Sandstone Pipe In Sandstone
Sandstone pipes are vertical cylindrical features that are commonly preserved in the St. Peter Sandstone in northern Arkansas. They are made up of the same sand as the surrounding rock. These features were observed in Ordovician-aged sandstone in Arkansas by geologists as early as 1916. Research by other scientists showed that these pipes formed in sand that was slightly deformed by a column of water rising through it from a lower horizon and feeding a spring at the surface. This sand then lithified into the rock we see today which includes the sandstone pipe. A modern-day example of sandstone columns forming in springs is present in the Dismal River, in the Nebraska Sand Hills. At this location, boiling (motion from water pressure, not temperature) sand springs have developed, fed by groundwater moving upward along cylindrical conduits. In the picture above, the sandstone surrounding the pipe has eroded away leaving the sandstone pipe standing in relief.
Another good week in the field, though did get soggy. Still seeing some vibrant fall colors. Seems like this year it just goeson and on. Monday we hiked up one of the last major hollows up the Middle Fork from Shirley that we haven’t already seen. Of course, once we got as far up as we could, it started raining. We were soaked through the rest of the afternoon, all the way back to the Jeep.
The next day things were still wet while we finished up at the confluence of that hollow with the Middle Fork, then headed up to a spot much higher in section to see if we could discern what appears in the contours (and on GoogleEarth) to be a syncline in the Witts Springs high up on John Henry Mountain.
It is a very difficult spot to get to and probably one of the steepest areas on the map. Although the rock is dipping, we didn’t get a sense of any structure other than perhaps it’s part of the large monocline that dips toward a possible southwest/northeast fault in the valley to the southeast. Wednesday was rainy again, so we worked our way through part of the vast road network built during the early days of the Fairfield Bay real estate boom which, I believe was in the early 1970’s. The (dirt) roads, along with numerous cul-de-sacs are still there with their names proudly displayed on rusting corner signposts. There are probably hundreds of lots still marked with little, hand-painted signs, now covered with lichen, noting the buyers name and hometown. Apparently none of them ever built, which was a boon for us, because the undeveloped subdivision gave us great access to a fairly large area north of Highway 16 in the southeast corner of the Shirley quad.
Until next week, see you in the field!