Brief characteristics of the section

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Figure 2
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Figure 3
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Figure 4
[4]  The section is located 90 km to the southwest of the Tabas (33o15' 25'' and 56o10' 14'' ) in the eastern limb of anticline; a core being exposed at the watershed of the Godar-e-Gachal Range stretching northeastward along the Kalmard fault (Figures 1 and 2). The core is composed of gypsum and limestone beds of the Gachal Formation. The upper part of the limestones (Bed D) contains scarce brachiopods, conodonts, and foraminifers of Early Carboniferous age [Afghanabati, 1977]. With parallel but distinct stratigraphic disconformity the Gachal Formation is overlain by the Khan Formation. The section lacks the entire Pennsylvanian Series of the Carboniferous and a part of or entire Asselian Stage of the Lower Permian (Figures 3 and 4). The following bed succession is observed (from the base upward):

[5]  Unit 1. Brown ferruginate, thick-bedded to massive sandstones and sandy dolomites with thin interbeds of lighter color grey biosparitic limestones; basal limestone conglobreccia lie with a sharp contact on Bed D of the Gachal Formation. Thickness 34.5 m.

[6]  Unit 2. Grey, locally brown, ferruginate thin- and medium-bedded limestones. Thickness 4 m.

[7]  Unit 3. Pale grey, brownish medium- and thick-bedded dolomitized limestones and massive sandy dolomites. Thickness 16.5 m.

[8]  Unit 4. Grey thin-bedded biodetrital limestones with abundant brachiopods. Thickness 4 m.

[9]  Unit 5. Brown medium- and thick-bedded dolomites; quartzitic sandstones at the base. Thickness 7.8 m.

[10]  Unit 6. White thick-bedded to massive quartzarenite with thin interbeds of biodetrital limestones (biomicrites, pelmicrites); fragments of crinoids and bryozoans in debris. Thickness 12.6 m.

[11]  Unit 7. Interbedding of grey and light-grey thin- and medium-bedded biodetrital limestones with abundant bryozoans, brachiopods, crinoids, and fusulinids. The latter occur throughout the unit but most frequently in the upper part. At the base a thin interbed is overcrowded by badly preserved tests of Pseudoendothyra sp. (sample KH7). Single forms of Pseudofusulina unidentifiable at species level (samples KH10, KH14, KH18) occur above. Farther upsection species of this genus increase in abundance, locally they overcrowd the rock. These are Pseudofusulina curteum Leven, P. karapetovi karapetovi Leven, P. karapetovi tezakensis Leven, P. licis Leven, P. insignis Leven, P. ex gr. pamirensis Leven, P. aff. perrara Leven, P. aff. gravis Leven, P. gachalensis n. sp., P. kalmardensis n. sp., Pseudofusulina sp. 1, 2, 3 and 4. In addition to Pseudofusulina, there are frequent Eoparafusulina tschernyschewi (Schellwien), E. regina Nie et Song, E. pamirensis Leven, E. cf. oblonga (Grozdilova et Lebedeva), and single Eoschubertella ex gr. obscura (Lee et Chen) and Palaeostaffella(?) sp. (samples KH20, KH22, KH23, KH24, KH24A, KH24D, KH25, and R). Thickness 48.5 m.

[12]  Beside fusulinids, R. V. Gorjunova found two bryozoan assemblages. The lower assemblage (samples KH2 and KH13) contains Goniocladia perillustris Gorjunova, Rhombotrypella darvasica Gorjunova, Mackinneyella ornamentata (Schulga-Nesterenko), Alternifenestella aff. absoluta (Gorjunova), Streblascopora marmionensis (Etheridge). The upper assemblage (samples KH16, KH18, KH22) is composed by Alternifenestella aff. megacapillaris (Sakagami); Thamniscus sp. nov.; Filites sp. nov., Hexagonella aff. recta Gorjunova, Fistulipora enodata Gorjunova, Ulrichotrypa aff. ramulosa Bassler, Streblascopora marmionensis (Etheridge), Filites aff. quasites (Trizna), Diploporaria sp. nov., Thamniscus sp., Tabulipora aff frugalis Trizna et Klaucen.

[13]  Unit 8. Light-brown massive dolomites and sandy dolomites. Thickness 20 m.

[14]  Unit 9. Red, red-brown medium- and coarse-bedded sandstones. Thickness 20 m.

[15]  Younger beds of the Khan Formation are missing in the section.


RJES

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