projectate (pro-jec'-tate). Of pollen grains, having the apertures borne on the ends of strongly projecting arms, e.g., in Aquilapollenites.
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.
nontronite (non'-tron-ite). A member of the dioctahedral montmorillonite group of minerals in which the layer charge is the result of substitution primarily in the tetrahedral sheet. An ideal formula is: (Ca0.5,Na)0.3Fe3+2(Si,Al)4O10(OH)2• n H2O . One of the dominant minerals along mid-ocean ridges. Cf: smectite .
sphericity (sphe-ric'-i-ty). The relation to each other of the various diameters (length, width, thickness) of a particle; specif. the degree to which the shape of a sedimentary particle approaches that of a sphere. True sphericity, as originally defined by Wadell (1932), is the ratio of the surface area of a sphere of the same volume as the particle to the actual surface area of the particle. Due to the difficulty of determining the actual surface area and volume of irregular solids, Wadell (1934) developed an operational definition expressed as the ratio of the true nominal diameter of the particle to the diameter of a circumscribing sphere (generally the longest diameter of the particle). A perfect sphere has a sphericity of 1.0; all other objects have values less than 1.0. Many other measures of sphericity have been proposed. Not to be confused with roundness or angularity.
sulfide (sul'-fide). A mineral compound characterized by the linkage of sulfur with a metal or semimetal, such as galena, PbS, or pyrite, FeS2. See also: sulfosalt.
angular distance . The angle, measured at the Earth's center, that subtends the great-circle path between the earthquake's epicenter and the receiver. Cf: epicentral distance.
amalgamate (a-mal'-gam-ate). Said of a type of wall structure in trepostome bryozoans in which the zooecial boundaries are not visible in tangential section. Cf: integrate.
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.
Pages
