Conodont color (CAI) versus microcrystalline and textural changes in upper triassic conodonts from Northwest Germany

Summary Scanning Electron Microscopy on conodonts from the Middle Triassic “Trochitenkalk” from Northwest Germany with CAI values ranging from 1 to 5 revealed structural alterations during progressive diagenesis. Conodonts with low CAI values of 1.5 already show syntaxial recrystallization of apatite on the conodont surface. Aggrading crystallization of the internal structure occurs in conodonts with CAI=5. The usually short-prismatic and blocky syntaxial crystallites become increasingly longer and an overall increase in crystallite size takes place. Conodonts from the telemagmatically heated sediments overlying the intrusive body of the Vlotho Massiv are often corroded, i.e., they have pocked, frosted to pitted surfaces with dolomite rhomb overgrowths, indicating contact with ascending dolomitizing brines.