Rattlesnake Formation | |
---|---|
Stratigraphic range: Miocene-Late Pliocene | |
Type | Sedimentary and igneous |
Overlies | Mascall Formation, Columbia River Basalt Group |
Area | John Day Valley |
Thickness | 700 feet (210 m) |
Lithology | |
Primary | Fanglomerate, siltstone |
Other | Tuff (ignimbrite) |
Location | |
Coordinates | 44°30′N119°36′W / 44.5°N 119.6°W |
Approximate paleocoordinates | 44°30′N116°54′W / 44.5°N 116.9°W |
Region | Oregon |
Country | United States |
Extent | eastern Oregon |
Type section | |
Named for | Rattlesnake Creek |
Named by | J. C. Merriam |
Year defined | 1901 [1] |
The Rattlesnake Formation is a Miocene to late Pliocene geologic formation found along the John Day River Valley of Oregon, in the Western United States.
The formation is described in Geologic Formations of Eastern Oregon (1972) as follows:
The unit is composed of up to 700 feet of fanglomerate and finer terrestrial sediments and a 40-foot thick ignimbrite unit which crops out in the middle of the section. The gravel is well rounded and consists of pebbles of basalt, chert, siltstone, diorite, rhyolite, and chert set in a medium-grained matrix of poorly indurated volcanic sandstone. The ignimbrite displays zonation typical of welded ashflow tuffs and is a prominent ridge former. [2]
The ignimbrite was radiometrically dated by the Potassium–argon method at 6.4 million years by Evernden and James (1964). [3]
Middle and late Pliocene mammals have been recovered from beneath the ignimbrite. Fossils found here include Amebelodon sp. , the extinct peccary Mylohyus longirostris , the extinct North American rhino Teleoceras fossiger , Indarctos oregonensis , Pliohippus spectans , Machairodus sp. , Hemiauchenia vera , an extinct species of fox known as Vulpes stenognathus and the earliest record of modern-day beavers. [4] [5] [6]
In the lower fanglomerate member of the Rattlesnake Formation, remains of Pekania occulta were found. [7] [8]
The Pliocene is the epoch in the geologic time scale that extends from 5.333 million to 2.58 million years ago. It is the second and most recent epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian Stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.
John Day Fossil Beds National Monument is a U.S. national monument in Wheeler and Grant counties in east-central Oregon. Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved layers of fossil plants and mammals that lived in the region between the late Eocene, about 45 million years ago, and the late Miocene, about 5 million years ago. The monument consists of three geographically separate units: Sheep Rock, Painted Hills, and Clarno.
The Nevadan orogeny occurred along the western margin of North America during the Middle Jurassic to Early Cretaceous time which is approximately from 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kinds of orogenic processes occurring. During the early stages of orogenesis an "Andean type" continental magmatic arc developed due to subduction of the Farallon oceanic plate beneath the North American Plate. The latter stages of orogenesis, in contrast, saw multiple oceanic arc terranes accreted onto the western margin of North America in a "Cordilleran type" accretionary orogen. Deformation related to the accretion of these volcanic arc terranes is mostly limited to the western regions of the resulting mountain ranges and is absent from the eastern regions. In addition, the deformation experienced in these mountain ranges is mostly due to the Nevadan orogeny and not other external events such as the more recent Sevier and Laramide Orogenies. It is noted that the Klamath Mountains and the Sierra Nevada share similar stratigraphy indicating that they were both formed by the Nevadan orogeny. In comparison with other orogenic events, it appears that the Nevadan Orogeny occurred rather quickly taking only about 10 million years as compared to hundreds of millions of years for other orogenies around the world.
The Boring Lava Field is a Plio-Pleistocene volcanic field with cinder cones, small shield volcanoes, and lava flows in the northern Willamette Valley of the U.S. state of Oregon and adjacent southwest Washington. The field got its name from the town of Boring, Oregon, located 12 miles (20 km) southeast of downtown Portland. Boring lies southeast of the densest cluster of lava vents. The zone became volcanically active about 2.7 million years ago, with long periods of eruptive activity interspersed with quiescence. Its last eruptions took place about 57,000 years ago at the Beacon Rock cinder cone volcano; the individual volcanic vents of the field are considered extinct, but the field itself is not.
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.
The Mascall Formation is a Miocene geologic formation found along the John Day River Valley of Oregon, in the Western United States.
Halmahera Arc is the volcanic arc of the Halmahera region of eastern Indonesia. It is considered to belong to the Halmahera Plate within the Molucca Sea Collision Zone.
Indarctos is an extinct genus of bear, endemic to North America, Europe and Asia during the Miocene. It was present from ~11.1 to 5.3 Ma, existing for approximately 6.2 million years.
The San Juan volcanic field is part of the San Juan Mountains in southwestern Colorado. It consists mainly of volcanic rocks that form the largest remnant of a major composite volcanic field that covered most of the southern Rocky Mountains in the Middle Tertiary geologic time. There are approximately fifteen calderas known in the San Juan Volcanic Fields; however, it is possible that there are two or even three more in the region.
The Bluff Downs fossil site is a paleontological site of Pliocene age in northern Queensland, Australia. It is one of the most significant fossil sites of Pliocene age in Australia due to its unique fauna and specific dating. The fossil site lies on the banks of the Allingham Creek on the pastoral property of Bluff Downs Station, northwest of Charters Towers on the Cape York Peninsula
Acer clarnoense is an extinct maple species in the family Sapindaceae described from a series of isolated fossil leaves and samaras. The species is known from the late Eocene sediments exposed in the state of Oregon in the US. It is one of several extinct species placed in the living section Macrantha.
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The Ringold Formation is a geologic formation in Eastern Washington, United States. The formation consists of sediment laid down by the Columbia River following the flood basalt eruptions of the Columbia River Basalt Group, and reaches up to 1,000 feet (300 m) thick in places. It preserves fossils dating back to the Neogene period.
The Coyote Butte Limestone (OR085) is a geologic formation in Oregon. It preserves fossils dating back to the Sakmarian to Kungurian stages of the Permian period, spanning an estimated 23 million years. The formation occurs in isolated buttes to the north; Triangulation Hill, and south; type locality and name giver Coyote Butte and Tuckers Butte, on either side of the Grindstone and Twelvemile Creeks in Crook County, Oregon.
Cerro Guacha is a Miocene caldera in southwestern Bolivia's Sur Lípez Province. Part of the volcanic system of the Andes, it is considered to be part of the Central Volcanic Zone (CVZ), one of the three volcanic arcs of the Andes, and its associated Altiplano-Puna volcanic complex (APVC). A number of volcanic calderas occur within the latter.
Jotabeche is a Miocene-Pliocene caldera in the Atacama Region of Chile. It is part of the volcanic Andes, more specifically of the extreme southern end of the Central Volcanic Zone (CVZ). This sector of the Andean Volcanic Belt contains about 44 volcanic centres and numerous more minor volcanic systems, as well as some caldera and ignimbrite systems. Jotabeche is located in a now inactive segment of the CVZ, the Maricunga Belt.
Pekania is a genus of mustelid that contains a single living species, the fisher (Pekania pennanti). Formerly placed in the genus Martes, it was determined to be distinct enough to be placed within its own genus. A 2013 study also identified several fossil species formerly in Martes that are more closely related – and probably ancestral – to the fisher, moving them into Pekania as well.
Cooks Creek is a tributary of the Delaware River in Bucks County, Pennsylvania, in the United States, rising in Springfield Township and passing through Durham Township before emptying into the Pennsylvania Canal and the Delaware.
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