Date of this Version
Published in Transactions of the Nebraska Academy of Sciences, Volume 4 (1977).
The concept of a "terrace-cyole" in the Quaternary history of the Central Great Plains was fust proposed by us at the 1944 "Symposium on Loess," sponsored by 1his Academy (1945). However, certain aspects have never been fully presented, particularly (a) the relations of drought to this "terrace-cycle" concept and (b) as a recurrent phenomenon in this and similar continental regi,pns. There also may be a possible relation to the fixation of sodium salts in vegetation and to selenium and nitrogen poisoning. Prediction requires scientific data not only from the near past, but also from the distant past. It is now obvious that erosional breaks in the younger valleyfills in the terrace sequence coincide with breaks in the cultural and faunal successions.
The research of two former Academy members-lohn E. Weaver and Harry E. Weakly, and their associates-has supplied much background on drought. Also, the works of Donald B. Lawrence (1958) and Edward G. Gibson (1973)-with respect to sunspot minima of the ll-year, sunspot cycle-seem to be very important in relation to glaciation as well as to drought.