杭州湾庵东浅滩现代沉积物中的生物遗迹

Biogenic traces in modern shoal deposits of Andong area,Hangzhou Bay

杭州湾庵东浅滩沉积物中发现有多种造迹生物,主要有蝼蛄、泥甲虫、宁波泥蟹、珠带拟蟹守螺、泥螺、弹涂鱼、蚂蚁和鸟类等,营造的生物遗迹主要为觅食迹、居住迹和爬行迹(爬迹、拖迹和鸟足迹)等。分析表明,浅滩不同亚环境的造迹生物及其遗迹的主要类型和分布特征具有明显的差异性:(1)在潮上带植被茂密的草滩环境中,以层面上的生物觅食迹、居住迹和鸟足迹为主,造迹生物主要有蝼蛄、泥甲虫、蚂蚁和鸟类等,其中以蝼蛄的潜穴最为丰富。(2)在高潮滩的积水泥沼环境中,有大量近海喜盐植物,生物遗迹主要有宁波泥蟹的"J"形、"W"形和"Y"形潜穴、弹涂鱼的羽状爬迹、珠带拟蟹守螺在层面上营造的弧形、圆圈状的觅食迹和"C"形的条带状生殖迹。(3)在中、低潮间带的粉砂质环境中,以层面上珠带拟蟹守螺不规则的觅食迹为主。生物遗迹的分布与浅滩沉积底质沉积物粒度与含水量等特征密切相关。本研究不仅丰富了杭州湾浅滩沉积的新遗迹学研究,而且对古代潮汐沉积及其环境研究有重要的借鉴意义。

Various trace-makers have been found in the shoal deposits of Andong area, Hangzhou Bay,including mole crickets （Gryllotalpa unispina）,mud beetles （Coleptera）,mud crabs （Ilyplax ningboensis）, Cerithideopsilla cingalata, mud snails （Bullacta ）, mudskippers or amphibious fishes （Periophthalmua cantonensis）,ants and birds.The most abundant traces can be ascribed to Fodinichnia,＆amp;nbsp;Domichnia,Repichnia and Pascichnia.Analysis shows that significant variations in type and diversity of traces and their makers are present over the different shoal zonations.（1 ） The highly-vegetated supratidal flat is featured by the abundance of bird tracks,and feeding and dwelling traces of mole crickets,mud beetles and ants,in which the feeding burrows of mole cricket are the most common.（2） In the upper in-tertidal flat where a lot of halophilic plants dominate on the muddy substrates,the biogenic traces include the J-, W-or Y-shaped burrows by mud crabs, the pinniform crawling traces by mudskippers, and the arc-shaped,donut-shaped grazing trails and C-shaped reproduction traces by mud snails （Cerithideopsilla cingalata）.（3）In the silty substrate of the middle-lower intertidal zones,the biogenic traces are charac-terized by the irregular grazing trails of mud snails （Cerithideopsilla cingalata）on the bedding plane.It is also found that the distribution of biogenic traces is highly related to the grain sizes and water-saturation of the substrates.This study provides not only a neoichnological approach to tidal-flat sedimentary in the Han-gzhou Bay,but also a meaningful modern analogue for sedimentary facies and paleo-environmental inter-pretations of ancient tidal flats.