TITLE:
Facies Analysis, Sedimentary Environment and Sequence Stratigraphy of the Carboniferous Deposits of Gachal Formation, Eastern Central Iran (Rahdar Section)
AUTHORS:
Mohammad Javad Javdan, Mohammad Nabi Gorgij, Javad Shahraki, Seyed Mahmood Pahlavan Hashemi, Seyed Mohsen Kalvandi, Seyed Mohammad Kalvandi, Eshagh Bandani
KEYWORDS:
Kalmard, Lower Carboniferous, Gachal Formation, Rahdar Section, Homoclinal, Paleothysis, Kaskaskia, Khan Group
JOURNAL NAME:
Open Journal of Geology,
Vol.5 No.9,
September
25,
2015
ABSTRACT: Early carboniferous
deposits of the Kalmard block, with various characteristics in different
outcrops, are recognized by Gachal Formation. Generally speaking, this
formation comprises of four different members (A, B, C and D), consisting of
carbonate and evaporative rocks. Gachal Formation is composed chiefly of 55
meters sandstone and limestone interbedded with shale. According to the
lithological and microscopic studies, Gachal Formation is deposited in beach,
semi-restricted and open lagoon, shoal and open marine environments. Vertical
changes of microfacies and the curve of its depth changes account for the high
thickness of the facies of shoal and bar sub-environments and the low thickness
of the facies of lagoon and open marine sub-environment as well. Gachal
Formation rocks in Rahdar section are deposited in a low-anglehomoclinal ramplocated in southern Paleothysis Ocean.
The carbonate-sandstone sequence inGachal
Formation in Rahdar section is composed of a depositional sequence separated
from each other by type 1 sequence boundaries. Deposits of this formation are
separated from lower deposits by type 2 sequence boundary and fromKhan Group by unconformity. The
sedimentary sequence identified in this formation points to the age of late
Visean, conforming to Kaskaskia IV. The erosional boundary between Gachal and
Khan Formations is relatively compatible with drop in sea level at Late
Kaskaskia global scale.