GeologyRocks

Quaternary

The subdivision of the Cenozoic era. The period spans 1.8Ma to the present day.

Epochs:

• Holocene 10,000Ya - Present day
• Pleistocene 1.8Ma - 10Kya

Rare Earth Elements

Elements with atomic numbers 57 (Lanthanum) to 71 (Lutetium) inclusive plus scandium and yttrium.

Regolith

Loose material, such as dust and rock fragments, covering bedrock.

Regression

A lowering of sealevel observed in the geological record. See trangression.

Relative Age

The age of a rock or formation given relative to other rocks or formation, usually defined as a zone fossil name. See also Absolute age.

Relative sea level change

A local sea level change caused by a combination of global (eustatic) and local (isostatic) changes. This is the sea level variation "recorded" by the rock record.

Rille

A channel (sinuous rille) or trench like feature (linear or arcuate rille) on the surface of the Moon.

Rima

Latin word used to name rilles on the Moon (pl. rimae).

Sequence stratigraphy

Sequence stratigraphy is a branch of geology that attempts to link relative sea-level changes to sedimentary deposits. The essence of the method is mapping of strata based on identification of time lines, such as unconformities, maximum flooding surfaces and transgression surfaces. In doing so it places stratigraphy in chronostratigraphic framework.

Silurian

A geological period; the third of the Paleozoic Era from 443 to 416Ma. The fossil record from this period includes a huge variety of marine fossils, land plants and early invertebrate land animals.

Epochs:

• Prídolí 418-416Ma
• Ludlow 422-418Ma
• Wenlock 428-422Ma
• Llandovery 443-428Ma