Thorium-234 and Thorium-228 
  U.S. GEOTRACES Arctic (HLY1502; GN01) 
  PI: Ken Buesseler (WHOI) 
  Co-PIs: Matt Charette (WHOI) & Willard Moore (University of South Carolina) 
  Version history: 
   2020-10-12 (v2; current) - corrected GEOTRACES Sample_ID numbers in event #6234 
   2020-06-01 (v1) - original version served