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Mid Holocene environmental and climatic change in Iran.

Authors:
Environment, ecology, landscape and subsistence


Mahew Jones, Morteza Djamali, Lora Stevens,
Vanessa Heyvaert, Hajar Askari, Dariush Noorollahi
and Lloyd Weeks
Introduction
       




      
    
     
      
  
      
       
       
       
     


        


c.
      
      
      
        





c.
et al
       
       

       
   et al  





 et al.     


   et
al
       



       
     

      




   

et al

       
        
       
     
      et al
       
      



M. Jones, M. Djamali, L. Stevens,V. Heyvaert, H. Askari, D. Noorollahi and L. Weeks








     



Climate and environment in Iran today
       
     

      


    
      
        
      
    
     

     
     
       
      

        
    
 et al.   
 
    
Figure 2.1. Long-term Holocene climate shifts driven by changes in insolation (A, summer insolation at 30°N; Berger and
Loutre 1991). Records shown are from Eski Acigol, Turkey (B; Roberts  2001), Zeribar, Iran (C; Stevens  2006) and
Qunf Cave, Oman (D; Fleitmann  2003). The fourth millennium BC is highlighted.
2. Mid-Holocene environmental and climatic change in Iran 
et al



  



 
  
et al

 




       
 Artemisia     
    
      

      


      

Evidence of Holocene climate and
environmental change from Iran
Lake records

        
 
      
     et al  
et al.
 
        
c.   

       

et al



     
      
      
     
    
  




    
       

et al
      
     
   et al  
     



et al.

et al
       
       



et al.




    
    
       

c.

       
    


et al

      
       
et
al        
   


      
 et al   et al  
et al  






et al.
     

        

M. Jones, M. Djamali, L. Stevens,V. Heyvaert, H. Askari, D. Noorollahi and L. Weeks


et al.  



        
       





Geomorphology and tectonics

et al

  
     
      
     


  

        
        

      



     



Figure 2.2. Detailed proxy records during the fourth millennium BC in Iran. A and B show the percentage of oak pollen at
Mirabad and Zeribar respectively (Van Zeist and Boema 1977). C and D show the δ18O records from the same records (Stevens
 2006). The fourth millennium BC is highlighted; there is a clear drop in oak around 5.2 kyr BP, associated with desiccation
at the site and the most positive oxygen isotope values, which may mark the regional 5.2 kyr BP drought.
2. Mid-Holocene environmental and climatic change in Iran 

        

  


et al




 et al.       
        

      
      

  


 


c.


et al
Sea-level change
       
      
       
      
et al et
al
      

et al

      


      
    
      


et al
       
       


      
        


c.



c.
et al.
       



c

Evidence of change from the wider
region

       



      

   
        
       
et
al.
et al.

    
et al

       
et
al



et al
      
       

      
      
       



        

      
 
     
      

      
     
     
M. Jones, M. Djamali, L. Stevens,V. Heyvaert, H. Askari, D. Noorollahi and L. Weeks
 
 


      





Figure 2.3. Maps of terrestrial “wetness“ during the mid-Holocene in Iran and surrounding regions. Sites used are listed in Table 1.
2. Mid-Holocene environmental and climatic change in Iran 




       


  



 et al      
    



      
      
       


      







et al.
Summary
         







    

      

     
     
         
     

         

       
     

Bibliography

Annals of the Association of American
Geographers
         


  
Akkadica


       
Quaternary Research
Site Proxy Denition of “wet” Reference
   et al.
   et al.
   
   
   
  et al.
  et al.
   
   
   
  et al.
   
  et al.
   
Table 2.1. Sites and proxies used in the development of “wetness” maps (Fig. 3).
M. Jones, M. Djamali, L. Stevens,V. Heyvaert, H. Askari, D. Noorollahi and L. Weeks
       
Palaeogeography,
Palaeoclimatology, Palaeoecology

Philosophical
Magazine Series 3

Quaternary Sciences
Reviews

Review of Palaeobotany
and Palynology


Paleoclimates, paloenvironments
and human communities in the eastern Mediterranean region
in later prehistory,
        
        
         
      Journal of
Quaternary Science


   
        
     
Quaternary Science Reviews
   

     




     Quaternary
Science Reviews

        

  

Vegetation History and Archaeobotany



    
Quaternary Research



  
      

Holocene

 
        
