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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Danian (Dan'-i-an). A stage of the Standard Global Chronostratigraphic Scale: lowermost Paleocene and base of Cenozoic (above Maastrichtian Stage of Cretaceous , below Selandian). The basal GSSP in Tunisia coincides with global iridium anomaly.

double biseries (dou'-ble). Two distinct sets of coverplates in edrioasteroids, the pairs of one set alternating with those of the other to form an integrated system (Bell, 1976).

spectrometer (spec-trom'-e-ter). An instrument used for spectroscopy and the measuring, recording, and the comparing of the intensity of light in different parts of a spectrum as a function of wavelength; formerly called a spectrophotometer. See also: spectrometry, flame photometer, spectrocolorimeter .

making hole (mak'-ing). The act of drilling a well.

ardennite (ar-den'-nite). A yellow to yellowish-brown orthorhombic mineral: Mn2+4(Al,Mg)6(SiO4)2(Si3O10)[(As,V)O4](OH)6 .

mottled zone . A layered that is marked with spots or blotches of different color or shades of color. The pattern of mottling and the size, abundance, and color contrast of the mottles may vary considerably and should be specified in the soil description. See also: soil color.

polarity interval . The fundamental unit of worldwide polarity-chronostratigraphic classification. The term is applied to rock, not time; it is used in a spatial sense (Oriel et al., 1976, p.276).

traverse table . A mathematical table listing the lengths of the two sides opposite the oblique angles for each of a series of right-angled plane triangles as functions of every degree of angle (azimuth or bearing) and of all lengths of the hypotenuse from 1 to 100. Traverse tables are used in computing latitudes and departures in surveying and courses in navigation.

dun . An inconspicuous hill in the English Lake District. Etymol: Gaelic.

gupeiite (gu-pei'-ite). A metallic steel-gray cubic mineral: Fe3Si .

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