Age (geology)

A geologic age is a subdivision of geologic time that divides an epoch into smaller parts. A succession of rock strata laid down in a single age on the geologic timescale is a stage.

Units in geochronology and stratigraphy[1]
Segments of rock (strata) in chronostratigraphy Time spans in geochronology Notes to
geochronological units
Eonothem Eon 4 total, half a billion years or more
Erathem Era 10 defined, several hundred million years
System Period 22 defined, tens to ~one hundred million years
Series Epoch 34 defined, tens of millions of years
Stage Age 99 defined, millions of years
Chronozone Chron subdivision of an age, not used by the ICS timescale

See also

References

  1. ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.
2019 in paleontology

Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2019.

Boring Billion

The Boring Billion is a term coined by palaeontologist Martin Brasier to refer to the approximately one billion-year period between 1.8 and 0.8 Ga in Earth's history, during the Proterozoic Eon, that is characterized by environmental, evolutionary, and lithospheric stability. The exact timing and duration of the Boring Billion is not agreed upon by scientists, with estimates for the beginning and end of the Boring Billion ranging between 1.8 and 2.4 Ga for initiation and between 0.5 and 0.8 Ga for termination. This period has also been termed the "Barren Billion", "Dullest Time on Earth" and "Earth’s Middle Ages". However, despite the "boring" label, when plate tectonics, environmental conditions, and the evolution of eukaryotic life are considered, much was happening during this period (see below).

In the time leading up to the Boring Billion, Earth experienced multiple widespread glaciations, the origin of prokaryotic life, the introduction of oxygen into the atmosphere with the evolution of cyanobacteria, addition of UV-blocking ozone to the atmosphere, and the oxidizing of iron in the oceans. After the Boring Billion, the atmosphere again underwent rapid changes as atmospheric oxygen rose to approximately modern levels, most modern major animal phyla evolved during the Cambrian explosion, and large animals appeared in the oceans.By contrast, the period of the Boring Billion was characterized by climatic stability, low levels of atmospheric oxygen, a relative lack of biological events, and the absence of extreme changes in the atmospheric and oceanic composition. Stability during the Boring Billion may be attributed to existence of a relatively stable supercontinent that was initiated by 1.7 Ga and persisted until its breakup around 0.75 Ga.During the Boring Billion, green and purple photosynthetic bacteria appear to have thrived in an anoxic and sulfidic ocean. This ocean was much less productive than modern oceans, releasing sulfurous gasses including toxic hydrogen sulfide, and was very limited in nutrients (especially Mo, Fe, N, and P). As the Boring Billion progressed, eukaryotic life evolved from an Archean ancestor within this ocean. By the end of the Boring Billion, the first life had appeared on land.. It was ended by a period of intense cold, of uncertain origin, which resulted in glaciation over much or even all of the Earth (the so-called Snowball Earth).

Carnian

The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic series (or earliest age of the Late Triassic epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by the Norian. Its boundaries are not characterized by major extinctions or biotic turnovers, but a climatic event (known as the Carnian Pluvial Event) occurred during the Carnian and seems to be associated with important extinctions or biotic radiations.

Chaicayán Group

Chaicayán Group is a group of poorly defined sedimentary rock strata found in Taitao Peninsula in the west coast of Patagonia. The commones rock types are siltstone and sandstone. Conglomerate occur but is less common.Study of fossils and uranium–lead dating of detrital zircons indicate a Miocene age, at least for the upper sequences. The Chaicayán Group deposited likely as a result of a marine transgression that drowned much of Patagonia and Central Chile in the Late Oligocene and Miocene.The group is intruded by porphyritic stocks and sills of Pliocene age.

Embryo fossil

Fossil embryos are the preserved remains of unhatched or unborn organisms. Many fossils of the 580 -million-year-old Doushantuo formation have been interpreted as embryos; embryos are also common throughout the Cambrian fossil record.

Geochronometry

Geochronometry is a branch of stratigraphy aimed at the quantitative measurement of geologic time. It is considered a branch of geochronology.

