Discovery and geological significance of Upper Jurassic seismites in the Chiclayo region of Northern Peru

Seismites constitute a distinct category of sedimentary rocks that preserve soft-sediment deformation structures and associated seismogenic features, serving as critical stratigraphic archives for reconstructing paleoseismic events and regional tectonic evolution. Accurately identifying seismic sediment deformation structures and distinguishing these earthquake-induced features remains challenging. The Chiclayo region in northern Peru is located at the collision front between the Nazca and South American plates, a place with intense seismic activity. Comprehensive geological studies and section measurements were conducted in the Mesozoic La Leche Formation, identifying abundant brittle and soft-sediment deformation structures classified here as seismites. Five seismic events were determined. The paleogeographic environment of the La Leche Formation corresponds to a Late Jurassic littoral-shallow marine shelf within an initial back-arc basin. Synsedimentary fault activity between Peru’s northern coastal plain and western coastal range triggered basin margin collapses. This study provides new insights into Mesozoic plate tectonics in the eastern Pacific and modern seismic impacts on geological environments.