Reconstrucción paleoambiental del tránsito Cretácico-Terciario en La Lajilla (México) con foraminíferos

Abstract

Upper Maastrichtian and lower Danian sediments belonging to the Méndez and the Velasco formations, respectively, contain abundant foraminifera at La Lajilla section (northeastern México). Foraminifera! turnover across the K/T boundary indicate a catastrophic mass extinction of planktic foraminifera, whereas benthic foraminiferal extinction do not exceed 25%. The most important change in benthic foraminifera across the KIT boundary consists of a reorganisation of their communities: infaunal morphogroups were more affected than the epifaunal ones. Most of the infaunal species became extinct or temporally disappeared, due to the lack of nutrient supply toward the sea bottom floor. Infaunal percentages increased after the boundary, and indicate primary productivity recovery at La Lajilla during the lower Danian