Carbonate platform evolution of the Asmari Formation in the east of Dezful Embayment, Zagros Basin, SW Iran

https://doi.org/10.1016/j.jafrearsci.2021.104229Get rights and content

Highlights

  • Identify eight microfacies (MF.1–8) basinal deep water - lagoonal shallow water.

  • For Cyclostratigraphy in three oil fields with 7 positive and 5 negative breaks.

  • The Asmari platform evouloted at 6 stages: Ch (I,II,III), Aq (IV,V), Bu (VI).

Abstract

In this study, based on a multidisciplinary approach (biostratigraphy, cyclostratigraphy, and facies analysis), the Asmari carbonate successions were evaluated across two platform-to-basins transects including Parsi (Pr), Karanj (Kr), and Paranj (Prj) oil fields. In the biostratigraphy part, key large benthic foraminifera was used; which determined the Asmari carbonate Formation to the Chattian-Burdigalian in age. Facies analysis led to identifying eight microfacies (MF.1–8) arranged from basinal deep-water setting (MF.1) to lagoonal shallow-water to tidal zone (MF.8). In cyclostratigraphy, a total of seven positive breaks and five negative breaks related to 12 wells were recognized by cyclolog software, to identify and correlate coeval depositional packages across oil fields. These key breaks were calibrated with biostratigraphy dating and traced across studied oil fields. Finally, based on the combination of all extracted data, three carbonate platforms were distinguished evolved through the Chattian- Burdigalian. Chattian carbonate platform is composed of a high variety of carbonate producing (Stages I, II, and III), representing a fore-Stepping stacking pattern. Aquitanian Carbonate Platform is a soft-grained carbonate ramp with a low-angle gradient comprising two different Stages: IV and V. The Burdigalian platform (Stage VI) is composed of meters to decimetre–scale limestone (MF.6) rich in Borelis melo, discorbis, and small rotalids highlighting a shallow-water lagoon and has a uniform set throughout the study area.

Introduction

After the Eocene warming trend provided an optimum condition for thriving LBF, subsequent Oligocene–Miocene time interval experienced a global Greenhouse-to-Icehouse climatic transition (Perrin and Bosellini, 2012). At this period, carbonate platforms are extensive throughout the world; which, in some localities such as the Asmari Formation in Iran, acted as good hydrocarbon reservoirs (Pomar et al. (2014) and references therein). These carbonate deposits are accumulated worldwide in a spectrum of the depositional profile from the reef (Frost, 1981), fringing reef (Bosellini and Russo, 1992; Perrin and Francesca, 1994) to low-and high angle ramps (Allahkarampour Dill et al., 2018; Brandano et al., 2009a, 2009b); though they have recently been reinterpreted as ramp systems (Bassi and Nebelsick, 2010; Nebelsick et al., 2013; Pomar et al., 2014). Physical, chemical, and biological conditions induced through the Oligo-Miocene have caused dominant production of coral, coralline red algae, and large rotalids; predominantly piled up in the mesophotic zone of a carbonate platform (Allahkarampour Dill et al., 2018; Bassi and Nebelsick, 2010; Brandano et al., 2009a, 2009b; Pomar et al., 2012a, 2014, 2017; Shabafrooz et al., 2015). In this condition, coral buildups as depositional relief above the seafloor at the time of deposition, but with no barrier up to sea level (Pomar et al., 2014) have thrived at the lower Chattian and progressively shrunk towards the upper Chattian; in which discrete mounds (cluster reefs) have been built in the mesophotic zone (Pomar et al., 2014, 2017). In the northern flank of the Oligo-Miocene Asmari carbonate platform, however, both coalesced and isolated coral buildups have recently been documented in the mesophotic zone through the upper Chattian by Allahkarampour Dill et al. (2018). In the southern flank counterpart, in contrast, details of carbonate communities, and their distribution approach through time have poorly been discussed, which will be explained in this study.

The present study is two regional-scale platform-to-basin transects covering southern to south-eastern flanks of the Asmari basin; at which one of the most prolific hydrocarbon reservoirs in the Middle East was discovered. Some compressive regional-scale studies of the Asmari Formation have recently been conducted in terms of stratigraphy, sedimentary basin, and depositional architecture. Strontium isotope stratigraphy has been examined by Ehrenberg S.N., et al. (2007) who updated the age dating of the Asmari deposits. Latter, van Buchem et al. (2010) have investigated regional-scale sequence stratigraphy of the Asmari Formation from the high-Zagros to Dezful-Embayment. Shabafrooz et al. (2015) have studied carbonate architecture and sequence stratigraphy of the Asmari Formation using depositional geometries-i.e., clinoforms and build-ups- in three outcrop sections at the Izeh zone. More recently, a platform-to-basin transect of the Asmari Formation has been studied at the Izeh zone by Allahkarampour Dill et al. (2018); who reconstructed Asmari carbonate platform evolution through the Oligo-Miocene.

