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Cut some grip strip and chink over it with Log Jam or Conceal.
Ryan, I would suggest using a foam backer rod (cut to fit) and then caulk over that You definitely do not want to "fill" it full of caulk or chinking as it will lose its bond and split - allowing moisture in. The caulk we prefer is CONCEAL and is mfg'ed by Sashco.
Grip strip with a sharp utility knife and template for the radius. Staple in place and chink over 1/4" thickness. http://www.permachink.com/log-home-accessories/grip-strip.html