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Reconstruction of the Holocene hydro-ecological and environmental change of the Nile Delta: insights from organic geochemical records in MZ-1 sediment core
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  • Fan Zhang,
  • Jianfang Hu,
  • Xinxin Li,
  • YANNA WANG,
  • Chengpeng Sun,
  • Xiaoshuang Zhao,
  • Feng Jiang,
  • Xin Zhao,
  • Yan Liu,
  • Alaa Salem,
  • A. M Abu Shama,
  • Zhongyuan Chen
Fan Zhang
Department of Ocean Science and Engineering Southern University of Science and Technology
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Jianfang Hu
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences
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Xinxin Li
Southern University of Science and Technology

Corresponding Author:[email protected]

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YANNA WANG
East China Normal University
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Chengpeng Sun
Department of Ocean Science and Engineering Southern University of Science and Technology
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Xiaoshuang Zhao
State Key Laboratory for Estuarine and Coastal Research, East China Normal University
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Feng Jiang
State Key Laboratory for Estuarine and Coastal Research, East China Normal University
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Xin Zhao
Department of Ocean Science and Engineering, Southern University of Science and Technology
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Yan Liu
State Key Laboratory of Estuarine and Coastal Research
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Alaa Salem
Kafrelsheikh University
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A. M Abu Shama
Kafrelsheikh University
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Zhongyuan Chen
East China Normal University
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Abstract

The Holocene hydro-ecological and environmental change of the Nile Delta remains a knowledge gap. The study aimed to approach this objective by using multi-proxies of organic carbon (OC) in a well-dated MZ-1 core in Manzala lagoon off the Nile Delta. The data defined five distinctive stages at decadal-centennial scale. Stage I (ca. 8.2-7.7 ka) was characterized by remarkedly high reconstructed pH and low mean annual air temperature (the 8.2-ka cold event). The obviously low TOC and C/N, but higher short-chain n-alkanes indicated more marine OC deposition. This was followed by highly fluctuated organic geochemical proxies at Stage Ⅱ (ca. 7.7-5.8 ka) indicating episodic but significant terrestrial OC input delivered by Nile floods during the African Humid Period (AHP). Subsequent increase in short- and medium-chain n-alkanes suggested macrophytes prevailing in the lagoon during Stage Ⅲ (ca. 5.8-5.4 ka) with cooling-drying climate transitioned from the AHP. Stage Ⅳ (ca. 5.4-1.2 ka) witnessed decreased short-chain n-alkanes of marine origin and increased long-chain n-alkanes of terrestrial origin when the Nile climate entered into the mega-trend of aridification. Abnormal pulses of terrestrial OC with high TOC likely reflected the modified landscape due to early human occupation around the area. The highly fluctuated charcoal fluxes since ca. 6 ka implied such clearing-firing-aided land exploitation activity. The lagoon eco-setting was further affected by intensified anthropogenic-OC input after the latest millennium. Our study highlighted the land-ocean interactions on modulating the paleo-lagoonal ecology of the Nile Delta, which should be incorporated into healthy management in the Nile Delta.
Jan 2022Published in Marine Geology volume 443 on pages 106684. 10.1016/j.margeo.2021.106684