Biogenic Traces In The Modern Sedimentary Of The South Bank Of Hangzhou Bay

The modern biogenic structures as their morphology, trace makers of burrows, tracks, trails and traces made by extant organisms in the Cao'e River, odern tidal flat and fieldwork sites in Andong area and the beach of thousand step sand in Putuo island are describe. Summed up the composition and distribution characters in different sub-environments and micro-environments of the Hangzhou Bay. The relationships between the biogenic structures and their substrate, sedimentary environment, ecological environment are analyzed. Comparison and analyses modern biogenic structures in Hangzhou Bay. Spatial variations in types, abundance and diversities of traces and their makers are obvious over the different tidal-flat zonations.(1) Species distribution and quantity of bay are obvious different from the bottom of the bay to the bay mouth.(2) The modern biogenic structures in the Hangzhou Bay are described. It included 15 kinds of trace makers;(3) By means of experiments, the distribution of the modern biogenic structures is affected by the substrate property(as grain-size, the relative water content, salinity), sedimentary environment and ecological environment;(4) Various trace-makers have been found at the Andong tidal flats in the Hangzhou bay, including mole crickets, mud beetles, sea cockroachs, hot taps, mud crabs,cerithideopsilla cingalata,mud snails, mudskippers or amphibious fishes,ants, scopimera globosas, grubs and birds. Biogenic traces are dominantly composed of the J-shaped,U-shaped and Y-shaped burrows by mud crabs, pinniform shaped crawling traces by mudskippers, and the V-shaped, donut-shaped grazing trails and the C-shaped reproduction traces by mud snails.(5) Trace community distribution influenced by sediment of the environment conditions, the influence factors including the nature of the underlying, water depth, salinity, oxygen and energy as well as the deposition rate and deposit emergency disturbance, organic matter content and food supplies, etc. This study provide not only new methods and scientific contents to the tidal-flat sedimentary in the Hangzhou Bay, but also a meaningul modern analogue for facies and paleo-environmental interpretations of fossil tidal flats.