Homocline

In structural geology, a uniclinal structure, homoclinal structure, unicline or homocline (from old _el. "homo" = same, "cline" = inclination)cite web |url=http://www.wou.edu/las/physci/taylor/erth350/erth350.htm |title=Overview of Structural Geology and Geologic Map Interpretation |accessdate=2008-03-16 |format=pdf |work=ERTH350 Environmental Geology (class notes)|publisher=Western Oregon University|author = Taylor, S.|date=2005-01-05|quote=Homoclinal Structure: Homo = same, Cline = inclination; homoclinal structure = uniformly tilted beds…] is a sedimentary rock unit, which may also be associated with a stratigraphic landform, where the underlying strata are tilted in the same direction,cite book |author=Hyne, Norman J. |title=Nontechnical guide to petroleum geology, exploration, drilling, and production |publisher=Penn Well Corp |location=Tulsa, OK |year=2001 |pages= p. 60 |isbn=0-87814-823-X |quote=Sedimentary rocks dipping uniformly in one direction are known as a "homocline".] especially with near uniform dip angle. [cite book|title = Encyclopaedia of Geomorphology| first=Mohammad | last= Naqi | year = 2006 | publsiher = Anmol Publications | isbn = 8126124458 | quote = Uniclinal/Homoclinal Structure : Homoclinal structures are those which represent inclined rock strata at uniform dip angle caused by general regional tilt.] A homocline may be formed by uplift of coastal plain sediments, or as a limb of a large dome or fold.cite book |author=Sugden, David E.; Chorley, Richard J.; Schumm, Stanley Alfred |title=Geomorphology |publisher=Methuen |location=London |year=1985 |pages= |isbn=0-416-32590-4 |oclc= |doi= | quote = These structures are produced in two main ways, either by the uplift of a sequence of off-lapping coastal plain sediments or as part of one 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.cite book |author=Reynolds, Stephen J.; Davis, George Theron |title=Structural geology of rocks and regions |publisher=John Wiley |location=New York |year=1996 |pages= p. 481|isbn=0-471-52621-5 | quote=Homoclines, which are simple tilted structures where bedding dips uniformly in a single 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.cite web |url=http://myweb.cwpost.liu.edu/vdivener/notes/structure_landforms.htm |title=Structural Control of Fluvial Landscapes| work = Crustal Structures and Landforms (course notes) |accessdate=2008-03-16 | author = Divener, V. |format= |publisher = Long Island University C.W. Post Campus|quote="Homoclinal ridges" formed by the resistant beds are typically asymmetrical (if the strata don't dip too steeply) with a steep "scarp slope" and a more gentle "dip slope".] cite book |author=Huggett, Richard J. |title=Fundamentals of geomorphology |publisher=Routledge |location=New York |year=2003 |pages= p. 93 |isbn=0-415-24145-6 |quote=Homoclinal ridge or strike ridge: Ridge formed in gently dipping strata with an asymmetrical cross-section of escarpment and dip slope.] 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.cite web |url=http://www.britannica.com/eb/topic-145944/cuesta |title=Cuesta, or homoclinal ridge (geology) |accessdate=2008-03-16 |format= |work=Britannica Online Encyclopedia|quote=This landform occurs in areas of tilted strata and is caused by the differential weathering and erosion of the hard capping layer and the soft underlying cliff maker, which erodes more rapidly.] 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.cite book |author=Gerrard, John |title=Rocks and landforms |publisher=Unwin Hyman |location=Boston |year=1988 |pages= p. 80|isbn=0-04-551113-6 |quote=Homoclinal ridges and hogbacks are best developed where rocks such as limestone and sandstone form the resistant layers and shales, and siltstones and mudstones form the weaker layers.] 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.cite web |url=http://itc.gsw.edu/faculty/bcarter/geomorph/struct/fold3.htm |title=Folds — Folded Sedimentary Rocks |author = Carter, B. |accessdate=2008-03-16 |format= | publisher=Georgia Southwestern State University |work=GEOL3411 -- Geomorphology (lecture notes)|quote=Because these ridges would have beds dipping only in one direction they are called "homoclinal ridges" and the valleys beside them are called "homoclinal valleys"] Most of the stratigraphic ridges in the Ridge-and-Valley Appalachians of the eastern United States are homoclinal ridges.cite web |url=http://daac.gsfc.nasa.gov/geomorphology/GEO_2/GEO_PLATE_T-12.shtml |title=Geomorphology : Chapter 2 Plate T-12 : Folded Appalachians | date = 2007-01-19 |accessdate=2008-03-16 |publisher= NASA, Goddard Earth Sciences (GES), Data and Information Services Center (DISC) |first=Steve | last = Kempler|work=|quote=Most ridges are monoclinal, and the dip of many can be determined by the difference in scarp and dip slopes.]

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.cite book|title = Principles of Oil and Gas Production |first = Roswell Hill | last = Johnson | coauthors = Louis Grow Huntley | year = 1916 | publisher = John Wiley & sons | pages = p. 64 | quote = Monocline is a much abused term. For many years, some have used it for "beds dipping in one direction," others for a "one-limbed flexure." … there was a favorable response to the introduction of the new term homocline at the 1915 meeting of the Geological Society of America, …] 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,cite book|title =The Century Dictionary: An Encyclopedic Lexicon of the English Language |first = William Dwight | last = Whitney | publisher = The Century Co. | year = 1890 | pages = p. 3837| quote = monoclinal (mon'ö-kli-nal), a. and и. [< monocline + -al.] I. a. in geol., dipping in one direction : said of a zone of stratified rocks throughout which the strata all incline toward the same point of the compass. The term was introduced by HD Rogers (1842), and has taken the place of Darwin's hybrid word uniclinal.] but is now considered obsolete.cite book |author=United States Bureau of Mines; American Geological Institute |title=Dictionary of mining, mineral, and related terms |publisher=American Geological Institute in cooperation with the Society for Mining, Metallurgy, and Exploration, Inc |location=Alexandria, Va |year=1997 |pages= pp. 264, 600|isbn=0-922152-36-5 |quote=Homocline: A general term for a series of rock strata having the same dip … Unicline: An obsolete syn. of monocline.]

References