402 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
8. Green mnd and sand. — In their composition, origin, and distribution these deposits resemble in 
many respects the bine and red mads. I'heir chief characteristic is the presence of a greater or less 
abundance of glauconitic grains and glauconitic casts of the calcareous organisms. These muds and 
sands are almost always developed along bold and exposed coasts, where no very large rivers pour 
their detrital matters into the sea. They contain, as a rule, many remains of calcareous organisms, 
mineral particles from the continental rocks, and a considerable quantity of clayey matter, although 
fine clayey or detrital matter appears always to be less abundant than in a characteristic blue mud. 
Along coasts where these deposits are laid down pelagic conditions appear to approach much nearer 
to the shores than where bine muds prevail, as, for instance, on the Agulhas Bank and off the Atlantic 
coast of the southern United States ; to such an extent is this the case that, were it not for the presence 
of glauconite and the nature of the mineral particles, many of the green muds might equally well be 
-called globigcrina oozes. 
The green sands differ from the green muds chiefly in being more granular in appearance, owing 
to the relatively small quantity of amorphous matter present, and are irsually found in shallower 
water. The average depth of the Challenger samples of green mud is 513 fathoms, and of green sand 
119 fathoms, the range of both classes being usually from 100 to 900 fathoms. The percentage of car- 
bonate of lime varies to a great extent, the average being 25 in the muds and 50 in the sands, pelagic 
and bottom-living foraniiuifera being the principal constituents. The percentage of siliceous organ- 
isms ]iiay be as high as 50, usually higher in the muds than in the sands, and they are principally 
glauconitic casts of calcareous organisms along with diatoms, radiolarians, sponge siiicules, and 
arenaceous foramiuifera. The mineral i)articles usually make up a large part of the deposit, sometimes 
nearly 80 per cent, the grains of glancouite being the most characteristic, along with qu.artz, felspar, 
magnetite, hornblende, augite, etc., and fragments of continental rocks. In the green sands there are 
frequently nodules and small concretions of phosphate of lime. 
Average composiiion of llie Challenger samples of green mud and green sand. 
Green iniul. 
Green sand. 
Carbonate of lime: 
Pelagic foramiuifera 
14.59 
21 
J3ottuin living' foramiuifera 
2.94 
15 
( )ther organisms 
7. 99 
13. 78 
9.f> .<>9 
IQ 7S 
Siliceous organisms 
IH. 07 
8 
27 11 
30 
Fine washings 
33. 70 
12. 22 
74. 48 
50. 22 
100 
100 
9. Volcanic mud and sand. — Around oceanic islands of volcanic origin the deposits consist in a 
large measure of the rocks and minerals arising from the disintegration of the volcanic rocks of the 
islands. Near shore, Avithin the region of wave action, these are largely sands composed of volcanic 
material and the fragments of calcareoiis organisms which vary much in size. In deeper water, further 
from the islands, the mineral particles become less abundant and smaller, n hile pelagic organisms, 
such as foramiuifera, and pteropod shells, coccoliths, and rhabdoliths, increase in number so that the 
de))osit assumes the character of a mud in which there is a considerable (juantity of clayey and 
calcareous matter, light gray, brown, or black in color, and of an earthy rather than a clayey character. 
These deposits may be found along any coast where volcanic rocks prevail, but they are character- 
istically developed around the volcanic islands of the great ocean basins. In general ajipearance and 
conqiosition they present great variety, depending on position, depth, and the organic remains that take 
part in their formation, their chief characteristic being the relative abundance of volcanic materials. 
The Challenger samples of volcanic mud range in depth from 260 to 2,800 fathoms, the average 
depth being 1,033 fathoms; the samples of volcanic sand range from 100 to 420 fathoms, the average 
depth being 243 fathoms. The amount of carbonate of lime varies greatly, sometimes rising to 70 
per cent, principally due to the remains of pelagic and liottom-living foramiuifera. Siliceous 
organisms are rare, always under 5 per cent, consisting of radiolaria, sponge spicules, diatoms, and 
arenaceous foramiuifera ; true glauconitic casts and grains are absent. The mineral particles make 
up a considerable portion of the deposit, sometimes rising to 80 per cent; the most characteristic are 
sanidine, plagioclases, augite, hornblende, rhombic pyroxenes, olivine, and magnetite. Among the 
lapilli the most frei[uont are those belonging to the basaltic and andesitic series of rocks, especially 
those belonging to the vitreous varieties, and they are often decomposed into palagouitic matter, 