Such literature declares a list of comprehensive studies of the Asmari carbonate Formation in particular at outcropped sections placed at the northern flank; however detailed analysis of the taxonomic assemblages and facies architecture related to the south-southeast flank have received less attention. The main aims of this study are to analyze the vertical and lateral changing character of facies belts and depositional architecture, to recognize the interplay between type, distribution, and biodiversity of carbonate producing biota and their ambient condition in controlling carbonate platforms, and to reconstruct types of carbonate platform profile along southern and southeastern flanks of the Asmari intra-shelf basin in the context of a conceptual model; all these will provide valuable information about biodiversity and type of carbonate system during the Oligo-Miocene for better understanding of both regional and global correlation.

Finally, the Asmari Formation in the study area has been compared with the surface sections properly outcropped out at the northern flank of the Asmari intra-shelf Basin in the Izeh zone and High zagros provinces (Allahkarampour Dill et al., 2018; Shabafrooz et al., 2015; Rahmani et al., 2012; and van Buchem et al., 2010).

Section snippets

Geological setting and study area

The Zagros fold-and-thrust belt begins with an approximate length of about 2000 km and a width of 100–300 km from the southeastern Turkish-Armenian border and continues with a northwest-southeast trend to the Strait of Hormuz located in the southernmost part of Iran. As a Foreland Basin, initially, convergence activities of this topographic situation started from the end of the Cretaceous with the movement of the Arabian continent's plate towards the Iranian continental block and subsequently

Materials and methods

The present study consisting of two transects covers both southern and south-eastern flanks of the Asmari intra-shelf basin. These SW-NE and E-W trending transects comprise five adjacent oil fields namely Parsi (well no. 1, 11, 16, 18, 19, and 33), Karanj (well no. 31, 2, 9, and 14), Paranj (well no. 6), Mansourabad (well no. 11) and Aghajari (well no. 30) (Fig. 2).

For further understanding of depositional architecture and carbonate platform evolution through time, multidisciplinary tools such

Biostratigraphy

The biostratigraphy of the Asmari Formation was initially proposed by Thomas (Thomas, 1948), Wynd, 1965 primarily introduced a specifying biozonation (biozone no. 55, 56, 57, 58, 59, and 61). Later, it was revised by Adams and Bourgeois (1967); who examined a new biozonation scheme of the Asmari Formation especially in the Lurestan and Khuzestan regions, SW Iran. This biozonation using detailed data from 45 surface and 9 subsurface sections comprise 3 assemblage zones and 2 subzones, but

Facies analysis

In this part, all microscopic data extracted from thin sections (fabric, skeletal and non-skeletal components, sorting, and grain-size) were used for microfacies analysis. As a result, 8 microfacies-i.e., MF.1–8 were identified; which are based on Dunham and Embry and Klovan (1971) classification. From deeper to shallower settings, details of facies were described and interpreted in the following and summarized in Table 4.

  • MF1: Planktonic foraminifera wackestone to packstone

Description: This

Cyclostratigraphy

Cyclostratigraphy is a branch of stratigraphy evaluating astronomically forced pale climate change in the sedimentary record. It is typically focused on “Milankovitch cycles” in the sedimentary record, and the astronomical parameters induced these cycles (Berger, 1978; Berger et al., 1993; 2010). Therefore, such a tool applies for geologic correlation and the determination of geologic time (Fischer et al., 1988; Schwarzacher, 1993; Hilgen et al., 2004; Strasser et al., 2006; Hinnov and Hilgen,

Stratal architecture and distribution of facies association

The depositional profile of the Asmari carbonate Formation has been studied by many authors; most of which assigned this formation to a carbonate homoclinal ramp (Amirshahkarami, 2007; Seyrafian, 2006; Allahkarampour Dill, 2010; Vaziri-Moghaddam, 2005).

