{{Short description|Geological indicator of water flow}} [[Image:WaveRipple.JPG|thumb|Bidirectional wave ripple, [[Nomgon]], [[Mongolia]]]] A '''paleocurrent''' or '''paleocurrent indicator''' is a [[geological]] feature (typically a [[sedimentary structure]]) that helps one determine the direction of flowing [[water]] in the geologic past. This is an invaluable tool in the reconstruction of ancient [[depositional environment]]s.<ref>Prothero, D. R. and Schwab, F., 1996, ''[[Sedimentary Geology (journal)|Sedimentary Geology]]'', pg. 48–51, {{ISBN|0-7167-2726-9}}</ref>
There are two main types of paleocurrent indicators:
*''Unidirectional'', which give a clear, single direction of flow *''Bidirectional'', which give a good linear direction, but it is unclear which direction along the linear trend the water flowed.
Paleocurrents are usually measured with an [[azimuth]], or as a [[Rake (geology)|rake]] on a bedding plane, and displayed with a [[Pie chart#Polar area diagram|Rose Diagram]] to show the dominant direction(s) of flow. This is needed because in some depositional environments, like [[meandering river]]s, the paleocurrent resulting from natural sinuosity has a natural variation of 180 degrees or more.<ref>{{Cite journal | last = Miaoa | first = Xiaodong |author2=Huayu Lua |author3=Zhen Lid |author4=Guangchao Caod | title = Paleocurrent and fabric analyses of the imbricated fluvial gravel deposits in Huangshui Valley, the northeastern Tibetan Plateau, China | journal = [[Geomorphology (journal)|Geomorphology]] | volume = 99 | issue = 1–4 | pages = 433–442 | publisher = © 2007 Elsevier B.V. | date = July 2008 | doi = 10.1016/j.geomorph.2007.12.005 |bibcode = 2008Geomo..99..433M }}</ref>
Below are a partial list of common paleocurrent indicators:
==Unidirectional== [[Image:FluteCast.JPG|thumb|Flute cast, showing paleocurrent to the upper right of pic]] *[[Cross-bedding]] – the axis of a trough cross bed or the down-dip direction of a tabular cross bed point the direction of paleo flow. *Current [[ripple mark]]s – will have the short side of the ripple pointing down stream. *[[Sole markings]]/[[flute cast]]s – the short, steep side will point up stream, and the long, tapered side points down stream. *[[Imbrication (sedimentology)|Imbrication]] – clasts line up in the direction of flow.
==Bidirectional== [[Image:PartingLineation.JPG|thumb|200px|Parting lineation, from lower right to upper left; [[Kayenta Formation]], [[Canyonlands National Park]].]] *Symmetrical [[ripple mark]]s – flow is perpendicular to the ridge crest. *[[Tool mark]] – flow is along the mark. *[[Parting lineation]]s – flow is along the grains.
==References==
{{Wikibooks|Historical Geology|Paleocurrents}} <references/>
[[Category:Sedimentology]]
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