Amadeus Event

Last updated

The Amadeus Event (OAE1c) was an oceanic anoxic event (OAE). It occurred 106 million years ago (Ma), during the Albian age of the Cretaceous period, [1] in a climatic interval known as the Middle Cretaceous Hothouse (MKH). [2]

Contents

Extent and duration

OAE1c lasted for approximately 567 kyr. [3] Environmental conditions across much of the globe facilitated the formation of dysaerobic waters, although OAE1c varied in its nature and magnitude depending on region. Shallow shelf environments in the Gulf of Mexico were unaffected by anoxia. [4]

Causes

The MKH was one of the hottest intervals of the entire Phanerozoic eon, with OAE1c occurring during a particularly warm time known as the Amadeus Thermal Maximum; these conditions were prime for generating anoxic waters. [2] Orbital forcing is considered the most likely cause of OAE1c, as most geochemical changes observed across the OAE1c interval were in lockstep with Milankovitch cycles. [5] Black shale deposition occurs during minima in the axial precession cycle, when waters were less saline and/or warmer. Increased influxes of terrestrial runoff would have induced stratification of the water column, inhibiting mixing of water masses at different depths. Peaks in carbonate deposition occurred during precession maxima, when precipitation and evaporation rates were lower and saline deep water bodies were able to form, preventing stratification. [1] The lack of anomalous osmium enrichments of any significance rules out large igneous province volcanism as a suspected causal factor, which is known to have caused other Cretaceous OAEs like OAE1a and OAE2. [6]

Effects

Unlike many other OAEs across the MKH, the black shales deposited during OAE1c were made up of type III kerogen and consisted primarily of terrestrial organic matter, in contrast to the type II kerogen made up of marine organic matter that the black shales of OAE1a, OAE1b, OAE1d, and OAE2 were composed of. Also unlike other MKH OAEs, no significant radiations or extinctions of radiolarians occurred as a result of OAE1c. [7]

See also

Related Research Articles

The Cretaceous is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide.

<span class="mw-page-title-main">Extinction event</span> Widespread and rapid decrease in the biodiversity on Earth

An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity.

Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the Earth's orbit around the sun. These orbital changes modify the total amount of sunlight reaching the Earth by up to 25% at mid-latitudes. In this context, the term "forcing" signifies a physical process that affects the Earth's climate.

<span class="mw-page-title-main">Anoxic event</span> Historic oxygen depletion events in Earths oceans

Oceanic anoxic events or anoxic events (anoxia conditions) describe periods 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."

<span class="mw-page-title-main">Aptian</span> Fifth age of the Early Cretaceous

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma, approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.

The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma. The Coniacian is preceded by the Turonian and followed by the Santonian.

The Ontong Java Plateau (OJP) is a massive oceanic plateau located in the southwestern Pacific Ocean, north of the Solomon Islands. The OJP was formed around 120 million years ago (Ma) with a much smaller volcanic event around 90 Ma. Two other southwestern Pacific plateaus, Manihiki and Hikurangi, now separated from the OJP by Cretaceous oceanic basins, are of similar age and composition and probably formed as a single plateau and a contiguous large igneous province together with the OJP. When eruption of lava had finished, the Ontong Java–Manihiki–Hikurangi plateau covered 1% of Earth's surface and represented a volume of 80 million km3 (19 million cu mi) of basaltic magma. This "Ontong Java event", first proposed in 1991, represents the largest volcanic event of the past 200 million years, with a magma eruption rate estimated at up to 22 km3 (5.3 cu mi) per year over 3 million years, several times larger than the Deccan Traps. The smooth surface of the OJP is punctuated by seamounts such as the Ontong Java Atoll, one of the largest atolls in the world.

Sapropel is a term used in marine geology to describe dark-coloured sediments that are rich in organic matter. Organic carbon concentrations in sapropels commonly exceed 2 wt.% in weight.

