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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walkaway VSP . A vertical seismic profile that involves moving the source away from the wellhead between energy injections.

paint . A term used in SW U.S. for an earthy, pulverulent variety of cinnabar (Thrush, 1968).

aphyric (a-phyr'-ic). Said of the texture of a fine-grained or aphanitic igneous rock that lacks phenocrysts; also a rock exhibiting such texture.

replacement [paleont] . A process of fossilization involving substitution of inorganic matter for the original organic constituents of an organism.

ferribarroisite . A dark green to black monoclinic mineral of the amphibole group, representing barroisite with essential Fe3+: NaCa(Mg3Fe3+2)(Si7Al)O22(OH)2.

palpus (pal'-pus). A term applied either to a pedipalpus (including pedipalpal coxae) or more properly to one of the five segments following the coxa in an arachnid (TIP, 1955, pt. P, p.62). Pl: palpi. Adj: palpal. See also: palp.

isinglass (i'-sin-glass). A syn. of mica, esp. muscovite in thin transparent sheets.

ice gneiss . Frozen ground with ice segregated in laminae so as to resemble a gneissic rock; term used by Taber (1943).

Ontarian (On-tar'-i-an). (a) Stage in New York State: Middle Silurian (middle and lower parts of Clinton Group). (b) An obsolete name for the Middle and Upper Ordovician in New York State.

ankaramite (an-ka'-ra-mite). An olivine-bearing basanite containing numerous pyroxene (usually clinopyroxene) phenocrysts, the former being more abundant than the latter, in a fine-grained groundmass composed of clinopyroxene microlites and calcic plagioclase. It was named by Lacroix in 1916 from Ankaramy, Malagasy.


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