A Large Cenomanian Carbonate Ramp at the Transition Between Two Domains of the Zagros Sedimentary Basin, SW Iran: Cyclic Evolution and Its Eustatic and Tectonic Controls

Abstract

Carbonate sedimentation was spread widely on the southern margin of the Neo-Tethys Ocean in the mid-Cretaceous. New information from four exploration wells sheds light on the peculiarities of the Sarvak Formation (late Albian–Cenomanian) at the narrow transition between the Dezful Embayment and Coastal Fars in the southern Zagros. The solution of this task was necessary to understand whether the fragmentation of the Zagros Basin into domains affected the carbonate platform development. The methods included the analyses of carbonate microfacies, paleoecological patterns of foraminifera, and depositional environments. The results of this study show the existence of ten carbonate microfacies. Prevailing wackestones and packstones with a muddy matrix and absent carbonate buildups imply the development of a large carbonate ramp. Paleoecological interpretations based chiefly on foraminifers prove this model. For instance, the presence of oligosteginids signifies shallower parts of the platform, and the cooccurrence of planktonic foraminifera and oligosteginids suggests a deeper environment. The stratigraphical distribution of the established microfacies in the wells indicates three cycles in the evolution of this platform. The third of these cycles marked an abrupt deepening episode because it includes microfacies suggesting the relatively deeper environments. Three maximum flooding surfaces established in the study area are common to the Arabian plate. The discussion of the results suggests that the influence of the Kazerun fault on the carbonate ramp in the Cenomanian is uncertain. Neither eustatic nor tectonic factors of the carbonate platform development can be excluded. Conclusively, it appears that the studied Cenomanian carbonate ramp was integral at the transition between the Dezful Embayment and Coastal Fars.

1. Introduction

Tropical marine environments were vast in the beginning of the Late Cretaceous [1] and facilitated growth of large carbonate platforms (shelves and ramps) [2,3,4]. Particularly, such platforms extended broadly along the southern Neo-Tethyan margin [5,6,7]. The Zagros orogen, shaping presently the southwestern part of Iran, was a part of the above-mentioned margin in the late Mesozoic [5,8,9]. Carbonate complexes, which accumulated there in the beginning of the Late Cretaceous, have been well known for their hydrocarbon potential [10,11,12].

Significant attention was paid by previous researchers to the Sarvak Formation [13,14,15,16,17,18,19], which represents a large Cenomanian carbonate platform of the Zagros. However, many questions related to the evolution of this platform remain open. For instance, the Zagros consists of several domains [20,21,22]. One can expect differences in the evolution of the noted carbonate platform between these domains. If so, was there a single platform, fragmented platform, or chain of platforms? This is a knowledge gap, filling which is necessary for more precise paleogeographical reconstruction of the Zagros in the Cenomanian. To answer this question, the evolution of this platform at the transition between the different domains needs examination. Exploration wells drilled at the transition between two domains of the Zagros provide novel information of the Sarvak Formation, which seems to be highly important to address the question raised above.

The present study examines carbonates of the Sarvak Formation at the narrow transition between the Dezful Embayment and Coastal Fars in the southern Zagros. The information from these four wells seems to be important because two of them represent the Dezful Embayment, and two others represent the Coastal Fars, and all four are located at the transition between these two major domains of the southern Zagros. In other words, these wells are very suitable to focus the potential (dis)integrity of the Sarvak Formation at the noted transition, which is related to the above-mentioned research question. An analysis of microfacies sheds light on the depositional environment and records the cyclic development of a carbonate platform. The findings are also helpful to discuss the factors of eustasy and regional tectonic activity. More generally, this study extends the existing knowledge [13,14,15,16,17,18,19] via its focus on the area with the transitional position between two major domains.

2. Geological Setting

The Zagros fold–thrust belt is a tectonic unit in western, southwestern, and southern Iran (Figure 1). It developed in the Cenozoic on the former margin of the Arabian plate due to its collision with Iranian blocks [23,24]. In the Mesozoic, the Zagros was adjacent to the southern periphery of the Neo-Tethys Ocean [5,25], which can be considered as passive with caution due to a significant fault activity and other deformation [21,25,26]. Presently, the Zagros is divided by major faults into several tectonic blocks (domains) [20,21,22]. Two large domains are the Dezful Embayment and Coastal Fars, which are separated by the Kazerun fault (Figure 1).

