| In these cases, associated fluids could have modified the original isotopic signature, in particular when anhydrite was altered to secondary gypsum by surface waters. |
| Middle Triassic anhydrite and dolomite form a sequence of strong reflectors, as does Lower Cretaceous sandstone. |
| It is dominated by the deposition of calcite with minor pyrite, marcasite, barite, anhydrite and gypsum. |
| In particular the Hith, which is a well defined anhydrite in the west, passes laterally into dolomites to the east. |
| The fine-grained matrix consists chiefly of gypsum, although traces of anhydrite may be present. |
| At depths of less than 600m, gypsum forms rather than anhydrite because the gypsum-anhydrite stability boundary is crossed somewhere in this interval. |
