Changes

* ''Stratigraphic cross sections'', which show prior geometric relationships by adjusting the elevation of geological units to some chosen geological horizon ([[:file:geological-cross-sections_fig1.png|Figure 1]]).

* ''Stratigraphic cross sections'', which show prior geometric relationships by adjusting the elevation of geological units to some chosen geological horizon ([[:file:geological-cross-sections_fig1.png|Figure 1]]).

A third type of cross section called a ''balanced cross section'' is a combination of these two. This type attempts to portray the form of geological units prior to some episode of deformation (see [[Evaluating structurally complex reservoirs]]). It can provide important conclusions about present day geometry and past stratigraphic relationships.

A third type of cross section called a ''balanced cross section'' is a combination of these two. This type attempts to portray the form of geological units prior to some episode of [[deformation]] (see [[Evaluating structurally complex reservoirs]]). It can provide important conclusions about present day geometry and past stratigraphic relationships.

==Stratigraphic cross sections==

==Stratigraphic cross sections==

[[file:geological-cross-sections_fig1.png|thumb|300px|{{figure number|1}}(a) Stratigraphic and (b) structural cross sections of the Ranger Formation in the Long Beach unit of the Wilmington field, California. Sections are projected onto a north-south plane. (From Slatt et al.<ref name=pt06r122>Slatt, R. M., Phillips, S., Boak, J. M., Lagoe, M. B., 1993, Scales of geological heterogeneity of a deep-water sand giant oil field, Long Beach unit, Wilmington field, California, in Rhodes, E. G., Moslow, T. F., eds., Marine Clastic Reservoirs—Examples and Analogs: New York, Springer-Verlag.</ref>)]]

[[file:geological-cross-sections_fig1.png|thumb|300px|{{figure number|1}}(a) Stratigraphic and (b) structural cross sections of the Ranger Formation in the Long Beach unit of the Wilmington field, California. Sections are projected onto a north-south plane. (From Slatt et al.<ref name=pt06r122>Slatt, R. M., Phillips, S., Boak, J. M., Lagoe, M. B., 1993, Scales of geological heterogeneity of a deep-water sand giant oil field, Long Beach unit, Wilmington field, California, in Rhodes, E. G., Moslow, T. F., eds., Marine Clastic Reservoirs—Examples and Analogs: New York, Springer-Verlag.</ref>)]]

Stratigraphic cross sections show characteristics of correlatable stratigraphic units, such as reservoir sandstones or sealing shales. They may also be vital in understanding the timing of deformation by showing the drape of sediment over developing folds or the thickening of the section across [[growth fault]]s. The following elements of cross section design are presented as if they were a sequence. In practice, however, each choice affects and is affected by the others.

Stratigraphic cross sections show characteristics of correlatable stratigraphic units, such as reservoir sandstones or sealing shales. They may also be vital in understanding the timing of [[deformation]] by showing the drape of sediment over developing folds or the thickening of the section across [[growth fault]]s. The following elements of cross section design are presented as if they were a sequence. In practice, however, each choice affects and is affected by the others.

===Choice of datum===

===Choice of datum===