Heckel, Philip H. Department of Geoscience, University of Iowa, Iowa City, Iowa.
Last reviewed:January 2020
- Related Primary Literature
- Additional Reading
A vertical sequence of several different kinds of distinctive sedimentary rock units that is repeated upward through the stratigraphic succession. Originally defined in the rock succession of Pennsylvanian age in the Illinois Basin in the 1930s, the rock types include coal, limestone, sandstone, and several types of shale and mudstone. Cyclothems were soon recognized elsewhere in rocks of this age in the central and eastern United States. Those in the Midcontinent (Kansas and states to the northeast) are dominated by several types of limestone and shale, with less coal and sandstone. Those in the Appalachian region are dominated by coal, mudstone, shale, and sandstone, with less limestone. Some workers generalized the term, and simple cyclothems became recognized in coal-bearing successions of other ages, but the term never achieved wide usage outside of rocks of Pennsylvanian age. See also: Pennsylvanian; Sedimentary rocks; Stratigraphy
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information