Editing Varve (section)

==Formation==
[[File:Fahrrad-ostern-2006-bluefish-01.jpg|thumb|upright=1.35|Varves formed during the [[Weichselian glaciation]], near [[Eberswalde]], Germany]]
Varves form in a variety of [[marine (ocean)|marine]] and [[Lake|lacustrine]] [[sedimentary depositional environment|depositional environments]] from [[season]]al variation in [[clastic]], biological, and chemical sedimentary processes.

The classic varve [[archetype]] is a light / dark coloured couplet deposited in a lake basin. During summer months, light laminae (thin layers) composed of silica and calcium carbonate are deposited. This is the consequence of dead [[phytoplankton]], and other micro-organisms that create their skeletons or shells out of silica or calcium carbonate, falling to the lake bottom. This process of the precipitation and deposition of dead micro-organisms out of the water column is restricted to warm months when [[productivity (ecology)]] is high. The corresponding dark colored layers are composed of organic matter and fine sediment particles transported and deposited during spring [[Freshet|freshets]] as a result of winter snowmelt. The alternation of these two distinct layers allows for high-precision dating of sediment profiles, for each couplet is equivalent to one year.

In addition to seasonal variation of sedimentary processes and deposition, varve formation requires the absence of [[bioturbation]]. Consequently, varves commonly form under [[anoxic sea water|anoxic]] conditions.

A well-known marine example of varved sediments are those found in the Santa Barbara basin, off [[California]].<ref>{{cite journal
 | author1 = Thunell, R.C.|author-link1=Robert Thunell
 |author2=Tappa, E. |author3=Anderson, D.M. 
 | date = 1995-12-01
 | title = Sediment fluxes and varve formation in Santa Barbara Basin, offshore California
 | journal = Geology
 | volume = 23
 | issue = 12
 | pages = 1083–1086
  | doi = 10.1130/0091-7613(1995)023<1083:SFAVFI>2.3.CO;2
 | url = http://geology.geoscienceworld.org/cgi/content/abstract/23/12/1083
 | access-date = 2007-04-27
|bibcode = 1995Geo....23.1083T | url-access = subscription
 }}</ref> Another long record of varved sediments is the palaeo-lacustrine record of the Piànico–Sèllere Basin (southern Alps).<ref>{{Cite journal|date=2000-11-01|title=A long lacustrine record from the Piànico-Sèllere Basin (Middle-Late Pleistocene, Northern Italy)|url=https://www.sciencedirect.com/science/article/abs/pii/S1040618200000641|journal=Quaternary International|language=en|volume=73-74|pages=47–68|doi=10.1016/S1040-6182(00)00064-1|issn=1040-6182|last1=Moscariello|first1=Andrea|last2=Ravazzi|first2=Cesare|last3=Brauer|first3=Achim|last4=Mangili|first4=Clara|last5=Chiesa|first5=Sergio|last6=Rossi|first6=Sabina|last7=De Beaulieu|first7=Jacques-Louis|last8=Reille|first8=Maurice|issue=1|bibcode=2000QuInt..73...47M|url-access=subscription}}</ref> Here, the detrital layer part of each varve was used as a proxy for 771 palaeofloods which occurred over a period of 9.3 thousand years during an interglacial period in the Pleistocene.<ref>{{Cite journal|last1=Witt|first1=A|last2=Malamud|first2=BD |last3=Mangili|first3=C|last4=Brauer|first4=A|date=2017-11-14|title=Analysis and modelling of a 9.3 kyr palaeoflood record: correlations, clustering, and cycles|url=https://hess.copernicus.org/articles/21/5547/2017/|journal=Hydrology and Earth System Sciences|language=English|volume=21|issue=11|pages=5547–5581|doi=10.5194/hess-21-5547-2017|issn=1027-5606|doi-access=free}}</ref><ref>{{Cite journal|last1=Mangili|first1=C|last2=Witt|first2=A|last3=Malamud|first3=B|last4=Brauer|first4=A|date=2017-08-21|title=Detrital layer frequency in a 9336 year varved sequence within the Pianico-Sellere Palaeolake (Southern Alps, Italy) [Downloadable Data]|publisher=PANGAEA - Data Publisher for Earth & Environmental Science|doi=10.1594/PANGAEA.879779|url=https://doi.pangaea.de/10.1594/PANGAEA.879779}}</ref>