The Matawan Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

and

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

. It preserves fossils dating back to the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

. A description of the formation in Maryland from the

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...

''Tolochester Folio'' (1917) follows: :The formation consists chiefly of

glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () me ...

sand intimately mixed with dark-colored clay, but all through the material small flakes of mica are abundant. In some places the deposits consist almost entirely of black clay; in others, particularly where the upper beds are exposed, the arenaceous phase is predominant, and some beds consist entirely of sand ranging in color from white to dark greenish-black. Where the glauconite decomposes, the iron oxidizes and the materials are stained reddish-brown and in places are firmly indurated by the iron oxide. In places a small layer of gravel lies at the base of the formation. Small amounts of pyrite are occasionally seen. A prominent feature in several exposures of the Matawan formation in this quadrangle is the presence of large spherical to oblong concretions of clay ironstone, in places very numerous and attaining a length of 5 feet and a thickness of 3 feet. They stand erect in the formation in most places. In the erosion of the bluffs of the formation, they persist long after the inclosing loose sands and sandy clays have been removed and are found scattered over the beaches in large numbers. They are especially noticeable on Dutch Ship Island, on the west side of Gibson Island, and in the high bluff at the mouth of Lloyd Creek.Tolchester folio, Maryland
Folios of the Geologic Atlas 204, by B. L. Miller, E. B. Mathews, A. B. Bibbins, and H. P. Little, 1917.

References

* Cretaceous Maryland Cretaceous geology of New Jersey Cretaceous Delaware {{Maryland-geologic-formation-stub

See also

References