Nanotextures of aragonite in stromatolites from the quasi-marine Satonda crater lake, Indonesia - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 210

overgrowths on filamentous green algae thalli
(Fig. 1). These samples show a facies that was
named 'stromatolitic-siphonocladalean' and 'peloi-
dal zone' by Kempe & Ka´mierczak (1993) and

'Green-Algal Microbialite' by Arp et al. (2003).
This facies comprises a significant part of the
Satonda reef framework the bulk of which is com-
posed of marine stenohaline calcareous red algae

Fig. 1. Observation and compositional analysis of carbonate laminae in Satonda stromatolites. (a) Optical microscopy
image of the laminated circular overgrowths on filamentous green algae forming the framework of Satonda
stromatolites. Concentric dark (Mg - Si rich) and bright (aragonite) laminae can be observed. (b) Optical microscopy
image of one aragonite lamina at higher magnification showing striations parallel to the general direction of the
lamina accretion. The average distance between striations is around 1mm. (c) Secondary electron SEM image of the
laminae which have been slightly etched. The fibrous texture of the aragonite laminae as well as numerous striations are
visible. (d) NanoSIMS measurements of the Sr/Ca and Mg/Ca ratios along a 50-mm segment profile.