The Weissert Event, also referred to as the Weissert Thermal Excursion (WTX), [1] was a hyperthermal event that occurred in the Valanginian stage of the Early Cretaceous epoch. [2] This thermal excursion occurred amidst the relatively cool Tithonian-early Barremian Cool Interval (TEBCI). [1] Its termination marked an intense cooling event, [3] potentially even an ice age. [4]
The start of the WTX has been astrochronologically dated by one study to 134.50 ± 0.19 million years ago (Ma), with its positive δ13C excursion being found to last until 133.96 ± 0.19 Ma and the plateau phase of elevated δ13C values until 132.44 ± 0.19 Ma. [5] However, astrochronological studies of sediments in the Vocontian Basin have yielded a duration of 2.08 Myr, with the positive δ13C excursion being 0.94 Myr in duration and the δ13C plateau being 1.14 Myr. [6] A different study concludes the WTX lasted for about 1.4 million years (Myr) based on the chronological length of the high δ13C plateau observed over its course in the Bersek Marl Formation of Hungary. [7]
An addition of carbon dioxide into the atmosphere via the activity of the Paraná-Etendeka Large Igneous Province (PE-LIP) is generally accepted as the leading candidate for what sparked the WTX, [2] although this is not universally accepted, with some reconstructed geochronologies showing a lack of causality between the emplacement of the PE-LIP and the onset of the WTX. [4] The prolonged, drawn out manner in which the PE-LIP erupted has been brought up as a further argument against its emplacement as the driving perturbation causing the WTX. [8]
The WTX resulted in a rapid global temperature increase during the otherwise mild TEBCI. [1] The sharp jump in global temperatures during this hyperthermal event was accompanied by oceanic anoxia. [9] However, unlike other oceanic anoxic events, the WTX is not associated with widespread black shale deposits. [10] Nannoconids experienced a decline at the onset of the WTX resulting from marine regression, but bloomed in abundance later on in the event as ocean productivity skyrocketed. [11] In the Vocontian Basin, the WTX is associated with an increase in marlstones. [12] At the end of the WTX, temperatures cooled by ~1–2 °C based on the results of palaeothermometry done in southern France, whereas the Boreal Ocean and its surroundings cooled by as much as 4 °C. [3] Geochemical records of 187Os/188Os point to an increase in unradiogenic osmium flux into the ocean, suggesting the occurrence of silicate weathering of PE-LIP basalts during this slice of time, providing the most likely explanation for the temperature drop. [13] Some studies have suggested that a transient ice age with limited but significant polar ice caps occurred in the aftermath of the WTX, [4] [14] although the lack of a positive δ18Oseawater excursion during the latest Valanginian interval of cooling and the presence instead of a very slightly negative excursion calls into question the existence of any significant polar ice growth. [8]
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.
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 Triassic is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.
The Triassic–Jurassic (Tr-J) extinction event (TJME), often called the end-Triassic extinction, was a Mesozoic extinction event that marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago, and is one of the top five major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, the entire class of conodonts and 23–34% of marine genera disappeared. On land, all archosauromorphs other than crocodylomorphs, pterosaurs, and non-avian dinosaurs became extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Some remaining non-mammalian therapsids and many of the large temnospondyl amphibians had become extinct prior to the Jurassic as well. However, there is still much uncertainty regarding a connection between the Tr-J boundary and terrestrial vertebrates, due to a lack of terrestrial fossils from the Rhaetian (uppermost) stage of the Triassic. Plants, crocodylomorphs, dinosaurs, pterosaurs and mammals were left largely untouched; this allowed the dinosaurs, pterosaurs, and crocodylomorphs to become the dominant land animals for the next 135 million years.
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).
The Early Cretaceous or the Lower Cretaceous is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 Ma and 145.0 ± 4 Ma. It is preceded by the Kimmeridgian and followed by the Berriasian.
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.6 ± 2.0 Ma. The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceous and precedes the Hauterivian Stage of the Lower Cretaceous.
The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.6 ± 2 Ma and 125.77. The Hauterivian is preceded by the Valanginian and succeeded by the Barremian.
The Paraná-Etendeka Large Igneous Province (PE-LIP) (or Paraná and Etendeka Plateau; or Paraná and Etendeka Province) is a large igneous province that includes both the main Paraná traps (in Paraná Basin, a South American geological basin) as well as the smaller severed portions of the flood basalts at the Etendeka traps (in northwest Namibia and southwest Angola). The original basalt flows occurred 136 to 132 million years ago. The province had a post-flow surface area of 1,000,000 square kilometres (390,000 sq mi) and an original volume projected to be in excess of 2.3 x 106 km3.
The Lau event was the last of three relatively minor mass extinctions during the Silurian period. It had a major effect on the conodont fauna, but barely scathed the graptolites, though they suffered an extinction very shortly thereafter termed the Kozlowskii event that some authors have suggested was coeval with the Lau event and only appears asynchronous due to taphonomic reasons. It coincided with a global low point in sea level caused by glacioeustasy and is closely followed by an excursion in geochemical isotopes in the ensuing late Ludfordian faunal stage and a change in depositional regime.
In geochemistry, paleoclimatology, and paleoceanography δ13C is an isotopic signature, a measure of the ratio of the two stable isotopes of carbon—13C and 12C—reported in parts per thousand. The measure is also widely used in archaeology for the reconstruction of past diets, particularly to see if marine foods or certain types of plants were consumed.
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 Carnian pluvial episode (CPE), often called the Carnian pluvial event, was a period of major change in global climate that coincided with significant changes in Earth's biota both in the sea and on land. It occurred during the latter part of the Carnian Stage, a subdivision of the late Triassic period, and lasted for perhaps 1–2 million years.
The Toarcian extinction event, also called the Pliensbachian-Toarcian extinction event, the Early Toarcian mass extinction, the Early Toarcian palaeoenvironmental crisis, or the Jenkyns Event, was an extinction event that occurred during the early part of the Toarcian age, approximately 183 million years ago, during the Early Jurassic. The extinction event had two main pulses, the first being the Pliensbachian-Toarcian boundary event (PTo-E). The second, larger pulse, the Toarcian Oceanic Anoxic Event (TOAE), was a global oceanic anoxic event, representing possibly the most extreme case of widespread ocean deoxygenation in the entire Phanerozoic eon. In addition to the PTo-E and TOAE, there were multiple other, smaller extinction pulses within this span of time.
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 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.
The Steptoean positive carbon isotope excursion (SPICE) is a global chemostratigraphic event which occurred during the upper Cambrian period between 497 and 494 million years ago. This event corresponds with the ICS Guzhangian-Paibian Stage boundary and the Marjuman-Steptoean stage boundary in North America. The general signature of the SPICE event is a positive δ13C excursion, characterized by a 4 to 6 ‰ shift in δ13C values within carbonate successions around the world. SPICE was first described in 1993, and then named later in 1998. In both these studies, the SPICE excursion was identified and trends were observed within Cambrian formations of the Great Basin of the western United States.
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