Surtsey - The Volcano Island, Iceland. Fossils on Surtsey.

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Fossils on Surtsey, Iceland

Fossiliferous sedimentary xenolith on Surtsey
Length of hammer 28 cm
© Photo: L.A.Simonarson

'You are never to old to learn', it is said. But I must admit that some new kinds of information sounds more like a joke....like the finding of fossils on Surtsey - an island
only 39 years old . The fossils where obtained as early as 5 years after the eruption!

But according to a report published in the Surtsey Research Progress Report VII in 1974
that is a fact. This is what it says: 'During the Surtsey eruption 1963-1967 fossiliferous
sedimentary xenoliths were carried upwards with the hot magma and are now found
in the tephra on Surtsey.'

Well, that makes it a little more possible to understand, but how did those fossils happen
to ride on the hot magma - and where did it come from?

The report explains: 'Data from a 1.565 m deep drillhole on Heimaey show a
(700 to 800 m ) thick series of sedimentary layers in the stratigraphic column below
the Westmann Islands. Those beds have probably supplied the fossiliferous xenoliths
on the islands.'
So this layer which is believed to cover an area from a bit up the coast inside the Westmann Islands and out as far as behind Surtsey, which is the uttermost of the islands, somehow
consists of old fossils, and when magma came up during the eruption from 1963-1967,
some fragments (xenoliths) of that layer were carried up to the surface.

Foraminifera: cibicides lobatulus

Did they find any dinosauruses, mammoths or something like that? Not exactly.
But quite a lot (several hundreds) of foraminiferas (Foraminifera are tiny single-celled organisms thatconstruct shells. They inhabit a wide range of marine environments,
from the intertidal zone to the deep sea in all regions. - just in case you didn't know).,
Also found were some molluscas (Molluscs are one of the most diverse groups of
invertebrate animals - both in form and habitat. Mollusca: Snails, clams,
mussels, squids, octopi, chitons, and tusk shells).

Arctica islandica, which can be 132 years old
and apparently much more as a fossil....

Several fragments of the mollusca called Arctica islandica were also found, and some of
them were taken from two blocks and dated radiometrically. One block (mainly outer
fraction ) was approximately 11.000 years old, while the other (mainly inner fraction)
was 6.200 years.

The report concluded with the following words: 'The marine fauna consists entirely
of species living at the present time which is in agreement with the radiocarbon dates.
The fauna is, moreover, north boreal, i.e. similar to the fauna of South Iceland today. Several species of foraminifera found in the xenoliths have not been recorded as living nowadays in Icelandic waters. However, the recent foraminifera fauna of Iceland is not sufficiently well known, so a comparison is probably of no great importance.'

The text above is Based upon two reports by Leifur A Simonarson,
Scince Institute, University of Iceland, Reykjavik.
Surtsey Research Progress Report VII and IX.

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