Stromatlites, tufas and travertines of El Morro section: Deposits related to the first marine incursion in the Santa Rosalía Basin, Baja California Sur

Abstract

In this work, we report the facies analysis of the Basal Marine Limestone deposited during latest Miocene in the southeastern part of the Santa Rosalía basin, Baja California Sur. The Basal Marine Limestone constitutes the lower member of the Boleo Formation deposited during the proto-Gulf of California stage. In one of the best exposed sections in the basin, called El Morro, the Basal Marine Limestone is a 1 to 6 m thick deposit overlying the volcanic rocks of the Comondú Formation, and is constituted by travertine, tufa and stromatolite facies. Travertine facies were deposited in a fluvial environment, which laterally passes into a coastal marsh environment represented by the tufa facies; both facies are covered by stromatolite facies of a shallow-water intertidal environment. The change in the depositional environment indicates a transgression that is interpreted as the first marine incursion related to the opening of the Gulf of California.