In
geology
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ea ...
, a sequence is a
stratigraphic unit
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ...
which is bounded by an
unconformity
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...
at the top and at the bottom.
Definition
In a more rigorous and general way a sequence is defined as a
"relatively conformable
.. genetically related succession of strata bounded by unconformities or their correlative surfaces"
Special cases and related concepts
Special cases of sequences include
type 1 sequences and
type 2 sequences.
A related concept are
parasequence A parasequence is a fundamental concept of sequence stratigraphy
Sequence stratigraphy is a branch of geology, specifically a branch of stratigraphy, that attempts to discern and understand historic geology through time by subdividing and linking s ...
s. Contrary to their name they are not smaller sequences.
See also
*
Catena (soil)
References
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Sequence stratigraphy
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