Carbonates accumulated extensively on the southern margin of the Neo-Tethys Ocean in the late Albian–Cenomanian [5,6,7]. These deposits are known as the Sarvak Formation in the Zagros [19,27] and the other tectonic blocks of the Middle East [6,28,29]. Composition, thickness, and age of the Sarvak Formation vary across its distribution. Generally, it is dominated by Albian–Turonian limestones with a thickness measured in hundreds of meters. Shallow-water limestones represent a large carbonate platform that developed in a tropical, marginal sea of Arabia [5,6,7].

The study area (approximate coordinates are 30° N and 50° E) is situated in the southern part of the Zagros fold-and-thrust belt, at the transition between the Dezful Embayment and Coastal Fars (Figure 1). The Sarvak Formation is represented in exploration wells, which are located near the edges of the noted domains separated by a major Kazerun fault, which originated in the Paleozoic and reactivated in the late Mesozoic [21]. In the study area, the Sarvak Formation is a typically carbonate unit, with a thickness increasing eastwards from 369 m to 442.5 m. This formation conformably overlays the Kazhdumi Formation, and it is overlain disconformably by the Upper Cretaceous units (the Laffan Shale Member and the Ilam Formation of Coniacian age or the Gurpi Formation of Campanian age). A late Albian–Cenomanian age of the Sarvak Formation in the study area was defined by the regional biostratigraphy [30].

3. Materials and Methods

The material for the present study originates from four exploration wells drilled in the study area (Figure 1). The Sarvak Formation is present in all of them (Figure 2, Figure 3, Figure 4 and Figure 5). The identified biozones (sensu Wynd [30]) include the Trocholina-Orbitolina assemblage zone 21, the Praealveolina-algae assemblage zone 22, the “Favusella washitensis” occurrence zone 23, the Rudist debris zone 24, the Nezzazata-alveolinids assemblage zone 25, and the Oligostegina facies zone 26. These biozones confirm a late Albian–Cenomanian age.

Carbonate rocks of the Sarvak Formation are the focus of the sedimentological analysis. More than 700 thin sections were made from well cuttings. They were examined in the Paleontology Laboratory of the Exploration Management of National Iranian Oil Company (Iran). Carbonate microfacies and the general depositional model were established following some general principles proposed by Flügel [31] and Wilson [32]. Paleoecological interpretations of foraminifera and accompanying constituents also facilitated paleoenvironmental interpretations. The stratigraphical distribution of carbonate microfacies was established for each well. This permitted registering the cyclicity of carbonate platform development, outlining maximum flooding surfaces, and considering spatial differences of local carbonate successions. Importantly, maximum flooding surfaces were also useful for the correlation of the wells.

4. Results

4.1. Carbonate Microfacies

The bioclast mudstone–wackestone microfacies (MF1) is dominated by micrite (Figure 6A). The fossil content is very poor and dominated by miliolids, which are known to tolerate a broad range of salinity [31,33]. Their low diversity suggests shallow and saline water of the inner part of carbonate platforms [31,34]. Debris of invertebrate shells also occurs.

The bioclast algae wackestone–packstone microfacies (MF2) is dominated by micrite and grains in a micritic matrix (Figure 6B). Bioclasts are mainly represented by calcareous green algae. Bivalves and echinoids are also present (10–15%). Benthic foraminifera are relatively few and belong to the orders Miliolida and Textulariida. The abundance of dasycladacean green algae in this microfacies suggests shallow, warm marine environments [31,35,36]. The low diversity of benthic foraminifera is consistent with a shallow and restricted environment of lagoonal setting.

The benthic foraminifera–algae bioclast packstone microfacies (MF3) bears dasycladacean green algae and more diverse benthic foraminifera than MF2. The microfacies texture is grain-dominated (Figure 6C). Echinoid, bivalve, and gastropod debris is common. Benthic foraminifera belong mainly to imperforated tests of alveolinids, orbitolinids, Trocholina, Nezazzata, and miliolids. They indicate an inner platform setting.

The diverse benthic foraminifera bioclast wackestone–packstone microfacies (MF4) is mainly composed of tests of imperforate foraminifera and debris of invertebrate shells (Figure 6D). Benthic foraminifera belong to the genera Orbitolina, Alveolina, Praealveolina, Nezazzata, Dicyclina, Trocholina, Chrysalidina, Cuneolina, and miliolids. Broken shells of bivalves (rudists), echinoids, gastropods, and ostracods are scattered within the matrix. The cooccurrence of imperforated foraminiferal tests implies a lagoonal setting of the inner platform. Their diversity also suggests a better connection with open marine environments compared to MF3. The presence of broken invertebrates is a sign of a moderately high-energy environment adjacent to sand shoal.

