C. The Alleged Existence of Devonian Red Beds in SouthWestern Szechuan and North-Central Yunnan. of Huili. In his Presidential Address to the Geological Society of China in 1929, the late Dr. V. K. Ting announced that the valley of Huili Chou, lying between the high mountain ranges Continental Devonian of the Lungtsaoshan and Taliangshan, on the west and east, respectively, in the extreme south-west of Szechuan, consists largely of red sandstones of Devonian age. He added, "Middle Devonian fossils have been found. by me in the region south of the river in precisely the same formation. A fragment of Leperditia found in the district itself assures me that the correlation is correct ".1 I have crossed the Lungtsaoshan and can confirm Ting's observation that it is built of rocks of Permian age and it is quite possible that in the Huili valley, there is another example of the protrusion of the older Palæozoic floor through younger rocks. That Devonian rocks do occur elsewhere in this manner is certain. On the Tali Fu-Yungpei T'ing route, after traversing a great thickness of Permian volcanic rocks and crossing Middle Devonian of the Yangtze at the Chingchiangkai ferry, fossi Chingchiangkai. liferous limestones occur from which I obtained a large collection of Middle Devonian corals, brachiopods and cephalopods. The limestones are followed by overlying Red Beds, the junction being marked by a conglomerate in which jasper and porphyrite pebbles are the commoner rocks; taking these to be derived from the Perrmian igneous, suite, I regarded the Red Beds themselves as late Permian or early Mesozoic.2 Continental Lower The continental Lower Devonian of Huili Chou has its counterpart in Eastern Yunnan where the upper part of the Silurian consist of sandstones with Modiolopsis, Lingula, Devonian of Eastern Leperditia and fish remains. 3 These beds show a progressive increase in fresh water conditions which culminated later in the continental deposits of the Lower Devonian from which Arthrostigma gracile Daws., and Yunnan. 1 Bull. Geol. Soc. China, Vol. VIII, No. 2, pp. 160-161, (1929). 2 Rec. Geol. Surv. Ind., Vol. LIV, Pt. 3, p. 325, (1923). Pal. Ind., N. S., Vol. X, Mem. No. 1, pp. 6-19, (1927). 3 Bull. Geol. Soc. China, Vol. XV, No. 1, p. 35, (1936). Bull. Geol. Soc. China, Vol. XVI, pp. 7-8, (1937). other plants have been described.1 These lower Devonian rocks are confined to quite restricted areas about Chü-ching Fu (Lat. 25° 32′ Long. 103° 47') and another city, Chanyi Chou, some 10 miles further north in the extreme east of Yunnan. In North-Western Yunnan, reaching from north of Tali Fu (Lat. 25° 40′ Long. 100° 10′) to Likiang Fu (Lat. 26° 53′: Long. 100° 14′); Prof. J. W. Gregory's from Chitsung (Lat. 27° 35': Long. 99° 34') Minchia Series of to Atuntzu (Lat. 28° 30': Long. 98° 53'), and Devonian Age. again, in the Mekong valley itself, north of Weihsi Ting (Lat. 27° 11': Long. 99° 16′), there occurs a series of purple, red and green sandstones, grits and shales, often associated with porphyries, basalts, diabases, tuffs, agglomerates and flows of dolerite, spilite and rhyolite, which Prof. Gregory termed the Minchia Series and which he believed to be of Upper Devonian age. I do not accept this classification in its entirety for the southern limits to which these rocks extend, the only ones with which I am acquainted, but the occurrence of Uncinulus procuboides Kayser var., in the neighbourhood of the Janu La, is regarded by Dr. Cowper Reed as proving the presence of Upper Devonian rocks there. In any case there appears to be nothing in common between the Minchia Series of Gregory and the continental Lower Devonian of Eastern Yunnan or of the Huili valley in Szechuan.2 Unfortunately Ting did not specify the locality of "the region south of the river", from which he obtained this particular Middle Devonian fauna, but as he was personally responsible for for the rich collections collections of the Geological Survey of Devonian of. Eastern V. K. Ting on the of Central Yunnan. China from the Middle lity this was the region he had in mind. to be settled until the proposed posthumous publication of his field notes takes place, a tribute to the memory of a great Chinese geologist which will undoubtedly lighten many obscure stratigraphical problems. At the same time, it is possible to prove that those geologists who read into Ting's remarks a presumption that the Middle Devonian fauna in question came from the Yangtze-Yunnan Fu area, and conclude therefrom that the Red Beds which cover almost the 1 Pal. Sinica, Ser. A, Vol. 1, Fasc. 2, [1927]. Pal. Sinica, Ser. A, Vol. 1, Fasc. 4, [1936]. 2 Phil. Trans. Ser. B, Vol. 213, pp. 220-222, 287-289, [1925], whole of it, are of Devonian age, are interpreting them in a way which he never intended. There can be no doubt that for some years Ting regarded the greater part of the Red Beds of Central Yunnan as of Triassic age, and further, that he impressed this view on his colleagues. For example, T. K. Huang has stated:-" In Central Yunnan the Liupakou Series [of the Permian] is wanting, the Triassic Red Beds coming directly upon the basaltic lava, according to V. K. Ting.”1 He also rejected the theory that any of the Red Beds of Yunnan are contemporaneous with the red, continental Cretaceous formations of Szechuan, or with the red Tertiary deposits of certain other provinces. In this case it is fortunate that his own words can be quoted. After referring to the fact that most writers on Szechuan fail to recognise any unconformity between the Jurassic coal measures and the overlying sandstones, he continues as follows:"In Yunnan the difficulties are greater because no sedimentary rocks younger than the Trias have been met with, except those of the Pliocene, the characteristic Red Beds [i.e., those of Szechuan] being absent.2 A few years later Ting adopted the view, in conjunction with Prof. A. W. Grabau, that the Red Beds in question