End-Triassic ExtinctionBy: Donald Maute IIIGeneral InformationTriassic Period dates from about 252 to 201 MaEnd Triassic mass extinction occurred at the Triassic-Jurassic boundary around 200 MaOne of the Big Five most severe mass extinctions in history76% percent of all marine and terrestrial species perished20% of all taxonomic families perished

Particularly affected ammonoids and conodontsConodonts and labrynthodont amphibians became completely extinctOnly the phylloceratid ammonoids survived Conodonts and ammonoids served as important index fossils for Triassic strataMany families of brachiopods, gastropods, bivalves, corals, sponges, marine reptiles and amphibians became extinct as wellThe only marine reptiles to survive were ichthyosaurs and plesiosaurs

Marine fauna

Phylloceratid ammoniods are the only group of ammoniods to survive the End Triassic Extinction. They later radiated and diversified into later ammoniods, but all died off in the K-Pg extinction

Terrestrial Fauna and FloraLots of land vertebrates disappearedHowever, dinosaurs, pterosaurs, crocodiles, turtles, mammals and fish were hardly affected.All the ecological niches were filled relatively quickly by dinosaurs, and is thought to have helped dinosaurs rise to become the dominant terrestrial faunaMost plants spores and pollen show no significant changes when this event took place

phytosauraetosaurornithosuchidaerauisuchianCauses?Highly debated, nobody has a definite answerMany believe that the main factors of this mass extinction were climate change, rising sea levels, ocean anoxia, and large amounts of volcanism associated with rifting. More minorly a possible bolide impact. It could in fact be a combination of these factors.Large amounts of CO2, SO2 and other toxic gasses are emitted from the volcanic activity that associated with tectonic activity-rifting of Pangaea.Thought to have contributed to the greenhouse effect, raising temperatures and acidifying oceansCauses?Possible that increase in CO2 in the atmosphere caused a warming of the atmosphere and the oceans, which melted underwater methane clathrates and released the trapped methane. Methane is a much more efficient greenhouse gas than CO2, this would result in temperatures raising significantlyThe most accepted theory is linked to the Central Atlantic Magmatic Province (CAMP), which is formed during the breakup of Pangaea. The massive volcanism caused sea levels to rise, ocean anoxia, ocean acidification, climatic changes and releasing of toxic compounds on a high degree.CAMP seems to be the root cause, with all of the other factors happening because of it

CH4 vs CO2

What are Methane Clathrates again?Methane clathrates are bubbles of methane trapped in underwater crystalline H2O (ice)Requires temperatures to stay cold so the methane will stay trappedIf the oceanic temperature increases enough, the methane clathrates will melt, releasing the CH4

POP QUIZQuestion: When was the most recent time the climate was at a thermal maximum?POP QUIZAnswer: Paleocene-Eocene Thermal Maximum(PETM) 56 Ma

With this being said, methane clathrates have had a long time to regenerate, so it is possible in the near (geologically speaking) future they will melt again and cause temperatures to rise significantly and maybe even cause an extinction.EvidenceStratigraphic sections from Europe, North and South America indicates an absence of carbonate sedimentation at the T-Jr boundaryIt is said volcanogenic maximum of CO2 lead to undersaturation of seawater with respect to aragonite and calcite and suppression of carbonate sedimentation. Lowering the saturation state of seawater with respect to calcium carbonate was most likely a triggering factor for marine life with calcite or aragonite shells to perishThis caused most organisms that secrete aragonite and high-magnesium calcite to perish. For example: all major reef groups had high extinction rates and had an extremely slow recovery.Higher CO2 concentrations in the ocean could lead to a higher CCD and ACD (aragonite compensation depth).EvidenceMarine organisms that did survive had to adapt and secrete the polymorph of aragonite instead; calcite. Shell sizes also dramatically decreasedAragonite is about 1.5 times more dissolvable in seawater than calciteRhaetian=last age in the TriassicLiassic=lower/early Jurassic

EvidenceSome researchers believe that the melting of methane clathrates was a large reason for the extinctionThe CO2 released from the rifting of Pangaea and the CAMP only caused the initial warming of the oceans and atmosphereOnce the ocean was warm enough, the methane clathrates melted and released the CH4 which caused global warming much more rapidlyPublished research indicates that a minimum of 16,000 gigatons of CH4 were released within 10,000 to 20,000 yearsNegative 13C excursions coincide with these eventsU-Pb dating from Zircons correlates these events as wellBolide Impact?Evidence is lacking, no iridium or shocked quartz in the stratigraphic sequence is found from 200 MaManicouagan Crater of Quebec is the closest in timeU-Pb dating of Zircons from this site date the melt rock from the crater to about 214 Ma.This is 14 Ma before the End Triassic Extinction took placeIt is possible that it could have triggered an extinction earlier in the Triassic, but not the End Triassic Mass Extinction

Was it even a mass extinction?Some researchers argue that this wasn't even a mass extinction at all, just a bunch of more minor extinctions

Concluding thoughtsIn my opinion, I think that the melting of methane clathrates are the main cause of this extinction, from the volcanism of the CAMPI feel that the bolide impact does not have enough evidence to be the cause of the extinctionHowever I do feel that it is a mass extinctionQuestions?