Ch. 17 Quiz

concurrent range zones

established by plotting the overlapping ranges of two/more fossils with different geologic ranges

guide fossil

fossil used in the con-current range by charts

fossil succession

fossils at the bottom are older

inclusions

fragments of one rock in a layer of another are older than the rock layer itself

easily identified, widespread, short geologic range

guide fossils meet three criteria:

fossils and the principle of fossil succession

how do geologists correlate rock units over large areas

use decay rates of unstable isotopes

how do geologists use radiometric dating to determine the absolute age of rocks?

cross cutting relationships

igneous intrusion/fault, younger than the rocks it cuts through

angular unconformity

layers above and below unconformity have different orientation

disconformity

layers above and below unconformity have the same orientation

stratigraphy

mapping of the rock layers, focuses on composition, origin, age relationships, geographic extent

lithostratigraphic correlation

matches up the same rock units over a larger area with no regard for time

relative

placing events in order by their position in the geologic record, doesn't say how long ago an event took place just that one event came before another

absolute

provides specific dates for events expressed in years, radiometric dating

lateral continuity

sediment extends laterally until it thins or ends along basin edges

original horizontality

sediment is deposited in horizontal layers

superposition

sedimentary rock layers have oldest on bottom, youngest on top

unconformities

sequences of strata, represent times of non deposition, gap in geologic record, incomplete rock record

no, isotopes are too short lived

could geologists use radiocarbon dating to date very old rocks?

nonconformity

cut into metamorphic or igneous rock and covered by sedimentary

lithostratigraphic unit and biostratigraphic unit

defined by content

time stratigraphic correlation

demonstrates time equivalence of events, can use fossils to show time equivalence

uniformitarianism

the same processes seen today have operated over vast amounts of time, can't interpret the rock record without this principle

time-stratigraphic unit and time unit

those expressing/related to geologic times

igneous and metamorphic

which types of rocks can be radiometrically dated?

rock layers don't extend indefinitely

why can't geologists rely on lithostratigraphic correlation to demonstrate time equivalence when mapping large areas?