This paper illustrates an example of the application of Sr isotope stratigraphy in refining interpretation of sections with equivocal stratigraphy derived from other techniques. Here we illustrate an example of Sr isotope stratigraphy that has clearly provided incorrect age information. We analyzed 61 samples from the La Luna Formation from the Las Hernández and San Pedro del Rio sections in the Venezuelan Andes. Biostratigraphy indicates that the section ranges from early Coniacian to early Campanian (Zapata et al., in press). Sr isotope ratios of the samples vary from 0.707507 to 0.708483, considerably higher than those for the age of the section determined by biostratigraphy (Table AT1; Fig. AF1). The range of Sr isotope values corresponds to the early Campanian-Miocene part of the seawater Sr isotope curve (McArthur et al., 2001). This range excludes all but the youngest interval predicted by biostratigraphy, indicating that the Sr isotope values are not those of original seawater. The samples are clay-rich and enriched in organic carbon (Table AT1). Residues after dissolution were dark colored, and it is likely that Sr isotope values were increased by inheritance of radiogenic Sr from noncarbonate components during recrystallization.