BARTAK DEPRESSION OR MERNA CRATER - THE ORIGIN OF A LANDSCAPE FEATURE IN CUSTER COUNTY, NEBRASKA

The loess-covered tablelands of central Nebraska are covered with numerous depressions varying greatly in size. The depressions are generally concentrated in two areas; the Rain Water Basin Area of south-central Nebraska and the Central Nebraska Loess Hills of north-central Nebraska. One large depression is located in Custer County near the town of Merna. The depression is referred to as the "Bartak Depression" by the locals because it is located on property owned by the Bartak family. This depression has been the focus of interest since it was renamed the Merna Crater in the 1997 article "Merna Crater- A young impact feature in loess of Central Nebraska" published in the Oklahoma Geological Survey Circular by Dort, Zeller, Martin and Moody. Dort et al. concluded that the depression was probably created by the explosion of an extraterrestrial bolide which occurred about five kilometers above the land surface. They estimate the explosion occurred about 3000 years ago.

Results of test holes drilled in and adjacent to the depression show that the stratigraphic units including the Peoria Loess (25,000 to 11,000 YBP) carry through the landscape adjacent to and beneath the depression with no disruption. This indicates that the depression was not formed by the explosion of a bolide that occurred about 3000 years ago. The origin of the depression may be similar to that of other depressions found throughout Nebraska.