Flood Basalts and Stratigraphic Boundaries

Flood Basalts and Stratigraphic Boundaries

The great continental flood-basalt lava flows exceeded 2000 cubic kilometres and comprise one form of large igneous province (LIP map). [image Columbia River Basalt Flows] Large igneous provinces are believed to have been caused by mantle plumes in the lithosphere, which injected magma into the lithosphere and erupted as huge basalt lava flows, probably within a million years or less.

The Deccan, Newark, and Siberian flood basalts (each with lava volumes greater than 2 x 10^6 km^3 over periods of 1 million years or less) have been correlated with major extinction events. Extinctions could have been caused by environmental impacts of released gases – climatic cooling due to sulphuric acid aerosols, greenhouse warming caused by CO2 and SO2 gases, and acid rain. Mantle plume activity and flood basalts may also have been associated with other deleterious global geological factors, such as changes in sea-floor spreading rates, rifting events, increased tectonism and volcanism, or sea-level variations.

The end-Cretaceous (Cretaceous/Tertiary or K/T boundary) mass extinction that wiped out the dinosaurs has been correlated with the impact of a 10-km diameter asteroid about 65 million years ago. Several other extinction events correlate with evidence of similar impacts.

Flood Basalt

Age Ma

Stratigraphic Boundary

Age Ma

Columbia River 0.25 x 10^6 km^3

16 ± 1 duration ~ 1 Myr Early/Mid-Miocene [image] 16.4
Ethiopia ~1 x 10^6 km^3 31 ± 1 duration ~ 1 Myr Early/Late Oligocene 30

North Atlantic >1 x 10^6 km^3

57 ± 1 duration ~ 1 Myr Paleocene/Eocene(Thanetian/Selandian) 54.8 (57.9)
Deccan >2 x 10^6 km^366 ± 1 duration ~ 1 MyrCretaceous/Tertiary [image]65.0 ± 0.1
Madagascar ? volume 88 ± 1 duration ~ 6? Myr Cenomanian/Turonian(Turonian/Coniacian)

93.5 ± 0.2 (89 ± 0.5)

Rajmahal ? volume 116 ± 1 duration ~ 2 Myr Aptian/Albian 112.2 ± 1.1
Serra Geral/Etendeka >1 x 10^6 km^3 132 ± 1 duration ~ 1 or 5 Myr Jurassic/Cretaceous(Hauterivian/Valanginian) [image 1] 142 ± 2.6 (132 ± 1.9)
Antarctica >0.5 x 10^6 km^3 176 ± 1 or 183 ± 1 duration ~ 1? Myr (Aalenian/Bajocian) (176.5 ± 4)
Karoo > 2 x 10^6 km^3 td> 183 ± 1 duration ~ 0.5 -1 Myr Early/Middle Jurassic [image 1, image 2] 180.1 ± 4
Newark >2? x 10^6 km^3201 ± 1 duration ~ 0.6 MyrTriassic/Jurassic [images]205.7 ± 4
Siberian > 2 x 10^6 km^3249 ± 1 duration ~ 1 MyrPermian/Triassic [image, image 2]248.2 ± 4.8

adapted from here.

Other flood basalts Paraña,

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