| Hantkenina Temporal range: | |
|---|---|
 | |
| Hantkenina dumblei | |
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Phylum: | Retaria |
| Subphylum: | Foraminifera |
| Class: | Globothalamea |
| Order: | Rotaliida |
| Family: | † Hantkeninidae |
| Genus: | † Hantkenina Cushman, 1924 |
| Species | |
| |
Hantkenina is a genus of planktonic foraminifera that lived from the Middle Eocene up to late Eocene, circa 49 Ma-33.9 Ma. There have been 11 morphospecies described, including one of Cribrohantkenina [1]
Hantkenina is a genus of foraminifera. Hantkeninids are well-known biostratigraphic index fossils. [2] They produce a test ("shell") of calcite (CaCO3). Hantkeninids evolved from Clavigerinella caucasica . [1] Hantkenina is highly distinctive from other planktonic foraminifers as they are characterized by planispiral coiling and their hollow, slender extensions of each chamber known as tubulospines. [2]
The structure of this unique feature vary between individuals, and between species of hantkenina. All hantkeninas species retained tubulospines through their evolution. This indicates that it served a useful purpose for this particular form of foraminifera. The function of the tubulospines are unknown, however, reproduction and feeding purposes have been suggested as possible functions. [3]
The first hantkenids (Hantkenina mexicana) lived in deep planktonic environments with minimum oxygen levels. However, isotopes suggests they migrated to fully oxygenated shallower waters at about 43.8 Ma. [2] During the Eocene the climate went through climate changes. The peak of the Cenozoic warmth occurred during the Early Eocene. Afterwards, global cooling began, persisting to Early Oligocene. [3] The first large ice caps appeared in Antarctica during this time. [4] This climate change also affected deep-water environments.
The cooling process caused gradual changes in the structure of the water column. As the water cooled, the rates of remineralization of organic matter at the near surface water altered. A consequence of this global cooling was that bacterial metabolic rates at the upper water column slowed down and allowed sinking organic matter to descend further to deeper environments in the ocean. This made the oxygen minimum zone, less intense and more spread out. New niches for deep-dwelling zooplankton that were able to tolerate low levels of oxygen opened up. Pearson and Coxall (2013) speculate that the evolution of Clavigerinella and hantkenina was related to this global cooling, [3] as well as pulses of deep-water anoxia [5]
The Cenozoic is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterized by the dominance of insects, mammals, birds and angiosperms. It is the latest of three geological eras of the Phanerozoic Eon, preceded by the Mesozoic and Paleozoic. The Cenozoic started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.
The Eocene is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name Eocene comes from the Ancient Greek Ἠώς and καινός and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.
The Oligocene is a geologic epoch of the Paleogene Period that extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from Ancient Greek ὀλίγος (olígos) 'few' and καινός (kainós) 'new', and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period.
The Paleogene Period is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 Ma to the beginning of the Neogene Period 23.03 Ma. It is the first period of the Cenozoic Era, the tenth period of the Phanerozoic and is divided into the Paleocene, Eocene, and Oligocene epochs. The earlier term Tertiary Period was used to define the time now covered by the Paleogene Period and subsequent Neogene Period; despite no longer being recognized as a formal stratigraphic term, "Tertiary" still sometimes remains in informal use. Paleogene is often abbreviated "Pg", although the United States Geological Survey uses the abbreviation "Pe" for the Paleogene on the Survey's geologic maps.
The Paleocene–Eocene thermal maximum (PETM), alternatively ”Eocene thermal maximum 1 (ETM1)“ and formerly known as the "Initial Eocene" or “Late Paleocene thermal maximum", was a geologically brief time interval characterized by a 5–8 °C global average temperature rise and massive input of carbon into the ocean and atmosphere. The event began, now formally codified, at the precise time boundary between the Paleocene and Eocene geological epochs. The exact age and duration of the PETM remain uncertain, but it occurred around 55.8 million years ago (Ma) and lasted about 200 thousand years (Ka).
Foraminifera are single-celled organisms, members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell of diverse forms and materials. Tests of chitin are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment, while a smaller number float in the water column at various depths, which belong to the suborder Globigerinina. Fewer are known from freshwater or brackish conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit ribosomal DNA.
The Deep Sea Drilling Project (DSDP) was an ocean drilling project operated from 1968 to 1983. The program was a success, as evidenced by the data and publications that have resulted from it. The data are now hosted by Texas A&M University, although the program was coordinated by the Scripps Institution of Oceanography at the University of California, San Diego. DSDP provided crucial data to support the seafloor spreading hypothesis and helped to prove the theory of plate tectonics. DSDP was the first of three international scientific ocean drilling programs that have operated over more than 40 years. It was followed by the Ocean Drilling Program (ODP) in 1985, the Integrated Ocean Drilling Program in 2004 and the present International Ocean Discovery Program in 2013.
