20 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



Ordovician 



SSUYEN FORMATION : 



1. Moderately thick-bedded, gray and light-gray limestone in 

 layers 10 to 20 cm thick, with several irregular edgewise conglom- 

 erate and thin dolomitic limestone beds at certain horizons. 



Fauna. — Occasionally fragments of cephalopods {Amienocera^) 

 and gastropods occur. 



2. Moderately thick-bedded, light-gray arenaceous, dolomitic 

 limestones, in layers 5 to 20 cm thick, 60 m (196.8 feet). 



Total thickness of Ssuyen formation, 280 m (918.4 feet). 



WUTING FORMATION : 



Moderately thick-bedded, gray to dark limestone, with a few edge- 

 wise conglomerates in layers 10 to 20 cm thick, 160 m (524.8 feet). 



Fauna. — Traces of annelid borings. 



The Wuting occurs on the eastern slope of the 128-meter hill and at 

 the western end of Kan-tao-tzu Island. It rests apparently con- 

 formably on the Pingchou, and thus far I have not found the Santao 

 or any Lower Chazyan formation in this region. 



The Ssuyen and Wuting formations also outcrop in the five iso- 

 lated hills that stretch between Wan-chia-tung and Hsi-tien-chia-tun, 

 near Kan-tao-tzu Island. The lithologic characters and geologic 

 relations are the same as on Kan-tao-tzu Island. Only a few un- 

 identifiable fragments of Armenoceras were found in these isolated 

 hills. 



PECHILI DISTRICT 



Except for comparatively small areas at Wu-hu-tsui, Chin-chia- 

 cheng-tzu, and on Tschang-hsing-tao, most of the Pechili district is 

 occupied by rocks belonging to the Sinian series. The Cambrian 

 strata are finely developed in the vicinity of Chin-chia-cheng-tzu and 

 in the northeastern part of Tschang-hsing-tao, while the Ordovician 

 beds are confined to the area surrounding the Wu-hu-tsui coal field. 



WU-HU-TSUI SUBDISTRICT 



Surrounding the Wu-hu-tsui coal field, except on its northern 

 flank, Ordovician rocks make up the Ma, San-leng, Tai-tzu, and Kan- 

 tien hills. Since three rather large faults are present in this area, 

 it is necessary to present a composite and somewhat diagrammatic 

 section. (PI. 6.) 



Ordovician 

 Ssuyen formation : 



1. Moderately thick-bedded, gray to light-gray limestone, in layers 

 5 to 20 cm thick, with thin edgewise conglomerates and dolomitic 

 limestones, 100 m (328 feet). 