Most recently some integrated studies have been done on the Asmari Formation to reconstruct comprehensive depositional architecture and carbonate setting. van Buchem et al. (2010) focused on northern and southern flanks of the Asmari intra-shelf

Discussion

The present study includes the Asmari carbonate platform architecture in the south-southeast flanks of the Asmari intra-shelf basin, evolved in 6 distinct stages (Stage. I-VI). The literature of the Asmari carbonate platform studies are mostly focused on the northern flank of the intra-shelf basin (Vaziri-Moghaddam et al., 2006; Alahkarampour Dill et al., 2010; Vaziri-Moghaddam et al., 2010; Shabafrooz et al., 2015a, b); in which spectacular outcrop sections are exposed. Generally, all former

Conclusion

The Asmari carbonate platform was studied in two south and south-east-trending transects containing Aghajari, Karanj, Paranj, Parsi, and Mansourabad oil fields located in the Dezful Embayment. Carbonate platform architecture through Oligo-Miocene is the most important goal of this study; which was achieved by a combination of biostratigraphy, cyclostratigraphy, and facies analysis.

Biostratigraphy of carbonate successions is based on spatial and temporal distribution of key large benthic

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This paper was supported by the Department of Earth Sciences, Science & Research Branch, Islamic Azad University, Tehran, Iran, that we would like to thanks. We wish to thank the National Iranian South Oil Company (NISOC) for providing the data and for permission to publish this research.We are also very grateful for Dr. Nikfard's valuable guidance and assistance. Dr. Damien Delvaux, Editor-in-Chief of Journal of African Earth Science, sincerely is thanked for his highly valuable comments and

References (55)

  • L. Pomar et al.

    Carbonate ramp evolution during the late Oligocene (chattian), salento peninsula

    southern Italy: Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2014)
  • L. Pomar et al.

    Reef building and carbonate production modes in the west-central Tethys during the Cenozoic

    Mar. Petrol. Geol.

    (2017)
  • J. Romero et al.

    A model for the palaeoenvironmental distribution of larger foraminifera based on late Middle Eocene deposits on the margin of the South Pyrenean basin (NE Spain)

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2002)
  • K. Sarkarinejad et al.

    Thick-skinned and thin-skinned tectonics of the Zagros orogen, Iran: constraints from structural, microstructural, and kinematics analysis

    J. Asian Earth Sci.

    (2019)
  • M. Allahkarampour Dill et al.

    The Asmari Formation, north of the Gachsaran (Dill anticline), southwest Iran: facies analysis, depositional environments and sequence stratigraphy

    Carbonates Evaporites

    (2010)
  • M. Amirshahkarami

    Distribution of Miogypsinoides in the Zagros Basin, in southwest Iran: historical biology

    A Journal of Paleobiology

    (2008)
  • M. Amirshahkarami et al.

    Paleoenvironmental model and sequence stratigraphy of the Asmari Formation in southwest Iran

    Hist. Biol.

    (2007)
  • D. Bassi et al.

    Larger foraminifera from the upper Oligocene of the Venetian area

    North-East Italy: Paleontology

    (2007)
  • F.R. Bosellini et al.

    Stratigraphy and facies of an Oligocene fringing reef (castro limestone, salento peninsula, southern Italy)

    Facies

    (1992)
  • M. Brandano et al.

    Nutrients, sea level and tectonics: constraints for the facies architecture of a Miocene carbonate ramp in central Italy

    Terra. Nova

    (2002)
  • M. Brandano et al.

    Facies analysis and palaeoenvironmental interpretation of the late Oligocene attard member (lower coralline limestone formation)

    Malta: Sedimentology

    (2009)
  • M.W.N. Buxton et al.

    A standardized model for Tethyan Tertiary carbonate ramps

    J. Geol. Soc.

    (1989)
  • J.-M. Daniel et al.

    Asmari Reservoir Modeling Field Scale Study of Gachsaran, Final Report Part1: the International IOR Research Cooperation for Iranian Fields Joint Study Program

    (2008)
  • R.J. Dunham

    Classification of carbonate rocks according to depositional texture

  • S.N. Ehrenberg et al.

    Strontium isotope stratigraphy of the asmari formation (Oligocene - Lower miocene), SW Iran

    J. Petrol. Geol.

    (2007)
  • A. Embry et al.

    A late Devonian reef tract on northeastern Banks Island, NWT

    Bull. Can. Petrol. Geol.

    (1971)
  • E. Flügel

    Microfacies of Carbonate Rocks, Analysis, Interpretation and Application

    (2010)
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