Ichnology of tidal ravinement omission surfaces in siliciclastic transgressive deposits from the Puesto El Moro formation (Upper Cretaceous), Southern Patagonia, Argentina

Abstract

Omission surfaces represent a gap in the sedimentary record on a particular environment, constituting an important tool for basin analyses. Nevertheless, not always these surfaces constitute key sequence-stratigraphic surfaces, and their correct interpretation is highly important for the recognition of genetically related strata. Documentation and interpretation of ichnological data from stratigraphic surface can refine the sedimentological model. The Puesto El Moro Formation (lower Upper Cretaceous) in the Austral-Magallanes Basin, southern Patagonia (Argentina), shows excellent examples of several omission surfaces stacked during a transgressive context associated with the beginning of the foreland stage. Each of these surfaces, interpreted as Tidal Ravinement Surfaces, contain Thalassinoides isp. and Sinusichnus isp., which represent opportunistic colonization by crustaceans into a predominantly firm substrate. In this case study, the vertical recurrence of substrate-controlled trace fossil suites is the result of high-frequency repeated coastal conditions during the transgression; the associated surfaces, which have limited lateral extension, have low potential for correlation at basin scale.