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

tidal activity, storm waves, tsunamis, and seismic shocks, with the latter being particularly pertinent for paleoseismological studies. The wide array of structures and triggering mechanisms presents challenges for researchers in unraveling their origins, leading to ongoing studies and discussions (Shanmugam, 2017). In Ecuador, there has been limited exploration of SSDS, with scant reports in Holocene fluvio-lacustrine deposits and Pliocene volcaniclastic deposits, primarily linked to seismic activities (Hibsch et al., 1996, 1997). This study focuses on SSDS within the Tena formation of Upper Cretaceous, situated in the Ecuadorian sub-Andean region. The formation comprises sandstone, red siltstones, and claystones deposited in transitional to continental environments (Gaibor et al., 2017). Despite earlier publications on the Tena formation lacking references to SSDS, recent investigations reveal a diversity of these structures in the Ecuadorian Amazon (Cornejo, 2022). The objective of this research is to enhance understanding of SSDS deformation mechanisms and triggering mechanisms. The study involves a thorough description of various SSDS types and the interpretation of potential triggering mechanisms. This research holds significance in advancing knowledge about sedimentary structures in the region and their implications for Cretaceous Geodynamics evolution. METODOLOGY We conducted an examinationof anoutcrop along theTena-Puerto Napo Road, perpendicular to the active Porotoyacu fault (Fig. 1). This outcrop will be referred to as Santa Rosa. Our thorough documentation encompassed sedimentary, stratigraphic, and structural characteristics. Employing the coseismic stratigraphy approach, we identified and characterized SSDS, adhering toTuttle (2001) methodology and classifying them based on Rodrı́guez- Pascua et al. (2000) and Montenat et al. (2007). In the process of estimating paleoearthquake magnitudes, we took into account the dimensions and spatial distribution of the SSDS. RESULTS During our observations at the Santa Rosa outcrop, we have identified a diverse range of SSDS exhibiting various sizes and morphologies (Fig. 2a). These SSDS were found within 5 of the 11 units we studied and have been categorized based on their rheological behavior following Montenat et al. (2007) classification. Within the ductile structures category, we identified the following: 1 - Loop