The Bounty Trough is a major submerged feature, a bathymetric depression, of the oceanography of the southwest Pacific Ocean. It is located off the east coast of New Zealand's South Island. It is named after the Bounty Islands near the Eastern end of the trough. The islands, in turn, are named after HMS Bounty.
The Bounty Trough is located to the South of the Chatham Rise, and North of the Campbell Plateau. It runs East-West for a distance of some 800 kilometres (497 mi) to the deep ocean between the Chatham and Bounty Island groups. The Bounty Trough's western extremity is less than 50 kilometres (31 mi) off the South Island's coast. [1] It covers an area of approximately 100,000 km2 (38,610 sq mi). [2]
Much of The Bounty Trough lies at depths of 2,000–3,000 metres (6,562–9,843 ft), and it marks an indentation in the "coastline" of the largely submerged continent of Zealandia.
A curious feature of the Bounty Trough is that it marks the continuation of several main river features in the South Island – the "Otago Fan Complex". [3] This is a distinct series of channels existing in the base of the trough which is an extension of the Clutha and Waitaki River systems.
Both these rivers, especially the Clutha, are noted for their fast flow. This alone would not account for the existence of the channels, though much of their current contours was probably shaped by sediment during the ice ages. [4]
The channel system is the remnant of a Cretaceous (failed) rift formed via ocean-floor spreading at the time when Zealandia separated from Antarctica [5] between 130 and 85 Mya. The channels provide a major transportation system for sediments from the major rivers in the eastern South Island. At the Eastern end of the rift is the abyssal Bounty Fan.
In July 2012, the NIWA research ship RV Tangaroa mapped the area finding a structure of nine canyons ending in "a large deep apron-shaped sediment deposit in the Bounty Trough". The survey considered development of a biodiversity assessment of the area which would then support "potential environmental effects of any oil drilling, and help establish environmental guidelines specific to the area". [6] The mapping also found "pock marks" some 20 m (66 ft) deep by 200 m (656 ft) in diameter in the margins which may indicate methane seepage. The survey could support petrochemical exploration, though, Roberts et al. [2] found evidence of "an extensive and effective petroleum system" to be "conjectural".
Both the Otago and abyssal fans, and the rift itself developed from the Kaikoura Orogeny and were greatly accelerated after about 2.5 Ma, with the onset of global glacial/interglacial climatic cycles and the development of an icecap along the alpine region of South Island. The glacial periods contributed large amounts of sediment to the trough. [3] Sediment is not being deposited now in the same way as it was during the glacial period. [6]
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
The Clutha River is the second longest river in New Zealand and the longest in the South Island. It flows south-southeast 338 kilometres (210 mi) through Central and South Otago from Lake Wānaka in the Southern Alps to the Pacific Ocean, 75 kilometres (47 mi) south west of Dunedin. It is the highest volume river in New Zealand, and the swiftest, with a catchment of 21,000 square kilometres (8,100 sq mi), discharging a mean flow of 614 cubic metres per second (21,700 cu ft/s). The river is known for its scenery, gold-rush history, and swift turquoise waters. A river conservation group, the Clutha Mata-Au River Parkway Group, is working to establish a regional river parkway, with a trail, along the entire river corridor.
The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some 1,000 kilometres (620 mi) from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productive and important fishing ground, as well as important habitat for whales.
The seabed is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The geology of the Falkland Islands is described in several publications. The Falkland Islands are located on a projection of the Patagonian continental shelf. In ancient geological time this shelf was part of Gondwana, which around 400 million years ago broke from what is now Africa and drifted westwards relative to Africa. Studies of the seabed surrounding the islands indicated the possibility of oil. Intensive exploration began in 1996, although there had been some earlier seismic surveys in the region.
The Lord Howe Rise is a deep sea plateau which extends from south west of New Caledonia to the Challenger Plateau, west of New Zealand in the south west of the Pacific Ocean. To its west is the Tasman Basin and to the east is the New Caledonia Basin. Lord Howe Rise has a total area of about 1,500,000 km2 (580,000 sq mi), and generally lies about 750 to 1,200 metres under water. It is part of Zealandia, a much larger continent that is now mostly submerged, and so is composed of continental crust. Some have included the 3,500 m (11,500 ft) deep New Caledonia Basin as within the rise, given its continental crust origin, and this would give a larger total area of 1,950,000 km2 (750,000 sq mi).
A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Continental rifting forms new ocean basins. Eventually the continental rift forms a mid-ocean ridge and the locus of extension moves away from the continent-ocean boundary. The transition between the continental and oceanic lithosphere that was originally formed by rifting is known as a passive margin.
The Campbell Plateau is a large oceanic plateau south of New Zealand and the Chatham Rise. It originated in the Gondwanan breakup and is part of Zealandia, a largely submerged continent. The above sea level parts of the plateau — the Bounty Islands, Antipodes Islands, Auckland Islands and Campbell Island — form part of the New Zealand Subantarctic Islands which were declared a World Heritage Site in 1998. Large parts of the Campbell Plateau lie less than 1000 m below sea level. It rises to 500 m at the Pukaki Rise and emerges above sea level at the Auckland and Campbell Islands.
