Amazing diatom preservation within dolomitised sediments of the late Neogene Pisco Formation, Peru

The late Neogene Pisco Formation of southern Peru is considered a Fossil-Lagerstätte (Seilacher, 1970) due to the abundance and beautiful preservation state of its fossil marine vertebrates (e.g., Esperante et al., 2015). However, the Pisco Formation strongly deserves the attribute of Fossil-Lagerstätte also for the amazing preservation state of several diatom specimens. Early diagenetic dolomite and associated minerals (i.e., Mn oxides) occasionally precipitated within the diatomaceous sediments characterising this formation (Gariboldi et al., 2015; Gioncada et al., 2016). In these instances, the filling of the diatom frustules by means of both micritic and drusy dolomite prevented them from being compressed by the sedimentary load. Thus, by means of SEM-SE images, beautifully preserved ultrastructures can be observed three-dimensionally. Furthermore, in those cases where silica has been dissolved, highly-detailed moulds let us have a glimpse of the diatom ultrastructures.