Arkell.1956.Jurassic..

INDONESIA 435
most part Dumortieriae (Krause, 1896, pi. xi) and of about the same age
as the deposit at Trian in Cochin China—an horizon conspicuous also in
northern Persia. Middle Jurassic is more doubtfully represented by
pelecypods and gastropods, including a Trigonia of Bajocian-Bathonian
aspect (Newton, 1903), and by Astarte-and-Corbula beds (Easton, 1904)
which suggest the Bathonian.
Upper Jurassic certainly occurs but is even more skimpily known:
reef limestones with an Upper Jurassic Lopha are recorded on the Sarawak
River (Newton, 1897), and Spath (Cutch, 1924, p. 16; 1933, pp. 825-6)
has identified a 'Subplanites of the schlosseri group' from Upper Sarawak;
this indicates Upper Kimeridgian. A fragmentary Perisphinctid figured
by Easton (1904, pi. xii) is not determinable. Land probably existed to
the north-west (Martin, 1907).
EASTERN INDONESIA
In the eastern part of the archipelago, as mentioned above, the Jurassicsystem
comes on in force and in the 'Banda Arc' there seems to have been
continuous deposition from Lower Trias or Permian to Lower Cretaceous.
The predominant facies in the geosyncline, from Hettangian to Tithonian,
is shales with nodules, resembling the Spiti Shales. In the Sula Islands
and Obi, to the north, the facies of some formations is more shallow-water,
neritic; and, so far as negative evidence can be relied on, deposition did
not begin until the Upper Lias or even Middle Jurassic. The deposits
on Misol are intermediate in character.
The supposed limits of the trough, indicated by broken lines in fig. 66,
were based largely on evidence from the Trias and from the physiography
of the present sea-bed. For the Jurassic alone, the conventional picture so
constructed is less satisfactory, for from Toarcian times onwards a trough
at least as important continued eastwards through New Guinea; and on
Buru (Wanner, 1922, p. 99) the earliest known beds are Oxfordian,
although this island lies in the middle of the trough. In any case, all
reconstructions are hazardous while we remain so ignorant of the stratigraphy
of Sumatra and Borneo. The small relic of Upper Kimeridgian
in Borneo is a warning of the vast amount of denudation that has taken
place, before and since the Cretaceous.
The emphasis usually laid on facies will be disregarded in the following
summary, which aims at bringing together the multitudes of scattered
records of ammonites from all parts of the eastern half of the archipelago
and sifting them critically. A complete but uncritical catalogue of Cephalopods
down to 1930 is available (Kruizinga, 1931), and a detailed account
of the stratigraphy island by island (Wanner, 1931). An attempt to
classify the occurrences by means of the belemnites has been made by
Stolley (1934), and the interesting Aucellae [Buchia] and Inocerami
have been studied respectively by Krumbeck (1934) and Wandel (1936).
Other mollusca are catalogued by Krijnen (1931) and other groups by
various authors in the same Festschrift. Of special interest is the pelecypod
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