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A
| Absolute Geologic Time |
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| Anterior
| Situated toward the front of an animal, or near or toward the head or head region, as opposed to posterior (GG2)
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| Arthropod | Any one of a group of solitary marine, freshwater, and aerial invertebrates belonging to the phylum Arthropoda, chartered chiefly by jointed appendages and segmented bodies. Among the arthropods are trilobites (GG2)
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| Assemblage | A group of fossils that occur at the same stratigraphic level; often with the connotation also of localized geographic extent. (GG2)
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| Articulate |
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B
| Bathymetry | The measurement of ocean depths and the charting of the topography of the ocean floor (GG2)
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| Bed | The smallest formal unit in the hierarchy of lithostratigraphic units. In a stratified sequence of rocks it is distinguishable from layers above and below. A bed commonly ranges in thickness from a centimeter to a few meters. the term is applied primarily to sedimentary strata. (GG2)
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| Bedding Plane | A planar or nearly planar bedding surface that visibly separates each successive layer of stratified rock (of the same or different lithology) from the preceding or following layer; a plane of deposition. It often marks a change in the circumstances of deposition and may show a parting, a color difference, or both. (GG2)
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| Benthic | Pertaining the the benthos (those forms of marine life that are bottom-dwelling) (GG2)
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| Biodiversity
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| Bivalve | (adj.) Having a shell composed of two distinct and usually movable valves, equal or subequal, that open and shut. (n) A bivalve animal, such as as a brachiopod, or specifically a mollusk of the class Bivalva (Pelecypoda), including the clams, oysters, scallops, and mussels, generally sessile or burrowing into soft sediment, having no distinct head, and possessing a hatchet-shaped foot and a sheet-like or lamelliform gill on each side of a bilaterally symmetrical body. (GG2)
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| Brachiopod | Any solitary marine invertebrate belonging to the phylum Brachiopoda, characterized by a lohophore and by two bilaterally symmetrical valves that may be calcareous or composed of chitinophosphate and that are commonly attached to a substratum, but may also be free. Range, Lower Cambrian to present. Also known as lamp shell (GG2)
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C
| Calcareous Algae |
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| Calcite | A common rock-forming mineral: CaCO3 (calcium carbonate). Calcite is usually white, colorless, or pale shades of gray, yellow, and blow; it has perfect rhombohedral cleavage, a vitreous luster, and a hardness of 3 on the Mohs scale, and it readily effervesces in cold dilute hydrochloric acid. It is the principal constituent of limestone; calcite also occurs crystalline in marble, loose and earthy in chalk, spongy in tufa,, and stalactitic in cave deposits. (GG2)
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| Carbonate | A mineral compound characterized by a fundamental anionic structure of CO3-2. Calcite (CaCO3) is an example of a carbonate. (GG2)
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| Carbonate Mud |
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| Carbonate Sand |
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| Cast | Secondary rock or mineral material that fills a natural mold - i.e. a replica or reproduction of the external details (size, shape, surface features) of a fossil shell, skeleton, or other organic structure, produced by the filling of a cavity formed by the decay or dissolution of some or all of the original hard parts of which the organism consisted. (GG2)
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| Cephalopod | Any marine mollusk belonging to the class Cephalopoda, characterized by a definite head, with the mouth surrounded by part of the foot that is modified into lobelike processes with tentacles or armlike processes with hooklets or suckers or both. the external shell, if present, as in nautiloids, is univalve and resembles a hollow cone, which may be straight, curved, or coiled and is divided into chambers connected by a siphuncle; the shell is internal in present-day cephalopods and their fossil ancestors, such as the belemnites. nautiloids and ammonoids are extinct cephalopods, generally valuable as index fossils; octopuses, squids, and cuttlefishes are common living cephalopods. Range, Cambrian to present. (GG2)
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| Clastic |
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| Climate | The characteristic weather of a region, particularly as regards temperature and precipitation, averaged over some significant interval of time. (GG2)
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| Coelenterate | Any multicelled invertebrate animal, solitary or colonial, belonging to the phylum Coelenterata, characterized by a body wall composed of two layers of cells connected by a strutureless mesogloea, by a single body cavity with a single opening for ingestion and egestion, and by radial or biradial symmetry. Range, Precambrian to present. (GG2)
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| Continental Drift | A general term, which can be used for many aspects of the theory originally propounded at length by Wegener (1912); Wegener postulated the displacement of large plates of continental crust, moving freely across a substratum of oceanic curst, but the mechanisms involved were so implausible to most geologists that the concept was generally discredited for many decades. New evidence has now been found and more acceptable mechanisms have been proposed, so that the original theory has gained a wider measure of acceptance. (GG2)
