Question

Which one of the following is a geochronologic unit?

• A. System
• B. Period
• C. Member
• D. Formation

Answer 1

The Correct Option is B

To determine which of the given options is a geochronologic unit, we need to understand the hierarchical classification of geological time.

Geochronology deals with the dating and understanding of events in Earth's history. The hierarchy of the geologic time scale begins with Eons, which are divided into Eras. Eras are further divided into Periods, then Epochs, and finally Ages.

In this context:

• Period: A Period is a fundamental geochronologic unit used to denote a specific interval of time in Earth's history. Therefore, it is the correct answer.
• System: This term refers to a chronostratigraphic unit rather than a geochronologic one. It represents the rocks deposited during a particular period.
• Member: This is a unit used in stratigraphy to subdivide formations into smaller layers. It is not a geochronologic unit.
• Formation: Another stratigraphic unit that is used to define a body of rock with distinct characteristics, but not related to time directly.

Hence, among the provided options, the correct answer is Period, as it is the only option that signifies a geochronologic unit.