Editing Concretion (section)

=== Claystones, clay dogs, and fairy stones ===
Disc concretions composed of [[calcium carbonate]] are often found eroding out of exposures of interlaminated [[silt]] and [[clay]], [[varve]]d, [[proglacial lake]] deposits. For example, great numbers of strikingly symmetrical concretions have been found eroding out of outcrops of [[Quaternary]] proglacial lake [[sediment]]s along and in the [[gravel]]s of the [[Connecticut River]] and its tributaries in [[Massachusetts]] and [[Vermont]]. Depending the specific source of these concretions, they vary in an infinite variety of forms that include disc-shapes; crescent-shapes; watch-shapes; cylindrical or club-shapes; botryoidal masses; and animal-like forms. They can vary in length from {{convert|2|in|cm|abbr=on|sp=us}} to over {{convert|22|in|cm|abbr=on|sp=us}} and often exhibit concentric grooves on their surfaces. In the [[Connecticut River Valley]], these concretions are often called "claystones" because the concretions are harder than the clay enclosing them. In local brickyards, they were called "clay-dogs" either because of their animal-like forms or the concretions were nuisances in molding bricks.<ref name="Gratacap1884a">{{cite journal |last1=Gratacap |first1=L.P. |year=1884 |title=Opinions Upon Clay Stones and Concretions |journal=The American Naturalist |volume=18 |number=9 |doi=10.1086/273756 |pages=882–892 |bibcode=1884ANat...18..882G |s2cid=84690956 |url=https://www.journals.uchicago.edu/doi/pdf/10.1086/273756 |access-date=18 August 2021|url-access=subscription }}</ref><ref name="Sheldon1900a">{{cite book |last1=Sheldon |first1=J.M.A. |year=1900 |title=Concretions from the Champlain clays of the Connecticut Valley |publisher=University Press |location=Boston |page=74 |url=https://books.google.com/books?id=tUkPAAAAYAAJ&dq=Sheldon,+J.M.A.,+1900.+%27%27Concretions+from+the+Champlain+clays+of+the+Connecticut+Valley.%27%27+University+Press,+Boston.+pp.74.&pg=PA7 |access-date=18 August 2021}}</ref><ref name="Tarr1935a">{{cite journal |last1=Tarr |first1=W. A. |title=Concretions in the Champlain formation of the Connecticut River Valley |journal=Geological Society of America Bulletin |date=31 October 1935 |volume=46 |issue=10 |pages=1493–1534 |doi=10.1130/GSAB-46-1493|bibcode=1935GSAB...46.1493T }}</ref> Similar disc-shaped calcium carbonate concretions have also been found in the [[Harricana River]] valley in the [[Abitibi-Témiscamingue]] administrative region of [[Quebec]], and in [[Östergötland]] county, Sweden. In [[Scandinavia]], they are known as "marlekor" ("fairy stones").<ref name="Kindle1923a">{{cite journal |last1=Kindle |first1=E. M. |title=Range and Distribution of Certain Types of Canadian Pleistocene Concretions |journal=Geological Society of America Bulletin |date=30 September 1923 |volume=34 |issue=3 |pages=609–648 |doi=10.1130/GSAB-34-609|bibcode=1923GSAB...34..609K }}</ref><ref name="Warkentin1967a">Warkentin, B.P., 1967. ''Carbonate content of concretions in varved sediments''. ''Canadian Journal of Earth Sciences'', 4(2), pp.333-333.</ref>