The miliolid peloid packstone–grainstone microfacies (MF5) includes numerous miliolids and peloid grains (Figure 6E). Debris of mollusk shells (rudists and gastropods) and echinoids occurs in subordinate amounts. These are embraced by a sparry to micritic cement and show abrasion and sorting. These textural aspects are indicative of a high-energy environment of sand shoal. Other benthic foraminifera like Textularia also occur in this microfacies.

The rudist/coral floatstone–rudstone microfacies (MF6) is dominated by debris of rudist shells and coral colonies exceeding 2 mm in size (Figure 6F). High-energy conditions dominated but were not consistent enough to create a well-sorted texture. This microfacies can be linked to a shallow part of a middle platform.

The echinoid/rudist packstone microfacies (MF7) includes shell debris of marine invertebrates (echinoids and rudists) in the absence of imperforate tests of benthic foraminifera (Figure 6G). A micritic texture dominates, without any sorting and abrasion. These peculiarities imply deposition in a middle part of a carbonate platform and above the storm wave base level.

The bioclast oligosteginid packstone microfacies (MF8) is characterized by a significant amount of oligosteginids, which implies a middle part of a carbonate platform (Figure 6H). Bioclasts of echinoids and bivalves are finely fragmented and occur in subordinate amounts. In some samples, oligosteginids are sole components. In the absence of planktonic foraminifera, the environment is attributed to a shallow part of an outer ramp below the storm wave base level [31,37].

The bioclast planktonic foraminifera oligosteginid packstone microfacies (MF9) is distinguished by the appearance of planktonic foraminifera, which are absent in the other microfacies described above (Figure 6I). Planktonic foraminifera are Heterohelix, Muricohedbergella, Macroglobigerinelloides, and rare Favusella. Bioclasts of fine-grained shells of bivalves and echinoids are also present. This microfacies has a micritic matrix, and its fine-grained nature and abundance of matrix imply a low-energy environment below the storm wave base.

The bioclast planktonic foraminifera packstone microfacies (MF10) lacks oligosteginids (distinctly from MF8 and MF9) (Figure 6J). Planktonic foraminifera are chiefly biserial heterohelicids representing deeper parts of outer platforms, but not deeper than 100 m [38,39].

4.2. Evidence from Foraminiferal Paleoecology

Diverse benthic and planktonic foraminifera have been registered in the Sarvak Formation. The information on this group of microfossils is important for paleoenvironmental reconstruction.

Imperforate tests of benthic foraminifera dominate tropical, shallow, inner platforms [33,34,40,41,42,43,44]. Representatives of these benthic foraminifera in the studied sedimentary succession include Orbitolina, Cuneolina, Dictyoconous, Aleveolina, Praealveolina, Cisalveolina, Nezzazzata, Trocholina, Dicyclina, Chrysalidina, Textularia, and miliolids. Notably, alveolinids were found in carbonate lagoons and inner shelf platforms, often with high light penetration and oligotrophic conditions [33,43,45]. Their fusiform shapes imply adaptation to stable, shallow-water ecosystems [46]. Orbitolinids associated typically with shallow-water carbonate platforms, particularly in the mid-Cretaceous Tethyan realm [47,48]. These microfossils evolved in warm, tropical to subtropical marine settings, often in reefal or lagoonal environments with low-energy conditions. Trocholina, Nezazzata, Dicyclina, and Chrysalidina indicate warm, tropical marine environments, often in reef-associated or lagoonal settings with high carbonate production [35,43,46]. Oligosteginids were very adaptable and typical to shallow and inner neritic settings [49]. They also imply warm and eutrophic environments [50,51].

Hyaline tests of planktonic foraminifera and oligosteginids indicate a deeper, middle to outer part of carbonate platforms. Planktonic foraminifera belong mainly to biserial tests of Heterohelix, throchospiral tests with globular chambers of Muricohedbergella and Macroglobigerinelloides, and rarely ornamented tests of Favusella. The horizons of the Sarvak Formation with oligosteginids are attributed to shallower parts of the outer platform, while the cooccurrence of planktonic foraminifera and oligosteginids implies its deeper part. The noted taxa indicate a tropical, shallow, open-marine setting [41,52,53,54,55]. In the study area, the Heterohelix-bearing strata are inferred to record deposition in the deeper outer platform in the absence of oligosteginids.

