The Central Atlantic Magmatic Province and its Connection with the Triassic/Jurassic Extinction

The Central Atlantic magmatic province (CAMP) is a large igneous province formed during the breakup of Pangaea during the Mesozoic era. Rifting of North America from Europe and Africa (i.e., the open of the present day Atlantic Ocean) occurred during the Latest Triassic and or/ Earliest Jurassic and resulted in the emplacement of at least 10 million square kilometers of basalt in eastern North America, South America, Northern Africa, and Europe, the largest known igneous province in area of extent.




The CAMP is of significance because of its possible relationship with the Triassic/Jurassic boundary and thus a contributor to the Triassic/Jurassic extinction event. However, the exact timing of the event and whether or not it was a factor in extinction is highly debated with one group of workers arguing for it as a cause and another group denying this. Interestingly, support for or against the CAMP being a cause for the TR/J extinction depends on where the rocks are studied and dated. In Morocco the age of lava flows appears to coincide with the TR/J boundary (e.g., Marzoli et al., 2004, 2008; Verati et al., 2007), whereas in North America the flows appear to be too young (e.g., Whiteside et al, 2007, 2008).

A recent paper by Jourdan et al. (2009) provides new dates of CAMP deposits from North America and again argues for a causal effect on the end Triassic extinction (see the full abstract below), thus this issue is far from resolved.

You can read more on the CAMP at these websites:

http://en.wikipedia.org/wiki/Central_Atlantic_Magmatic_Province

http://www.auburn.edu/academic/science_math/res_area/geology/camp/

Jourdan, F., Marzoli A., Bertrand, H., S. Cirilli, S., Tanner, L.H., Kontak, D.J.,
McHone, G, Renne, P.R., and G. Bellieni. 2009. 40Ar/39Ar ages of CAMP in North America: Implications for the Triassic–Jurassic boundary and the 40K decay constant bias. Lithos 110:167-180. doi:10.1016/j.lithos.2008.12.011

ABSTRACT - The Central Atlantic magmatic province (CAMP) is one of the largest igneous provinces on Earth (greater than 10 million square km), spanning four continents. Recent high-precision 40Ar/39Ar dating of mineral separates has provided important constraints on the age, duration, and geodynamic history of CAMP. Yet the North American CAMP is strikingly under-represented in this dating effort.

Here we present 13 new statistically robust plateau, mini-plateau and isochron ages obtained on plagioclase and sericite separates from lava flows from the Fundy (n=10; Nova Scotia, Canada), Hartford and Deerfield (n=3; U.S.A.) basins. Ages mostly range from 198.6±1.1 to 201.0±1.4 Ma (2σ), with 1 date substantially younger at 190.6±1.0 Ma. Careful statistical regression shows that ages from the upper (199.7.0±1.5 Ma) and bottom (200.1±0.9 Ma) units of the lava pile in the Fundy basin are statistically indistinguishable, confirming a short duration of emplacement (≪1.6 Ma; ≤1 Ma). Three ages obtained on the Hartford (198.6±2.0 Ma and 199.8±1.1 Ma) and Deerfield (199.3±1.2 Ma) basins were measured on sericite from the upper lava flow units. We interpret these dates as reflecting syn-emplacement hydrothermal activity within these units. Collectively, CAMP ages gathered so far suggest a short duration of the main magmatic activity (2–3 Ma), but also suggest the possibility of a temporal migration of the active magmatic centers from north to south. Such a migration challenges a plume model that would postulate a radial outward migration of the magmatism and is more compatible with other models, such as the supercontinent global warming hypothesis. When compared to the age of the Triassic–Jurassic boundary, the filtered CAMP age database suggests that the onset of the magmatic activity precedes the limit by at least few hundred thousand years, thereby suggesting a causal relationship between CAMP and the end of Triassic mass extinction.

An age at 191 Ma possibly suggests a minor CAMP late tailing activity (190–194 Ma) which has been observed already for dykes and sills in Africa and Brazil. We speculate that, if genuine, this late activity can be due to a major extensional event, possibly heralding the oceanization process at ~190 Ma. Comparison between high quality U/Pb and 40Ar/39Ar ages of pegmatite lenses from the North Mountain basalts confirms a ~1% bias between the two chronometers. This discrepancy is likely attributed to the miscalibration of the 40K decay constants, in particular the electron capture branch.

REFERENCES

Marzoli, A., Bertrand, H., Knight, K.B., Cirilli, S., Buratti, N., Vérati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., and G. Bellieni. 2004. Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis. Geology 32:973–976. doi: 10.1130/G20652.1

Marzoli, A., Bertrand, H., Knight, K., Cirilli, S., Nomade, S., Renne, P.R., Verati, C., Youbi, N., Martini, R., and G. Bellieni. 2008. Synchrony between the Central Atlantic magmatic province and the Triassic–Jurassic mass-extinction event? Comment. Palaeogeography, Palaeoclimatology, Palaeoecology 262, 189–193. doi:10.1016/j.palaeo.2008.01.016

Verati, C., Rapaille, C., Féraud, G., Marzoli, A., Bertrand, H., and N. Youbi. 2007. Timing the Tr–J boundary: further constraints on duration and age of the CAMP volcanism recorded in Morocco and Portugal. Palaeogeography Palaeoclimatology Palaeoecology 246. doi:10.1016/j.palaeo.2006.06.033

Whiteside, J.H., Olsen, P.E., Kent, D.V., Fowell, S.J., and M. Et-Touhami. 2007. Synchrony between the Central Atlantic magmatic province and the Triassic-Jurassic mass-extinction event? Palaeogeography, Palaeoclimatology, Palaeoecology 244:345-367. doi:10.1016/j.palaeo.2006.06.035

Whiteside, J.H., Olsen, P.E., Kent, D.V., Fowell, S.J., and M. Et-Touhami. 2008. Synchrony between the Central Atlantic magmatic province and the Triassic–Jurassic mass-extinction event? Reply to Marzoli et al. Palaeogeography,Palaeoclimatology, Palaeoecology 262, 194–198. doi:10.1016/j.palaeo.2008.02.010

Graphic is from here.