UPPER ORDOVICIAN BRACHIOPODS FROM KAZAKHSTAN 



17 



Conglomerate and 

 red sandstone 



MIDDLE - UPPER ORDOVICIAN 

 Anderken Formation 



Siltstone and 

 mudstone (Unit 6) 



Limestone 

 (Unit 5) 



Sandstone and 

 siltstone (Unit 4) 



I | Sandstone 



(Unit 2-3) 



Conglomerate, 

 polymict (Unit 1) 



Beke Formation 



Sandstoi 

 mudstone, graded 



| : x : : : : : :| Sandstone, siltstone and 



Fig. 4 Geological map showing distribution of the Middle and Upper Ordovician rocks and the positions of measured sections and fossil localities that 

 yielded brachiopods in the area between the Uzunbulak and Ashchisu Rivers, south-eastern Chu-Ili Range (after Nikitin 1972, modified). 



tabulate corals Lichenarial sp. and Amsassia sp., stromatoporoids, 

 and various trilobites and echinoderms. Locally between the 

 Kujandysai and Sarybulak rivers, and on both sides of the Ashchisu 

 River in the eastern part of outcrop area, carbonate build-ups disap- 

 pear and the unit comprises bedded limestone varying from biomicrite 

 to biosparite intercalating with siltstone and mudstone, with 

 brachiopods of the Parastrophina-Kellerella Association (Tables 4— 

 5, Samples 628, 8223, 8223a, 8223b). Brachiopods of this association 

 also occur in pockets of bioclastic limestone in the mud-mound core 

 and the overlying bedded limestone together with large spherical or 

 ellipsoidal ooids of radiaxial calcite up to 1 cm across (Samples 

 2538,8217,8219,8256). 



Unit 6. Siltstone and mudstone with up to 6 interlayers of bentonite 

 up to 0.3 m thick in the lower part, total about 50-60 m thick, 

 containing brachiopods of the Zhilgyzambonites-Foliomena Asso- 

 ciation (Samples 8231, 8251, 8255). Abundant trilobites are 

 Gramilatagnostus granulatus Kolobova, Sphaeragnostus sp., 

 Microparia speciosa Hawle & Corda, Hammatocnemis sp.. 

 Birmanites almatiensis (Chugaeva), Cyclopyge sp., Cybele weberi 

 Chugaeva and Ovalocephalus sp., and graptolites include 

 Dicranograptus nicholsoni, Diplograptus anderkenensis, 

 Glyptograptus trubinensis and Pseudoclimacograptus scharenbergi, 

 suggesting the Lower to Middle Caradoc Diplograptus midtidens 

 Biozone (Keller 1956). 



Locality 3. East side of Kopalysai River 



On the east side of the Kopalysai River (Fig. 1) the Anderken 

 Formation is about 160 m thick and rests unconformably on the 

 siliciclastic Llandeilo Beke Formation (Fig. 2). Detailed description 

 of this section was provided by Keller (1956: 26), who recognised 

 three units (Fig. 3): (1) bed of intercalating polymict conglomerate 



and coarse- to medium-grained sandstone up to 70 m thick with 

 bivalves, rare Ectenoglossa sorbidakensis (Sample 8223-1) and 

 numerous plant remains of Akdalaphyton caradoci; (2) intercalating 

 fine-grained sandstone and siltstone about 15-20 m thick with 

 brachiopods of the Tesikella Association (Sample 1 27), the trilobites 

 Duhmaspis levis anderkensis and Lonchodomas tecturmasi; and (3) 

 mudstones with some siltstones and fine-grained sandstones about 

 70-80 m thick with abundant brachiopods of the Mabella- 

 Sowerbyella Association (Sample 8228). The deposits overlying the 

 Anderken Formation are polymict pebbly conglomerates and 

 sandstones of the Dulankara Formation. 



Locality 4. Buldukbai-Akchoku Mountain 



On the west side of the River Kopalysai, the Anderken Formation 

 includes a large carbonate mud-mound which forms the top of 

 Buldukbai-Akchoku Mountain. The lower part of the formation is 

 exposed on the south-western slope of the mountain, north of an east- 

 west fault (Figs 1, 3, 5-7). It includes, in ascending order: 



Unit 1 . Medium- to fine-grained sandstone up to 120 m thick with 

 Ectenoglossa sorbidakensis. 



Unit 2. Dark green, bedded siltstones, about 14 m thick with a few 

 layers of fine grained sandstone 3-10 cm thick, containing Mabella 

 conferta and Shlyginia fragilis of the Sowerbyella-Mabella Asso- 

 ciation. 



Unit 3. Siltstones with nodules of algal limestone gradually chang- 

 ing into beds of nodular limestone with dasyclad algae towards the 

 top, 38 m thick in total. 



Unit 4. Nodular algal limestone intercalating with siltstone about 

 0.5-1.5 m thick, up to 22 m thick in total, with brachiopods of the 

 Acculina-Dulankarella Association (Sample 8231-40). 



