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Triggering of the Largest Deccan Eruptions by the Chicxulub Impact

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Triggering of the Largest Deccan Eruptions by the Chicxulub Impact Geological Society of America Bulletin, published online on 30 April 2015 as doi:10.1130/B31167.1 Triggering of the largest Deccan eruptions by the Chicxulub impact Mark A. Richards1,†, Walter Alvarez1,2, Stephen Self1, Leif Karlstrom3, Paul R. Renne1,4, Michael Manga1, Courtney J. Sprain,1,4 Jan Smit,2,5 Loÿc Vanderkluysen6, and Sally A. Gibson7 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA 2Osservatorio Geologico di Coldigioco, Contrada Coldigioco 4, 62021 Apiro (MC), Italy 3Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA 4Berkeley Geochronology Center, Berkeley, California 94709, USA 5Department of Sedimentary Geology, Vrije Universeit, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands 6Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, Pennsylvania 19104, USA 7Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK ABSTRACT cate that at approximately Chicxulub/Creta- fl ood basalt eruptions from the Siberian Traps ceous-Paleogene time, a huge pulse of mantle and Emeishan Traps were approximately coin- New constraints on the timing of the Cre- plume–derived magma passed through the cident with the extinctions at end-Permian and taceous-Paleogene mass extinction and the crust with little interaction and erupted to end–middle-Permian (end-Guadalupian) time, Chicxulub impact, together with a particu- form the most extensive and voluminous lava respectively, and the Central Atlantic magmatic larly voluminous and apparently brief erup- fl ows known on Earth. High-precision ra- province was erupted at approximately the Tri- tive pulse toward the end of the “main-stage” dioisotopic dating of the main-phase Deccan assic-Jurassic boundary (Courtillot and Renne, eruptions of the Deccan continental fl ood ba- fl ood basalt formations may be able either to 2003). Also, there is no compelling evidence salt province suggest that these three events confi rm or reject this hypothesis, which in to date for other impact/extinction associations may have occurred within less than about a turn might help to determine whether this (Alvarez, 2003). Moreover, constraints on the hundred thousand years of each other. Par- singular outburst within the Deccan Traps likely “kill mechanisms” for these mass extinc- tial melting induced by the Chicxulub event (and possibly volcanic eruptions worldwide) tions (e.g., CO2 outgassing, launching of sulfur does not provide an energetically plausible contributed signifi cantly to the Cretaceous- gas leading to sulfate aerosols) are compatible explanation for this coincidence, and both Paleogene extinction. with both impact and volcanic causes (Self et geochronologic and magnetic-polarity data al., 2006, 2014; Black et al., 2014). show that Deccan volcanism was under way INTRODUCTION Recent high-precision 40Ar-39Ar dating of well before Chicxulub/Cretaceous-Paleogene the Cretaceous-Paleogene boundary in the Hell time. However, historical data document that The hypothesis that the ca. 66 Ma Creta- Creek area (Montana, USA) and of the Chicxu- eruptions from existing volcanic systems can ceous-Paleogene mass extinction event was lub (Yucatán, Mexico) impact ejecta shows that be triggered by earthquakes. Seismic model- caused by an extraterrestrial impact (Alvarez et these two events are time-coincident within ing of the ground motion due to the Chicxu- al., 1980; Smit and Hertogen, 1980) stands in ~32,000 yr precision at ca. 66.04 Ma (Renne et lub impact suggests that the impact could contrast with a competing hypothesis that the al. 2013), and both fall within paleomagnetic have generated seismic energy densities of Cretaceous-Paleogene extinction was caused chron 29R (Chenet et al., 2007; Ogg, 2012). order 0.1–1.0 J/m3 throughout the upper by the Deccan Traps continental fl ood basalt Radioisotopic constraints on Deccan-related ~200 km of Earth’s mantle, suffi cient to trig- eruptions (Courtillot et al., 1988, 2000; Cour- volcanism are much less precise, but they show ger volcanic eruptions worldwide based upon tillot and Renne, 2003). The impact hypothesis that early- and late-stage alkalic eruptions pre- comparison with historical examples. Trig- is supported by the presence of impact depos- ceded and postdated Cretaceous-Paleogene gering may have been caused by a transient its at the Cretaceous-Paleogene boundary, the time by at least several million years (Basu et increase in the effective permeability of the discovery of the ~180-km-diameter Chicxulub al., 1993). Moreover, the Cretaceous-Paleo- existing deep magmatic system beneath the crater in Yucatán, Mexico (Hildebrand et al., gene boundary is thought to have occurred Deccan province, or mantle plume “head.” 1991; Schulte et al., 2010), and increasingly within chron 29R, whereas the “main-phase” It is therefore reasonable to hypothesize that precise radioisotopic dating (Renne et al., 2013) tholeiitic basalt eruptions of the Western