4.3. Depositional Environments and Cycles

The analyses of microfacies and foraminifera imply that the Sarvak Formation in the study area represents a mid-Cretaceous carbonate ramp (Figure 7). The dominance of wackestones and packstones with a muddy matrix and the absence of carbonate buildups matches this interpretation well. Additionally, non-skeletal grains indicate an inner ramp setting, and their occurrence with benthic foraminifera evidences a high-energy, shoal environment. The peloidal shoal setting associates with warm tropical carbonate ramps [31,37]. All lines of evidence suggest an integrative depositional model of a carbonate ramp that existed in the study area in the late Albian–Cenomanian (Figure 7).

The stratigraphic distribution of the microfacies MF1 to MF10 can be established in each studied well. As we know the depositional environment related to each microfacies (see text above and Figure 7), it is possible to realize paleoenvironmental changes together with the deposition of the Sarvak Formation. The wells of the study area demonstrate that the stratigraphic distribution of the carbonate microfacies is not haphazard but reflects some regular patterns of paleoenvironmental changes, which can be grouped as true cycles. The base of each cycle is marked by the shallowest microfacies (relatively to lower and upper microfacies), whereas the appearance of the relatively deepest microfacies indicates a maximum flooding surface.

In well 1, three cycles can be established (Figure 2). The first of them starts at the bottom of the Sarvak Formation where MF1 is found. A deepening pattern is reflected by a shift to MF4, and MF7 marks the first maximum flooding surface. Then, depositional environments remained generally the same, but the appearance of MF1 marks the end of this cycle. Then, the second cycle starts, and it corresponds to the gradual shift from MF1 and MF2 to MF3 and MF4, after which the cycle culminates with MF7, which is understood as the second maximum flooding surface. Then, depositional environments remained more or less the same (MF6 is known from a lengthy interval), and the end of the cycle corresponds to a sharp shift to MF2. The third cycle started with an extraordinarily abrupt shift to MF9, after which there was a shallowing trend (MF8 to MF4) to the top of the Sarvak Formation capped by the erosional surface. The third maximum flooding surface can be found close to the beginning of this cycle, and it lies at the level of MF9. The third cycle ended with non-deposition and erosion after the deposition of the Sarvak Formation. It cannot be excluded that deposits marking the shallowing pattern of this cycle were partly eroded during the post-Sarvak hiatus.

A somewhat comparable cyclicity can be established in wells 2, 3, and 4 (Figure 3, Figure 4 and Figure 5). Three cycles are visible in all of them. However, the “geometry” of these cycles differs in detail due to local differences in carbonate accumulation and/or bottom topography. For instance, the first and second cycles demonstrate relatively longer deepening patterns in well 2 than in well 1 (Figure 2 and Figure 3). In wells 1 and 4, MF6 was documented on the very short intervals of the first cycle, and MF5, MF6, and MF7 were relatively common in the second cycle (Figure 2 and Figure 5). In contrast, well 2 demonstrates an opposite situation (Figure 3), and the first and second cycles are rather comparable in well 3 (Figure 4). Nonetheless, the relatively deep microfacies (MF7, MF8, MF9) prevailed in all four wells, where the beginning of the third cycle is abrupt (Figure 2, Figure 3, Figure 4 and Figure 5). Wells 3 and 4 are the only wells where MF10 was recorded (Figure 4 and Figure 5).

The three main sedimentation cycles outlined above can also be understood as sequences consisting of transgressive and highstand systems tracts (Figure 8), although such an interpretation is only provisional. Taking into account the presence of the same cycles in all considered wells (Figure 2, Figure 3, Figure 4 and Figure 5), it is supposed that these cycles were common for the entire Sarvak Formation of the study area, and, thus, the maximum flooding surfaces can be used for the correlation of these deposits (Figure 8). MF7 marks the intervals with the first and the second maximum flooding surfaces, and MF9/MF10 marks the interval with the third maximum flooding surface. Moreover, the third cycle reflects an abrupt deepening episode, and, thus, it differed essentially from the two other cycles. This episode started with a quick shift from MF2 to MF9 and ended when the sea regressed in the late Cenomanian (note a hiatus above the Sarvak Formation everywhere in the study area—Figure 2, Figure 3, Figure 4 and Figure 5).

The stratigraphic distribution of the established microfacies in the studied wells can potentially be used to establish the position of these wells relative to the carbonate ramp. However, a detailed comparison of the wells (Figure 8) did not permit making any definite conclusion. Although some regularities are visible at the particular stratigraphical intervals, they are not universal. This is why it would be very challenging to relate these wells to the orientation and the general geometry of the carbonate ramp.

