RFG 2018 Conference

GeoWord of the Day

The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.

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macphersonite (mac-pher'-son-ite). A pale amber, colorless or white orthorhombic mineral: Pb4(SO4)(CO3)2(OH)2 . It is a polymorph of susannite and leadhillite.

weir . (a) A small dam in a stream, designed to raise the water level or to divert its flow through a desired channel; e.g., a "leaping weir". (b) A notch in a levee, dam, embankment, or other barrier across or bordering a stream, through which the flow of water is regulated; e.g., a "wasteweir". Well-designed weirs usually have known dimensions and cross-section areas as a function of height above the base. Graduations of height allow rapid determination of hydraulic parameters, such as wetted perimeter, needed to calculate discharge.

structural province . A region whose geologic structure differs significantly from that of adjacent regions. It is generally coextensive with a physiographic province.

litharge (lith'-arge). A red or yellow tetragonal mineral: PbO . Cf: massicot. Syn: lead ocher. It is the Pb analogue of romarchite.

super-solidus intrusion breccia PGE deposit . A mineral-deposit type characterized by platinum-group element sulfide mineralization cutting mafic-ultramafic cumulates associated with an intrusive breccia formed by associated ultramafic dikes. Abbrev: SIB-type PGE deposit.

pull-apart basin . A topographic depression created by an extensional bend or extensional overstep along a strike-slip fault (Aydin and Nur, 1982). Syn: sag pond; rhombochasm.

minerocoenology (min''-er-o-coe-nol'-o-gy). The study of mineral associations in the broadest sense, such as the correlation of igneous rocks or magmatic provinces with their ore deposits (Thrush, 1968, p.712). Obsolete.

self-reversal (self-re-ver'-sal). Acquisition by a rock of a natural remanent magnetization opposite to the ambient magnetic field direction at the time the rock was formed.

apodeme (ap'-o-deme). One of the ingrowths from the exoskeleton of many arthropods that provide points of muscle attachment, such as an invagination of the body wall of an arachnid, an inward deflection of a sclerite of a merostome, a downward projection from the dorsal interior of a thoracic segment of a trilobite, or an infold of the exoskeleton of a crustacean.

Dunkardian (Dun-kard'-i-an). North American provincial series: uppermost Pennsylvanian-Lower Permian (above Monongahelan).


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