Cenomanian


Cenomanian

-|The Cenomanian age (also known as Woodbinian [depreciated by the ICS] ) is the "first or earliest or oldest" Geochronological "geologic age" of the Late Cretaceous Epoch. Like all geological time units the Cenomanian age is associated with a Chronostratigraphic stratum or "geologic stage" (or faunal stage—see biostratigraphy and geobiology) of the same name, the "Cenomanian stage" (and its relationship to the parents epochs' strata, called a series, is that it is one of many in the series). Each belong to the Cretaceous period and Cretaceous system as well.

Terminology

The strata "characteristic of the geological stage" were identified by various means as having been "laid down during the corresponding age". The terms upper and lower refer to the strata and stage (or other larger chronostratigraphic units) whereas" 'late' "and" 'early' "generally refer to relative time measures, which is to say late or middle or early modify when withing 'the age' (or hierarchically larger) time unit.

The Cenomanian units

As a unit of geologic time measure, the Cenomanian age spans the time betweencite web|url=http://www.stratigraphy.org/chus.pdf|accessdate=2008-06-17|title=International Stratigraphic Chart|author=International Commission on Stratigraphy] 99.6 ± 0.9 MA|1 and 93.5 ± 0.8 MA (million years ago, sometimes mya or m.y.a [Multiples of an "annum"] ) as formally accepted by the International Union of Geological Sciences. The "Cenomanian stage" is the sequence of rock strata and its fossil record which have been studied by many disciplines and are used in geochronology to date findings within the geologic age. Excepting chronozones, which are outside the hierarchy organization, stages are the smallest unit and type of chronostratigraphic layers used in the earth sciences for dating comparisons and determination.

Characteristics in the Cenomanian

The late Cenomanian represents the highest mean sea-level observed in the past six hundred million years (approximately one hundred and fifty meters above present day sea-levels). A corollary is that the highlands were at all time lows, so the landscape on earth was one of warm broad shallow seas inundating low lying land areas on the precursors to todays continents and what few lands rose above the waves were made of old mountains and hills, upland plateaus, all much weathered. Tectonic mountain building was minimal, for today's configuration of continents was far from complete, so most continents were isolated by large stretches of water. Without highlands to brake winds, the climate would have been windy and waves large, adding to the weathering and depositions of strata in water regions at fast rate.

Invertebrate Fauna

Belemnites

auropoda

Theropoda

Geologic Formations

Related other topics

*Body form
*European Mammal Neogene
*Geologic time scale
**New Zealand geologic time scale
*North American Land Mammal Age
*Fauna (animals)
*Type locality
*List of GSSAs
*List of GSSPs

Notes and references

External links

* [http://www.stratigraphy.org/over.htm The Global Boundary Stratotype Section and Point (GSSP)] : overview

* [http://www.stratigraphy.org/gssp.htm Chart of The Global Boundary Stratotype Sections and Points (GSSP)] : chart

* [http://www.rocksandminerals.com/geotime/geotime.htm Geotime chart] displaying geologic time periods compared to the fossil record.

References

*Cite journal
last = Gehling
first = James
last2 = Jensen
first2 = Sören
last3 = Droser
first3 = Mary
last4 = Myrow
first4 = Paul
last5 = Narbonne
first5 = Guy
title = Burrowing below the basal Cambrian GSSP, Fortune Head, Newfoundland
journal = Geological Magazine
volume = 138
issue = 2
pages = 213–218
date = March 2001
year = 2001
url = http://www.journals.cambridge.org/action/displayAbstract?fromPage=online&aid=74669
doi = 10.1017/S001675680100509X
id = 1

* Hedberg, H.D., (editor), "International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure", New York, John Wiley and Sons, 1976
* [http://www.stratigraphy.org/cheu.pdf International Stratigraphic Chart] from the International Commission on Stratigraphy
* [http://www2.nature.nps.gov/geology/usgsnps/gtime/gtime1.html USA National Park Service]
* [http://astro.wsu.edu/worthey/earth/html/md08.html Washington State University]
* [http://www.ucmp.berkeley.edu/help/timeform.html Web Geological Time Machine]
* [http://www.pballew.net/arithm16.html#aeon Eon or Aeon] , [http://www.pballew.net/etyindex.html Math Words - An alphabetical index]
* [http://www.stratigraphy.org/geowhen/stages/Cenomanian.html GeoWhen Database - Cenomanian]


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