Paleontology and geology
Coastal plain and shallow sea environments dominated this region during the Tertiary. The land that would become Louisiana formed as river, lake, delta, and nearshore marine deposits formed land that extended out into the Gulf. The sea advanced and retreated several times during the Tertiary, producing a complex interfingering of marine and non-marine beds. But overall, the sea withdrew over the course of the Tertiary, and terrestrial environments developed further and further south into the Gulf of Mexico. This provided ample terrestrial environments for camels, mastodons, and other mammals. Some Tertiary gravels contain Paleozoic-age fossils of brachiopods and other marine organisms. These were eroded from older marine sediments deposited in the central part of the U.S. and carried by rivers and streams into Louisiana during the Tertiary and Quaternary.