Mississippian (geologic period)
Encyclopedia
- Not to be confused with the "Mississippian period" describing the dominance of the Mississippian cultureMississippian cultureThe Mississippian culture was a mound-building Native American culture that flourished in what is now the Midwestern, Eastern, and Southeastern United States from approximately 800 CE to 1500 CE, varying regionally....
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The Mississippian is a subperiod in the geologic timescale or a subsystem of the geologic record
Geologic record
The geologic record in stratigraphy, paleontology and other natural sciences refers to the entirety of the layers of rock strata — deposits laid down in volcanism or by sediment deposition of weathering detritus including all its fossil content and the information it yields about the history...
. It is the earliest/lowermost of two subperiods of the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
period lasting from roughly 359 to 318 Ma
Year
A year is the orbital period of the Earth moving around the Sun. For an observer on Earth, this corresponds to the period it takes the Sun to complete one course throughout the zodiac along the ecliptic....
(million years ago). As with most other geochronologic
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
units, the rock bed
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
s that define the Mississippian are well identified, but the exact start and end dates are uncertain by a few million years. The Mississippian is so named because rocks with this age are exposed in the Mississippi River valley
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
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In North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, where the interval consists primarily of marine limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
s, it was in the past treated as a full-fledged geologic period between the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
and the Pennsylvanian
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
. In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
system, and sometimes called the Upper Carboniferous and Lower Carboniferous instead. During the Mississippian subperiod an important phase of orogeny
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
occurred in the Appalachian Mountains
Appalachian Mountains
The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...
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Subdivisions
In the official geologic timescale, the Mississippian is subdivided into three stages:- TournaisianTournaisianThe Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from 359.2 ± 2.5 Ma to 345.3 ± 2.1 Ma...
- ViseanViséanThe Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from 345.3 ± 2.1 to 328.3 ± 1.6 Ma...
- SerpukhovianSerpukhovianThe Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from 328.3 Ma tot 318.1 Ma...
The first two come from European stratigraphy, the last is from Russian stratigraphy. Besides Europe and Russia, there are many local subdivisions that are used as alternatives for the international timescale. In the North American system, the Mississippian is subdivided into four stages:
- Kinderhookian (the lower two-thirds of the Tournaisian)
- Osagean (top of the Tournaisian and bottom of the Visean)
- Meramecian (middle Visean)
- Chesterian (top of the Visean plus the Serpukhovian)