scholarly journals An evaluation of Deccan Traps eruption rates using geochronologic data

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 181-198
Author(s):  
Blair Schoene ◽  
Michael P. Eddy ◽  
C. Brenhin Keller ◽  
Kyle M. Samperton

Abstract. Recent attempts to establish the eruptive history of the Deccan Traps large igneous province have used both U−Pb (Schoene et al., 2019) and 40Ar/39Ar (Sprain et al., 2019) geochronology. Both of these studies report dates with high precision and unprecedented coverage for a large igneous province and agree that the main phase of eruptions began near the C30n–C29r magnetic reversal and waned shortly after the C29r–C29n reversal, totaling ∼ 700–800 kyr duration. These datasets can be analyzed in finer detail to determine eruption rates, which are critical for connecting volcanism, associated volatile emissions, and any potential effects on the Earth's climate before and after the Cretaceous–Paleogene boundary (KPB). It is our observation that the community has frequently misinterpreted how the eruption rates derived from these two datasets vary across the KPB. The U−Pb dataset of Schoene et al. (2019) was interpreted by those authors to indicate four major eruptive pulses before and after the KPB. The 40Ar/39Ar dataset did not identify such pulses and has been largely interpreted by the community to indicate an increase in eruption rates coincident with the Chicxulub impact (Renne et al., 2015; Richards et al., 2015). Although the overall agreement in eruption duration is an achievement for geochronology, it is important to clarify the limitations in comparing the two datasets and to highlight paths toward achieving higher-resolution eruption models for the Deccan Traps and for other large igneous provinces. Here, we generate chronostratigraphic models for both datasets using the same statistical techniques and show that the two datasets agree very well. More specifically, we infer that (1) age modeling of the 40Ar/39Ar dataset results in constant eruption rates with relatively large uncertainties through the duration of the Deccan Traps eruptions and provides no support for (or evidence against) the pulses identified by the U−Pb data, (2) the stratigraphic positions of the Chicxulub impact using the 40Ar/39Ar and U−Pb datasets do not agree within their uncertainties, and (3) neither dataset supports the notion of an increase in eruption rate as a result of the Chicxulub impact. We then discuss the importance of systematic uncertainties between the dating methods that challenge direct comparisons between them, and we highlight the geologic uncertainties, such as regional stratigraphic correlations, that need to be tested to ensure the accuracy of eruption models. While the production of precise and accurate geochronologic data is of course essential to studies of Earth history, our analysis underscores that the accuracy of a final result is also critically dependent on how such data are interpreted and presented to the broader community of geoscientists.

2020 ◽  
Author(s):  
Blair Schoene ◽  
Michael P. Eddy ◽  
C. Brenhin Keller ◽  
Kyle M. Samperton

Abstract. Recent attempts to establish the eruptive history of the Deccan Traps large igneous province have used both U-Pb (Schoene et al., 2019) and 40Ar/39Ar (Sprain et al., 2019) geochronology. Both of these studies report dates with high precision and unprecedented coverage for a large igneous province, and agree that the main phase of eruptions began near the C30n-C29r magnetic reversal and waned shortly after the C29r-C29n reversal, totaling ~700-800 ka duration. Nevertheless, the eruption rates interpreted by the authors of each publication differ significantly. The U-Pb dataset was interpreted to indicate four major eruptive pulses, while the 40Ar/39Ar dataset was used to argue for an increase in eruption rates coincident with the Chicxulub impact (Renne et al., 2015; Richards et al., 2015). Although the overall agreement in duration is an achievement for geochronology, the disparate eruption models may act to undermine this achievement in the eyes of the broader geologic community. Here, we generate chronostratigraphic models for both datasets using the same statistical techniques and conclude that 1) age modeling of the 40Ar/39Ar dataset results in constant eruption rates with relatively large uncertainties through the duration of the Deccan Traps, and cannot verify or disprove the pulses identified by the U-Pb data, 2) the stratigraphic position of the Chicxulub impact within the 40Ar/39Ar dataset is much more uncertain than was presented in Sprain et al. (2019), and 3) neither dataset supports an increase in eruption rate as a result of the Chicxulub impact. While the production of precise and accurate geochronologic data is of course essential to studies of Earth History, our analysis underscores that the accuracy of a final result also is critically dependent on how such data are interpreted and presented to the broader community of geoscientists.


