PLEISTOCENE DEPOSITS OE TUKFAN 



377 



place is taken by layers of dark carbonaceous clay, bog iron ore, and lig- 

 nite. Manifestly these layers are of snbaerial origin, or at least were 

 formed in very shallow water, such as that of the swamps of Seyistan 

 and Lop, or the flood-plains of the same regions. Vegetation was abun- 

 dant, as has been th^ case till recently. Even now the vegetation of the 

 plain of Turfan is more flourishing than that of the plain of the Lop 

 basin. In ancient times, when the lignite and carbonaceous clay of the 

 section were formed, much of the vegetation was probably a low, swampy 

 growth, but there were plenty of trees also. In and near the carbo- 

 naceous layers I found many pieces of fossil wood containing much iron. 

 The trunk shown in the 

 photograph (plate 35, 

 figure 2) was preserved 



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(17) 5 feet— Grav«I. 



(16) 6 feet — Solid white clay, weathering rellow and deep plok. 

 (15) 2 feet — White, marly quartz sand aod grit, wttb aggregations of 

 Iron ore and wltb a layer of gypsum at the base. 



FlGURE 14.- 



(14) 30 feet — Massive white clay, weathering yellow and pink, and dark 

 In places wltb carbonaceous matter. 



(13) 1 foot — Yellow eand. 



(12) 6 feet — Banded plok and yellow clay wrth carbonaceous and Iron- 



(11) 1 foot — Yellow 6and. (bearing layers. 



(10) 15 feet — Massive white clay, weathcrlne pink. 



(8) 4 feet — Dark carbonaceous clay with thin seama of coal. 

 (8) Vi foot— Llgnlle. 



(6) and (7) 8 feet— While clay full of llgnlle seams. Iron, and gypsum. 



(5) 3 feet — Dark carbonaceous clay. 



(4) 4 feet — Wblte and yellow claj wlih Iron ore and sand, suggesting 



reed beds, 

 (3) 4 feet — Dark carbonaceous clay, almost lignite al top. 



(2) 6 feet — Mnsslve white clav 



— Layers of carbonaceous clay and white clay concealed under 



intact for a length of 

 about 8 feet. It was a 

 foot in diameter and 

 was somewhat flattened. 

 Its preservation was so 

 perfect that the scars 

 where the branches had 

 been broken off were in- 

 tact. The interlacus- 

 trine strata of Turfan 

 reproduce the essential 

 features of the vegetal 

 beds of the Carbonifer- 

 ous jseriod. The section 

 given in figure 14 re- 

 sembles sections in the 

 Coal Measures of Penn- 

 sylvania. 



Apparently' on the advent of an interlacustrine or thesial epoch, the 

 lake of Turfan contracted, leaving a smooth plain. Streams from the 

 mountains — ^then much more than now — kept the plain moist. The 

 result was a luxuriant growth of vegetation, not only on the immediate 

 edge of the lake, but in large areas of swampy land round about. When 

 conditions were most favorable, plants grew so luxuriantly that thin beds 

 of lignite were formed. Under less favorable circumstances, the number of 

 plants diminished, more or less detritus was washed into the swamps, and 

 carbonaceous clays were formed. Sometimes the bogs produced iron ore ; 

 again, trees grew in the swamps or were washed in from the surrounding 



-Lake Deposits and Quaternary Coal Measures 

 at TatliJc Biilah. 



Southeast of the playa of Turfau. Same scale as tigures 

 5-10. 1 inch = 40 feet. 



