黄河三角洲地区全新世环境演化及海平面变化

ENVIRONMENT EVOLUTION AND EUSTATIC CHANGE OF HOLOCENE IN THE YELLOW RIVER DELTA

利用钻孔沉积物的粒度、矿物和元素地球化学测试信息,研究了黄河三角洲地区全新世沉积环境、气候及海平面的演化特征.研究表明,本区全新世环境演化分为6个阶段:①早全新世早期,10 900～9 100aBP,海平面较低,尚未淹没本区,为近岸氧化环境或氧化-还原过渡环境;②早全新世晚期,9 100～8000 aBP,海水上涨,本区时淹时退,为浅海或潮坪环境,生物钻孔发育;③中全新世主体,8 000～4 150 aBP,海平面快速上升,完全淹没,Fe2+/Fe3+介于0.739 5～1.912 3之间,为全新世中最高段,表明还原程度强、全球气候变暖(大暖期);④中全新世后期,4 150～2 850 aBP,海水有所下降,仍为浅海环境,Fe2+/Fe3+较高,多在1.0以上;⑤晚全新世,2 850～1 310 aBP,海平面进一步下降,本区时常暴露,其中2 150～1 310 aBP以还原环境为主,为潮下带,2 150～2 850aBP以氧化-还原过渡环境为主,为潮间带;⑥1855AD以来,海平面基本稳定,稍有上升,为现代黄河三角洲沉积时期.本区全新世至少存在5期冷热交替的旋回性气候变化.

Environment evolution and eustatic change of Holocene in the Yellow River delta were studied based on the data of grain size, mineral and element geochemistry of sediment. Study shows that environment evolution and eustatic change of Holocene in this area may be divided into 6 stages：① early stage of early Holocene, 9100-10900 aBP,when sea level was low and this area was an oxidizing environment or oxidizing-reducing transition environment;② late stage of early Holocene, 8000-9100 aBP, sea-level rising, submerged sometimes and exposed sometimes, offshore or tidal flat with lots of burrows;③ middle mid-Holocene, 4150-8 000 aBP, when sea level rose rapidly and Fe^2＋/Fe^3＋ value changed from 0. 7395 to 1.9123, showing strong reducing degree and global warm climate;④ late mid-Holocene, 2850-4150 aBP, sea-level falling, shallow sea with higher Fe^2＋/Fe^3＋ value;⑤ late Holocene, 2850-1310 aBP, fall- ing further, this area exposed sometimes;⑥1855AD-now, sea-level stable with a little rising, sedimenta- tion period of the modern Yellow River delta. There were 5 cold-warm cyclic climate changes at least in Holocene in the Yellow River delta.