Identification of tsunami deposits and liquefaction features in the Gargano area (Italy): paleoseismological implication

P. M. De Martini, P. Burrato, D. Pantosti, A. Maramai, L. Graziani, H. Abramson


The Gargano region (Southeastern Italy) was hit by a M = 6.8 earthquake and inundated by a subsequent tsunami
in 1627. To better define the hazard in the region, we searched for evidence of this and prior earthquakes in
the geologic record. We identified potential earthquake-related liquefaction features and tsunami deposits in the
stratigraphic sequences of the marsh areas both north and south of the Gargano promontory. We recognized clear
liquefaction features and possible tsunamigenic sands that can be related to the 1627 seismic event in irrigation
ditch exposures and gouge cores along the Northern Gargano coast. In total, six potential tsunami sand deposits
have been recognized in two areas located close to the northern and southern coasts of the Gargano promontory.
However, ambiguous evidence comes from the paleontological analysis of these sands. Although fragments of
marine shells have been found in the coarser portion of the sand samples, foraminifera and ostracods assemblages
are typical of brackish water condition. Radiocarbon dating of three of these deposits from the Northern
Gargano coast, near the town of Lesina, suggests an average recurrence interval of 1700 years for tsunami events
in this area. Assuming that all the paleotsunamis are related to the same seismogenic source responsible for the
1627 earthquake, this average recurrence interval may be typical for that source. Radiocarbon dating of three
sand layers observed on the southern coast, close to the city of Manfredonia, suggests that the average recurrence
time for violent sea inundation there is about 1200 years.


tsunami;liquefaction;Gargano;1627 earthquake

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X