Yarmouthian Interglacial (Stage)
Encyclopedia
The Yarmouthian stage and the Yarmouth Interglacial were part of a now obsolete geologic timescale of the early Quaternary
of North America
.
stages. It was developed between 1894 and 1909 by geomorphologists
and Quaternary geologists to subdivide glacial and nonglacial deposits within the United States
. From youngest to oldest, they were the Wisconsin glaciation
, Sangamonian
(interglacial), Illinoian Stage (glacial), Yarmouthian, Kansan glaciation
, Aftonian (interglacial), and Nebraskan stages. The Yarmouthian (Yarmouth) Interglacial was defined first on the basis of "interglacial" sediments encountered in wells
dug in southeasterm Iowa
. Later the Yarmouth (Yarmouthian) stage in Illinois
was defined on the basis of the Yarmouth Paleosol (Soil) developed in the surface of what were thought at that time to be "Kansan" glacial till
s and buried by Illionian glacial tills of the Glasford Formation in southeast Iowa and east-central Illinois. At this time, it was incorrectly presumed that the Yarmouth Paleosol formed during a single interglacial stage that separated a younger glacial stage, the Illinoian Glaciation, represented by the sediments of the Glasford Formation in Illinois and the glacial deposits of an older glacial stage, called the "Kansan Glaciation".
bed on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial - interglacial nomenclature was originally based. Detailed research by various geomorphologists and Quaternary geologists demonstrated that the two glacial tills and one ash bed stratigraphic model, on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial - interglacial nomenclature was based, was completely wrong. For example, the so-called "Kansan" glacial sediments in which the Yarmouth Soil developed are now known to date to different periods of glaciation depending on where it is examined within the Midwest and other parts of North America. In addition, fission track dating
and geochemical analysis demonstrated what was thought to be one volcanic ash
layer was actually three separate volcanic ash layers, i.e. the 602,000 year-old Lava Creek B volcanic ash; the 1,293,000 year-old Mesa Falls volcanic ash, and the 2,003,000 year-old Huckleberry volcanic ash. Thus, the basic assumptions, on which the Yarmouthian (interglacial), Kansan (glacial), Aftonian (interglacial), and Nebraskan (glacial) nonmenclature was originally defined was found to be lacking any scientific basis. As a result, the Yarmouthian (interglacial), Kansan (glacial), Aftonian (interglacial), and Nebraskan (glacial) nonmenclature was abandoned by Quaternary geologists North America and merged into the Pre-Illinoian Stage.
Also, the "interglacial" deposits used by Leverett to originally define the Yarmouthian (Yarmouth) Interglacial in 1898 actually consist of interbedded glacial tills, diamictons, peats, sands, and silts, that are part of the Kellerville Till Member of the Glasford Formation. Pollen samples and wood recovered from these deposits indicate that the vegetation consisted of a Picea-Larix forest and that climate was full-glacial rather than interglacial during their accumulation. Thus, the criteria, i.e. (1.) its sediments being all of the same age, (2.) it consisting of sediments deposited during a single interglacial period, and (3,) as originally defined by Leverett in 1898 consist of interglacial sediments, by which the Yarmouthian (Yarmouth) Interglacial (Stage) was defined and recognized have all been found to be false.
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
of 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...
.
Development
This climatic and chronological framework was composed of four glacial and interglacialInterglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
stages. It was developed between 1894 and 1909 by geomorphologists
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
and Quaternary geologists to subdivide glacial and nonglacial deposits within the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. From youngest to oldest, they were the Wisconsin glaciation
Wisconsin glaciation
The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....
, Sangamonian
Sangamonian Stage
The Sangamonian Stage, also known as the Sangamon interglacial, is the name used by Quaternary geologists to designate the last interglacial period in North America from 125,000—75,000 years ago, a period of...
(interglacial), Illinoian Stage (glacial), Yarmouthian, Kansan glaciation
Kansan glaciation
The Kansan glaciation or Kansan glacial was glacial stage and part of an early conceptual climatic and chronological framework composed of four glacial and interglacial stages.-History:...
, Aftonian (interglacial), and Nebraskan stages. The Yarmouthian (Yarmouth) Interglacial was defined first on the basis of "interglacial" sediments encountered in wells
Water well
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...
dug in southeasterm Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
. Later the Yarmouth (Yarmouthian) stage in Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
was defined on the basis of the Yarmouth Paleosol (Soil) developed in the surface of what were thought at that time to be "Kansan" glacial till
Till
thumb|right|Closeup of glacial till. Note that the larger grains in the till are completely surrounded by the matrix of finer material , and this characteristic, known as matrix support, is diagnostic of till....
s and buried by Illionian glacial tills of the Glasford Formation in southeast Iowa and east-central Illinois. At this time, it was incorrectly presumed that the Yarmouth Paleosol formed during a single interglacial stage that separated a younger glacial stage, the Illinoian Glaciation, represented by the sediments of the Glasford Formation in Illinois and the glacial deposits of an older glacial stage, called the "Kansan Glaciation".
