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Vocabulary • Fossil • Molds and Casts • Films • Mineral replacement • Amber • Brachiopod • Trilobite • Dinosaur • Index Fossil
Fossils • Fossils are cool little pictures to our past. • To be a fossil it must: • Once been alive • Now Dead • Buried in sediment • No longer of interest to bacteria.
Methods of fossilization • Fossils form many ways. Things die and then weathering, Erosion and deposition take over. • Ways to make a fossil: • Molds and Casts • Films • Mineral replacement • Amber
Molds & Casts • Organisms buried in sediment decay away leaving a cavity or mold. If the space is filled with sediment, a cast is made. • A mold preserves a negative imprint of the surface, while a cast preserves the external form of the organism.
Films • Imprints of leaves and seed cones are so perfectly preserved that minute details are visible through modern microscopes.
Mineral Replacement • Sometimes a shell can be filled with minerals and then dissolve away. • Ground water carrying dissolved minerals infiltrates the microscopic pores and cavities in bone, wood or shell.
Amber • Amber is tree sap that drips from conifers (Pines.) • This sap drips unto insects below it trapping the insect in the sap. • The sap eventually turns rock hard and the insect remains are forever preserved in the amber.
Types of fossils you need to know. • Brachiopods – aka old clams • Trilobite – looks like an old cockroach • Dinosaurs – Big lizards • Plants • Snails – Look like today’s snails
Index Fossils Index Fossil A fossil of an animal that lived all over the worldanddidn’t live that long. Humans (so far): Time lived________ worldwide? Yes / No Dinosaurs: Time lived________ worldwide? Yes / No
Types of index fossils • Bottom of ESRT 8/9 all good index fossils.
Tracks • We can see today fossil footprints. • Even in NYS there are places where Dinos roamed. • If you look at the tracks you can see what it was doing.
How do we use Index fossils • Relative dating • Correlations