Fossils and Geologic Time Topics

Fossil Basics (Part 1)

• A fossil is a life form or evidence of a life form preserved in an ancient rock.

Life form means that fossils can contain all or part of any plant or animal that has existed during earth’s history.

Evidence of life means that fossils can be traces of plant or animal activity, such as tracks, trails, burrows, or coprolites (fossil excrement).  These traces are called ichnofossils.

Ancient means that fossils must be in rocks 10,000 years old or older.

Shark tooth and fish
Shark tooth (left) and fish fossil (right) (Photographs by Parvinder Sethi)

Fern (Photograph by Parvinder Sethi)

Fossils are traces of life preserved in ancient rock.  These fossils are remains of a shark (above left), a fish (above right), and a fern (right). 





Trails and footprints
Left: trails (photograph by Parvinder Sethi); right: dinosaur footprints (photograph by the Virginia Division of Geology and Mineral Resources)

Ichnofossils are traces of plant or animal life.  The left photograph shows grazing trails.  The right photograph shows dinosaur footprints in a quarry near Culpeper.