uropod (u'-ro-pod). Either of the flattened leaflike appendages of the last abdominal segment of various crustaceans, which with the telson form the caudal fan; e.g. limb of the sixth abdominal somite of a eumalacostracan, or one of the last three abdominal appendages of an amphipod. The term is sometimes applied to any abdominal appendage of a crustacean.
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.
rose diagram . A circular or semicircular star-shaped graph indicating values or quantities in several directions of bearing, consisting of radiating rays drawn proportional in length to the value or quantity; e.g. a current rose, a structural diagram for plotting strikes of planar features, or a "histogram" of orientation data.
sterane . Hydrocarbon resulting from steroid molecules in the geological environment.
proglacial (pro-gla'-cial). Immediately in front of or just beyond the outer limits of a glacier or ice sheet, generally at or near its lower end; said of lakes, streams, deposits, and other features produced by or derived from the glacier ice.
coefficient of earth stress . The principal-stress ratio at a given point in a soil.
primary dolomite . A dense, finely textured dolomite rock, made up of grains less than 0.01 mm in diameter, formed in place by direct chemical or biochemical precipitation from seawater or lake water. Characteristically it is well-stratified, unfossiliferous, and interbedded with anhydrite, clay, and micritic limestone. Also, a similarly textured dolomite rock made up of clastic particles formed by direct accumulation. Some authors consider the rock to be syndiagenetic (Fairbridge, 1967, p.66-67). See also: dolomicrite. Syn: orthodolomite.
climatic (cli-mat'-ic). Said of ecologic formations resulting from or influenced by differences in climate. Cf: edaphic.
commensal (com-men'-sal). Said of organisms living in a state of commensalism.
hulsite (huls'-ite). A submetallic black monoclinic mineral: (Fe2+,Mg)2(Fe3+,Sn)BO5 .
hornfels (horn'-fels). A fine-grained rock composed of a mosaic of equidimensional grains without preferred orientation and typically formed by contact metamorphism. Porphyroblasts or relict phenocrysts may be present in the characteristically granoblastic (or decussate) matrix (Winkler, 1967).
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