Author(s):  
Bryan C. Storey ◽  
Alan P. M. Vaughan ◽  
Teal R. Riley

ABSTRACTEarth history is punctuated by events during which large volumes of predominantly mafic magmas were generated and emplaced by processes that are generally accepted as being, unrelated to ‘normal’ sea-floor spreading and subduction processes. These events form large igneous provinces (LIPs) which are best preserved in the Mesozoic and Cenozoic where they occur as continental and ocean basin flood basalts, giant radiating dyke swarms, volcanic rifted margins, oceanic plateaus, submarine ridges, and seamount chains. The Mesozoic history of Antarctica is no exception in that a number of different igneous provinces were emplaced during the initial break-up and continued disintegration of Gondwana, leading to the isolation of Antarctica in a polar position. The link between the emplacement of the igneous rocks and continental break-up processes remains controversial. The environmental impact of large igneous province formation on the Earth System is equally debated. Large igneous province eruptions are coeval with, and may drive environmental and climatic effects including global warming, oceanic anoxia and/or increased oceanic fertilisation, calcification crises, mass extinction and release of gas hydrates.This review explores the links between the emplacement of large igneous provinces in Antarctica, the isolation of Antarctica from other Gondwana continents, and possibly related environmental and climatic changes during the Mesozoic and Cenozoic.


2009 ◽  
Vol 146 (3) ◽  
pp. 305-308 ◽  
Author(s):  
DOUGAL A. JERRAM ◽  
KATHRYN M. GOODENOUGH ◽  
VALENTIN R. TROLL

The study of volcanic rocks and igneous centres has long been a classic part of geological research. Despite the lack of active volcanism, the British Isles have been a key centre for the study of igneous rocks ever since ancient lava flows and excavated igneous centres were recognized there in the 18th century (Hutton, 1788). This led to some of the earliest detailed studies of petrology. The starting point for many of these studies was the British Palaeogene Igneous Province (BPIP; formerly known as the ‘British Tertiary’ (Judd, 1889), and still recognized by this name by many geologists around the globe). This collection of lavas, volcanic centres and sill/dyke swarms covers much of the west of Scotland and the Antrim plateau of Northern Ireland, and together with similar rocks in the Faroe Islands, Iceland and Greenland forms a world-class Large Igneous Province. This North Atlantic Igneous Province (NAIP) began to form through continental rifting above a mantle plume at c. 60 Ma, and subsequently evolved as North America separated from Europe, creating the North Atlantic Ocean.


Lithosphere ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 40-52 ◽  
Author(s):  
Rajesh K. Srivastava ◽  
Fei Wang ◽  
Wenbei Shi ◽  
Anup K. Sinha ◽  
Kenneth L. Buchan

Abstract Two distinct sets of Cretaceous dolerite dikes intrude the Chhotanagpur gneissic complex of eastern India, mostly within the Damodar Valley Gondwanan sedimentary basins. One dike set trends NNE to ENE, whereas the other set, which includes the prominent Salma dike, trends NW to NNW. One dike from each set in the Raniganj Basin was dated using the 40Ar/39Ar method in order to resolve a controversy concerning the emplacement age of the Salma dike. The NE-trending dike yielded a plateau age of 70.5 ± 0.9 Ma, whereas the NNW-trending Salma dike is much older, with a plateau age of 116.0 ± 1.4 Ma. These results demonstrate that the Salma dike was emplaced at ca. 116 Ma and not at ca. 65 Ma, as suggested in an earlier study. Geochemical characteristics of the two dikes are also distinct and indicate that they belong to previously identified high-Ti and low-Ti dolerite groups, respectively. The observed geochemical characteristics of both dike sets are comparable with the geochemistry of basalts of the Kerguelen Plateau, Bunbury Island, and Rajmahal Group I and suggest a connection to mantle plumes. The new age data presented herein indicate that these two magmatic episodes in the eastern Indian Shield were related to the ca. 120–100 Ma Kerguelen mantle plume and its associated Greater Kerguelen large igneous province and the ca. 70–65 Ma Réunion plume and its associated Deccan large igneous province, respectively.


2020 ◽  
Author(s):  
Urs Schaltegger ◽  
Philipp Widmann ◽  
Nicolas D. Greber ◽  
Luis Lena ◽  
Sean P. Gaynor ◽  
...  

