Truckin, up to buffalo. Been thinking, you got to mellow slow.
Takes time, you pick a place to go, and just keep truckin on.
The Blog submissions during the last couple of months have been sparse as I have been truckin on like the do-dah man. Destinations have included fishing in northwestern Ontario, exploring the back roads of Wisconsin, hiking and leaf peeping near Twin Lakes south of Leadville, Colorado, and zipping all over the Black Hills and Plains of South Dakota. Geology is a fascinating science and I have never regretted choosing such a college major.
|Marchington Lake, Ontario: walleye for breakfast.|
For readers who have traveled east-west across South Dakota (one of my favorite states), the changes in landscape are quite easy to observe. Most of the landscape East River (east of the bisecting Missouri River---see Blog 1/29/14) is covered by Pleistocene glacial debris; outcrops of bedrock are scarce and rich farm land supports fields of soy beans and corn. A limited number of streams exhibit rock outcrops but they are few and far between. As soon as travelers enter West River (if traveling I-90 the River is at Chamberlain) the tilled farm lands turn to short grass cattle pastures, rock exposures are numerous, and relief becomes more noticeable. Please observe the following figures (shaded relief and (geology) to better understand the relationship between geology and landscapes. In addition, readers should consult a “road map” for place locations and highways.
Shaded relief map of South Dakota. Map courtesy of Ray Sterner, John Hopkins University.
General geologic map of South Dakota. See 1/29/14 Blog for information East River. Map courtesy of South Dakota Geological Survey.
West River, South Dakota, belongs to the Great Plains Physiographic Province and a subdivision termed the Unglaciated Missouri Plateau. Whereas the landscape East River (Glaciated Missouri Plateau) was formed due to glacial action, features in West River are the result of action by streams (with a little help in a few places by igneous intrusions). It is most easy to think of West River geology as follows (refer to figures). The central part of the state (trending east-west) is dominated by a large hunk of the Cretaceous Pierre Shale, sometimes referred to as the Pierre Hills. Exposures often are poor except along the flanks of the Black Hills (BH) and adjacent to some of the streams like the White and Cheyenne Rivers—both draining the Black Hills region and flowing east before dumping into the Missouri River. Much of the surface of the land has been softened by erosion of the shale, wind-blown loess often mantles the surface, there are few nifty landforms, and grasslands dominate the region. Stratigraphic correlation of the Pierre Shale between the Missouri River Trench and the Black Hills remains quite difficult for geologists.
The southern swatch of land in West River is more of a butte and mesa and “badland” topography dominated by exposures of Cenozoic rocks. The famous badlands, including Badlands National Park, are included in these Tertiary Tablelands. Adjacent to the South Dakota-Nebraska state line are a couple of interesting geological features: 1) a small section of the Nebraska Sand Hills sneak northward into South Dakota in the central part; and 2) in the southwest there is a sharp break in the landscape at the Pine Ridge Escarpment (PRE) where Tertiary tablelands erode into a series of forested ridges and valleys and form the northern boundary of the High Plains subdivision of the Great Plains.
|Google Earth© map near Pine Ridge, SD. Note forested PRE trending southwest from Pine Ridge. The linear ridges of the “sand hills” are easily visible.|
Trending east-west across northern West River are the Cretaceous Tablelands dominated by exposures of latest Cretaceous to early Tertiary rocks. The Fox Hills Formation is essentially a regressive beach deposit (sand) left behind by the disappearing Western Interior Seaway. Above that unit are rocks deposited in marine-marginal swamps, marshes, alluvial plains, streams and floodplains—the Cretaceous Hell Creek (famous for fossils of the “last dinosaurs”), and the Paleocene Ludlow and Tongue River formations. Rocks above the Fox Hills are generally a “dull” color dominated by grays and blacks. However, these rocks contain massive beds of lignitic coal and have been mined for decades.
Directly east of the southern Black Hills, essentially south of I-90 and west of Murdo (Exit 192), is one of the most fascinating areas of the U.S. Collectively known as the “badlands”, this corner of the state has tremendous exposures of Tertiary rocks, especially those of Eocene, Oligocene, and Miocene ages. In addition, travelers also will notice Cretaceous outcrops along the stream valleys—usually the dark gray Pierre Shale and occasionally the overlying buff-colored Fox Hills Formation (mostly sandstone). The centerpiece of the “badlands” region is Badlands National Park (1978), established in 1929 as a National Monument to protect the vast paleontological resources in the Eocene-Oligocene White River Group.
