Nile Delta's sinking past: Quantifiable links with Holocene compaction and climate-driven changes in sediment supply?
Nile Delta's sinking past: Quantifiable links with Holocene compaction and climate-driven changes in sediment supply?
复制标题
尼罗河三角洲下沉的过去：与全新世压实和气候驱动的沉积物供应变化之间的可量化联系？
作者：
N. Marriner;C. Flaux;C. Morhange;D. Kaniewski
尼罗河三角洲是一个下沉的沉积盆地，拥有埃及66%的人口和60%的粮食产量。未来几十年预计的海平面上升情景使人们更加关注三角洲对可容纳空间快速变化的潜在弹性。我们使用年代地层数据从194个有机丰富的泥炭和泻湖点定量重新评估尼罗河三角洲表面动态的驱动程序在全新世。重建的沉降速率范围为0.03至4.5 mm/年，最高的是Manzala、Burullus、Idku和Maryut泻湖，这些地区对应于深层晚更新世地形，充满了可压缩的全新世地层; 88%的沉降值<2 mm/年。我们认为，在全新世两个显着的，但以前被低估的贡献者在尼罗河三角洲的质量平衡的变化已被沉积物压实和沉积物供应的轨道强迫变化。8000 - 4000校准（cal）14 C年B. P.之间，空间平均沉积速率大于沉降速率，这意味着三角洲加积是区域尺度上的主要地貌过程。因为CA。4000卡/年B. P.尼罗河沉积物供应量的急剧下降，加上三角洲湿地的人为排水，使沉积中心对海平面上升和极端洪水事件的退化更加敏感。
The Nile Delta is a subsiding sedimentary basin that hosts ~66% of Egypt’s population and 60% of the country’s food production. Projected sea-level-rise scenarios for the coming decades have sharpened focus on the delta’s potential resilience to rapid changes in accommodation space. We use chronostratigraphic data from 194 organic-rich peat and lagoon points to quantitatively reevaluate the drivers of Nile Delta surface dynamics during the Holocene. Reconstructed subsidence rates range from 0.03 to 4.5 mm/yr, and are highest in the Manzala, Burullus, Idku, and Maryut lagoons, areas that correspond to deep late Pleistocene topography infi lled with compressible Holocene strata; 88% of the subsidence values are <2 mm/ yr. We suggest that during the Holocene two signifi cant but previously underestimated contributors to changes in Nile Delta mass balance have been sediment compaction and orbitally forced changes in sediment supply. Between 8000 and 4000 calibrated (cal) 14 C yr B.P., spatially averaged sedimentation rates were greater than subsidence, meaning that delta aggradation was the dominant geomorphological process at the regional scale. Since ca. 4000 cal yr B.P., a sharp climate-driven fall in Nile sediment supply, coupled with the human-induced drainage of deltaic wetlands, has rendered the depocenter more sensitive to degradation by sea-level rise and extreme fl ood events.