A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals

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A reduction in bed thickness resulting from onlapping stratigraphic sequences

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A relatively flat, nearly level area of sedimentary rocks in a continent that overlies or abuts the basement rocks of a craton

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A relatively high-standing area formed by the movement of normal faults that dip away from each other.

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A relatively impermeable rock, commonly shale, anhydrite or salt, that forms a barrier or seal above and around reservoir rock so that fluids cannot migrate beyond the reservoir

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A relatively low-standing fault block bounded by opposing normal faults.

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A relatively mobile mass that intrudes into preexisting rocks

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A reservoir in which buoyant forces keep hydrocarbons in place below a sealing caprock

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A reservoir or portion of a reservoir that contains economically producible hydrocarbons

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A rhythmic sequence of sediments deposited in annual cycles in glacial lakes

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A rock composed chiefly (> 90%) of dolomite

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A rock mass formed somewhere other than its present location, which was transported by fault movements, large-scale gravity sliding, or similar processes.

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A rock rich in organic matter which, if heated sufficiently, will generate oil or gas

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A scientist trained in the study of the Earth

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A sedimentary rock and a variety of quartz made of extremely fine-grained, or cryptocrystalline, silica, also called chalcedony

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A sedimentary rock containing a mix of clay and calcium carbonate

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A semi-enclosed coastal environment of deposition in which a river mouth permits freshwater to contact and mix with seawater

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A soft, silica-rich sedimentary rock comprising diatom remains that forms most commonly in lakes and deep marine areas

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A soft, soluble evaporite mineral commonly known as salt or rock salt

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A solid or nearly solid form of bitumen that can melt upon heating and contains impurities such as nitrogen, oxygen and sulfur

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A stable area of continental crust that has not undergone much plate tectonic or orogenic activity for a long period

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A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids.

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A subsurface condition in which the pore pressure of a geologic formation exceeds or is less than the expected, or normal, formation pressure.

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A subsurface oil accumulation

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A subsurface rock that lacks contact with aquifers or meteoric water within the Earth

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A surface feature of the Earth that allows magma, ash and gas to erupt

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A surface land form

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A surface of breakage, cracking or separation within a rock along which there has been no movement parallel to the defining plane

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A surface that separates older sequences from younger ones, commonly an unconformity (indicating subaerial exposure), but in limited cases a correlative conformable surface

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A surface that separates younger strata from eroded, dipping, older strata and represents a gap in the geologic record

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A system of numerous Earth-orbiting satellites that can be used to determine the location (latitude, longitude and elevation) of a receiver or station on the Earth within about 2 m [6 ft]

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A telescopic surveying device used to construct surface topographic and geologic maps in the field

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A term applied to hard rocks, or igneous and metamorphic rocks that are distinguished from sedimentary rocks because they are typically more difficult to disaggregate

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A test in which the pore fluid in the sample is able to flow and equilibrate to imposed pore pressure conditions; the fluid mass and volume will vary but its pressure will be constant

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a test that in which the fluid in the sample is not able to flow and equilibrate to imposed pore pressure conditions; the fluid mass remains the same while the fluid volume and pressure will vary

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A thrust fault having a relatively large lateral displacement

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A topographic feature consisting of a large flat area at a relatively high elevation with steep sides

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A type of anticline that is circular or elliptical rather than elongate

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A type of clay mineral from the kaolin group that forms through the weathering of feldspar and mica group minerals

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A type of fault whose surface is typically vertical or nearly so.

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A type of fold in which the thickness of the layers remains constant when measured parallel to the axial surface and the layers have the same wave shape, but the thickness along each layer varies

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A type of geochemical analysis in which a rock sample is subjected to controlled heating in an inert gas to or through a hydrocarbon generating point to assess its quality as the source rock, the abundance of organic matter in it, its thermal maturity, and the quality of the hydrocarbons that may be produced or have been produced

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A type of hydrocarbon trap whose closure is controlled by the presence of an unconformity

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A type of fault formed when the hanging wall fault block moves up along a fault surface relative to the footwall. Such movement can occur in areas where the Earth's crust is compressed

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A type of fault in which the hanging wall moves down relative to the footwall, and the fault surface dips steeply, commonly from 50o to 90o.

