Search

This study assessed the influence of sediment and water redistribution in host sediments on peperite formation by examining the peperites at the boundary between Cretaceous lacustrine sedimentary successions and intruding dikes (D1 and D2). The peperite zones occur along the dike margins and consist of fluidal juvenile fragments, classified as Type A and Type B perperite zones based on lateral extent of the peperite zones. Type A peperite zone, the dominant type, exhibites a narrow distribution (<20 cm), whereas Type B peperite zone sporadically occurs along D1 with a wider width (<1 m). Type B peperite zone is laterally linked with clastic dikes. These dikes containi fluidal shaped dike fragments with jigsaw-fit textures, indicating syn-magmatic fluidization and the resultant formation of the clastic dike via heat transfer. During dike emplacement, the interaction between the host sediments and the intruding magma formed Type A along the margins. Simultaneously, the clastic dikes, composed of fluidized sediments and water, supplied additional water and sediments, enhancing magma-host sediment intermingling and leading to the wide lateral extent of Type B. Our findings demonstrate that sediment and water redistribution via syn-magmatic fluidization is crucial in peperite formation, influencing the initial processes of phreatomagmatic volcanism. [ABSTRACT FROM AUTHOR]

Post‐collisional processes cause uplift and exhumation of the overthickened crust together with the formation of sedimentary basins. To determine the influence of post‐collisional processes on sedimentation, we investigated the Early Mesozoic Munamdong Formation of the Yuljeon Basin in the Korean Peninsula, deposited immediately after the orogenic events caused by the collision of the North China Block and South China Block. Facies analysis shows that the Munamdong Formation was deposited in a streamflow‐dominated alluvial fan under tropical/subtropical climatic conditions. Vertically, the Munamdong Formation exhibits a fining‐upward trend with changes in stacking patterns, from highly amalgamated channel conglomerates to floodplain fines, indicating a progressive increase in the creation of accommodation space exceeding sediment supply. Moreover, the types of gravels in the conglomerate beds and the petrographic characteristics of the sandstones suggest that the sediments were supplied rapidly from nearby Precambrian high‐grade metamorphic rocks and Triassic post‐collisional plutons. These results indicate the supply of sediment from restricted sources, implying that the drainage basins did not widen even during intermittent quiescence of basin subsidence. We interpret the fining‐upward trend and uniform composition of sediments to have resulted from rapid uplift and exhumation of the orogenic crust, together with rapid tectonic subsidence, possibly aided by post‐collisional magmatism. This study shows that the Munamdong Formation reflects a close connection between surficial sedimentation and post‐collisional tectonic processes. This study will help to fill the gap of understanding between deep crustal processes and post‐collision sedimentation with insight into the Early Mesozoic tectonic environment of the East Asian continental margins. [ABSTRACT FROM AUTHOR]