Greinar (Vísindafélag Íslendinga) - 01.01.1977, Blaðsíða 108

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for a long time, and that then, and possibly also earlier, a
thick layer of basalts was eroded and carried away. This was
a zone, uplifted out of shallow ocean, as we shall see, and most
reasonably corresponds to the Oligocene uplift of Iceland (cf.
Chapter 2). Later, probably together with sinking of the ocean
floor which caused the 200 m sinking of sea-level (cf. Chapter
2), and the great regression at the end of the Oligocene, the
uplifted zone became submerged, because of the return of the
seawater from the epicontinental seas; the relative rise of
sea-level was naturally greater than the sinking of the ocean
floor.
This interpretation is also in another way in keeping with
the work of Van Andel and Bowin (36, p. 1288); they found
Pliocene and Miocene Foraminifera encrusted in manganese
nodules on the flank basalts. The Miocene Foraminifera date
the submergence as close to that end of the Oligocene regres-
sion as could well be demanded.
We now consider the dogma concerning red clay. Concern-
ing the present deep sea in the western North Atlantic, in parti-
cular, three independent evidences for shallow water in the
Eocene and Oligocene are dismissed with the remark that
they occur together with red clay (79). These evidences are:
1) Opaline sediments “formed as transgressive facies in nor-
mal marine continental shelf environments” are time equi-
valents of quite similar biogenic Eocene “horizons A and A”
deep sea cherts of the North Atlantic and Caribbean” (80).
2) “the Oligocene contains a remarkably persistent white
chalk formation . . . This chalk with Brarudosphaera . . . was
formerly thought to be indigenous to shallow water . . . Ap-
parently the bed indicates widespread condition of rapid de-
position, so that the calcium carbonate was not dissolved [?],
even in such deep water that the hed lies hetween “red” clays
(79, p. 420—421; italics ours).
3) Red clay is characteristic for great depth in the icy cold
deep water of Recent and Pleistocene time, although even by
this globally existing temperature condition, the upper limit
of red clay varies regionally from 3000 m to 5300 m depth