Midterm 2 Stratigraphy

Walther's Law

Main idea: if you have a distribution of environments you can take the distribution of environments and predict what would happen as they shifted space

Principle of Superposition

Steno's Law A major principle of stratigraphy stating that within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence

Principle of Original Horizontality

Steno's Law Layers of sediment were originally deposited horizontally under the action of gravity any rock layers that are now folded and tilted have since been altered by later outside forces

Principle of Lateral Continuity

Steno's Law states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.

Principle of Cross-Cutting Relationships

Steno's Law younger features cut across older features

Nonconformity

exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.

Disconformity

exists where part of a sequence of parallel rock layers is missing

Stratigraphy

the branch of geology concerned with the order and relative position of strata and their relationship to the geological time scale. deals with the origin, composition, distribution, and succession of strata

Angular Unconformity

tilted rocks are overlain by flat-lying rocks