Rhuddanian

In the geologic timescale, the Rhuddanian is the first age of the Silurian period and of the Llandovery epoch. The Silurian is in the Paleozoic era of the Phanerozoic eon.[3] The Rhuddanian age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (million years ago). It succeeds the Himantian Age (the last age of the Ordovician Period) and precedes the Aeronian age.[4]

Epochs in the Silurian
-444 —
–
-442 —
–
-440 —
–
-438 —
–
-436 —
–
-434 —
–
-432 —
–
-430 —
–
-428 —
–
-426 —
–
-424 —
–
-422 —
–
-420 —
–
-418 —
Epochs of the Silurian Period.
Axis scale: millions of years ago.

GSSP

The GSSP for the Silurian is located in a section at Dob's Linn, Scotland, in an artificial excavation created just north of the Linn Branch Stream. Two lithological units (formations) occur near the boundary.[3] The lower is the Hartfell Shale (48 metres (157 ft) thick), consisting chiefly of pale gray mudstone with subordinate black shales and several interbedded meta-bentonites.[3] Above this is the 43 metres (141 ft) thick Birkhill Shale, which consist predominantly of black graptolitic shale with subordinate gray mudstones and meta-bentonites.[5]

Palaeontology

Agnathans
Agnathans of the Rhuddanian
Taxa Presence Location Description Images
Rhuddanian-Telychian It had an elongated body and a dorsal fin and an anal fin near the back third of its body.
Jamoytius kerwoodi

Molluscs

Cephalopods
Cephalopods of the Rhuddanian
Taxa Presence Location Description Images
Dapingian-Homerian The shallow seas of Laurentia, Baltica and Siberia.[6] Head was soft muscular tissue at the opening of hard cone-like shell.
Cameroceras, shown feeding on a Aphetoceras, while a quartet of Cyclostomiceras swim by.

See also
  • Ordovician-Silurian extinction events

References
  1. Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
  2. Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
  3. Gradstein, Felix M.; Ogg, James G.; Smith, Alan G. (2004). A Geologic Time Scale 2004. ISBN 9780521786737.
  4. "GSSP Table - All Periods". International Commission on Stratigraphy. Retrieved 15 September 2018.
  5. "GSSP for the Rhuddanian Stage". International Commission on Stratigraphy.
  6. Frey, R.C. 1995. "Middle and Upper Ordovician nautiloid cephalopods of the Cincinnati Arch region of Kentucky, Indiana, and Ohio" (PDF). U.S. Geological Survey, p.73


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