Romanche Trench
The Romanche Trench, also called the Romanche Furrow or Romanche Gap, is the third deepest of the major
It was named after the French navy ship La Romanche, commanded by captain Louis-Ferdinand Martial which on 11 October 1883 made soundings that revealed the trench. The boat was returning to France after spending a few months on a scientific mission near Cape Horn as part of the first International Polar Year.[2]
Oceanography
The trench has a depth of 7,761 m (25,463 ft), is 300 km (190 mi) long and has an average width of 19 km (12 mi) and allows for a major circulation of deep ocean basin water from the west Atlantic to the east Atlantic basins. Deep water flow through the trench is from west to east with a rate of 3.6 Sverdrups (million m³/s) of 1.57 °C (34.83 °F) water.[1]
Lower North Atlantic Deep Water (LNADW) is found around 3,600–4,000 metres (11,800–13,100 ft) below sea level and flows from the Greenland and Norwegian seas; it brings high salinity, oxygen, and freon concentrations towards the equator.
Geology
The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900 km (560 mi), making it the largest equatorial fracture zone in the Atlantic. According to the normal scenario for the opening of the South Atlantic, it is spreading at a rate of 1.75 cm/year (0.69 in/year) and began forming about 50 Ma. North of and parallel to the fracture zone is a transverse ridge which is particularly prominent over hundreds of kilometres east and west of the MAB of the South Atlantic. The western part of the transverse ridge consists of fragments of uplifted oceanic crust and
Biological role
The hydrothermal vents of the MAR support many life forms. The Romanche and Chain Fracture Zones creates a huge gap in the MAR and can act as a "Subsea Berlin Wall" segregating the North Atlantic communities from those in other oceans.[6] Swarms of hydrothermal shrimps reminiscent of those found from northern MAR vent-sites have been found on the northern part of the southern MAR. Bivalve communities have been reported around vents further south. These species await a formal description and it is not known whether or not they represent communities distinct from those on the northern MAR.[7] The flow of NADW through the Romanche and Chain Fracture Zones may serve as a conduit for larval transport from the western North Atlantic to the eastern South Atlantic. For example, the caridean shrimp Alvinocaris muricola inhabits cold seeps in both the Gulf of Mexico and the Gulf of Guinea, which clearly suggests a gene flow across the Atlantic, but the amount of data is very limited and dispersal pathways are not fully understood.[8]
References
Notes
- ^ a b Schlitzer et al. 1985
- ^ Mercier & Speer 1998
- ^ Ferron et al. 1998, Introduction, pp. 1929-1931
- ^ Gasperini et al. 2001, Introduction, pp. 101-102
- ^ Bernoulli et al. 2004, Geological setting and stratigraphy, p. 924
- ^ "Hydrothermal Vent". Census of Marine Life. 2005. Archived from the original on 13 May 2015. Retrieved 14 June 2015.
- ^ German et al. 2008, 3.4. The "Red Lion" vent site, 4°47.82'S, 12°22.59'W; Fig. 9, pp. 340-341
- ^ Ramirez-Llodra & German 2007, pp. 38–39
Sources
- Bernoulli, D.; Gasperini, L.; Bonatti, E.; Stille, P. (2004). "Dolomite formation in pelagic limestone and diatomite, Romanche Fracture Zone, Equatorial Atlantic". Journal of Sedimentary Research. 74 (6): 924–932. . Retrieved 7 June 2015.
- Ferron, B.; Mercier, H.; Speer, K.; Gargett, A.; Polzin, K. (1998). "Mixing in the Romanche Fracture Zone". Journal of Physical Oceanography. 28 (10): 1929–1945. .
- Gasperini, L.; Bernoulli, D.; Bonatti, E.; Borsetti, A. M.; Ligi, M.; Negri, A.; Sartori, R.; von Salis, K. (2001). "Lower Cretaceous to Eocene sedimentary transverse ridge at the Romanche Fracture Zone and the opening of the equatorial Atlantic". Marine Geology. 176 (1–4): 101–119. . Retrieved 7 June 2015.
- German, C. R.; Bennett, S. A.; Connelly, D. P.; Evans, A. J.; Murton, B. J.; Parson, L. M.; Prien, R. D.; Ramirez-Llodra, E.; Jakuba, M.; Shank, T. M.; Yoerger, D. R.; Baker, E. T.; Walker, S. L.; Nakamura, K. (2008). "Hydrothermal activity on the southern Mid-Atlantic Ridge: Tectonically- and volcanically-controlled venting at 4–5°S". Earth and Planetary Science Letters. 273 (3–4): 332–344. . Retrieved 14 June 2015.
- Mercier, H.; Speer, K.G. (1998). "Transport of Bottom Water in the Romanche Fracture Zone and the Chain Fracture Zone". Journal of Physical Oceanography. 28 (5): 779–790. .
- Ramirez-Llodra, E.; German, C. R. (2007). "Biodiversity and biogeography of hydrothermal vent species: thirty years of discovery and investigations" (PDF). Oceanography. 20 (1): 30–41. . Retrieved 14 June 2015.
- Schlitzer, R.; Roether, W.; Weidmann, U.; Kalt, P.; Loosli, H. H. (1985). "A meridional 14C and 39Ar section in northeast Atlantic deep water". Journal of Geophysical Research. 90 (C10): 6945–6952. .