Paper No. 126-8
The Kermanshah radiolarites belong to a vast siliceous complex characteristic of the Mesozoic rocks of the Tethys region. These siliceous sequences are associated either with ophiolitic outcrops, which allow us to date them, or to sedimentary sequences that were deposited in a long and narrow basin in an international zone, which benefited from the nutritional content upwelling driven by monsoons (Dercourt et al., 1993; Ricou and Marcoux, 1980; Ricou et al., 1977; Gharib and De Wever, 2010). The Ophiolite melange is well exposed in east of Kermanshah (SW Bisetun), west Iran and consists of spilitic diabase, spilitic trackybasalt, andesitic basalt, porphyric andesite, spilitic basalt, sepentinite, serppentinized harzburgite and gray limestone associated with green and red chert nodules and beds. In the present study, four stratigraphic sections of the ophiolite melange in southwest of Bisetun were studied and 40 chert samples were collected from different levels of sedimentary facies subjected to radiolarian extraction. These samples contain abundant Middle Jurassic to Early Cretaceous radiolarians. These radiolarian specimens indicate a Bathonian to Early Valanginian age for the ophiolite melange. Identified radiolarian zones include the Striatojaponocapsa conexa
Zone (JR5) (Middle Bathonian-Late Callovian), Kilinora spiralis
Zone (JR6) (Oxfordian), Hsuum maxwelli
Zone (JR7) (Kimmeridgian), and Pseudodictyomitra carpatica
Zone (KR1) (Tithonian-Early Valanginian) of Matsuoka (1995).
Dercourt, J., Ricou, L.E., Vrielynck, B., (Eds). (1993): Atlas Tethys paleoenvironmental maps. Gauthier-Villars, 260 pp, 14 maps.
Gharib, F. and De Wever, P. (2010): Radiolaires mesozoiques de la formation de Kermanshah (Iran). Comptes Rendus Palevol 9, 209-219.
Matsuoka, A. (1995): Jurassic and Lower Cretaceous radiolarian zonation in Japan and in the western Pacific. Island Arc 4, 140-153.
Ricou, L.E., Braud, J., Brunn, J.H. (1977): Le Zagros. Mém. Hors série Soc. geol. France.
Ricou, L.-E., Marcoux, J. (1980): Organisation générale et rôle structural des radiolarites et ophiolites le long du système alpino-méditerranéen. Bull. Soc. geol. France 1 (7 (22)), 1–14.