Question

The correct combination(s) of ranks and corresponding categories of stratigraphic units is/are

• A. Formation – Lithostratigraphy
• B. System – Chronostratigraphy
• C. Period – Chronostratigraphy
• D. Group – Biostratigraphy

Hint:

In stratigraphy, formations are lithostratigraphic units, while systems, periods, and groups correspond to different categories of geological time and biostratigraphy.

Answer 1

The Correct Option is A, B

1. To answer this question, we need to identify the correct combination of ranks and categories of stratigraphic units. Let's review the key terms and concepts:
2. Lithostratigraphy refers to the study of rock layers (strata) and their distribution, arrangement, and sequential relationship. A Formation is a fundamental unit of Lithostratigraphy, defined by a distinctive set of rock layers that can be mapped over a large area.
3. Chronostratigraphy deals with the age and temporal relation of rock layers. A System and a Period are units of time and correspond to segments of geologic time. In Chronostratigraphy, a System is a ranking below Era but above Series.
4. Biostratigraphy involves the differentiation and correlation of rock layers based on their fossil content. The term Group is not typically a rank used in Biostratigraphy; rather, it is a category used in Lithostratigraphy, hierarchically above Formation.
5. Based on the definitions above, the correct combinations are:
   • Formation – Lithostratigraphy: Correct because Formation is a primary unit of Lithostratigraphy.
   • System – Chronostratigraphy: Correct because System represents a time-stratigraphic unit in Chronostratigraphy.
6. The other options:
   • Period – Chronostratigraphy is a term in Chronostratigraphy but corresponds to a slightly different concept of geologic time directly equivalent to what is known as a System in Chronostratigraphy.
   • Group – Biostratigraphy is incorrect because Group is used in Lithostratigraphy, not Biostratigraphy.
7. Therefore, the correct answer to the question is the combination of "Formation – Lithostratigraphy" and "System – Chronostratigraphy".