Sometimes interesting scientific evidence shows up in unexpected places. Years ago, there had been discussion of the possibility that immediate post glacial climate in the North Atlantic coastal region was unusually warm, but the evidence was spotty. Then, I was looking through material taken from a geotechnical boring placed to assess the geology of a part of Boston Harbor where a new tunnel was being planned, and found a large fragment of a clam embedded in clay. The clay was deposited during the last glacial maximum and later, and was associated with the melting of glaciers in the region. As a matter of routine, I gave it to Russell Barber, a mollusk expert and, at the time, my boss. He identified it as a species of razor clam found these days no farther north than the Carolinas. And thus, yet another piece of spotty evidence!
Something similar happened in Florida just recently. Pollen from the mallow, primrose willow, gentian and other families was found in Eocene sediments (about 35 million years old). The sample was found over 760 meters below the surface and represents at least 17 species of terrestrial plants.
“So what?” you say? Well, 35 million years ago, what is now Florida was in the middle of one off those “ancient seas” we are always hearing about from geologists. This finding indicates that there was land nearby, possibly islands. Or, something else is … different than expected.
In the old days (say, 10 years ago or so) I might have suggested that the pollen could have come from land a very long distance away and transported here by wind, or even on the water’s surface. However, these days we have much better models of how “pollen rain” (as it is called) works, and when pollen is found in a particular deposit estimates can be made of how far away it came from. Some of this pollen came from insect pollinated plants. Compared to wind dispersed pollen, this sort of plant sperm is both rare and usually found near where it was produced.
This is the oldest flora yet described for Florida.
Jarzen, David, & Klug, Curtis (2010). A preliminary investigation of a lower to middle Eocene palynoflora from Pine Island, Florida, USA Palylnology, 34 (2), 164-179 : 10.1080/01916121003737421