Accommodation: The space available for sediment to accumulate (Jervey, 1988). Accommodation is a composite of eustacy, subsidence, compaction, tectonism, and erosion.

Autochthonous: Formed or produced in the place where now found. The term is widely applied, e.g. to a coal or peat that originated at the place where its constituent plants grew and decayed, to rocks that have not been displaced by overthrust faulting, or to brecchia at an explosion crater that remains in its original position, with only minor rotation or translation of the fragments.

Biostratigraphy: Stratigraphy based on the paleontological aspects of rocks, or stratigraphy with paleontological methods; specif. the separation and differentiation of rock units on the basis of the description and study of the fossils they contain.

Borehole Image Logs: Microconductivity devices that produce an electrical image of the borehole face similar to a low resolution photograph.

Carbonate: [mineral] A mineral compound characterized by a fundamental anionic structure of CO₃^-2.
[sed] A sediment formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron, e.g. limestone or dolomite.

Chemostratigraphy: Branch of stratigraphy that uses changes in the distribution and concentrations of chemical elements and isotopes in strata to divide, organize, and correlate the sedimentary rocks.

Composite Sequence: (Depositional Sequence, 3rd order) is a relatively conformable succession of genetically related strata, bound at its top and base by unconformities or their correlative conformities, and often composed of multiple unconformity-bound High-Frequency Sequences (HFS).

Cycle: (5th order) The fundamental building block of carbonate stratigraphic analysis. Refers to the smallest set of genetically related facies deposited during a single base level rise/fall event. Comparable to parasequence. Can be mapped across multiple facies tracts, as distinguished from autocycles.

Cycle Set: Bundles of cycles that show a consistent stratigraphic trend, either progradational, aggradational, or retrogradational (transgressive). Comparable to parasequence set.

Depositional Topography: Topography formed as a result of sediments being dropped from a moving medium, e.g. coastal bars and barriers, kame terraces, or sand dunes.

Greenhouse system: Refers to a period of time on Earth where no large continental ice sheet existed. Greenhouse climatic systems are globally warmer than icehouse systems and have smaller amplitude eustatic sea-level variations.

High-Frequency Sequence: A (4th order) High-Frequency Sequence (HFS) is bound at its top and base by unconformities or their correlative conformities, and composed of systems tracts defined by base-level fall (LST), base-level rise (TST), and base level fall (HST) successions.

Highstand Systems Tracts: Volume of sediment deposited during the late part of the relative rise of sea level, the still stand of sea level, and the early part of the relative fall of sea level.

Icehouse System: Refers to a period of time on Earth where the global climate was influenced by the presence of large continental ice sheets. Icehouse climatic systems are globally cooler than greenhouse systems and have large amplitude eustatic sea-level variations linked to the growth and shrinkage of the large continental ice sheet.

Lowstand Systems Tracts: Volume of sediment deposited during the late part of the relative fall of sea level and the early part of the relative rise of sea level where sea level was below the previous sequence shelf edge.

Magnetostratigraphy: All parts of stratigraphy based on paleomagnetic signatures.

Maximum Flooding Surface: Surface that marks the turn-around from landward-stepping to seaward stepping strata. Farther out on platform, the MFS coincides with the downlap surface (depending on the degree of condensation of clinoform toes).
Recognition of the MFS is important for separating TST and HST, which in turn is important for other stratigraphic analysis. But, on the platform top (where a very large percentage of carbonate reservoirs occur) this can be difficult to pin down precisely.

Sequence Boundary: The unconformity or correlative conformity that bounds a sequence. The sequence boundary is not always a major physical feature, nor is every exposure surface is a sequence boundary. The sequence boundary commonly (but not always) represents a significant change in stratal arrangements and therefore reservoir properties.

Systems Tracts: Lowstand, Transgressive, and Highstand Systems Tracts are recognized by delineation of retrogradational, aggradational, and progradational cycle sets and component facies.

Transgressive Systems Tracts: Volume of sediment deposited during the relative rise of sea level where sea level is above the previous sequence shelf edge. This is the time of maximum retreat landward of the shoreline (or maximum potential accommodation space created on the platform top in case of an isolated platform).

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