Leaf Fossil Hunt

To a rockhound a cut bank rising from a road’s borrow pit draws attention. You might see a wall of stone, a tumble of gravel, or you may not even notice.

Rock pickers see these as a window to  the past. The road builder has conveniently opened a portal into local geology. 

An important aspect of finding fossils and unearthing minerals is understanding time from a  geological prospective.

Sedimentary, igneous, and metamorphic are the three major rock groups. Knowing which type you’re looking at helps one understand what could possibly get chipped out.

Understanding how the earth was formed is knowing a measure of geological time  .  .  .  literally millions of years.

This week’s trek took us to a road cut on the crest of the Ochoco divide. There we split apart sedimentary rock layers in search of leaf and twig fossils. 

On the geological time line these layers are young, less than fifty million years old and likely encased in mud and sediment on an ancient lake bed.

Volcanic activity pushed these rocks up to form mountains, only to be exposed by a dozer cutting out a logging road.

Leaf fossils are one of the few types we’re allowed to collect  .  .  .  dig up some bones and authorities want to know about that. 

But plant material is fair game.  However, it’s not easy work. It’s a fragile dig. You need to carefully split layers of rock to reveal the fossil.

Most plant fossils are from impression fossilization. Layers of sediment and soil bury the plant material leaving an impression or copy showing  a leaf in rather fine detail.

However, there are  times when the plant material gets replaced with minerals and you get a cast fossil.

Often casts are with limbs or twigs and the mineral replacing the plant structure so that rather than a simple ‘image’ you have a physical copy  .  .  .  in rock.

We picked through tailings and chipped away at rock faces long enough to get some representative examples.

There was no need to fill buckets with rock bound fossils. The goal is to explore some different places  .  .  .  well, and have a picnic in the wilds.