#drrock

Ripples from ~ 2-bilion-years ago

Soft rocks under pressure

This rock was once a soft sediment laid down layer upon layer at the bottom of a sea. But when got caught up among tectonic forces, the rock was compressed and squeezed into contorted shapes as shown in this outcrop.

Compounded time in nature

One of my favourite geological features are rocks within rocks like the one in the picture. For me they beautifully encapsulate passage of time at scale that is not comprehensible by human beings.

This boulder is at least 200 million years old and yet it contains other rocks that must have formed before it. So, the cumulative time encapsulated by this simple boulder is much greater than what already is vast antiquity.

Hi! Actually, not until now. I do not have a ‘hated rock’, as in every rock an interesting story can be found. But if I had to pick one, I think it would be a marble.

Marble is a metamorphic rock which originally was a limestone (a sedimentary rock made up of fossils of ancient sea creatures) that was transformed/recrystallised by intense heat and pressure. Because of this metamorphic transformation, fossils in limestone rock are often destroyed and much of the rock’s earlier history is erased. But of course, that’s not to say that there is nothing that can be done with it!

Frog Rock

The frog rock is a granite boulder which was fractured and weathered by natural processes that made it develop a shape that resembles a crouching frog. This is an example of pareidolia, which is a human tendency of seeing shapes of animals, human faces etc. in inanimate objects.

Many shades of fossils

Fossils are incredible remnants of an ancient world. They can be billions, millions, thousands etc. years old and their antiquity has always intrigued humankind.

Sometimes fossils can be very easily spotted in rocks because their telling shape stands out in a rock, but sometimes it may not be so easy and one has to know what to look out for.

In this post I present an array of marine shell fossils in sandstones and siltstones that represent shallow to deep sea environments from around 250 million years ago. I hope these can help you learn what to look out for and so you too can spot fossils in your local rocks.

Many shapes of fossils (Part 2)

Marine sedimentary rocks are the most common along southern New South Wales coast of Australia. These contain many marine shell fossils in sandstones and siltstones that represent a shallow to deep sea environments from around 250 million years ago.

These creatures would have fed on the organic-rich debris found within the sediment that now surrounds them, and which after many millions of years have turned into a hard rock.