<p>The connection between volcanic activity of large igneous provinces and the respective feedback from environment and biosphere contributing to the carbon cycle has been investigated at the present temporal resolution of high-precision U/Pb dating. Uncertainties of 0.05 % on the <sup>206</sup>Pb/<sup>238</sup>U age from zircon dating allow a resolution of 30-50 ka pulses of magmatic activity; simultaneously, the duration of carbon isotope excursions (CIE) can be determined, the geological boundaries dated, or global sedimentary gaps can be quantified at the same level of precision. This contribution demonstrates with two case studies that we can refine the contemporaneity and start to reliably infer causality of consecutive events at the 10<sup>4</sup> year level.</p><p>Until the Anisian the aftermath of the Permo-Triassic Boundary Mass extinction (PTBME; ~251.94 Ma, Baresel et al., 2017) is characterized by profound fluctuations of the global carbon cycle with amplitudes of up to 8 ‰ in d<sup>13</sup>C<sub>carb</sub> values. These represent large variations in the global climate and biological crises, in particular during the end-Smithian extinction event (~249.1 Ma). A precise chronology from the southern Nanpanjiang basin (China) allows for a quantification of these fluctuations of Earth climate. Following the volcanic pulse causing the PTBME, several discontinuous episodes of volcanism of the Siberian Large Igneous Province (S-LIP) were generally assumed to have caused the subsequent Early Triassic carbon cycle fluctuations. This is, however, in disagreement with the geochronological database of precise zircon U/Pb dates that put an end to the volcanic activity at 250.6 Ma (Burgess & Bowring, 2015; Augland et al., 2019). Therefore, recurrent S-LIP volcanism is an unlikely explanation for the Early Triassic unstable carbon cycle.</p><p>The initial intrusive pulse of the Karoo Large Igneous Province (K-LIP) formed the sill/dyke complex of the Karoo basin, South Africa. New, precise U/Pb geochronology confirms its very short duration at around 183.2-182.8 Ma (Burgess et al., 2015; Corfu et al., 2016), as well as its synchronicity with the lower Toarcian oceanic anoxic event (T-OAE), and a carbon cycle disturbance of presumable global importance. Repeated excursions in d<sup>13</sup>C<sub>org</sub> of up to 3 ‰ in the late Pliensbachian (~185.5 Ma) as well as at the Pliensbachian-Toarcian boundary (~183.5 Ma) are therefore at least partly older than any known magmatic activity of the K-LIP (Lena et al., 2019). We therefore, again, must invoke non-volcanic drivers in order to explain the instability of the carbon cycle.</p><p>These two case histories demonstrate that in order to invoke causality and global importance to carbon cycle instability, as well as for the testing of its correlation with volcanic episodes, we need to rely on geochronology of both sedimentary and volcanic records at the 10<sup>4</sup> years level of precision.</p><p>References: Augland et al. (2019) Scientific Reports, 9:18723 ; Baresel et al. (2017) Solid Earth, 8, 361–378, 2017; Burgess & Bowring (2015) Science Advances, 1(7), e1500470–e1500470; Burgess et al. (2015) Earth and Planetary Science Letters, 415(C), 90–99; Corfu, F. et al. (2016) Earth and Planetary Science Letters, 434(C), 349–352; Lena et al. (2019) Scientific Reports, 9:18430.</p>


2019 ◽  
Vol 760 ◽  
pp. 229-251 ◽  
Author(s):  
Henrik H. Svensen ◽  
Dougal A. Jerram ◽  
Alexander G. Polozov ◽  
Sverre Planke ◽  
Clive R. Neal ◽  
...  

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stephen M. Jones ◽  
Murray Hoggett ◽  
Sarah E. Greene ◽  
Tom Dunkley Jones

AbstractLarge Igneous Provinces (LIPs) are associated with the largest climate perturbations in Earth’s history. The North Atlantic Igneous Province (NAIP) and Paleocene-Eocene Thermal Maximum (PETM) constitute an exemplar of this association. As yet we have no means to reconstruct the pacing of LIP greenhouse gas emissions for comparison with climate records at millennial resolution. Here, we calculate carbon-based greenhouse gas fluxes associated with the NAIP at sub-millennial resolution by linking measurements of the mantle convection process that generated NAIP magma with observations of the individual geological structures that controlled gas emissions in a Monte Carlo framework. These simulations predict peak emissions flux of 0.2–0.5 PgC yr–1 and show that the NAIP could have initiated PETM climate change. This is the first predictive model of carbon emissions flux from any proposed PETM carbon source that is directly constrained by observations of the geological structures that controlled the emissions.


2015 ◽  
Vol 27 (1) ◽  
pp. 95-139 ◽  
Author(s):  
Richard Spikings ◽  
Ryan Cochrane ◽  
Diego Villagomez ◽  
Roelant Van der Lelij ◽  
Cristian Vallejo ◽  
...  

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