BG99-13, middle reaches of Ushakova River, central part of Island (Silurian of Russian Federation)

Where: Severnaya Zemlya, Russian Federation (79.7° N, 96.5° E: paleocoordinates 4.6° N, 1.1° E)

• coordinate stated in text

• outcrop-level geographic resolution

When: Sredninskaya Formation, Telychian (438.5 - 433.4 Ma)

• These rocks were previously referred to as part of the Golomyannaya Formation (Menner et al. 1979; Bogolepova et al. 2000). Graptolites provide firm evidence of the age of these strata, indicating a level between the upper part of the crispus and the griestoniensis Biozones (Bogolepova et al. 2000).

• formation-level stratigraphic resolution

Environment/lithology: black mudstone

• The depositional environment of these sediments, between two relatively shallow shelf facies with low biodiversity, but abundant and distinctive faunas, implies that they should also be placed within the shelf (topographic lows) environment probably deposited during a transgressive phase. The black shales hosting the concretions have graptolite-dominated assemblages, with a few cephalopods and very rare brachiopods and chitinozoans indicating an oxygen and nutrient-rich part of the water column. By comparison, the more rich associations occur in calcareous nodules represented by varying admixtures of graptolites, cephalopods, bivalves, ostracodes, gastropods, brachiopods, algae, machaeridians and conodonts. The presence of shelf shelly benthos and current oriented fossils indicates that the basin was periodically oxygenated.

Size class: macrofossils

Collection methods: Specimens at PMU

Primary reference: O. K. Bogolepova, A. P. Gubanov, and V. I. Pease. 2005. Bohemian-type Silurian (Telychian) bivalves from Arctic Russia. Geologiska Föreningen 127(4):247-252 [P. Wagner/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 85024: authorized by Pete Wagner, entered by Pete Wagner on 21.11.2008

Creative Commons license: CC BY (attribution)

Taxonomic list

Plumulites sp. Barrande 1872 scale worm
 Murchisoniina - Loxonematidae
Loxonema sp. Phillips 1841 snail
 Euomphalina - Holopeidae
Holopea sp. Hall 1847 snail
 Cyrtodontida - Antipleuridae
Sibirinka sp. Bogolepova and Kříž 1995 clam
? Dualina sp. Barrande 1881 clam
 Solemyida - Ctenodontidae
Ctenodonta sp. Salter 1852 clam
 Discosorida - Phragmoceratidae
Phragmoceras sp. Broderip 1839
 Oncocerida - Trimeroceratidae
 Dissidocerida - Geisonoceratidae
Geisonoceras sp. Hyatt 1884
 Orthocerida - Kionoceratidae
Kionoceras sp. Hyatt 1884
 Atrypida -
Zygospiraella sp. Nikiforova 1961
 Atrypida - Atrypinidae
 Orthida - Rhipidomellidae
Dalejina sp. Havlicek 1953
 Graptoloidea - Monograptidae
Stimulograptus sp. Přibyl and Štorch 1983 graptolite