Aretz et al_2011.pdf - ORBi - Université de Liège

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Kölner Forum Geol. Paläont., 19 (2011)
M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.)
Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011
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Early Jurassic corals of the Pamir Mountains - a new fauna of transition
between the Triassic and Jurassic
Galina K. MELNIKOVA 1 & Ewa RONIEWICZ 2
1Institute of Geology, Tajik Academy of Sciences, Ajni 267, 734063 Dushanbe, Tajik Respublic; mgk-
36@mail.ru
2 Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland;
eron@twarda.pan.pl
Early Jurassic corals are known in the SE Pamir Mountains beginning in the Hettangian/Sinemurian
(Fig. 1). In the Pamirian Jurassic sequences, two structural zones with differing facies development can be
distinguished: the south-western Ghurumdy zone, and the north-eastern Mynhadjir zone. Strata in both
zones were deposited in the same southeastern Pamirian sedimentary basin, on two sides of an inner, Istyk
Uplift (DRONOV & MELNIKOVA 1987) attaining considerable thicknesses.
Jurassic sedimentation began on both sides of the uplift by deposition of two suites of transgressive
conglomerates discordantly overlying Permo-Triassic sequences: the Darbazatash suite on the south and
the northern Kizylbeless suite. In both zones, sedimentation was followed by deposition of carbonate suites
provided with the same names as the zones: Ghurumdy suite and Mynhadjir suite. They are composed of
limestones with diverse lithologies, in the Ghurumdy suite, with a Hettangian-Sinemurian age indicated by
ammonites of the Schlotheimiidae. The lower part of Mynhadjir suite is considered to be of the Hettangian-
Sinemurian age as well. The above suites are covered by suites Sedek and Zormynhadjir, composed of
black, well striated limestones.
Series Stage Structural Zones
Middle
Jurassic
Lower
Jurassic
Aa
T
P
S
H
Mynhadjir zone
at NE
300-900m
Zormynhadjir
suite
corals
Mynhadjir suite
corals
Ghurumdy zone
at SW
560-1275m
Sedek suite
corals
Ghurumdy suite
corals
Kizylbeless suite Darbazatash suite
Fig. 1: Distribution of Early Jurassic corals in the SE Pamirs
In the lower Ghurumdy sub-suite, a well diversified coral fauna is known: the solitary forms
Archaeosmilia, Cylismilia, phaceloid genera, Archaeosmiliopsis, Prodonacosmilia, Intersmilia, Proaplophyllia and
lamellate colonial forms Eocomoseris (MELNIKOVA 1975, 1989, MELNIKOVA & RONIEWICZ 1976; MELNIKOVA et
al. 1993). In the coeval lower part of the Mynhadjir suite, Cylismilia has been found.
In the both suites, the upper sequences contain organo-detritic limestones and fine-grained oolitic
limestones, and are considered to be of the Sinemurian age. In the upper Ghurumdy sub-suite, phaceloid
corals, Pachysmilia and Stylosmilia are present (MELNIKOVA 1989). Different ecological types of corals,
massive colonial forms, are known in the upper Mynhadjir sub-suite, mentioned in DRONOV & MELNIKOVA
(1987).
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