. The Earth beneath the sea : History . Fig. 11. Frequency of cosmic iron spherules as a function of depth in core 90, Swed. Deep-Sea Exped., from the West Pacific. (After Pettersson and Fredriksson, 1958.) Paleontological investigations by Bramlette and Riedel (quoted by Olavisson, 1961) indicate an unconformity between Quaternary and Lower Miocene at about 56 cm depth. have formed from molten drops in the atmosphere; these are probably original cosmic particles or fragments of chondritic meteorites breaking apart at entry into the atmosphere. Studies of the cosmic components of pelagic sedim
. The Earth beneath the sea : History . Fig. 11. Frequency of cosmic iron spherules as a function of depth in core 90, Swed. Deep-Sea Exped., from the West Pacific. (After Pettersson and Fredriksson, 1958.) Paleontological investigations by Bramlette and Riedel (quoted by Olavisson, 1961) indicate an unconformity between Quaternary and Lower Miocene at about 56 cm depth. have formed from molten drops in the atmosphere; these are probably original cosmic particles or fragments of chondritic meteorites breaking apart at entry into the atmosphere. Studies of the cosmic components of pelagic sediments were originally carried out by Murray and Renard {op. cit.). Recent extensive investigations by Hans Pettersson have focused on the variation in time of the accretion of cosmic material. The results of Pettersson and his co-workers (Pettersson and Fredriksson, 1958; Fredriksson, 1958; Castaing and Fred- riksson, 1958; Laevastu and Melhs, 1955; Pettersson, 1959a; Fredriksson, 1959) indicate marked, world-wide changes in the rate of accretion of metallic spherules during Cenozoic times (Fig. 11). Hunter and Parkin (1960) have also 1 The presence of this latter mineral is not evident from the work of Hunter and Parkin (I960) but has been established in similar chondrules by Murray and Renard (1891) and Bramlette (unpublished).
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