"海底陆源沉积扇" can be translated as "submarine terrigenous sedimentary fan" or "submarine continental-derived sedimentary fan".
"Submarine" indicates its underwater (sea bottom) location.
"Terrigenous" or "continental-derived" refers to the land-derived (陆源) origin of the sediment.
"Sedimentary fan" describes the fan-shaped depositional feature.
Both translations are accurate, with "submarine terrigenous sedimentary fan" being more concise and commonly used in geological literature.