末次冰盛期后黄河三角洲潮滩沉积及其环境指示

SEDIMENTARY INFORMATION OF TIDAL FLAT OF THE YELLOW RIVER DELTA AFTER LAST GLACIAL MAXIMUM AND ITS ENVIRONMENTAL IMPLICATIONS

15万年左右黄河切穿三门峡后，建造了广阔的华北平原，并在其上频繁摆动入海，其中1000年以来年均入海沙量高达11～12亿t。入海泥沙的大量沉降，形成了众多古黄河三角洲，现代黄河三角洲形成于1855年。根据黄河三角洲YDZ1孔沉积粒度的垂向变化，结合AMS^14C测年数据和历史资料，分析了末次冰盛期后黄河三角洲潮滩的沉积信息及其沉积环境演变。结果表明，黄河三角洲潮滩沉积物类型主要有砂、粉砂质砂、砂质粉砂、粉砂和黏土质粉砂；从上而下各沉积层段之间的平均粒径①值和分选系数表现为减小-增加-战小的变化趋势，偏态和峰态表现为增加-减小-增加的变化趋势；沉积相序经历了泛滥平原相-河流相-三角洲前缘相-浅海相-潮坪相-河流相，这表明沉积动力环境表现为强（陆相）-弱（海相）-强（陆相）的变化过程。

The Yellow River is the sediment supplier for building up the vast Norht China Plain. It swings frequently on the plain and finaly pours into the Bohai Sea after the River cut through the Sanmenxia about 150 kaBP. The annual average sediment charge of the Yellow River into the sea reached （11-12）× 10^8t since 1 000 aBP, most of which deposited at the river mouth to form deltaic lobes, and the modern Yellow River delta was formed in 1855. According to the vertical variations in sediment grain size of the YDZ1- core of the Yellow River delta, in connection with the AMS14C dating and historical data, this paper ana- lyzed the sedimentary information and the evolution o{ sedimentary environment of the Yellow River delta after the last glacial maximum. The main types of sediment are sand, silty sand, sandy silt, silt and clayey silt. From top to bottom, the mean size and sorting coefficeint show trends from decrease to increase, then coming back to decrease, while the skewness and kurtosis exhibit contrary trends in a increase- decrease- increase pattern. The sequence shows a facies succession of flood plain facies, fluvial facies, delta-front fa- cies, shallow marine facies, tidal flat facies and fluvial facies from bottom to top. It means that the dynam- ic environment varied from strong （continental facies） to weak （marine facies）, then to strong （continental facies） again.