Facies and Taphonomy

The ammonoid-bearing Famennian sequences of the Uralian-Kazakhstanian Region are highly condensed in western Kazakhstan, but become thicker to the north (Bashkortostan) and are particularly thick in central Kazakhstan.

M es

Genozone

Genozone

Disappearance of ..

clymeniids

Cheiloceras

Zones in the Rhenish Massif Becker & House, 2000; Becker et al., 2002

Genozones (Becker, 1993; Becker & House (2000)

Zones of the Rhenish Massif (Korn, 1981, 1986)

Zones of the Rhenish Massif (Korn, 1999; Kom& Ziegler, 2002)

Zones of the Urals and Kazakhstan

VI-F

Acutimitoceras (S.) prorsum

Acutimitoceras

prorsum

prorsum

VI-E

Cymaclymenia nigra

Cymaclymenia

Upper paradoxa

nigra

VI-D-2

'j| KEpiwocklum. £ applanata

Wocklumeria

sphaeroides

sphaeroides

VI-D-1

^ J| Wocklum. K sphaeroides

VI-C-2

Parawockumeria paradoxa

Parawocklumeria

Lower paradoxa

paradoxa

nucleus

VI-C-1

Kamptoclymenia endogona

endogona

VI-B

Balvia lens

Balvia

Upper subarmata

lens

VI-A

Kosmoclymenia

Linguaclymenia

Lower

parundulata

(M.) sublaevis

subarmata

sublaevis

frechi-corpulenta

V-C

Piriclymenia piriformis

Kalloclymenia

piriformis

piriformis

V-B

Ornatoclymenia ornata

Ornatoclymenia

ornata

ornata

ornata

V-A

Clymenia laevigata

Clymenia

acuticostata

laevigata

laevigata

IV-C

Protoxyclymenia (F.) serpentina

Pachyclymenia

serpentina*

serpentina*

serpentina

IV-B

Protoxyclymenia (P.) dunkeri

Protoxyclymenia

Upper annulata

dunkeri

dunkeri +

IV-A

Platyclymenia (P.) annulata

Prionoceras

Lower annulata

annulata

annulata

III-C

Prolobites delphinus

Prolobites

delphinus

delphinus

delphinus

III-B

Pseudoclymenia pseudogoniatites

Pseudoclymenia

sandberg.

pseudogon.

pseudogon.

III-A

Pernoceras dorsatum

Pernoceras

dorsatum

dorsatum

II

Dimeroceras mamilliferum

Dimeroceras

clymeniids j vi

Iiii

Appearance^ clymeniids^

Cheiloceras

Fig. 15.2 Correlation of the Famennian ammonoid zones proposed by various authors. The shaded area indicates the interval containing Famennian clymeniids in the Urals and Kazakhstan.

Facies And Zone Fossils

Fig. 15.3 Map showing five major areas with different Famennian ammonoid assemblages in the Uralian-Kazakhstanian Region. 1 - Western Kazakhstan, 2 - Chelyabinsk Region, 3 - Bashkortostan (these three within the South Urals), 4 - Karaganda Region, 5 - Semipalatinsk Region (these two in central Kazakhstan).

Fig. 15.3 Map showing five major areas with different Famennian ammonoid assemblages in the Uralian-Kazakhstanian Region. 1 - Western Kazakhstan, 2 - Chelyabinsk Region, 3 - Bashkortostan (these three within the South Urals), 4 - Karaganda Region, 5 - Semipalatinsk Region (these two in central Kazakhstan).

The richest Famennian ammonoid occurrences are found in western Kazakhstan in settings that are interpreted as the eastern margin of the Volga-Ural Carbonate Platform. They occur in thin, relatively deepwater carbonates with abundant conodonts and nautiloids, but with scarce foraminifers, bryozoans, brachiopods, and other benthic organisms (Fig. 15.4). Usually the ammonoids are found as large accumulations of non-oriented, unsorted, and excellently preserved shells. Abundances differ, however, in the stratigraphic succession. In most sections, the richest assemblages are found in the Middle Famennian, and lower part of the Upper Famennian. The number and diversity of ammonoids decreases noticeably up section. The microfacies are mostly mudstone/wackestone, and less frequently homogeneous packstone. Bioclasts include thin-shelled planktonic ostracodes (varying quantity), rare foraminifers (e.g., Parathurammina), and rare, rounded, clear fragments of pelmatozoans and camenids (Akhmetshina et al., 2004; Nikolaeva et al., 2004).

The Famennian of western Kazakhstan includes most Upper Famennian ammonoid zones in uninterrupted succession. The total thickness of the Famennian does not exceed 20 m. The condensed nature of the sequences and the character of the microfacies suggest deepwater sedimentation far from the source of clastic material. In contrast, in Bashkortostan and central Kazakhstan, the beds with ammonoids are separated by relatively thick beds of barren rocks (sections up to 150 m). In Bashkortostan, the shell-bearing rocks are carbonates, the source of which was the Volga-Urals Carbonate Platform, and in central Kazakhstan these are shales and siltstones, of clastics supplied by washout from the Kazakhstania Paleocontinent (for a full list of ammonoid localities and detailed description of ammonoid-bearing sections, see Nikolaeva and Bogoslovsky, 2005a).

Eastern margin of the Volga-Urals Carbonate Platform

Western Kazakhstan: Tengiz,

Karachaganak

Western Kazakhstan: Baktygarin, Kiya, Karadzhar

/ranip "omuls basin

A ttisS

-TSII V

Fig. 15.4 Reconstruction of the environmental settings in the Famennian basin of western Kazakhstan. Ammonoids are found only in the deep southeastern zone, where there is very little benthic fauna. This reconstruction is based on data from many sections and borings in the Peri-Caspian Region (Nikolaeva and Gibshman, in preparation). Mudmounds to the northwest of the zone with ammonoid-bearing sequences contain giant oil deposits.

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