Morphology of a Newly Mapped Submarine Bank in the Northern Galapagos and Effects on Local Primary Productivity
Abstract
During the 2010 R/V Melville MV1007 cruise, a large submarine bank was discovered and mapped, immediately southwest of Isla Marchena, at the northern margin of the Galapagos Platform. The seamount was surveyed using EM122 multibeam bathymetry and MR1 sidescan sonar. It is elongate with a northeast-southwest orientation and extends 38km and is 18km wide. The calculated volume of the edifice is approximately 200 km3. The orientation and elongate shape of the seamount is similar to other structures in the northern Galapagos, suggesting that it may have originated by the coalescing of two or more eruptive centers originating from NW-SE fissures. The seamount has a relatively flat top with a very steep (23-28 degrees) southwestern slope and a shallower (∼6 degrees) northeastern slope. The origins of the steep southwestern flank are unclear but could be attributed to mass wasting, possibly coupled with post-constructional faulting. The gentler northeastern slope is comparable to the morphology of seamounts in the surrounding area. Sidescan sonar images show areas of high reflectivity on the eastern and northern margin where there are local bathymetric highs. A low relief swath on the western portion shows low reflectivity. The tow cam images show flow margins with varying degrees of sediment cover. Dredging at three sites on the southeastern edge of the seamount recovered basaltic lava with compositions similar to Isla Marchena. One dredge taken from a local high on the southeast part of the bank (530-430 m) recovered eight rock fragments that are rounded and fluted, possibly indicating shoreline erosion. The weathered rocks and the broad flat top of the seamount suggest that at least part of the bank is a submerged island, but this will need to be studied further. The size and extent of the bank makes it important in terms of subsurface current movement and nutrient upwelling. In order to assess this, a study of the sea surface chlorophyll and nutrient levels using MODIS satellite data will be presented.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.V41A2258T
- Keywords:
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- 3045 MARINE GEOLOGY AND GEOPHYSICS / Seafloor morphology;
- geology;
- and geophysics