Monument Rocks, The Butterfield Overland Dispatch, and the Western Interior Seaway

In the 1865, the chalk formations of Monument Rocks, was a stop on the Butterfield Overland Dispatch stage route from Fort Riley to Denver. Soon, the 600 miles route fell victim to Indians and the railroad. Today, Monument Rocks can be found on a dusty trail, 25 miles south of I-70 and Oakley, Kansas, and a few miles east of southbound Highway 83.

Monument Rocks, Kansas
Monument Rocks, Kansas

The isolation of these rocks has helped to preserve them over the years. And in splendid loneliness one can imagine weary travelers dismounting from the stage to stretch their legs and get a meal before continuing on through a untamed country beset by Indians who wanted no part of the white man.

There is an older story associated with Monument Rocks.

Imagine a vast seaway stretching from Canada to Mexico. The weather is tropical. The seaway is as wide as the state of Colorado and half of Kansas. Now, one pictures what Kansas looked like 80 million years ago.

The 70 feet tall chalk formations of Monument Rocks were created during the Cretaceous Period, when the North American continent was split by a vast inland sea known as the Western Interior Seaway. This was a shallow sea, less than 600 feet, filled with plesiosaurs, reptiles which propelled themselves through the water by means of four long flippers, and the lizard-like mosasaurs, as well as sharks like the giant thirty foot clam-crushing Ptychodus mortoni, and the voracious fifteen foot long bony fish Xiphactinus. Other sea life included invertebrates such as mollusks, ammonites, and squid-like belemnites, whose fossil remains are common in the chalk formations, and plankton including coccolithophores, whose secretions of chalky platelets giving the Cretaceous its name. The sediments were laid down at a rate of about an inch of compacted chalk and fossil each 700 years, meaning that the formations consist of almost 600,000 years of sedimentation.

Monument Rocks
Monument Rocks

What is the difference between chalk and clay.

Chalk is a limestone consisting of coccolith, a deposit from the coccolithophore, a unicellular algae. The coccolithophores, for the most part, floated on the top of the seaway, and when they died, the microscopic calcite, which formed their shells settled down through the ocean water, accumulating on the ocean bottom and forming a calcareous ooze, which over time became hardened chalk. The thickness of the strata layer and the color might indicate a change in climate and plant life.

Clay is simply finely grained rock and soil.

DSC_0113 monumentRocks (8) monumentRocks (12) monumentRocks_close

Maps of the Western Interior Seaway.


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