Tsunami

Depth of water

Terrestrial - Continental shelf (0 - 140 m)

Circumstances

Sediments by tsunami. Sediments are formed by an event and sedimentary structures by biological activities and waves are not observed. Sediments are supplied from various circumstances such as lands, biological reefs, and gravelly beaches. Large scale tsunami may form Deep-sea tsunami deposit.

Sedimentary facies (Sediments)

Conglomerate, sandstone and sandy siltstone in ascending order. Conglomerate is clast-supported and is composed of boulders - pebbles. Sandy siltstone is rich in organic substances and black.

Sedimentary facies (Structures)

Tsunami sediments overlies with a sharp unconformity on the basement. Opposite current directions to land-side and ocean-side are formed by spilling waves and undertow waves. Hummocky cross-stratifications and dehydration structures are observed in sandstone. Imbricate structures are not observed in conglomerate.

Sedimentary facies (Fossils)

Organic substance rich zone is formed by the errosion of land. Shellfishes from different circumstances are co-exist and they are preserved in spite of clast-supported conglomerate as its deposition speed is fast.