. The Earth beneath the sea : History . 10 mm 1 mm rrmi 100m lO^i- ^3 ^ 4 % Fig. 13. Enveloping cumulative curves of grain-size distribution in four environments in the Xorth Mahavavy delta, Madagascar. (From data in Berthois and Guilcher, 1956.) Legend—1: coarse sediments in channels (7 samples); 2: basins (2 samples); 3: coastal mangroves (3 samples); 4: beaches on delta sea-front (6 samples). heavy surf beating upon the outer beach and percolation of sea-water through the coastal dunes at high tide. As a consequence of this, the water in the basins is saline. Since a large proportion
. The Earth beneath the sea : History . 10 mm 1 mm rrmi 100m lO^i- ^3 ^ 4 % Fig. 13. Enveloping cumulative curves of grain-size distribution in four environments in the Xorth Mahavavy delta, Madagascar. (From data in Berthois and Guilcher, 1956.) Legend—1: coarse sediments in channels (7 samples); 2: basins (2 samples); 3: coastal mangroves (3 samples); 4: beaches on delta sea-front (6 samples). heavy surf beating upon the outer beach and percolation of sea-water through the coastal dunes at high tide. As a consequence of this, the water in the basins is saline. Since a large proportion of the basins are dry at the end of the dry season or even before, the salt crystallizes and salt mixed with clay, silt and sand is transported by the wind and deposited in more sheltered areas. Owing to the climatic environment, the inter-levee basins are thus sebkhas, or saline bahadas, and the role of salt in deltaic sedimentation is much more imi)ortant than it would be under a humid climate. Rather similar processes have been reported from the Laguna Madre flats, coastal south Texas, by Fisk (in Russell, 1959), Price (1958) and others.
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectoceanbottom
