Rit (Vísindafélag Íslendinga) - 01.06.1923, Blaðsíða 118

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siderably below this boundary and then rose again to that
level (No. 4 in Fig. 8). Some considerations seem to indic-
ate that the latter is the more probable, but further in-
vestigations will be necessary before this matter can be
decided with any certainty.
The lowest and oldest shell strata in Borgarfjörður (Neðra-
nes etc.) were probably formed by the re-elevation of the
coast-line up to the above-mentioned level. The species are
arctic and correspond mostly to those now found on the
iwrth and cast coasls of Iceland. (Astaric Bariksii, var. striata,
much more common than the typical form). The clay strata
higher up in these terraces were probably formed when
the coast-Iine was at the 40-50 m. boundary, for the
molluscs found in these strata must have lived at a depth
corresponding toa sea-level 40-50 m. higher than at present,
and these mollusc íauna correspond to those now living
on thc north coast of lceland or the northern part of the
west coast. (?) The upper clay strata in the marine terraces
at Grjóteyri (No. 3 in Fig. 1) and Gröf (No. 2 in Fig. 7)
were also formed at that time. In both of these boreal
species are found (Anomia squaniula).
5. Once more the land rose, so that the coast-line at
Faxaflói receded from the 40 — 50 m. level, and finally fell
to 4—5 tn. below the present sea-Ievcl (No. 5 in Fig. 8).
At the beginning of this period the shell strata were íormed
which are found high up in the lower marine terraces
(15 — 20 m. above sea-level) at Borgarfjörður, and which
contain various boreal species (Zirphœa crispata, Cyprina
islandica, Mytilus modiolus etc.) and indicate similar con-
ditions of life to those on the west coast of Icetand (Zirphœa
crispatu). Later in this period the shell strata at Brekku-
höfði (No, 29) and Katanes (No. 28) were formed.
At the end of this period, when the sea stood at the
lowest point, (at least 4 — 5 m. lower than at present), a
submarine bog was formed, which is to be found on the
beach at low tide at Faxaílói. At Borgarfjörður and Hval-
fjörður no fossil shell strata from the same period as this
bog have been discovered, but at Garðsskagi (Útskálar) on