A Second Gunman in the Death of the Dinosaurs
If you've already heard that dinosaurs are extinct - and the betting is that you have - you've probably also heard the reason: an asteroid smashed into Mexico's YucatA n Peninsula some 65 million years ago, blasting enough dust into the atmosphere to block the sunlight and dim the skies.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Sep 12, 2012
The effect of the Deccan traps eruptions has been known for some time. Interestingly they provide an independent assessment of the rapidity of the mass extinctions. The early basalt flows in the north of the traps have weathered red tops containing dinosaur bones & egg shards. The later basalts in the south have the same red top soil horizons and contain mammal bones. Somewhere in the middle of the pile will be a basalt flow topping a soil with a major Iridium spike; that flow may be a mite thicker than average due to the sismicity accompanying the impact and crustal relaxation as a result.
Note however that the dinos appeared after the end Permian mass extinction with a major heat spike and drop in atmospheric O2. The small ones in particular would have adapted to the excess heat CO2 and SO2 in the atmosphere resulting from the emplacement of each basalt sheet in roughly 1000 year intervals of time. Reason being that dino remains appear on the soils developed on top of the early basalt sheet, so flows did not even cause local extinctions (unless local dinos were surrounded by hot lava at time).
The net results of the Deccan basalts would have been a decline in large dinos and a proliferation of the small agile Triassic model type dinos. Also note that small mammals without the usual adaptations to low O2 concentrations also survived both end Permian and K-T extinction events.
Sad news for the Dinos is that K-T impact occurrd when the dinos were still too large to target small bugs eating detritus. Result is that Birds survived, but closely related Dinos did not.
Have a nice day: Ag
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