Maine's fossil record
Bringing the past to life
Every fossil has a tale to tell about a past life and the world in which it lived. Fossils are the remains of past life that have been preserved in sediments (such as clays and peats) or rocks (such as slates and sandstones). Just after the glacial retreat about 12,000 years ago, much of Maine was a treeless tundra that supported megafauna - large animals such as wooly mammoths, mastodons, saber-toothed cats and many others until about 10,000 years ago. After the ice melted, plants and animals returned, even though it was still extremely cold. Scientists have been amazed to discover nearly complete skeletons of large animals still preserved in lake muds and the "blue clay" from over 10,000 years ago.
Shells are the most common macrofossils in Maine's glacial-marine muds. This collection includes species of clams, mussels, scallops, barnacles and even a walrus toe bone. Some species still live on the Maine coast, while others typically inhabit colder North Atlantic waters. Photo courtesy of W.B. Thompson, Maine Geological Survey Organisms can be preserved in fossils in many different ways: positive or negative impressions, internal or external molds or by complete mineralogical replacement. A fossil may represent only one part of an organism, or perhaps it may preserve most of that organism's anatomy. Most fossils consist of hard body parts such as shells, teeth and bones, because these are the most resistant to weathering and have a good chance of surviving in the rock. Fossils of marine organisms have been found in the "blue clay" of the Presumpscot Formation. Invertebrate shells such as clams, mussels, snails and barnacles are the most common; however, fish and mammal remains also have been discovered. A mammoth that washed into the ocean as well as a walrus were also intriguing discoveries and are currently on display in the Maine State Museum.
Ray Webb holding the walrus toe bone found at his gravel pit in Prospect, Maine. The bone was buried in glacial-marine mud along with the sea shells shown in the accompanying photo.Covering a vast span of time, the fossils preserved in Maine's bedrock date from 500 to 360 million years ago; however, there is a gap in Maine's fossil record. The gap is from 360 million years ago to about 100 thousand years ago. There are no fossil-bearing rocks in Maine that have been dated to that period of time, and because of this, no dinosaur fossils have ever been discovered in Maine. As the glaciers melted and the sea flooded coastal Maine, sand and mud from the glaciers covered the sea floor, but the fossils that are preserved in this sediment are less than 16,000 years old.