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.

The Cenomanian units

As a unit of geologic time measure, the Cenomanian age spans the time between 99.6 ± 0.9 MA and 93.5 ± 0.8 MA (million years ago, sometimes mya or m.y.a) 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 today's 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.

External links

• The Global Boundary Stratotype Section and Point (GSSP): overview
• Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart
• Geotime chart displaying geologic time periods compared to the fossil record.

References

• Hedberg, H.D., (editor), International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure, New York, John Wiley and Sons, 1976
• International Stratigraphic Chart from the International Commission on Stratigraphy
• USA National Park Service
• Washington State University
• Web Geological Time Machine
• Eon or Aeon, Math Words - An alphabetical index
• GeoWhen Database - Cenomanian