Sequence Stratigraphy of Kazhdumi Formation at NW Gachsaran

In this research, the sequence stratigraphy of the Kazhdumi Formation was investigated at two stratigraphy sections on the northern limb of Lar Anticline and south limb of Khumi Anticline in the NE of Gachsaran township. Given the discerned facies and their vertical transformations, two 3rd degree sedimentary sequences were identified in the Kazhdumi Formation. At the northern limb section of Khami Formation, the TST of the 1st and 2nd sequences are designated by basin and outer ramp sub-environment facies. The HST of the 1st and 2nd sequences consists respectively of basin, outer, middle and inner ramps and of outer ramp. The TST of the 1st and 2nd sequences is formed of basin and outer ramp sub-environment facies and the HST of the 1st and 2nd sequences is formed of the outer ramp facies, all at the southern limb of Lar Formation. Notwithstanding the presence of a subtle lamination, planktonic organisms special to deep environment as with radiolarian, planktonic foraminifers and oligosteginids and also profusion of fine-grained clasts and alternation with marly and shaly limestones in the Kazhdumi Formation, the MFS is discernible on both sequences. The underlying boundary of the 1st sequence on both sections rests over the Dariyan Formation and Kazhdumi Formation boundary. Iron nodules at this boundary signifies a discontinuity (a sequential boundary of SB1 type). The overlying boundary of the 1st and sequence and the underlying and overlying boundaries of the 2nd sequence, given the dearth of evidence on retrogradation, is of SB2 type.