GEO 303 Fossils

Mold

hollow cavity left in sediment after original fossil has dissolved

cast

mold is later filled with sediment

replacement

atom by atom replacement of organic matter by minerals

permineralization

void space in bone or teeth filled by minerals

body fossil

remains of a part of the organism

trace fossil

evidence of past life that doesn’t include organism itself

algal fruiting body

• spherical

• aragonite

sponge

• porous

• silica, calcite

• tube shaped

coral

• septae (solitary or colonial)

• calcite & aragonite

echinoid

• pentagonal symmetry

• calcite

• looks like a sand dollar

bivalve

• bilateral symmetry between x-axis

• calcite

• looks like an oyster

gastropod

• conical tube

• calcite

• mobile snails

ammonite

• coiled on horizontal plane

• calcite

• marine molluscs (giant shell)

brachiopod

• bilateral symmetry between y-axis

• calcite

• looks like a muscle

fusilinid

• resemble grains of rice or wheat

• calcite

leaf impression

• carbonaceous remains of plant material between fine layers

• liginin and cellulose

wood

• replacement of wood by silica

• lignin and cellulose

• bark structure

bone

• spongy inner bone structure

• calcium