Jökull - 01.12.1980, Side 8

the Tjörnes sequence. Bárðarson was convinced
of an angular unconformity and a consider-
able hiatus between the basalts at Kaldakvísl
where he observed dips of 20—30° towards
north, and the Pliocene Crag strata which
dipped up to 10° towards northwest. After
an initial transgression, subsequent Crag
strata had accumulated in sheltered places
such as a fiord or quiet creeks and possibly
lagoons. According to Bárðarson the lignite
seams and barren sandstones were dry land
deposits or possibly formed in fresh water
lakes cut off from the sea. He considered most
of the marine deposits to be shallow water to
littoral sediments. He divided the sedimentary
sequence of alternating shelly nrarine and
terrestrial beds between Kaldakvísl and
Höskuldsvík into three biozones (Table 1). For
the lowest of these, the Tapes Zone, Bárðarson
inferred a sea temperature similar to that of
the present day west or south coast of Norway.
At the time of formation of the Mactra Zone,
Bárðarson suggested climatic conditions at least
as favourable as those now prevailing on the
warmest range of the Norwegian coast or pos-
sibly approximating the climate of the British
Isles to-day. When it came to the deposition of
the Cardium (= Serripes) groenlandicum Zone the
temperature must, according to Bárðarson,
have varied from at least that of the west coast
of Iceland to-day up to that of the British Isles
to-day. Bárðarson did not accept Pjetursson’s
conclusions about a glacial origin of any of the
Breiðavík deposits, and concluded that the
temperature remained similar to the present
conditions-on the west coast of Iceland. He
considered both the three biozones of the
Tjörnes beds and the Breiðavík beds to be of
Pliocene age. Bárðarson pointed out that the
Icelandic Pliocene fauna was altogether very
closely allied to the English Crag fauna. A
revised outline of the geology of Tjörnes was
included in the second edition of Bárðarson’s
(1927) textbook on geology.
Fossil shell collections from Tjörnes were
examined and described by Harmer (1914—
1925) in his work “On the Pliocene Mollusca
of Great Britain”.
Emilsson (1929) made some observations on
Tjörnes. He discovered that the Tjörnes beds
have an extension as far south as the farm
Rauf (now Eyvík), where he collected and
identified marine fossils. Emilsson also
examined fossil plant remains from lignite
seams, and concluded that the lignite material
had been supplied by local vegetation. He also
mentioned a thin fossiliferous shale bed near
Húsavík, interbedded between two moraines.
During the second quarter of this century,
stratigraphical investigations in Iceland con-
tinued within the framework provided by
Pjetursson’s work, which became generally
accepted (e.g. Nielsen and Noe-Nygaard 1936).
Askelsson (1935a, 1935b, 1938, 1939) studied
the fossiliferous beds in Breiðavík on Tjörnes,
and interpreted the presence of the cold-water
species Portlandia arctica as a proof of their
Pleistocene age. Later he published general
descriptions of the Tjörnes sequence and the
fossil material conserved there (Áskelsson 1941,
1960a, 1961). Áskelsson (1960b) compared the
marine fossils of the Tjörnes beds with the
Pleistocene Skammidalur fauna in South Ice-
land and concluded that the Skammidalur
formation was of the same age as the Serripes
Zone of Tjörnes. Accordingly, he stated, the
Serripes Zone must be of old Quaternary age.
A general description of the Tjörnes beds
was presented by Laursen (1936), who dis-
cussed temperature changes reflected by the
fossils and ascribed the beds to the Pliocene.
Líndal visited Tjörnes in 1939 and 1941 and
made several observations on stratigraphy
and the origin of the sedimentary beds, es-
pecially in the Furuvík and Breiðavík outcrops
as well as in the Búrfell area (Fig. 2). His
discovery of lava flows intercalated in the
Breiðavík sediments is of particular import-
ance. Líndal’s diaries were published in 1964.
A brief account of the Tjörnes sequence was
given by Kjartansson (1952), who considered
the Tjörnes beds to be of Pliocene age and to
have been deposited in a graben.
The Lexique Stratigraphique International
includes a section on the stratigraphy of Ice-
land compiled by Tryggvason et al. (1956). The
6 JÖKULL 30. ÁR