Ordovician

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

Ordovician
485.4 ± 1.9 – 443.8 ± 1.5 Ma PreЄ Є O S D C P T J K Pg N
Chronology
සැකිල්ල:Ordovician graphical timeline
Etymology
Name formality	Formal
Name ratified	1960
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Period
Stratigraphic unit	System
First proposed by	Charles Lapworth, 1879
Time span formality	Formal
Lower boundary definition	FAD of the Conodont Iapetognathus fluctivagus
Lower boundary GSSP	Greenpoint section, Green Point, Newfoundland, Canada 49°40′58″N 57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653
GSSP ratified	2000
Upper boundary definition	FAD of the Graptolite Akidograptus ascensus
Upper boundary GSSP	Dob's Linn, Moffat, U.K. 55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W / 55.4400; -3.2700
GSSP ratified	1984
Atmospheric and climatic data
Sea level above present day	180 m; rising to 220 m in Caradoc and falling sharply to 140 m in end-Ordovician glaciations

මූලාශ්‍ර

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.