Morpho-structure and sedimentology of the Holocene Ebro prodelta mud belt (northwestern Mediterranean Sea)

Abstract

The Ebro “mud belt” is a Holocene prodeltaic deposit which has developed around, and southwestward from, the present Ebro Delta plain, covering most of the inner and middle Ebro continental shelf. Seismic-reflection profiles of this mud belt exhibit a complex sigmoid—oblique configuration. Top-set strata dip gently seaward to the 20 m isobath, and overly the fore-set beds which are exposed in up to 40–60 m water depth. Top-set and fore-set beds have mostly parallel and high continuity reflectors. Thin, acoustically transparent bottom-set beds are present at the base of the fore-set beds and extend to the distal edge of the prodelta (60–80 m water depth), where they overly relict transgressive sand deposits. There is no evidence of mass movement. The suspended load discharged by the river is mainly transported alongshelf by advective processes. This dynamics produces thin clinoform deposits that extend alongshelf for tens of kilometres. Mud belt deposition began about 10,000–11,000 years BP. Accumulation rate ranges from less than 0.5 mm y −1 on the seaward and southern edges of the deposit to about 2.5 mm y −1 near the present river mouth.