Search the Community

Placement of terrestrial formations in the late cretaceous of North America as been constantly evolving and in October 2016 Denver Fowler a Paleontologist at the Museum of the Rockies published a very extensive paper on the subject and updated most units. This is very important when it comes to understanding dinosaur evolution and aids in describing species. This paper is in the process of going through peer review so is subject to change. Fowler DW. (2016) A new correlation of the Cretaceous formations of the Western Interior of the United States, I: Santonian-Maastrichtian formations and dinosaur biostratigraphy. PeerJ Preprints 4:e2554v1https://doi.org/10.7287/peerj.preprints.2554v1 The paper is pretty technical but all of the data is found in this excel file (supplemental information) which is a massive high-resolution stratigraphic chart for all of the formations from the late cretaceous of North America. It's nice to see it all laid out and a great reference source. https://doi.org/10.7287/peerj.preprints.2554v1/supp-1 To make it easy I've broken the chart apart so you can easily see most important dinosaur formations Texas The biggest change came with our understanding the Aguja and Javelina Formations of Texas part of the Tornillo group. The study indicated that the Aguja Formation deposits are only Campanian in age and that the Javelina Formation does not extend into the end of the Cretaceous. Very important when trying to describe species in those formations. Sellers have been comparing the Aguja to the Judith River in Montana well there is a correlation but its deposits are much younger that JR. Eastern Montana, N. Dakota, S. Dakota and Wyoming What I found interesting is that the Hell Creek is much older in Montana than in the adjacent states. The other interesting observation that can been easily be seen on these charts is that the how short a time frame the deposits of the Hell Creek/Lance formation are compared to the other major dinosaur formations. Central Montana Two Medicine and Judith River Formations are the two key formations in this locality Utah and New Mexico Utah depicted on the left and NM on the right Head North to Canada Alberta and Saskatchewan