The end-Triassic extinction is characterized by major losses in both terrestrial and marine diversity, setting the stage for dinosaurs to dominate Earth for the next 136 million years. Despite the approximate coincidence between this extinction and flood basalt volcanism, existing geochronologic dates have insufficient resolution to confirm eruptive rates required to induce major climate perturbations. Here, we present new zircon uranium-lead (U-Pb) geochronologic constraints on the age and duration of flood basalt volcanism within the Central Atlantic Magmatic Province. This chronology demonstrates synchroneity between the earliest volcanism and extinction, tests and corroborates the existing astrochronologic time scale, and shows that the release of magma and associated atmospheric flux occurred in four pulses over about 600,000 years, indicating expansive volcanism even as the biologic recovery was under way.T he approximate temporal coincidence between the five major extinction events over the past 542 million years and the eruption of large igneous provinces (LIPs) has led to speculation that environmental perturbations generated by the emplacement of large volumes of magma and associated outgassing over short periods of time triggered each global biologic crisis (1). Establishing an exact link between extinctions and LIP eruptions has proved difficult because of the geographic separation between LIP volcanic deposits and stratigraphic sequences preserving evidence of the extinction. In most cases, uncertainties on radioisotopic dates used to correlate between geographically separated study areas exceed the duration of both the extinction interval and LIP volcanism by an order of magnitude. This hinders evaluation of any relationship between magmatism and extinction and precludes accurate estimates of volcanic effusion rates, associated volatile release, and extinction mechanisms.The end-Triassic extinction (ETE)-marked within early Mesozoic basins of eastern North America by a dramatic turnover in fossil pollen, spores (sporomorphs), and vertebrates (2)-is one of the largest Phanerozoic mass extinctions, occurring just before the Triassic-Jurassic boundary (3, 4), and has long been thought to be associated with the eruptions of the Central Atlantic Magmatic Province (CAMP) (5, 6). CAMP is the most aerially extensive LIP on Earth, and with volume estimates between 2-3 × 10 6 km 3 , it ranks as one of the most voluminous (7) (Fig. 1). Remnants of CAMP are found on four continents and consist primarily of continental thoeliitic basalts emplaced as subaerial flows and intrusive bodies during rifting of the Pangean supercontinent and incipient formation of the Atlantic Ocean basin (Fig. 1) fig. S1) prevents estimation of the volume of magma erupted over unit time, a critical factor for evaluating extinction mechanisms such as CO 2 -induced global warming (12, 13) ocean acidification (14, 15), or sulfur aerosol-induced "volcanic winters" (16). U-Pb Geochronology of CAMP Flows and IntrusivesHere, we present zirco...

New high-precision U/Pb geochronology from volcanic ashes shows that the Triassic-Jurassic boundary and end-Triassic biological crisis from two independent marine stratigraphic sections correlate with the onset of terrestrial flood volcanism in the Central Atlantic Magmatic Province to <150 ka. This narrows the correlation between volcanism and mass extinction by an order of magnitude for any such catastrophe in Earth history. We also show that a concomitant drop and rise in sea level and negative delta(13)C spike in the very latest Triassic occurred locally in <290 ka. Such rapid sea-level fluctuations on a global scale require that global cooling and glaciation were closely associated with the end-Triassic extinction and potentially driven by Central Atlantic Magmatic Province volcanis

A working timeline for the history of ordinary chondrites includes chondrule formation as early as 0-2 Ma after our Solar System's earliest forming solids (CAIs), followed by rapid accretion into undifferentiated planetesimals that were heated internally by 26 Al decay and cooled over a period of tens of millions of years. There remains conflict, however, between metallographic cooling rate (Ni-metal) and radioisotopic thermochronometric data over the sizes and lifetimes of the chondrite parent bodies, as well as the timing of impact related disruptions. The importance of establishing the timing of parent body disruption is heightened by the use of meteorites as recorders of asteroid belt wide disruption events and their use to interpret Solar System dynamical models. Here we attempt to resolve these records by contributing new 207 Pb-206 Pb data obtained on phosphates isolated from nine previously unstudied ordinary chondrites. These new results, along with previously published Pb-phosphate, Ni-metal and thermometry data, are interpreted with a series of numerical models designed to simulate the thermal evolution for a chondrite parent body that either remains intact or is disrupted by impact prior to forming smaller unsorted "rubble piles". Our thermal model and previously published thermometry data limit accretion time to 2.05-2.25 Ma after CAIs. Measured Pb-phosphate data place minimum estimates on parent body diameters of ~260-280 km for both the L and H chondrite parent bodies. They also consistently show that petrologic Type 6 (highest thermal metamorphism) chondrites from both the H and L bodies have younger ages and, therefore, cooled more slowly than Type 5 (lesser metamorphism) chondrites. This is interpreted as evidence for Type 5 chondrite origination from shallower depths than Type 6 chondrites within initially concentrically zoned bodies. This contrasts metallographic cooling rate data that are inconsistent with such a simple onion shell scenario. One model that can reconcile these two data sets takes into account subtle differences in temperature to which each system responds. This working model requires that disruption occur early enough such that the Ni-metal system can record the cooling rate associated with a rubble pile (<70 Ma), yet late enough that the Pb-phosphate system can record an onion shell structure (>30 Ma). For this 30-70 Ma timeline, reaccretion into smaller rubble piles will ensure that the originally deeply buried and hot Type 6 samples will always cool faster as a result of disruption, yielding nearly uniform ages that record the time of parent body disruption. This is consistent with the available Pb-phosphate data, where all but one Type 6 chondrite (H, n=3; L, n=4) yields a cooling age within a narrow 4505 ± 5 Ma timeframe. These data collectively imply that both the H and L chondrite parent bodies were catastrophically disrupted at ~60 Ma. In addition, combined Ni-metal and Pb-phosphate models confirm that a subset of Type 4 chondrites record early rapid cooling likely ass...

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