In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcaniclava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet.
Certain mafic and ultramafic layered intrusions are a variety of sill that often contain important ore deposits. Precambrian examples include the Bushveld, Insizwa, and the Great Dyke, complexes of southern Africa, the Duluth intrusive complex of the Superior District, and the Stillwater intrusive of the United States. Phanerozoic examples are usually smaller and include the Rum peridotite complex of Scotland and the Skaergaard intrusive of east Greenland. These intrusives often contain concentrations of gold, platinum, chromium, and other rare elements.
SILL, in geology, an intrusive mass of igneous rock which consolidated beneath the surface and has a large horizontal extent in comparison with its thickness.
The rocks in which it lies belong to the Carboniferous Limestone series, and the Sill is probably one of the manifestations of the volcanic activity which occurred during the later part of the carboniferous period.
These sills are harder and more resistant than the tuffs and vesicular lavas, and on the hill slopes their presence is often indicated by small vertical steps, while on the cliff faces their columnar jointing is often very conspicuous.
Sills, Beverly (1929-2007), American soprano, who combined critical success with international popularity as a result of her clear, supple...
In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the...
The site of Fort Sill was staked out on January 8, 1869 by Maj. Gen.
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