The structural and sedimentological evolution of the Somali Basin : paleoceanographic interpretations
Burroughs, Richard H.
MetadataShow full item record
KeywordReconstruction; Paleocurrents; Chain (Ship : 1958-) Cruise CH99; Chain (Ship : 1958-) Cruise CH100
The paleooceanographic development of the Somali Basin in the Northwestern Indian Ocean is determined through considering the structural, evolution of the area; its influence on Neogene atmospheric and oceanic circulation as indicated in the sediment record; and variation in these circulation systems as seen in late Quaternary sediments. Chain Ridge forms the main structural element of the Somali Basin. Correlation of geophysical measurements along its topographically elevated portion with geophysical transects in the southern Somali Basin indicates that a buried portion of the Chain Ridge sector of Owen Fracture Zone extends at least to 7.5°S. In areas where crustal age may be estimated on both sides of the fracture zone either by elevation or by other methods, the sea floor to the west is at least 30 m.y. older than that to the east and may be considerably older. The trend of the fracture zone and the age of its segments control the time and direction of movement for India relative to Africa and Madagascar. In addition, they limit the number of proposed reconstructions and indicate that the Western Somali Basin is a small remaining part of the original Tethys. These constraints result in a model for the area which considers Gondwanaland dispersal in the Western Indian Ocean. The final stages of development of the Somali Basin respond with the destruction of the Tethys with the regression in northern India during Middle Miocene. Neogene sedimentation rate determinations for the Somali Basin show considerable increases between the Miocene and Recent, in spite of the fact that the basin is becoming larger and deeper. It is proposed that the dessication and subsequent elevation of the area in northern India caused by structural evolution resulted in the development of a land-sea heating contrast which drives the southwest. monsoon, and due to increased upwelling and productivity it is recorded by increased sedimentation rates in the Somali Basin. The late Quaternary sediment record of the area indicates maintenance of these large scale circulations with little change in sea surface temperature as determined from nannofossil assemblage variation, and occurrence of upwelling over a broader area as indicated by the distribution of coarse carbonate. Several significant bottom water incursions into the basin are interpreted from analyzing the total carbonate curves but their effects do not extend to the area of maximum upwelling due to depression of the CCD by high productivity.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1974
Showing items related by title, author, creator and subject.
The ecology of colonial radiolarians : their colony morphology, trophic interactions and associations, behavior, distribution, and the photosynthesis of their symbionts Swanberg, Neil Ralph (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1979-08)Colonial radiolarians (Spumellaria) are among the most common and abundant large zooplankton, but they have been little studied by modern biologists. Colonies were found on 98% of epipelagic diving stations in the period ...
Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. I, Horizontal and vertical distributions Wiebe, Peter H.; Boyd, Steven H. (Woods Hole Oceanographic Institution, 1979-01)The hydrographic limit of the distribution of Nematoscelis megalops in the Northwestern Atlantic Ocean is usually marked by the abrupt changes in water properties across the Gulf Stream. There are, however, isolated but ...
Nutritional ecology of Agalma okeni and other siphonophores from the epipelagic western North Atlantic Ocean Biggs, Douglas C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1976-05)The feeding and fishing behavior of siphonophores in their natural environment: was observed by SCUBA diving at 171 stations in warm-water areas of the Western North Atlantic Ocean. Calycophorae and Physonectae showed ...