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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melanosclerite (mel-a-no-scle'-rite). A problematic organic (chitinous) microfossil with a dense wall and a variety of forms ranging in size from approximately 50 μm to several millimeters. It is present in organic residues from the Paleozoic of Laurentia, Baltica, and Laurasia and thought to have an affinity with hydrozoans (Cashman, 1996).

growth ruga . An irregular ruga or wrinkle on the surface of a bivalve-mollusk shell, having an origin similar to that of a growth line but corresponding to a more pronounced halt in growth.

lattice texture [eco geol] . In mineral deposits, a texture produced by exsolution in which elongate crystals are arranged along structural planes.

khari (kha'-ri). A term used in East Pakistan for a small, deep stream of local origin. Etymol: Bengali.

oxalate . A mineral compound containing the anion (C2O4)-2. An example is whewellite, Ca(C2O4)•H2O.

suture line . Surficial line on an echinoderm theca formed by the intersection of sutures with the thecal surface (Bell, 1976).

balcony . Any projection on the wall of a cave large enough to support at least one person.

simplicity (sim-plic'-i-ty). An equivalent term for the principle of parsimony [philos].

sand ridge . (a) A generic name for any low ridge of sand formed at some distance from the shore, and either submerged or emergent. Examples include a longshore bar and a barrier beach. (b) One of a series of long, wide, extremely low, parallel ridges believed to represent the eroded stumps of former longitudinal sand dunes, as in western Rhodesia. (c) A seaward-pointing landform found on a sandy beach; e.g. a beach cusp. (d) sand wave.

archerite (arch'-er-ite). A colorless or buff tetragonal mineral occurring in cave deposits: H2(K,NH4)PO4 .