This paper presents a new, more detailed depth zonation of the northwestern Gulf of Mexico based on one of the best benthic foraminiferal data sets published. Fourteen depth-relatable zones defined at the generic level are recognized, six in the neritic interval, seven in the bathyal interval, and one restricted to abyssal depths. A test of the depth zonation using modern data shows that 90% of all samples are correctly classified. Slightly lower levels of reliability of classification for the bathyal versus the neritic interval are evident due to naturally occurring overlaps of generic depth distributions in the bathyal interval. The model was further tested using Neogene samples from two northwestern Gulf of Mexico wells. The results show that the new automated depth classification technique provides interpretations similar to depth estimates based on conventional approaches. Although it is difficult to compare new results against depth estimates rather than known depths, the new technique appears to provide considerable data that indicate where and when the possibilities of sea-level changes, subsidence, faulting, downslope transport, or downhole caving should be investigated.