Writers : Yahia Sheibani, Vesal; supervisor:R. Moussavi Harami, A. Mahboobi; advisor: M. Nagafi
Refference : M.Sc.Thesis _ Ferdowsi university, Mashhad
Publishing Year : 1381

Abstract :

There are some separate outcrops of limestones in South Mashhad (Binalooi mountains) most of which are observeable in the north of Aman-abad village. Four stratigraphic sections were measured and their thickness varies from 30.05 to 84.58k meters.
The cretaceous rocks are composed of limestones and siliciclastics. Limestone in the studied area are mainly fine to medium grain with skeletal and non-skeletal grains.
A few interbedded sandstones and conglomerates are present in the carbonate interval.
The peresence of large amounts of orbitolina, specialty Iraqia simplex species, indicates that they are Aptian in age the carbonate interval overlies the sandstones and conglomeratic units which are probably equivalent to Shurigeh (Neocomian) in thc . Kopet- Dagh Basin. These rocks are dissected by several normal faults Pctrographic studies of 105 thin sections showed that the carbonate rocks in this area consists of four carbonate and two siliciclastic lithofacies.carbonated lithofacies consists of 15 sublithofacies which are deposited in a shallow platform of a carbonate ramp. These sublithofacies are composed of fossiliferous grainstone, well sorted oolitic grainstone, intraclastic grainstone with bioclast, peiloidal and bioclastic grainstone, intraclastic packstone, bioclastic wackestone packstone، orhitolina packstone, mudstone-wackestone, caIci mudstone, bioclastic ,which are deposited in open marine, shoal lagoon and beach environments. Siliciclastic lithofacies include conglomerate and
sandstone (Arkose) which are deposited in a continental fluvial environment Petrographic studies also showed ، that diagenetic processes which are acted up or cretaceOUS carbonates consists of compaction,cementation, micritization, replacement silicification), neomorphism, formation of stylolites and fractures. These processes are
operated in diagcncti environmcnts such as marine phreatic, meteoric phreatic, burial and uplift.
21 samples were analyzed for carbon of oxygen isotopes. In addition 17 samples were. analyzed for trace elemental ( Mn ، Fe, Sn, Na, Mg, and Ca The amount of oxygen isotopes in the limestones range between -11.191 to -2.145 PDF and the amount of carbon isotopes range between 0.218 to 4.328 PDB. These variation ,reveals a meteoric diagenetic environment. Decreasing trend in the value of oxygen mounts of Fe and Mn, as well as decreasing of Na and Si isotopes with increasing the also indicated the meteoric diagenesis environment too. The calculated for the ambieni 1 and geochemical studies !أ water, that calcite was deposited, is about 26°C. Petrographi .also showed that the primary mineral? composition of these carbonate rocks were calcite Sequence stnatigraphic studies in this area show that there two depositional sequences DS ( DS2) are present in the Baz-Howz section whereas there is only one depositional( sequence is present in the other measured sections which are bounded with crosional boundaries(SB 1) .each sequence begins with lithofacies which mdicates the
. transgression of the sea and makes shallow parascquences after still standing of the sea paleogeographic of the Binalood area during the Aptian has been reconstructed and interpreted.

Subject List : Depositional environment