Arkell.1956.Jurassic..

INDOCHINA, HONG KONG, MALAYA
found in Spiti Shales facies in eastern Indonesia. Where the connecting
seaway ran, however, is unknown; for in the intervening tracts of Indo-
China and Borneo only Lias and more doubtful Middle Jurassic (with a
small and incomplete Kimeridgian exception in Sarawak) is known.
This led Grabau (1928, pp. 133, 250) to postulate a connexion across
Assam into the Bay of Bengal and thence via the Indian Ocean; a concept
criticized above. If it is a correct hypothesis that India moved northward
in the Tertiary orogeny, a continuous outcrop of marine Jurassics from
west Yunnan to the Gulf of Siam or Tonkin need not be sought, for
these regions previously would not have lain so far apart; the Himalayan
and Indonesian troughs could be disrupted parts of an originally almost
continuous geosyncline. Whether the requisite system of tear-faults
exists and, if so, where it runs, are problems for future field-work.
HONG KONG AND INDO-CHINA
Small patches of marine Lias are known at scattered points over this
area. At Hong Kong the Lower Sinemurian is represented by a Schlotheimiid
genus, Hongkongites (Grabau, 1928, p. 774, pi. ix; Davis, 1952,
pp. 77-84, and plate facing p. 32) (= Sulciferites ?), and at Na Cham in
Tonkin there are Cardinia beds, without ammonites but obviously
Hettangian or early Sinemurian (Mansuy, 1919).
In Indo-China (Fromaget, 1937), at Hun Nien, in the province of
Kwang Nam, Annam, marine beds yield a faunule of small pelecypods
and gastropods largely identical with species of the French Hettangian,
and an ammonite compared to [Waehneroceras ?] longipontinum (Oppel)
(Counillon, 1909). Gryphaea arcuata and Uptonia jamesoni are also
recorded from other places (Fromaget, 1952, p. 69). In the south, in
Cochin China, Upper Toarcian appears at Trian, about 30 miles NE.
of Saigon, developed as shales with Dumortieria lantenoisi (Mansuy,
1914). The photographs show this to be close to D. nicklesi Benecke, of
the uppermost Jurense Zone in Europe. At Chepon in Laos, on about
the latitude of Hue and midway between the sea and the Siamese frontier,
are red sandstones with occasional beds of limestone and shale in which
occur teeth of Lepidotus, Acrodus and Plesiosaurus, believed to be of
Upper Lias age. This formation is directly overlain by the Upper Cretaceous
(Senonian) (Hoffet & Le Maitre, 1939). In NE. Laos, in the Sam
Neua region, are shales containing some of the Upper Bathonian brachiopods
of the Namyau Beds of Burma and Yunnan (Mansuy, 1920).
MALAYA
No evidence for Jurassic beds has been found. An assemblage of
pelecypods and plants near Singapore, which Newton (1906) thought
possibly Middle Jurassic, has turned out to be pre-Rhaetian (Scrivenor,
1931, pp. 65-7).
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