Fossils Fossil: Any evidence of prehistoric life forms or environments Often found in sedimentary rock layers (sandstone or shale)

Shale deposits in the Grand Canyon

Fossil-bearing sandstone and shale strata near Blewett Pass, Washington

Badlands, South Dakota

Paleontologists excavating a prehistoric watering hole in Badlands

Types of Fossils: 1.Petrified Remains hard, rocklike remains usually bones or wood

2. Molds and Casts Mold: organism decays but leaves behind an imprint in sediments Cast: Other sediments fill in the imprint and harden

3. Carbonaceous Films Heat and pressure push down on the organism leaving behind carbon residue

4. Original Remains Actual preserved parts of organisms Preserved in: –amber (crystallized sap) –frozen ground –tar pits

5. Trace Fossils Fossilized tracks Worm “tracks” Ripple marks from water waves

Index Fossils

Species that existed for a short period of time Were abundant Were widespread geographically Used to determine the ages of rock layers

Index Fossil Correlation

Fossil Lab (in notebook) Make detailed drawings of five different kinds of fossils from the specimens in class Drawings must be at least 12 cm long (you may need to use a microscope for some specimens) Label each drawing Tell what type of fossil each is (cast, petrified, etc.) For at least three of your specimens, give the time when the organism existed on Earth