Sandbian

The Sandbian is the first stage of the Upper Ordovician. It follows the Darriwilian and is succeeded by the Katian. Its lower boundary is defined as the first appearance datum of the graptolite species Nemagraptus gracilis around 458.4 million years ago. The Sandbian lasted for about 5.4 million years until the beginning of the Katian around 453 million years ago.^[7]

Sandbian
458.4 ± 0.9 – 453.0 ± 0.7 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Chronology
−485 — – −480 — – −475 — – −470 — – −465 — – −460 — – −455 — – −450 — – −445 — – P a l e o z o i c Ꞓ O r d o v i c i a n S F E a r l y M i d d l e L a t e L Stage 10 Tremadocian Floian Dapingian Darriwilian Sandbian Katian Hirnantian Rhuddanian       ← First land plant spores[1] ← Ordovician meteor event[2][3] Subdivision of the Ordovician according to the ICS, as of 2021.[4] Vertical axis scale: millions of years ago.
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the Graptolite Nemagraptus gracilis
Lower boundary GSSP	Fågelsång section, Sularp Brook, Skåne, Sweden 55.7137°N 13.3255°E / 55.7137; 13.3255
Lower GSSP ratified	2002[5]
Upper boundary definition	FAD of the Graptolite Diplacanthograptus caudatus
Upper boundary GSSP	Black Knob Ridge section, Oklahoma, United States 34.4305°N 96.0746°W / 34.4305; -96.0746
Upper GSSP ratified	2006[6]

Naming

The name Sandbian is derived from the village Södra Sandby (Lund Municipality, Skåne County, Sweden). The name was proposed in 2006.^[8]

GSSP

The GSSP of the Sandbian is the Fågelsång section (55.7137°N 13.3255°E / 55.7137; 13.3255) at Sularp Brook, east of Lund (Skåne, Sweden). It is an outcrop of shale and mudstone. The lower boundary of the Sandbian is defined as the first appearance datum of graptolite species Nemagraptus gracilis in that section.^[9]

References

1. Wellman, C.H.; Gray, J. (2000). "The microfossil record of early land plants". Phil. Trans. R. Soc. B. 355 (1398): 717–732. doi:10.1098/rstb.2000.0612. PMC 1692785. PMID 10905606.
2. Korochantseva, Ekaterina; Trieloff, Mario; Lorenz, Cyrill; Buykin, Alexey; Ivanova, Marina; Schwarz, Winfried; Hopp, Jens; Jessberger, Elmar (2007). "L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40 Ar- 39 Ar dating". Meteoritics & Planetary Science. 42 (1): 113–130. Bibcode:2007M&PS...42..113K. doi:10.1111/j.1945-5100.2007.tb00221.x.
3. Lindskog, A.; Costa, M. M.; Rasmussen, C.M.Ø.; Connelly, J. N.; Eriksson, M. E. (2017-01-24). "Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification". Nature Communications. 8: 14066. doi:10.1038/ncomms14066. ISSN 2041-1723. PMC 5286199. PMID 28117834. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated
4. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
5. Bergström, Stig; Finney, S.; Xu, Chen; Pålsson, Christian; Zhi-hao, Wang; Grahn, Yngve (June 2000). "A proposed global boundary stratotype for the base of the Upper Series of the Ordovician System: The Fågelsång section, Scania, southern Sweden". Episodes. 23 (2): 102–109. doi:10.18814/epiiugs/2000/v23i2/003. Retrieved 13 December 2020.
6. Goldman, Daniel; Leslie, Stephen; Nõlvak, Jaak; Young, Seth; Bergström, Stig; Huff, Warren (December 2007). "The Global Stratotype Section and Point (GSSP) for the base of the Katian Stage of the Upper Ordovician Series at Black Knob Ridge, Southeastern Oklahoma, USA". Episodes. 30 (4): 258–270. doi:10.18814/epiiugs/2007/v30i4/002. Retrieved 13 December 2020.
7. "GSSP Table - Paleozoic Era". Geologic Timescale Foundation. Retrieved 2 December 2012.
8. Bergström, Stig; Finney, Stanley; Xu, Chen; Goldman, Daniel; Leslie, Stephen (31 August 2006). "Three new Ordovician global stage names". Lethaia. 39 (3): 287–288. doi:10.1080/00241160600847439.
9. Bergström, Stig M.; S. C. Finney; Chen Xu; Christian Pålsson; Wang Zhi-hao; Yngve Grahn (2000). "A proposed global boundary stratotype for the base of the Upper Series of the Ordovician System: The Fågelsång section, Scania, southern Sweden" (PDF). Episodes. 23 (2): 102–109. doi:10.18814/epiiugs/2000/v23i2/003. Retrieved 20 September 2012.