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in my field notes as a local variation of a Triassic Red Bed horizon, a doubtful opinion which I preferred not to publish earlier. Possibly they are of similar age and origin to those of Y'u-pi-lang, described by Saurin, but they differ in possessing a high dip of about 40° to the south-south-west.
It is now suggested that both ocurrences bear a close relationship in time to the Coal Measures of the Yunnan-i basin. (Lat. 25°26′ Long. 100°40′). I have always regardRelations with the Coal Measures of Yun- ed the latter as of Upper Triassic age, but it is only quite recently that confirmation of this view has been forthcoming. From Yunnan-i itself I obtained a small fauna which by its general facies and the affinities of its species led Dr. Cowper Reed to refer it to the Upper Trias and especially to the Carnian1. At Miaotsway, a short distance to the south and from beds somewhat higher in the succession, I found a very abundant fauna, regarding which Dr. Cowper Reed has written" If we adopt Krumbeck's recent classification of the Triassic Beds of the East Indies, it seems as if the Miaotsway Beds should be ascribed to the Lower Noric."2
Above these beds at Miaotsway follow the Coal Measures of the Yunnan-i basin and although continuous exposures were not obtained, there is no reason to suspect any break in the succession, so that it appears safe to regard the Coal Measures themselves as Upper Norian. A provisional list of the plant remains collected by myself at Miaotsway, based chiefly on determinations by Prof. Sir A. C. Seward, was published by Prof. B. Sahni in 1936. It contains the following forms:
Equisetites Sarrani (Zeill.)
It is stated that Pelourdea Zeilleri is no doubt identical with Zeiller's supposed Næggerathiopsis Hislopi from Tongking. These
1 Pal. Ind., N. S., Vol. X, No. 1, p. 244, .
plants from Yunnan were taken to Paris by Prof. Sahni, and thanks to the courtesy of Prof. Painvain of the École des Mines, compared with Zeiller's Tongking types with which they are stated to show unmistakable affinities, and none with the Indian Gondwana flora.1 This particular Tongking flora, formerly regarded as Rhætic. is now placed in the Norian. Indeed, the Miaotsway section furnishes additional proof that this change is correct.
In an earlier paper I have stated that the fossiliferous marine Trias of the Yunnan-i basin may be faulted against the Red Beds which follow them to the east2. The evidence for this consists entirely of changes of dip in isolated exposures across one particular traverse. On another occasion, somewhat further to the south, I was more inclined to regard the change as due to lateral variation, for reddish-purple shales identical with those of the Red Beds proper were found interstratified with the yellow and white marls and soft, white sandstones of the Upper Trias, before the latter gave way entirely to the Red Beds.
The Junction of the Fossiliferous Trias of Yunnan-i and the Red Beds.
Summarizing the evidence advanced in this chapter, it is concluded that the Red Beds in question cannot be older than the Upper Permian and are not younger than the Upper Trias. Attention may now be directed to the Red Beds in Szechuan to the north, Indo-China and Siam to the south, the Federated Shan States and Burma to the west, with a view to their comparison and correlation if this appears to be possible.
III. THE RED BEDS OF SURROUNDING REGIONS.
As the Cretaceous and Tertiary ages attributed to the Red Beds of Central Yunnan by K. Krejci-Graf and others are based on their likenesses in certain respects with such deposits in the neighbouring, northerly province of Szechuan, further consideration of the latter is warranted here, particularly as it is hoped to demonstrate that the real analogies lie for the most part with certain facies of the Triassic rocks which also occur there.
1 Journ. Ind. Bot. Soc., Vol. XV, No. 5, p. 328, .
The great Red Basin of Szechuan occupies an area of not less than 67,000 square miles, bounded, roughly, on the west by the frontier ranges of Eastern Tibet; on the northThe Red Basin of Szechuan and the work east and east by the Tapanshan and the of Y. T. Chao and T. K. ranges cut by the Yangtse in its gorges beHuang. (1931). tween Wushan in Szechuan and I'chang in Hupeh, and on the south by the high mountains about the borders of Hupeh, Kueichow and Yunnan with Szechuan (see Pl. I.). The basin itself is filled with sediments of both marine and continental origin, ranging in age from late Permian to Quaternary; the outer ranges display older rocks still. Y. T. Chao and T. K. Huang group the Red Beds of the Basin together as the Szechuan Series which is described as a thick series of prevailing red rocks, chiefly sandstones and clay shales, lying directly on a coal-bearing group of Jurassic age and overlain by Pliocene and Pleistocene gravels. Numerous open, symmetrical anticlines of considerable linear extension occur, in which the older formations-Jurassic, Triassic and Permian are sometimes found. Otherwise from the published descriptions, the writer's personal observations being confined to the edge of the south-western corner of the province, the surface is entirely covered by Red Beds. The Szechuan Series is divided into three parts. The lowest, or Ts'ienfuyen Formation, 200-400 metres (650-1,300 feet) thick, usually carries a basal conglomerate, followed by yellowish sandstones and shales in which fresh-water molluscs such as Corbicula and Cyrena have been found; in addition to this, fresh water limestones with Unio and Cyrena have been met with. This fauna, which is of a Wealdean type, dates the beds fairly accurately as Lower Cretaceous.1 The Middle Division or Kuangyüan Formation, is 1,000 to 1,400 metres (3,280 to 4,600 feet) thick, concordant on the former and mainly composed of red sandstones and red clay shales with minor bands of yellow sandstone. It is supposed to belong to the Middle Cretaceous though part of it may be of Upper Cretaceous age. Discordantly on the Middle Division follows the Upper or Ch'engts'iangyen Formation, about 500 metres (1,640 feet) thick and distinguished by its massive, coarse, soft red sandstones with intercalations of clay shale and the frequent occurrence of conglomerates or conglomeratic sandstones. Because of the pronounced physical break
