Age Estimation of Hypogenic Caves in the Mozduran Formation (NE Iran): Implications for Karst Evolution

Mike Buchanan 2025

Picture: A Mozduran Cave (Courtesy of Mahmood Mherafrooz)

Abstract

Hypogenic caves within the Mozduran Formation of north-eastern Iran represent one of the earliest documented examples of deep-seated karst development in the region. This paper investigates their age, stratigraphic context, and geological significance. Based on stratigraphic correlation, carbonate platform evolution, and diagenetic processes, these caves are estimated to have formed during the Oxfordian–Kimmeridgian stages of the Late Jurassic (163.5–152.1 Ma). Numerical approximation places the average age of the caves at 157.8 Ma. Their evolution reflects hypogene dissolution by ascending fluids and subsequent paleoenvironmental modifications such as terra rossa infilling. Comparisons with global hypogenic karst systems highlight the broader significance of Iranian karst within Late Jurassic carbonate provinces.

Keywords: Hypogenic caves, Mozduran Formation, karst, Jurassic carbonates, Iran, palaeokarst, speleogenesis

1. Introduction

Karst systems are among the most dynamic geological environments, shaped by chemical dissolution, tectonic processes, and hydrological interactions. While epigenic caves formed by meteoric infiltration are widely studied, hypogenic caves remain comparatively under-researched in Iran despite their significance for regional palaeogeography and hydrogeology (Klimchouk, 2007).

Hypogenic caves are characterised by bottom-up development, where ascending fluids enriched with carbon dioxide, hydrogen sulphide, or thermal energy dissolve carbonate rocks (Palmer, 1991; Klimchouk, 2012). Their recognition within Iranian carbonate provinces, particularly the Mozduran Formation, provides a valuable opportunity to integrate local karst studies into global speleogenetic frameworks (Ford and Williams, 2007).

This study aims to:

1.           Establish the age of hypogenic caves in the Mozduran Formation.

2.           Relate their development to Late Jurassic carbonate platform evolution.

3.           Compare Iranian hypogenic caves with international analogues.

2. Geological Background

2.1 Regional Geological Setting

The Mozduran Formation crops out extensively in north-eastern Iran. It consists predominantly of shallow marine carbonates deposited on a broad carbonate platform during the Late Jurassic. The formation is underlain by the Kashafrud (Shemshak) Formation and overlain by the Shurijeh red clastic deposits, with regional equivalents including the Lar Limestone (Central Alborz) and the Esfandiar Limestone (Tabas region).

2.2 Stratigraphic Context

Biostratigraphic evidence constrains the Mozduran Formation to the Oxfordian–Kimmeridgian interval (163.5–152.1 Ma). Fossil assemblages of ammonites and benthic fauna confirm its placement within a warm, shallow marine depositional setting (Hypogenic Cave Formation Age Estimation for Mozduran Formation, 2025).

Formation             Stratigraphic Position        Absolute Age (Ma)              Equivalent Formations (Regional)

Shurijeh Formation            Overlying unit           ~150 Ma                           Red clastics (Kopeh Dagh)

Mozduran Formation         Study unit                  163.5–152.1                      Lar CaCO3  (Alborz), Esfandiar CaCO3 (Tabas)

Kashafrud Formation        Underlying unit           >163.5 Ma                      Shemshak Group equivalents

3. Methods

3.1 Stratigraphic Correlation

Age determination relies on correlation between cave-hosting strata and well-dated fossiliferous sequences.

3.2 Hypogenic Process Modelling

Cave formation mechanisms were inferred from lithological evidence, dissolution morphology, and analogues from international case studies (Klimchouk, 2007; Palmer, 1991).

3.3 Age Calculation

Numerical estimates use absolute stage boundaries. With the Oxfordian base at 163.5 Ma and Kimmeridgian top at 152.1 Ma, the cave system’s age is constrained between 150–163.5 Ma, averaging 157.8 Ma.

Figure 2. Simplified speleogenetic model of hypogenic cave formation in the Mozduran Formation (after Klimchouk, 2007).

 4. Results

4.1 Cave Age

The hypogenic caves of the Mozduran Formation are estimated to be ~157.8 Ma, ranking them among the oldest hypogenic karst systems in the Iranian plateau.

4.2 Geological Conditions of Formation

•             Extensive carbonate platform development.

•             Shallow marine environments with high carbonate productivity.

•             Tectonic stability favouring long-term hypogene dissolution.

4.3 Preservation Features

Caves exhibit evidence of:

•             Multiple phases of mineral deposition.

•             Terra rossa infilling and sedimentary occlusion.

•             Minimal erosional destruction due to tectonic stability.

 

Table 1. Estimated age range of Mozduran hypogenic caves.

 

A graph of a number of people AI-generated content may be incorrect.

  Geological Stage                Age (Ma)                Cave Formation Phase                     Notes

Oxfordian                              163.5–157.3         Initial hypogenic activity                Marine carbonate platform at peak

Kimmeridgian                       157.3–152.1         Active hypogenic dissolution          Terra rossa deposition begins

Average Age Estimate        157.8     -               Minimum cave age today ~150 Ma

5. Discussion

5.1 Hypogenic Speleogenesis in Iran

The Mozduran system illustrates classic hypogenic features: bottom-up enlargement, deep groundwater circulation, and chemical interaction with carbonates (Klimchouk, 2012).

