The Chukchi Shelf or Chukchi Sea Shelf is the westernmost part of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and the easternmost part of the continental shelf of

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. In the west it merges with the Russian Siberian Shelf. Within this shelf, the 50-mile Chukchi Corridor acts as a passageway for one of the largest marine mammal migrations in the world. The main geological features of the Chukchi Shelf are the Hope Basin and the Herald Thrust, a basement uplift cored by

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

s. The latter is named after Herald Island. Off the northwestern

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

n coast there is a

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

rift basin, the Hannah Trough. To the north of Alaska the Chukchi Shelf extends to form the Chukchi Plateau which protrudes into the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...

geological zone. The Chukchi Shelf is shared between

and the

according to the June 1990 USSR–USA Maritime Boundary Agreement.

50-Mile Chukchi Corridor

The Chukchi Corridor is a 50-mile wide strip of ocean offshore of Northwest Alaska that acts as a passageway for one of the largest marine mammal migrations in the world.

Geography

Following the Chukchi Sea coast, the Chukchi Corridor stretches from Point Hope, Alaska to Utqiagvik, Alaska. From winter through early summer, the area is covered in sea ice with recurring openings in the ice that allow wildlife to migrate north from the Bering Sea to areas of the Chukchi or Beaufort seas during spring and early summer

Fauna

The Chukchi Sea coastline serves as an essential corridor for marine mammals like

bowhead whale The bowhead whale (''Balaena mysticetus''), sometimes called the Greenland right whale, Arctic whale, and polar whale, is a species of baleen whale belonging to the family Balaenidae and is the only living representative of the genus '' Balaena' ...

s, beluga whales, Pacific walrus, and bearded seals. It is also an important hunting area for indigenous subsistence hunters. This region includes biologically important gray whale feeding and reproduction habitats Many bird species navigate the Chukchi Corridor to migrate to the North Slope for summer breeding As a region with substantial seafloor productivity, the Chukchi Corridor is an important nursery habitat for forage fish species,

Arctic cod ''Arctogadus glacialis'', known also with ambiguous common names Arctic cod and polar cod, is an Arctic species of fish in the cod Family (biology), family Gadidae, related to the true Gadus, cod (genus ''Gadus''). ''Arctogadus glacialis'' is fo ...

, and

Saffron cod The saffron cod ''(Eleginus gracilis)'' is a commercially harvested fish closely related to true cods (genus ''Gadus''). It is dark grey-green to brown, with spots on its sides and pale towards the belly. It may grow to 55 cm and weigh up to ...

. Saffron and Arctic cod are critical to the Arctic marine food web.North Pacific Fishery Management Council
"Fishery Management Plan for Fish Resources of the Arctic Management Area"
North Pacific Fishery Management Council, 2009. Retrieved 16-09-2016.

Importance

The Chukchi Corridor is an extremely important region for subsistence hunting for the communities of Point Hope, Point Lay, Wainright, and Utqiagvik, Alaska. Studies show that Inupiaq rely extensively on areas in the Chukchi Corridor for hunting throughout the year. The National Marine Fisheries Service designated areas along the entire Chukchi coast out to 15–30 miles offshore as Essential Fish Habitat (EFH) for saffron cod. In 2001, the U.S. Fish and Wildlife Service designated Ledyard Bay as critical habitat for spectacled eiders. Currently, part of the corridor is protected from oil and gas activities. On January 27, 2015, President Obama, using his authorities under the Outer Continental Shelf Lands Act, permanently withdrew the waters 3 to 25 miles offshore from future oil and gas leasing activities. This action leaves the valuable waters 25 to 50 miles offshore unprotected.

Geology

The Chukchi Shelf and surrounding regions have a recent history of petroleum production and exploration, with development of the nearby North Slope region dominating petroleum production in Alaska with over 10 billion barrels of oil produced between 1977 and 2005. The stratigraphy and structural geology of the Chukchi Shelf have been studied due to it being a potential source area of sediment that filled the North Slope basin. Studies using seismic reflection data in the Chukchi Shelf have shown that the structural history of the shelf is complex with multiple events of deformation from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

through

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

time. The structural deformation features of the shelf have been reactivated at least four different times, from thin-skinned crustal shortening creating a fold and thrust belt in the Devonian, to reactivation of thrust faults as normal faults during crustal extension in the

to create the Hanna Trough. These normal faults were then again reactivated as thrust faults in the southern shelf in the Jurassic, and reactivated as normal faults again in the early Cenozoic. The process of deformational features being reactivated throughout different stress regimes in time is excellent evidence of structural inheritance, where previously used planes of weakness are used in both shortening and extensional regimes. These examples in the Chukchi Shelf show that structural inheritance can survive multiple deformational events through hundreds of millions of years. These concepts play a role in petroleum exploration since deformational planes of weakness can create or destroy petroleum plays depending on the surrounding stratigraphy.

50-Mile Chukchi Corridor

Geography

Fauna

Importance

Geology

References

Further reading