武汉东湖是如何形成的?

Formation of East Lake, Wuhan, Eastern China

东湖位于湖北省武汉市中心城区,是中国乃至亚洲最大的城中湖之一.她是首批国家重点风景名胜区和国家5A级旅游景区.武汉市正在打造东湖城市生态绿心.东湖对于武汉在资源、环境、生态、人文各方面均具有重要意义.关于东湖的成因长期众说纷纭.研究首次从地质、地貌、沉积等方面对东湖的成因进行了分析,并对东湖与长江的关系进行了讨论.(1)东湖位于中-晚更新世形成的岗地区.湖汊发育,岸线蜿蜒,岬湾交错,是东湖最大的特点.(2)东湖的湖相沉积厚度各处不一,总体呈现南薄北厚、边缘薄中间厚的特点.下伏主要地层为晚更新世下蜀黄土,在靠近基岩残丘的南部边缘局部为晚更新世坡积层,两者之间为明显的侵蚀接触关系.(3)东湖的湖盆形成于距今2万年左右的末次冰期盛期.东海海平面的大幅度下降,长江河床深切.发育于长江南岸珞珈山、南望山、喻家山一带的地表径流,在汇入长江时因江水水位较低而发生侵蚀,形成多条冲沟组合而成的侵蚀洼地.之后,随着冰后期的全球变暖,长江水位快速上升,两岸天然堤发育、壮大,使侵蚀洼地的出口被淤塞,逐渐积水成湖,即东湖为沟谷壅塞湖.(4)根据湖泊地质地貌特征,东湖与沙湖是两个不同成因且相对独立的湖泊;长江并未经东湖流过.但东湖的形成与长江有关,乃是全球气候变化驱动下海、江、湖相互作用的产物.(5)东湖之美,美于自然.保护其自然特质,顺应其自然规律,是东湖保护与利用必须坚持的原则.将湖域、湖岸、岸上作为一个整体,将水域和流域作为一个系统,按照山水林田湖草生命共同体的科学理念,对东湖进行整体性和系统性的保护与治理是十分必要的.

The East Lake, located in the downtown of Wuhan city, Hubei Province, is the largest city lake in China or even in Asia. It is one of the first batches of national key scenic spots and 5 A tourist attractions, and has been an important water source area for industrial, agricultural production and aquatic base in Wuhan. Nowadays, in Wuhan it building the ecological green heart of East Lake, therefore there is great significance for resources, environment, ecology and humanity. However, the formation cause of the East Lake has long been disputed. This study is the first one to analyze the origin of the East Lake from many aspects,including geology, geomorphology and sedimentation, further to discuss the relationship between the East Lake and the Yangtze River. The main conclusions are as follow:(1) The geomorphological characteristics of the lake: branching, meandering coastline and headlands and bays, this is generally developed on the hillock of Middle-Late Pleistocene.(2) The thickness of lacustrine sediments in East Lake is various, showing thin in the south and thick in the north, thin in the margin and thick in the middle. The underlying strata are mainly the Late Pleistocene Xiashu loess, and the Late Pleistocene slope layer is locally distributed near the southern margin of the bedrock residual mound. There is an obvious unconformable relationship between lacustrine sediments and Xiashu loess.(3) The basin of East Lake was formed in the last glacial maximum(LGM) about 20 ka ago. In this time, the sea level of the East China Sea has dropped sharply, and induced the riverbed of the Yangtze River incised. The Luojia, Nanwang and Yujia mountains on the south bank of the Yangtze River were deeply incised landscape when it flowed into the Yangtze River due to low erosion baseline of the LGM, resulting in a series of gullies. After that, the Holocene global warming and high sea-level,the water surface of the Yangtze River rose rapidly, and the natural dikes along its banks developed and expanded with resultant in filling of the incised gullies, accounted for the formation of lake. Based on the above analyses, the East Lake was a gully choked lake.(4) According to the characteristics of geology and geomorphology, the East Lake and Shahu Lake are two independent lakes with different formation processes. The Yangtze River does not flow through the East Lake, however, the formation of the East Lake is related to the Yangtze River, which is the result of the complex feedback of the East China Sea-Yangtze River-East Lake,this process was driven by global climate change.(5)The worth of the East Lake lies in nature. Protecting its natural characteristics and conforming its natural laws is principles of protection and utilization of the East Lake. As a whole, for the scientific concept of mountain-water-forest-paddy-lake-grass community, it is necessary to regard lake shore and landform as a whole and regard catchment and basin as a whole to protect and manage the East Lake in a holistic and systematic way.