Science 
        

        

    Quaternary Science
Reviews

      
Atmospheric Research
   Les Qanats, une technique d’acquisition
de l’eau      

         
     
      Holocene


      Iranica
Antiqua
    Fluvial Sedimentation, Sea-
level History and Anthropogenic Impact in the Great
Mesopotamian plain: A new Holocene Record

       

   Marine Geology

      
Chiefdoms
and Early States in the Near East; the Organizational
Dynamics of Complexity   

      
      

The Origins of Agriculture and Crop Domestication


        
        
       
      
Marine Geology
        
Explorations in Turkestan

         
   
   Quaternary International


       

      Quaternary
International


   Quaternary International


Theoretical and Applied Climatology
      
  
Science
         
Geographical Journal

2. Mid-Holocene environmental and climatic change in Iran 
    

   
Third Millennium BC Climate Change
and Old World Collapse
       
      Nature 


      
Proceedings of
the International History Seminar on Irrigation and Drainage

         

   
Quaternary Research


         
The Origins of State Organizations in Prehistoric Highland
Fars, Southern Iran: Excavations at Tall-e Bakun


         
      
Quaternary Research

    


      
Journal of Quaternary Science

   
      
      
GeoResearch Forum     

       
   
      

Quaternary International

 
Quaternary Research
       


Quaternary Science Reviews 

      
Hydrology and Earth System Sciences
Discussions
  
       
        

Palaeogeography, Palaeoclimatology, Palaeoecology
        
       
  Géomorphologie



Antiquity
         
    
   
       
    
Holocene






    Quaternary Science
Reviews
        
        
     
  
      
  Quaternary Science Reviews 

       

Quaternary International
      
        

Paléorient


Quaternary Research


The Holocene


      
      
Quaternary Research 
          

 Marine Geology

       
Palaeohistoria

   
   
Geodinamica Acta



Geomorphological mapping: a professional handbook of
techniques and applications

        
 
    

   Quaternary Science Reviews 

M. Jones, M. Djamali, L. Stevens,V. Heyvaert, H. Askari, D. Noorollahi and L. Weeks

        

Quaternary Research
    

     
      
