The mechanisms of soft-sediment deformation structures(SSDS)in the Precambrian Dengying Formation in the northern Sichuan Basin remain poorly understood.This study presents a compre-hensive analysis of these structures in the Guangyuan area,examining their characteristics,distribution,and origins through field outcrop studies.The results indicate that these deformation structures,which are predominantly located in the middle to lower strata of the third member of the Dengying Formation,are composed of grey-white thin-layered limestone and purplish-red to grey-green thin-layered mudstone.The identified structures include liquefaction veins,convolute folds,breccias,and intrastratal faults,which are primarily observed in sediments from shallow,low-energy,aquatic environments.These deformations are closely linked to a combination of cyclic shear stress and stratigraphic pressure,suggesting recurrent ancient seismic activity as a key contributor.The finding of two distinct seismic liquefaction sequences sug-gests a minimum of two significant seismic events within the Member 3 of the Dengying Formation.It is fur-ther inferred that there was a period of intensive tectonic activity during the deposition of the member 3 of the Dengying Formation in the northern Yangtze Craton,and the seismic activity seemed to be related to the extension of the Late-Tongwan Movement in the rift.
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