The Pennsylvanian (also known as Upper Carboniferous or Late Carboniferous) is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly to Ma (million years ago). As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few hundred thousand years. The Pennsylvanian is named after the U.S. state of Pennsylvania, where the coal-productive beds of this age are widespread.
The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America, where the early Carboniferous beds are primarily marine limestones, the Pennsylvanian was in the past treated as a full-fledged geologic period between the Mississippian and the Permian. In Europe, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period.
Amphibians were diverse and common; some were several meters long as adults. The collapse of the rainforest ecology in the mid-Pennsylvanian (between the Moscovian and the Kasimovian) removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however, prospered due to specific key adaptations. One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. These included the earliest sauropsid reptiles (Hylonomus), and the earliest known synapsid (Archaeothyris). Small lizard-like animals quickly gave rise to many descendants. Reptiles underwent a major evolutionary radiation, in response to the drier climate that followed the rainforest collapse.
The major forms of life at this time were the arthropods. Due to the high levels of oxygen, arthropods were far larger than modern ones. Arthropleura, a giant millipede relative, was a common sight and the giant dragonfly Meganeura "flew the skies".
North American subdivision is into five stages, but not precisely the same, with additional (older) Appalachian series names following:
The Virgilian or Conemaugh corresponds to the Gzhelian plus the uppermost Kasimovian. The Missourian or Monongahela corresponds to the rest of the Kasimovian. The Desmoinesian or Allegheny corresponds to the upper half of the Moscovian. The Atokan or upper Pottsville corresponds to the lower half of the Moscovian. The Morrowan corresponds to the Bashkirian.
Anna Jonas Stose (August 17, 1881 – October 27, 1974) was a major geological pioneer, who worked for the American Museum of Natural History, Maryland Geological Survey, Pennsylvania Geological Survey, Virginia Geological Survey, and the United States Geological Survey. She is best known for her work mapping the Appalachian Mountain Range, documenting the structure of and exposure to the rock formations, and tracing crystalline rocks. Stose was among the first to implement petrographic and structural techniques to the Appalachian Mountains, which were still in development at the time. This was rare because women at this time didn’t do physical work in the fields, and her hard efforts are now noted and appreciated. She contributed largely to the Geologic Map of Virginia and the Geologic Map of the United States.Antler orogeny
The Antler orogeny was a tectonic event that began in the early Late Devonian with widespread effects continuing into the Mississippian and early Pennsylvanian. Most of the evidence for this event is in Nevada but the limits of its reach are unknown. A great volume of conglomeratic deposits of mainly Mississippian age in Nevada and adjacent areas testifies to the existence of an important tectonic event, and implies nearby areas of uplift and erosion, but the nature and cause of that event are uncertain and in dispute. Although it is known as an orogeny (mountain building event), some of the classic features of orogeny as commonly defined such as metamorphism, and granitic intrusives have not been linked to it. In spite of this, the event is universally designated as an orogeny and that practice is continued here. This article outlines what is known and unknown about the Antler orogeny and describes three current theories regarding its nature and origin.Appalachian Plateau
The Appalachian Plateau is a series of rugged dissected plateaus located on the western side of the Appalachian Mountains. The Appalachian Mountains are a mountain range that run down the entire East Coast of the United States.
The Appalachian Plateau is the northwestern part of the Appalachian Mountains, stretching from New York to Alabama. The plateau is a second level United States physiographic region, covering parts of the states of New York, Pennsylvania, Ohio, Maryland, West Virginia, Virginia, Kentucky, Tennessee, Alabama, and Georgia.Jill Witmer
Jill Witmer (born October 1, 1991) is an American field hockey player. Witmer was named to the U.S. National Team in 2013 and was named to the U.S. Olympic Team in 2016.Pennsylvanian
Pennsylvanian may refer to:
A person or thing from Pennsylvania
Pennsylvanian (geology), a geological subperiod of the Carboniferous Period
Pennsylvanian (train), an Amtrak trainSpearfish Formation
The Spearfish Formation is a geologic formation, originally described from the Black Hills region of South Dakota, United States, but also recognised in North Dakota, Wyoming, Montana and Nebraska. It is a heterogeneous red bed formation, commonly with siltstone and gypsum low in the formation and sandstone and shale higher up. Other rock types include claystone, conglomerate, dolomite, and oil shale. It is typically regarded as Permian–Triassic in age, although its original description included Jurassic rocks.The Spearfish Formation is interpreted as representing shallow marine to coastal terrestrial deposition, like the modern Persian Gulf. Depositional environments may have included restricted marine bodies and ephemeral lakes (gypsum), hypersaline waters (limestone), hypersaline microbial mats (oil shale), and sabkhas (dolomite). The marine waters of the shallow continental sea retreated during the deposition of the formation, reflected in a change from dominantly nearshore marine to coastal terrestrial deposition over time.The Spearfish Formation is sparsely fossiliferous. So far, only stromatolites, casts of bivalves, and trace fossils have been found.
(541.0 Mya–2.5 Gya)
|Archean eon (2.5–4 Gya)|
|Hadean eon (4–4.6 Gya)|