Jökull - 01.12.1988, Page 58

Fig. 1. Location map. Legend: 1) Recent sediments; 2) Recent lava flows; 3) Lava flows chiefly erupted
during the Brunhes chron; 4 and 5) Lava flows and sediments formed during the Matuyama chron respec-
tively; 6 and 7) Lava flows and sediments formed during the late Gauss chron; 8 and 9) Lava flows and
sediments older than 3.1 Ma. (Redrawn from Eiríksson et al„ 1987).
Myndl. Staðsetningarkort. 1) Setmyndanir frá nútíma; 2) Hraunlög frá nútíma; 3) Hraunlög frá Brunhes
segulskeiði; 4 og 5) Hraunlög og setlögfrá Matuyama segulskeiði; 6 og 7) Hraunlög og setlög frá síðari
hluta Gauss segulskeiðs; 8 og 9) Hraunlög og setlög eldri en 3,1 milljón ára. (Eiríksson o.fl., 1987, endur-
teiknað).
mudrocks with marine fossils. The grain size trend is
then reversed and conglomerates, sandstones or lava
flows conclude a typical cycle. Eiríksson et al. con-
cluded that the cycles should be interpreted in terms
of glacial-interglacial cycles. They presented a ten-
tative correlation with a palaeomagnetic time scale
and with the Tjömes sequence. The correlation
which was based on palaeomagnetic measurements
of samples from the sediments and lava flows, fos-
sils, and on lithological units such as tuff layers,
indicated Matuyama age with two normal polarity
events represented in the core (Fig. 2).
The main objective of the present paper is to re-
port new absolute ages for the Flatey core lava
flows. There are at least two reasons as to why this
objective is important. Firstly, the dates put con-
straints on the frequency of glaciations of the area
and enable a correlation not only with an absolute
time scale, but also with the Tjömes sequence. Sec-
ondly, the knowledge of the age of certain horizons
in the core has a broader significance for the tecton-
ic evolution of the Tjömes Fracture Zone and may
enable estimates of subsidence and uplift rates.
56 JÖKULL, No. 38, 1988