The Hell Creek formation, as many of you know, was deposited in the North-Midwest United States (and some Southern parts of Canada) in the very end of the Cretaceous, as well as the very beginning of the Paleogene (but we're not going to talk about the Paleogene Hell Creek because we're focusing on the dinosaur-filled part!).
Most of the sediments from the formation appear to have been laid down by fluctuating channels and deltas, with rare swamp deposits in the easternmost portion, where it bordered the Western Interior Seaway. To the west were the newly formed Rocky mountains. The environment of Hell Creek, along with the contemporaneous Lance and Scollard formations, has been interpreted to have been subtropical, well-watered environments, with floodplains, swamps, coastal plain, and estuarine environments, with many rivers, streams, and lakes flowing through them (Lofgren, 1997; Breithaupt, 1997; Eberth, 1997). The vegetation was largely dominated by angiosperms such as laurels, magnolias, palms, sycamores, and beech trees, though conifers such as bald cypress and redwoods were present. Much rarer were the cycads (Only a single species - Nilssonia yukonensis) and ginkgos (One species - Ginkgo adiantoides).
As I've said before, the environment we will be using for our demo will be that of the dig site I will be going to in around one week. The T. rex appears to have died around an oxbow lake - a type of lake formed when a meander (a loop) in a meandering river is cut off from the rest of the river. Lakes such as these are often not very far from an active river, which you can see in the early stages of our map. The lake itself would likely have many aquatic plants such as water lettuce, water lillies, and a few others. In between the bodies of water would be woodland, dominated primarily by angiosperms, though things such as bald cypress might thrive in areas where the water level rises frequently due to their ability to survive fluctuating water levels. One thing that we know for sure is that there were horsetails around the lake, as there have been recovered, intact fossils of these found in the deposit.
Based on several factors, it appears that the lake would have been quite murky/muddy, which is not represented in this screenshot, but that is being taken into account. You can see the murkier water in the below screenshot of a floodplain area surrounding a river system. Such environments were common in Hell Creek - many sites were deposited when a river flooded a large area, burying anything living [or dead] within a certain area (these types of deposits are known as Crevasse Splays). Note that we do not have all of the angiosperm vegetation models ready yet, so the plant distributions and densities that you see here are not indicative of what they will be in the final product.
Well, I hope this has given you a bit of a better idea of what Hell Creek was like! I am looking forward to going out to Montana and getting a better idea of what things are like in the field!
Acknowledgements:
Lofgren, D.F. 1997. "Hell Creek Formation". In: Currie, P.J.; Padian, K., editors. 1997. The Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 302-303.
Breithaupt, B.H. 1997. "Lance Formation". In: In: Currie, P.J.; Padian, K., editors. 1997. The Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 394-395.
Eberth, D.A. (1997). "Edmonton Group". In: Currie, P.J.; Padian, K., editors. 1997. The Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 199-204.
