Arkell.1956.Jurassic..

640 GENERAL SURVEY
Certainly the Bajocian and Bathonian faunas seem to be absent from the
Papuan geosyncline in central and SE. New Guinea, New Caledonia and
New Zealand, and also (with minor exceptions) in Japan, but there is
plenty of sediment in which they may yet be found, and the faunas are
present where these geosynclines meet the Tethys in Indonesia, which is
nearest to the transgressive Middle Bajocian of Western Australia. For
the rest of the vast length of these western Pacific geosynclines there is
no bordering continent with marine marginal Jurassics now above sea,
so it is impossible to say whether or not there was a transgression at this
time over adjoining continental land. At any rate none reached the
enclosed basin of east Australia.
On the eastern side of the Pacific the position is clear. The Middle
Bajocian transgression over vast areas in the Western Interior states and
Canada, already often mentioned, synchronizes perfectly in the Pacific
coast geosyncline with Middle Bajocian which is the thickest in the world.
No other interpretation is possible than that transgression over the Western
Interior was going on simultaneously with extremely rapid subsidence
in the Pacific coast geosyncline. An eleven-page analysis of North
American Jurassic stratigraphy in the state of knowledge in 1911 led Dacque
to the conclusion that it confirms Haug's 'law': but in fact it contradicts
it absolutely.
Similarly in the enormously thick geosynclinal series of the Caucasus,
the Toarcian and Bajocian are particularly well represented, whereas
according to Haug's 'law' they should be regressive there. The volcanic
developments in the southern Caucasus merely denote geosynclinal
mobility.
The single unit 'Middle Jurassic', used by Haug and Dacque, is, of
course, much too crude. The transgressions over various continental
areas within the Middle Jurassic were by no means simultaneous (as
indeed Haug realized: 1900, p. 701). For instance, in Western Australia
the transgression over lake beds and crystalline basement was Middle
Bajocian, but in Transbaikal, on the edge of Angaraland, the Lias sea was
there already, and although both Lower and Upper Bajocian are present,
Middle Bajocian ammonites have so far not been reported. In Madagascar,
East Africa and central Arabia the transgression over the African shield
was early Toarcian (Bouleiceras beds) and marine Bajocian merely follows
on. In Cutch, Tunisia, Egypt (Suez) and Burma, the transgression was
Bathonian, and probably late Bathonian. These various transgressions,
therefore, were not synchronous with an alleged regression in the geosynclines
'at the end of the Lias or beginning of the Bajocian'.
Regressions from continental margins being marked mainly by negative
evidence (absence of expected faunas, which may be due to various causes),
they are less satisfactory to deal with than transgressions. It is therefore
preferable, indeed usually unavoidable, to proceed from the transgressions,
and to enquire how they are integrated with the signs of orogenic movement
within the mobile belts (table 27, p. 634). Accordingly, from the evidence
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