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| Contour | An imaginary line on a map or chart, that connects points of equal value - for example elevation of the land surface above or below some reference value or datum plane, generally sea level. Contours are commonly used to depict topographic surfaces. (GG2)
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| Contour Interval | The difference in value between two adjacent contours; specifically, the vertical distance between the elevations represented by two successive contour lines on a topographic map. It is generally a regular unit chosen according to the amount of vertical distance involved and the scale of the map. (GG2)
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| Coral | A general name for any of a large group of bottom-dwelling, sessile marine invertebrate organisms (polyps) that belong to the class Anthozoa (phylum Coelenterata), are common in warm intertropical modern seas and abundant in the fossil record in all periods later than the Cambrian, produce external skeletons of calcium carbonate, and exist as solitary individuals or grow in colonies. (GG2)
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| Craton | A part of the Earth's crust that has attained stability, and has been little deformed for a prolonged periods. |
| Crinoid
| Any pelmatozoan echinoderm belonging to the class Crinoidea, characterized by quinqeradiate symmetry, by a disk-shaped or globular body enclosed by calcareous plates from which appendages, commonly branched, extend radially, and by the presence of a stem, or column., more common in fossil than in living forms (GG2)
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| Cross Bedding | Beds inclined at an angle to the main planes of stratification (GG2)
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| Cross Section | A diagram or drawing that shows features transected by a given plane; specifically, a vertical section drawn at right angles to the longer axis of a geologic feature. (GG2)
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D
| Devonian | A period of the Paleozoic era (after the Silurian and before the Carboniferous (Mississippian)) thought to have covered the span of time between 400 and 345 million years ago. The Devonian is named after Devonshire, England where rocks of this age were first studied. (GG2)
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| Dip | The angle that a structural surface (e.g. a bedding or fault plane) makes with the horizontal: measured perpendicular to the strike of the structure and in the vertical plane. (GG2)
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| Dolomite | (Mineral) A common rock-forming rhombohedral mineral CaMg(CO3)2. Some of the magnesium may be replaced by iron (Fe). Dolomite is white, colorless, or tinged yellow, brown, pink, or gray, it has perfect rhombohedral cleavage and a pearly to vitreous luster, effervesces feebly in cold dilute hydrochloric acid, and forms curved, addle-like crystals. Dolomite is found in extensive beds as dolomite rock. (Rock) A carbonate sedimentary rock of which more than 50% by weight or by areal percentages under the microscope consists of the mineral dolomite; A carbonate sedimentary rock containing more than 90% dolomite and less than 10% calcite. Dolomite occurs in crystalline and noncrystalline forms, is clearly associated and often interbedded with limestone and usually represents postdepositional replacement of limestone. Named after Deodat Guy de Dolomieu (1750-1801), French geologist, and first applied to certain carbonate rocks of the Tyrolean Alps. (GG2)
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| Dolostone |
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| Dorsal | Pertaining to, or situated near or on the back or upper surface of an animal or of one of its parts. (GG2)
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E
| Echinoderm | Any solitary marine benthic (rarely pelagic) invertebrate belonging to the phylum Echinodermata, characterized by radial symmetry, an endoskeleton formed of plates or ossicles composed of crystalline calcite, and a water-vascular system. Crinoids are a type of echinoderm. (GG2)
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| Ecology | The study of the relationships between organisms and their environment, including the study of communities, patterns of life, natural cycles, relationships of organisms to each other, biogeography, and population changes (GG2)
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| Ecosystem | A unit in ecology consisting of the environment with its living elements, plus the nonliving factors that exist in and affect it. (GG2)
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| Extinction | The total disappearance of a species or higher taxon, so that it no longer exists anywhere (GG2)
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F
| Facies | The aspect, appearance, and characteristics of a rock unit, usually reflecting the conditions of its origin; especially, as differentiating the unit from adjacent or associated units. A mappable, areally restricted part of a lithostratigraphic body, differing in lithology or fossil content from other beds deposited at the same time and in lithologic continuity. A distinctive rock type broadly corresponding to a certain environment or mode of origin. A body of rock distinguished on the basis of its fossil content. (GG2)
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| Fauna | The entire animal population, living or fossil, of a given area, environment, formation, or time span. (GG2)
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| Formation | A body of rock strata which is unified with respect to adjacent strata by consisting dominantly of a certain lithologic type or combination of types or by possessing other unifying lithologic features. Thickness may range from less than a meter to several thousand meters, depending on the size of units locally required to best express the lithologic development of a region. (GG2)
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| Fossil | Any remains, trace, or imprint of a plant or animal that has been preserved in the Earth's crust since some past geologic or prehistoric time; loosely, any evidence of past life. (GG2)