5.2 Comparison with Global Analogues

Comparable hypogenic systems occur in:

•             The Carpathian Basin (Klimchouk, 2007).

•             The Guadalupe Mountains, USA (Palmer, 1991).

•             The Geneva Basin, Switzerland, where dolomitization influenced karst evolution (Makhloufi et                al., 2018).

5.3 Terra Rossa as a Paleoclimate Indicator

The development of terra rossa within Mozduran caves reflects prolonged subaerial weathering and residual soil accumulation, consistent with Mediterranean karst terrains (Martín-Pérez et al., 2010).

5.4 Implications for Iranian Karst Research

This study demonstrates that Iranian hypogenic caves:

•             Provide a deep-time perspective on karst evolution.

•             Serve as archives of paleoenvironmental change.

•             Should be integrated into global karst models (Ford and Williams, 2007).

6. Conclusions

•             Hypogenic caves in the Mozduran Formation formed between 163.5–152.1 Ma, averaging +- 157.8 Ma.

•             Their development was controlled by hypogene fluid circulation during Late Jurassic carbonate platform evolution.

•             Terra rossa deposits and sedimentary occlusion record paleoenvironmental transitions.

•             Iranian karst researchers can use Mozduran caves as analogues for global hypogenic speleogenesis.

 7. Recommendations

Future research should include:

•             Isotopic dating (U-Th, Sr isotopes).

•             Fluid inclusion studies.

•             Comparative petrographic analyses with Alborz and Tabas carbonate provinces.

 References

1.      Ford, D.C. and Williams, P. (2007) Karst Hydrogeology and Geomorphology. Chichester: Wiley.

2.      Hypogenic Cave Formation Age Estimation for Mozduran Formation (2025) Unpublished manuscript.

3.      Klimchouk, A. (2007) ‘Hypogene speleogenesis: hydrogeological and morphogenetic perspective’, Special Paper 1. Carlsbad: National Cave and Karst Research Institute.

4.      Klimchouk, A. (2012) ‘Speleogenesis, hypogene’, in White, W.B. and Culver, D.C. (eds.) Encyclopaedia of Caves. 2nd edn. Amsterdam: Academic Press, pp. 748–765.

5.      Makhloufi, Y., Rusillon, E., Brentini, M., et al. (2018) ‘Dolomitization of the Upper Jurassic carbonate rocks in the Geneva Basin, Switzerland and France’, Swiss Journal of Geosciences, 111, pp. 475–500. doi:10.1007/s00015-018-0311-x.

6.      Martín-Pérez, A., Salinas, R., De Waele, J., et al. (2010) ‘Terra rossa development in karst terrains: a Mediterranean example’, Geomorphology, 118(3–4), pp. 193–206.

7.      Palmer, A.N. (1991) ‘Origin and morphology of limestone caves’, Geological Society of America Bulletin, 103(1), pp. 1–21.

 

Comments

Post a Comment

Popular posts from this blog

Image
Histoplasma capsulatum - Histo - South Africa 2006 Histoplasma spores are prevalent in the atmosphere all the time. Our immune systems tolerance is derived by the local level of exposure. Within certain caves, typically low energy systems receding/dropping water table being the key to increased prevalence, the closer to the equator the more the prevalence becomes. Along with all other tropical diseases. Histoplasma capsulatum is an intelligent Dimorphic Fungus. This does not mean it can make tea. The intellect comes in the form of a transformation from a fungus into a yeast, as the spore settles and defuses through the alveoli membranes of the lung, into the blood stream. "Calcareous lesions" as reported radiologically historically, have been disproved by direct biopsy. The prevalence of reactive lymph nodes within the lungs specifically in the mediastinum is what we see as a "storm" on the x-ray image. As with the evolution of the development of your imm...
Read more
Image
  Groundwater Divides and Erosion of Terrestrial Horizons: A Critical Review of the Academic Paradigm - Mike Buchanan, 2022   Introduction The concept of groundwater divides has been a cornerstone of hydrogeology and broader hydrological sciences for decades. However, accumulating evidence challenges the traditional view of these divides as fixed and distinct boundaries. This paper critically examines the prevailing academic paradigm, focusing on the impact of tectonic activity, gravitational forces, and climatic erosion on terrestrial horizons. While the discussion is rooted in hydrogeology, the subject’s relevance spans across geoscientific disciplines due to its broader implications for terrestrial erosion processes, landscape evolution, and resource management. The Traditional Paradigm of Groundwater Divides Historically, the dominant model has operated under two main assumptions: Sharp and distinct groundwater divides – These are viewed as clear-cut ...
Read more
Image
  The Ethical Responsibilities of a Karstologist: A Comprehensive Overview Mike Buchanan 2023 A Philosophical Expression An ethical karstologist embodies a profound responsibility to the intricate karst landscapes they study, recognising these environments as vital ecosystems that sustain diverse life forms and human communities. Their duties extend beyond scientific inquiry; they must advocate for the preservation of these fragile ecosystems, balancing the pursuit of knowledge with a commitment to sustainability and conservation. By fostering a deep respect for the interconnectedness of all living things, an ethical karstologist seeks to illuminate the delicate relationship between human activity and nature, ensuring that their research contributes to a harmonious coexistence that honours the past, nurtures the present, and safeguards the future of karst landscapes. This integrated approach champions the stewardship of these unique environments, emphasizing that the integrit...
Read more