Writers : Lasemi .Y & Mokhtarpour. H.A
Refference : Geosciences Scientific Quarterly Journal,No.:7,P.:46

Abstract :

The Permian sequence (Ruteh Formation) in the Bibi Shahrbano Area is composed of 142 meters of
dark fossiliferous limestone. Its lower contact is unconformable with the quartz arenite (Top Quartzite) of the Lalun Formation. Its upper contact with the Elika Formation is a distinct laterite horizon. The calcareous algae and benthic foraminifers indicate the Murghabian age for the Permian rocks in the study area.
Field and petrographic studies and microfacies analysis in the study area led to the recognition of three
sub- environments including the open marine, barrier, and lagoon- tidal flat.The environment of the Ruteh Formation is very similar to the present day carbonate environments.These rocks were deposited in an epicontinental platform (hom!clinal ramp),similar to the southern part of the present day Persian Gulf.
Vertical changes of microfacies represents a major regressive cycle, with 36 small scale shallowing upward cycles.This ma)or cycle(third- order cycle)should be the result of extensional movements, subsidence, and eustatic sea level changes causing slow transgression and faster regression. The small scale regressive cycles (parasequences) are the result of glacial activity leading to eustatic sea level changes (placioeustatic) or Milankovitch rhythms, causing fast transgression and gradual lowering of sea level.

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