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G
| Gastropod | Any mollusk belonging to the class Gastropoda, characterized by a distinct head with eyes and tentacles and, in most, by a single calcareous shell that is closed at the apex, sometimes spiralled, not chambered, and generally asymmetrical. Range: Upper Cambrian to present. (GG2)
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| Genus | A category in the hierarchy of plant and animal classification intermediate in rank between family and species. (GG2)
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| Geologic Map | A map on which is recorded geologic information, such as the distribution, nature, and age relationships of rock units, and the occurrence of structural features (folds, faults, joints), mineral deposits, and fossil localities. (GG2)
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| Geologic Time | The period of time dealt with by historical geology, or the time extending from the end of the formative period of the Earth as a separate planetary body to the beginning of written or human history. the term implies extremely long duration or remoteness in the past, although no precise limits can be set. Also see Absolute Geologic Time and Relative Geologic Time. (GG2)
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| Geologic Time Scale | An arbitrary chronologic arrangement or sequence of geologic events, used as a measure of the relative or absolute duration or age of any part of geologic time, and usually presented in the form of a chart showing the names of the various rock-stratigraphic, time-stratigraphic, or geologic-time units, as currently understood. (GG2>
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| Geologist | One who is trained in and works in any of the geological sciences. (GG2)
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| Geology | The study of the planet Earth -- the materials of which it is made, the processes that act on these materials, the products formed, and the history of the planet and its life forms since its origin. (GG2)
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| Gondwana | The Late Paleozoic continent of the Southern Hemisphere. The counterpart of Gondwana in the Northern Hemisphere is Laurasia; the supercontinent from which both were derived was Pangea.
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| Grainstone | A term used by Dunham for a mud-free (less than 1% of material with diameters less than 20 microns), grain-supported, carbonate sedimentary rock. It may be current-laid or formed by mud being washed out from previously deposited sediment, or it may result from mud being bypassed while locally produced particles accumulated. (GG2)
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| Gravel |
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H
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I
| In Situ | In its natural position; said specifically of a rock, soil, or fossil when in the situation in which it was originally formed or deposited
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| Internal Mold | A mold or impression showing the form and markings of the inner surfaces of a fossil shell or other organic structure; it is made on the surface of the rock material filling the hollow interior of the shell or organism. (GG2)
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| Invertebrate | An animal belonging to the Invertebrata, i.e. without a backbone, such as the mollusks, arthropods, and coelenterates. (GG2)
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J
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K
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L
| Limestone | A sedimentary rock consisting chiefly (more than 50% by weight or by areal percentages under the microscope) of calcium carbonate, primarily in the form of the mineral calcite and with or without magnesium carbonate; specifically a carbonate sedimentary rock containing more than 95% calcite and less than 5% dolomite. Limestones are formed by either organic or inorganic processes, and may be detrital, chemical, oolitic, earthy, crystalline, or recrystallized; many are highly fossiliferous and clearly represent ancient shell banks or reefs. (GG2)
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| Lithofacies | A lateral, mappable subdivision of a designated stratigraphic unit, distinguished from adjacent subdivisions on the basis of lithology, including all mineralogic and petrographic characteristics and those paleontologic characteristics that influence the appearance, composition, or texture of the rock. (GG20
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| Lithology | The description of rocks, especially in hand specimen and in outcrop, on the basis of such characteristics as color, mineralogic composition, and grain size. (GG2)
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M
| Map | A diagram, drawing or other graphic representation, usually on a flat surface, of selected physical features (natural, artificial, or both) of a part or the whole of the surface of the Earth or any desired surface or subsurface area, by means of signs and symbols and with the means of orientation indicated, so that the relative position and size of each feature on the map corresponds to its correct geographic situation according to a definite and established scale and projection. (GG2)
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| Map Scale | The ratio between linear distance on a map and the corresponding distance on the surface being mapped. it may be expressed in the form of a direct of verbal statement using different units (e.g. "1 inch to 1 mile" or "1 inch=1 mile"); a representative fraction or numerical ratio (e.g. "1/24,000" or 1:24,000", indicating that one unit on the map represents 24,000 identical units on the ground); or a graphic measure (such as a bar or line marked off in feet, miles, or kilometers). (GG2)
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| Marine | Of, or belonging to, or caused by, the sea
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| Mass Extinction |
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| Measured Section | A vertical representation of sediment or rock layers
that shows properties such as sediment type, fossil content, etc.
