Sedimentology and sequence stratigraphy of a tide- and wave-dominated coastal succession: the Cretaceous Goshoura Group, Kyushu, southwest Japan

Abstract

The Cretaceous, upper Albian-Cenomanian, Goshoura Group crops out in the Amakusa Islands, Kyushu, Japan. On the basis of facies analysis, the following coastal facies are recognized: shoreface-inner shelf (upper-middle shoreface, lower shoreface and inner shelf), tidal flat on the shoreface, estuary (bay-head delta, central basin, tidal flat and estuary mouth sand body) and fluvial (fluvial channel, flood plain and levee). The group records 4 transgressions and 3 regressions and consists of 4 depositional sequences composed mainly of transgressive and highstand systems tracts. The coastal palaeoenvironments are characterized by tide-and wave-dominated facies. Relative sea-level change estimated from this group is compatible with postulated eustatic sea-level fluctuation around the Albian-Cenomanian boundary.