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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radiolarian ooze . A deep-sea pelagic sediment containing at least 30% opaline-silica tests of radiolarians. It is a siliceous ooze.

kinoite (kin'-o-ite). A blue monoclinic mineral: Ca2Cu2Si3O8(OH)4 .

Båth's law . A generalization in seismology that the largest aftershock occurring within a few days of a main shock has a magnitude of 1.2 units lower than that of the main shock (Richter, 1958, p.69).

conotheca (co-no-the'-ca). (a) Conoidal theca with a small circular aperture located at the terminus of a short neck developed irregularly in colonies of tuboid graptolithines (Whittington and Rickards, 1968). (b) The outer shell of ectocochleate cephalopods and of the phragmocone of endocochleate cephalopods.

fenitization (fen''-it-i-za'-tion). As generally used today, widespread alkali metasomatism of quartzo-feldspathic country rocks in the environs of carbonatite complexes.

Wolfcampian (Wolf-camp'-i-an). North American series: lowermost Permian (above Virgilian of Pennsylvanian, below Leonardian).

caltonite (cal'-to-nite). A dark-colored analcime-bearing basanite that contains microphenocrysts of olivine and clinopyroxene in a trachytic groundmass composed of feldspar laths, clinopyroxene, iron oxides, and analcime. It was named by Johannsen (1931) for Calton Hill, Derbyshire, England. Obsolete.

sault . A waterfall or rapids in a stream. Etymol: French, old spelling of "saut" (from Latin "saltus"), "leap".

chiastoclone (chi-as'-to-clone). A desma (of a sponge) in which several subequal, zygome-bearing arms radiate from a very short central shaft, giving the spicule an X-shaped profile.

deflection [geomorph] . A sharp change in the trend of a mountain chain. The term was introduced by Bucher (1933) as a translation of Staub's term Beugung. It differs from an orocline by not necessarily being a strain imposed on the completed orogen. See also: capped deflection; fractured deflection. Cf: linkage [geomorph].

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