It is much like counting tree rings and can be used as evidence that young earth creationism is incorrect, since some notable examples, if actually annual, indicate an age of the earth greater than 10,000 years.
Varve chronologies are a window to the past and have been used to study past climate conditions, the periodicity of volcanic eruptions and as an independent test of radiocarbon (C14) dating methods.
Varve dating has a greater significance than just for local dating, since frequently there is enough organic material to allow radiocarbon dates to be calculated.
There is therefore the possibility of using the calendrical varve chronology to calibrate radiocarbon dates.
Some secular geologists believe that varves may actually be diurnal, reflecting tides instead of seasonal causes.
If this is so, formations like the Elatina Formation in South Australia (which is about 250 meters thick) could be accounted for in a mere 60 years.(Williams & Schmidt p.