![<span class="mw-page-title-main">John Day Formation</span>](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Blue_basin_lower_trail.jpg/320px-Blue_basin_lower_trail.jpg)
The John Day Formation is a series of rock strata exposed in the Picture Gorge district of the John Day River basin and elsewhere in north-central Oregon in the United States. The Picture Gorge exposure lies east of the Blue Mountain uplift, which cuts southwest–northeast through the Horse Heaven mining district northeast of Madras. Aside from the Picture Gorge district, which defines the type, the formation is visible on the surface in two other areas: another exposure is in the Warm Springs district west of the uplift, between it and the Cascade Range, and the third is along the south side of the Ochoco Mountains. All three exposures, consisting mainly of tuffaceous sediments and pyroclastic rock rich in silica, lie unconformably between the older rocks of the Clarno Formation below and Columbia River basalts above.
![<i>Protohippus</i> Extinct genus of mammals](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Protohippus_simus.jpg/320px-Protohippus_simus.jpg)
Protohippus is an extinct three-toed genus of horse. It was roughly the size of a modern donkey. Fossil evidence suggests that it lived during the Late Miocene, from about 13.6 Ma to 5.3 Ma.
![<i>Pseudhipparion</i> Extinct genus of mammals](https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Pseudohipparion_retrusus.JPG/320px-Pseudohipparion_retrusus.JPG)
Pseudhipparion is an extinct genus of three-toed horse endemic to North America during the Miocene. They were herding animals whose diet consisted of C3 plants. Fossils found in Georgia and Florida indicate that it was a lightweight horse, weighing up to 90 pounds. In 2005, fossils were unearthed in Oklahoma. Seven species of Pseudhipparion are known from the fossil record which were very small, following the trend of Bergmann's rule.
![<i>Nannippus</i> Extinct genus of mammals](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Nannippus_jaw.JPG/320px-Nannippus_jaw.JPG)
Nannippus is an extinct genus of three-toed horse endemic to North America during the Miocene through Pleistocene, about 13.3—1.8 million years ago (Mya), living around 11.5 million years. This ancient species of three-toed horse grew up to 3.5 feet and weighed between 165 pounds to 199 pounds, which was around the same size as a domestic sheep.
![<i>Cormohipparion</i> Extinct genus of horse](https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Ashfall_Fossil_Beds_-_Teleoceras_and_Cormohipparion.jpg/320px-Ashfall_Fossil_Beds_-_Teleoceras_and_Cormohipparion.jpg)
Cormohipparion is an extinct genus of horse belonging to the tribe Hipparionini that lived in North America during the late Miocene to Pliocene. They grew up to 3 feet long.
The Irdin Manha Formation is a geological formation from the Eocene located in Inner Mongolia, China, a few kilometres south of the Mongolian border.
Phlaocyon annectens is an extinct species of the genus Phlaocyon, belonging to the subfamily Borophaginae and tribe Phlaocyonini, a canid endemic to central and western North America from the Late Oligocene to Early Miocene living 24.6—20.8 mya and existed for approximately 4.2 million years.
![<span class="mw-page-title-main">Carlile Shale</span> Geologic formation in the western US](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Fairport_Chalk_Member_of_the_Carlile_Formation_in_Ellis_County%2C_Kansas_01.png/320px-Fairport_Chalk_Member_of_the_Carlile_Formation_in_Ellis_County%2C_Kansas_01.png)
The Carlile Shale is a Turonian age Upper/Late Cretaceous series shale geologic formation in the central-western United States, including in the Great Plains region of Colorado, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming.
![<span class="mw-page-title-main">Ogallala Formation</span> Geologic formation in the western United States](https://upload.wikimedia.org/wikipedia/commons/thumb/8/86/Ash_Hollow_Nebraska.JPG/320px-Ash_Hollow_Nebraska.JPG)
The Ogallala Formation is a Miocene to early Pliocene geologic formation in the central High Plains of the western United States and the location of the Ogallala Aquifer. In Nebraska and South Dakota it is also classified as the Ogallala Group. Notably, it records the North American Land Mammal Ages (NALMAs) Hemphillian, Clarendonian, and Barstovian. It also includes an excellent record of grass seeds and other plant seeds, which can be used for biostratigraphic dating within the formation. The Ogallala Formation outcrops of Lake Meredith National Recreation Area preserve fish fossils. Similar specimens from the same unit are found at Alibates Flint Quarries National Monument in Texas.
