TRACE FOSSIL ASSEMBLAGES FROM MIDDLE SILURIAN BAY (ESTUARINE) SEDIMENTARY ENVIRONMENTS IN THE HANSHAN AREA, ANHUI

Three trace fossil assemblages have been recognized in the estuarine deposits in the Middle Silurian Fentou Formation,Hanshan area,Anhui.
(1) The Protopaleodictyon assemblage mainly consists of Protopaleodictyon submontanum, Acanthorhaphe sp., Planolites sp. 1 and Gordia cf. molassica, and may be explained to be formed in a subtidal estuarine environment.
(2) The Arenicolites assemblage is made up of Arenicolites sp., Skolithos sp.,Thalassinoides sp., Planolites sp. 1 and irregular diagonal burrows as well as bioturhation structures, associated with some body fossils including the braehiopods Lingula, gastropods Orthonota, Hormotoma and Ecculiomphalus, and trilobites Coronocephalus, and is interpreted to be originated in a muddy-sandy coastal estuarine environment.
(3) The Chondrites assemblage is characterized by high-branched burrow systems including Chondrites furcatus and C. arbuscula, and contains a few of Planolites. It is an assemblage of high abundance and low diversity,and associated with some body fossils including the brachiopods Striispirifer,trilobites Coronocephalus, gastropods and bivalves and others, Which may serve to represent a locally restricted oxygen-deficient subtidal estuarine sedimentary environment.