Hutch salt field has prehistoric beginnings

Sunday, September 27, 1987

The salt pulled to the surface by the Carey, Morton and Cargill companies today hasn't seen daylight in more than 200 million years.

It was in the Permian period of the Upper Paleozoic era - 280 million to 225 million years ago - in which geologists think the salt of Kansas settled out inch by inch through the evaporation of sea water.

In those years, the Southern Hemisphere was in the grip of an ice age. The Appalachian mountain range was being thrown up on the eastern part of the continent. Across Kansas, Texas, New Mexico and part of Colorado stretched a shallow bay 650 miles long and about 200 miles wide populated by crustaceanlike creatures called trilobites and early varieties of shark.

The major inhabitants of the land were sail-backed reptiles called pelycosaurs and cotylosaurs, who would evolve into the dinosaurs of the Mesozoic era and eventually into modern birds and reptiles.

Somehow, the bay that covered Kansas was partially cut off from the sea, forming a shallow lagoon. Remnants of this ancient salt sea are still visible in pockets of water contained in some of the rocks pulled from the Carey salt mine.

As water evaporated from the lagoon, salt was left behind, and as salt in the water got more concentrated, it began to settle onto the bottom. Geologists think new water from the ocean poured into the lagoon to replace what was lost, bringing more salt, and the deposit grew thicker.

Unlike minerals such as limestone, which need thousands of years to build up to any real thickness, salt can accumulate rapidly under the right conditions. Salt might have been laid down at a rate of several inches per year in this basin, which had become a gigantic solar evaporation pan.

The deposit was mostly sodium chloride, but it also contained about 3 percent calcium sulfate and traces of shale, calcium chloride and magnesium chloride.

After that, the geological picture is less clear. The sea level may have gone up, deepening the Kansas lagoon, or the ground may have subsided and brought in a fresh flood of sea water.

However it happened, the buildup of salt stopped, and the layers of rock salt began to be covered with the silt and vegetable matter that would later become Kansas' fertile soil.

With 650 feet of shale, rock and sand over it, the white treasure of central Kansas settled in to wait for a wheeler-dealer real estate promoter named Ben Blanchard to bring back the daylight.