Náttúrufræðingurinn - 1962, Blaðsíða 37

NÁTTÚR UFRÆÐIN GURINN
131
fjall in the Mývatn area, Northern Iceland. The layer (cf. Fig 2) was deposited
ahout 2500 years ago and the hollows (Figs. 3 and 4) are found in the area be-
tween Hverfjall and the craters of Jardsbadshólar. The birchtrees buried in
the Hverfjall tephra are on average somewhat bigger than those now growing in
the Mývatn area.
In the spring 1961 a pit was dug through the tephra layer H3 in Rangár-
botnar, 10 km NW of Hekla, where the layer has a thickness of about 5 m. This
pit revealed a branched tube left by a birch tree embedded in the tephra layer.
Some charcoal was found on the inner walls of this tube and a C14 dating
carried out by Laboratoriet för radioaktiv datering, Stockholm (St 813) gave
the age 2820 ± 70 years. The tephra layer H3 is a rhyolitic layer from Hekla
and the most extensive of all postglacial tephra layers found in Iceland,
covering about 80 000 km2 of the country’s area. A previous C14 dating (Y-85)
of peat immediately underlaying H3 gave the age 2700 ± 130 years. In a
nearby pit in Rangárbotnar small pieces of charcoal were found in a brown-
black tephra layer from Hekla, situated above Ha and separated from that
layer by a 30 cm thick layer of alluvial sand and loessial soil. C14 dating of
this charcoal (St 814) gave the age 2660 ± 80 years.
The author stresses the desirability of combining the C14 method and the
tephrochronological method when establishing a postglacial chronology in
Iceland.
Jónas Jaliobsson:
Fuglahrakningar
í fyrrahaust hraktist hingað til lands talsvert magn a£ íartugl-
um, mest spörfuglar, sem verpa á Norðurlöndum, en færa sig
suðvestur á bóginn, þegar haustar. Samkvæmt frásögn dr. Finns
Guðmundssonar komu aðallega tveir fuglasveimar. í rökkrinu að
kvöldi 8. október 1961 sáust nokkrir fuglar á Kvískerjum í Öræf-
um, og daginn eftir var orðið krökkt af þeim. Seinni komudag-
urinn var 24. október, en þá sást allmikið magn.
Stórhópar af Evrópu-fuglum koma ekki að tilefnislausu alla
leið hingað norður til íslands að haustlagi um sólarhrings ferð
yfir opið haf. Liggur beinast við að leita orsakanna í veðurfari
— stormi eða dimmviðri. Eftirfarandi niðurstöður eru fengnar með
athugunum á veðurkortum frá þessum dögum.