Effects of the quaternary sea-level change on the subsidence of a sedimentary basin: A case study of the Osaka Bay sedimentary basin, Japan

Surface load redistribution related to the Quaternary ice age may play an important role on the formation of Quaternary sedimentary basin. The basin is, in fact, formed by tectonic processes, but the Quaternary sea-level change may effect the subsequent evolution of the basin, in particular the subsidence history. Thus, the time-dependent surface load and its concomitant sediment loading produce a maximum crustal subsidence of about 100 m if the following conditions are satisfied: (1) Maxwell relaxation time of relatively thin lithosphere is less than the period of the glacial and interglacial cycle of 10⁵ yr; and (2) sediments are sufficiently supplied into the deformed areas by the water loading. Crustal subsidence of 100 m corresponds to about 20% for the depression of Osaka Bay basin during the past 1.2 Myr. These two conditions seem to be satisfied in active island-arcs with relatively weak lithosphere, and Osaka Bay sedimentary basin formed in the Quaternary is a suitable place to test this mechanism and/or to examine its effect on the crustal subsidence related to the sedimentary basin.