The Kačák Event, also known as the Kačák-otomari Event, is a widely recognised bioevent or series of events that occurred close to the end of the Eifelian Age of the Middle Devonian Epoch. It involved a global eustatic rise in sea level and ecological turnover. It was named for the Kačák Member of the Srbsko Formation in Bohemia, where it is represented by a black shale interval within a sequence of limestone. In marine environments, this appears as an anoxic event, often forming potential hydrocarbon source rocks such as the Marcellus Shale. Within the Old Red Sandstone continent, it is represented by the Achanarras lake, the deepest and most widespread lake that developed within the Orcadian Basin. The event is associated with significant extinctions, particularly amongst the Ammonoidea.

<span class="mw-page-title-main">Cretaceous Thermal Maximum</span> Period of climatic warming that reached its peak approximately 90 million years ago

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.

<span class="mw-page-title-main">Tropic Shale</span>

The Tropic Shale is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, including Nothronychus graffami. The Tropic Shale is a stratigraphic unit of the Kaiparowits Plateau of south central Utah. The Tropic Shale was first named in 1931 after the town of Tropic where the Type section is located. The Tropic Shale outcrops in Kane and Garfield counties, with large sections of exposure found in the Grand Staircase–Escalante National Monument.

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, was one of two anoxic extinction events 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. Selby et al. in 2009 concluded the OAE 2 occurred approximately 91.5 ± 8.6 Ma, though estimates published by Leckie et al. (2002) are given as 93–94 Ma. The Cenomanian-Turonian boundary has been refined in 2012 to 93.9 ± 0.15 Ma. 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 nitrogen, oxygen, phosphorus, and sulphur cycles of the ocean.

Euxinia or euxinic conditions occur when water is both anoxic and sulfidic. This means that there is no oxygen (O2) and a raised level of free hydrogen sulfide (H2S). Euxinic bodies of water are frequently strongly stratified, have an oxic, highly productive, thin surface layer, and have anoxic, sulfidic bottom water. The word euxinia is derived from the Greek name for the Black Sea (Εὔξεινος Πόντος (Euxeinos Pontos)) which translates to "hospitable sea". Euxinic deep water is a key component of the Canfield ocean, a model of oceans during the Proterozoic period (known as the Boring Billion) proposed by Donald Canfield, an American geologist, in 1998. There is still debate within the scientific community on both the duration and frequency of euxinic conditions in the ancient oceans. Euxinia is relatively rare in modern bodies of water, but does still happen in places like the Black Sea and certain fjords.

<span class="mw-page-title-main">Ipubi Formation</span>

The Ipubi Formation is the middle geological formation of the Santana Group, the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The formation is dated to the Aptian to Albian stages of the Early Cretaceous, unconformably overlying the Crato Formation and unconformably overlain by the Romualdo Formation, formerly known as the Romualdo Member of the Santana Formation. The averaging 15 metres (49 ft) thick Ipubi Formation comprises shales and sandstones in the lower section and evaporites in the upper part of the formation, deposited in a transgressive to highstand lacustrine environment in the Araripe rift basin.

The Calcare di Sogno is a geological formation in Italy, dated to roughly between 182-169 million years ago and covering the Lower Toarcian-Late Bajocian stagess of the Jurassic Period in the Mesozoic Era. Thallatosuchian remains are known from the formation, as well fishes and other taxa.

The Toarcian Oceanic Anoxic Event (TOAE), also known as the Jenkyns Event, the Pliensbachian-Toarcian extinction event, or the Early Toarcian mass extinction, was a global anoxic event during the early part of the Toarcian age, approximately 183 million years ago, during the Early Jurassic. Occurring during the supergreenhouse climate of the Early Toarcian Thermal Maximum (ETTM), the TOAE is believed to be possibly the most extreme case of widespread ocean deoxygenation in the entire Phanerozoic eon. It is documented by a high amplitude negative carbon isotope excursion, as well as the widespread deposition of black shales and a major extinction event of marine life associated with a major rise in global temperatures. This anoxic event was responsible for the deposition of commercially extracted oil shales, particularly in China.

