Shallow marine tsunami deposits in Teluk Banten (NW Java, Indonesia), generated by the 1883 Krakatau eruption

Teluk Banten (TB) is a tropical shallow marine embayment with coral reef islands, close to the Krakatau volcanic complex. The 1883 Krakatau eruption generated a tsunami, which had a devastating effect on the neighboring coastal areas. The effects of the 1883 Krakatau eruption and the associated tsunami on the bottom sediments in TB are assessed using textural, compositional and 210Pb geochronological data. An important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra. The tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments. Coarse components in the tsunamite consist of locally derived material eroded from the seabed. Land-derived components are incorporated in the tsunamite only in close proximity to the coast. The tsunamite is thickest in localized areas of the central part of the bay. Along the northern open sea-facing slope of TB, the tsunamite is relatively thin (<7 cm thick) but well-preserved, as little post-depositional modifications have occurred. In the eastern bay area, recent erosion since the redirection of the Ciujung River in the 1920s has removed the Krakatau tsunamite. Along the west coast of TB, the only signature of the 1883 Krakatau eruption consists of tephra, and evidence for a high-energy event is lacking. Presumably, the western area was sheltered from the tsunami wave coming from the northwest. At the shallower stations with low accumulation rates, the tephra has been thoroughly mixed by bioturbation.