Time Stratigraphic Unit Definition A Time Stratigraphic Unit, or a Chronostratigraphic Unit, is a rock unit that is characterized by geological formations, during a specific period of time. This serves as a reference for all rocks formed during the same time period.

Facies Facies: In the field of geology, the term “facies” represents a mappable, areally restricted part of a rock body that has different fossils or lithology from other contiguous beds deposited at the same time.

“Test” Definition in Paleontology In the field of paleontology, a subsidiary of geology, the term “test” refers to the external hard part of an invertebrate.

Volcanic Rock (Igneous) Definition A “Volcanic Rock” is an igneous rock that is finely crystalline and glassy (or aphanitic). To illustrate, volcanic rocks result from volcanic action at the earth’s surface. Typically, this also includes igneous intrusions that are “near-surface,” which may otherwise be considered plutonic. This action results in a final rock that is…

Silicates Definition In the fields of geology and mineralogy, the term “silicates” refers to compounds whose crystal structure contains SiO4 tetrahedra. Silicates are either isolated or joined to form groups, rings, single or double chains, sheets, or three-dimensional frameworks.