摘要
The study area is located in the east Tabas Block in Central Iran. Facies analysis of the Qal＇eh Dokhtar Formation（middle Callovian to late Oxfordian） was carried out on two stratigraphic sections and applied to depositional environment and sequence stratigraphy interpretation. This formation conformably overlies and underlies the marly-silty Baghamshah and the calcareous Esfandiar formations, respectively. Lateral and vertical facies changes documents low-to high energy environments, including tidal-flat, beach to intertidal, lagoon, barrier, and open-marine. According to these facies associations and absence of resedimentation deposits a depositional model of a mixed carbonate-siliciclastic ramp was proposed for the Qal＇eh Dokhtar Formation. Seven third-order depositional sequences were identified in each two measured stratigraphic sections. Transgressive systems tracts（TSTs） show deepening upward trends, i.e. shallow water beach to intertidal and lagoonal facies, while highstand systems tracts（HST） show shallowing upward trends in which deep water facies are overlain by shallow water facies. All sequence boundaries（except at the base of the stratigraphic column） are of the no erosional（SB2） types. We conclude eustatic rather than tectonic factors played a dominant role in controlling carbonate depositional environments in the study area.
The study area is located in the east Tabas Block in Central Iran. Facies analysis of the Qal＇eh Dokhtar Formation（middle Callovian to late Oxfordian） was carried out on two stratigraphic sections and applied to depositional environment and sequence stratigraphy interpretation. This formation conformably overlies and underlies the marly-silty Baghamshah and the calcareous Esfandiar formations, respectively. Lateral and vertical facies changes documents low-to high energy environments, including tidal-flat, beach to intertidal, lagoon, barrier, and open-marine. According to these facies associations and absence of resedimentation deposits a depositional model of a mixed carbonate-siliciclastic ramp was proposed for the Qal＇eh Dokhtar Formation. Seven third-order depositional sequences were identified in each two measured stratigraphic sections. Transgressive systems tracts（TSTs） show deepening upward trends, i.e. shallow water beach to intertidal and lagoonal facies, while highstand systems tracts（HST） show shallowing upward trends in which deep water facies are overlain by shallow water facies. All sequence boundaries（except at the base of the stratigraphic column） are of the no erosional（SB2） types. We conclude eustatic rather than tectonic factors played a dominant role in controlling carbonate depositional environments in the study area.
基金
financial support given to this study by the Department of Geology of Ferdowsi University of Mashhad, Iran (code 3/28001)
