Ice cores from Greenland glaciers are 100's of thousands of years old- and perhaps easier to understand,
is the sediment cores bored out of bottom of arctic lakes in Alaska- they show seasonal lines in the sediment from silt washed into the lakes from spring runoffs. The yearly lines are continuous and often go way past 10,000 years. They can also carbon date the pollen found in those silt layers. A global flood would have obliterated those sediment records.
I called professor Richard Alley at Penn State Univ, who was on the Greenland team and he talked to me for an hour ( mid 90's)- he told me all about the glacial lakes core bores. You never read any stories in the Awake about this science. Prof. Alley wrote a book- The two Mile Time Machine- I have a copy.