Ordovician යනු වසර මිලියන 485-444 කට පෙර Paleozoic යුගයේ දෙවන කාල පරිච්ඡේදය වේ,

Ordovician
485.4 ± 1.9 – 443.8 ± 1.5 Ma
Chronology
Etymology
Name formalityFormal
Name ratified1960
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitPeriod
Stratigraphic unitSystem
First proposed byCharles Lapworth, 1879
Time span formalityFormal
Lower boundary definitionFAD of the Conodont Iapetognathus fluctivagus
Lower boundary GSSPGreenpoint section, Green Point, Newfoundland, Canada
49°40′58″N 57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653
GSSP ratified2000[1]
Upper boundary definitionFAD of the Graptolite Akidograptus ascensus
Upper boundary GSSPDob's Linn, Moffat, U.K.
55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W / 55.4400; -3.2700
GSSP ratified1984[2][3]
Atmospheric and climatic data
Sea level above present day180 m; rising to 220 m in Caradoc and falling sharply to 140 m in end-Ordovician glaciations[4]

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  1. ^ Cooper, Roger; Nowlan, Godfrey; Williams, S. H. (March 2001). "Global Stratotype Section and Point for base of the Ordovician System" (PDF). Episodes. 24 (1): 19–28. doi:10.18814/epiiugs/2001/v24i1/005. සම්ප්‍රවේශය 6 December 2020.
  2. ^ Lucas, Sepncer (6 November 2018). "The GSSP Method of Chronostratigraphy: A Critical Review". Frontiers in Earth Science. 6: 191. Bibcode:2018FrEaS...6..191L. doi:10.3389/feart.2018.00191.
  3. ^ Holland, C. (June 1985). "Series and Stages of the Silurian System" (PDF). Episodes. 8 (2): 101–103. doi:10.18814/epiiugs/1985/v8i2/005. සම්ප්‍රවේශය 11 December 2020.
  4. ^ Haq, B. U.; Schutter, SR (2008). "A Chronology of Paleozoic Sea-Level Changes". Science. 322 (5898): 64–68. Bibcode:2008Sci...322...64H. doi:10.1126/science.1161648. PMID 18832639. S2CID 206514545.

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