The concentrations of redox-sensitive trace elements,such as uranium(U),vanadium(V),molybdenum(Mo),cobalt(Co),chromium(Cr) and rare earth elements(REE+Y) were determined in a given carbonate succession in the Gaoyuzhuang Formation(～1.56 Ga),which spans depths from outer shelf to intertidal,to explore the Early Mesoproterozoic ocean redox conditions.The values of the Zr-normalized redox-sensitive trace element concentrations and some relevant ratios show obvious changes from bottom to top in the succession.Samples from the outer shelf setting(M1 interval) demonstrate significantly enhanced values in Zr-normalized redox-sensitive trace element concentrations and relevant ratios(the peaks of Mo/U,V/Cr and Ni/Co ratios larger than 8,4.25,and 7,respectively).Authigenic framboidal pyrites were also found within oncolite-like carbonate concretions and surrounding host rocks in this interval.These all indicate a euxinic state in the outer shelf environment.Less enrichment of Zr-normalized redox-sensitive elemental abundances and a mild decrease in the values of geochemical ratios were present in the inner shelf environment(M2 interval)(the V/Cr and Ni/Co ratios fall into a range of 2.5 4.25 and 4 5,respectively),suggesting dysoxic conditions dominant in the inner shelf setting.Samples from the shallower subtidal and intertidal settings(M3 and M4 intervals) are mostly invariable with much lower values of Zr-normalized redox-sensitive elements and relevant ratios,with the V/Cr and Ni/Co ratios typically near or less than 2 and 5 respectively,indicative of oxic conditions in the high energy subtidal/intertidal zones.A remarkable negative Ce anomaly exhibited in the shale-normalized REE+Y diagram in the M4 interval may provide evidence in support of the hypothesis.Taken together,our results suggest a relatively shallow chemocline in the Early Mesoproterozoic ocean:the transitions between euxinic,dysoxic and oxic may occur in quiet-water outer shelf and highenergy subtidal zone,respectively.The presence of euxinic ocean bottom waters is compatible with low concentrations of seawater sulfate and reduced levels of atmospheric oxygen during this period.The extreme environmental conditions induced by these anoxic oceans could have been responsible for the delayed oxygenation of the biosphere and hindered the evolution of multicellular life. The concentrations of redox-sensitive trace elements such as uranium (U), vanadium (V), molybdenum (Mo), cobalt (Co), chromium (Cr) and rare earth elements (REE + Y) were determined in a given carbonate succession in the Gaoyuzhuang Formation (~ 1.56 Ga), which spans depths from outer shelf to intertidal, to explore the Early Mesoproterozoic ocean redox conditions. values ​​of the Zr-normalized redox-sensitive trace element concentrations and some relevant ratios show obvious changes from bottom to top in the succession.Samples from the outer shelf setting (M1 interval) shows significant enhanced values ​​in Zr-normalized redox-sensitive trace element concentrations and relevant ratios (the peaks of Mo / U, V / Cr and Ni / Co ratios larger than 8, 4.25, and 7, respectively). Authigenic framboidal pyrites were also found within oncolite-like carbonate concretions and surrounding host rocks in this interval. all of the auxiliary state in the outer shelf environment. Lessementment of Zr-normalized re dox-sensitive elemental abundances and a decrease in the values ​​of geochemical ratios were present in the inner shelf environment (M2 interval) (the V / Cr and Ni / Co ratios fall into a range of 2.5 4.25 and 4 5, respectively) suggesting dysoxic conditions dominant in the inner shelf setting. Examples from the shallower subtidal and intertidal settings (M3 and M4 intervals) are mostly invariable with much lower values ​​of Zr-normalized redox-sensitive elements and relevant ratios, with the V / Cr and Ni / Co ratios typically near or less than 2 and 5 respectively, indicative of oxic conditions in the high energy subtidal / intertidal zones. A remarkable negative Ce anomaly show in the shale-normalized REE + Y diagram in the M4 interval may provide evidence in support of the hypothesis.Taken together, our results suggest a relatively shallow chemocline in the Early Mesoproterozoic ocean: the transitions between euxinic, dysoxic and oxic may occur in quiet-water outer shelf and highenergy subtidal zon e,respectively. The presence of eugenic ocean bottom waters is compatible with low concentrations of seawater sulfate and reduced levels of atmospheric oxygen during this period. extreme environmental conditions induced by these anoxic oceans have been responsible for the delayed oxygenation of the biosphere and hindered the evolution of multicellular life.