Orchard Creek Exposure, 1.6 km north of Thebes (Ordovician of the United States)

Where: Alexander County, Illinois (37.2° N, 89.5° W: paleocoordinates 24.5° S, 61.5° W)

• coordinate based on political unit

• outcrop-level geographic resolution

When: Girardeau Limestone Formation, Hirnantian (445.2 - 443.4 Ma)

Environment/lithology: limestone

• The Girardeau is composed of two alternating lithologies which are cyclically interbedded in units ranging from two to four inches (5.1 to 10.2 cm) thick. The predominant rock in a single cycle (about 75 to 80%) is a dark green massive and unlaminated lithographic limestone. Most of this material represents clay-sized and silt-sized calcite, although clay minerals are present.

Size class: macrofossils

Primary reference: J. C. Brower. 1973. Crinoids from the Girardeau Limestone (Ordovician). Palaeontographia Americana 7(46):263-499 [G. Webster/G. Webster]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 201761: authorized by Pete Wagner, entered by Pete Wagner on 26.05.2019

Creative Commons license: CC BY (attribution)

Taxonomic list

Crinoidea
 Monobathrida - Patelliocrinidae
 Monobathrida - Hapalocrinidae
 Monobathrida - Melocrinitidae