The Probability of Life - Creationists have long asserted that the chances of life forming naturally are so remote that they could not have happened.
The polarity timescale has been previously determined by dating of seafloor magnetic anomalies, radiometrically dating volcanic rocks within magnetostratigraphic sections, and astronomically dating magnetostratigraphic sections.
Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloguing and comparing fossil floral and faunal assemblages.
Biostratigraphy does not directly provide an absolute age determination of a rock, but merely places it within an interval of time at which that fossil assemblage is known to have coexisted.
Tephra is also often used as a dating tool in archaeology, since the dates of some eruptions are well-established.
It is important not to confuse geochronologic and chronostratigraphic units.