HOW FOSSIL LEAVES ARE RECOVERED



Excavating a fossil rainforest is very rewarding experience!  As discussed in "The Making of a Fossil Rainforest", thereís layer upon layer of mudstone and sandstone containing thousands of fossils.  Once the layers are discovered, it is easy to recover 500 or more fossil leaves in a single day. 

As we split the layers of rock, itís like opening a book and turning the pages of earthís ancient past.  The rock layers have naturally formed cracks or laminations which occur along the planes containing the fossil leaves.  Itís fairly easy for even an amateur paleontologist to see the cracks.  With a well-aimed swing of a rock hammer, the cracks easily open up to reveal their treasures.

Because the cracks form along the same plane as the leaves, they are almost always horizontal.  This makes sense because the leaves of the rainforest fall and lie horizontally.  We slowly work down through the layers of rock along these cracks.  Each piece is removed and carefully lifted up. 

Usually there is a main part of the fossil leaf on one side of the crack and a counterpart on the other side. Depending on the leaf specimen and preservation, the fossil part containing the most valuable scientific information may be the top side of the leaf or the underside.  Or, it was very well preserved, as shown in the example at left; both sides will contain dramatic detail of veins, cuticle and stem.  At the excavation site, a decision is made on which part to keep or if both parts will be kept for study.


It's like opening the pages of a 
book on earth's history!

Most of the recovery effort at Castle Rock is being done using the "census method".  Even if a fossil leaf doesnít merit being taken back to the museum, it is identified and counted.  After a while, well-recognized plant species will only be counted and discarded unless they are extremely well preserved or if they may contain valuable scientific information.  We may uncover thousands of fossil leaves in a single day and storage space is finite in any museum.  So, we sift through all the fossils found and keep the best specimens (see note 1, below).  These are carefully wrapped and transported back to the museum for study.  However, the mudstone and sandstone at Castle Rock are very moist and require a special drying to prevent cracking.  For more on this, please see "Fossil Drying Process".
 

Notes

1. Back at the museum, another decision must be made.  After studying each specimen and recording its scientific information, we must decide if it is still valuable enough to keep in a permanent collections area for future study which may be conducted by museum staff or other researchers around the world.

Paleocurrents.com
[Created 09/18/2002]
[Last Updated: n/a]