Lateral lithological and compositional variations of the Cretaceous/Tertiary deep-sea tsunami deposits in northwestern Cuba

Lateral lithological, compositional, and grain size variations in the Peñalver Formation in northwestern Cuba, which is a Cretaceous/Tertiary (K/T) boundary deposit accumulated on the northwestern slope of the extinct Cretaceous Cuban arc and distributed over an area of 150 km, are examined in order to investigate the influence of a tsunami on the deep-sea bed. The lower part of the Peñalver Formation is composed of calcirudite containing grains derived from a shallow platform. It is considered to have been deposited by debris flows from the shallow carbonate platform triggered by the impact of the seismic wave. The upper part of the formation is composed of calcarenite to calcilutite hemipelagic to pelagic sediments. This has a distinctly different source to the lower part and is considered as having been formed under the influence of tsunami waves, judging from its regional homogeneity and the presence of serpentine lithic grains that were probably transported from central to eastern Cuba by a westward flowing water mass. An erosional surface between the two parts, together with sedimentary structures in the upper part indicative of current influence is more common with decreasing presumed depositional depth, which can be interpreted as stronger tsunami effect at the shallower depths. In addition, compositional and grain size oscillations that repeated >6 to 10 times are observed in the upper part, which may reflect repeated lateral injection of the sediments eroded from the shelf to the upper slope of the depositional basin by backwash of successive tsunami waves into the dense sediment suspended cloud that was formed by the first tsunami.