Magnetic Spherules in Deep-sea Deposits 
Hans Pettersson and Kurt Fredriksson 1 
Few of the components entering into the 
sediments covering the ocean floor have at- 
tracted so much attention as the magnetic 
spherules first described in 1876 by Sir John 
Murray. Struck by the resemblance of their 
surface structure to that of iron meteorites, 
Murray called them "cosmic spherules." The 
number he was able to extract from one quart 
of the deposit, by means of a small magnet, 
varied from 20 to 30 in samples of Red Clay, 
whereas in the same quantity of Globigerina 
Ooze only one or two were found (Murray, 
1876). 
Together with A. F. Renard, Murray later 
published (1897) a more detailed description 
of the spherules in volume 4 of the "Chal- 
lenger” Reports, Deep Sea Deposits. The higher 
numbers found in the Red Clay are ascribed 
to its much lower rate of sedimentation. 
Hoping that the method of counting the 
magnetic spherules present in different kinds 
of deposits may afford a solution to the 
difficult problem of determining the rate of 
deep-sea sedimentation, one of us decided to 
include in the equipment of the Swedish 
Deep-sea Expedition (1947-48) special corers 
of wider diameter than those otherwise used 
from the "Albatross," viz., with an internal 
diameter of 90 mm. instead of the usual 46 
mm. For various technical reasons this wide- 
bore corer was not used until we reached the 
western Pacific Ocean (Pettersson, 1956). Ow- 
ing to the higher resistance offered by the 
1 Oceanografiska Institutet, Goteborg, Sweden. 
Manuscript received November 20, 1956. 
The following investigation has been made possible 
through generous grants from His Majesty King 
Gustaf Adolf VI Fund, for which support we beg to 
offer our most respectful thanks. Also, we have twice 
received grants in support of our work from Karin och 
Herbert Jacobssons Fond, for which we beg to offer 
our cordial thanks. 
sediment to a thick coring tube, and owing 
to the necessity of avoiding too heavy a strain 
on the steel cable used when coring, the 
length of the thick corer had to be limited to 
only 6 metres, as compared to the 15 to 20 
metres of the narrower coring tubes. The 
length of the thick cores raised was, therefore, 
in general only 5 to 5!4 metres. On the other 
hand, from a section taken from a thick core 
about four times more material was obtained 
than from a narrow core of the same length. 
In all, a dozen of such thick cores were raised 
from the cruise with the "Albatross” through 
three oceans. 
Owing to more pressing work on other 
material collected during the cruise, the work- 
ing up of the thick cores for magnetic spher- 
ules had to be postponed for several years 
after our return from the expedition. How- 
ever, in the meanwhile a young technician, 
T. Laevastu, then in the employ of the Ocean- 
ographic Institute in Goteborg, was charged 
with carrying out preliminary extraction ex- 
periments using parts of a narrower core of 
Red Clay raised from the central Pacific 
Ocean. For this work an electromagnetic ex- 
tractor of high efficiency had been obtained 
from the well-known New York firm of 
Frantz. Portions of the sediment suspended 
in water were passed through this extractor. 
Already in the preliminary experiments with 
this instrument its great superiority over the 
primitive method for extraction used by Mur- 
ray was apparent, the number of spherules 
extracted from 1 kg. of Red Clay varying 
between a few hundred and a couple of 
thousands. Attempts to estimate the efficiency 
of the method were also carried out by adding 
to sediment already extracted a counted num- 
ber of artificial magnetic spherules, made from 
iron wire with the oxygen flame, having 
slightly larger dimensions though than the 
71 
