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Suomen Geologinen Seura. N: 0 35. Geologiska Sällskapet i Finland. 113 Phosphoritic nodules are found, for example, on the top and sides of banks, on steep escarpments which appear to be fault scarps, on the walls of submarine canyons, and on the break of the continental shelf (Mero 1961, p. 7). All the localities where phosphorites are found are essentially nondepositional environment (Dietz et al. 1942). The nodules must be in contact with the water to accrete. On ce buried in sediment, the nodules will cease to eruarge by accretion of colloidal particles (Mero 1961, p. 7) . Discontinuous layering occurs within the nodules. This has usually been explained as due to covering by sediment, which would stop the growth process, with subjacent erosion of the unconsolidated sediment cover, exposing the nodules to sea water again. However, this discontinuous layering as well as the growth of the nodules might also be discussed in the light of the uplifting effect or other rearrangements of the nodules owing to seismic vibrations. Such vibrations might be able to separate larger particles from finer particles, to lift them up to the sediment surface or to move them in a horizontal direction (cf. Fig. 2). Most phosphoritic nodules in the California region seem to have been formed during the Miocene (Mero 1961, p . 4). This epoch is known for intense volcanic activity in that area and at the same time likely a seismic one as well. Another irregularity concerns the distribution of »cosmiC» spherules. In some cores their number increases towards the top of the core (Fredriksson 1959). This is also true in older strata (Lower Miocene in age) outcropping at the bottom (Core 90; diagram by Pettersson and Fredriksson 1958). However, the density of these grains is greater than the density of the solids in oozes and clays and, therefore, the uplifting effect of vibrations may be reduced or even reversed. Burri and Koczy (1956) made an experiment on a clay suspension with a water content of 60 % and with a regular distribution of artificial magnetic spherules. By vertical vibrations produced by a small hammer striking the bottom of a container during 5 days, they finally obtained a distribution of the spherules increasing upwards. The magnitude of the accelerations used is not known. ACKNOWLEDGMENTS Acknowledgment us hereby given to the following agency, whose support made this research possible: Office of Naval Research, contract No. Nonr 840(01). For suggestions and discussions the authors are greatly indebted to Drs. M. Bäth, N. Jerlov, O. Joensuu, F. F. Koczy, B. Kullenberg, and G. Rusnak.
REFERENCES BAAS BECKING, L. G. M. and MOORE, D. (1959) Density distribution in sediments. J. Sediment. Petrol. 29, pp. 47-55. BURRI, M. and Koczy, F. F. (1956) Effet de secousses sur la classification d'un sediment. Manuscript. BUTTLER, V. V. and HOUTERMANS, F. G. (1950) Photographic determination of activity distribution in manganese lumps of deep-sea origin. Nature 37, pp. 400-401. DIETZ, R. S., EMERY, K. O. and SHEPARD, F. P. (1942) Phosphorite deposits on the sea floor off southern California. BuH. Geol. Soc. Amer. 53, pp. 815-848. FRASER, H. J. (1935) Experimental study of the porosity and permeability of clastic sediments. J. Geol. 43, pp. 910-1010. FREDRIKSSON, K. (1959) On the origin, age and distribution of »cosmis spherules». Int. Oceanogr. Congr. Preprints. AAAS, Washington, pp. 456-457. GOLDBERG, E. D. and ARRHENIUS, G. O. S. (1958) Chemistry of Pacific pelagic sediments. Geochim. et Cosmochim. Acta 13, pp. 153-212. GUTENBERG, B. and RICHTER, C. F. (1949) Seismicity of the Earth. Princeton Univ. Press. HAMILTON, E. L. (1960) Ocean basin ages and amounts of original sediments. J. Sediment. Petrol. 30, pp. 370-379. HOWELL, B. F . (1959) Introduction to geophysics. McGraw-Hill, New York. MENARD, H. W. (1960 a) Consolidated slabs on the sea floor of the Eastern Pacific. Deep-sea Research 7, pp. 35-41. -»- (1950 b) The East Pacific Rise. Science 132, pp. 1737-46. MENARD, H. W. and SHIPEK, C. J. (1958) Surface concentrations of manganese nodules. ature 182, pp. 1156- 1158. MERo, J. L. (1960) Mineral resources on the ocean floor. Mining Congr. J. Oct. 1960. -»- (1961) Sea floor phosphorite. Mineral Information Service 14, o. 11, pp. 1- 12. NEUMANN, F. (1954) Earthquake intensity and related ground motion. Univ. of Washington Press, Seattle. OLAUSSON, E. (1961) Remarks on some Cenozoic core sequences from the central Pacific, with a discussion of the role of coccolithophorids and foraminifera in carbonate deposition. Medd. Oceanograf. Inst., Göteborg 29. PETTERSSON, H. (1943) Manganese nodules and the chronology of the ocean floor. Ibid. 6. PETTERSSON, H. and FREDRIKSSON, K. (1958) Magnetic sph erules in deep-sea deposits. Pacific Sci. XII, No. 1, pp. 71-81. RICHTER, C. F. (1958) Elementary seismology. Freeman, San Francisco. SHIPEK, C. J. (1960) Photographic study of some deep-sea floor environments in the eastern Pacific. BuH. Geol. Soc. Amer. 71, pp. 1067- 1074. -»- (1961) Surveying the deep-sea floor with cameras. Photogrammetric engineer ing, March, pp. 84-91. TERZAGHI, K. (1957) Varieties of submarine slope failures. Harvard soil mechanics series, No. 52.
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