are of Upper Permian age, a standpoint which he maintained at the Sixteenth Session of the International Geological Congress in Washington in 1933 (see p. 538). D. Further considerations on the Age of the Red Beds. Neoschwagerina craticulifera (Schwager) reported by Dr. Cowper Reed in my own collections from Tzumenlu, near Yunnan Fu3 was found again by Saurin at Tiefongngan, north The Horizon of the Underlying Permian of the city, where it occurs in limestone resting Limestone. on basaltic tuffs and where it is also associated with Fusulina brevicula Schwager and F. japonica Gumb. All these species are characteristic of the Lower Permian and in IndoChina their horizon follows directly above the transition beds between the Uralian and the Permian. But M. Saurin has also stated that Neoschwagerina Douvillei Ozawa occurs in the limestone cliffs above the pagoda of Heyaszeu, to the west of Yunnan Fu, and this is a 1 Mem. Geol. Surv. China, Ser. A, No. 10, p. 64, [1932]. 2 Bull. Geol. Soc. China, Vol. VIII, No. 2, p. 169, [1929]. form which is characteristic of the terminal horizons of the Permian in both Indo-China and Japan.1 If N. Douvillei really is a well founded zone fossil as thus indicated, the possibility of any part of the Red Beds above its horizon belonging to the Permian is precluded, because in many places the underlying limestones were deeply eroded, in others reduced to a peneplain and perhaps in extreme cases entirely removed, before the deposition of the Red Beds themselves commenced. In M. Saurin's opinion these events imply an emersion in Lower Triassic and perhaps in Middle Triassic times and he concludes that the folded Red Beds belong either to the Middle and Upper or only to the Upper Trias as far as the Carnian, while the horizontal red sandstones are of Norian-Rhætic age.2 4 The question arises, however, to what extent are the elaborate zoning schemes, adopted for the subdivision of the Anthracolithic of these parts of Asia and based on the vertical distribution of the Fusulinidæ, reliable. Evidence, in fact, is accumulating that the stratigraphic value of a particular species as a zone index fossil is to be regarded with suspicion. In the case of Indo-China, J. Gubler has demonstrated survivals across several so-called zones.3 He admits only two horizons in the Indo-Chinese Permian, characterised by Neoschwagerina craticulifera and N. multiseptata, respectively, and regards more detailed zoning and synchronisation as hazardous if not fantastic. From the Productus Limetone of the Hindu Kush, R. Furon has reported the co-existence of the supposed typical Lower and Upper Permian forms, N. craticulifera and Sumatrina annæ3. From the Lower Permian Maokou Limestone of Kwangsi, C. Li and W. Y. Chang obtained not only N. craticulifera, but, amongst other forms N. Douvillei, the identical species which Saurin believes proves the Upper Permian age of the Yunnan Fu rocks. T. K. Huang has stated that all the species of fusulinids quoted by himself as occurring in the Maokou fauna are assembled in a single horizon and cannot be adapted into any smaller subdivisions.7 Forms are thus included in the Lower Permian in this instance, which have 1 Op. cit., p. 449. 2 Ibid., p. 461. 3 Bull. Soc. géol. France, Vol. IV, 5th Ser., p. 443, [1934-35]. Mem. Soc. géol. France, Vol. XI, Fasc. 4, No. 26, p. 149, 156, [1935]. 5 Bull. Soc. géol. France, Vol. 4, 5th Ser., p. 70, [1934-35]. Bull. Geol. Soc. China, Vol. XV, p. 275, [1936]. Bull. Soc. géol. France, Vol. 4, 5th Ser., p. 446, [1934-35]. H been zoned individually from the top to the bottom of the whole system by other writers. Indeed, if we accept the views of the Geological Survey of China, limestones bearing this Neoschragerina craticulifera fauna, extensively developed in Eastern Yunnan and elsewhere, must be classified with the Maokou Limestone of SouthWestern Kueichow, and placed at the top of the Yangsinian, the lower of the two great divisions into which the Permian of Southern China is divided. Thus the occurrence of Neoschwagerina Douvillei in the limestones near Yunnan Fu would not appear to invalidate their Lower Permian age. The Red Beds and the Lopingian. Above the Yangsinian follows the Lopingian and in searching for evidence which may have a bearing on the problem of the lower limit of the Red Beds, its development in Eastern Yunnan, North-Western Kueichow and the extreme south-west of Szechuan is worthy of brief of brief attention. In these regions, according to T. K. Huang1 it is represented by the Liupakou Series of continental shales and sandstones with a thickness usually below 200 metres (650 feet). It invariably contains thin coal seams and carries the Gigantopteris flora. It generally rests on basaltic lava flows which in their turn overlie the Maokou Limestone with its Neoschwagerina craticulifera fauna, and which we have already seen underlies typical Red Beds in the Yunnan Fu neighbourhood. Following the coalbearing horizons there occurs a thick succession of red shales and sandstones, often lithologically inseparable from the Liupakou beds themselves, and from horizons about the middle of these Triassic pelecypods have been obtained in Kueichow. This generalised section of Huang's agrees with that given by Deprat for Eastern Yunnan, except that the latter placed his "Grès grossiers et psammites rouge-brune à niveau de charbon à Megalopteris nicotianafolia" in the lowest Trias, and with the further exception, that between the basalts and the underlying Lower Permian limestones there intervenes his thick series of sandstones, variegated marls and conglomerates. In Central Yunnan, however, west of the longitude of Yunnan Fu, as no trace of the Liupakou Series or of its associated coal seams and flora has been found either by myself or by any other geologist, it must be regarded as missing, unless the basic rocks or some part Mem. Geol. Surv. China, Ser. A, No. 10, p. 64, [1932]. |