Western Interior Seaway during the mid-Cretaceous, about 100 million years before the present

The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves during most of the early and mid-Cretaceous Period. Image File history File links File links The following pages link to this file: Western Interior Seaway Geology of the Grand Teton area Ammolite ... Image File history File links File links The following pages link to this file: Western Interior Seaway Geology of the Grand Teton area Ammolite ... This article is about the body of water. ... Animated, colour-coded map showing the various continents. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... // The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. ...

Origin and Geology

The Seaway was created as the Pacific and North American tectonic plates collided, causing the Rocky Mountains to form in western North America. With high eustatic sea levels existing worldwide during the Cretaceous, waters from the Arctic Ocean in the north and the Gulf of Mexico in the south met and flooded the central lowlands, forming a sea that transgressed (grew) and regressed (receded) over the course of the Cretaceous.  The Pacific plate, shown in pale yellow The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean. ...  The North American plate, shown in brown The North American Plate is a tectonic plate covering most of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... For individual mountains named Rocky Mountain, see Rocky Mountain (disambiguation). ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... Eustasy is one of several terms that are used to describe the changing relationships between sea level and dry land. ... Gulf of Mexico in 3D perspective. ...

The earliest phase of the Seaway began in the mid-Cretaceous, when an arm of the Arctic Ocean transgressed south over western North America; this formed the Mowry Sea, so named for a characteristic rock formation that is rich in oil shale.^[1] In the south, the Gulf of Mexico was an extension of the Tethys Sea, which met with the Mowry Sea in the late Cretaceous, forming the "complete" Seaway.^[1] A geologic formation is a formally named rock stratum or geological unit. ... Oil shale Oil shale is a general term applied to a fine-grained sedimentary rock containing significant traces of kerogen (a solid mixture of organic chemical compounds) that have not been buried for sufficient time to produce conventional fossil fuels. ... The Tethys Sea was a shallow inland body of water that existed between Laurasia and Gondwana, the geological ancestor of the modern Black, Caspian and Aral Seas. ...

At its largest, the Western Interior Seaway stretched from the Rockies to the Appalachians in the east, some 1000 km wide. At its deepest, it may have been only 800 or 900 meters deep, shallow in terms of seas. Two great continental watersheds drained into it from east and west, diluting its waters and bringing resources in eroded silt that formed shifting delta systems along its low-lying coasts. There was little sedimentation on the eastern shores of the Seaway; the western boundary however, consists of a thick clastic wedge eroded eastward from the Sevier orogenic belt.^[1][2] The western shore was thus highly variable, depending on variations in sea level and sediment supply.^[1] The Appalachian Mountains are a system of North American mountains running from Newfoundland and Labrador, Canada to Alabama in the United States, although the northernmost mainland portion ends at the Gaspe Peninsula of Quebec. ... Silt is soil or rock derived granular material of a specific grain size. ... This article or section cites very few or no references or sources. ... In geology, clastic wedge usually refers to a thick assemblage of sediments--often lens-shaped in profile--eroded and deposited landward of a mountain chain; they begin at the mountain front, thicken considerably landwards of it to a peak depth, and progressively thin with increasing distance inland. ... The Sevier orogeny was a mountain-building event that affected western North America between aproximately 140 million years ago (Ma), and 50 Ma. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...

Widespread carbonate deposition suggests that the Seaway was warm and tropical, with abundant calcareous algae.^[3] Rudy Slingerland of Penn State University has computer-modelled a counter-clockwise gyre for the Cretaceous Seaway, with cooler waters flowing south along the eastern seacoasts of Wyoming and Colorado. In organic chemistry, a carbonate is a salt of carbonic acid. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ...

At the end of the Cretaceous continuing uplift in a mountain-building episode called the Laramide orogeny hoisted the sandbanks (sandstone) and muddy brackish lagoons (shale), the thick sequences of silt and sandstone still seen today as the Laramie Formation, while low-lying basins between them gradually subsided. The Western Interior Seaway divided across the Dakotas and retreated south towards the Gulf of Mexico. This shrunken, regressive phase of the Western Interior Seaway is sometimes called the Pierre Seaway. The Laramide orogeny was a period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. ... Clarence King named the Laramie Formation in 1876 for exposures in northeastern Colorado. ... Gulf of Mexico in 3D perspective. ...

During the early Paleocene, parts of the Western Interior Seaway (marine waters) still occupied areas of the Mississippi Embayment, submerging the site of present-day Memphis. Later transgression however, was associated with the Cenozoic Tejas sequence, rather than with the previous event responsible for the Seaway. The Paleocene, early dawn of the recent, is a geologic epoch that lasted from 65. ... This article may be too technical for most readers to understand. ... City nickname: The River City or The Bluff City Location in the state of Tennessee County Shelby County, Tennessee Area  - Total  - Water 763. ... The Tejas sequence was the last major marine transgression across the North American craton. ...

Fauna

An anachronistic drawing of a plesiosaur and mosasaur.

