DISTRIBUTION OF CALCIUM CARBONATE IN AREA INVESTIGATED BY CARNEGIE 



99 



no. 7083 the indices are a=1.567, =1.586, 7 =1-587. 

 According to Professor W. P. Kelley, the dehydration 

 curves of these two soil colloids indicate that the clay 

 mineral in them is closely related to, but slightly differ- 

 ent from, beidellite. This difference is confirmed both 

 for the soil colloids and for the deep-sea clays by a 

 comparison of the X-ray patterns with those given in 

 table 30 for montmorillonite, beidellite, nontronite, and 

 bentonite. Besides the quartz lines at 3.33, 1.81, and 

 1.37 angstroms, these samples also contain lines at 

 about 3.2, 2.42, and 2.0 angstroms, which are not found 

 in the clay minerals mentioned, and they usually do not 

 contain the characteristic line of beidellite and montmo- 

 rillonite at about 5 angstroms. It is interesting to note 

 in this connection that Dr. C. S. Ross, from the results 

 of optical examination, identified the clay mineral in 

 sample 62 as being similar to the beidellite-nontronite 

 group. 



Correns believes, from the results of an X-ray in- 

 vestigation of the deep-sea samples collected by the 

 Meteor expedition,that certain of these contain musco- 



vite and kaolinite in addition to calcite. Nagelschmidt's 

 results show that the fine fraction of the Mallss clay 

 contains muscovite and halloysite, in addition to 

 quartz and calcite; Denison, Fry, and Gile (1929), and 

 Volk (1933) are of the opinion that soil colloids often 

 contain muscovite. An examination of table 29-B 

 will show that many of the characteristic muscovite 

 and kaolinite ( or halloysite ) lines are present in at 

 least some of the samples, and it is therefore 

 possible that these minerals are present in certain 

 deep-sea clays of the Pacific. The possible presence 

 of phillipsite, the lines of which coincide with many 

 of the diagnostic lines of muscovite and kaolinite, 

 makes the determination of the latter minerals very 

 uncertain. On the other hand, if the colloidal mater- 

 ials in deep-sea clays originate as continental soils, 

 it would be expected that several clay minerals are 

 present in them, and furthermore in different ocean- 

 ic basins the principal clay mineral in the deposits 

 would reflect the dominant conditions of soil forma- 

 tion on surrounding land. 



DISTRIBUTION OF CALCIUM CARBONATE IN THE AREA INVESTIGATED BY THE CARNEGIE 



Observed Relations 



In table 36 are given most of the determinations 

 available of the calcium carbonate contents of bottom 

 samples collected in the region traversed by. the Carne- 

 gie . The results of 596 determinations are given. Of 

 these over one hundred have not been published previous- 

 ly, namely, those of the Carnegie and of the U.S.C. and 

 G.S.S. Surveyor bottom samples. The remainder have 

 been compiled from the results of the Challenger (Mur- 

 ray and Renard, 1891) and the Albatross (Murray and 

 Lee, 1909); the descriptions given by Murray (1902, 

 1906) of certain samples collected by the British sur- 

 veying ships Britannia. Egeria. Penguin, and Waterwitch 

 and the U.S.S. Tuscarora ; and the numerous determina- 

 tions published by Trask (1932) on samples collected by 

 him or obtained from other sources. 



The data are grouped according to latitude and depth 

 for each 10-degree interval of latitude north and south 

 of the equator, and for the following depth intervals: to 

 1000 meters, 1000 to 2000, 2000 to 3000, 3000 to 4000, 

 4000 to 5000, and over 5000 meters. The name of the 

 collecting ship when known, the published reference, the 

 type of deposit, and the location, depth, and calcium car- 

 bonate content, are given for each sample. These data 

 are summarized and illustrated in tables 33 and 34 and 

 figures 38 to 41, which give the average calcium car- 

 bonate contents of all the samples of sediments and of 

 the pelagic sediments alone, for the various depth divi- 

 sions within each latitude interval, and for each depth 

 division of all latitudes taken together. The frequency 

 distribution of calcium carbonate contents within each 

 latitude and depth division is summarized in table 35, 

 wherein the numbers of samples for each division having 

 percentage contents of CaC03 of to 10 per cent, 10 to 

 20 per cent, 20 to 30 per cent, etc. are shown. 



Areal Distribution. Chart 10, constructed from 

 table 36, shows the probable areal distribution of calci- 

 um carbonate in the region investigated by the Carnegie . 

 The actual content of calcium carbonate of each of the 



samples given in table 36 also is shown. The chart was 

 constructed in the following manner. The available de- 

 terminations of calcium carbonate (given in table 36) 

 were plotted first and then the lines of equal calcium 

 carbonate content as given by Murray and Lee were 

 drawn on the chart. In addition, all sonic sounding val- 

 ues of less than 2000 fathoms obtained by the U.S.S. 

 Ramapo (H.O. Publ. 210 a, c) in the north Pacific and 

 certain soundings of the Carnegie were plotted. With 

 the aid of Hanzawa's chart (1928) of the areal distribu- 

 tion of the various types of bottom sediments in the 

 northwest Pacific, and of the small scale Hydrographic 

 Office sheets showing the depths of other soundings in 

 the north and the southeast Pacific, the lines of equal 

 calcium carbonate content given by Murray and Lee were 

 modified to correspond to the data plotted on the chart. 

 Contour lines for 5, 15, 30, 50, and 75 per cent of calci- 

 um carbonate are shown. The areas having more than 

 30 per cent CaC03 are indicated by crosshatching, as 

 described in the legend accompanying the chart. 



Although no information is available about the nature 

 of the sediments surrounding most of the islands in the 

 south and northwest Pacific, the areas around these is- 

 lands, following Murray and Lee, have been assumed to 

 contain sediments having more than 30 per cent CaC03. 

 Also, known depths less than 2000 fathoms in the north 

 Pacihc have been assumed to be underlain by sediments 

 containing more than 15 per cent CaC03. 



In the Pacific north of latitude 10° there is very lit- 

 tle difference in the general character of the chart from 

 that given by Murray and Lee. South of this latitude sev- 

 eral important changes have been made. The areas of 

 more than 30 per cent CaC03 content surrounding the 

 Caroline Islands and the Marshall Islands, between lon- 

 gitudes 140° and 180° east, and latitudes to 12° north, 

 have been joined together as a result of Hanzawa's work 

 in this region. Similarly, the three areas of CaCO^ con- 

 tent over 50 per cent in the southeast Pacific have been 

 grouped into one area and greatly enlarged. Although 

 the investigations of the Carnegie added considerably to 



