Paleontology and geology
The Precambrian: Precambrian metamorphic rocks cover much of Connecticut. No fossils are found in these rocks.
The Paleozoic: No Cambrian rocks are found in Connecticut, and all later Paleozoic rocks in the state are igneous and metamorphic. No fossils have been identified from these rocks.
The Mesozoic: Exposures of Triassic and Jurassic sedimentary rocks can be seen in the Connecticut River Valley in the central part of the state. These rocks were originally deposited as sediments in alluvial fans, braided streams, and lakes that filled rift valleys. The rifting occurred as the supercontinent of Pangea began to pull apart. Trace fossils of invertebrates, and fossils of both plants and dinosaurs are found within these sediments. Dinosaur footprints also occur in some of these rocks. No Cretaceous rocks are known from Connecticut.
The Cenozoic: No Early Cenozoic (Tertiary) rocks are known from Connecticut, however, Quaternary sediments were deposited as vast ice sheets advanced over the state. Fossils from this time period are found along the coast of Connecticut’s Long Island Sound and in the northwestern part of the state and include marine invertebrates, such as clams, snails, and crustaceans. Many of these fossils are from animals very similar to those of today.