Blue-Gray Limestone, Crinoids, and Large Quartz Crystals in Western Arkansas

     Yes, this is Maizie and me licking our lips (or nose, in her case) at the striking roadcuts of the Ozark Mountains (actually plateaus) of northern Arkansas and the Ouachita Mountains of west-central Arkansas.

       The western part of Arkansas includes, from north to south: the Ozark Plateaus or Mountains, the Arkansas River Valley, the Ouachita Mountains, and the West Gulf Coastal Plain. The Ouachita Mountains are one of the few east-west-trending ranges in the U.S. (The Uinta Mountains in Utah and Mt. Tom/Mt. Holyoke Range in Massachusetts are two of the other east-west-trending features.)

      The geologic units are outlined below, including shades of blue for blue-gray Mississippian rocks. (NB: unless one is a geomorphologist, most geologists just gloss over anything coloured yellow for the Tertiary and Quaternary.)

       The Mississippian Pitkin Limestone is 360 to 320 years old and is chucky-jam full of fossils, including crinoids and bryozoans. The crinoid stems (which resemble rolls of Smarties candies) are parts of animals called sea-lilies that attached to the seafloor. In this rock sample, which may or may not have travelled from northern Arkansas to Colorado, shows the unweathered fossils.

        Here are some weathered out crinoid stems.

        And here is the stem and the less-often preserved top of a crinoid animal.

       The photo below shows weathered-out screw-shaped bryzoans, commonly referred to as Archimedes screws (in the right bottom part of the photo.) The upper left part of the photo shows the crinoid stem pieces. The crinoids are so plentiful in the Pitkin Limestone that some people apparently fling them on the ground like pop-rocks. We did not partake of that practice.

      The Pitkin Limestone overlies the Fayetteville Shale as seen in this roadcut. The "tight" shale is the source of much gas development in Arkansas via hydraulic fracking.

      One of the most spectacular parts of our Natural State of Arkansas journey was traveling south along state route 7 from Russellville to Ouachita Hot Springs National Park, right through the heart of the Ouachitas.

         Here's the view (with Maizie) toward the Arkansas Valley:

        Ouachita Hot Springs National Park:

       Pictured below are some large quartz crystals from Blue Springs, Arkansas, which are now at the Crystal Bridges American Art Museum grounds in Bentonville.

       . . .And a few images incorporating geology and art from Crystal Bridges:

      And lastly, a beautiful morning with cool mist in the Ozarks somewhere between Mountain Home and Eureka Springs:

Have you explored Arkansas? Hoping you had/have a traveling companion and navigator as amazing as Maizie. . .

Steph

Crinoids for Cri-nerds

     We discussed crinoids,

also known as sea "lilies," here at Partial Ellipsis of the Sun in April. This extraordinarily well-preserved Paleozoic crinoid fossil sample (below) inspired another look at this animal that looks like a plant.

      Compare the sample above to the "Smarties" stem pieces we found in northern Arkansas in April. The disarticulated crinoid stems or stalks are relatively common, but the delicate, lacy crown pieces are much rarer.

      Modern day crinoids and the fossil animals are quite similar, hence they are often referred to by the non-scientific term "living fossils."

       The parts of crinoid animals are labelled below, though the terms are quite plant-based:

I guess you could say I'm a bit of a cri-nerd ;-).

     How about you?
     Steph

April Arkansas Gems, Fossils, and Meanderings

       A post about Arkansas gems, fossils, and rocks is overdue. This crinoid piece is especially well-preserved. Here is a bit more information about crinoids.

     We spent many hours sorting and breaking apart Mississippian and Ordovician rocks. What joy!

Quartz crystals: 

Crinoid stalk or stem pieces:

     This sample was not available to bring home :-(.

But, this brachiopod sample  was: 

       My Mom, Smith College friend, Karen, and I had a great time exploring northwest Arkansas.We found brachiopods, crinoids, quartz crystals, and explored Crystal Bridges Art Museum, Thorncrown Chapel, the Ozark Folk Center and Blanchard Springs Caverns located in Fifty-Six, AR. Little Rock Central High School was the last stop before dropping Karen at her aunt's home in Hot Springs and heading back to Bentonville.

     We almost missed the road to Thorncrown Chapel, even though we were expressly looking for it. It was worth the trek!

        The outdoor artwork and plantings are some of my favorite parts of Crystal Bridges.

     Pappy and Lightning entertained us at the Ozark State Park Folklore Center.
   

     More highlights:

      Mom and Maizie were big fans of the Frank Lloyd Wright home:

      We enjoyed the geodesic dome:

       Alas! I left my iPad atop my trusty Subaru at one of the last overlooks on the way from Hot Springs to Bentonville. I saw it fly off in the rear view mirror. The photos were not in the cloud. So, a few photos from my friend and from my phone remain. It was most memorable and mom can now answer the question “Why are you going to Arkansas?” with some of these images. 

      Mom liked the half-mile trek through Blanchard Springs Caverns in Fifty-Six, especially.

        And we all really liked the giant bronze spider, Maman, holding her marble eggs protectively over the main entryway at Crystal Bridges.

        [I am writing this on my phone without a 'u' key so the photos will do most of the talking this time around.]


        Hope you'll have a chance to make Arkansas plans some time. It is The Natural State and it is a Gem!

Steph