Earth Science Stories

4 Feb 2010

Science Daily, January 21st ... the Kimmeridge Clay deposit is a well known geological formation that runs across middle England - only surfacing at a few points that have been worn down by glaciation but underlying a great swathe of later geological formations. It was deposited in the Late Jurassic between 160 and 145 million years ago and is the main oil source rock in the North Sea. Within the Kimmeridge Clay (which can be seen on Dorset's Jurassic coast and in various quarries) there are divisions, one of which contains many fossils and the other which has none. The hypothesis is that the clay was laid down during a shallow sea environ, the organic matter preserved in oxygen depleted bottom waters. However, the clean Kimmeridge clays are organically poor which indicates, to geologists, that the deposits changed from oxygen depleted to oxygen rich, possibly on more than one occasion - a theory brought about, quite naturally, from the idea geological deposits are formed over long periods of time. The research was therefore based on the conventional model but it could be interpreted differently from the point of view of rapid deposition - containing both clay (with fossils) and clay (without).

University of Arizona News ( ) ... Ice Age climate from an Arizona stalagmite shows that abrupt climate change that is known from Greenland ice cores (Heinrich and Dansgaard-Oeschger events) also occurred in the SW of North America. The stalagmite revealed a century by century climate record between 55,000 and 11,000 years ago. When the ice sheets covered NE North America the climate in the SW was cooler and wetter than now and the stalagmite showed that the climate switched repeatedly between cool and wet and drier conditions. June 2008 ... this is an old story but interesting. A dinosaur bone was discovered in Australia that has 'defied prevailing wisdom'. I like it when a piece begins with the anomalous bit straight out in the open. Apparently, the bone belongs to a very close relative of the Megaraptor, a dinosaur with hawk like habits which inhabited South America some 90 million years ago. This suggests Gondwana Land, the super continent of the southern hemisphere, that is thought to have split apart during the Cretaceous to form four parts = South America, Africa, Antarctica and Australia, may not have happened quite the way it is generally assumed. Basically, it has been thought Australia has remained detached from Gondwana for at least 80 million years. This particular dinosaur bone appears to scotch that idea, and Australia and South America may still have been connected - possibly via Antartica, for much longer. The author of the piece actually says that land bridges of some kind must have existed until at least the late Eocine period, only 40 million years ago ( published in The Proceedings of the Royal Society B ).