Definitions

uniclinal

Homocline

In structural geology, a uniclinal structure, homoclinal structure, unicline or homocline (from old homo = same, cline = inclination) is a sedimentary rock unit, which may also be associated with a stratigraphic landform, where the underlying strata are tilted in the same direction, especially with near uniform dip angle. A homocline may be formed by uplift of coastal plain sediments, or as a limb of a large dome or fold. On a topographic map, homoclines exhibit nearly parallel elevation contour lines that show a steady change in elevation in a given direction.

A homoclinal ridge, or strike ridge, is a stratigraphic landform typically characterized by a steep escarpment or scarp slope (also known as a strike slope or antidip slope) on the side that cuts across the strata, and a more gentle dip slope on the side of the ridge that follows the dip. A homoclinal ridge forms when tilted strata with dissimilar erosional resistance erode at different rates. The more durable erosion resistant materials are the slope-formers found on the typically shallower back slope, while more easily eroded layers are the cliff-formers. These ridges are well formed when harder sandstones and limestones are interbedded with softer shales, siltstones, and mudstones in tilted exposed strata, resulting in differential erosion. Ridges associated with homoclines having steeply tilted strata, and exhibiting nearly symmetrical cross-section, are also known as hogback ridges; those with gently tilting strata, with highly asymmetric profiles, are known as cuestas. Homoclinal ridges differ from synclinal or anticlinal ridges, in that they have strata dipping in only one direction. Most of the stratigraphic ridges in the Ridge-and-Valley Appalachians of the eastern United States are homoclinal ridges.

Etymology

Homocline was introduced as a new term at the 1915 meeting of the Geological Society of America, but its precise definition and usage have been inconsistent, as was the case with the term monocline before then. Both terms have been used to describe "beds dipping in one direction" and a "one-limbed flexure", with different authors making incompatible distinctions. Henry Darwin Rogers introduced the term monoclinal in 1842, and it supplanted the term uniclinal which was used previously, but is now considered obsolete.

References

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