40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change.
Reliable geochronological results gathered so far (n = 76) have considerably constrained the timing of the emplacement of the Karoo large igneous province (LIP). Yet strikingly missing from this dating effortis the huge southern sill complex cropping out in the >0.6 x 10(6) km2 Main Karoo sedimen...
| Main Authors: | , , , , |
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| Format: | Journal Article |
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American Geophysical Union
2008
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| Online Access: | http://hdl.handle.net/20.500.11937/29478 |
| _version_ | 1848752814415675392 |
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| author | Jourdan, Fred Fraud, G. Bertrand, H. Watkeys, M. Renne, P. |
| author_facet | Jourdan, Fred Fraud, G. Bertrand, H. Watkeys, M. Renne, P. |
| author_sort | Jourdan, Fred |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Reliable geochronological results gathered so far (n = 76) have considerably constrained the timing of the emplacement of the Karoo large igneous province (LIP). Yet strikingly missing from this dating effortis the huge southern sill complex cropping out in the >0.6 x 10(6) km2 Main Karoo sedimentary basin. We present 16 new 40Ar/39Ar analyses carried out on fresh plagioclase and biotite separates from 15 sill samples collected along a N-S trend in the eastern part of the basin. The results show a large range of plateau and miniplateau ages (176.2 +- 1.3 to 183.8 +- 2.4 Ma), with most dates suggesting a -3 Ma (181-184 Ma) duration for the main sill events. The available age database allows correlation of the Karoo LIP emplacement with the Pliensbachian-Toarcian second-order biotic extinction, the global warming, and the Toarcian anoxic event (provided that adequate calibration between the 40K and 238U decay constant ismade). The mass extinction and the isotopic excursions recorded at the base of the Toarcian appear to be synchronous with both the increase of magma emission of the Karoo LIP and the emplacement of the sills.The CO2 and SO2 derived from both volcanic emissions as well as carbon-rich sedimentary layers intrudedby sills might be the main culprits of the Pliensbachian-Toarcian climate perturbations. We propose that the relatively low eruption rate of the Karoo LIP is one of the main reasons explaining why its impact on thebiosphere is relatively low contrary to, e.g., the CAMP (Triassic-Jurassic) and Siberia (Permo-Triassic) LIPs. |
| first_indexed | 2025-11-14T08:14:36Z |
| format | Journal Article |
| id | curtin-20.500.11937-29478 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:14:36Z |
| publishDate | 2008 |
| publisher | American Geophysical Union |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-294782019-02-19T04:27:29Z 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. Jourdan, Fred Fraud, G. Bertrand, H. Watkeys, M. Renne, P. Karoo Pliensbachian-Toarcian large igneous province 40Ar/39Ar ages sill complex climate change Reliable geochronological results gathered so far (n = 76) have considerably constrained the timing of the emplacement of the Karoo large igneous province (LIP). Yet strikingly missing from this dating effortis the huge southern sill complex cropping out in the >0.6 x 10(6) km2 Main Karoo sedimentary basin. We present 16 new 40Ar/39Ar analyses carried out on fresh plagioclase and biotite separates from 15 sill samples collected along a N-S trend in the eastern part of the basin. The results show a large range of plateau and miniplateau ages (176.2 +- 1.3 to 183.8 +- 2.4 Ma), with most dates suggesting a -3 Ma (181-184 Ma) duration for the main sill events. The available age database allows correlation of the Karoo LIP emplacement with the Pliensbachian-Toarcian second-order biotic extinction, the global warming, and the Toarcian anoxic event (provided that adequate calibration between the 40K and 238U decay constant ismade). The mass extinction and the isotopic excursions recorded at the base of the Toarcian appear to be synchronous with both the increase of magma emission of the Karoo LIP and the emplacement of the sills.The CO2 and SO2 derived from both volcanic emissions as well as carbon-rich sedimentary layers intrudedby sills might be the main culprits of the Pliensbachian-Toarcian climate perturbations. We propose that the relatively low eruption rate of the Karoo LIP is one of the main reasons explaining why its impact on thebiosphere is relatively low contrary to, e.g., the CAMP (Triassic-Jurassic) and Siberia (Permo-Triassic) LIPs. 2008 Journal Article http://hdl.handle.net/20.500.11937/29478 10.1029/2008GC001994 American Geophysical Union fulltext |
| spellingShingle | Karoo Pliensbachian-Toarcian large igneous province 40Ar/39Ar ages sill complex climate change Jourdan, Fred Fraud, G. Bertrand, H. Watkeys, M. Renne, P. 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title | 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title_full | 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title_fullStr | 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title_full_unstemmed | 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title_short | 40Ar/39Ar ages of the sill complex of the Karoo large igneous province: implications for the Pliensbachian-Toarcian climate change. |
| title_sort | 40ar/39ar ages of the sill complex of the karoo large igneous province: implications for the pliensbachian-toarcian climate change. |
| topic | Karoo Pliensbachian-Toarcian large igneous province 40Ar/39Ar ages sill complex climate change |
| url | http://hdl.handle.net/20.500.11937/29478 |