42 



MARINE BOTTOM SAMPLES OF LAST CRUISE OF CARNEGIE 



from samples 22, 23, 27, and 79, were dissolved in acid 

 and found to contain as nuclei small colorless shards of 

 siliceous volcanic glass (index of refraction less than 

 1.50). Dr. J. D. H. Wiseman^ has shown that most man- 

 ganese nodules contain such finely divided volcanic glass, 

 instead of the clay minerals which were formerly be- 

 lieved to be present in them. 



The observations summarized in the preceding par- 

 agraph merely confirm the long recognized fact that the 

 coarser -grained inorganic constituents of pelagic deep- 

 sea sediments are chiefly of volcanic origin. It is not a 

 necessary deduction, however, that the fine-grained, 

 partly colloidal materials which are the predominant in- 

 organic constituents of these sediments either are vol- 

 canic or have originated mainly from the decomposition 

 on the sea floor of volcanic debris. A priori, at least, it 

 is equally possible that in certain regions the major part 

 of this fine-grained material is of continental origin and 

 has been carried in suspension from land and deposited 

 on the sea bottom simultaneously with coarser-grained 

 volcanic debris from other sources. Any conclusions as 

 to the origin of the fine-grained and colloidal inorganic 

 constituents in the sediments of a given region should be 

 based on a comparison of the properties of these con- 

 stituents themselves with those of similar substances of 

 known origin. 



Twin crystals and aggregates of the interesting zeo- 

 litic mineral phillipsite were observed in the sand 

 grades of nine Globigerina oozes and two red clays from 

 the southeastern Pacific. This mineral is shown by 

 X-ray analysis to be present also in the finer fractions 

 of another Globigerina ooze and probably in several ad- 

 ditional noncalcareous samples. 



Evidences of stratification of siliceous and calcare- 

 ous organic remains and clay were observed in two of 

 the siliceous oozes collected between Boca Perde and 

 Christmas Island in the central Pacific, namely, sample 

 79, radiolarian ooze and sample 81, siliceous Globiger- 

 ina ooze. It is noteworthy that Challenger sample 270 

 from this same region showed a similar stratification. 



Distribution of Deposit Types 



Chart 1 shows many of the routes or areas in the 

 region of the Pacific covered by the Carnegie from which 

 bottom samples have been collected by other ships and 

 expeditions. Only those expeditions have been included, 

 however, in which the bottom samples collected either 

 are described in publications or have been available for 

 examination by the writer. In addition, the location, de- 

 posit type, and percentage of calcium carbonate of the 

 samples collected by the Carnegie are shown on chart 1. 



Chart 2 shows the probable general distribution of 

 the chief types of pelagic deposits and the boundaries 

 between pelagic and terrigenous deposits in the region 

 investigated: that is, east of 140° east, north of the 

 equator; east of 180°, between the equator and 20° south; 

 and east of 150° west, between 20° and 50° south. Where 

 no new information is available as to the nature of the 

 bottom material or the depth, the maps given by Mur- 

 ray and Lee (1909) for the entire Pacific, and by 

 Hanzawa for- the northwest Pacific, have usually been 

 followed. (See also pages 99 to 126 and chart 10 which 

 describe the distribution of CaC03 In the bottom depos- 



1 Personal communication. 



its of the region.) Since chart 2 was constructed, a cor- 

 responding map of the areal distribution of deep-sea 

 deposits in the Pacific and Indian oceans, prepared by 

 Wolfgang Schott from all available material (including 

 that of the Carnegie) has been published (W. Schott, 

 1935). Although the writer's chart and that of Schott are 

 rather similar in so far as the Carnegie area is concerned, 

 there are several important differences. These are 

 chiefly matters of opinion, either about doubtful areas 

 from which few samples have been described, or as to 

 the criteria for separation of pelagic and terrigenous 

 sediments. 



There are three large areas of Globigerina ooze in the 

 area investigated. Byfar the greatest of these, occupying 

 about ten million square miles, is that which covers most 

 of the bottom of the southeastern Pacific. This area was 

 enlarged by the work of the Albatross, as may be seen by 

 comparing the map of Murray and Renard published in 1891 

 with that given by Murray and Lee nearly twenty years later. 

 On both Schott'sand the writer'scharts this area is extend- 

 ed even farther, as a result of the bottom samples collect- 

 ed by the Carnegie and of the echo soundings made by the 

 Dana. Of the other two large Globigerina ooze areas, 

 that surrounding the Marshall, Gilbert, and Caroline is- 

 lands, between 140° and 179° east and between the equa- 

 tor and 15° north, has been developed through the work 

 of the Japanese and is shown in detail on Hanzawa' s 

 chart. According to Schott, this area is probably con- 

 tinuous with the great Globigerina ooze region of the 

 southwest Pacific, as is also the area between Samoa, 

 Tonga, and Fiji, which is shown on chart 2. In the north 

 Pacific, at depths less than 2000 fathoms, there are nu- 

 merous small areas surrounding oceanic islands or on 

 sharply sloping submerged peaks and ridges which the 

 Challenger workers. Flint (1905) and others, have found 

 to be covered with Globigerina ooze. Many of these are 

 small and uncertain in extent, being based on single sam- 

 ples, some of which were only casually examined, and 

 not all of them are shown on chart 2. 



By far the larger part of the bottom of the north Pa- 

 cific north of 10° north, is covered by red clay; indeed, 

 this is the premier red clay area of the ocean basins. 

 There are, besides, five large red clay areas in the re- 

 gion south of 10° north included on the chart. Two of 

 these lie in the deep water to the west of the zone of 

 terrigenous deposits off the South American coast, one 

 between the equator and 38° south, the other south of 

 45° south. The former extends westward as a wide 

 curved tongue bounded on the southeast by the Merriam 

 Ridge, and turns to the north up to 5° south as a narrow 

 strip which includes the Bauer Deep. The third area 

 lies, in general, west of 140° west, except for an inden- 

 tation between latitudes 30° and 43° south. It is part of 

 the large red clay area of the central south Pacific 

 shown on Schott's chart. The fourth red clay area be- 

 tween the equator and 6° north and 152° to 140° east is 

 based on Hanzawa's chart. North of 10° south, between 

 170° west and about 180°, there is also a belt of red clay, 

 continuous with the great north Pacific red clay region. 



The long strip of radiolarian ooze shown on chart 2, 

 and on the map of Murray and Lee, to extend west of the 

 zone of terrigenous deposits off the Central American 

 coast between about 7° and 15° north to 165° west, and 

 thence southwest to about 10° south, is based principally 

 on samples collected at its western and eastern extrem- 

 ities. It is not believed by Schott to be continuous. The 

 central part is almost entirely unexplored. The fact that 



