We set out at the ushal time and at 8 miles West We passed point of Red Rocks about 600 yds from the river and at Eleven miles crossed the paney River?.Some Cottenwood on the Banks and Some Bushis. the Red Rock is evidently a volcanic production is porous like pomestone but heavier than Sand stone.
Jacob Fowler, fur trapper and trader
October 19, 1821
Fowler's 1821 journal entry appears to be the first recorded mention of Pawnee Rock. Fowler's geology is incorrect. Pawnee Rock is not volcanic igneous rock; it is sedimentary rock called Dakota Sandstone.
About 100 million years ago sandy and clay sediments were deposited along the edge of a vast sea that covered much of central North America. This layer—known as the Dakota Formation—was later buried beneath other sea depositions. The chemical makeup of these sediments determined their color, texture, and density. For example, sediments became harder in places of high iron concentration.
Over time periods of erosion have uncovered these sediments. More recently water draining toward the Arkansas River has stripped away the softer clay, silt, and sand deposits. This process has exposed the harder sandstone formations such as Pawnee Rock, which protrudes high above the surrounding plain.
You are standing somewhere near the shoreline of a vast shallow sea that occupied this spot millions of years ago.
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