The fossil remains of marine mollusks have played a pivotal role in the understanding of stratigraphy around the world. Recently, Palaeontologia Electronica (PE) authors Lloyd Glawe, John Anderson, and Dennis Bell published an article about their study of microscopic mollusk shells from a set of nearly continuous cores from the Paleogene of Louisiana.
The authors state, "the mollusk shells were available in an unusually long subsurface core representing 6 million years of nearly continuous, deltaic deposition." The subsurface cores spanned over 650 meters in length and are estimated to extend from ~60 Ma to ~54 Ma, which allowed the authors to modify the known stratigraphic range for certain species of marine mollusks from the Gulf Coastal Plain of the United States.