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An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the ...
Hutton's Unconformity is a name given to various notable geological sites in Scotland identified by the 18th-century Scottish geologist James Hutton as places where the junction between two types of rock formations can be seen. This geological phenomenon marks the location where rock formations created at different times and by different ...
The Torridon Group infills an irregular land surface with up to 600 m of topography locally, cutting down through the previously deposited Stoer group sediments, resting in many areas directly on the Lewisian. It has been suggested that there is significant unconformity within this group, between the Diabaig and Applecross Formations. [4]
Close-up of Apollo Temple showing angular unconformity between Tonto Group and Unkar Group Major unconformities separate the Unkar Group from the strata overlying and underlying it. First, the Unkar Group, as the bottom unit of the Grand Canyon Supergroup, lies directly upon deeply eroded granites , gneisses , pegmatites , and schists that ...
Hutton's Unconformity at Jedburgh. Above: John Clerk of Eldin's 1787 illustration. Below: 2003 photograph. Uniformitarianism, also known as the Doctrine of Uniformity or the Uniformitarian Principle, [1] is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the ...
Little is known about the history of the oldest exposed rocks in the area due to extensive metamorphism.This somber, gray, almost featureless crystalline complex is composed of originally sedimentary and igneous rocks with large quantities of quartz and feldspar mixed in. [1] The original rocks were transformed to contorted schist and gneiss, making their original parentage almost unrecognizable.
Hutton's angular unconformity at Siccar Point where 370-million-year-old Devonian Old Red Sandstone overlies 435-million-year-old Silurian greywacke. [2]Old Red Sandstone, abbreviated ORS, is an assemblage of rocks in the North Atlantic region largely of Devonian age.
Geologists define schist as medium-grained metamorphic rock that shows well-developed schistosity. [3] Schistosity is a thin layering of the rock produced by metamorphism (a foliation ) that permits the rock to easily be split into flakes or slabs less than 5 to 10 millimeters (0.2 to 0.4 in) thick.