Inland sea (geology)

An inland sea (also known as an epeiric sea or an epicontinental sea) is a shallow sea that covers central areas of continents during periods of high sea level that result in marine transgressions. In modern times, continents stand high, eustatic sea levels are low, and there are few inland seas, the largest being Hudson Bay. Modern examples might also include the recently (less than 10,000 years ago) reflooded Persian Gulf, and the South China Sea that presently covers the Sunda Shelf.[1]

For other uses, see Inland Sea.

Modern inland seas
This 1827 map of Australia depicts a 'Great River' and a 'Supposed Sea' that both proved nonexistent.

Former epicontinental seas in Earth's history

At various times in the geologic past, inland seas have been greater in extent and more common than at present.

  • During the Oligocene and Early Miocene large swathes of Patagonia were subject to a marine transgression. The transgression might have temporarily linked the Pacific and Atlantic oceans, as inferred from the findings of marine invertebrate fossils of both Atlantic and Pacific affinity in La Cascada Formation.[5][6] Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography.[5][7]
  • A vast inland sea, the Western Interior Seaway, extended from the Gulf of Mexico deep into present-day Canada during the Cretaceous.
  • At the same time, much of the low plains of modern-day northern France and northern Germany were inundated by an inland sea, where the chalk was deposited that gave the Cretaceous Period its name.
  • The Amazon, originally emptying into the Pacific, as South America rifted from Africa, found its exit blocked by the rise of the Andes about 15 million years ago. A great inland sea developed, at times draining north through what is now Venezuela before finding its present eastward outlet into the South Atlantic. Gradually this inland sea became a vast freshwater lake and wetlands where sediment flattened its profiles and the marine inhabitants adapted to life in freshwater. Over 20 species of stingray, most closely related to those found in the Pacific Ocean, can be found today in the freshwaters of the Amazon, which is also home to a freshwater dolphin. In 2005, fossilized remains of a giant crocodilian, estimated to have been 46 ft (14 m) in length, were discovered in the northern rainforest of Amazonian Peru.[8]
  • In Australia, the Eromanga Sea existed during the Cretaceous Period. It covered large swaths of the eastern half of the continent.[upper-alpha 1]

See also
  • Endorheic basin – Closed drainage basin that allows no outflow
  • Marginal sea – A sea partially enclosed by islands, archipelagos, or peninsulas
  • Mediterranean sea (oceanography) – Mostly enclosed sea with limited exchange with outer oceans

Notes
  1. Also in Australia the promise of an inland sea is often said to have been one of the prime motives of inland exploration during the 1820s and 1830s. Although this theory was championed by the explorer Charles Sturt, it enjoyed little support among the other explorers, most of whom were more inclined to believe in the existence of a Great River which discharged into the ocean in the north-west corner of the continent.[9]

References
  1. The Lord Howe Rise that covers much of the sunken "continent" of Zealandia and the largely submerged Mascarene Plateau that includes the Granitic Group islands of the Seychelles could not be considered "inland"
  2. "Baltic Sea Portal". Archived from the original on 2009-09-22.
  3. Šliaupa, Salius; Hoth, Peer (2011). "Geological Evolution and Resources of the Baltic Sea Area from the Precambrian to the Quaternary". In Harff, Jan; Björck, Svante; Hoth, Peter (eds.). The Baltic Sea Basin. Springer. ISBN 978-3-642-17219-9.
  4. Lidmar-Bergström, Karna (1997). "A long-term perspective on glacial erosion". Earth Surface Processes and Landforms. 22 (3): 297–306. Bibcode:1997ESPL...22..297L. doi:10.1002/(SICI)1096-9837(199703)22:3<297::AID-ESP758>3.0.CO;2-R.
  5. Encinas, Alfonso; Pérez, Felipe; Nielsen, Sven; Finger, Kenneth L.; Valencia, Victor; Duhart, Paul (2014). "Geochronologic and paleontologic evidence for a Pacific–Atlantic connection during the late Oligocene–early Miocene in the Patagonian Andes (43–44°S)". Journal of South American Earth Sciences. 55: 1–18. Bibcode:2014JSAES..55....1E. doi:10.1016/j.jsames.2014.06.008. hdl:10533/130517.
  6. Nielsen, S.N. (2005). "Cenozoic Strombidae, Aporrhaidae, and Struthiolariidae (Gastropoda, Stromboidea) from Chile: their significance to biogeography of faunas and climate of the south-east Pacific". Journal of Paleontology. 79: 1120–1130. doi:10.1666/0022-3360(2005)079[1120:csaasg]2.0.co;2.
  7. Guillame, Benjamin; Martinod, Joseph; Husson, Laurent; Roddaz, Martin; Riquelme, Rodrigo (2009). "Neogene uplift of central eastern Patagonia: Dynamic response to active spreading ridge subduction?". Tectonics. 28.
  8. "Peru finds giant crocodile fossil in Amazon". Daily Times. September 12, 2005.
  9. Cathcart, Michael (2009). The Water Dreamers: How Water and Silence Shaped Australia. Melbourne: Text Publishing. chapter 7. ISBN 9781921520648.
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