     Holocene

Geobotanical foundations of the Middle East

... numbers of dated samples are assumed to correlate with data points for settlement density, etc.) [27]. In this regard, the 3rd millennium BCE (5-4 ka BP) is considered as a key transition period in terms of climatic conditions [28,29] and the simultaneous emergence of more urban societies on the CIP [7,30]. ...
... 2. Does the model output correspond to the existing information from terrestrial archives/ proxies (pollen, δ18O) regarding the general climatic trends? What can we learn from the model about aridity events commonly discussed as possible explanation for settlement crises in archaeological studies covering the Mid-Holocene [6,9,30]? ...
... While these syntheses provide a relatively clear picture of climatic changes in eastern Central Asia, reconstructions for Western Central Asia are rare. Based on pollen and oxygen-isotope records, Jones et al. [30] deduce the wettest period during the Holocene for the Zagros Mountains and northwestern Iran from approx. 7 ka to 5 ka BP. ...
Article
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Settlement crises in ancient cultures of Western Asia are commonly thought to be caused by climatic events such as severe droughts. However, the insufficient climate proxy situation in this region challenges the inference of clear relationships between climate and settlement dynamics. We investigate the Holocene climatic changes on the Varamin Plain in the context of the climatic history of Western Central Asia by using a transient comprehensive Earth System Model simulation (8 ka BP to pre-industrial), a high-resolution regional snapshot simulation and a synthesis of pollen-based climate reconstructions. In line with the reconstructions, the models reveal only slightly varying mean climatic conditions on the Varamin Plain but indicate substantial changes in seasonality during the Holocene. Increased precipitation during spring, combined with lower temperature and potentially stronger snow accumulation on the upstream Alborz mountains may have led to an increased water supply on the alluvial fan during the vegetation period and thus to more favourable conditions for agricultural production during the Mid-Holocene compared to modern times. According to the model, dry periods on the Central Iranian Plateau are related to particularly weak Westerly winds, fostering the subsidence in the mid-troposphere and hampering precipitation over the region. The model reveals that dry periods have spatially heterogenous manifestations, thus explaining why they do not appear in all proxy records in the wider study region. In fact, the climatic signal may depend on local environmental conditions. The interaction of the topography with the atmospheric circulation leads to additional spatial heterogeneity. Although our results provide several indications for a connection between climate and settlement dynamics, the small overall changes in moisture call into question whether climate is the main driver for settlement discontinuities on the Central Iranian Plateau. To shed further light on this issue, more high-resolution long-term proxy records are needed.
... Therefore it is assumed that the effective wetness decreased. This may be caused by factors like a decline in precipitation, an increase of evaporation, a decrease in wetness and/or an increase of seasonality (Jones et al., 2013). The occurrence of sand strata in the upstream part of the study area may point to an increase of seasonality. ...
... The transition from a dominant erosional to a dominant depositional fluvial environment during the early Holocene is most probably also forced by a climate change. There is definitely evidence of climate changes during the Holocene in Iran but because of the vast extent of the country and its diverse landscapes, the shift of the climatic settings is not uniformly spread (Jones et al., 2013). Although in the Zagros Mountains and also in the Taurus Mountains in Turkey forest expansion was delayed relative to the forests in the Mediterranean (Van Zeist and Bottema, 1977;Wick et al., 2003;Stevens et al., 2006;Djamali et al., 2008;Litt et al., 2009;Schmidt et al., 2011), in both mountain sites an increase in wetness is observed since the end of the Younger Dryas. ...
Article
The early- and mid-Holocene deposits of the Lower Khuzestan plain at the north-eastern margin of the Persian Gulf have been investigated by means of facies analysis of sediment successions of undisturbed cores. Organic material and molluscs have been selected for dating by radiocarbon whereby possible contamination by hard-water effect is discussed. The results suggest that the Holocene transgression in Mesopotamia may have taken place later than generally accepted. Before ca. 7700–7900 yr cal. BP, the plain was characterized by mud-dominated fluvial systems. During the mid-Holocene, tides invaded the existing valleys, and the sedimentary environment shifted from fluvial to estuarine but not as extensively as has previously been suggested. The estuarine environments lasted for about 2000–2500 years until ca. 4850–5000 yr cal. BP when the seaward part of the plain was again characterized by widespread fluvial sedimentation.
... The climate of the last interglacial period (LIG: 150,000-120,000 years ago) was relatively warm or warmer than the present (Kukla et al. 2002;Pickarski 2014). The climate of the mid-Holocene had relatively increased in rainfall along with wetter condition than in the contemporary period in southern and southwest Asia to northern Africa that resulted in both African and Asian monsoons (Texier et al. 2000;Wanner et al. 2008;Jones et al. 2011). ...
