H. Takayama

Complex tsunami waves suggested by the Cretaceous-Tertiary boundary deposit at the Moncada section, western Cuba

The Moncada Formation in western Cuba is an 2-m-thick weakly metamorphosed complex characterized by repetition of calcareous sandstone units that show overall upward fining and thinning. The Moncada Formation contains abundant shocked quartz, altered vesicular impact-melt fragments, and altered and deformed greenish grains of possible impact glass origin. In addition, a high iridium (0.8 ppb)

Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba: An impact-related, high-energy, gravity-flow deposit

The Cacarajicara Formation of western Cuba is a more than 700 m thick calcareous clastic sequence that contains shocked quartz throughout, and spherules. Three members are recognized. The lower member consists of limestone and chert boulders, and disconformably overlies Cretaceous deep-water turbidite. It is characterized by: (1) a grain-supported fabric with only a small amount of matrix, (2) 5–15 cm, wellsorted clasts and occasional boulders, (3) reversely graded, discoidal or rectangular boulders showing a preferred orientation, (4) abundant shallowand deep-water carbonate clasts in a well-mixed fabric, (5) direct contact between adjacent clasts, and (6) hydrostatic deformation within a black clay matrix. This evidence suggests that the lower member was deposited under conditions of high-density and high-speed laminar flow. The middle member consists of upward graded, massive to well-bedded, homogeneous calcarenite. Unusual fluid-escape structures in the thick calcarenite suggest that this member formed by high-density turbidity suspension. The upper member consists of fine calcarenite mudstone; there is no evidence of bioturbation. We infer that it was deposited from a dilute, low-density suspension. Kiyokawa, S., Tada, R., Iturralde-Vinent, M., Masui, T., Tajika, E., Gracia Delgado, D., Oji, T., Nakano, Y., Goto, H., Takayama, H., and Rojas-Consuegra, R., 2002, More than 700-m-thick Cretaceous-Tertiary boundary sequence of the Cacarajicara Formation, western Cuba; Ejecta induced high-energy flow deposit, in Koeberl, C., and MacLeod, K.G., eds., Catastrophic Events and Mass Extinctions: Impacts and Beyond: Boulder, Colorado, Geological Society of America Special Paper 356, p. 125–144. S. Kiyokawa et al. 126 On the basis of these criteria, the Cacarajicara Formation is interpreted to be a single hyperconcentrated flow that was formed by high-energy and high-speed concentrated flow. The south-southeast paleocurrent direction suggests that this highenergy flow originated on the Yucatan platform and was triggered by the Chicxulub impact. We propose that a gigantic flow deposit was induced by earthquake-generated collapse of the Yucatan platform margin owing to ballistic flow from the Chicxulub impact.