Geology 101 Chapter 9

Daughter isotope

the compound remaining after the parent isotope

Disconformity

A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition

Trace Fossils

A fossil of a footprint, trail, burrow, or other trace of an animal rather than of the animal itself.

Nonconformity

A 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

Parent isotope

A parent atom refers to the atom that undergoes radioactive decay in a nuclear reaction.

Angular Uncomformity

An angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers

Isotopes

Aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements.

Fossil Succession

Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content.

Sources of radiometric error

Radiometric correction is to avoid radiometric errors or distortions

Numerical Age Vs. Relative Age

Relative age is the age of a rock layer (or the fossils it contains) compared to other layers. It can be determined by looking at the position of rock layers. Relative age is the numeric age of a layer of rocks or fossils.

Original Horizontality

States that layers of sediment are originally deposited horizontally under the action of gravity

Cross-Cutting

States that the geologic feature which cuts another is the younger of the two features. It is a relative dating technique in geology.

Hadean

The earliest time interval (eon) of Earth history. The time before the planet's first rocks.

Proterozoic

The eon following the Archean and preceding the Phanerozoic. It extends between 2500 and 542 million years ago.

Archean

The first eon of Precambrian time. The eon preceding the Proterozoic. It extends between 4.5 and 2.5 billion years ago

Body Fossils

The most common type of fossil found across the world. They are formed from the remains of dead animals and plants

Phanerozoic

The part of geologic time that is represented by rocks containing abundant fossil evidence. The eon extending from the end of the Proterozoic eon (540 million years ago) to the present.

Inclusions

The principle of inclusions states that inclusions found in other rocks (or formations) must be older than the rock that contain them.

Lateral Continuity

The principle of lateral continuity states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous.

Superposition

The principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest

Fossilization

The process of becoming a fossil

Half-life

The time it takes for one-half of a radioactive element to decay into a daughter isotope