The K-Pg Río Cangrejo layer in central Cuba: An ejecta-rich backwash deposit over the Caribbean volcanic terrane.

The Chicxulub meteorite impact produced varied deposits at the Cretaceous-Paleogene (K-Pg) boundary, with effects that enveloped the entire planet. In the Gulf of Mexico and Caribbean region, stratigraphic sections of the K-Pg Complex Clastic Unit (CCU) are being described from different marine environments. This work provides the characterization and formal definition of the Río Cangrejo Layer, a new K-Pg boundary lithostratigraphic unit identified in the Cabaiguan piggy-back basin of central Cuba, which originated upon the Caribbean Volcanic Arc terrane. The new unit is formed by the K-Pg CCU, exhibits several amalgamated layers with marked cross-bedding, and is significantly rich in altered ejecta spherules. Three main intervals were identified in the sequence: a basal grain flow deposit, a middle interval with unidirectional tractive current structures, and an upper level rich in spherules. The foraminiferal association, petrography, and sedimentology of this CCU confirm its origin linked to the Chicxulub impact. The unit records the action of tsunamis and is interpreted as a backwash deposit that eroded the Maastrichtian carbonate platform situated atop the Cretaceous volcanic rocks. The definition of this unit is of special importance for the regional and global stratigraphic correlation of the K-Pg event, particularly in the Caribbean context. The type outcrop, of exceptional scientific value and accessibility, is proposed as a geosite for its conservation, research, and public dissemination concerning the global K-Pg event.