Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

126 PATA Days 2024 bedding, 2 – Ball and pillow, 3 – Load cast, 4 – Flame structures, 5 – Deformed lamination and 6 – Pseudonodules. Below we will provide a detailed description of each of these structures. Ductile deformation structures • Loop bedding The lower segment of the outcrop displays loop bedding structures, characterized by elongated, slender loops or chain- like links formed from claystone within unit 1. These structures, evenly spaced at one-meter intervals and occasionally clustered. Situated in the lower and middle portions of stratigraphic unit 2, predominantly consisting of 58 cm thick mudstone with parallel lamination. Notably, the loop bedding structures exhibit variations in diameter, ranging from 80 to 150 cm (Fig. 2b). • Ball-and-pillow Ball-and-pillowmorphology structures were observed in the middle part of the outcrop. These structures exhibit symmetrical concentric balls with curved or deformed laminations, conforming to their rounded shape both externally and internally (Fig. 2c). Composed primarily of claystone, the interior and surrounding lithology share a similar granulometric composition. Located predominantly at the top of stratigraphic unit 5, which is a layer of claystone. The ball- and-pillow structures are entirely enclosed and isolated within the claystone, losing continuity with the upper strata. Fig.1: Location of the analyzed outcrop, named Santa Rosa. (a) Regional location within the geodynamic context of Ecuador. The gray polygon represents Ecuador within South America's geodynamic context, where the Nazca plate moves at a rate of ~55mm/year and the South American plate at ~30mm/year; the outcrop in Figure 1c is highlighted in red. (b) Position within the Napo province. The dark gray polygon delineates the Napo province, with main active faults indicated by lines (Adapted from Costa et al., 2020). (c) Map showing primary faults and distribution of surface earthquakes within the sub-Andean zone (obtained from IGEPN, 2022). Colors denote seismic event magnitudes; black lines represent active surface faults with kinematics, the red star denotes the outcrop and black squares indicate nearby towns.