Jet Age Meets Ice Age: The Mammoth, Camel and Horse Fossils of Big Cypress's Jetport

In the late 1960s and early 1970s, work on a proposed jetport in the Big Cypress Swamp, just north of Everglades National Park, dug into Ice Age sediments — and turned up bones of mammoths, camels and horses. The site now lies inside Big Cypress National Preserve.

The small collection was all but forgotten until 2019, when NPS paleontologist Justin Tweet, doing research, found records of it in the Florida Museum of Natural History in Gainesville. In February 2023, NPS Senior Paleontologist Vincent Santucci visited the museum to inventory and photograph the fossils and learn their history.

The jetport fight

As Florida's population and tourism grew, planners in the 1960s proposed the world's largest jetport north of Everglades National Park — sited partly to take supersonic passenger jets, then thought to be the future of flying.

Dr. Luna B. Leopold. NPS photo

Conservationists — among them Marjory Stoneman Douglas and Dr. Luna B. Leopold, a senior hydrologist at the U.S. Geological Survey and son of conservationist Aldo Leopold — fought to protect the Everglades and Big Cypress Swamp and helped stop the jetport. Leopold coordinated the 1969 Environmental Impact of the Big Cypress Swamp Jetport, which set out the scientific case against it.

The cover of the 1969 environmental impact report. NPS image

The campaign also raised public and political awareness of these fragile ecosystems. On October 11, 1974, Big Cypress National Preserve was established — the first national preserve in U.S. history.

Where the bones lay

Before the preserve existed, one of the six planned runways was built. Crews dug a borrow pit on its south side for fill, and the workers hauling the sediment began to notice fossil bones and teeth.

• Bedrock: the Tamiami Formation, Late Miocene to Pliocene, widespread in southwestern Florida.
• The fossil layer: reworked Tamiami rocks described as the Fort Thompson Formation, in a river-channel deposit of land-derived sand, pebbles and limestone — interpreted by Curtis McKinney (1977) as an Ice Age stream valley.
• The sequence: rounded cobbles, oyster shells and bones at the base, grading up to fine-grained limestone at the top. McKinney read it as built up under a rising water table; since the site is only a few feet above sea level, it may record the sea advancing as sea level rose.

The fossils

Most bones found at the site were not saved and are considered lost, according to McKinney. A small Florida Museum of Natural History team, including McKinney, then a graduate student, did field work and collected fossils over several years in the early 1970s.

The museum's website lists six specimens from the site. Little information came with them, but the site was dated to the Pleistocene by the presence of the mammoth Mammuthus. The rest are typical Pleistocene animals: camels, horses, canids and tortoises. They are mostly isolated, partial bones and tortoise shell fragments, many identifiable to genus, and part of the collection was still uncatalogued.

Partial femur of a Pleistocene camel, Florida Museum of Natural History UF 543889. NPS photo

Partial skull of an extinct horse (Equus sp.), UF 543900. NPS photo

Partial lower jaw of an extinct horse (Equus sp.), UF 543891. NPS photo

What next

Ice Age vertebrate fossils are uncommon in Florida's southern tip, south of Interstate 75, so the collection deserves more study. Identifying the animals more precisely would pin down its age and may shed light on the Pleistocene ecosystem of the southwestern Florida peninsula.

Sources

Based on Vincent L. Santucci and Justin Tweet, "A Glimpse into the Pleistocene Paleoecosystem of Big Cypress National Preserve," Park Paleontology News 15, no. 2 (Fall 2023), NPS Geologic Resources Division, National Park Service, citing Leopold and Marshall (1969), McKinney (1977) and DuBar (1991); a work of the United States government in the public domain. A 1972 Polaroid from the Florida Museum of Natural History and a cross-section drawing from McKinney's 1977 University of Florida thesis are not reproduced.