Chazy Formation

The Chazy Reef Formation is a mid-Ordovician limestone deposit in northeastern North America.

It consists of some of the oldest

stromatoporoids

.

The formation is named for the small town of

gastropod shells. Rock of the Chazy Formation was quarried from the nineteenth century at the Fisk Quarry, Isle La Motte, the oldest quarry in Vermont.^[5] Portions of the exposed reef on several islands in Lake Champlain were dedicated as the Chazy Fossil Reef National Natural Landmark in 2009.^[6]

The system formed in warm tropical waters of the

global paleoclimate was so warm that the planet was all but ice-free. Atmospheric carbon dioxide

was fourteen to sixteen times more plentiful than it is today.

The Chazy Reef Formation, which built up vertically from a muddy base catching fine dark silt as it grew, began as mounds deposited by bryozoans that stabilized a muddy bottom, then built up into the water column to such an extent that the connected mounds modified their surrounding environment (Mehrtens). As the reef aged, it began to offer an increasing variety of ecological niches, which fostered the first rich local

faunal succession

.

The Chazy Reef Formation has given its name to the contemporaneous mid-Ordovician

faunal stage

, the Chazyan.

Notes

^ P.E. Raymond of Harvard called it "the oldest coral reef in the world" (Raymond 1924), though coral rubble was not in fact the primary reef building material.
^ Percy E. Raymond, "The Trilobites of the Chazy Limestone", Annals of the Carenegie Museum 3.2 (1905): "...the forty years which have elapsed since the distinguished Canadian paleontologist, Elkanah Billings, published his descriptions of Chazy fossils".
^ H. J. Hofmann, "Ordovician Chazy Group in southern Quebec" AAPG Bulletin 47.2 (February 1963:270-301) retrieved November 30, 2008
^ The quarrymen's term was noted by Raymond 1905.
^ The blackest stone may be seen in the polished "marble" revetments—actually unmetamorphosed limestone— inside Radio City Music Hall, New York, and in floors in the Vermont State House.
^ "Chazy Fossil Reef". National Natural Landmarks Program. National Park Service. June 28, 2012. Retrieved September 16, 2016.

Chazy Formation

Notes

External links

Further reading