WORDPLAY WEDNESDAY: STRATIGRAPHY
Stratigraphy is an important piece of vocabulary for paleontology. It is a branch of geology concerned with the relative position of strata (rock layers) and their relationship to the geologic time scale. It is primarily used for sedimentary and igneous rocks (metamorphic rocks don't tend to layer).
Nicolas Steno, a Catholic priest, established the basis for stratigraphy by introducing the Law of Superposition, the Principle of Original Horizontality, and the Principle of Lateral Continuity.
In other words, all rocks are deposited horizontally,
are laterally continuous,
and the oldest rocks are on the bottom.
There are three major branches of stratigraphy: lithostratigraphy, biostratigraphy, and chronostratigraphy.
Lithostratigraphy looks at the variations in lithology (physical characteristics of rocks) such as vertical and lateral bedding, and reflects changes in depositional environment (river, lake, desert).
Biostratigraphy correlates rock layers using fossils. This is based off of William Smith's Principle of Faunal Succession.
wherein fossils flora and fauna succeed each other in vertical layers and can be found over wide horizontal distances.
Lastly, there is chronostratigraphy which aims to put an absolute date (an actual number) rather than a relative date on rock strata. This means we can tell you where on the geologic time scale a formation belongs as shown below.
I personally love stratigraphy. It involves a lot of rigorous outdoor adventuring including hiking, mapping, drawing, picture-taking, and sample collection. In fact, I am currently working on a stratigraphic paper for our Evil Tree Bonebed. It's taken a few years but we should be done soon! I'll share when we are finally published!
