Paleontology relative dating
NSF Postdoctoral Research Fellow at Stony Brook University.
I study how bone tissue, growth, and metabolism evolve at macroevolutionary time scales.
Once the rocks are placed in order from oldest to youngest, we also know the relative ages of the fossils that we collect from them.
Relative age dating tells us which fossils are older and which fossils are younger. To get an age in years, we use radiometric dating of the rocks.
The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored or differently structured materials exposed in this cliff.
The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata. Such index fossils must be distinctive, globally distributed, and occupy a short time range to be useful.
Recall that most fossils are housed within sedimentary rock, which results from the compaction and cementation of deposited sediments.
They build up over time so that that the layers at the bottom of the pile are older than the ones at the top.
Current understanding of the history of life is probably close to the truth because it is based on repeated and careful testing and consideration of data.
The rejection of the validity of fossils and of dating by religious fundamentalists creates a problem for them: Fossil sequences were recognized and established in their broad outlines long before Charles Darwin had even thought of evolution.
Geologists call this simple observation the Principle of Superposition, and it is most important way of working out the order of rocks in time.
Ordering of rocks (and the fossils that they contain) in time from oldest to youngest is called .