I had a great experience in the summer of 1966 rummaging around the badlands (lower case and generic badlands) while collecting geological information. “Things” were just different 45 years ago and I was able to travel and collect extensively over the region—but not in the National Monument! Truckin on, 1966.
Truckin on, badlands1966.
Today, very few travelers heading east-west across South Dakota bother to explore this corner of the state other than taking a quick drive through the National Park loop. It is much too easy to set the cruise control at 75 mph and head down I-90. However, the “badlands” geology is fascinating and includes a number of large mesas locally known as tables and buttes. Two of the large highlands, Sheep Mountain Table (3143 feet) and Cuny Table (3196 feet), have public access to their summits. Others, such as Rattlesnake Butte, are managed by the Oglala Sioux out of Pine Ridge. In an another Blog (1/8/14) I wrote about the calcite sand crystals collected on Rattlesnake Butte. All of these mesas have a similar geological profile with the badly eroded White River Group exposed on the flanks and a protective cover of Miocene rocks (including some indurated volcanic ash) on top. In addition, many have summit blankets of Pliocene and/or Pleistocene stream gravels.
I usually visit the badlands each summer and consistently journey to the agate beds trying to locate a somewhat elusive Fairburn Agate. These agates are among the best known banded variety in the world. They are valued for their colorful fortification patterns with an abundance of reds (iron oxide), oranges (iron oxide) and blacks (manganese oxides). The derivation of their name comes from the small community of Fairburn, located south, ~25 miles, of Rapid City near SD 79. The Fairburn beds in this area seem to be lag and/or channel gravels associated with the Chadron Formation or the underlying Chamberlain Pass Formation. Although the “type locality” Fairburn beds have been prospected for decades, they still yield a few agates but especially unlimited numbers of chalcedony, jasper, and quartz. This year I was able to locate a small agate, nothing to brag about, but still a Fairburn. After a little polishing the fortification pattern begin to appear.
I also found about 50% of a silicified brachiopod, some sort of a Paleozoic Spirifer-type from one of the Mississippian or Pennsylvanian limestones.
|Small Fairburn Agate 2014. Maximum width ~2.1 cm.|
I also found about 50% of a silicified brachiopod, some sort of a Paleozoic Spirifer-type from one of the Mississippian or Pennsylvanian limestones.
During my excursions in 1966 I collected a number of pieces of a sky-blue chalcedony from the Brule Formation (stratigraphically above the Chadron Formation in the White Rive Group). This microcrystalline quartz occurs in thin veins or dikes (non-igneous) due to some sort of diagenetic processes. Since my ramblings in the mid-1960s the Park has expanded its boundaries and other land has become off-limits. In visiting with current collectors and rock shop owners it appears that this beautiful chalcedony is mostly unavailable to rockhounds.
|Spirifer brachiopod (convex right two-thirds) with a wide hinge line (top), a wing-like shape, with a deep sulcus and fold, and prominent plications. Most likely Mississippian or Pennsylvanian in age. Width ~2.4 cm.|
Chalcedony weathering from a vein in Badlands National Park. Photo courtesy of National Park Service.
Highway SD 44 in the “badlands” is a great road to help understand the local geology. Start at Cedar Pass in the National Park and travel west through the small community of Interior to the village of Scenic and observe the White River Group. If you are not in the National Park examine road cuts to find land snails of the genus Helix. This snail was one of the first fossils described from the “badlands” (Hayden, 1857). As the road (SD 44) descends down to the Cheyenne River, the Pierre Shale is exposed and a long time ago I was able to collect small limestone nodules with fossil crabs enclosed. In addition, I have a nice coral, probably Mississippian in age, collected from gravel pits along the river.
Helix leidyi (snails) from the White River Group.
The provenance of this rounded cobble of a Mississippian coral was in the Black Hills. The collecting locality was in a Pleistocene gravel pit east of the Hills.
A few miles past the river is the small community of Farmingdale with a paved road running north to New Underwood on I-90. To the south a gravel road leads to the Railroad Buttes collecting area on the National Grasslands. Again, collecting jasper, chalcedony and quartz is easy. But, I also have found Prairie Agates at this location. These agates seem to be “poor Fairburns” and are fairly common throughout western South Dakota and Nebraska. In fact, Prairie Agates are the “State Rock” of Nebraska.