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A type of metamorphic rock with shearing and granulation of minerals caused by high mechanical stress during faulting or dynamic metamorphism, typically during episodes of plate tectonic activity

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A type of minor fault whose sense of displacement is similar to its associated major fault

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A type of normal fault that develops and continues to move during sedimentation and typically has thicker strata on the downthrown, hanging wall side of the fault than in the footwall

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A type of porosity resulting from the presence of vesicles, or gas bubbles, in igneous rock

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A type of reverse fault in which the fault plane has a very shallow dip, typically much less than 45o

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A type of secondary porosity created during diagenesis, commonly through dissolution or dolomitization or both

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A type of secondary porosity created through the dissolution of a preexisting constituent of a rock, such as a shell, rock fragment or grain

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A type of secondary porosity produced by the tectonic fracturing of rock

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A type of smectite clay mineral that tends to swell when exposed to water

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A type of stratigraphic trap. The termination by thinning or tapering out ("pinching out") of a reservoir against a nonporous sealing rock creates a favorable geometry to trap hydrocarbons, particularly if the adjacent sealing rock is a source rock such as a shale

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A type of strike-slip fault in which the fault surface is vertical, and the fault blocks move sideways past each other

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A type of structural hydrocarbon trap in which closure is controlled by the presence of at least one fault surface

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A type of subsurface map whose contours represent the elevation of a particular formation, reservoir or geologic marker in space, such that folds, faults and other geologic structures are clearly displayed

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A type of topography formed in areas of widespread carbonate rocks through dissolution

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A type of woody kerogen that is relatively uniform in composition.

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A variety of sealed geologic container capable of retaining hydrocarbons, formed by changes in rock type or pinch-outs, unconformities, or sedimentary features such as reefs

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A variety of sealed geologic structure capable of retaining hydrocarbons, such as a fault or a fold.

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A water-bearing portion of a petroleum reservoir with a waterdrive

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A wave-like geologic structure that forms when rocks deform by bending instead of breaking under compressional stress

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A wetland depositional environment in which water is present either permanently or intermittently and in which trees and large woody plants can grow but peat does not form

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A widely-distributed carbonate mineral and chief constituent of dolostone

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A worldwide grid system of rectangular map coordinates that uses metric (SI) units.

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A zone of the upper mantle in which earthquakes occur when a lithospheric plate is subducted, named in honor of seismologists Kiyoo Wadati and Hugo Benioff

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Ability of a material to undergo stress, deform, and then recover and return to its original shape after the stress ceases

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Also known as plate tectonics, the unifying geologic theory developed to explain observations that interactions of the brittle plates of the lithosphere with each other and with the softer underlying asthenosphere result in large-scale changes in the Earth

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Also known as weathered layer, a near-surface, possibly unconsolidated layer of low seismic velocity

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An abundant rock-forming mineral composed of silicon and oxygen, also called silica. Quartz sand grains are a major constituent of sandstone and other clastic sedimentary rocks.

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An accumulation, pool or group of pools of oil in the subsurface.

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An accumulation, pool, or group of pools of hydrocarbons or other mineral resources in the subsurface

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An aggregate of minerals or organic matter (in the case of coal, which is not composed of minerals because of its organic origin), or volcanic glass (obsidian, which forms a rock but is not considered a mineral because of its amorphous, noncrystalline nature).

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An analysis of the history, composition, relative ages and distribution of strata, and the interpretation of strata to elucidate Earth history

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An arch-shaped fold in rock in which rock layers are upwardly convex

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An arcuate deposit of sediment, usually sand, that occurs along the convex inner edges of the meanders of channels and builds outward as the stream channel migrates.

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An area in which hydrocarbon accumulations or prospects of a given type occur.

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An area of surface land on which exploration or production activity occurs

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An area of the subsurface where source rock has reached appropriate conditions of pressure and temperature to generate hydrocarbons

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An area of the subsurface where source rock has reached appropriate conditions of pressure and temperature to generate liquid hydrocarbons as opposed to gas

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An entity or property that differs from what is typical or expected, or which differs from that predicted by a theoretical model

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An environment from which water rarely drains that supports primarily grassy vegetation and does not form peat

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An environment of coastal sedimentation characterized by arid or semiarid conditions above the level of high tide and by the absence of vegetation

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An exploration and production play type in which prospects exist below salt layers

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An influx of rapidly moving, sediment-laden water down a slope into a larger body of water; the suspended sediment causes the current to have a higher density than the clearer water into which it flows, hence the name

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An informal term used to denote a surface in or of rock, or a distinctive layer of rock that might be represented by a reflection in seismic data

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An interaction of lithospheric plates that can result in the formation of mountain belts and subduction zones

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An interval or unit of rock differentiated from surrounding rocks on the basis of its fossil content or other features, such as faults or fractures

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An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers

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An occurrence of trapped hydrocarbons, an oil field

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An umbrella term for oil and natural gas that is produced by means that do not meet the criteria for conventional production

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An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules

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An unusual occurrence of hydrocarbon in which molecules of methane are trapped in ice molecules

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Basin- or trough-shaped fold in rock in which rock layers are downwardly convex

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Bubble-shaped cavities in volcanic rock formed by expansion of gas dissolved in the precursor magma

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Compaction and cementation of sediments to the degree that they become coherent, relatively solid rock

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Containing chert, a sedimentary rock and a variety of quartz made of extremely fine-grained, or cryptocrystalline, silica, also called chalcedony

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