Clovis and Folsom age estimates: Stratigraphic context and radiocarbon calibration

The events to do with peopling the New World archaeologically represented by 'Clovis' and 'Folsom' have been - tantalizingly - beyond the range of radiocarbon calibration. Now calibration extends further, one can ask if the abruptness of Clovis, of Folsom, and of the transition between them are realities. A calibrated chronology for those sites where the stratigraphic security is best shows these in truth are rapid human affairs.