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The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks).
The North American land-mammal-age system was formalized in 1941 as a series of provincial land-mammal ages. [2] The system was the standard for correlations in the terrestrial Cenozoic record of North America and was the source for similar time scales dealing with other continents.
The geologic turmoil on the west coast was maintained as the Pacific Plate continued to slide under the North American Plate. [133] During the early part of the Cenozoic period climates were much warmer than they are today. Latitudes as high as South Dakota had a subtropical climate until as recently as the end of the Oligocene. [134]
(Click to zoom) See legend below This is the legend for the North American geological map above. Geologic map of North America. The geology of North America is a subject of regional geology and covers the North American continent, the third-largest in the world. Geologic units and processes are investigated on a large scale to reach a ...
The geological timeline of Western North America includes significant geological events over millions of years in the evolution of Western North America, including several tectonic plate interactions involving the North American plate and leading to the formation of various mountain ranges and seaways.
Geologic time shown in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events The geological history of the Earth follows the major geological events in Earth's past based on the geological time scale , a system of chronological measurement based on the study of the planet's rock ...
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition.A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.
A cratonic sequence (also known as megasequence, Sloss sequence or supersequence) in geology is a very large-scale lithostratigraphic sequence in the rock record that represents a complete cycle of marine transgression and regression on a craton (block of continental crust) over geologic time. They are geologic evidence of relative sea level ...