Abstract

The Gorgan Plain (NE Iran) is characterized by fertile soils formed on a loess plateau and is at present primarily exploited for intensive agriculture. However, the timing and intensity of the human impact on the landscape in the past are still unclear. A sediment core, taken from the centre of the eastern Gorgan Plain in the Kongor Lake covering the major part of the Holocene from 6.1 to 0.8 ka (all ages are calibrated before present), has been studied for pollen, non-pollen palynomorphs, botanical macroremains, insects, charcoal, geochemistry, biomarkers and magnetism in order to provide new insights into the evolution of the landscape and to estimate the intensity of human activities. The data obtained suggest a dry period between 5.9 and 3.9 ka and an increase in regional humidity afterwards with a maximum between 2.7 and 0.7 ka, during the period of the Persian empires (Achaemenid through Sasanian) and the Islamic era. The eastern part of the Gorgan Plain was characterized by open steppe landscapes during the last 6 ka, which most likely were used for pasture and at least since 2.7 ka for agriculture including arboriculture. The strongest anthropogenic impact on the environment around the Kongor site is documented during the Parthian and Sasanian Empires (200 BC–651 AD) and the Islamic era up to the eve of the Mongol invasion.

Highlights

  • The Gorgan Plain (NE Iran) is located at the southeastern corner of the Caspian Sea between the Alborz Mountains and the Turkmen steppe (Figure 1a)

  • The Holocene vegetation history of the eastern part of the Alborz Mountains has been studied on a lagoonal core from the SE Caspian Sea (Leroy et al, 2013a), providing general vegetation changes during the highstands of the Caspian Sea at 10.6–7.2 ka and 3.5 ka–present from deciduous Quercus to Carpinus betulus, Parrotia persica and Fagus orientalis-Pterocarya fraxinifolia

  • The permanent water body formed an efficient trap for aeolian particles, explaining high dust input causing a very high sedimentation rate, high DBD, K and Ti contents and κLF in accordance with low total organic carbon (TOC), n-alkanes and few plant and beetle remains during this period

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Summary

Introduction

The Gorgan Plain (NE Iran) is located at the southeastern corner of the Caspian Sea between the Alborz Mountains and the Turkmen steppe (Figure 1a). Combined records of GS05 and CP14 from the southern Caspian Sea reflect major late glacial and Holocene climate and vegetation changes in comparison to the Caspian Sea level changes (Leroy et al, 2013b). The Holocene vegetation history of the eastern part of the Alborz Mountains has been studied on a lagoonal core from the SE Caspian Sea (Leroy et al, 2013a), providing general vegetation changes during the highstands of the Caspian Sea at 10.6–7.2 ka and 3.5 ka–present from deciduous Quercus to Carpinus betulus, Parrotia persica and Fagus orientalis-Pterocarya fraxinifolia. Peat or lake cores are more suitable for local environmental reconstructions of the Gorgan Plain

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