An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia."
Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the re-construction of past climate at various intervals. Paleoceanographic research is also intimately tied to paleoclimatology.
The Eocene–Oligocene extinction event, also called the Eocene-Oligocene transition (EOT) or Grande Coupure, is the transition between the end of the Eocene and the beginning of the Oligocene, an extinction event and faunal turnover occurring between 33.9 and 33.4 million years ago. It was marked by large-scale extinction and floral and faunal turnover, although it was relatively minor in comparison to the largest mass extinctions.
The Azolla event is a paleoclimatology scenario hypothesized to have occurred in the middle Eocene epoch, around 49 million years ago, when blooms of the carbon-fixing freshwater fern Azolla are thought to have happened in the Arctic Ocean. As the fern died and sank to the stagnant sea floor, they were incorporated into the sediment over a period of about 800,000 years; the resulting draw-down of carbon dioxide has been speculated to have helped reverse the planet from the "greenhouse Earth" state of the Paleocene-Eocene Thermal Maximum, when the planet was hot enough for turtles and palm trees to prosper at the poles, to the current icehouse Earth known as the Late Cenozoic Ice Age.
The cool tropics paradox is the apparent difference between modeled estimates of tropical temperatures during warm, ice-free periods of the Cretaceous and Eocene, and the colder temperatures which proxies suggested were present. The long-standing paradox was resolved when novel proxy derived temperatures showed significantly warmer tropics during past greenhouse climates. The low-gradient problem, i.e. the very warm polar regions with respect to present day, is still an issue for state-of-the-art climate models.
The Paleocene, or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek παλαιός palaiós meaning "old" and the Eocene Epoch, translating to "the old part of the Eocene".
Eocene Thermal Maximum 2 (ETM-2), also called H-1 or Elmo, was a transient period of global warming that occurred around 54 Ma. It was the second major hyperthermal that punctuated long-term warming from the Late Paleocene through the Early Eocene.
The Cretaceous Thermal Maximum (CTM), also known as Cretaceous Thermal Optimum, was a period of climatic warming that reached its peak approximately 90 million years ago (90 Ma) during the Turonian age of the Late Cretaceous epoch. The CTM is notable for its dramatic increase in global temperatures characterized by high carbon dioxide levels.
The Cenomanian-Turonian boundary event, also known as the Cenomanian-Turonian extinction, Cenomanian-Turonian Oceanic Anoxic Event, and referred to also as the Bonarelli Event or Level, was an anoxic extinction event in the Cretaceous period. The Cenomanian-Turonian oceanic anoxic event is considered to be the most recent truly global oceanic anoxic event in Earth's geologic history. There was a large carbon cycle disturbance during this time period, signified by a large positive carbon isotope excursion. However, apart from the carbon cycle disturbance, there were also large disturbances in the ocean's nitrogen, oxygen, phosphorus, sulphur, and iron cycles.
The Middle Eocene Climatic Optimum (MECO), also called the Middle Eocene Thermal Maximum (METM), was a period of very warm climate that occurred during the Bartonian, from around 40.5 to 40.0 Ma. It marked a notable reversal of the overall trend of global cooling that characterised the Middle and Late Eocene.
Bridget S. Wade is a British micropalaeontologist who is a professor at the University College London. Her research considers Cenozoic climate change, which she investigates by studying preserved planktonic foraminifera. Wade was a guest on the 2020 Royal Institution Christmas Lectures.
Global paleoclimate indicators are the proxies sensitive to global paleoclimatic environment changes. They are mostly derived from marine sediments. Paleoclimate indicators derived from terrestrial sediments, on the other hand, are commonly influenced by local tectonic movements and paleogeographic variations. Factors governing the Earth's climate system include plate tectonics, which controls the configuration of continents, the interplay between the atmosphere and the ocean, and the Earth's orbital characteristics. Global paleoclimate indicators are established based on the information extracted from the analyses of geologic materials, including biological, geochemical and mineralogical data preserved in marine sediments. Indicators are generally grouped into three categories; paleontological, geochemical and lithological.
Pulleniatina obliquiloculata is a planktonic foraminifera, one of the two extant species for the genus Pulleniatina, first occurrence within N19 zone. Widely tropical-subtropical marine plankton, pelagic inhabitants of deep waters.