- Mississippi embayment
The Mississippi Embayment is a physiographic feature in the south-central United States, part of the Mississippi Alluvial Plain. It is essentially a northward continuation of the fluvial sediments of the Mississippi River Delta to its confluence with the Ohio River at Cairo, Illinois. The embayment is a topographically low-lying basin that is filled with Cretaceous to recent sediments. The northern end of the embayment appears as an anomalous break in regional geologic structure with Paleozoic sedimentary rocks both to the east in Kentucky and Tennessee and to the west in Missouri and Arkansas. The current sedimentary basin results from the filling of a Cretaceous tectonic basin and existed as a large bay in the Cretaceous through early Tertiary shoreline.
The New Madrid Seismic Zone lies at the northern end of the embayment. It was the site of the large New Madrid Earthquakes of 1811 - 1812. The area is underlain by some anomalous geology. The Reelfoot Rift is an ancient failed continental rift that dates back to the Precambrian break-up of the supercontinent Rodinia. The more recent opening of the Atlantic Ocean and Gulf of Mexico during late Paleozoic to early Mesozoic break-up of Pangea no doubt affected and may have partially re-activated the old rift.
Formation of the embayment: the Van Arsdale-Cox explanation
The Mississippi embayment represents a break in what was once a single, continuous mountain range comprising the modern Appalachian range, which runs roughly on a north-south axis along the Atlantic coast of the United States, and the Ouachita range, which runs on a rough east-west axis west of the Mississippi River. The ancestral Appalachian-Ouachita range was thrust up when the tectonic plate carrying North America came into contact with the plates carrying South America and Africa when all three became joined in the ancient supercontinent Pangaea about 300 million years ago. Explaining the formation of the embayment requires explaining how part of a mountain range became a basin.
As Pangaea began to break up about 95 million years ago, North America passed over a volcanic "hotspot" in the Earth's mantle (specifically, the Bermuda hotspot) that was undergoing a period of intense activity. The upwelling of magma from the hotspot forced the further uplift to a height of perhaps 2–3 km of part of the Appalachian-Ouachita range, forming an arch. The uplifted land quickly eroded and, as North America moved away from the hot spot and as the hotspot's activity declined, the crust beneath the embayment region cooled, contracted and subsided to a depth of 2.6 km, forming a trough that was flooded by the Gulf of Mexico. As sea levels dropped, the Mississippi and other rivers extended their courses into the embayment, which gradually became filled with sediment.
Evidence for the Van Arsdale-Cox explanation is found in the presence of the seismic zones centered on New Madrid, Missouri, and Charleston, South Carolina, each the source of devastating earthquakes in the 19th century, and in diamond-bearing kimberlite pipes in Arkansas, which are products of volcanism.
- Crowley's Ridge
- Mississippi Delta — the subset of the embayment that lies in Mississippi state, noted for its distinct cultural history
- Arkansas Delta
Notes and references
- Imlay, R.W., 1949. Lower Cretaceous and Jurassic formations of southern Arkansas and the oil and gas possibilities. Arkansas Resource and Development Commission, Division of Geology, Information Circular 12, 64.
- Morgan, W.J., 1983. Hotspot tracks and the early rifting of the Atlantic. Tectonophysics 94, 123-139.
Wikimedia Foundation. 2010.
Look at other dictionaries:
Mississippi Alluvial Plain — Mississippi Delta … Wikipedia
Mississippi Delta (disambiguation) — Mississippi Delta, part of the Mississippi embayment … Wikipedia
Mississippi County, Missouri — Location in the state of Missouri … Wikipedia
Mississippi River Delta — False color image of the larger Mississippi River Delta … Wikipedia
Mississippi River — For the river in Canada, see Mississippi River (Ontario). Coordinates: 29°09′04″N 89°15′12″W / 29.15111°N 89.25333°W / … Wikipedia
Mississippi (disambiguation) — Contents 1 Places and landforms 2 Time periods 3 Ships 4 Art … Wikipedia
Geography of the Interior United States — the games at the great lake are held in the winter so none can live they realy dont want otters or bubble gum to live either. so just go die Physiographic regions of the U.S. Interior See:legend For purposes of description, the physical geography … Wikipedia
Coon Creek Formation — The Coon Creek Formation is a geologic formation located in western Tennessee and extreme northeast Mississippi. It is a sedimentary sandy marl deposit, Late Cretaceous (Maastrichtian) in age, about 70 million years old. The formation is known… … Wikipedia
Olympic-Wallowa Lineament — Location of the Olympic Wallowa Lineament. Is the OWL an optical illusion? The Olympic Wallowa lineament (OWL) – first reported by cartographer Erwin Raisz in 1945  on a relief map of the continental United States – is a physiographic feature… … Wikipedia
Bootheel — This article is about the southeastern corner of the U.S. state of Missouri. For New Mexico Bootheel, see New Mexico Bootheel. Location of the bootheel region centered on … Wikipedia