Existing quantitative methods for biostratigraphic dating and correlation commonly ignore one of the key strengths of the microfossil record—relative abundance data. In this study, we present a maximum likelihood-based biostratigraphic method that demonstrates how microfossil abundance can be used in the stratigraphic placement of isolated samples. Precise correlation and dating of isolated paleontological samples is not possible with current methods, which are primarily intended for the alignment of longer stratigraphic sequences. In contrast, the probabilistic approach provided by likelihood analysis results in sample age estimates with defined confidence intervals. Therefore, all the uncertainties inherent in our age assessment (resulting from small sample sizes, incomplete sampling, imperfect knowledge of stratigraphic distributions, lack of taxonomic resolution of biostratigraphic data, and underlying environmental, paleogeographic, and sedimentologic processes) are explicit in our results. We conclude with a field test of the method, from data collected from an oil well from the Catatumbo Basin, Colombia, illustrating the use of our approach in a real-world case study and highlighting how our method could be generalized to a wide range of stratigraphic problems.