Holocene sea-level change in the Bilbao estuary (north Spain): foraminiferal evidence

Benthic foraminiferal assemblages in Holocene sedimentary sequences of 4 boreholes from the Bilbao estuary (Bay of Biscay, northern Spain) have been analyzed. Estuarine indigenous and open-sea exotic foraminifera have been distinguished in order to interpret the environments of deposition (inter/supratidal sand dune and beach, low marsh, brackish intertidal, near-marine intertidal and fresh water) with varying amounts of open-sea influence. Two distinct upward-shallowing sequences, with a variable succession of environments depending on the distance to the estuary entrance, have been identified (similar to 8000 BP and similar to 3000 BP by comparison with other coastal deposits) and interpreted as showing episodic increase of sea level.