Geology of the Republic of the Congo

The geology of the Republic of the Congo, also known as Congo-Brazzaville, to differentiate from the Democratic Republic of the Congo, formerly Zaire, includes extensive igneous and metamorphic basement rock, some up to two billion years old and sedimentary rocks formed within the past 250 million years. Much of the country's geology is hidden by sediments formed in the past 2.5 million years of the Quaternary.

Glikson crater

Glikson crater is an impact structure (or astrobleme), the eroded remnant of a former impact crater, situated in the Little Sandy Desert of central Western Australia. A possible impact structure was first reported in 1997, and named after Australian geologist A. Y. Glikson, attention to the site being drawn by the presence of a prominent 14 km diameter ring-shaped aeromagnetic anomaly. The area within the ring contains sparse outcrop of uplifted and deformed Neoproterozoic sandstone, but is largely covered by sand dunes. The recent discovery of shatter cones and microscopic shock effects is reliable evidence for an impact origin. Deformation of the sandstone consistent with an impact origin extends out to a diameter of 19 km, which is the best estimate for the original diameter of the original crater. The ring-shaped aeromagnetic anomaly was probably caused by disruption of a horizontal layer of magnetic igneous rock, known as a sill, by the impact event. Nearby outcrops of dolerite have been dated at 508 ± 5 Ma (Middle

Cambrian), and if this is the same rock causing the aeromagnetic anomaly, then the impact must be younger, probably of Paleozoic age.

Hawaii (island)

Hawaiʻi ( (listen) hə-WY-ee; Hawaiian pronunciation: [həˈvɐjʔi]) is the largest island located in the U.S. state of Hawaii. It is the largest and the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of 4,028 square miles (10,430 km2), it has 63% of the Hawaiian archipelago's combined landmass, and is the largest island in the United States. However, it has only 13% of Hawaiʻi's people. The island of Hawaiʻi is the third largest island in Polynesia, behind the two main islands of New Zealand.The island is often referred to as the Island of Hawaiʻi, the Big Island, or Hawaiʻi Island to distinguish it from the state. Administratively, the whole island encompasses Hawaiʻi County.

As of the 2010 Census the population was 185,079. The county seat and largest city is Hilo. There are no incorporated cities in Hawaiʻi County (see List of counties in Hawaii).

Laguna Brava Formation

Laguna Brava Formation (Spanish: Formación Laguna Brava), formerly referred to as Santo Domingo Formation, is a Late Eocene (Tinguirirican in the SALMA classification) sedimentary formation located in the Argentine Northwest. The formation contains beds with fossil bird tracks described as Gruipeda dominguensis.It was formerly thought that the formation was of Triassic age.

Stratigraphy of New Zealand

This is a list of the units into which the rock succession of New Zealand is formally divided. As new geological relationships have been discovered new names have been proposed and others are made obsolete. Not all these changes have been universally adopted. This table is based on the 2014 New Zealand Stratigraphic Lexicon (Litho2014). However, obsolete names that are still in use and names postdating the lexicon are included if it aids in understanding.Names for particular rock units have two parts, a proper name which is almost always a geographic location where the rock is found and a hierarchical rank (e.g. Waitematā Group). This ranking system starts with individual 'beds' of rock which can be grouped into 'members', members are grouped into 'formations', formations into 'subgroups' then 'groups'. In New Zealand, groups are further combined into 'supergroups' or for basement rocks into terranes. Not all of these hierarchical layers are necessarily present within a particular rock succession. Many New Zealand rocks can also have names based on their major rock types, such as the Wooded Peak Limestone or the Hawks Crag Breccia.

Volcanology of New Zealand

Volcanology of New Zealand is the scientific study of volcanoes and volcanic phenomena in New Zealand. Volcanism has been responsible for many of the country's geographical features, especially in the North Island and the country's outlying islands.

While the land's volcanic history dates back to before the Zealandia microcontinent rifted away from Gondwana 60–130 million years ago, activity continues today with minor eruptions occurring every few years. This recent activity is primarily due to the country's position on the boundary between the Indo-Australian and Pacific Plates, a part of the Pacific Ring of Fire, and particularly the subduction of the Pacific Plate under the Indo-Australian Plate.

New Zealand's rocks record examples of almost every kind of volcanism observed on Earth, including some of the world's largest eruptions in geologically recent times.

None of the South Island's volcanoes are active.

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