مقالات رزومه منوچهر دریابنده

The Zagros sedimentary Basin has long been considered by geologists because of the presence of the hydrocarbon reservoirs and source rocks. Variable sedimentology and facies studies in this basin especially in Jurassic and Cretaceous successions have displayed their high potential as hydrocarbon source rocks. The Sargelu Formation is one of these successions that consist of abundant thin-shelled bivalves. Pelagic disarticulated bivalves concentrations in the deep marine sediments have been introduced as filaments that have recorded in variable middle Jurassic sediments around the world. In this study diversity and abundance of the Posidonia-dominated faceis have applied to differentiation of the sub-environments and reconstruction of the palaeoecological conditions of the Sargelu Formation. Because of the importance of the Sargelu sediments as source rocks, the achieved results are useful for reconstruction of the paleogeographical condition and hydrocarbon exploration in the Zagros Basin.  

The studied outcrops of the Sargelu Formation throughout Zagros fold-thrust belt including the Lorestan Zone consists of Tange-Havandeh, Kezi, Dowdan, Bizel, Tange-Mastan and Homajgah. To evaluation and determination of the sedimentary facies and sedimentary environment of the Sargelu sediments, a detailed sedimentary parameters include sediment/package/layers thickness, bedding boundaries (gradational, sharp, erosional), sedimentary structures, variable grain size, type and preservation mode of macrofossils (fragmented, whole, disarticulated, articulated) were recorded in the field. Based on microscopic asses on 500 thin-section, eight carbonate facies were identified in the Sargelu sediments in the studied area. Carbonate facies were classified/named according to Dunham (1962) classification. Identification of the facies/facies associations and their sedimentary environments were based on Wilson (1975) and Flugel (2010) scheme. 

Based on the microscopic and field analysis, eight facies have been identified in the Sargelu sediments that were related to two facies associations including basin to outer ramp of a distally steepened ramp system. Mud-dominated, fine-grained facies (calcareous shale, mudstone, pelagic bivalve wackestone/floatstone) including pelagic and hemi-pelagic deposits were deposited in the basin environment below SWB, characterized by long time of the low sedimentation rate, low water circulation and low oxygen level, displayed by high abundance of the organic material in this sediments (Pomar et al, 2012; Bayet-Goll et al, 2018; Sharafi et al, 2016, 2019). Outer ramp association consists of thin- to medium-bedded dark limestone including abundant Posidonia-dominated shell concentration with sharp-based, chaotic to preferentially parallel bed orientation of the skeletal elements and fining up-ward fabrics. These special features display periodically activity of the turbidity currents during deposition of the shell concentration and higher sedimentation rate and relatively favorable environmental conditions (with respect to the oxygen and nutrients) for the benthic communities, displayed by abundance bioturbation in these sediments.

Facies analysis of Sargelu Formation exposed in Lorestan Zone led to identification of two facies associations, representing basin to outer ramp of a distally steepened ramp system. Basin deposits in central Lorestan Zone include pelagic and hemi-pelagic deposits, displayed by mud-dominated, fine-grained facies. These sediments were deposited in an anoxic to dysoxic, relatively deep, sea-floor environment as revealed by the presence of: a) organic-rich shales and limestones, b) undisrupted lamination in most facies, c) absence benthic fauna. In contrast, Posidonia pelagic bivalves are interpreted as the result of the proliferation of this bivalve during periods of favorable environmental conditions on the sea floor. Thin to medium beds of graded wackestone/packstone to rudstone/floatstone and accumulations of thin shells of Posidonia pelagic bivalves indicate sporadic reworking of the sea floor by turbidity currents. Disarticulation, fragmentation, and reorientation of Posidonia pelagic bivalves can be indicative of reworking, by turbidity currents which periodically interrupted periods of lower-energy suspension sedimentation.

Sargelu and Garau formations are significant geological units in the Zagros, which are known for having the most important unconventional hydrocarbon resources in Iran. This study aimed to evaluate the hydrocarbon generation potential of two formations by analyzing 15 oil-shale samples collected from the Gashun-G and Pirbadush sections along the Qolyan River in the Qalikuh area, Lorestan. The analysis method used was Rock-Eval pyrolysis. To determine the scatter pattern of heavy elements, a total of 15 samples of river sediments and water were analyzed using ICP-MS. The average values for total organic carbon (TOC) and most hydrocarbon production indicators in Garau oil shales exceed the values observed in Sargelu oil shales. Based on the findings of the elemental analysis and pollution index calculations conducted on sediments, it can be seen that Sargelu shows a higher presence of heavy elements, a higher contamination factor (CF) and average pollution load index (PLI) compared to Garau samples. This difference can be attributed to the physical and chemical characteristics of the sediments. Conversely, Garau samples show a higher average Contamination Degree (CD) in its water, which may be attributed to environmental factors such as temperature and pH of water. The results of the statistical analysis demonstrate a wide range of heavy element formation factors within the sediments and waterways of the Garau route. As a result, despite the lack of human activity in this area, in addition to the amount of organic matter in the oil-shale, the geo-genic activity causes natural environmental pollution that is influenced by various factors, including oxidation-reduction potential, reactive processes, type of bedrock, clay minerals, sediment texture and environmental conditions.

