Jökull - 01.12.1992, Page 66

Þorvaldur Thoroddsen. 1889. Jarðfræði. Sjálfsfrœðarinn,
fyrri flokkur, 2. bók. Sigfús Eymundsson, Reykjavík,
73 bls.
Þorvaldur Thoroddsen. 1896. Nogle iagttagelser over surt-
arbrandens geologiske forhold i det nordvestlige Island.
Geol. Fören. Förhandl. 18: 114-154. Sjá einnig Land-
fræðisögu Þ.Th.
ÞorvaldurThoroddsen. 1908. Lýsing Islands, II. bindi. Hið
íslenzka bókmenntafélag, Kaupmannahöfn.
Þorvaldur Thoroddsen. 1922. „Naturforhold", bls. 540-551
í kafla um Island í Salmonsens Konversations-Leksikon,
2. útg., 12. bindi. Köbenhavn.
Östrup, E. 1896, 1900. Diatomeeme i nogle islandske
surtarbrand-lag. Medd. Dansk Geol. Foren. (3): 85-94
og (6): 23-30.
SUMMARY
HISTORY OF OPINIONS ON THE AGE OF
ICELAND
This paper traces the history of ideas regarding the
geological "age of Iceland", as determined primarily
from plant fossils exposed in the older lava sequ-
ences of the island. The first statement on this age
to become generally known among geologists, was
that of the great Swiss paleontologist Oswald Heer
(1809-1883). It is contained in vol. III of his "Flora
Tertiaria Helvetiae" as well as in a short paper pu-
blished in the same year (Heer 1859a,b). Heer’s
opinion of a Lower Miocene age for fossil outcrops
in the Northwest peninsula of Iceland was reitera-
ted in the first volume of his "Flora Fossilis Arctica"
(Heer 1868a). It should be noted that Heer’s Central
European Lower Miocene corresponded to the Upper
Oligocene in North Germany, the Oligocene having
been suggested as a separate epoch in 1854. Heer
also studied a number of other fossil floras from the
Arctic and from Britain, finding almost all of them to
be either Miocene or Mesozoic. Heer’s procedures in
classification of these fossils were criticized, as well
as the estimates of ages and of annual temperatures
which he derived from the plant assemblages.
In particular, a dispute developed in 1878-
79 between Heer and the British geologist J-
Starkie Gardner (1844-1930) who was studying fossil
localities in South England. He claimed, originally on
the basis of somewhat slender arguments, that the
British and Arctic floras were much more likely to be
Eocene than Miocene. Gardner’s preferred explanati-
on for major changes in climate was also much dif-
ferent from that of Heer. After visiting Iceland in
1881, Gardner (1885a,b) became convinced that the
Iceland flora was significantly younger than the oth-
ers. Gardner’s conclusions on the age of South Eng-
land floras were generally accepted very soon, but
reactions to his other ideas were mixed. He seems to
have dropped out of paleobotanical research by 1895,
to become an expert on metalwork. In the following
decades however, new fossil discoveries supported the
view of an Eocene age for the Northern British and
Arctic areas. Petrologic findings, for instance by Hol-
mes (1918), indicated the unity of a "Thulean basalt
province" between Britain and East Greenland, and
in North America the concept of a widespread Eocene
temperate "Arcto-Tertiary flora" (see Wolfe 1977) was
popular until about 1960. In this time, Gardner’s
important disclaimer regarding Iceland was forgotten.
New paleontological and palynological work on
Icelandic material by Askelsson (1946) and Pflug
(1956, 1959) appeared to confirm an Eocene or even
older age. This view hence prevailed through the
critical early years of continental drift revival (e.g-,
Wilson 1963), and was not refuted until mid-Miocene
K-Ar dates on the older lava series in Iceland app-
eared in 1967-68. Along with certain other persistent
erroneous conceptions of the geology of Iceland, the
view of an Eocene age may have delayed the general
acceptance of sea fioor spreading by local scientists.
64 JÖKULL, No. 42, 1992