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首页> 外文期刊>Estuarine Coastal and Shelf Science >Chronology of the sedimentary processes during the postglacial sea level rise in two estuaries of the Algarve coast, Southern Portugal
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Chronology of the sedimentary processes during the postglacial sea level rise in two estuaries of the Algarve coast, Southern Portugal

机译：葡萄牙南部阿尔加维海岸两个河口冰川后海平面上升期间沉积过程的年代学

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摘要

Four profiles of estuarine sediments obtained from boreholes drilled in the Algarve, Southern Portugal were studied in order to reconstruct the process of sediment accumulation driven by the postglacial sea level rise. In addition to the sedimentological analysis, the Foraminifera Index of Marine Influence (FIMI) permitted assessment of the nature and organization of sedimentary facies in the Beliche-Guadiana and Gilao-Almargem estuaries. The Beliche-Guadiana CM5 and Almargem G2 profiles accumulated in a sheltered environment, with the former present-ing an almost continuous record of the sea level rise since ca 13 000 calyr BP. The G1 and G3 profiles from the Gilao-Almargem area represent a more discontinuous record of the last 8000 years, which accumulated in the more dynamic environment of an outer estuary. The integration of all radiocarbon ages of dated levels, led to an estimate of sediment accumulation rates. Assuming a constant position of the sediment surface with respect to the tidal range and a negligible compaction of sediment, the sea level rose at the rate of 7 mm yr~(-1) in the period from 13 000 to 7500 cal yr BP. This process slowed down to ca 0.9 mm yr~(-1) from 7500 cal yr BP until the present. The marked historical change in the rate of sediment accumulation in these estuaries also occurred with the accumulation of organic matter and is, therefore, important data for global bio-geochemical models of carbon. The main obstacle to obtain higher temporal resolution of the sedimentary processes was the intense anaerobic respiration of organic matter via sulphate reduction, which did not allow any accumulation of peat and, furthermore, led to erasure of the palae-ontological record by acid formed from the subsequent oxidation of sulphides.
机译：为了重建冰川后海平面上升驱动的沉积物堆积过程，研究了从葡萄牙南部的阿尔加维钻探的钻孔中获得的四种河口沉积物剖面。除了沉积学分析，海洋有孔虫指数（FIMI）还允许评估Beliche-Guadiana和Gilao-Almargem河口的沉积相的性质和组织。 Beliche-Guadiana CM5和Almargem G2剖面积累在一个有遮盖的环境中，前者自从大约13000 cal BP以来几乎连续记录了海平面上升的情况。 Gilao-Almargem地区的G1和G3剖面代表了过去8000年的更不连续的记录，这些记录积累在外部河口更活跃的环境中。对所有已过期水平的放射性碳年龄的综合，得出了沉积物沉积速率的估计值。假设相对于潮汐范围的沉积物表面位置恒定并且沉积物的压实程度可以忽略不计，那么在从13 000到7500 cal yr BP期间，海平面以7 mm yr〜（-1）的速率上升。该过程从7500 cal yr BP一直减慢到大约0.9 mm yr〜（-1）。这些河口的沉积物沉积速率的明显历史变化也随着有机质的积累而发生，因此，这是全球碳生物地球化学模型的重要数据。要获得更高的沉积过程时间分辨率，主要障碍是通过硫酸盐还原法进行的有机物强烈厌氧呼吸，这不允许泥炭的任何积累，而且，导致由古生物形成的酸擦除了古生物学记录。随后硫化物的氧化。

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