Facies analysis of Garau Formation exposed in Lurestan Basin, High Zagros, folded belt Zagros led to indentification of three facies associations, representing basin plain, turbidite floor fan to outer ramp of a distally steepened ramp system. Basin plain deposits in central Lorestan Basin include plagic and hemi-plagic and turbidity deposits were developed in southern part of the Lorestan area. Analysis of depositional environment and facies of the Garau Formation reflect a three stage evolution model: 1) Early stage is represented by ramp drowning and basin plain expansion in an anoxic to dysoxic, low energy conditions with high productivity; 2) The activation of turbidity currents in the basin floor. These intervals are coincided with Leupoldina bloom and Oceanic Anoxic Event 1a (OAE1a). The middle part of the Garau Fm. is interpreted as fine-grained pelagic turbidites on base of their flat shape, sharp base, transitional top, Buma sequence and composition, which are composed mainly of intercalation of gravity flows and pelagic/hemipelagic deposits. The relative influence of sea level falls may result in an increase in sharp activation of turbidity currents and deposition of floor fans. 3) Stage 3 is represented by the recovery in the effectiveness of carbonate factory, favoured by the progressive shallowing of the depositional system and an increase in the abundance of pelagic foraminifers. These deposits reflect the shutdown of the turbidity and subordinate mass flows of the feeder system in the mainland and drowning of calciturbidites stage 2, likely as the result of a relative sea-level rise.

Qalikouh area is located 35 km southwest of Aligudarz city, Lorestan province, SW of Iran. The area is located in the central part of the Zagros Geological Zone. The oil shales of the area are located in the Upper Triassic and Lower Jurassic of Sargalu and Garau Formations. The Sargalu Formation contains a series of shale, carbonate and clays. Garau Formation includes oil shale horizons with different thicknesses, ammonite shales and black cherty layer. In order to investigate the enrichment ratio and relationship between elements and organic matter, 53 samples of oil shale from Garau and Sargalu formations were selected. The samples were analyzed by XRD, XRF, ICP-MS and Rock-Eval analyzer. Data processing was performed using factor analysis, fractal modeling, stepwise factor analysis and principal component analysis. The data show that Sargalu Formation with average TOC = 13.27% and Garau Formation with average TOC = 18.13%, have high content of organic matter in central and NW of the area. Cconcentration-number fractal modeling showed that the Co, Mo, Ni, Pb and U have significant anomalies. The stepwise factor analysis (SFA) method showed a significant correlation between the anomalous elements and TOC. Geochemical maps showed that the anomalies are located for Co and Pb in the center and SE, for Mo, Ni in the NW and center, for V and REE in the NW, and for U in central part of the area.

The carbonate Sargelu Formation (Middle Jurassic) in the Lorestan area mainly consists of black calcareous shales and thin- to thick-bedded limestones with remarkable organic material. Integrated binary diagrams of trace elements and stable isotopes such as Na-Mn, Sr-Na, Sr/Na-Mn and petrography, SEM and CL suggest an original low Mg calcite  (LMC) composition of the carbonate Sargelu Formation. Deep-sea sedimentation of the Sargelu Formation and its outer ramp to basin depositional settings are consistent with the formation and preservation of the LMC carbonate sediments. Binary diagrams of 1000Sr/Ca-Mn and δ18O-Mn as well as the presence of the framboidal and cubic pyrites, organic material and pseudocement infilling the bivalves display a predominant anoxic to the sub-oxic condition of the sedimentary substrate of the Sargelu Basin and marine and burial diagenetic effects in a closed to the semi-closed diagenetic system. The high content of the Mn of the studied sediments supports the anoxic condition in the sedimentary substrate as this condition facilitates incorporating Mn within calcite composition. Greenhouse condition in the Middle Jurassic period, which led to the stratification of the seawater of the Sargelu Basin and as a function of low water circulation, poor ventilation and formation of the anoxic condition, caused this high-temperature degree.

Qalikouh anticline is located 35 km southwest of Aligudarz city, Lorestan province, SW of Iran. The area is located in the high structural zone of Zagros. The oil shales of the areas are located in the Middle Jurassic and Lower Triassic of Sargelu and Garu Formations. The Sargelu Formation contains a series of shale, carbonate, oil shale, and clays. Garau Formation includes oil shale horizons with different thicknesses, ammonite shales, and black cherty layer. The shales of these two formations in the high Zagros region have formed oil shale reserves due to their richness in organic matter (OM), kerogen type is I and II, and relatively low thermal maturity at the beginning of the oil window. This study focuses on the effect of geochemical processes on the enrichment of trace elements and their interaction with organic matter in Qalikouh oil shale. analysis was performed by XRF, XRD, ICP-Ms, and Rock-Eval methods and Statistical significance were analyzed. The results of this study indicated the high enrichment of elements Cd, Mo, Ag, U, Cs. The correlation between immobilized and mobile oxides, organic matter, formed minerals, and other factors were tested. These tests revealed that the enrichment of trace elements is affected by classical, biological, and autogenic materials. Elements U, V, Cd are related to the organic and autogenic matter. Elements Ca, Si, P is of biological origin, and elements Ag, Ti are of classical origin.