The Rockall Trough is a deep-water bathymetric feature to the northwest of Scotland and Ireland, running roughly from southwest to northeast, flanked on the north by the Rockall Plateau and to the south by the Porcupine Seabight. At the northern end, the channel is bounded by the Wyville-Thomson Ridge, named after Charles Wyville Thomson, professor of zoology at the University of Edinburgh and driving force behind the Challenger Expedition. At the southern end, the trough opens into the Porcupine abyssal plain. The Rockall Basin is a large sedimentary basin that lies beneath the trough. Both are named after Rockall, a rocky islet lying 301.4 km west of St Kilda.
The natural history of New Zealand began when the landmass Zealandia broke away from the supercontinent Gondwana in the Cretaceous period. Before this time, Zealandia shared its past with Australia and Antarctica. Since this separation, the New Zealand landscape has evolved in physical isolation, although much of its current biota has more recent connections with species on other landmasses. The exclusively natural history of the country ended in about 1300 AD, when humans first settled, and the country's environmental history began. The period from 1300 AD to today coincides with the extinction of many of New Zealand's unique species that had evolved there.
The following outline is provided as an overview of and introduction to Oceanography.
Zealandia, also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83–79 million years ago. It has been described variously as a submerged continent, continental fragment, and microcontinent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is over a billion years old, about twice as old as geologists previously thought.
Masaaki Kimura is a Japanese geologist and a professor emeritus from the Faculty of Science of the University of the Ryukyus, Okinawa, Japan.
The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. New Zealand is part of Zealandia, a microcontinent nearly half the size of Australia that broke away from the Gondwanan supercontinent about 83 million years ago. New Zealand's early separation from other landmasses and subsequent evolution have created a unique fossil record and modern ecology.
The Exmouth Plateau is an elongate northeast striking extensional passive margin located in the Indian Ocean roughly 3,000 meters offshore from western and northwestern Western Australia.
The Angola Basin is located along the West African South Atlantic Margin which extends from Cameroon to Angola. It is characterized as a passive margin that began spreading in the south and then continued upwards throughout the basin. This basin formed during the initial breakup of the supercontinent Pangaea during the early Cretaceous, creating the Atlantic Ocean and causing the formation of the Angola, Cape, and Argentine basins. It is often separated into two units: the Lower Congo Basin, which lies in the northern region and the Kwanza Basin which is in the southern part of the Angola margin. The Angola Basin is famous for its "Aptian Salt Basins," a thick layer of evaporites that has influenced topography of the basin since its deposition and acts as an important petroleum reservoir.
The Kutai sedimentary basin extends from the central highlands of Borneo, across the eastern coast of the island and into the Makassar Strait. With an area of 60,000 km2, and depths up to 15 km, the Kutai is the largest and deepest Tertiary age basin in Indonesia. Plate tectonic evolution in the Indonesian region of SE Asia has produced a diverse array of basins in the Cenozoic. The Kutai is an extensional basin in a general foreland setting. Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence. Rapid, high volume, sedimentation related to uplift and inversion began in the Early Miocene. The different stages of Kutai basin evolution can be roughly correlated to regional and local tectonic events. It is also likely that regional climate, namely the onset of the equatorial ever wet monsoon in early Miocene, has affected the geologic evolution of Borneo and the Kutai basin through the present day. Basin fill is ongoing in the lower Kutai basin, as the modern Mahakam River delta progrades east across the continental shelf of Borneo.
Bruce Peter Luyendyk is an American geophysicist and oceanographer, currently professor emeritus of marine geophysics at the University of California, Santa Barbara. His work spans marine geology of the major ocean basins, the tectonics of southern California, marine hydrocarbon seeps, and the tectonics and paleoclimate of Antarctica. His research includes tectonic rotations of the California Transverse Ranges, participation in the discovery of deep-sea hydrothermal vents, quantitative studies of marine hydrocarbon seeps, and geologic exploration of the Ford Ranges in Marie Byrd Land, Antarctica.
The Canadian Arctic Rift System is a major North American geological structure extending from the Labrador Sea in the southeast through Davis Strait, Baffin Bay and the Arctic Archipelago in the northwest. It consists of a series of interconnected rifts that formed during the Paleozoic, Mesozoic and Cenozoic eras. Extensional stresses along the entire length of the rift system have resulted in a variety of tectonic features, including grabens, half-grabens, basins and faults.
The Wishbone scarp is a Pacific Ocean floor feature in the oceanic crust, that if it were on land would be similar to a mountain range fault system over 1,000 km (620 mi) long. It commences in the north near the Osbourn Trough although it is likely to be related tectonically to the Manihiki scarp somewhat to its north. To the south it splits into west and east scarps that have been intercepted by the Louisville hotspot with the West Wishbone scarp continuing until it intercepts the Chatham Rise. There is now evidence that the entire scarp has a fracture zone origin resolving previous uncertainty on this issue.