SEASONAL BANDING IN GLACIAL CLAYS. vé 
with regular intervals along a line extending from the southernmost to the central part of 
Sweden it has been possible not only to sum up the whole series of centuries it has taken for 
the ice-border to retire this distance, or some 800 km, but also to estimate the length of the 
postglacial epoch after the disappearance of the ice and up to our days. 
“Of the late glacial sediments the most important is a glaci-marine clay, the “varvig 
lera” (hvarfvig lera), so called from its “varves” (2) or its periodical lamin of different 
colour and grain. 
“Already at my first field-work as a geologist, in 1878, I was struck by the regularity 
of these laminz, much reminding of the annual rings of the trees. The next year, therefore 
I commenced, and during the following years pursued, detailed investigations and measure- 
ments of these laminee in different parts of Sweden. The laminz were found to be so regular 
and so continuous that they could scarcely be due to any less regular period than the annual 
one. I therefore ventured in 1882 to advance the view that there might be a close connec- 
tion between the periodical lamin of the clay and the annual ablation of the land-ice (3). 
Two years afterwards the investigations had proceeded so far that, being confirmed in my 
opinion that the laminze were really annual, and having found out a way for correlating 
annual layers at different places by means of diagrams, I could, in a lecture read before our 
Geological Society in Stockholm, indicate the way by which a real chronology for the last 
part of the Ice-age could be obtained (4). A few months afterwards I also succeeded in 
finding the first correlation between the clay-layers at three points, though not very far from 
one another. In 1889 I found — and mapped — in the neighborhood, NW of Stockholm, 
a thereto [hitherto] overlooked kind of certainly quite small, but very characteristic terminal 
moraines, which proved to be periodically arranged in rows with somewhat regular intervals 
of about 200-300 m. This led me to point out the possibility that these ridges might corre- 
spond to the stop in the recession of the ice-border, which was probably caused by each 
winter, and that this might be ascertained by investigation of the successive annual clay- 
layers between some neighbouring ridges (5). This kind of moraines has since that time been 
found to be quite common in the lower parts of the land, and at first I had therefore the 
intention of pursuing the chronological investigations by means of a careful mapping of the 
annual moraines. 
* * * * * 
“By detailed studies of some oses, especially at Stockholm and Uppsala, and, later 
on, also at Dal’s Edit had turned out that also the oses are of a pronounced periodical structure, 
marked by centres of coarser material, on their southern side gradually passing into finer 
gravel and sand. This led me to a new explanation of their formation as successive sub- 
marginal delta-deposits, formed in the glacier-arches of the receding land-ice, and probably 
corresponding to the annual “varves” of the finest, clayey sediment and to the annual mo- 
raines (6). 
“Finally, in 1904, I happened to get a very good correlation between two clay-sections 
1 km apart from each other, and now I determined to make an earnest attempt to realize 
my old plan for a clay-chronology. 
“By investigating some forty points in the Stockholm region it was soon found that the 
clay-correlation offered less difficulty than thereto suspected and was — the localities of 
observation being well chosen —as a rule performable at. distances of 1 km. This being 
ascertained, I secured the assistance of a number of students from the universities of Stock- 
holm and Uppsala, ten from each, and after some training they went all out on a summer 
morning in 1905, each of them to his special part of a line about 200 km. long, running, as seen 
from the map Pl. 1, past Stockholm and Uppsala through the Sédermanland-Uppland penin- 
sula, from the great Fennoskandian moraines at its southern end to the river Dalilfven to 
a 
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