Ghats the Chicxulub impact might have triggered showing that the Chicxulub impact iridium Province, during which at least 90% of Dec- the enormous Poladpur, Ambenali, and Ma- layer and the Cretaceous-Paleogene boundary can lavas are thought to have erupted, began habaleshwar (Wai Subgroup) lava fl ows, are essentially coincident in time. The Deccan during (or before) chron 30N and ended during which together may account for >70% of the continental fl ood basalts started several mil- chron 29N (Chenet et al., 2008, 2009). Thus, Deccan Traps main-stage eruptions. This hy- lion years prior to the Cretaceous-Paleogene Deccan volcanism was well under way at the pothesis is consistent with independent strati- boundary (Courtillot and Renne, 2003) and time of the Cretaceous-Paleogene extinction graphic, geochronologic, geochemical, and were therefore not initiated by the Chicxulub and Chicxulub impact time, and it continued tectonic constraints, which combine to indi- impact. However, the volcanic hypothesis for after Cretaceous-Paleogene time (Fig. 1A). the Cretaceous-Paleogene extinction has per- Recent studies of Deccan volcanic stratigra- †[email protected] sisted for several reasons: Massive continental phy (Fig. 1A) have indicated an extraordinary GSA Bulletin; Month/Month 2015; v. 1xx; no. X/X; p. 1–14; doi: 10.1130/B31167.1; 7 fi gures; 1 table; Data Repository item 2015164. For permission to copy, contact [email protected] 1 © 2015 Geological Society of America; Gold Open Access: This paper is published under the terms of the CC-BY license. Geological Society of America Bulletin, published online on 30 April 2015 as doi:10.1130/B31167.1 Richards et al. ** Group Sub-group Formation Age (Ma) * Chron Nd Dike 64636261 65 66 67 68 69 70 crust mantle orientations *** Desur N Panhala 29N Wai Mahabaleshwar Ambenali n = 34 Poladpur Age of K-Pg boundary (66.0 Ma in Geological Ambenali + Time scale 2012; 66.04 Bushe Ma in Renne et al., 2013) Mahabaleshwar and span of Chron 29R (Nasik-Pune) Lonavala (66.398-65.688 Ma in GTS 2012). Kandala 29R Chicxulub Impact? Kalsubai 29R (Nasik-Pune) Bhimashankar N Thakurvadi Deccan Basalt Group Deccan Kalsubai Neral n = 46 ? Igatpuri Jawhar N Narmada / Rajpipla > 67 Ma 30N (i) (stratigraphic position uncertain) (ii) 30N (iii) (iv) n = 96 * Ages with 2σ errors, recalculated to the same calibration as in Renne et al., 2013. -20 -10 0 +10 (v) (Age of K-Pg boundary, 66.04 Ma, is calculated on the same basis.) ** Ranges of previous data from Narmada-Tapi Black age symbols = Plateau ages Age symbols equally spaced from Vanderkluysen et al., 2011, judged to be meaningful oldest to youngest within each formation; their fig. 4, top and middle. symbols are not in stratigraphic order Gray age symbols = Plateau ages *** Vanderkluysen et al., within formations. possibly biased by alteration (2009) Chenet et al. 2011, fig. 11c, e, f. A and/or recoil artifacts Age sources are given in Table 1. Figure 1. (A) (i) Deccan subgroups and formations (Chenet et al., 2008). Additional information includes (ii) radioisotopic ages (see Table 1 for sources) with 2σ uncertainties indicated by error bars, (iii) geomagnetic polarity assuming all reversed-polarity formations are within chron ε 29R, (iv) Nd ranges (Vanderkluysen et al., 2011), and (v) orientations of associated dikes (Vanderkluysen et al., 2011). Relatively minor-volume Narmada/Rajpipla basalts occurred during earlier phases of Deccan volcanism along the east-west Narmada Rift, and these clearly predate the Chicxulub impact. Gray area in column (ii) indicates approximate time range of chron 29R. (Continued on following page.) pulse of basaltic volcanism that accounts for case, it seems reasonable to assume that if the not small—perhaps on the order of one chance more than half the total volume of Deccan vol- Deccan Traps eruptions contributed to the main in ~10 (that is, 20–30 Ma/2–3 Ma). However, canism and includes the huge Poladpur, Ambe- Cretaceous-Paleogene extinctions, then the Wai if, as the evidence presented herein suggests, nali, and Mahabaleshwar Formations within the Subgroup pulse of eruptions was the likely cul- the Chicxulub impact occurred within only Wai Subgroup of the Deccan continental fl ood prit. Although the timing and duration of the ~100,000 yr or so of the Wai Subgroup out- basalt (Self et al., 2006). Magnetostratigraphic Kalsubai, Lonavala, and Wai Subgroup forma- burst of Deccan volcanism, then the odds of this constraints have been interpreted to suggest that tions are not well constrained, it also appears occurring by chance would be an order of mag- much of the Wai Subgroup volcanism occurred likely that the Cretaceous-Paleogene boundary nitude smaller, i.e., one chance in ~100. Such prior to the 29R/29N reversal during a brief and the Chicxulub impact may have occurred at small odds provide a new impetus to explore interval of time, perhaps as little as ~100,000 yr or just before the onset of the huge Wai Sub- plausible causal links. (Chenet et al., 2008, 2009), but not likely more group eruptions (e.g., Keller et al., 2012).
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