The Dragon Wagon

The Dragon Wagon
The landscaping changes often.

Monday, August 29, 2016

The Mammoth Site

The geology around the Black Hills of South Dakota contains quite a bit of limestone.  Under the right conditions, groundwater dissolves away underground limestone and caverns may develop.  Approximately 26,000 years ago, the roof of a cavern near present day Hot Springs, South Dakota, collapsed, creating a sinkhole.  This sinkhole was about 120x150 feet at the surface and 65 feet deep, with steep walls.  An artesian spring at the bottom filled the sink hole with warm water.  The warm water allowed vegetation to grow at the edge of the water year round.  Over the next few hundred years, an occasional animal would try to reach the vegetation or water, fall in, die and be buried, as silt washing in slowly filled the sink hole.  Eventually, the sink hole was completely filled with sediment and buried skeletons, and the danger of entrapment was gone.  Over the next several thousand years, the softer surrounding geology was eroded away, leaving a small hill that was the sediment that had filled the sink hole.  In modern times, the community of Hot Springs, South Dakota, grew in the area.

In 1974, a landowner began earth moving operations to remove this small "hill".  Luckily, the bulldozer operator stopped when he encountered what appeared to be large bones.  Dr. Larry Agenbroad was brought in, started a paleontological dig, and soon realized the wealth and importance of the site.  This site contains the largest collection of mammoth remains in the world.  A non-profit corporation named "The Mammoth Site" was formed to own and manage the location.  To date, most of the bones have been left "in situ" where they have been carefully exposed in the site.  To date, 61 mammoth skeletons have been uncovered:  58 Columbian Mammoths and 3 Wooly Mammoths.  It is believed that all of the mammoths have been males, most of them young males.  A number of other important animal and plant fossils have also been found in the site.  This location continues to be an active paleontological dig with much yet to be uncovered.


A couple of fiberglass cast replicas in the lobby/gift shop




The dig site





The tools of the trade used for uncovering fossils



The red Spearfish Sandstone formed the rim of the sinkhole, so this image shows one edge of the sinkhole.



Out tour guide mentioned that the grinding surface of mammoth molars looked like the bottoms of sneakers.  Since we heard that, now when we see mammoth teeth, we always imagine some poor kid buried face down in the rocks!



Another of the animals found was the extinct Short-faced Bear.  This is a cast replica in their exhibit hall.


Sunday, August 28, 2016

Custer State Park

Custer State Park in the Black Hills of South Dakota is known for its observable wildlife.  We have taken several drives through the park, exploring most of its back roads.


Typical scenery of Custer State Park.



One of the primary attractions are the bison that roam Custer State Park.








When the bison decide to use the road,
a "bison jam" may occur.





We also saw several Pronghorns.







The park also has many Prairie Dog "towns".






Bluebird



Eastern Kingbird



Meadowlark



American Kestrel



Various flowers






Seed pod


Black Hills Institute of Geological Research

What does an "Older Fossil" (my username on many Internet forums) do when spending several days near Hill City, South Dakota?  Why he goes to view other fossils of course!  I had been reading about the Black Hills Institute of Geological Research for many years.  The BHIGR is a private company that specializes in the collection and preparation of fossils.   Since they are located in Hill City, just a couple of miles from where we have been camping, this was definitely on my list.




Their museum has a pretty extensive collection, which unfortunately is displayed in a fairly small space, so things look a little crowded.  Most of the displayed skeletons on the main floor are fiberglass casts of specimens held by other institutions.




They had a nice display of one of my favorite fossils, ammonites.  Ammonites were early cephalopods, ancient relatives of today's Nautilus.




I've always liked the complex suture patterns found in the later species of ammonites.  The suture pattern is formed where the walls that separate the chambers inside the shell contact the outer shell.  In ammonites, these walls became extremely intricately folded.



Sometimes the beautiful nacra (mother-of-pearl) of the original shell is preserved.



A nice collection of fossil fish and others from the famous Green River Formation



It is amazing how little the Horseshoe Crab and Stingray have changed over geologic time.




Crinoids (fossils of sea bottom dwelling plant-like animals)



This is one of the wonderful feathered dinosaur specimens from China which are confirming the dinosaur origin of birds.  Note the long tail feathers.



The BHIGR has long been involved in the study of tyrannosaurids, especially the famous Tyrannosaurus Rex.







Triceratops skull



The curious skull of a Titanothere (an ancient relative of today's rhinos)
 


Cast of a Coelophysis specimen found at Ghost Ranch in New Mexico
(where we visited earlier this year)



One of the flying reptiles, a pteranodon



Beautifully articulated Struthiomimus specimen



We thought that this Oviraptorosaur skull almost looked
like a scrap-metal, steam-punk sculpture!



Dracorex hogwartsia
This dinosaur "dragon" was a vegetarian!