The Selli Event, also known as OAE1a, was an oceanic anoxic event (OAE) of global scale that occurred during the Aptian stage of the Early Cretaceous, about 120.5 million years ago (Ma). The OAE is associated with large igneous province volcanism and an extinction event of marine organisms driven by global warming, ocean acidification, and anoxia.

The Breistroffer Event (OAE1d) was an oceanic anoxic event (OAE) that occurred during the middle Cretaceous period, specifically in the latest Albian, around 101 million years ago (Ma).

The Paquier Event (OAE1b) was an oceanic anoxic event (OAE) that occurred around 111 million years ago (Ma), in the Albian geologic stage, during a climatic interval of Earth's history known as the Middle Cretaceous Hothouse (MKH).

The Mid-Cenomanian Event (MCE) was an oceanic anoxic event that took place during the middle Cenomanian, as its name suggests, around 96.5 Ma.

References

  1. 1 2 Galeotti, Simone; Sprovieri, Mario; Coccioni, Rodolfo; Bellanca, Adriana; Neri, Rodolfo (15 January 2023). "Orbitally modulated black shale deposition in the upper Albian Amadeus Segment (central Italy): a multi-proxy reconstruction". Palaeogeography, Palaeoclimatology, Palaeoecology . 190: 441–458. doi:10.1016/S0031-0182(02)00618-1 . Retrieved 10 June 2023.
  2. 1 2 Scotese, Christopher Robert; Song, Haijun; Mills, Benjamin J. W.; Van der Meer, Douwe G. (April 2021). "Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years". Earth-Science Reviews . 215: 1–47. doi:10.1016/j.earscirev.2021.103503 . Retrieved 10 June 2023.
  3. ↑ Liu, Xuan; Zhang, Yi; Han, Kaibo; Batenburg, Sietske J.; Guo, Huifang; Ma, Chao; Yao, Hanwei; Fan, Hanhan; Wu, Qi; Chen, Xi (November 2022). "Chemo- and cyclostratigraphic records of the Albian from the Tethyan Himalaya of southern Tibet, China". Global and Planetary Change . 218. doi:10.1016/j.gloplacha.2022.103955 . Retrieved 10 June 2023.
  4. ↑ Scott, Robert W.; Rush, Natalie; Hojnacki, Rachel; Campbell, Whitney; Wang, Yulun; Lai, Xin (August 2020). "Albian (Lower Cretaceous) carbon isotope chemozones, Texas Comanche Shelf and Mexican Chihuahua Trough: Implications for OAEs". Cretaceous Research . 112: 1–19. doi:10.1016/j.cretres.2020.104453 . Retrieved 10 June 2023.
  5. ↑ Tateo, Fabio; Morandi, Noris; Nicolai, Annarita; Ripepe, Maurizio; Coccioni, Rodolfo; Galeotti, Simone; Baudin, Francois (1 March 2000). "Orbital control on pelagic clay sedimentology; the case of the late Albian "Amadeus Segment" (central Italy)". Bulletin de la Société Géologique de France . 171 (2): 217–228. doi:10.2113/171.2.217 . Retrieved 10 June 2023.
  6. ↑ Matsumoto, Hironao; Coccioni, Rodolfo; Frontalini, Fabrizio; Shirai, Kotaro; Jovane, Luigi; Trindade, Ricardo; Savian, Jairo F.; Koroda, Junichiro (11 January 2022). "Mid-Cretaceous marine Os isotope evidence for heterogeneous cause of oceanic anoxic events". Nature Communications . 13 (1): 239. Bibcode:2022NatCo..13..239M. doi:10.1038/s41467-021-27817-0. PMC   8752794 . PMID   35017487 . Retrieved 13 June 2023.
  7. ↑ Erbacher, Jochen; Thurow, J. (March 1997). "Influence of oceanic anoxic events on the evolution of mid-Cretaceous radiolaria in the North Atlantic and western Tethys". Marine Micropaleontology. 30 (1–3): 139–158. doi:10.1016/S0377-8398(96)00023-0 . Retrieved 14 June 2023.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.