5. Discussion

The outcomes of the present research should be interpreted in both global and regional aspects. First of all, the development of the established carbonate ramp matches well the extensive growth of carbonate platforms in the Cretaceous; the latter was among a few periods when the mean global carbonate platform area exceeded 1 × 10⁷ km² [3]. Cenomanian carbonate platforms and, particularly, ramps were reported previously from the Cauvery Basin in India [56], the Central Peloponnesus [57], the Eastern Pacific [58], the Hvar Island [59], Northern Spain [60,61], the Saharan Atlas [62,63], the Sinai Peninsula [64,65], and the Teutoburger Wald in Germany [66]. This can be understood so that the study area was embraced by the global episode of carbonate accumulation and carbonate platform growth.

The cyclic evolution of the carbonate ramp in the study area (Figure 8) can be explained by the interplay of the global sea-level (eustatic) changes and the regional tectonic activity. The established maximum flooding surfaces seem to be keys linking local and global events. The regional maximum flooding surfaces K110, K120, and K130 were common to the entire Arabian plate [6]. Their ages were justified by Simmons et al. [67] as the latest Albian, the earliest Cenomanian, and the late Cenomanian, respectively. The presence of the cycles with these surfaces in the entire region and their presence in the study area leads to the inference that three maximum flooding surfaces established in the wells (Figure 8) are local expressions of K110, K120, and K130. They can be used to infer eustatic rises proposed by Haq [68]. The abrupt deepening episode can be explained by a higher position of the global sea level in the second half of the Cenomanian [68]. This may be evidence of a clear eustatic control. However, one should note that the number of global sea-level rises was bigger than three during the time interval when the Sarvak Formation deposited [68]. In addition, these rises were comparably strong. Moreover, the position of the global sea level was not too much higher in the second half of the Cenomanian than in the first half of this stage [68], which makes the registered deepening episode enigmatic to certain degree.

Does the difference between the number of global sea-level rises and the number of regional maximum surfaces mean that the eustatic fluctuations do not explain the established cyclicity? On the one hand, the tectonic factor that modified local signatures of the global sea-level changes cannot be excluded (see below). On the other hand, one should take into account that the available eustatic reconstructions are not ideal, as well as that the accompanying stratigraphical developments are also not ideal; such uncertainties complicate the understanding of the factors of the Late Cretaceous sedimentation in the entire Arabian plate [69]. Notably, three sequences were registered in the Sarvak Formation in the other part of the Zagros Basin [70]. This implies that the sequences established in the study area (Figure 8) reflect a more general, regional pattern, i.e., typical to a significant portion of the Arabian margin, not only the study area.

The study area was located on the southern margin of the Neo-Tethys Ocean, and this margin experienced some tectonic activities in the Cretaceous [21,25,26]. Special attention should be paid to the Kazerun fault that crossed the study area (Figure 1). According to Sepehr and Cosgrove [21], this fault reactivated in the Cretaceous. The information from the studied wells does not permit us to establish any clear lithological difference between two wells representing the Dezful Embayment and two other wells representing the Coastal Fars. This is evidence against any strong influence of the Kazerun fault on the local carbonate deposition in the Cenomanian (indeed, this does not mean that this fault was inactive in the Cretaceous). There are, however, differences in the thicknesses of the proposed sequences (Figure 8). They differed by two times between the wells. Interestingly, the differences between the wells representing the Dezful Embayment and Coastal Fars are comparable to the differences between the wells within each of these domains. This means that either these differences cannot be explained by the activity of the Kazerun fault or this activity was related to highly peculiar motions of the tectonic blocks (e.g., with rotation and inclination components).

According to Piryaei et al. [70], there was a differential subsidence on the Arabian margin in the Albian–Cenomanian, and the generally passive tectonic regime prevailed. Esfandyari et al. [71] stressed significant changes in the development of a carbonate platform in the other part of the Zagros, but only in the second half of the Cenomanian. These lines of evidence imply that the regional tectonic activity was not strong enough to affect the carbonate ramp development in the study area. Nonetheless, the proposed differential subsidence [70] can explain the established variation of thickness between the wells (see above). Tectonic activity accelerated later [70,71], and this can explain temporal differences in the end of the Sarvak Formation accumulation [69]. In the study area, a reactivization of the Kazerun fault can be hypothesized after the accumulation of the Sarvak Formation.

