View source for Earth:Siderian

{{short description|First period of the Paleoproterozoic Era}}
{{Infobox geologic timespan
| name                         = Siderian
| color                        = Siderian
| top_bar                      = all time
| time_start                   = 2500
| time_end                     = 2300
| image_map                    =2400 Ma paleoglobe.png
| caption_map                  =A reconstruction of the Earth's continents during the middle Siderian, circa 2.4 Ga. 
| image_outcrop                = Banded iron formation Dales Gorge.jpg
| caption_outcrop              = A Siderian banded iron formation in Dales Gorge, Western Australia
| image_art                    = Snowball Huronian.jpg
| caption_art                  = Artist's impression of the Earth during the [[Earth:Huronian glaciation|Huronian glaciation]], starting from mid-Siderian
<!--Chronology-->  
| timeline                     = Siderian
| proposed_boundaries1         = 2630–2420 Ma
| proposed_boundaries1_ref     = Gradstein et al.
| proposed_part1               = [[Earth:Neoarchean|Neoarchean]]
| proposed_part1_ref           = Gradstein et al.
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
| synonym2_coined              =
| synonym3                     =
| synonym3_coined              =
<!--Usage Information--> 
| celestial_body               = earth
| usage                        = Global ([[Organization:International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
<!--Definition-->
| chrono_unit                  = Period
| strat_unit                   = System
| proposed_by                  =
| timespan_formality           = Formal
| lower_boundary_def           = Defined Chronometrically
| lower_gssa_accept_date       = 1991<ref name=Plumb1991>{{cite journal |last=Plumb |first=K. A. |date=June 1, 1991 |title=New Precambrian time scale |journal=Episodes |doi=10.18814/epiiugs/1991/v14i2/005 |volume=14 |issue=2 |pages=139–140|doi-access=free }}</ref>
| upper_boundary_def           = Defined Chronometrically
| upper_gssa_accept_date       = 1991<ref name=Plumb1991/>
<!--Atmospheric and Climatic Data-->
| o2                           =
| co2                          =
| temp                         =
| sea_level                    =
}}
The '''Siderian Period''' ({{IPAc-en|pron|s|aɪ|ˈ|d|ɪər|i|.|ə|n|,_|s|I|-}}; {{lang-grc|σίδηρος|sídēros}}, meaning "iron") is the first geologic period in the [[Earth:Paleoproterozoic|Paleoproterozoic]] [[Earth:Era (geology)|Era]] and lasted from {{Period start|Siderian}} [[Megaannum|Ma]] to {{Period start|Rhyacian}} Ma. Instead of being based on [[Earth:Stratigraphy|stratigraphy]], these dates are defined [[Physics:Absolute dating|chronometrically]].

The deposition of [[Earth:Banded iron formation|banded iron formation]]s peaked early in this period. These iron rich formations were formed as anaerobic [[Biology:Cyanobacteria|cyanobacteria]] produced waste [[Chemistry:Oxygen|oxygen]] that combined with [[Chemistry:Iron|iron]], forming [[Chemistry:Magnetite|magnetite]] (Fe<sub>3</sub>O<sub>4</sub>, an [[Chemistry:Iron oxide|iron oxide]]). This process removed iron from the Earth's oceans, presumably turning greenish seas clear. Eventually, with no remaining iron in the oceans to serve as an oxygen sink, the process allowed the buildup of an oxygen-rich atmosphere. This second, follow-on event is known as the oxygen catastrophe, which, some geologists believe triggered the [[Earth:Huronian glaciation|Huronian glaciation]].<ref>{{cite journal |title=Paleoclimates: The First Two Billion Years |first1=James F. |last1=Kasting |first2=Shuehi |last2=Ono |year=2006 |journal=Philosophical Transactions: Biological Sciences |volume=361 |issue=1470 |pages=917–929 |doi=10.1098/rstb.2006.1839 |jstor=20209693|pmc=1868609 |pmid=16754607}}</ref><ref>{{cite journal |title=The Paleoproterozoic Snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis |first1=Robert E. |last1=Kopp |first2=Joseph L. |last2=Kirschvink |first3=Isaac A. |last3=Hilburn |first4=Cody Z. |last4=Nash |journal=PNAS |year=2005 |volume=102 |issue=32 |pages=11131–11136 |doi=10.1073/pnas.0504878102|url=http://authors.library.caltech.edu/1015/1/KOPpnas05.pdf |pmid=16061801 |pmc=1183582|doi-access=free }}</ref>

Since the time period from 2420&nbsp;Ma to 2250&nbsp;Ma is well-defined by the lower edge of iron-deposition layers, an alternative period named the '''Oxygenian''', based on stratigraphy instead of chronometry, was suggested in 2012 in a geological timescale review.<ref name="Gradstein_et_al_2012">{{cite book |title=The Geologic Time Scale 2012 |publisher=Elsevier |editor1-last=Gradstein |editor1-first=F. M. |display-editors=etal |year=2012 |volume=1 |pages=361–365 |isbn=978-0-44-459390-0}}</ref>

== References ==
{{Reflist}}

* {{cite web | title=Siderian Period | work=GeoWhen Database | url=http://www.stratigraphy.org/upload/bak/geowhen/stages/Siderian.html | access-date=May 24, 2015}}
* [http://www.dinosaurfact.net/Proterozoic/Siderian.php "The Siderian"]. Dinosaurfact.net. Retrieved May 24, 2015.


[[Category:Paleoproterozoic]]
[[Category:Geological periods]]


{{Sourceattribution|Siderian}}