362 THORLEIFUR EINARSSON 



part of the peat contains marine diatoms whereas the higher part has only 

 freshwater diatoms (Jonsson, 1956, 1957). The isostatic recovery continued 

 and kept pace with the eustatic sea level rise during the Boreal and Atlantic 

 periods. 



A pollen diagram from Seltjorn (Th. Einarsson, 1956, 1961) shows the 

 first great Betula-maximum (pollen zone B), the following Atlantic Betula- 

 minimum, and the first part of the second great 5e/»/a-maximum. The 

 transgression submerged the Seltjorn bog and stopped the peat formation in 

 Sub-Boreal time. Seltjorn is today a bay. The subsidence in this area is more 

 than 4 m, and the transgression is still continuing. Submerged peat has been 

 found in many localities in Iceland (Bardarsson, 1923; Thorarinsson, 1956; 

 Jonsson, 1957). Only at Hri'itafjordur, northern Iceland, is there evidence of a 

 transgression in Sub-Boreal time, the Purpura (Nucella) transgression, with a 

 following regression (Bardarsson, 1910; Thorarinsson, 1955). Trausti 

 Einarsson (1961) has argued against the transgressive trend on the Icelandic 

 coasts in the last few thousand years, and denies the submerged peat as proof 

 for a subsidence. 



As mentioned before, the birch forest dechned from ca. 2500 B.P. to the 

 onset of the settlement, the "landnam". In a short history of Iceland (Islend- 

 ingabok), written about 1 120, Ari the Wise Thorgilsson (1067-1 148) says that 

 Iceland was covered with woods between "coast and mountain", when the 

 "landnam" began. Iceland was colonized mainly from Norway in the years 

 A.D. 870-930. After the beginning of the "landnam", the birch forest was 

 devastated very rapidly as can be seen from the detailed pollen diagram from 

 Skalholt in southern Iceland (Fig. 5). Skalholt was probably settled early in 

 the tenth century and in 1056 the farmstead became the residence of the 

 Icelandic bishops and was until the end of the eighteenth century the cultural 

 center of Iceland. In the pollen diagram from Skalholt (Fig. 5) the first column 

 shows the sediment (Carex-moss-peat) with the tephra layers K-ca. 5500 

 B.P., H4 - 4000 B.P., H3 -2700 B.P., and G, which according to the pollen 

 studies was formed during an eruption in the Torfajokull area, southern 

 Iceland, during the "landnam" period, i.e. a.d. 870-930. The rhyolithic 

 tephra layer Hi was formed in a Hekla eruption in the year a.d. 1104. 

 This ash-fall destroyed the district Thjorsardalur 30 km east of Skalholt. 

 The two top-most basaltic tephra layers were deposited during the eruptions 

 of Hekla in 1693 and of Katla in 1721 respectively. 



Column A shows the proportion of inorganic-organic constituents of the 

 peat. The inorganic constituents are much higher in historic times than 

 before, because of the sedimentation of eolian dust from the soil erosion that 

 began after the settlement (Bjarnason, 1952; Th. Einarsson, 1961; Thorar- 

 insson, 1961). This soil deflation began early in historic times. 



Column B shows the proportion of Cyperaceae pollen (shaded) to all other 

 pollen grains. Column C shows the proportion of Salix, Gramineae, and 



