Early Carboniferous siliciclastic-carbonates in east-central Iran versus coeval carbonates of north Iran: record of latest Tournaisian-early Visean tectonic events

摘要

Three stratigraphic sections of the Early Carboniferous Gachal Formation in the Kalmard area, central Iranudwere studied. The Gachal Formation shows alternation of siliciclastics and carbonates in repeated cyclic arrangements.udThe microfacies and depositional environment are described and reconstructed. Facies analyses indicate the presence ofudseven carbonate and one siliciclastic facies types, which are indicative of back-, inner- and middle-ramp settings. Audmixed siliciclastic-carbonate ramp setting is proposed for the depositional environment of the Gachal Formation. Thisudmixed lithology has only been reported from that central Iranian formation. The Mobarak Formation, coeval deposits ofudthe Gachal Formation, in Alborz (northern Iran) is mainly composed of carbonates. The facies analysis of the carbonateudportion of the Early Carboniferous Gachal Formation shows some resemblance with those of the Mobarak Formation,udeven though middle- and outer-ramp facies are more abundant in the Mobarak Formation. During the latest TournaisianearliestudVisean third-order, shallowing-upwards depositional sequences were recognized in the Gachal Formation in theudstudy area. Tectonic activity (fault movements) was the main reason for thickness variations of the Gachal Formationudmembers in these three studied section. Synsedimentary tectonic activity must have been responsible for the platformudrising, leading to the erosion that created the siliciclastic influx into the Carboniferous basin in the Kalmard area. Ourudresults show the importance of synsedimentary tectonics on the development of carbonate facies.