If we exclude Quaternary alluvium and cover, there are only a handful of National Park Service units with significant Cenozoic nonmarine sedimentary rocks. They are all in the western half of the contiguous US or Alaska, which is not hugely surprising (the eastern half has generally not been much on sedimentary basins since the rifting at the end of the Triassic, and the great majority of NPS units are relatively small and devoted to cultural and/or historic features). Twenty or so parks have notable sedimentary rocks and deposits, including all of the parks with the word "fossil" in their name. (Forgive all of my qualifying; I use "nonmarine" because "terrestrial" just doesn't do when several of these were deposited in lakes, and it's kind of awkward to use "rocks" all the time when many of the formations in question are not actually lithified all that well, especially as you get closer in time to the present.)
First, a few that have more than a couple of sedimentary units of note:
Big Bend National Park: When considered geologically, Big Bend is often thought of in terms of Late Cretaceous fossils, but it has darn near the entire Cenozoic covered, with the Black Peaks Formation (Late Cretaceous–Paleocene), Hannold Hill Formation (Early Eocene), Canoe Formation (Middle Eocene), Chisos Formation (Middle Eocene–Early Oligocene), South Rim Formation (Early Oligocene), Delaho Formation (latest Oligocene–Early or Middle Miocene), Banta Shut-In Formation (Late Miocene), and various alluvial deposits (Pliocene to present), as well as igneous rocks. It's one of the few parks that has the early Paleocene. As the spreadsheet graphic shows, the NPS record is kind of thin in the early and middle Paleocene.
Death Valley National Park: This park has one of the most comprehensive geologic records of the NPS (although it gives the Mesozoic a pass in terms of sedimentary rocks). Notable named Cenozoic units include the Titus Canyon Formation (Late Eocene–Late Oligocene) and Copper Canyon Formation (Pliocene).
Grand Teton National Park: Grand Teton National Park is another park with a lot of coverage, including the Pinyon Conglomerate (Late Cretaceous–Paleocene), the volcanically sourced Hominy Peak Formation (Early–Middle Eocene) and Colter Formation (Early–Middle Miocene), and lacustrine Teewinot Formation (Middle–?Late Miocene), plus surplus volcanics from the Yellowstone Caldera, and about the youngest mountains you can find. Oddly, there are also a number of isolated outliers of other Cenozoic formations within a few miles of the park.
Katmai National Park and Preserve and Lake Clark National Park and Preserve: These two parks in southwestern Alaska are better known for their volcanoes, and their Mesozoic sedimentary rocks would probably be the next thing in the list of geologic highlights, but both also have Cenozoic sedimentary rocks. Katmai includes the Ketavik Formation (Paleocene and/or Eocene), Copper Lake Formation (Paleocene? and Early Eocene), and Hemlock Conglomerate (Late Oligocene?). Lake Clark has the West Foreland Formation (Late Paleocene–Early Eocene) and Tyonek Formation (Oligocene–Middle Miocene). These formations are noted for plant fossils.
Lake Mead National Recreation Area: The Horse Spring Formation (Late Oligocene–Middle Miocene) and Muddy Creek Formation (Late Miocene–Pliocene) are among the Cenozoic rocks and deposits here.
The second group of parks generally feature just one or two formations of note, but that's very much downplaying things. These formations are usually the reason that the parks exist, either due to the scenic value or their paleontology (again, those that include "fossil" in their titles). In roughly chronological order:
Theodore Roosevelt National Park: This park is mostly over Late Paleocene-age formations (Tongue River and Sentinel Butte of the Fort Union Group), which provide the scenic setting, and are also fossiliferous, providing a look at a unique time in history when North Dakota was absolutely swarming with crocodilians. There were other things as well, of course, but it's hard to overlook the crocs. If you've visited the Science Museum of Minnesota, these rocks are the same as those that provided the Wannagan Creek fauna.
Bryce Canyon National Park and Cedar Breaks National Monument: These two parks feature colorful and heavily-eroded exposures of the Claron Formation, deposited from the Paleocene to the Middle Eocene in a variety of settings. Traditionally, the Claron Formation is thought to represent a large lake, but more recent interpretations favor more diverse settings.
Fossil Butte National Monument: This monument was established for the heavily fossiliferous Green River Formation, deposited during the Early Eocene in a lake. The Green River Formation encompasses multiple lake basins; Fossil Butte is in the small, skinny Fossil Lake basin of western Wyoming. It is best known for its fish fossils, which have been excavated since the second half of the 19th century.
