New Jersey Amber, sometimes called Raritan amber, is amber found in the Raritan and Magothy Formations of the Central Atlantic (Eastern) coast of the United States. It is dated to the Late Cretaceous, Turonian age, based on pollen analysis of the host formations. It has been known since the 19th century, with several of the old clay-pit sites now producing many specimens for study. It has yielded a number of organism fossils, including fungi, plants, tardigrades, insects and feathers. The first identified Cretaceous age ant was described from a fossil found in New Jersey in 1966.
Occurrence
Though named after New Jersey, the fossil-bearing strata of the Raritan and overlying Magothy formations are also exposed in several neighboring U.S. states, including Maryland through south and central New Jersey, across Staten Island and Long Island (coastal areas of New York state), to a northern exposure at Martha's Vineyard, an island of Massachusetts.
Of the two formations that New Jersey amber is found in, the Raritan Formation underlies the Magothy Formation. The Magothy formation is reported by Wilson's 1967 paper describing Sphecomyrma freyi as having exposures in Maryland, New Jersey, New York, Delaware, and other unspecified islands along the New England coastline. The formation consists of gray to dark brown clay beds interlayered in light-colored sands. In the clay layers are lignite lenses, leaf impressions, and the amber. At the time of the paper's publication, the age was uncertain, and given by Wilson and Carpenter as approximately 100 million years old. Amber deposits of the Raritan Formation are mainly in the Old Bridge sand member and South Amboy Fire Clay Member, with the latter being fossilized in situ, with no disturbance after deposition. Palynological dating of the South Amboy Fire clay has returned a Turonian age, placing the members in the Complexiopollis – Santanacites palynostratigraphic zones.
Amber specimens are recovered from the South Amboy Fire Clay member, part of the Raritan Formation. Deposited in lagoons and saltwater marshes along the Cretaceous eastern seaboard. The lithology exposed in the Crossmans clay pits shows that the lagoons and marshes had brackish water channels where water flow diminished and anoxic conditions formed. This is supported by the presence of pyrite and marcasite on and around amber specimens, with some amber totally encased in the iron sulphides. The number of insect groups that need fresh water to survive, such as caddisflies, indicates that fresh water was close to the delta area.
Amber was first mentioned in 1821 by naturalist Gerard Troost, who described a specimen which contained a group of fossil scale insects from an outcrop at Cape Sable, Maryland. Hollick reported in 1905 that during the height of clay mining at the turn of the 20th century, amber was found in such volumes that it was saved, and burned during the winter for heat. A number of the clay mines are now sources of amber for study. The White Oaks site (or White Oaks pit) is part of the Old Crossman's pit clay mine in Sayreville, New Jersey. It contains outcrops of the amber-bearing South Amboy Fire Clay that are noted to be rich in inclusions.