黄河三角洲潮坪环境现代生物遗迹与物化条件的响应关系

The Response Relationship between Biogenic Structures and Physicochemical Stresses of the Yellow River Deltaic Tidal Flat

黄河三角洲潮坪在沉积过程中长期受各种物理化学环境因素的影响,而其中生物遗迹特征可以高精度高灵敏度地反映环境的变化。运用沉积学和遗迹学方法,全面系统地研究遗迹的分布、分异度、行为生态学、形态变化及扰动率等特征,分析其与三角洲潮坪沉积过程中受波浪和潮汐作用影响下物理化学因素之间的响应关系。结果表明:1)黄河三角洲潮坪沉积中生物遗迹的分异度、丰度与沉积物的粒度、沉积速率、水动力和总有机碳(TOC)含量分布基本一致,但盐度和浑浊度影响了生物遗迹分布的种类。造迹生物种类相同的情况下,盐度影响了生物的潜穴直径和扰动率,盐度相同的情况下,浑浊度影响生物潜穴的数量;2)潮上带生物遗迹分异度整体呈对称均衡分布,但在粉砂质底层区域和多条潮道的汇聚处,生物遗迹的丰度和分异度最高;3)潮间带整体生物遗迹分异度和丰度与粒度变化不大,但在TOC含量相对较高、水动力相对较弱、沉积速率低、盐度降低的几条潮道汇聚处,生物遗迹丰度和分异度达到最高;4)潮下带生物遗迹丰度和分异度整体呈对称均衡分布。该研究将补充、完善和修正已有的三角洲潮坪遗迹学和现代潮坪沉积学资料,并对高精度地解释、修正古潮坪环境起到一定的作用。

Depositional processes in the Yellow River deltaic tidal flat create a variety of physicochemical stressful conditions that are sensitively and directly reflected on biogenic sedimentary structures.According to sedimentology and ichnology methods to comprehensive and elaborate research the biogenic distribution and heterogeneity of traces,behavioral ecology,morphology change,and disturbance rates.These methods provide a significance way to identify and interpret the sedimentary environment.The study aims to analyze the response relationship between biosedimentary structures produced by organisms and the distinct physicochemical parameters of the depositional processes for a deltaic tidal flat,which are influenced by wave and tidal interaction.In addition,these physicochemical parameters that impact the neoichnological character of the Yellow River Delta tidal flats include grain size,sedimentation rate,energy conditions,substrate consistencies,water turbidity and salinity,and total organic carbon(TOC) cotent.The data analysis indicated that the diversity and heterogeneity of the biogenic sedimentary structures are basically consistent with hydrodynamics,sediment caliber,deposition rate,and TOC distribution of sediments.However,turbidity and salinity influence the categories of biogenic sedimentary structures.In the case of the same species of biogenic sedimentary structures,salinity affects the diameter and disturbance rate of burrows;in the case of the same salinity,turbidity affects the number of burrows.The study area is subdivided into the supratidal,intertidal,and subtidal zones.In the supratidal zone,the distribution of biogenic sedimentary structures is symmetrical,whereas the greatest diversity and abundance of biological remains appear in the area of the silty-dominated deposits and the convergence of multiple tidal channels.After accounting for grain-size,which is impacted by the diversity and abundance of biological remains in the intertidal zone,the highest development of diversity and abundance at the convergence of several tidal channels were controlled mainly by the relatively higher TOC content,the weaker hydrodynamics,generally low deposition rate,and reduced salinity.Burrow density and size for the horizontal trace distribution increase in the seaward direction.The distribution and abundance in the subtidal zone are similar to the supratidal zone,which are symmetrical and balanced overall.This study would supplement and improve the neoichnological and sedimentological data of modern tidal flats and plays an important role in the interpretation and correction of the ancient tidal flat environment with high precision.