Pleistocene aragonite crust diagenesis mimics microbialite fabrics (Danakil Depression, Ethiopia)
Metadatos
Mostrar el registro completo del ítemEditorial
Elsevier
Materia
Pleistocene Aragonite crusts Stromatolite Diagenesis Microbialite
Fecha
2023-02-08Referencia bibliográfica
David Jaramillo-Vogel... [et al.]. Pleistocene aragonite crust diagenesis mimics microbialite fabrics (Danakil Depression, Ethiopia), Sedimentary Geology, Volume 446, 2023, 106341, ISSN 0037-0738, [https://doi.org/10.1016/j.sedgeo.2023.106341]
Patrocinador
Swiss National Science Foundation (SNSF) 200021_163114; SNSF Ambizione 154810Resumen
Fibrous aragonite crusts occur in two consecutive Pleistocene successions in the Danakil Depression (Afar,
Ethiopia). Lateral transitions between pristine and altered fibrous aragonite crusts document changes in texture
associated with diagenesis. Crusts formed as essentially abiotic seafloor precipitates at the transition frommarine
to evaporitic conditions. Diagenesis started with the dissolution of aragonite fans at the interface between single
fans in non-laminated crusts and along lamination planes in isopachous, irregular, or crudely laminated crusts.
Incomplete dissolution resulted in the development of secondary porosity within amatrix of undissolved aragonite
fibers. Subsequently, the porosity was filled with calcite that systematically encased remaining aragonite
crystals. This was followed by the dissolution of remnant aragonite fibers, producing a network of elongated
inter- and intracrystalline pores that were eventually filled with low-Mg calcite. The stepwise substitution of
fibrous aragonite by low-Mg calcite resulted in sparry, sparry-cloudy, sparry-micritic (including clotted micrite),
and peloidal textures, which obscure the fibrous nature of the original deposits. Stable C- and O-isotope compositions
suggest that early diagenesiswas driven by meteoric and evaporative fluids. These observations unequivocally
demonstrate destructive diagenesis, resulting in secondary textures, which mimic micritic and grumous
(peloidal and clotted) textures associated with sparry microfabrics.
This suggests that these textures, classically interpreted as primarymicrobial precipitates and used as evidence of
biogenicity in ancient microbialites, might be diagenetic products in some cases, even though at some stage,
microbial processes and/or degradation of organic matter could have been involved in the diagenetic process.