coast running from Fort Myers east to Lake Okeechobee with the small town of LaBelle about half way in between.
The fossil fauna found here is from after a regression that left the Everglades basin well above sea level for several hundred thousand years before being flooded once more by a global warm spell in the late Pliocene-Early Pleistocene. The shallow inland lagoon that formed was superheated resulting in a truly tropical environment much different than that found along the Atlantic coast of the time. In the Caloosahatchee Formation along with molluscs are found vertebrates, echinoids and corals; the molluscs here are larger and more abundant then in other contemporary areas due to the warmer and more fertile microfauna.
In the south-western area of southern Florida are many quarries where the Caloosahatchee limestone phosphate zones are mined for lime and many collectors hit the spoil piles for specimens. Since Annea and I had collected loose specimens of Miocene shark's teeth 3 days before, I wanted to take her to the type locality where the fossils were in situ in the marl. Plus I could add to my expanded mollusca collection and Annea could grab samples for her microfossil studies.
University of Florida, Florida University, and Tampa University conduct many field trips along the Caloosahatchee River (which is the type locality for the formation) for both geology and biology classes, and it is a popular stop for local and out of state fossil collectors.
We rented a canoe from the Labelle canoe outpost and headed towards several areas of exposures we had been informed of, passing up various "shell beaches" of eroded out free specimens until we found one of the exposed deposits about a mile west of Labelle.
Using a shovel and trowl to carefully dig the crumbly limestone we washed the sediment in the river in 12x12 inch screens of 1/8 and 1/4 mesh, along with careful digging out with spoons & probes larger specimens. Annea filled baggies with raw sediment at 4 inch intervals to eventually process for microfossils with what should be an abundance of foraminifera.
Spot identification on site we found at least 10 species of coral, 55 of bivalves, 3 of scaphopods, 85 of gastropods, 3 of echinoids, and various specimens of crab, barnacles, obvious vertebrate bone fragments (vertebrates we gave away to a local group we met on the way back to LaBelle that had the required permit to collect vertebrates other then shark teeth): all of this just a small portion of the more than 500 recorded species for the marl. Definitely will come back during winters as a respite from the snow and cold to look for species we don't have; (will get the state permit this time since layers above the marl are know for uncommon Ice Age land mammals such as sabertooth, sloth, mastodon, mammoth teeth and such).
We mailed home for eventual cleaning, sorting and identification: six 12 inch bags stuffed with non-delicate marine fossils in matrix, two 18x18x9 boxes of bubble wrapped larger delicate specimens and a hundredi or so smaller ones we had cleaned at the hotel. Busy fall & winter ahead!
Ended the day with a dinner for 2 of Boiled shrimp, Louisiana style at the hotel pool in Ft. Myers. Tomorrow was going to be a more traditional tourist day at Busch Gardens amusement park & zoo then relaxing & sightseeing for 2 days before flying the 7th to US Virgin Islands for annual 2 week university field trip.
Nice break from the usual much harder rock Paleozoic formations we both usually work with!
24) Caloosahatchee river marl eroded fossil beach, half mile east of LaBelle, FL. 7-4-14