Árbók Hins íslenzka fornleifafélags - 01.01.1994, Page 180

184
ÁRBÓK FORNLEIFAFÉLAGSINS
SUMMARY
Tephrocinronology and ice core studies give age determinations that can be used to date
archaeological remains. Tephrochronology is based on classical stratigraphical principles
and in Iceland it forms a consistent system that can be used to obtain relative histories of
many aspects of volcanic activity, soil erosion etc. Prehistoric ash layers have been dated by
"C, and, more recently, by ice cores. Historic ash layers can be dated using careful scrutiny of
historical sources and the relative position of individual layers within the overall scheme of
tephrochronology.
In recent years, Vilhjálmur Örn Vilhjálmsson (VÖV), an archaeologist, has published five
almost identical versions of a paper in three languages. In these he suggests that tephro-
chronology, as established by the late Sigurður Þórarinsson and expanded by other geolo-
gists, is based on circular arguments and sloppy fundamental work that makes its use more
harmful than useful in archaeology. He also makes some serious allegations about workers
in the fields of "C dating and ice core studies.
Tephrochronology is based on the use of ash layers in soil profiles. By using widely dis-
tributed layers as marker horizons in soil profiles from all over Iceland these have been cor-
related to form a comprehensive system which is now being expanded to cover the North
Atlantic. VÖV has not succeeded in demonstrating any major discrepancies in this chronolo-
gy, and his comments are shown to be based on a lack of fundamental knowledge and
understanding of tephra stratigraphy. VÖV is also under the misapprehension that the his-
torical part of tephrochronology is based on l4C dating. This is not the case except only partly
for the oldest historical ash layer, the Settlement Layer which was deposited near the time of
the oldest archaeological remains and signs of initial settlement. "C dates, the relative posi-
tion of the layer in soil profiles and soil thickening all indicate the middle or second half of
the ninth century.
VÖV's understanding of volcanic traces in Greenland ice cores is also seriously flawed as
he does not realise that explosive eruptions are confined to certain volcanic zones and that
volcanic emission are rapidly reduced in strength in proportion to the distance from their
source. An emission from a small distant explosion can not be amphlified in the atmosphere
on its way to Greenland to produce a large trace.
With respect to "C dating VÖV appears to have only a limited understanding of some of
the fundamentals, which leads him into serious trouble and inconsistencies in his interpreta-
tions of determinations from Þjórsárdalur.
The allegations of incompetence that VÖV makes about geologists in general and some of
the scientists working on ice cores and "C dating are totally unfounded, and it is to be regret-
ted that respectable journals should publish them without the customary peer review
process of scientific journals.