Writers : Javanbakht,Mohammad ;Supervisor:Mousaviharami,Mahboubi
Refference : M.Sc.Thesis _ Ferdowsi University,Mashhad
Publishing Year : 1384

Abstract :

The Sefidkuh Formation is oldest stratigraphic unit of the Aghdarband Group that is exposed in the Aghdarband erosional window in northeast Iran. 4 stratigraphic sections have measured in the study area.
The thickness of this unit in Sefidkuh, Aghdarband, Kalebast and Nazarkardeh are 312, 176, 150 and 76 meters respectively.
This formation in the Sefidkuh and Aghdarband sections are composed of 4 parts (2 parts pyroclstic and 2 part carbonate), while in Kalebast and Nazarkardeh sections it consists of one carbonate part. Petrography studies of 170 thin sections led to identification of 14 carbonate, and 2 pyroclastic lithofacies.
The lithofacies belt of A is composed of dolostone, mudstone, peloidal ooid packstone - grainstone, The lithofacies belt of B composed of bioclast peloid wackestone - packstone, peloid bioclast packstone, bioclast ooid packstone and Oncoid bioclast packstone - grainstone. The lithofacies C consists of bioclast peloid grainstone, ooid grainstone, intraclast ooid grainstone, ooid grainstone, bioclast intraclast grainstone, ooid bioclast grainstone. The lithofacies D includes bioclast packstone - wackestone and bioclast mudstone. The pyroclastic lithofacies has been divided 2 subfacies, including tuff and lapilli tuff. Based of lithofacies characteristics of the Sefidkuh Formation, the lithofacies belts A, B, C and D have been deposited in tidal-flat, lagoon, barrier and open marine environments respectively. It is interpreted that the carbonates of the Sefidkuh Formation have been deposited in a carbonate ramp.
The most important diagenetic processes operated in carbonate rocks are cementation, micritization, compaction, neomorphism, dolomitization and silicification. Thess processes affected the Sefidkuh Formation in three diagenetic environments including marine, meteoric and burial during three stages including eogene, mezogene and telogene.
Sea level changes during depositional of the Sefidkuh Formation resulted the formation of 4 large-scale sequence Sefidkuh, 3 sequences in Agdarband and 1 sequence in the Kalebast and Nazarkardeh sections, The upper and lower boundaries of the Sefidkuh super sequence is type I in the studied area.
Paleogeographic reconstruction of the study area indicated that these rocks may have been deposited during eleven stages during the Late Triassic (late Scytian - Early Anisisn). We hope these information can be used for a better understand of the structural conditions in the region as well as Iran.

Subject List : sedimentation history