i a NI a ed 
SEASONAL BANDING IN GLACIAL CLAYS. 9 
“Tivery following mild season caused a new recession and a formation of a new fan of 
gravel, sand, and clay. Thus the whole series of those fans are placed as tiles, one over 
another, the uppermost always having their northern, or proximal border extending so much 
over that of the underlying as the ice-border had receded and the sea extended since the last 
year. As the recession was often very regular, the handles of the fans were gradually com- 
bined to ridges, thereby giving rise to the oses, the periodical structure of which has been 
afterwards often more or less concealed by the smoothening wave-action during the later 
land-emergence. 
“From this cause and owing to the thickness and coarseness of the material together 
with the casualities in its deposition the most proximal parts of the annual layers are as a 
rule not well adapted for direct chronological determinations, though, of course, a regular 
development of the very ose-deposits is a reliable sign that the ice-recession in such a region 
has been of a corresponding regularity. 
“Yet, it is the fine, extraglacial, clayey sediment that affords the most valuable means 
for the chronological investigations.” DE GEER, 1912, p. 241-245. 
At this point de Geer described the method used in counting the annual 
layers. The description is too long to quote. He found the number of late- 
e glacial layers to be about 5,000. He then describes the effect of wave action 
on the deposits and the impossibility of counting the postglacial layers of south- 
ern Sweden. Later on he described how he counted the postglacial layers: 
“This lack of seasonal lamination in the postglacial clays of Southern Sweden made it 
impossible here to fill out the great gap between the late-glacial chronology and the historical 
one. But one of the most energetical and successful of my young collaborators, R. Lidén, 
had found a periodical, and evidently seasonal lamination in postglacial fjord-deposits along 
the river Angermaniilfven in Norrland and also commenced their investigation. This work 
during the first years meeting with great difficulties, I got the idea that the postglacial sedi- 
ments in the Lake of Ragunda, which was totally drained in 1796, might perhaps afford a 
more favourable opportunity for the investigation of the postglacial chronology, and, there- 
fore, in the autumn before the congress I made a visit to Ragunda, just to look if there were 
any chances. These were indeed found to be so great that I determined at once to stay, 
and, by the collaboration of my wife, I succeeded in three weeks to work out a continuous 
section from the morainic bottom, upon which followed about 400 beautifully laminated, 
late-glacial clay-layers and thereupon about 700 somewhat less sharply accentuated layers 
of a black-banded postglacial fjord-clay. This clay passes upwards into well marked seasonal 
fa. layers of alternating fine, sandy sediment and silt, which had certainly for the most part 
with exception of the lowermost ones been deposited in the basin of the ancient Lake of 
Ragunda, since its ose-dammed outlet had been uplifted above the level of the fjord and 
seemingly until 1796, when the whole ose-dam was artificially cut through and the lake 
totally drained, thereby giving us access to such a unique section, registering probably ‘the 
whole postglacial epoch.” DE GEER, 1912, p. 251. 
De Geer found that there were 7,000 of these postglacial layers and these 
added to the late-glacial layers makes 12,000 as the total number of years, 
approximately, since the ice left southern Scania. From his study of the ice 
recession in Sweden, de Geer felt justified in assuming that it took at least 
