[Pleistocene]—the first of the two epochs of the Quaternary [Period], and that which precedes modern time, known as the Great [Ice Age].
[Pliocene]—last and youngest [epoch] of the Tertiary [Period] of the [Cenozoic] [Era].
[Proterozoic]—youngest [era] of the Precambrian; follows the [Archeozoic] Era and precedes the Cambrian [Period] of the [Paleozoic] Era.
[Red beds]—a general term for red [sandstone], [shales], etc., which appear to characterize arid [periods] in the past.
[Ripple marks]—wave-like corrugations produced in unconsolidated materials by wind or water.
[Rock]—any natural aggregate of [mineral] matter, usually consisting of a mixture of two or more minerals.
[Sandstone]—[sedimentary rock] composed of cemented sand grains, usually quartz.
[Sediment]—material that has been deposited by settling from a transportation agent such as water or air.
[Sedimentary rock]—[rocks] formed by the accumulation of [sediments].
[Shale]—a [sedimentary rock] formed by the hardening of mud and clay and usually tending to split into thin sheets or layers.