Geology and geochronology of the Tana Basin, Ethiopia : LIP volcanism, super eruptions and Eocene-Oligocene environmental change
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New geological and geochronological data define four episodes of volcanism for the Lake Tana region in the northern Ethiopian portion of the Afro–Arabian Large Igneous Province (LIP): pre-31 Ma flood basalt that yielded a single 40Ar/39Ar age of 34.05±0.54/0.56 Ma34.05±0.54/0.56 Ma; thick and extensive felsic ignimbrites and rhyolites (minimum volume of 2–3×103 km32–3×103 km3) erupted between 31.108±0.020/0.041 Ma31.108±0.020/0.041 Ma and 30.844±0.027/0.046 Ma30.844±0.027/0.046 Ma (U–Pb CA-ID-TIMS zircon ages); mafic volcanism bracketed by 40Ar/39Ar ages of 28.90±0.12/0.14 Ma28.90±0.12/0.14 Ma and 23.75±0.02/0.04 Ma23.75±0.02/0.04 Ma; and localised scoraceous basalt with an 40Ar/39Ar age of 0.033±0.005/0.005 Ma0.033±0.005/0.005 Ma. The felsic volcanism was the product of super eruptions that created a 60–80 km diameter caldera marked by km-scale caldera-collapse fault blocks and a steep-sided basin filled with a minimum of 180 m of sediment and the present-day Lake Tana. These new data enable mapping, with a finer resolution than previously possible, Afro–Arabian LIP volcanism onto the timeline of the Eocene–Oligocene transition and show that neither the mafic nor silicic volcanism coincides directly with perturbations in the geochemical records that span that transition. Our results reinforce the view that it is not the development of a LIP alone but its rate of effusion that contributes to inducing global-scale environmental change.
Prave , T , Bates , C R , Donaldson , C H , Toland , H , Condon , D J , Mark , D & Raub , T D 2016 , ' Geology and geochronology of the Tana Basin, Ethiopia : LIP volcanism, super eruptions and Eocene-Oligocene environmental change ' Earth and Planetary Science Letters , vol 443 . DOI: 10.1016/j.epsl.2016.03.009
Earth and Planetary Science Letters
Copyright © 2016 Elsevier B.V. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at http://10.1016/j.epsl.2016.03.009
This work was supported by NERC Grants NE/D012996/1 and NER/B/S/2002/00540 and NIGFSC IP/1024/0508.
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