Sunday, May 03, 2015

Geosonet 28

The Mesozoic ended with a splat
But what about a vastly older time?
Archean life was breathing algal mat
Did asteroids destroy them in their prime?
The spherule layer in the Kuruman
Contains iridium, enriched by mass.
Though seared in orogenic frying pan
Stilpnomelane was once an impact glass.
The Pilbara, a continent away
Contains the same meteoritic trace
The world rained fire on that fateful day,
A hail of red-hot glass from outer space.
   Yet, younger sediments are undisturbed
   The hydrologic cycle’s unperturbed.

Previous geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28


Chris Phoenix said...

Wouldn't algal mats have been protected by water? I think I remember that in the Mesozoic fire-rain, things that lived underground tended to survive.

I'm not doubting the geochemical data or its interpretation - just the attribution of algal extinction to it.

Unless the algal mats were purely tidal, or the fire-rain had enough energy to heat the water to a depth of many feet?

Chuck Magee said...

The End Mesozoic extinction was pretty severe for marine life. Ammonites, All the big marine reptiles except turtles, and a variety of microfossils all got hit.