The Western Interior Seaway was a shallow sea, filled with abundant marine life. Interior Seaway denizens included predatory marine reptiles, the largest animals in the Cretaceous seas: mosasaurs growing up to 18 meters long, ichthyosaurs (one specimen from Pink Mountain in British Columbia is currently the largest ichthyosaur specimen found to date^{[citation needed]}), and plesiosaurs (an inspiration for the Loch Ness Monster). Other marine life included sharks, such as Squalicorax, and advanced bony fish including Pachyrhizodus, Enchodus, and the massive 5-meter long Xiphactinus, a fish larger than any modern bony fish. Other sea life included invertebrates such as mollusks, ammonites, squid-like belemnites, and plankton including coccolithophores that secreted the chalky platelets that give the Cretaceous its name, foraminiferans and radiolarians. from www. ... from www. ... Look up Anachronism in Wiktionary, the free dictionary. ... Reptilia redirects here. ... Subfamilies Mosasaurinae Plioplatecarpinae Tylosaurinae Mosasaurs (from Latin Mosa, the Meuse river where the fossils were first discovered + Greek sauros, lizard) were serpentine marine reptiles, more closely related to snakes than to monitor lizards (Lee 1997). ... Families Ichthyosauridae Leptonectidae Mixosauridae Ophthalmosauridae Shastasauridae Stenopterygiidae Teretocnemidae Ichthyosaurs (Greek for fish lizard - ιχθυς meaning fish and σαυρος meaning lizard) were giant marine reptiles that resembled fish and dolphins. ... Pink Mountain is an unincorporated community in British Columbia, Canada. ... Motto: Splendor Sine Occasu (Latin: Splendour Without Sunset (diminishment)) Capital Victoria Largest city Vancouver Official languages English Government - Lieutenant-Governor Iona Campagnolo - Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament - House seats 36 - Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th - Total 944,735... Families Plesiosaurs (IPA ) (Greek: plesios, near to + sauros, lizard) were large, carnivorous aquatic reptiles. ... For other uses, see Loch Ness Monster (disambiguation). ... For other uses, see Shark (disambiguation). ... Species See text Squalicorax (crow shark) is a genus of extinct lamniform shark known to have lived during the Cretaceous period. ... Enchodus is a genus of extinct fish. ... Binomial name Xiphactinus audax Leidy, 1870 Xiphactinus audax (from Latin and Greek for sword-ray daring) was a large predatory bony fish that lived in the Cretaceous period. ... Invertebrate is an English word that describes any animal without a spinal column. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... For the extinct mollusc see Ammonite. ... Extinct Orders Aulacocerida Phragmoteuthida Belemnitida Diplobelida Belemnoteuthina Belemnites (or belemnoids) are an extinct group of marine cephalopod, very similar in many ways to the modern squid and closely related to the modern cuttlefish. ... Photomontage of plankton organisms Plankton are any drifting organism that inhabits the water column of oceans, seas, and bodies of fresh water. ... Coccolithophores are single-celled algae belonging to the haptophytes. ... Orders Allogromiida Carterinida Fusulinida - extinct Globigerinida Involutinida - extinct Lagenida Miliolida Robertinida Rotaliida Silicoloculinida Spirillinida Textulariida incertae sedis    Xenophyophorea    Reticulomyxa The Foraminifera, or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands that branch and merge to form a dynamic net. ... Classes Polycystinea Acantharea Sticholonchea Radiolarians (also radiolaria) are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. ...

The Western Interior Seaway was also home to early birds, including the flightless Hesperornis, which had stout legs for swimming through the water and small wing-like appendages used for marine steering rather than flight; and the tern-like Ichthyornis, an early avian with a toothy beak. For other meanings of bird, see bird (disambiguation). ... Families Hesperornithidae Hesperornithiformes are an extinct and highly specialized order of Cretaceous toothed birds. ... Genera Sterna (Gelochelidon) (Hydroprogne) (Thalasseus) Chlidonias Phaetusa Anous Procelsterna Gygis Larosterna Terns are seabirds in the family Sternidae, previously considered a subfamily Sterninae of the gull family Laridae. ... This article does not cite its references or sources. ...

On the bottom the giant clam Inoceramus has left common fossilized shells in the Pierre Shale. The clam had a thick shell paved with "prisms" of calcite deposited perpendicular to the surface, which gave it a pearly luster in life. Paleontologists suggest that the giant size was an adaptation for life in the murky bottom waters, where a correspondingly large gill area would have allowed the animal to cope with oxygen-depleted waters. The genus Inoceramus (James Sowerby, 1814) were bivalves in the Pteriacea superfamily. ...

Note that the above figure actually depicts an encounter between a mosasaur (not a pliosaur) and a plesiosaur, an event supported in at least one case by the fossil record.[1] The pliosaur's head is depicted above water, however, which was not considered physiologically possible. [2] Pliosaurs did exist in the Western Interior Seaway, but went extint during the Cenomanian period.

See also

• Geology of the Bryce Canyon area
• Zuñi sequence
• Sundance Sea - a separate seaway of the Jurassic

The exposed geology of the Bryce Canyon area shows a record of deposition that covers the last part of the Cretaceous period and the first half of the Cenozoic era in that part of North America. ... The Zuñi sequence was a cratonic sequence that began in the latest Jurassic, peaked in the late Cretaceous, and ended by the start of the following Paleocene. ... The Sundance Sea was a shallow inland sea which existed in North America during the Jurassic Period of the Mesozoic Era. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ...

References

1. ^ ^{a b c d} Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0-7167-2882-6 pp. 487-9
2. ^ Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997. ISBN 0-314-09577-2 p. 610
3. ^ Oceans of Kansas Paleontology. Mike Everhart. Retrieved on 2007-02-06.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 37th day of the year in the Gregorian calendar. ...

External links

• Oceans of Kansas
• Marine Reptiles of South Dakota
• Paleo Map Project
• Cretaceous paleogeography, southwestern US