A nodular, iron-stained sponge bed occurs directly below two thin, un-named marl bands at Seaford Head in Sussex, and marks the sequence boundary (Grant et al., 1999). An interval containing two thin marls defines the lowstand systems tract, the top of which is a marly sponge bed (c. 6.3 m below the Michael Dean Flint) representing a transgressive surface (Grant et al., 1999). A nodular sponge bed marks the maximum flooding surface at the top of the transgressive systems tract in Sussex, and this is overlain by a highstand systems tract extending up to the Coniacian/Santonian boundary, marked by the Michael Dean Flint (Grant et al., 1999). Thin marl bands in the highstand succession of this sequence reflect a longer term relative sea-level fall (Grant et al., 1999).
GRANT, S F, COE, A L, ARMSTRONG, H A. 1999. Sequence stratigraphy of the Coniacian succession of the Anglo-Paris Basin. Geological Magazine, 136, 17–38.