The dolomite problem is one of the long-lasting problems in sedimentology.Magnesium is a major element in dolomite,and its isotopic compositions may be used to infer the dolomitization processes and sedimentary environments.In this study,we investigated the Mg isotope compositions of dolostones of the Albian Givat Yearim Formation and Soreq Formation of Albian from a section near Jerusalem,Israel.The carbonates are mainly composed of subhedreal to euhedral micritic dolomite without notable post-depositional diagenetic alterations.Carbon and strontium isotope compositions of the dolomite are consistent with the Albian seawater,suggesting that the dolomitizing fluid was sourced from the contemporaneous seawater.delta~(26)Mg values of dolomite cluster around-2.0 and do not show a clear correlation with depth.Combining Mg isotope and C-Sr isotope compositions of dolomite,it is suggested that the Mg supply from seawater for dolomitization was abundant,leading to Mg isotope equilibrium between seawater and dolomite.The rhythmic fluctuations in Na,Rb and SigmaREE contents in the dolomite sequence indicate responses of marine environments in a semi-closed basin to variations in regional paleo-climates and paleo-environments.By contrast,the relatively homogeneous dolomite delta~(26)Mg values across the sedimentary beddings imply that the regional climate and environment changes had limited impacts on Mg isotope compositions of seawater in local basins.Hence,for massive dolomite that was deposited in partly restricted basins,their delta~(26)Mg values likely still trace the Mg isotope composition of seawater in open oceans.