Pierre Shale Fossils

I have long been wanting to explore the area known as Bacculite Mesa near Pueblo, Colorado searching for various fossils in the Pierre Shale deposits.  This site is on private land but the land owner does allow clubs to visit on planned trips.  This year I was able to make the field trip with the Canyon City and Lake George clubs.  

The Western Interior Seaway had Colorado as the ocean floor around 70-80 million years ago.  This was before the mountains were formed and all over Colorado there are fossils contained in Pierre Shale deposits.  I have found pyrite and marcosite concretions in this general area coming out of the Pierre Shale.  This is a rare and premiere location for fossils from this era of our geologic history!

Spanish Peaks

Looking SW over Pueblo towards the Spanish Peaks from the Bacculite Mesa.

Dave and Pierre Shale formations

Thanks David for taking this picture of me and the Pierre Shale formations of Bacculite Mesa locality.

I carpooled with another fossil enthusiast David (thanks for the ride and company!) and we both had a great day and some amazing finds.  David suggested hitting the back side of the collecting area and we found some great fossils in that area; but limited bacculites which was mainly on a different face of the mesa.  

Collecting area we were in. Photo courtesy of David Gillard.

I found the bacculite fossils pretty much in every zone of these hills including on top, especially in the small ravines and in wash outs below the hills.  I dug in a couple of spots that had quite a few rocks and fossils in the area, but didn’t find anything in-situ.  

Bacculites

Various bacculites are common if you look through the alluvial slopes as they have weathered out of their host Pierre Shale and made their way down the hill.  These multicolored bacculites are 4-6 inches long.

Bacculite spine

This is a bacculite tail that can flex, it is interlocked like vertebrae.

Here is what bacculites looked like. Taken from http://www.bhigr.com/media/photos/rplca/bacculites_grand.jpg

I found a couple spots where there was calcite (?) crystals in the fossils, like you see in the clams from Florida or septarian nodules.  These were eroding out of harder rock and not the Pierre Shale, I’m assuming some kind of reef as the rock was full of imprints of fossil clams, shells and ammonites.

shell imprtint

Shell imprint in shale.

Nymphalucina occidentalis

Small clam Nymphalucina occidentalis

bacculite

Weathered bacculite with shale matrix attached.

Unknown concretion, love the red/yellow/orange staining and patterns!

Little conglomerate ball, about an inch.

I love this triangle shell in a partial cube!

Calcite cluster, about 3 inches.

Veins of calcite mineralization

bacculite head

I believe this is the head of a small bacculite–which you can see protruding from the left side.

 

More calcite (?) crystallization

 

Bacculite with some of the iridescent patterns

Fossil clam with calcite mineralization

crystals

Some of the larger calcite (or barite?) crystals. These were beautiful amber color and translucent and in some spots gemmy.  Up to an inch.

Prickly Pear Cactus were in bloom!

David found this bacculite head right away; preserved in matrix!

David’s ammonite fossil.

Cool color and design on this shale rock; about 4 inches.

Various clams and shells. Many have calcite cores.

Cinco de Mayo 2013: A New Hope

Today was a great day and my second outing for the year, this time to the New Hope Amethyst lode claim as guests of the Canyon City rock club.  I was with the Lake George Gem and Mineral club , there were 5 or 6 clubs on this field trip.  Lots of eager Rockhounds wanting to get out find some amethyst quartz crystals!!  The day was slightly overcast which was perfect for a day of digging–bright but not too hot or sunny. I started the day doing some prospecting and walking around the claim and surrounding public lands.  I found some epidote in quartz/granite which was cool; but nothing else per se.  Richard, the field trip leader for the club, had given me a clue on where to find some calcite crystals so I went on a hunt for them.  I was able to find the area he mentioned; but obviously someone had been digging there already and I didn’t see the calcite crystals he mentioned.  The seam that had been dug out had some dried red clay and I figured I should see what that was about so I started digging in that carefully.  I ended up finding a small plate of small quartz points which was exciting (thanks to Carl Carnein for his help with identification).  Unfortunately the host rock was extremely brittle and even exercising great care it was hard to extract the plates without everything busting into tiny pieces.

Cute calcite cluster found in the maroon clay

Cute quartz cluster found in the maroon clay.  These will scratch glass.

I continued to dig into the clay and uncovered more small plates of quartz crystals, again they were very brittle but I was able to extract a couple 1.5 – 2″ pieces intact which was exciting!  Continuing into the pocket I the clay turned iridescent maroon colored and that is where I found a couple of really pretty plates, one, the back/side of the pocket was able to be extracted intact that was rather large, 4-5″ long.  Sweet! The below cluster was one of the intact small clusters which came from this area of the small pocket.

Calcite cluster without the coating of calcite

Quartz cluster that was pretty clean…

Awesome large cluster of calcite crystals intact!!

Awesome large cluster of quartz crystals intact!!

Once I got to the end of this small pocket I broke into a small but pretty smokey and amethyst quartz vein.  It quickly pinched out and I decided to see what everyone else was finding and relax for a little bit. Overall the calcite pocket was about 3-5″ high, 1-3″ wide and about 4″ deep at the largest points.

"Zipper" Vein of Smokey and Amethyst Quartz at the end of the Calcite pocket

“Zipper” Vein of Smokey and Amethyst Quartz at the end of the quartz pocket

Everyone was having luck about two feet deep digging an amethyst vein.  There was a lot of folks digging in a tight space so I decided to try and intercept the vein a little ways away from the crowd; 10 yards or so uphill.  I dug and dug in all directions but did not find the vein…it either made a significant turn, went further down than I was wanting to dig (which was 3+ feet!); or pinched out.  After a couple of hours I reclaimed my prospecting and just hung out and listened to everyone talk and enjoyed the stories and watching everyone find great little clusters.

Small amethyst, milky and smokey quartz clusters and points

Small amethyst, milky and smokey quartz clusters and points

I went through some of the tailings and found some cool little points, and after everyone was done they offered me a chance to dig in the excavated hole and I enjoyed about an hour of finding great small milky quartz covered plates before it was time to head home.  It was a wonderful day with great people; I’ve really enjoyed visiting this claim and appreciate the opportunity to do so!

Needs a little more scrubbing; beautiful amethyst quartz!

Needs a little more scrubbing; beautiful amethyst and smokey quartz!

Calcite crystals in close proximity to quartz vein

Quartz crystals in close proximity to quartz vein