Three-dimensional stromatolites from Maastrichtian–Danian Yacoraite Formation, Argentina: modelling and assessing hydrodynamic controls on growth patterns

Abstract

Stromatolites are biogenic sedimentary structures formed by the interplay of biological (microbial composition) and environmental factors (local hydrodynamic conditions, clastic inputand/or water chemistry). Well-preserved, three-dimensional (3D) fossil stromatolites arekey to assessing the environmental factors controlling their growth and resulting morphologyin space and time. Here, we report the detailed analysis of well-exposed, highly informativestromatolite build-ups from a single stratigraphic horizon within the Maastrichtian?DanianYacoraite Formation (Argentina). This study focuses on the analysis of depositional processesdriving intertidal to shallow subtidal stromatolites. Overall depositional architecture, externalmorphology and internal arrangement (mega, macro, meso and microstructures) of stromatolite build-ups were analysed and combined with 3D photogrammetric models, allowing us todecipher the links between stromatolite structure and tidal dynamics. Results suggest that external morphology and architecture of elongated and parallel clusters grew under the influence ofrun-off channels. The internal morphology exhibits columnar structures where the spacebetween columns is interpreted as recharge or discharge channels. This work supports thetheory that stromatolites can be used as a high-resolution tool in the assessment of waterdynamics, and provides a new methodological approach and data for the dynamicreconstruction of intertidal stromatolite systems through the geological record.