فصلنامه پژوهش های چینه نگاری و رسوب شناسی
سال سی و نهم شماره 1 (پیاپی 90، بهار 1402)

The present study has been performed to evaluate the prospective effects of activity mining on the mineralogy of sediments in the Dar-e-Allo copper mine, south of Kerman. Sediments affected by Dar-e-Allo mine are divided into six sedimentary groups including: natural background sediments, sediments of waterways leading to the mine, sediments of the Sarmashk River, sediments under the waste rock dump, sediments containing secondary phases, Fe-Mg oxy-hydroxide sediments, and evaporative sediments. Mineralogical studies of sediments as an indicator to evaluate the environmental effects of mining are classified into five main groups including primary and unaltered, carbonate, clay, sulfate and oxide minerals. Sediments in the operational area of the Dar-e-Allo copper mine are associated with extreme mineralogical diversity. The sulphide minerals are the most important source of acid mine drainage and secondary minerals such as gypsum, starkeyite, copiapite, magnesiocopiapite and natrojarosite are the most important temporary reserves of potentially toxic elements (PTEs) and H+ ions. The dissolution of the mentioned minerals, especially during the initial flushing events in the wet season, cause a sharp increase in the acidity and concentration of PTEs in the surface runoff.

Of the most important characteristics of the Ranikothalia genus, as large benthic foraminifera, are the existence of ornamentation in the external part of the shell especially around the central umbilicus knob, marginal mesh channels (MMC) in the marginal chord, trabeculate system with channels, V-shape plate in the floor of chambers and accumulation of septum that differentiated this genus from Nummulites genus and placing it in the Palaeonummulitinae sub-family. The Ilerdian transgression near the P5 Zone (Pelagic P5) is a stratal key surface for the determination of the Paleocene-Eocene boundary in the neritic deposits. Ranikothalia nuttalli as an index species is used for recognition of the Paleocene–Eocene boundary in the Neo-Tethys shallow water successions. This species, in the Padagi section, resembling the Pakistan Indus Basin, accompanied with Miscellanea miscella, Discocyclina sp., Discocyclina sp., Assilina sp. that indicated SBZ5/6 and suggested lower Ilerdian (earliest Eocene) age.

The source rock characteristics (thickness, quantity and quality) can be varied both in the deposition of time and space. Currently, the distribution map of organic matter is estimated by simplified extrapolate methods using observed data on well location. There is a high degree of uncertainty as a result of using this method especially in the area with a lack of well data.  The aim of this study is to intreduce a novel tool in DionisosFlow software for three-dimensional (3D) simulation of the distribution of total organic carbon in a source rock. In this method, a stratigraphic modeling approach is used to mimic the production and preservation process of the organic-rich interval. The main parameters in this module will be bathymetry, sedimentation rate, primary production, carbon flux and oxygen condition of the sedimentary environment. In this study, we constructed an artificial model to investigate the efficiency of this process-based algorithm. Furthermore, the 3D simulation result of a real model is illustrated. This study indicates a close relationship between depositional conditions on the one hand and the production and preservation of organic matter on the other hand. Also, simulation results pinpoint which anoxic condition could be one of the main parameters in maintaining and distribution of organic matter.

The biostratigraphy of the marly-limestone Pabdeh Formation has been studied in a section located in the Interior Fars (folded Zagros). Five assemblage biozones of plankton foraminifera with Early Eocene to Late Eocene age were identified in the studied section. Biozone 1 with a thickness of two meters has been identified at the base of the studied succession and includes Morozovellavela scoensis and Morozovella conicotruncata species defining the Early Eocene age. Biozone 2 with a thickness of 59 meters is the Early Eocene in age and is associated with the first occurrence of Morozovella aragonensis at the base and the last occurrence of Chiloguembelina wilcoxensis at the top. Biozone 3 with a thickness of 66 meters is defined by the first occurrence of Globigerinatheka kugleri at the base and the occurrence of Guembelitrioides nuttalli at the top and represents the beginning of the part of the Middle Eocene. The presence of Orbulinoides beckmanni indicates the Middle Eocene for biozone 4 with a thickness 88 meters. Biozone 5 with a thickness of 163 meters indicates the Middle–Late Eocene for the top of studied succession according to the first and last occurrence of Hantkenina alabamensis.

Biostratigraphy, microfacies and depositional environments of the Upper Cretaceous deposits (Gurpi and Amiran formations) were carried out in the Gerdbisheh section. The Gurpi Formation predominantly consists of shales interbedded with some argillaceous limestone layers. This formation disconformably overlies the Sarvak Formation and gradually underlies the Amiran Formation. The Amiran Formation is represented by grey to greenish shales, siltstones and sandstone intercalations which underlay the informal siliciclastic-carbonate unit 1. Planktonic foraminiferal assemblages have led to the recognition of six zones that reveal the late Coniacian?–early Maastrichtian age for the Gurpi Formation. Radiolaria and scattered planktonic foraminifera are the two main fossil groups present in the Amiran Formation. Therefore, based on the precence of the index planktonic foraminfera and the stratigraphic position the early-middle? Maastrichtian age is proposed for the Amiran Formation. We determined two microfacies in the interval of the Gurpi Formation and three petrofacies in the Amiran Formation. According to the obtained data the Gurpi Formation was deposited in the basinal setting, whereas the Amiran Formation is deposited as submarine fans on the slope part of a carbonate shelf under the control of turbidity currents.

The subsurface section of the Sarvak Formation with a thickness of 455 m is located in the North-Dezful Embayment. The Sarvak Formation is underlain by the Ilam Formation with erosional discontinuity and is overlain probably by the Shale of the Kazhdumi Formation (due to the lack of drilling to the underlying boundary). The probable age of this formation is Albian–Turonian. Based on petrographic studies of 2111 thin sections from cutting, the dominant lithologies are limestones and dolomitic limestones. Facies analysis has led to the identification of nine microfacies in three facies belts of the lagoon, bioclastic shoal and shallow open marine. The gradual changes in microfacies, lack of calciturbidite, slump structure and absence of large reefs structure, confirm the ramp type-carbonate platform. Diagenetic processes consist of micritization, neomorphism, physical and chemical compactions and dissolution. These processes have changed the reservoir quality of the Sarvak Formation. The quality of the reservoir is carried out in the framework of sequence stratigraphy and the Sarvak Formation is divided into third depositional sequences and six system tracts, and the reservoir potential of each system tracts was calculated and the result have shown 6 reservoir zones, which transgressive systems tract (TST)from the second depositional sequence has the highest reservoir potential in this well.