1 Grabau, A. W.: "Stratigraphy of China," Vol. II, pp. 664-5.
separating the Lower and Middle Divisions from the Upper one, the age of the latter (the Ch'engts'iangyen Formation) is regarded as in all probability as Tertiary and it has been placed in the Eocene pending further discoveries.
Chao and Huang state that everywhere this Ch'engts'iangyen Formation is but slightly tilted, the dip being usually from 7° to 15°, whereas the Kuangyuan Formation possesses dips of 30°, 40° or even 70° with sharp anticlines and synclines locally. They add that nine-tenths of the entire area of the Red Basin is the domain of the Szechuan Series and that the middle portion (the Kuangyuan Formation) is the most widespread, indeed, it is possible to travel for days on end across its red clays and sandstones. The lowest portion, on the contrary, is of rather limited extent. These Red Beds weather into a soil which produces crops supporting not less than 50 millions of the Chinese people, and in so doing form a contrast with the Red Beds of Yunnan which are amongst the more thinly populated parts of that Province.1
Arnold Heim, as mentioned earlier (p. 524), divided the Szechuanese Red Beds into three parts-in descending order the Tshiating, Tshungking and Tseliutsin Series, reswhich have priority over pectively; names those of Chao and Huang. He found no proof of the angular unconformity which these authors had reported between the base of the Red Beds and the underlying Jurassic on the north-western margin of the basin. The " apparent conformity" between the two systems in its interior suggests to him rather a "perfect concordance," if not "a continuity of sedimentation." Moreover, to Heim the whole of the Red Beds are Cretaceous, with high dips even in their youngest exposures.
In their reports of the oil fields and salt deposits of Szechuan, H. C. T'an and C. Y. Lee also adopt a threefold division, using two of Heim's terms (with variant spellings) but
Arnold Heim's Classification. (1930).
H. C. T'an and
C. Y. Lee's Classifica- not within the same limits. A new and uption. (1933). permost Mengshan formation, 800 metres (2,600 feet) of brown sandstone and shale, with local conglomerates, is distinguished, but it is only of limited extent in the west. They give the aggregate thickness as 2,800 metres (9,200 feet). regard the whole as Cretaceous conformable with the underlying Jurassic,
1 Mem. Geol. Surv. China, Ser. A, No. IX, .
with the possibility that the lowest 100-400 metres (330-1,320 feet) of the Red Beds may be of Upper Jurassic age, while the transition from one subdivision to the next is said to be very gradual.1 In another paper T'an has stated that both Cretaceous and Jurassic have been folded and tilted together as a single unit. 2 This classification is adopted by Dr. G. B. Barbour in his commendable "Physiographic History of the Yangtze ", where a full account of the implications of these structural relations will be found.3
G. D. Louderback has proposed another classification of the Red Beds but has refrained from entering into the "game of nomenclature". Of his four arbitrary divisions, the lowest and the highest are the equivalents of Arnold Heim's Tseliutsin and Tshiating sections, while his divisions II and III are embraced in Heim's Tshungking Series, as is indicated in the following table, adapted from those given by Louderback himself and by Lee.4
G. D. Louderback's Classification. (1935).
Comparative Classifications of Formations in the Red Basin of
NOTE. Tshiating and Chiating (Kiating) are variants of the same name, as also are Tzeliutsin and Tsuliuching. Tshungking is usually written as Chungking. (100 metres 328 feet).
1 Bull. Geol. Surv. China, No. 22, . see also Bull. Geol. Soc. China, Vol. XIII, pp. 91-104, .
2 Bull. Geol. Soc. China, Vol. XVI, p. 399, [1936-7].
3 Mem. Geol. Surv. China, Ser. A, No. 14, pp. 23-37, .
▲ Bull. Dept. Geol. Sci., Univ. California, Vol. XXIII, No. 14, pp. 459-466, .