Friday, March 23, 2012

Treasures of all ages

Last Sunday the Bendigo Family Nature Club organised a fossil hunt in the bush at the back of Spring Gully. Lots of people turned up with their little kids and we had a great morning finding creatures from the distant past.

The fossils we found were from the geological period known as the Ordovician. This covers the time period from about 440-500 million year before the present. In Ordovician times eastern Australia was at the bottom of a very deep sea. Not much lived down there. For the most part thefossils we find are things that floated around on the sea surface and fell to the bottom after dying. 

The most common fossils (by far) are graptolites. These little guys were colonial organisms that had their own little flotation device. A small balloon like structure allowed them to float whilst the rest of the organism (the fossilised bit) dangled down in the water.

Each of the little parts that look like the teeth of a saw was the home for a tiny animal known as a zoid or polyp.   Graptolites were around and very prevalent from about 500 million years ago. (Cambrian Period) through to about 400 million years ago (Devonian Period). During these time they progressed down an amazing evolutionary path and, accordingly, they are very good marker fossils that allow for subdivision of periods such as the Ordovician. This is why and how the Ordovician rocks are shown on the Bendigo geological maps as comprising a number of different sub-stages.
Anyway, the kids (and the adults) had a fantastic time last Sunday. They turned over some rocks and broke open others and they all found fossils.

Marbled Gecko (Christinus marmoratus) - the soft-scaled one with faint, grey, blotchy markings.

No comments:

Post a Comment