Many diagenetic features formed syndepositionally in the Lower Jurassic carbonate rocks of the Central High Atlas, Morocco. Fungal and algal micritization, ghosts of aragonitic fringing cements and bored syntaxial rim overgrowths indicate subsea diagenesis. More common are vadose pisolite and perched silt, desiccated crusts. gravitational cements, interstitial evaporites and dolomitization of fenestrally laminated lacey crusts indicating subaerial diagenesis. Deeper burial resulted in final filling of pores with spatry, characteristically iron-rich cements. A paleohydrographic model relates diagenetic features to diagenetic environment and to changes in surface environments. The passage of sediments through different diagenetic environments is compared with the sedimentary record of transgression and regression deduced from other evidence and provides further control on the reconstruction of marine fluctuations within the basin of deposition.