Strat and Age Dating Flashcards
The Precambian time is broken into three parts…
Hadean, Archean, Proterozoic
The Phanerozoic time is broken into three eras…
Paleozoic, Mesozoic, Cenozoic
“The Father of Modern Geology”; the first to articulate the Principle of Uniformitarianism
James Hutton - The present is the key to the past.
The Principle of Uniformitarianism states…
processes observed today were the same in the past.
The Principle of Original Horizontality states…
sediments tend to accumulate horizontally.
The Principle of Superposition states…
an undeformed sequence of layered rocks, each bed is
older than the one above and younger than the one
below. Younger strata are on top; older strata are below.
The Principle of Lateral Continuity…
strata often form in laterally extensive horizontal sheets. Subsequent erosion dissects once-continuous layers.
The Principle of Cross-Cutting Relations
younger features truncate (cut across) older features. Faults, dikes, erosion, etc., must be younger than the material that is faulted, intruded, or eroded. (A volcano cannot intrude rocks that aren’t there yet.)
The Principle of Baked Contacts
an igneous intrusion cooks the invaded country rock. The baked rock must have been there first (it is older). A chill margin is formed within the igneous intrusion at the contact from rapid cooling.
The Principle of Inclusions
the occurrence of one rock fragment within another. Inclusions are alwaysolder than the enclosing material. Weathering rubble must have come from older
rock. Fragments (xenoliths) within an igneous intrusion are older
The Principle of Fossil Succession
the predictability of fossil distribution through time.
What is an unconformity?
a time gap in the rock record, from nondeposition or
erosion.
What are the three types of unconformities?
angular unconformity, nonconformity, and disconformity
horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers
Angular unconformity
What is an nonconformity?
where igneous or metamorphic rocks are capped by sedimentary rocks.
