Abrupt and massive influx of terrestrial biomarkers into the marine environment at the Cretaceous-Tertiary boundary, Caravaca, Spain

The mass extinction at the Cretaceous-Tertiary (K/T) boundary ca. 65 million years ago caused a major change in the nature and abundance of global life in Earth history. We present the first vertical high-resolution records of molecular distributions of n-fatty acids across the K/T boundary at Caravaca (Spain). The results reveal that the first basal thin horizon (0 to + 0.5 cm; 0 = K/T boundary) of the K/T boundary-clay layer showed as much as a ∼35-fold increase in concentrations of terrestrial long-chain n-fatty acids (≥ C ₂₀), representative of an eight-fold increase in mass accumulation rate, compared with the subjacent Cretaceous layers. Thereafter concentrations rapidly declined back to almost pre-boundary values within + 3 cm above the K/T boundary. The abrupt increase in supply of terrestrial organic matter into the marine environment at the K/T boundary could have been caused by an enhanced riverine flux, probably due to heavy rains associated with global warming, combined with enhanced fragments of terrestrial higher-plants withered by acid rain and/or by temporal darkness and cooling.