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Surveying the role of climate changes on the species distributions in the past, present and future, and correlating these with changes in distribution ranges have attracted considerable research interest. The leopard geckos of the genus Eublepharis Gray, 1827 (family Eublepharidae), as a vicariate group, comprises six valid species distributed from Turkey through the Iranian Plateau to India, of which E. angramainyu, E. macularius and E. turcmenicus occur in Iran. In this study, we modelled the potential distribution areas for E. angramainyu and determined the suitable habitats in the past (the last interglacial [LIG] and mid-Holocene [MH]), present (1950–2000), and also predicted four scenarios in the future (2050) by using the maximum entropy approach (MaxEnt). The obtained models indicated very good values of the area under curve (AUC): LIG = 0.996 ± 0.003, MH = 0.996 ± 0.004, contemporary period = 0.995 ± 0.004, and the future = 0.997 ± 0.002. Precipitation of the coldest quarter and precipitation of the warmest quarter were the most important factors shaping the distribution of E. angramainyu. As it seems, climatic changes have been responsible for a southward shift in distribution and suitable habitats of E. angramainyu from the LIG (~150,000–120,000 years ago) to the future. The representative concentration pathway (RCP) 2.6 scenario model of the future predicted a much more restricted distribution and less suitable habitats due to radiation of the forcing level which reaches a value of around 3.1 W/m² by mid-century and returns to 2.6 W/m² by 2100.
... Past climate and environmental change is of longstanding and fundamental interest to archaeologists (Jones et al. 2011). Although the high power of adaptation in Homo sapience has allowed him to make fundamental changes in the subsistence system and the organization of technology (Jajarmi et al. 2015), however, during the Holocene, southwest Asia witnessed the rise and decline of many agricultural-based communities due to abrupt climate change (Staubwasser and Weiss 2006;Weiss 2017). ...
Article
Full-text available
Climate change is significantly affecting the livelihoods and health of human societies. During the Holocene, climatic events have occurred repeatedly. These events typically have affected large regions between 100 and 600 years. Paleoclimate studies of the Northern Hemisphere have identified climatic events of 9.2, 8.2, 5.2, 4.2, 3.2 ka BP, Roman warming, the early medieval cooling, medieval warming, and Little Ice Age. Also, by adapting the archaeological studies and the paleoclimate research of Iran, other periods of climate change such as 7.5, 7, 6.2 and 4.8 ka BP can be introduced. Due to the vastness and geographical diversity of Iran, the impact of each of these events in different parts of the country has been different, but, in general, during droughts related to climate change, semi-arid to arid regions of Iran have been more vulnerable, and therefore, people were using a variety of strategies to resilience and adapt, such as changing subsistence patterns, managing water resources, and migrating. However, in some periods of climate change, the effects of climatic hazards have been such that it has led to the cultural, socioeconomic and political decline of societies.
... These soils likely are developed under wetter conditions than the LGM during post-glacial times and the Holocene. A palaeoclimatic model presented by Jones et al. (2013) shows that following an early Holocene semi-arid phase, northeastern Iran experienced a mid-Holocene (7-6 ka) wet phase. This wet phase took place in response to orbitally induced changes in insolation. ...
Chapter
The stable isotopic composition of pedogenic carbonate forms in equilibrium with environmental parameters and, thus, records palaeoenvironmental signals. The aims of this study are to synthesize available data on the stable isotopic composition of Quaternary pedogenic carbonates in calcareous parent materials of Iran and to decipher paleoenvironmental implications of the isotopic data for the country. Isotopic composition and microfabric of pedogenic carbonates in 18 pedons in both gravelly (calcareous alluvium in central Iran) and non-gravelly deposits (calcareous loess in northeastern Iran) have been investigated. The results indicate that in limestone-derived soils of central Iran in situ weathering of calcareous pebbles is a major source of Ca for genesis of the carbonates, and carbonate features consist of micritic calcite crystals. In the loessic soils of northeastern Iran, pedogenic carbonates show a dominance of nodule morphology and are classified as orthic nodules. Microfabric analysis reveals that most of the carbonates have not been altered by diagenetic processes, especially the Holocene carbonates, and are suitable for isotopic study and palaeoreconstructions. In limestone-derived soils within the arid region of central Iran, the δ18O and the δ13C values carbonates indicate their enrichment due to the effects of evaporative water loss, a decline in plant density and the entrance of atmospheric CO2 into the soils. In semi-arid ecosystems of central and northeastern Iran, most of the Holocene carbonates have formed in equilibrium with the ambient environment and are suitable for palaeoenvironmental reconstructions. The combination of carbon and oxygen isotopic data demonstrates the dominant role of climate in determining the δ13C values of carbonates. There is a strong relationship between the δ13C values of carbonates and rainfall, and between O isotopes and aridity indices. Stable isotope patterns in Holocene soils appear to provide data for models that can then be used to interpret the many localities where Pleistocene aged soils and associated carbonate exist.
