Geologic Time & Fossils Flashcards
The objective is to learn the vocabulary of this unit.
Angular Unconformity
An unconformity in which younger strata overlie an erosion surface on titled or folded layer rock.
Cenozoic Era
The most recent of the eras; followed the Mesozoic Era.
Correlation
In geology, correlation usually means determining time equivalency of rock units. Rock units may be correlated within a region, a continent, and even between continents.
Cross- Cutting Relationship
A principle or law stating that a disrupted pattern is older than the cause of disruption.
Disconformity
A surface that represents missing rock strata but beds above and below that surface are parallel to one another.
Eon
The largest unit of geologic time.
Epochs
Each period of the standard geologic time scale is divided into epochs.
Eras
Major subdivision of the standard geologic time scale.
Formations
A body of rock of considerable thickness that has a recognizable unity or similarity making it distinguishable from adjacent rock units. Usually composed of one bed or several beds of sedimentary rock, although the term is also applied to units of metamorphic and igneous rock. A convenient unit for mapping, describing, or interpreting the geology of a region.
Fossil
Traces of plants or animals preserved in rock.
Faunal Succession
A principle or law stating that fossil species succeed one another in a definite and recognizable order; in general, fossils in progressively older rock show increasingly greater differences from species living at present.
Half- Life
The time it takes for a given amount of a radioactive isotope to be reduced by one- half.
Index Fossil
A fossil from a very short- lived species known to have existed during a specific period of geologic time.
Isotope
Atoms (of the same element) that have different numbers of neutrons but the same number of protons.