John Day Fossil Beds National Monument: John Day Fossil Beds National Monument is cheating a bit to be in this category, because its stratigraphic record incorporates several formations that cover quite a bit of the Cenozoic. These include the Clarno Formation (Early–Middle Eocene), John Day Formation (Middle Eocene–Early Miocene), Mascall Formation (Early–Middle Miocene), and Rattlesnake Formation (Late Miocene). Although the John Day Fossil Beds are justly famous for their mammal fossils, they are also known for their plant fossils, particularly the Clarno Nut Beds.
Florissant Fossil Beds National Monument: The wildly diverse plants and invertebrates of Florissant Fossil Beds National Monument come from the Late Eocene-age Florissant Formation. Like the Green River Formation, the Florissant Formation was deposited in a lake (although decidedly closer to a volcano), and like Fossil Butte, Florissant's fossils have long been excavated and distributed around the world.
Agate Fossil Beds National Monument: The namesake fossil beds are in the Early Miocene-age Harrison Formation and overlying Anderson Ranch Formation. You may have seen blocks of countless jumbled bones in museums, from "Agate, Nebraska" or something similar; these blocks came from here. Historically, Agate is best known for rhinos (Menoceras and Diceratherium), chalicotheres (Moropus), and giant pig-like entelodonts (Daeodon), which are particularly common in the lower Anderson Ranch Formation. If you know anything about taxonomic practices of the early 20th century, it will not surprise you to find out that at one point seven species of rhino were postulated from a single site. Agate is also known for corkscrew burrows dug by early beavers (Daemonelix burrows, dug by Palaeocastor), amphicyonid (bear-dog) burrows and dens, and a bonebed of the small early camel Stenomylus in the Harrison Formation.
Scotts Bluff National Monument: Geologically speaking, Scotts Bluff National Monument slots in rather nicely between Agate Fossil Beds National Monument and Badlands National Park, with the Early Oligocene-age Brule Formation, the Late Oligocene Gering Formation, and the Late Oligocene–Early Miocene Monroe Creek and Harrison formations. Scotts Bluff was a landmark on several of the emigrant trails, and travelers sometimes made note of the local fossils (turtles and what we'd now call oreodonts) in their journals.
Badlands National Park: The Late Eocene-age Chadron Formation and the Early Oligocene-age Brule Formation are the best-known contributors to the famous eroded landscape and fossils of the White River Badlands. The most famous fossils are probably saber-toothed nimravids, entelodonts, sheep-ish oreodonts, rhinos, and turtles.
Niobrara National Scenic River: This scenic river cuts through a landscape dominated by the Ogallala Group, particularly the Valentine and Ash Hollow formations. Its Cenozoic rocks and deposits date from the Middle Miocene to the present. The Niobrara River valley has long been a source of mammal fossils (Joseph Leidy described a number of fossils before the Civil War; the only provenance information he could supply was "the Niobrara Valley", which narrows things down to much of northern Nebraska. This is better than "White River Badlands" for provenance, but not by a whole lot). Horses and rhinos are probably the most familiar fossils from these rocks, but several sites in the vicinity of the river have yielded rich microfossil assemblages of amphibians, reptiles, and small mammals.
Montezuma Castle National Monument and Tuzigoot National Monument: These two monuments feature the Verde Formation, of the Middle Miocene–Pliocene. The Verde Formation is associated with the Verde River, which during those times was periodically dammed by lava flows and formed a lake. It has a variety of miniscule aquatic fossils, like diatoms and ostracodes, as well as plant and mammal fossils, and mammal tracks.
Hagerman Fossil Beds National Monument: The namesake fossil beds are part of the Glenns Ferry Formation, deposited near the Early–Late Pliocene boundary. Hagerman is best known for the Hagerman Horse, Equus simplicidens, one of the oldest species in the modern horse genus Equus. It may have been a zebra-like horse.
Tule Springs Fossil Beds National Monument: One of the newest National Park Service units, Tule Springs Fossil Beds National Monument includes sediments and fossils from the Middle Pleistocene to the present. The original impetus for study was to see if ancient humans were coexisting with and hunting Pleistocene megafauna (sloths, mammoths, mastodons, horses, extinct bison, etc.) here. Although this didn't so much turn out, researchers did find abundant Pleistocene mammals, with mammoths being the stars.
Finally, two parks are associated with historic paleontological work in Cenozoic rocks, although they have only limited fossil resources: Fort Laramie National Historic Site preserves the site of Fort Laramie, which among other things was used as a base of operations by O. C. Marsh for the nearby Arikaree Formation of the Late Oligocene–Early Miocene; and Fort Union Trading Post National Historic Site features Fort Union, which Ferdinand Vandeveer Hayden and Fielding Bradford Meek used as a base of collecting operations, and which gave its name to the Fort Union Formation/Group.
|Here we have the parks with their geologic times in approximate chronological order. I've omitted bog-standard Pleistocene–Holocene alluvium and cover. Click to embiggen.|