... These soils likely are developed under wetter conditions than the LGM during post-glacial times and the Holocene. A palaeoclimatic model presented by Jones et al. (2013) shows that following an early Holocene semi-arid phase, northeastern Iran experienced a mid-Holocene (7-6 ka) wet phase. This wet phase took place in response to orbitally induced changes in insolation. ...
Article
The stable isotopic composition of pedogenic carbonate forms in equilibrium with environmental parameters and, thus, records palaeoenvironmental signals. The aims of this study are to synthesize available data on the stable isotopic composition of Quaternary pedogenic carbonates in calcareous parent materials of Iran and to decipher paleoenvironmental implications of the isotopic data for the country. Isotopic composition and microfabric of pedogenic carbonates in 18 pedons in both gravelly (calcareous alluvium in central Iran) and non-gravelly deposits (calcareous loess in northeastern Iran) have been investigated. The results indicate that in limestone-derived soils of central Iran in situ weathering of calcareous pebbles is a major source of Ca for genesis of the carbonates, and carbonate features consist of micritic calcite crystals. In the loessic soils of northeastern Iran, pedogenic carbonates show a dominance of nodule morphology and are classified as orthic nodules. Microfabric analysis reveals that most of the carbonates have not been altered by diagenetic processes, especially the Holocene carbonates, and are suitable for isotopic study and palaeoreconstructions. In limestone-derived soils within the arid region of central Iran, the δ ¹⁸ O and the δ ¹³ C values of carbonates indicate their enrichment due to the effects of evaporative water loss, a decline in plant density and the entrance of atmospheric CO 2 into the soils. In semi-arid ecosystems of central and northeastern Iran, most of the Holocene carbonates have formed in equilibrium with the ambient environment and are suitable for palaeoenvironmental reconstructions. The combination of carbon and oxygen isotopic data demonstrates the dominant role of climate in determining the δ ¹³ C values of carbonates. There is a strong relationship between the δ ¹³ C values of carbonates and rainfall, and between O isotopes and aridity indices. Stable isotope patterns in Holocene soils appear to provide data for models that can then be used to interpret the many localities where Pleistocene-aged soils and associated carbonate exist.
Article
This article aims to show that virtual water has historically been an adaptation strategy that enabled some arid regions to develop a prosperous economy without putting pressure on their scarce water resources. Virtual water is referred to as the total amount of water that is consumed to produce goods and services. As an example, in arid central Iran, the deficiency in agricultural revenues was offset by more investment in local industries that enjoyed a perennial capacity to employ more workers. The revenues of local industries weaned the population from irrigated agriculture, since most of their raw materials and also food stuff were imported from other regions, bringing a remarkable amount of virtual water. This virtual water not only sustained the region's inhabitants, but also set the stage for a powerful polity in the face of a rapid population growth between the 13th and 15th centuries AD. The resultant surplus products entailed a vast and safe network of roads, provided by both entrepreneurs and government. Therefore, it became possible to import more feedstock such as cocoons from water-abundant regions and then export silk textiles with considerable value-added. This article concludes that a similar model of virtual water can remedy the ongoing water crisis in central Iran, where groundwater reserves are overexploited, and many rural and urban centers are teetering on the edge of socio-ecological collapse. History holds an urgent lesson on sustainability for our today's policy that stubbornly peruses agriculture and other high-water-demand sectors in an arid region whose development has always been dependent on virtual water.
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The ongoing changes affecting Lake Urmia (NW Iran) are revealed by the lake water level decrease (∼7 m in the last 20 yr) that was attributed to natural and anthropogenic causes but the exact impact of these factors on the state of the lake is still not identified. Indeed, lack of detailed record of environmental evolution of the lake in the past limits the understanding of actual and future processes. Our project aims to obtain a high-temporal resolution record of environmental changes in the lake area for the last ∼30 kyrs. Sediment cores have been obtained from the recently dried out part of the lake near Urmia City, and surface and ground waters have been measured for electric conductivity. This paper presents results of water and sediments analyses. Six ¹⁴C AMS dating on organic fractions provide a chronological framework and indicate that the record covers the last ∼30 cal kyr BP. During this period, evaporitic conditions were prevailing in the lake. The electric conductivity of brines from the sediment highlights changes in the lake water salinity. The data indicate a lake-level low stand at ∼30 cal kyr BP that was followed by a water level rise and establishment of lacustrine conditions for the next ∼9 kyr, this phase representing the highest lake level recorded since that time to date. From the LGM, the lake experienced several fluctuations of the water level. The relatively long-term lacustrine condition established during the Early Holocene before the water level decrease between ∼5.5 and 4.9 cal kyr BP. Sediments from the two dry events at ∼30 cal kyr BP and at 5.5–4.9 cal kyr BP are characterized by the presence of greigite, which indicates anaerobic early diagenetic conditions in the sediment.
