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.