Isle La Motte, dove-coloured limestone, Crown Point-Valcour Fm (Ordovician of the United States)

Where: Vermont (44.9° N, 73.3° W: paleocoordinates 28.0° S, 54.6° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Chazy Group, Chazy (466.0 - 457.5 Ma)

• formation-level stratigraphic resolution

Environment/lithology: lithified limestone

• Details of the divisions at each of the localities from which each specimen listed are not given, thus I will give a complete description of lithologies summarized by Ruedemann for the formation at two different localities. “Section of the Chazy beds at Valcour in ascending order: The Chazy beds at Valcour form a low anticline. B1, a hard, compact, gray limestone, exposed at water edge, on land of Ezra Day. 2 feet of its top exposed. B2, same rock. 6 inches. B3, gray, shaly impure limestone with mud seams; very fossiliferous. 1 foot 4 inches. B4, more crystalline limestone with darker shaly intercalations. 1 foot 10 inches. Contains numerous small bryozoan reefs and other fossils; also many cephalopods in its upper layer (just north of fence diving lands of George and Ezra Day). B5, darker, impure shaly limestone. 1 foot 6 inches. Contains some large nautiloids. B6, a gray shaly limestone, 3 feet, containing a rich fauna (Bolboporites, Malocystites, brachipods, trilobites). B7, series of heavier, dark gray beds with abundant plates of Palaocystites. 7a-10 inches, barren; 7b-14 inches, in lower 3 inches full of trilobites; 7c-3 feet 6 inches, barren; 7c2-8 inches, hard crystalline gray limestone with trilobites. B8, 5 ½ feet of dark shaly limestone, nearly bluish gray and very fossiliferous, containing orthoceracones. Since we can do no better than base our future stratigraphic work on the larger lithologic divisions recognized by Brainerd and Seely in the Beekmantown formation at East shore ham Vt. And in the Chazy formation at Chazy village, we refer the fossils obtained at other places than the Valcour shore provisionally to those divisions.”

Size class: macrofossils

Primary reference: R. Ruedemann. 1906. Cephalopoda of the Beekmantown and Chazy formations of the Champlain Basin. Bulletin of the New York State Museum, Paleontology 14:389-611 [P. Wagner/K. Koverman/M. Uhen]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 171795: authorized by Björn Kröger, entered by Björn Kröger on 20.07.2015

Creative Commons license: CC BY (attribution)

Taxonomic list

 Orthocerida - Proteoceratidae
"Spyroceras clintoni" = Stereospyroceras clintoni Miller 1877
Cyrtactinoceras boycii Whitfield 1886
 Orthocerida - Orthoceratidae
Orthoceras vagum Ruedemann 1906
Orthoceras modestum Ruedemann 1906
 Tarphycerida - Tarphyceratidae
 Oncocerida - Oonoceratidae
Ooceras perkinsi Ruedemann 1906