Les Sirkin, a geologist from Adelphi University, visited the island in the late 1980s as a part of the archeological dig project. He thought that the Navy bluffs made up of sand and clay layers were a fine example of a kame. His special thing was the study of sediments, especially pollen grains. Each type of plant has its own special pollen grain. During the growing season it is plentiful. My doctor told me that there is plenty of it in the air right now. It also can last a very long time. Thus in sediment, pollen of ancient plants can be found and identified. Sediment can also be dated using an isotope of carbon, carbon-14. Sirken can tell which plant a particular pollen grain came from and when. The kinds of plants that lived at different times can be known. We can get an idea of what kinds of plants lived through the ages on Fishers Island and the climates in which they lived.
In 1990, we began a study of the flora of the island. Gordon Tucker in his research came upon the work done by Margaret B. Davis in 1969 in the sediments at the bottom of a lake only a few miles northwest of Fishers Island. The lake is between Lyme and Old Lyme. I will quote what Gordon wrote.
During the Pleistocene, all vegetation in southern New England and Long Island was obliterated as a continental ice sheet 1-2 km thick covered the region. The terminus of the ice sheet reached Montauk Point and Block Island. All native plants were displaced southward by cooler climate and gradually reentered our area as the land was exposed and the climate warmed. Palynology determines the sequence of events from analysis of sediments containing pollen, preserved in lakes and bogs, based on the theory that abundance of pollen in sediments is reflective of local or regional abundance of species. The work of Davis (1969) carried out in Rogers Lake shows the postglacial development of vegetation in our area.
Boreal, tundra-like vegetation dominated the period from 14,300-12,150 years B.P. [Before the Present]. The pollen train was characterized by willows, grasses, sedges, and herbs.
This was followed by a zone dominated by spruce with tamarack and fir from about 11,700-9,100 B.P. indicative of a boreal forest cover similar to that now found in northern New England and eastern Canada.
This was followed by a white pine period from 7,900-8,100 B.P. during which time red maple and hemlock first appear.
Oak and hemlock dominate from about 8,000 to perhaps 5,000 years B.P. during which time (6,000) beech appears.
Hemlock declined greatly in abundance about 4,800 B.P. in Connecticut and the Northeast.
Oak-hickory forest the present dominate of our area.
Chestnut appears only 2,000 years ago.
The most recent sediments of the last 300 years contain abundant herbaceous pollen (especially Ambrosia and Rumex) paralleling the extensive clearing of land and development of agriculture in Colonial times.
The study of pollen in sediments has enabled us to know the kinds of plants that grew in a locale such as Fishers Island long, long ago shortly after the island came into being. It also tells us that through time the kinds of plants changed as did the climate. Some of the early types are still on the island today. Sedges, grasses, willows, spruces, all that thrive in cooler climates are still here, but now through time other types have joined them and have replaced some of them.