Table of Contents
- 1 What was responsible for the sea level oscillations that drove the formation of cyclothems?
- 2 What do cyclothems represent?
- 3 What happens during transgression?
- 4 What is the significance of the Carboniferous period?
- 5 What are cratonic sequences?
- 6 What is a seam of coal?
- 7 Where does the word cyclothem come from in Greek?
- 8 Where are cyclothems found in the United States?
What was responsible for the sea level oscillations that drove the formation of cyclothems?
Some cyclothems might have formed as a result of marine regressions and transgressions related to growth and decay of ice sheets, respectively, as the Carboniferous was a time of widespread glaciation in the southern hemisphere. A more general interpretation of sequences invokes Milankovitch cycles.
What do cyclothems represent?
Cyclothems. A cyclothem is a series of repeating sediments representing the transgression and regression of H2O or the submergence and emergence of land. In coal-bearing strata, changes in depositional environment produced a cyclic repetition of beds.
What term is given to describe a repetitive stratigraphic succession of marine and nonmarine strata that are indicative of cyclical depositional regimes?
cyclothem, complex, repetitive stratigraphic succession of marine and nonmarine strata that are indicative of cyclic depositional regimes.
How are Cyclothems formed?
Cyclothems are cyclic stratigraphic sequences that are unique to the Pennsylvanian and earliest Permian periods within the US Midcontinent, that formed as a result of marine transgressions and regressions (rise and fall of sea level) related to the waning and waxing of ice sheets at the South Pole.
What happens during transgression?
Transgression occurs when the ocean basins have more quantity of water than their capacity. A Marine Transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding.
What is the significance of the Carboniferous period?
Over millions of years, the organic deposits of this plant debris formed the world’s first extensive coal deposits—coal that humans are still burning today. The growth of these forests removed huge amounts of carbon dioxide from the atmosphere, leading to a surplus of oxygen.
What ended the Pennsylvanian Period?
The end of the Pennsylvanian Period was marked by a dry climate, the gradual disappearance of the vast coastal coal swamps and changes in plants and animals. These changes were brought about by the assemblage of the super-continent, Pangaea, and retreat of the shallow seas from interior continental areas.
What was Earth like during Pennsylvanian Period?
Swampy Forests By the Pennsylvanian Period, the evolution of terrestrial plants and animals had advanced to the point where true forests were developed in lowland, coastal sites. The presence of extensive, lush, swampy forests characterizes North America during the Pennsylvanian Period.
What are cratonic sequences?
A cratonic sequence is a very large-scale lithostratographic sequence in the rock record that represents a complete cycle of marine transgression and regression on a craton (block of continental crust) over geologic time.
What is a seam of coal?
Definition of coal seam : a bed of coal usually thick enough to be profitably mined.
How are cyclothems formed in the Midcontinent?
Cyclothems are repetitive stratigraphic sequences that are unique to the Pennsylvanian and earliest Permian periods within the US midcontinent. They formed as a result of marine transgressions and regressions as explained in the previous paragraph. The ideal Midcontinent cyclothymic deposit consists of four basic units.
What was the lowest level of the Pennsylvanian cyclothem?
Geological development of Pennsylvanian cyclothems. The lowest (oldest) level of the cyclothem is made up of a sandy shale containing marine fossils and representing nearshore environments. Sedimentary deposition in a shallow, nearshore marine environment.
Where does the word cyclothem come from in Greek?
Cyclothem is derived from two Greek words: Oyclos, cycle, and thema, a deposit. Cyclothems are repetitive stratigraphic sequences that are unique to the Pennsylvanian and earliest Permian periods within the US midcontinent.
Where are cyclothems found in the United States?
In Kansas alone, in just the Middle and Upper Pennsylvanian (Absaroka) section, there are parts or all of about 40 cyclothems. Their formation probably was the result of changes in sea-level as a result of the waxing and waning of southern-hemisphere glaciers.