  - ANAEROBIC. Usually in reference to organisms that can live without oxygen.
- ANGULAR UNCONFORMITY. Two rock layers which are not parallel; the underlying older layer dips at a different angle (usually steeper) than the younger top strata.
- ANNULI. Marks on fish scales produced by periods (usually winter) of nongrowth.
- ANTICLINE. A fold in stratified rock with the strata sloping downward in opposite directions from the fold crest.
- ARAGONITE. A carbonate mineral with specific characteristics.
- AUTHIGENIC. A mineral (such as quartz or feldspar) which is formed after the deposition of a sedimentary layer in which it occurs.
- BENTONITE. A light-colored, soft, porous rock formed from the minute clay crystals of eroded volcanic ash. It has the characteristic of swelling when wet (water absorption) and contracting when dry.
- BRACKISH. A condition in a body of water in which the salinity (salt level) is below that of sea water, but higher than that of fresh water.
- CARBONACEOUS. Rock or sediment which contains carbon or altered organic material such as coal.
- CHERTY. Containing chert: a dull-colored, flint-like quartz often found in limestone.
- CIRCULI. Ridges on fish scales produced during growth of the scales.
- CLAST. Rock fragments which are the result of weathering of a larger rock mass.
- CLASTIC. Rocks that consist of particles derived from pre-existing rocks or minerals.
- CLAYSTONE. An indurated clay without the lamination or fissility of shale.
- CONGLOMERATE. A coarse-grained sedimentary rock composed of fragments larger than 2 mm in diameter in a fine-grained matrix.
- CROSS-BEDDING. An internal structure in sedimentary rock in which the upper sedimentary layer runs across the grain of the main bed; it is caused by changing currents depositing sediment across the grain of the original deposits.
- DIAMICTITE. A sedimentary rock containing a wide range of particle sizes.
- DIP. The downward inclination of a rock layer; the vertical angle is determined by its relationship to a horizontal plane.
- DOLOMITIC. Containing a measurable amount of the mineral dolomite; a mineral consisting mainly of magnesium carbonate and calcium carbonate.
- FACIES. Lateral variations in the appearance or composition of a rock layer. The variations can be lithologic or paleontologic.
- FAULT. A fracture in the earth’s crust along which displacement (movement) has occurred.
- FLUVIAL. Pertaining to a river or rivers. Fluvial sediments are those transported and deposited by stream action.
- FORMATION. A rock layer that is mappable; has a distinctive lithology or series of lithologies. A mappable sequence of uniform or uniformly varying rocks.
- GASTROPODAL. A rock containing an abundance of gastropods.
- HOGBACK. A long, narrow, sharp-crested ridge formed by the outcropping edges of steeply inclined resistant rocks.
- IGNEOUS ROCKS. A rock or mineral that has solidified from molten or partly molten material.
- INTRUSIVE. Igneous rock formed by the forcing of molten material into a pre-existing rock.
- IRONSTONE. A rock composed of various iron minerals that accumulated during or shortly after deposition of the enclosing sediments.
- LACUSTRINE. Pertaining to, produced by, or formed in a lake or lakes.
- LATERITIC. Containing laterite: a red, porous material usually developed in a tropical to temperate climate. It is a residual or end-product of weathering.
- LIGNITE. A brownish-black coal that is intermediate in coalification between peat and subbituminous coal.
- LITHOLOGY. The scientific study of rocks: composition, texture, color, origin, etc.
- MAGNETITE. A black, opaque mineral that is strongly magnetic.
- MARLSTONE. An impure limestone.
- METAMORPHIC. Rocks whose structure has been changed by pressure, heat, chemical reaction, etc., such as limestone into marble.
- MUDSTONE. An indurated mud without the lamination or fissility of shale.
- OPERCULAR OPENING. The gill opening of fish.
- OSTRACODAL. A rock, usually a limestone, that contains an abundance of the small crustacean, ostracods.
- OVERTHRUST. A low-angle thrust fault of large scale, usually measured in miles.
- PALEOLIMNOLOGY. The study of ancient lakes.
- PAPER SHALE. A form of finely laminated shale that weathers into extremely thin, curled flakes.
- PHOSPHATIC. Containing phosphates.
- PHYTOPLANKTON. Floating microscopic plant life that occurs abundantly in lakes and oceans.
- PLATY. Rocks (sandstone or limestone) which separate into small slabs.
- PORCELLANITE. A dense cherty rock resembling porcelain.
- PUDDINGSTONE. A conglomerate consisting of well-rounded pebbles and cobbles sparsely packed in a fine-grained matrix.
- SILTSTONE. An indurated silt without the lamination or fissility of shale.
- STRATA. Rock layers of distinct composition and origin.
- SYNCLINE. A fold in stratified rock in which the strata slope up from the axis of the fold forming a v opposed to anticline.
- TAPHONOMY. The branch of paleoecology which deals with the change from living animals to fossils.
- TECTONIC. The forces which result in structural changes in the earth’s crust.
- THRUST FAULT. A fault in which an upper segment of rock (hanging wall) moves upward at a low angle (less than 45°) relative to a lower segment (footwall).
- TONGUE. A rock unit that wedges into, but disappears within, another rock unit.
- TUFFACEOUS. Sediment that contains up to 50% volcanic ash or dust.
- UNCONFORMITY. A substantial break or gap in the geologic or stratigraphic record.
- UNGULATES. Hooved mammals.
- VARVE. A set of rock laminae in which different types of sediment were deposited in the winter and in the summer. Thus a couplet of each sediment type would represent the deposition of one year.
- WELL SORTED. A rock in which nearly all of the sediment particles are of one grain size.
- ZOOPLANKTON. Floating microscopic animal life that occurs abundantly in lakes and oceans.
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