The small community of Wasta is located at Exit 98 on I-90. In the mid-1960’s the highway was known as US 16 and I drove the two-lane road many times from Chamberlain (my work station) to areas around the badlands and Black Hills (my research area). I commonly stopped at Wasta to explore outcrops of the Pierre Shale and to hunt the concretions for golden barite and coiled cephalopods (see Blog 7/1/12). This area is quite famous for the fossils collected in the concretions but also well known for yielding treasures of golden barite. In fact, these barite localities were noted in the 2008 publication American Mineral Treasurers (published by the Mineralogical Record) as one of the top 50 American mineral specimen producing localities. Today, as I understand the situation, the private land is very difficult to access. If you plan on collecting I would suggest contacting the various rock and mineral clubs or rock stores located in the Black Hills. Prairie Agates. Right width 5.5 cm.
Photomicrograph of Golden Barite collected from Elk Creek, South Dakota. Length of crystal is ~1.7 cm.
In a Blog on 4/2/14 I wrote about collecting selenite roses in the Carlile Formation near the community of Provo (also called Igloo—see Blog for explanation of name). The area near Igloo also has substantial outcrops of the Upper Cretaceous Pierre Shale. As with many exposures of the Pierre, there are large concretions weathering from the shale in this part of Fall River, County. I have described the Golden Barite near Wasta to the north but near Igloo the concretions contain a rather nondescript, more massive, mostly colorless, barite. The pieces I collected decades ago are obviously part of a much larger crystal as cleavage faces are quite evident; however, I do not have a complete crystal. The interesting “thing” about the barite is that specimens “fluoresce various shades of pink, green and yellow under shortwave ultraviolet light” Roberts and Rapp, 1965). I simply could not get a good photo of my specimen fluorescing mostly yellow.
Pringle is a small community south of Custer that may be best known for gemmy rose quartz at the White Elephant Mine. However, there is also an agate variety known mostly to local collectors as Pringle Agate. I have been unable to locate much information except a rock shop owner noted the variety is generally described as a “bleached or washed out” Fairburn! I picked up mine decades ago in some sort of a gravel pit whose location has been removed from the back recesses of my mind. This summer I tried, without success, to relocate that quarry.
I had friends and relatives visiting our camp site this summer so it was off to pound rocks at Teepee Canyon near Jewel Cave west of Custer (see Blog dated 6/18/12. The dolomite of the Minnelusa Formation is quite tough and demands a crack hammer of good size, as well as eye protection. Our group had really good luck simply breaking open large rocks that had been quarried out by previous prospectors. I find it simply amazing that thousands of tons of the dolomite have been pried out of outcrops with mostly hand tools. These quarries extend for several miles along outcrop strike and some may now be under claim (check with the Forest Service in Custer).
And finally in the agate category, I noticed a bowl of small for sale “agates” in a rock shop labeled “Pukwana Agates.” That immediately caught my attention since I met several people from Pukwana during my stay at the University. The small village is located in the glaciated lowlands 10 miles east of Chamberlain (and the Missouri River). Pukwana, at one time, was home to the annual Turkey Race celebration and a small factory producing Red Devil car alarms (check out Ebay). Today, on Saturday nights, it hosts lawnmower races (check out U Tube). However, during my numerous visits over the years I have never seen any sort of a gravel quarry or location where one might find agates or even pieces chalcedony. The pastures and fields have cobbles of igneous rocks dropped by the Pleistocene glacier but cryptocrystalline quartz is absent. The rock shop employees barely knew the location of Pukwana and certainly could not comment on the agates. My guess is that the name Pukwana is a unique name and tourists might spend a buck (like me) taking home an agate—well a piece of chalcedony.
|The "Stransky Building" once housed a company manufacturing Red Devil Car Alarms. It now is the home of a bar, the Puk U.|
|Races on Saturday nights.|
|A "Pukwana Agate," collecting locality unknown. Width ~1.7 cm.|
Don’t drink the water---I wish someone would have told me early on! In 1853 two geologists, Dr. F.V. Hayden and F.B. Meek, visited the Badlands region. Both were to receive national recognition later as distinguished scientists. They spent several days at Sage Creek, noted by travelers for the purgative qualities of its water. Both men and their horses experienced a weakening effect after drinking from the stream (National Park Service information). I simply got “violently” ill drinking some of the local well water!
Hayden, F. V.,1857, Notes Explanatory of a Map and Section Illustrating the Geological Structure of the Country Bordering on the Missouri River, from the Mouth of the Platte River to Fort Benton, in lat. 470 30' N., long. 1100 30' W. Proc. Acad. Nat. Sci. Philadelphia, v. 9, pp. 109-116, map.