Looks like point of impact of meteor many moons ago.
When I was a kid I used to wonder why geodes were found around Tampa Bay. Certainly Fla was never volcanic or igneous.
Years later it was established a meteor had hit Earth near what is the Yucatan Peninsular.
That map sure looks like the spot.
Hmmm, just noticed the latitude. Much farther N. than Yucatan.
Miami is approx 25 3/4º.
27º would be W of Sarasota, Ft. Myers
Tampa is 28º