Published in "Sedimentology 66(2): 480–512, 2019" which should be cited to refer to this work. Pleistocene sea-floor fibrous crusts and spherulites in the Danakil Depression (Afar, Ethiopia) DAVID JARAMILLO-VOGEL*, ANNELEEN FOUBERT*, JUAN CARLOS BRAGA†, JEAN-CHARLES SCHAEGIS*, BALEMWAL ATNAFU‡, BERNARD GROBETY* and TESFAYE KIDANE‡§ *Department of Geosciences, University of Fribourg, Ch. Du Musee 6, 1700 Fribourg, Switzerland (E-mail:
[email protected]) †Departamento de Estratigrafıa y Paleontologıa, Universidad de Granada, Campus Fuentenueva, 18002 Granada, Spain ‡School of Earth Sciences, Addis Ababa University, Addis Ababa, Ethiopia §School of Agricultural, Earth and Environmental Sciences, College of Agriculture, Engineering and Sciences, University of Kwazulu-Natal, Westville Campus, Durban, South Africa ABSTRACT Pleistocene fibrous aragonite fabrics, including crusts and spherules, occur in the Danakil Depression (Afar, Ethiopia) following the deposition of two distinc- tive Middle and Late Pleistocene coralgal reef units and pre-dating the precipita- tion of evaporites. Crusts on top of the oldest reef unit (Marine Isotope Stage 7) cover and fill cavities within a red algal framework. The younger aragonite crusts directly cover coralgal bioherms (Marine Isotope Stage 5) and associated deposits. Their stratigraphic position between marine and evaporitic deposits, and their association to euryhaline molluscs, suggest that the crusts and spher- ules formed in restricted semi-enclosed conditions. The availability of hard substrate controls crust formation with crusts more often found on steep palaeo- slopes, from sea level up to at least 80 m depth, while spherules mainly occur associated with mobile substrate. Crusts reach up to 30 cm in thickness and can be microdigitate, columnar (branching and non-branching) or non-columnar, with laminated and non-laminated fabrics.