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The basement rock of the crust can be 32–48 kilometres (20–30 mi) thick or more. The basement rock can be located under layers of sedimentary rock, or be visible at the surface. Basement rock is visible, for example, at the bottom of the Grand Canyon, consisting of 1.7- to 2-billion-year-old granite (Zoroaster Granite) and schist (Vishnu ...
Simplified geologic map of Kalimantan (Borneo) Island Map of Borneo and surrounding features. Made using GeoMapApp. The basement rock of Borneo is a complex mosaic of geologic terrains, commonly interpreted as the product of primarily Mesozoic accretion of micro-continental fragments, island arc material, oceanic crustal material and marginal basin fill onto the Paleozoic core of the Schwaner ...
The Vishnu Basement Rocks underlying this surface are often deeply weathered to an average depth of 3 m (9.8 ft) below it. Where it has not been removed by erosion, prior to, and during the deposition of the overlying Bass Formation, a residual regolith developed by subaerial weathering of the underlying basement rocks – is present. Typically ...
The age and exhumation history of the underlying Vishnu Basement Rocks constrain the age of the Unkar Group. Radiometric dating of these basement rocks demonstrate that these basement rocks underwent metamorphism and deformation at mid-crustal depths of about 20–25 km (12–16 mi) between about 1840 and 1660 Ma ago.
The Vishnu Basement Rocks is the name recommended for all Early Proterozoic crystalline rocks (metamorphic and igneous) exposed in the Grand Canyon region. They form the crystalline basement rocks that underlie the Bass Limestone of the Unkar Group of the Grand Canyon Supergroup and the Tapeats Sandstone of the Tonto Group. These basement rocks ...
Throughout the majority of it extent, the Tonto Group lies unconformably on underlying Precambrian rocks forming the Great Unconformity. This contact is either an angular unconformity truncating tilted strata of the Grand Canyon Supergroup or a nonconformity cut into the crystalline Vishnu Basement Rocks. The base of the Tonto Group consists of ...
At places throughout the Alps the European basement was, after being detached of its cover rocks, tectonically uplifted in a late stage of the orogeny. Thus the "external massives" were formed, places where the Hercynian basement rock crops out in large anticlinoria at the southern (or in France eastern) side of the Helvetic zone.
Some international dating work around 1973 indicated that most basement rock in North Korea dates to the Proterozoic or the earlier Archean.The North Kyangsong Province gneiss samples indicated ages to 2.12 billion years ago and in 1985, the Sangni Metamorphic Supergroup and the Sangni Revolution were proposed as names for the gneiss-schist and gneiss formation.