In contrast to the 2 to 3 cm thick clay layer found worldwide, the KT boundary in the Gulf of Mexico region and in Haiti is composed of much thicker coarse clastic deposits. Sand beds indicative of high energy deposition at the KT boundary at Brazos River, Texas, have been interpreted to be the result of a major disturbance of the depositional environment, such as a tsunami approximately 50 to 100 meters high [ Bourgeois et al., 1988]. At Beloc, in Haiti, the KT boundary is interpreted as an ejecta layer probably deposited and reworked on a submarine slope [ Carey et al., 1993]. In Northeastern Mexico the KT boundary is formed by as much as three meters of coarse clastic layers in stark contrast with the deep water fine marls deposited above and below it [ Smit et al., 1992; Alvarez et al., 1994]. The KT layers consist of a basal unit containing impact ejecta (shocked quartz and spherules), overlained by a coarse laminated sandstone derived from coastal areas, and topped by ripples of fine sand and Ir-rich silts [ Smit et al., 1992; Claeys et al., 1993]. This succession containing impact markers at its base and at its top is interpreted as being rapidly deposited (within a few days) by a series of tsunami waves caused by the nearby Chicxulub impact [ Alvarez et al., 1992; Smit et al., 1992; Smit et al., 1994].
Alternative views explain these KT clastic beds as the result of turbidity currents generated by high energy waves related to the Chicxulub event [ Bohor and Betterson, 1993; Bohor, 1994] or as a long time (> 100,000 years) succession of incised valley fill deposition associated with the Late Maastrichtian sea-level lowstand [ Stinnesbeck et al., 1993].