My next post about the Geology of the National Parks Through Pictures is from our move across the country from Utah to New York. Along the way we visited 13 National Parks as well as some other sites. This was the 11th National Park along the way.
You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website
Dinojim.com.
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Obligatory entrance sign photo
Pipestone National Monument is a sacred Native American site, known as Inyan Sa K'api to the Dakota People. It is here that they quarry the pipestone rock in order to carve pipes for ceremonial use, as well as other objects with smaller pieces of the rock.
The geology of Pipestone National Monument has three distinct rock types. The two primary rock types are quartzite and the pipestone layer. Seen in the picture above, the floor of this outcrop quarry is the Sioux Quartzite. At the base of the wall in the picture is a thin red layer. This layer is the pipestone layer, a rock known as catlinite or Siouz Argillite. Above the Catlinite is the continuation of the Sioux Quartzite, with the third type of rock in the park, conglomerate, above the quartzite.
The Sioux Quartzite initially formed ~1.6 billion years ago along a braided river system. This is similar to what is seen in many rocky mountains and colder climate regions today (such as
Canada's Banff National Park). Within the quartzite formation, several different types of deposits can be seen including different portions of the braided river system like channel-floor lag deposits, in-channel deposits, nearly filled channel deposits, and vertical accretion deposits. The sand grains within the quartzite are primarily comprised of quartz and were eventually cemented together with silica (dissolved sand grains) forming a quartz sandstone.
The red colors within the quartzite are caused by various minute amounts of iron oxide (AKA hematite, AKA rust). Over time, the quartz sandstone was buried and subjected to extreme heats and pressures. This essentially melted the quartz sand grains and silica cement, intermixing them to produce a solid mass of quartz. The result is a metamorphic rock known as a quartzite, a rock that is harder than ordinary steel.
Within the Sioux Quartzite is a layer of clay, which is the pipestone layer, catlinite. The clay was deposited within the braided river system along the floodplains. When rivers flood, they break across their natural levees and deposit clay and other fine sediment along the neighboring shorelines. Within braided river systems these clay deposits are rarely preserved, though, because eventually they are eroded away as the river system meanders across the landscape. Despite the odds, this deposit of clay was preserved by a fast burial of sand on top of the clay, preventing erosion.
Named after the American Painter, George Catlin, who visited the quarries in Minnesota in 1835, catlinite is unique to this region. Catlinite is made up of a unique combination of several clay minerals including pyrophyllite, diaspore, muscovite, kaolinite, and traces of hematite (producing the red, rust, color). Most notably, there is little to no quartz found within the catlinite deposit. The resulting rock is very dense but very soft, about the same hardness as a human finger nail, making it remarkably easy to carve. The same metamorphic processes that happened to the surrounding Sioux Quartzite, were also inflicted upon the catlinite, producing this low grade metamorphic rock.
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| Quarry representation. Courtesy of the NPS. |
In the words of George Catlin:
"For many miles we had the Coteau in view in the distance before us, which looked like a blue cloud settling down in the horizon . . . On the very top of this mound or ridge, we found the far-famed quarry or fountain of the Red Pipe, which is truly an anomaly in nature. The principal and most striking feature of this place, is a perpendicular wall of close-grained, compact quartz, of twenty-five and thirty feet in elevation, running nearly North and South with its face to the West, exhibiting a front of nearly two miles in length, when it disappears at both ends by running under the prairie . . . At the base of this wall there is a level prairie, of half a mile in width, running parallel to it; in any and all parts of which, the Indians procure the red stone for their pipes, by digging through the soil and several slaty layers of the red stone, to the depth of four or five feet. From the very numerous marks of ancient and modern diggings or excavations, it would appear that this place has been for many centuries resorted to for the red stone; and from the great number of graves and remains of ancient fortifications in its vicinity, it would seem, as well as from their actual traditions, that the Indian tribes have long held this place in high superstitious estimation; and also that it has been the resort of different tribes, who have made their regular pilgrimages here to renew their pipes.”
(Quote from Gurney and Heyman 2002)
While extracting the pipestone from the quarry, the overlying quartzite is slowly removed. There are several rubble piles, like pictured in the images above and below, that are produced from the overburden of the unneeded quartzite above the pipestone layer. The quarries are still mined today by Native American groups and have been for centuries. In the area surrounding the below rubble pile, Native Americans first discovered the pipestone. In this region the pipestone has had the hematite partially leached from the stone, causing speckles within the rock. These speckles are termed "spotted" pipestone.
The overlying conglomerate, as well as other features throughout the park, including glacial erratics (known as the Three Maidens towards the entrance of the park), striations (scratches in the quartzite), and till (the overlying conglomerate and other sediment), represent the remains of glacial activity throughout the park.
The glacial deposits within the park are thought to date between 800,000 and 500,000 years ago, some of the oldest in North America. While there are many significantly younger glacial deposits across the continental US, they did not cover the park. These glacial deposits are from the Ice Age, when vast sheets of ice covered the northern portions of the continent, dragging rocks and other debris along their bases. As they reached their limits and started to melt away, the dropped the materials they were carrying, often in a conveyor belt fashion, forming piles along their furthest extents. These piles are what are known as till, and include other artifacts like random boulders known as erratics.
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Winnewissa Falls
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Through the park runs Pipestone Creek, forming Winnewissa Falls (as seen above). The water falls are produced as the creek flows over the resistant Sioux Quartzite, the to excavated lower unit of the Sioux Quartzite below the Pipestone layer.
References
Gurney, G. and T. T. Heyman, editors. 2002. George Catlin and his Indian Gallery. Smithsonian American Art Museum, Washington, DC and W. W. Norton and Company, New York, New York.