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| Microbial Organisms |
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Mineral | A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. (GG2)
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| Mud |
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| Mudstone | A term used by Dunham (1962) for a mud-supported carbonate sedimentary rock containing less than 10% grains (particles with diameters greater than 20 microns.) The term specifies neither mineralogic composition nor mud of clastic origin (GG2)
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| Mollusk | A solitary invertebrate belonging to the phylum Mollusca, characterized by a nonsegmented body that is bilaterally symmetrical and by a radially or biradially symmetrical mantle and shell. Among the classes included in the mollusks are the gastropods, pelecypods, and cephalopods. (GG2)
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N
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O
| Ordovician | The second earliest period of the Paleozoic era (after the Cambrian and before the Silurian), thought to have covered the span of time between 500 and 440 million years ago. It is named after a Celtic tribe called the Ordovices. (GG2)
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| Oncolite |
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| Organism |
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| Outcrop | That part of a geologic formation or structure that appears at the surface of the Earth. (GG2)
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P
| Packstone | A term used by Dunham (1962) for a sedimentary carbonate rock whose granular material is arranged in a self-supporting framework, yet also contains some matrix of calcareous mud. (GG2)
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| Paleoclimate | The climate of a given interval of time in the geologic past. (GG2)
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| Paleoecology | The study of the relationships between ancient organisms and their environments, the death of organisms, and their burial and postburial history in the geologic past, based on fossil faunas and floras and their stratigraphic position (GG2)
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| Paleogeography | The study and description of the physical geography of the geologic past, such as the historical reconstruction of the pattern of the Earth's surface or of a given area at a particular time in the geologic past, or the study of the successive changes of surface relief during geologic time. (GG2)
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| Paleontologist | One who studies the fossilized remains of animals and/or plants
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| Paleontology | The study of life in past geologic time, based on fossil plants and animals and including phylogeny, their relationships to existing plants, animal, and environments, and the chronology of the Earth's history.
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| Paleozoic | An era of geologic time from the end of the Precambrian to the beginning of the Mesozoic, or from about 570 to 225 million years ago.
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| Pangaea | A supercontinent that existed from about 300 to 200 million years ago and included most of the continental crust of the Earth, from which the present continents were derived by fragmentation and continental drift. during an intermediate stage of the fragmentation, between the existence of Pangaea and that of the present continents, Pangaea is believed to have split into two large fragments, Laurasia on the north and Gondwana on the South. the prooto-ocean around Pangea has been termed Panthalassa.
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| Pelagic | Pertaining to the water of the ocean as an environment. (b) Said of marine organisms whose environment is the open ocean, rather than the bottom or shore areas. pelagic organisms may be either nektonic or planktonic.
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| Photosynthetic
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| Plate Tectonics | A theory of global tectonics in which the lithosphere is divided into a number of plates whose pattern of horizontal movement is that of torsionally rigid bodies that interact with one another at their boundaries, casing seismic and tectonic activity along these boundaries. (GG2)
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| Posterior | adj. Situated toward the back of an animal or at the hinder part of the body, as opposed to anterior. The hinder part or end of an animal. (GG2)
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Q
| Quarry | Open workings, usually for the extraction of stone. (GG2)
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R
| Reef | A ridgelike or moundlike structure, layered or massive, built by sedentary calcareous organisms, especially corals and consisting mostly of their remains; it is wave-resistant and stands above the surrounding contemporaneously deposited sediment. Also such a structure built in the geologic past and now enclosed in rock commonly of differing lithology. (GG2)
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| Relative Geologic Time |
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| Rock | An aggregate of one or more minerals (for example, granite, shale, marble); or a body of undifferentiated mineral matter. (GG2)
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S
| Sand |
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| Sandstone | A medium-grained clastic sedimentary rock composed of abundant rounded or angular fragments of sand size set in a fine-trained matrix (silt or clay) and more or less firmly united by a cementing material (commonly silica, iron oxide, or calcium carbonate); the consolidated equivalent of sand, intermediate in texture between conglomerate and shale. (GG2)
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| Sediment |
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| Sedimentary Rock | A rock resulting from the consolidation of loose sediment that has accumulated in layers (for example, a clastic rock - such as a conglomerate or sandstone) consisting of mechanically formed fragments of older rock transported from its source and deposited by water or from air or ice; or a chemical rock (such as rock salt or gypsum) formed by precipitation from solution; or an organic rock (such as certain limestones) consisting of the remains or secretions of plants and animals. the term is restricted by some authors to include only those rocks consisting of mechanically derived sediment; others extend it to embrace all rocks other than purely igneous and completely metamorphic rocs. (GG2)