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During the Bronze Age, the cultural region of North Central Iran (NCI) suffered a longterm cultural decline, probably due to severe droughts. According to paleoclimate research, during the overall period c. 5.4–3.5 ka BP, four widely observable climatic events occurred at c. 5.3–5.0, 4.9–4.7, 4.2–3.9, and 3.8–3.5 ka BP, and these appear to have caused widespread environmental damage in the Near East. Archaeological evidence of the NCI-region reveals political events that can be associated with the observed climatic variability. Paleoclimate research and archaeological studies can attribute, in combination, the cultural decline of NCI during the Bronze Age to the Late Holocene climate change.
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In 2016, an extensive fossil forest was discovered near Meshgin Shahr, northwest Iran. Silicified tree trunks occur in Miocene fluvial sediments and at multiple stratigraphic levels within a 27-m thick sequence of Pleistocene volcaniclastics. The Miocene trunks likely represent stream transport. Pleistocene examples originated during repeated eruptive events when volcaniclastic sediments buried a standing forest. The site, informally named Meshgin Shahr Fossil Forest, was registered in 2017 as a national natural monument by the Iranian Cultural, Handicraft and Tourism Organization. To date, 16 fossilized trunks have been found, all but one of them representing gymnosperms. The ancient coniferous forest was very different from modern forests in Iran and adjacent Azerbaijan, a result of climatic changes that were principally caused by the demise of the Paratethys Sea and by rain shadow effects caused by the uplift of the Alborz and Zagros mountain ranges. X-ray diffraction patterns reveal that woods from the fossil forest contain three types of silica: opal-CT, pure quartz, and a mixture of opal-CT and quartz. In addition, optical photomicrographs show the abundant presence of amorphous opal-A. Mineralogic variations occur among different fossil trees and within a single trunk. These silica polymorphs resulted from a combination of processes: silica minerals precipitated in multiple episodes under differing geochemical conditions and the diagenetic transformation of an opaline parent material.
Conference Paper
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Walstra, J., Heyvaert, V. M. A. & Verkinderen, P. 2009. Remote sensing for the study of fluvial landscapes in Lower Khuzestan, SW Iran. RSPSoc 2009 Annual Conference, 8-11 September 2009, Leicester, UK, 9 pp. (ISBN 0-946226-34-2).
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The Caspian Sea is well-known for its rapid sea-level change. During 1929–1995, a full sea-level cycle was observed. First, the sea level dropped ∼3 m with a lowstand in 1977, followed by a 3 m rise to 1995, after which the sea level has been relatively stable. These oscillations are a specific feature of the Caspian Sea and its sedimentary record. The main purpose of this study is to reconstruct the sea-level curve in the Holocene by using sedimentological and biostratigraphic analysis and radiocarbon dating along the Iranian part of the Caspian shore. Remote sensing images and historical maps show that two lagoons totally emerged, and the Gorgan delta prograded rapidly at a rate of around 160 m y−1 until the 1975 lowstand. Gorgan Bay was reduced in size considerably and the connection to the sea was blocked due to growth of a spit and change in base level. When sea level started to rise again, the coastal morphology rapidly changed and the Gorgan delta retrograded at the rate of around 140 m y−1. These sedimentary dynamics can be recognized in the preserved deposits. In addition to the recent dynamics, core data from the southeastern lowlands show four earlier highstands. Using characteristic barrier-lagoon deposits, early Holocene sea level rose until a highstand was reached of ca. −34 m. This phase was followed by fluvial deposition in the Gorgan delta associated with a base level fall. There is also an evidence of sea-level rise between 5000 and 2300 BP at ca. −27.7 m. On top of these deposits there is evidence of a highstand between 2700 and 2300 BP at ca. −23.5 m. The fourth highstand from the core data is dated to the Little Ice Age at ca. −24 m. Data from these last two highstands correspond well with other observations from the Caspian region.
Article
On présente ici un tableau général de l'évolution des espaces littoraux du golfe Persique et du golfe d'Oman durant l'Holocène, en insistant sur la forte mobilité de ces espaces au cours de cette période, en raison du rôle complexe de la mer, de la glacio-hydro- isostasie, des changements climatiques et hydrologiques et enfin de l 'intervention de l 'Homme. Un rappel est fait des données océanologiques des deux domaines marins. Sont ensuite analysés les différents secteurs géographiques et plus particulièrement étudiée l'évolution complexe des lagunes (notamment celle d'Umm al-Qowayn, dans les Emirats, et celle des paléolagunes de la plaine du Shinzani, au Makran). La grande mobilité des littoraux est attestée par les témoins des nombreuses lignes de rivage holocènes qui se regroupent, pour la plupart, en trois phases, 6 500-5 500 BP, 4 500-3 000 BP et 2 000-1 500 BP, que l'on retrouve à peu près partout. Le relèvement glacio-hydro-isostatique, faible, est général mais des zones sont tectoniquement actives (Makran) et l'eustatisme n 'est pas niable, même si leurs effets sont masqués ou perturbés par des changements océanologiques.