Marcellus Formation - Geology - Fossils

Fossils

There are relatively sparse inclusions of fossilized marine fauna found in the Marcellus, but these fossils are still important to paleontology. For example, the Marcellus contains the oldest known diverse collection of thin-shelled mollusks still having well preserved shell microstructure. It is also where goniatites, an extinct shelled swimmer similar to a squid, make their first appearance in the fossil record. Life on land also enters the fossil record in the Marcellus, with the trunks of branchless conifer trees that floated out to sea to be preserved in the black shale.

Marcellus fossils include specimens of the large clam-like brachiopod Spinocyrtia. External molds of crinoids, plant-like animals related to starfish also known as "sea lilies," are found in the formation, with the molds partially filled with limonite; brachiopod and bivalve (clam) molds have also been found in the shale. Small conical tentaculitids are commonly found in the Chittenango Member. The Halihan Hill bed contains styliolinids and macrofauna including brachiopods, coral-like bryozoans, small bivalves and gastropods (snails), incorporated after the faunal turnover when Emsian and Eifelian Schoharie/Onondaga fauna were replaced by the Givetian Hamilton fauna.

The Solsville member contains well preserved bivalves, gastropods, and brachiopods. These shellfish lived in the benthic zone at the bottom of marginal marine to open marine environments that existed west of the ancient Catskill Delta. The fossil record in this member shows the base was dominated by deposit feeders, while the upper layers were dominated by filter feeders. This can be correlated to the lithology: the finer sediments of the shales at the base of this member would contain abundant adherent organic matter for deposit feeders, but would tend to foul the gills of filter feeders when suspended; the coarser sediments of the sandstones at the top would have contained less organic matter to support deposit feeders. Below the Solsville, at the base of the Otsego in eastern New York, a coral bed is found; another coral bed can be seen at the top of the Marcellus near Berne, New York.

A diverse, eel-like conodont fauna occurs in the limestone of the Cherry Valley Member, which is also known for its rich nautiloid and goniatite cephalopod fauna. Originally named the Goniatite Limestone, it produces their fossilized remains with shells that can be larger than .3 metres (1 ft) across. It also contains the "Cephalopod Graveyard" in the Schoharie Valley of eastern New York, an unusual accumulation of abundant coiled and straight shells of several types of large adult cephalopods. This bed lacks juvenile fossils, indicating that if their behavior was similar to modern squid, this may have been an area where these Devonian cephalopods reproduced and died. This stratigraphic interval also provides an excellent example of incursion epiboles, which are sudden appearances and disappearances of fossil taxa in relatively thin sections of the rock unit. In the Cherry Valley, the taxa do not reoccur; instead each thin concretionary limestone bed contains different species of goniatites. The Cherry Valley and Union Springs also contain well-preserved anarcestida.