Fig. 3

Stratigraphic context of the San Gregorio Formation. A Generalized section of Northward Chiguaje Hill polygonal (NCH) (see Fig. 1); a section with more detail of the NCH is presented in Additional file 1. B Norte Casa Chiguaje locality section. C San Gregorio Oeste del Pueblo locality section. The “8C_A-C” and “10C_E-F” referred in the NCH section correspond molluscan shell samples used for ⁸⁷Sr/⁸⁶Sr analyses (see Additional file 5). Fm. Formation, Mb. Member, R.S Río Seco Member