THE K T BOUNDARY IN SOUTHWESTERN PETEN (G UATEMALA)/

In Peten, between shallow carbonate platforms with larger foraminifers , dasycladals and rudists of Maastrichtian age and limestones, marls a nd clays with planktonic foraminifers and calcareous nannofossils of D anian age, outcrop breccias with limestone clasts of shallow carbonate platform as in the El Caribe section or an iron crust as in the El Ce ibo section. The formation of these breccias ha been much debated: tsu nami of the boundary K/T meteorite on the Yucatan versus sea-level dro p near the K/T boundary. The El Ceibo section gives data that suggest that these breccias are coeval not with the impact wave, but with tect onic events.