Other tectonic mechanisms should be proposed, even if they are only hypothetical and cannot be proven by the outcomes of the present study. These mechanisms are dynamic topography [72,73,74,75,76] (despite complications in the understanding of the dynamic topography history of Arabia [77]) and changes in the regional lithospheric stress regime in the mid-Cretaceous [78]. Indeed, the influence of such mechanisms on the development of the considered carbonate ramp is highly hypothetical and requires further investigations. One should note that the carbonate platform on the Arabian margin of the Neo-Tethys Ocean was not homogeneous, and, particularly, intra-platform basins existed [19]. Such features can be attributed to the dynamic topography mechanisms. Navidtalab et al. [79] explained the development of intra-platform basins by fault activity and extension. It cannot be excluded that these particular tectonic phenomena were related to the action of more general dynamic topography mechanisms. Moreover, the latter can explain adequately the differential subsidence proposed for the Arabian margin [70]. From the studies of the other carbonate platforms, it is known that dynamic topography can be a significant factor of their evolution [80]. Another interesting observation is the absence of mid-Cenomanian hiatuses in the Sarvak Formation in the study area (Figure 8). Such hiatuses were recorded in some other areas, where this formation exists [19]. This can be explained tentatively by a relatively distant position of the study area from the interior parts of the entire carbonate ramp or by a local subsidence triggered by dynamic topography mechanisms.

It cannot be excluded that both the global sea-level changes and the regional tectonic activity (in the form of dynamic topography) controlled the cyclic evolution of the Cenomanian carbonate ramp in the study area, but the relative contribution of these factors and the exact mechanisms of their influence are yet to be clear. Moreover, changes in the accommodation space and dip angles of the ramp, as well as the dynamics of carbonate production, should be taken into account [19]. Most probably, the reconstructed carbonate ramp was a part of the much larger carbonate platform that embraced a significant part of the Arabian margin where the Sarvak Formation and its lateral analogues accumulated [6,19,69]. If so, some general regularities in the development of this larger platform could have local effects. The outcomes of the present study imply that the position of the study area at the narrow transition between two domains of the Zagros did not interrupt the local integrity of the Cenomanian carbonate ramp.

6. Conclusions

The present study of carbonates of the Sarvak Formation at the narrow transition between the Dezful Embayment and Coastal Fars in the southern Zagros permits making three general conclusions, as follows.

(1)

The established carbonate microfacies (often wackestones and packstones with a muddy matrix) and the patterns of foraminiferal paleoecology indicate the existence of the large carbonate ramp during the late Albian–Cenomanian;

(2)

According to the documented stratigraphic distribution of the carbonate microfacies, each of which correspond to a specific depositional environment, the carbonate ramp evolved cyclically, with three cycles with the maximum flooding surfaces corresponding to the K110, K120, and K130 surfaces of Arabia; the third cycle reflects an abrupt deepening episode in the second half of the Cenomanian;

(3)

The factors of the cyclic development of the carbonate ramp are unclear, but the influences of neither the global sea-level changes nor the regional tectonic activity can be excluded.

This study highlights the importance of locally focused investigations of large ancient carbonate platforms for the better comprehension of their development. The main limitation of the present work is that it employs only sedimentological and paleoecological information. This information is enough to realize the peculiarities of Cenomanian carbonate deposition at the transition between two domains of the southern Zagros, but geochemical data would extend some interpretations and justify stratigraphy. A solution of the related tasks is left for future investigations.

The perspectives for further studies are linked to possible improvements of the regional paleogeographical schemes showing peculiarities of the carbonate ramp in the particular, narrow time slices, as well as to detailed paleotectonic reconstructions of the Arabian margin of the Neo-Tethys Ocean and regarding dynamic topography and local signatures of general stress regimes. The other perspectives include investigations of the Sarvak Formation in the study area in terms of carbonate reservoir structure and properties. The related research projects can be linked to the solution of the tasks mentioned above. Briefly, the tasks can be summarized as follows: (1) improvement of paleogeographical knowledge of the Arabian margin, (2) dynamic topography developments, and (3) reservoir exploration in the study area.

Indeed, additional efforts are required to establish precise ages of the Sarvak Formation and its particular packages in all principal domains and the particular localities. This can lead to a reconsideration of the earlier proposed depositional models and the interpreted cycles/sequences. The present study focused on the entire Sarvak Formation, which is chiefly Cenomanian in age in the study area. However, Albian deposits are also present, and further research should confirm their age and explore the spatial distribution of these deposits in the southern Zagros.