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| Sedimentologist |
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| Sedimentology | The scientific study of sedimentary rocks and of the processes by which they were formed; the description, classification, origin, and interpretation of sediments. (GG2)
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| Shale | A fine-grained detrital sedimentary rock, formed by the consolidation (especially by compression) of clay, silt, or mud. it is characterized by finely laminated structure, which imparts a fissility approximately parallel to the bedding, along which the rock breaks readily into thin layers and that is commonly most conspicuous on weathered surfaces, and by an appreciable content of clay minerals and detrital quartz. (GG2)
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| Silurian | A period of the Paleozoic, thought to have covered the span of time between 440 and 400 million years ago; also the corresponding system of rocks. The Silurian follows the Ordovician and precedes the Devonian. it is named after the Silures, a Celtic tribe. (GG2)
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| Species | A group of organisms, either plant or animal, that may interbreed and produce fertile offspring having similar structure, habits, and functions. As a fundamental unit in the hierarchy of classification, species ranks next below genus. (GG2)
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| Stratigraphic Section |
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| Stratigraphy | (a) The science of rock strata It is concerned not only with the original succession and age relations of rock strata but also with their form, distribution, lithologic composition, fossil content, geophysical and geochemical properties -- indeed, with all characteristics and attributes of rocks as strata; and their interpretation in terms of environment or mode of origin and geologic history. All classes of rocks, consolidated or unconsolidated, fall within the general scope of stratigraphy. (b) The arrangement of strata, especially as to geographic position and chronologic order of sequence. (c) the sum of the characteristics studied in stratigraphy; the part of geology of an area or district pertaining to the character of its stratified rocks. (d) A term sometimes used to signify the study of historical geology. (GG2)
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| Strata |
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| | Strike | The direction or trend taken by a structural surface, such as a a bedding or fault plane, as it intersects the horizontal
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| | Stromatoporoid | A general name for any of a group of extinct sessile benthic marine organisms of uncertain biologic affinities (probably phylum Porifea, possibly Coelenterata or Cyanophyta). They secreted a calcareous skeleton, generally a few tens of centimeters across, of tabular, encrusting, dendroidal, domal, or bulbous form; internal structural elements were arranged in subhorizontal or concentric laminae or lines of disspeiments separated by small radial pillars, or an irregular open network. Stromatoporoids were especially abundant in Ordovician-Devonian reefs. Range, Cambrian(?) to Cretaceous. (GG2)
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| Subtropical |
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| Supercontinent |
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| Supercontinent |
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| Superposition |
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T
| Tectonics | A branch of geology dealing with the broad architecture of the outer part of the Earth, that is, the regional assembling of the structural or deformation features, a study of their mutual relations, origin, and historical evolution. It is closely related to structural geology, with which the distinctions are blurred, but tectonics generally deals with larger features.
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| Topographic Map | A map showing the topographic features of a land surface, commonly by means of contour lines. it is generally on a sufficiently large scale to show in detail selected man-made and natural features, including relief and such physical and cultural features as vegetation, roads, and drainage. (GG2)
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| Topography |
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| Trilobite | Any marine arthropod belonging to the class Trilobita, characterized by a three0lobed, ovoid to subelliptical exoskeleton divisible longitudinally into axial and side regions and transversely into cephalon (anterior), thorax (middle), and pygidium (posterior). Range, Lower Cambrian to Permian (GG2)
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| Tropical | Said of a climate characterized by high temperature and humidity and by abundant rainfall. An area of tropical climate borders that of equatorial climate.
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U
| Uniformitarianism | The fundamental principle or doctrine that geologic processes and natural laws now operating to modify the Earth's crust have acted in the same regular manner and with essentially the same intensity throughout geologic time, and that past geologic events can be explained by phenomena and forces observable today; the classical concept that "the present is the key to the past". The doctrine does not imply that all change is at a uniform rate, and does not exclude minor local catastrophes.
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V
| Ventral | Pertaining or belonging to the abdominal or lower surface of an animal or one of its parts that is opposite the back. (GG2.
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W
| Wackestone | A term used by Dunham (1962) for a mud-supported carbonate sedimentary rock containing more than 10% grains (particles with diameters greater than 20 microns), (GG2)
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| Wave | The oscillatory movement of water manifested by an alternate rise and fall of a surface in or on the water.
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| Wave Base | The depth at which wave action do longer stirs the sediments. It is typically about 10 meters. (GG2)
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X
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Y
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Z
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Last updated; January 10, 1997
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