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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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).

Peters' length (Pe'-ters). A horizontal distance between the points on the side of the potential-field (usually, magnetic) anomaly profile, where the slope line is drawn at half of the maximum slope line. This measurement is made with the objective of determining the depth of an anomalous mass (magnetized body). For tabular body or dike models, the Peters' rule gives a depth as 5/8 of the Peters' length (Peters, 1949).

westward drift (west'-ward). A component of the secular variation of the Earth's magnetic field; the movement is about 0.2° per year of the broad-scale departures of the actual geomagnetic field from an ideal dipole field.

friedrichite (fried'-rich-ite). A metallic orthorhombic mineral, a member of the aikinite-bismuthinite series, with a unique superstructure: Pb5Cu5Bi7S18 .

equatorial opening . median split. Also the part of an acritarch anterior to the equator and containing the excystment opening. Cf: hypocyst.

buried channel (bur'-ied). An old channel concealed by surficial deposits; esp. a preglacial channel filled with glacial drift.

barkevikite (bar-ke-vik'-ite). A brownish or velvet-black monoclinic mineral of the amphibole group, near arfvedsonite in composition and appearance. An unnecessary name for an iron-bearing or ferropargasitic hornblende.


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