Conflicts
Since the Yarmouthian (Yarmouth) interglacial was named, the stratigraphy of Pleistocene deposits was found to be far more complex then the two glacial tills and one volcanic ashVolcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
bed on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial - interglacial nomenclature was originally based. Detailed research by various geomorphologists and Quaternary geologists demonstrated that the two glacial tills and one ash bed stratigraphic model, on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial - interglacial nomenclature was based, was completely wrong. For example, the so-called "Kansan" glacial sediments in which the Yarmouth Soil developed are now known to date to different periods of glaciation depending on where it is examined within the Midwest and other parts of North America. In addition, fission track dating
Fission track dating
Fission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium-bearing minerals and glasses...
and geochemical analysis demonstrated what was thought to be one volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
layer was actually three separate volcanic ash layers, i.e. the 602,000 year-old Lava Creek B volcanic ash; the 1,293,000 year-old Mesa Falls volcanic ash, and the 2,003,000 year-old Huckleberry volcanic ash. Thus, the basic assumptions, on which the Yarmouthian (interglacial), Kansan (glacial), Aftonian (interglacial), and Nebraskan (glacial) nonmenclature was originally defined was found to be lacking any scientific basis. As a result, the Yarmouthian (interglacial), Kansan (glacial), Aftonian (interglacial), and Nebraskan (glacial) nonmenclature was abandoned by Quaternary geologists North America and merged into the Pre-Illinoian Stage.
Reassessment
Because of the flaws with the early conceptual climatic and chronological framework for Midwestern glacial - interglaciations, the Yarmouthian (Yarmouth) Interglacial (Stage) completely lacks any meaning or usefulness in North American glacial - interglacial nomenclature. First, the incorrect presumption that there was only one major ash bed within the Midwestern United States lead to the misclassification of Middle to Early Pleistocene interglacial deposits containing the 602,000 year-old Lava Creek B volcanic ash; the 1,293,000 year-old Mesa Falls volcanic ash, and the 2,003,000 year-old Huckleberry volcanic ash as being the same age. Because it was thought that there was only one significant ash bed, not three of them, any nonglacial deposit containing an ash bed, regardless of its true age, were thought to be the same age. As a result, the nonglacial desposits attributed in the scientific literature as dating to the Yarmouthian (Yarmouth) Interglacial (Stage) consist of an assemblage of sediments deposited during a number of differing interglacial periods, including some dating to 0.60, 1.22, and 2.02 million years ago. An additional problem is that recent research demonstrates that the glacial tills, the Glasford Formation, of the Illinoian Stage are limited in age to Marine Isotope Stage 6. Thus, within Illinois and adjacent parts of Iowa, the Yarmouth Soil (paleosol), which defines the Yarmouthian (Yarmouth) Interglacial (Stage) in Illinois, spans a period of geologic time equivalent to Marine Isotope stages 7, 8, 9, 10, and 11. Elsewhere in North America, as in Illinois, the Yarmouth Soil also has developed over a variable number of multiple glacial - interglacial cycles. Thus, the presumption that the Yarmouth Soil, by which the Yarmouthian (Yarmouth) Interglacial was later defined, represents a single interglacial stage or period has been completely discredited.Also, the "interglacial" deposits used by Leverett to originally define the Yarmouthian (Yarmouth) Interglacial in 1898 actually consist of interbedded glacial tills, diamictons, peats, sands, and silts, that are part of the Kellerville Till Member of the Glasford Formation. Pollen samples and wood recovered from these deposits indicate that the vegetation consisted of a Picea-Larix forest and that climate was full-glacial rather than interglacial during their accumulation. Thus, the criteria, i.e. (1.) its sediments being all of the same age, (2.) it consisting of sediments deposited during a single interglacial period, and (3,) as originally defined by Leverett in 1898 consist of interglacial sediments, by which the Yarmouthian (Yarmouth) Interglacial (Stage) was defined and recognized have all been found to be false.
External links
- Aber, J.S., 2006, Regional Glaciation of Kansas and Nebraska. Emporia State University, Emporia, Kansas.
- anonymous, 1997, Glacial Map of North-Central United States. Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas.
- anonymous, 2000, Pre-Wisconsin Glaciation of Central North America. Work Group on Geospatial Analysis of Glaciated Environments (GAGE), INQUA Commission on Glaciation, Emporia State University, Emporia, Kansas.
- anonymous, 2007, Global correlation tables for the Quaternary. Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England
- Gibbard, P.L., S. Boreham, K.M. Cohen and A. Moscariello, 2007, Global chronostratigraphical correlation table for the last 2.7 million years v. 2007b., jpg version 844 KB. Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England
- Hallberg, G.R., ed., 1980a, Pleistocene stratigraphy in east-central Iowa., PDF version 15.6 MB. Technical information Series. no. 10. Iowa Geological Survey Bureau, Ames, IA.
- Hallberg, G. R., T. E. Fenton, T. J. Kemmis, and G. A. Miller, 1980, Yarmouth Revisited: Midwest Friends of the Pleistocene 27th Field Conference., PDF version 4.6 MB. Guidebook no. 3. Iowa Geological Survey Bureau, Ames, IA.
- Roy, M., P.U. Clark, R.W. Barendregt, J.R., Glasmann, and R.J. Enkin, 2004, Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States, PDF version, 1.2 MB. Geological Society of America Bulletin, vol. 116, no. 1-2; pp. 30–41; DOI: 10.1130/B25325.1
See also
- Ice ageIce ageAn ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
- Glacial periodGlacial periodA glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate within an ice age...
- Last glacial period
- Timeline of glaciationTimeline of glaciationThere have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively...
- Illinoian Stage
- Pre-Illinoian Stage
- Kansan glaciationKansan glaciationThe Kansan glaciation or Kansan glacial was glacial stage and part of an early conceptual climatic and chronological framework composed of four glacial and interglacial stages.-History:...