Integration of sedimentological and ichnological analysis on the wave-dominated deposits of The Maastrichtian Calafate Formation, Austral-Magallanes Basin, Argentina

ODINO-BARRETO, A. LORENA; RICHIANO, SEBASTIÁN; GINGRAS, MURRAY K.; POIRÉ, DANIEL G.

MARINE AND PETROLEUM GEOLOGY

ELSEVIER SCI LTD

Año: 2020 vol. 121

0264-8172

An integrated study combining sedimentological and ichnological data has been conducted in the lower wavedominateddeposits of the Calafate Formation. The study aimed to assess the variation in fair-weather andstorm processes, tidal flux, and the coast configuration to correctly constrain sedimentary dynamics in complexdepositional systems.The wave-dominated deposits comprise foreshore to upper shoreface (FA1), middle to lower shoreface (FA2)and offshore-transition deposits (FA3) moderately affected by storms. In FA1, the most proximal strata containMacaronichnus isp. and occur within the foreshore, while the upper shoreface shows an increased ichnodiversityassociated with the occurrence of the archetypal Skolithos ichnofacies evidencing heightened energies of theupper shoreface. FA2 display a fair-weather community assigned to the proximal Cruziana ichnofacies that showsa wider range and variability of living strategies, and a storm-related community represented by opportunisticcolonizers which produced burrows assigned to Ophiomorpha nodosa. The monospecific occurrence of Thalassinoidesisp. at the top of FA2 in CC02P section is assigned to the Glossifungites ichnofacies, developed on afirmground and autogenic surface. The ichnoassemblage in FA3 is attributable to the transitional Skolithos-Cruziana ichnofacies, that exhibits a slightly reduced diversity of the fair-weather community and a sparsebioturbation.The distribution and the general characteristics of the ichnological assemblages are consistent with depositionin fully marine conditions. The bioturbation intensity, trace-fossil diversity, maximum penetration, and burrowsize distributions indicate fully oxygenated and clear waters, normal-marine salinity conditions, abundance andaccessibility of food, and continuous and moderate sedimentation. Nevertheless, the ichnological signature inFA3 is related to minor physico-chemical stress produced by strong tidal currents originated during the southwardexpansion of the Magallanes embayment.