In March 2004, a geological team from the University of Wisconsin found evidence of cyclical changes in cosmic ray bombardment of rocks. They didn't assume from that, that the rate of bombardment was cyclical. Since cosmic rays don't penetrate very far, they took it as evidence that the rocks were intermittently covered by ice. Their work showed that ice ages are globally simultaneous, rather than local, events.
I know you're familiar with the CHRONOS PROJECT:
Kirkby and Mangini analyzed ocean sediments rather than surface rock. Is it possible that the variation they found is due to changes here on Earth, rather than in the rate of cosmic ray bombardment? i.e. changes in dust levels in the atmosphere, or in the rate of erosion by wind and/or water?