The Effect of Sea Level Change on Depositional Facies in Mozduran Formation, West of the Kopet-Dagh Basin

The Mozduran Formation in west of the Kopet-Dagh basin, NE Jajarm, is mainly composed of dolostone in top and base, and mudstone to grainstone limestones in the middle parts of Cheshme-Khan section. This formation in the Qezel-Tapeh2 well is composed of alternative limestone and shale layers. Based on the facies studies, four carbonate facies associations (open marine, barrier, lagoon and tidal flat) have been identified, including fifteen carbonate microfacies and two siliciclastic lithofacies. It is interpreted that the Mozduran Formation in this area were deposited in a homoclinal ramp of a carbonate platform. The sequence stratigraphy analysis led to distinguish five depositional sequences in the Cheshme-Khan section and four depositional sequences in the Qezel Tapeh2 well. The lower boundary of the 1st sequence (paleosol layar in the Cheshme-Khan section) and the upper boundary of the latest sequence (continental deposits) of both sections are a “type 1” sequence boundaries, but other boundaries are interpreted to be a “type 2” sequence boundaries. The relative sea-level curve of the study area comparing to the global sea-level curve, shows a relatively correlation and some differences can probably be related to regional tectonic setting of the Kopet-Dagh basin due to subsidence along the longitudinal faults and sediment loading.