Fossils Earth Science 11

A. How preserved… Fossil: A rock replica (usually) of the animal, etc. In sedimentary rocks only, shale mostly since finer particles can preserve small details better Then preserved by one of the following methods…

How preserved… 1. Molds and Casts – shell or bone in rock, dissolved leaving mold, other material fills in space making a cast.

How preserved… 2. Replaced remains – hard parts replaced by minerals in circulating solutions (ex petrified wood)

How preserved… 3. Carbonization – all the other elements disappear and a carbon imprint remains. (Typical of leaves)

How preserved… 4. Amber – hardened sap from pine trees, insects found in it (ex Jurassic Park)

How preserved… 5. Actual unchanged remains – usually only bones, but rarely, soft parts too (ex if frozen)

How preserved… 6. Trace fossils – tracks, burrows, poop, bite marks, etc preserved

B. Index fossil: Must be unique, easy to tell apart from others Found over a wide geographic area Was on Earth only a short time (in only a few rock layers) If above are true, then any time you see that fossil you know how old the rock is, no matter where the rock is.

C. Fossil phyla… 1. Mollusca – clams (pelecypod), snails (gastropod), ammonoid, etc

Fossil phyla… 2. Brachiopod – almost extinct, similar to clams

Fossil phyla… 3. Arthropod – trilobite(extinct), spider, crab, etc.

Fossil phyla… 4. Vertebrate – spines, people, fish, etc

Fossil phyla… 5. Echinoderm – 5-fold symmetry, star fish, sand dollar, etc

Fossil phyla… 6. Plants – live on land