417 



afforded for the identity between nil the characteristics of the rocks 

 which ai'B maintained lo be the fossil eqnivalents of the recent 

 dee|)-sea deposits ami of those latter deposits themselves the |)robabi- 

 lity must increase of tliis equivalency being generally accepted. Up 

 to the present it must be admitted, notwithstanding the almost 

 absolute similarity, which has been proved to exist between recent 

 radiolarian ooze, and triassic and Jurassic radiolarites from some 

 Alpine localities, from Borneo, and some other islands in the East 

 Indian archipelago, one biipiiiidnt and nniKirLubli' c/innictmstic of 

 recent abysmal deposits, i.e. t/ic concfntrntion af o.rides of mangnnese 

 in nodules has hitherto never been observed in fossil deep-sea 

 deposits forming part of conlinenlal areas '). 



To what e.rtent, and in inhlch. waij mnminni'ne nodules are 

 characteristic of (dji/sinal deposits? 



The accumulation of oxide of manganese or shortly of manganese 

 in recent deep-sea deposits is very striking; almost without exception 

 manganese ^) is found in all deep-sea deposits, ('oncretions of man- 

 ganese of various dimensions are especially abundant in true abysmal 

 deposits, i. e. the red clay and the radiolarian ooze. 



MuüKAY ') in his latest book on deep-sea deposits remarks: "The 

 oxydes of iron and manganese... in certain abysmal regions of the 

 ocean . . . form concretions of larger or smaller size, which are 

 among the most strildng characteristics of the oceanic red clay." 



The question arises, whether, and to what extent, nodules of 

 manganese must be considered characteristic e.rclusivel(/ of abysmal 

 deposits; do they occur in such deposits onli/ or also elsewhere? 



In the report of the Challenger-expedition, and in the memoir of 

 Murray and Hjort ') quoted above it is reported that such nodules 

 of manganese have been dredged from shallow deptlis, and that they 

 have been found to occur there even in abundance, in some places. 



^) Philippi says about this wliile treating the probability of the occurreoce of 

 deep-sea deposits in former geological formations : "Auch sind meinens Wissens 

 die fur recente Tiefseeablagerungen so charakteristisolien Manganknollen .... 

 bisher noch aus keiner [•'ormation bekannt geworden." E. Philippi. Ueber das 

 Problem der Scbicbtung und iiber Scliiohtbildung am Boden der lieuligen Meere. 

 Zeitschr. d. deutscben geol. Ges. LX, p. 356, 1908. 



') T. Murray and A. F. Renard say: "Rarely can a large sample of any mud, 

 clay or ooze be examined with care without traces of the oxides of this metal 

 being discovered, either as coatings or minute grains." 



') J. Murray and J. Hjobt. The depths of the ocean, p. 155, Londen 1912. 



■I) I.e. p. 157. 