![<span class="mw-page-title-main">Ash Hollow Formation</span> Geologic formation in Nebraska](https://upload.wikimedia.org/wikipedia/commons/thumb/8/86/Ash_Hollow_Nebraska.JPG/320px-Ash_Hollow_Nebraska.JPG)
The Ash Hollow Formation of the Ogallala Group is a geological formation found in Nebraska and South Dakota. It preserves fossils dating back to the Neogene period. It was named after Ash Hollow, Nebraska and can be seen in Ash Hollow State Historical Park. Ashfall Fossil Beds State Historical Park is within this formation.
![<span class="mw-page-title-main">Rosebud Formation</span> Geological formation in midwestern US](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Natural_seeps_PA120590.jpg/320px-Natural_seeps_PA120590.jpg)
The Rosebud Formation is a geologic formation of cemented pink silt in Nebraska and South Dakota, dating to the early middle Miocene epoch of the Neogene period. Possibly named for its color, no type location has been set for this unit, but it is associated with the Valentine Formation along the Niobrara River. The fine silt of the formation forms an aquitard beneath the Ogallala Aquifer carried by the Valentine Formation. Many springs from the Valentine sands flow down the Rosebud outcrop into the Niobrara River.
The Sharps Formation is a geologic formation in South Dakota. It preserves fossils dating back to the Paleogene.
![<span class="mw-page-title-main">Marsland Formation</span>](https://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Syndyoceras_cooki_%28fossil_mammal%29_%28Marsland_Formation%2C_Middle_Miocene%3B_near_Agate%2C_Nebraska%2C_USA%29_2_%2832708793602%29.jpg/320px-Syndyoceras_cooki_%28fossil_mammal%29_%28Marsland_Formation%2C_Middle_Miocene%3B_near_Agate%2C_Nebraska%2C_USA%29_2_%2832708793602%29.jpg)
The Marsland Formation is a geologic formation in Nebraska. It preserves fossils dating back to the Neogene period.
The Astoria Formation is a geologic formation in Washington state & Oregon. It preserves fossils dating back to the early to middle Miocene.
The Dove Spring Formation is a geologic formation in the western Mojave Desert of California. It preserves fossils dating back to the Miocene epoch of the Neogene period.
Hyperailurictis is an extinct genus of felid from Miocene North America. The Hyperailurictis species are Pseudaelurus-grade felids and thought to be the first felids in the Americas.
![<span class="mw-page-title-main">Sarmiento Formation</span> Geologic formation in Chubut Province, Argentina](https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Geographic_location_of_Cabeza_Blanca_locality.png/320px-Geographic_location_of_Cabeza_Blanca_locality.png)
The Sarmiento Formation, in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million years from the mid-Eocene to the early Miocene. It predominantly consists of pyroclastic deposits, which were deposited in a semi-arid environment. It is divided up into a number of members. The diverse fauna of the Sarmiento Formation, including a variety of birds, crocodilians, turtles and snakes, also includes many mammals such as South American native ungulates as well as armadillos, and caviomorph rodents. Piram Conglomerate Formation
![<i>Andrias matthewi</i> Extinct species of amphibian](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Andrias_matthewi_size_comparison.jpg/320px-Andrias_matthewi_size_comparison.jpg)
Andrias matthewi, or Matthew's giant salamander, is an extinct species of giant salamander from the Miocene of North America. It belongs to the genus Andrias, which contains the living Asian giant salamanders. It is the largest salamander to have ever existed, with a maximum estimated length of 2.3 m. Its fossils have been found in Nebraska, Colorado, and Saskatchewan.
![<span class="mw-page-title-main">Santa Cruz Formation</span> Geological formation in Patagonia](https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Santa_Cruz_Formation_strata.jpg/320px-Santa_Cruz_Formation_strata.jpg)
The Santa Cruz Formation is a geological formation in the Magallanes/Austral Basin in southern Patagonia in Argentina and in adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with eponymous Santacrucian SALMA. The formation extends from the Andes to the Atlantic coast. In its coastal section it is divided into two members, the lower, fossil rich Estancia La Costa Member, which has a lithology predominantly consisting of tuffaceous deposits and fine grained sedimentary claystone and mudstone, and the upper fossil-poor Estancia La Angelina Member, which consists of sedimentary rock, primarily claystone, mudstone, and sandstone. The environment of deposition is interpreted to have been mostly fluvial, with the lowermost part of the Estancia La Costa Member being transitional between fluvial and marine conditions. The environment of the Estancia La Costa Member is thought to have been relatively warm and humid, but likely became somewhat cooler and drier towards the end of the sequence. The Santa Cruz Formation is known for its abundance of South American native ungulates, as well as an abundance of rodents, xenarthrans, and metatherians.