Dino Bio: fossilization, dating, geologic time
Terms
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- fossil
- any trace of past life
- igneous rock
- formed when hot, liquid rock cools (either magma or lava)
- metamorphic rock
- forms below the surface of the Earth, under conditions of high temperature and pressure; it's always denser than before
- sedimentary rock
- forms at or near the surface of the Earth under normal temperature and pressure
- formation of sedimentary rock
- process: erosion, transport, deposition, lithification
- rock cycle
- any rock can be transformed into any other rock
- sedimentary structures
- traces showing environment in which sedimentary rock formed: ripple marks, mud cracks, sole markings
- Principle of Superposition
- in any undisturbed sequence of sediment, the oldest will be on the bottom
- Principle of Uniformitarianism
- "the present is the key to the past"
- Principle of Faunal Succession
- certain animals are time and place specific
- fossil record
- history of preserved life in a rock
- fossils are biased
- only hard parts are fossilized (bone); fossilization favors animals from depositional environments; small, fragile animals aren't preserved as much
- still might not be preservation
- sediment might not lithify
- where to find fossils
- look for exposed bone in layers of sediment; look for certain dinosaurs in rocks of a certain age
- permineralization
- water carrying minerals comes through the sediment, filling holes in the bones with the minerals
- petrification/replacement
- organic material in the bone dissolves and is replaced by minerals
- soft-structure preservation
- (incl. eggs) {freezing, drying, pickling and tanning (peat bogs)}, amber, and tar. {only recent fossils: past 20 thous years}
- mold
- negative impression
- cast
- if the mold gets filled in and preserved
- trackways
- fossilized footprints
- gastroliths
- fossilized stomach stones: from gizzards (chickens and sauropods)
- coprolites
- fossilized feces; shows size, diet, and environmental details
- what we do/don't know
- do: size, morphology, time period, location, diet, synapomorphies, ecology, and behavior; don't: color, sounds, and social interactions
- what are we dating?
- the rock, not the fossil
- relative dating
- age in relation to something else
- biostratigraphy
- finding sequences of fossils in rocks (with superposition and faunal succession)
- absolute dating
- gives dates in years
- tree-ring dating
- only recent things
- carbon-14 dating
- organic material, but only up to 20-30 thous years old
- radiometric dating method
- date igneous rock through radioactive decay (half-life)(because igneous sets half-life at zero)
- eras
- {Cenozoic, Mesozoic, Paleozoic}, Precambrian; {Phanerozoic}
- Cenozoic Era
- 65 million years to current
- Mesozoic
- 245 million years to 65 million years; Cretaceous, Jurassic, Triassic
- Paleozoic
- 570 million years to 245 million years