Greinar (Vísindafélag Íslendinga) - 01.01.1977, Blaðsíða 120

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N-America, on the basis of a permanent coastline, and this
is then suggested for the Burma-Indonesia-Australia and
New Zealand area. To this must in any case be added the
question, which land furnished the sediments for the Her-
cynian to Alpine chain from Burma to Australia? At the
ends we have old India and Australia on the west side of
the arcs, from which we eonclude that there was a now
subsided land mass all the way in between. We have already
seen in Chapter 4 that a 5000 km drift of India during the
Tertiary is unacceptable for other reasons, and the same
applies to Australia. In the present position of the land masses,
the Hercynian trend rhymes, but we could hardly have ex-
pected that after a Mesozoic and Tertiary more or less rotat-
ing drift of India and Australia from Africa.
Subsidence in the Indian Ocean during the Tertiary, most
likely in the Oligocene regression, is just as possible as in
the North Atlantic. We have assumed that a rapidly spreading
nanocrystalline state is the basis for such subsidence, and
the even thickness of shallow sea organic deposition shown
by (35) refers also to the Indian Ocean.
Asia furnished also sediments along a coast line from Borneo
via Celebes, Japan to Kamchatka, as is easily understood.
Concerning the coasts of Africa and eastern S-America, we
have more limited geophysical knowledge of Mesozoic accu-
mulations of sedimentary strips than in N-America. The mate-
rial available now to the author will not be discussed. Con-
cerning S-Africa, it is clear that continental Triassic and Jur-
assic drop from a Jurassic peneplain, now at an altitude of
2400 m, to a depth of 1800 m below sea-level in Natal (87,
p. 193) which is evidence, both of a great continental uplift,
and of a subsidence east of Natal.
Let us for a moment postulate, for the sake of argument,
that 150 My ago, America began to drift away from Africa.
Then, at opposite coasts of these continents there would, by
not too unfavourable drainage conditions, be formed the coastal
accumulations of Africa and America, first in a lane between