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Figure F21. Indicative gamma ray attenuation (GRA) bulk density megasplice constructed from a stack of Leg 138 equatorial Sites 849, 850, and 851. Sites 849 and 851 were correlated to Site 850 using the Analyseries program (Paillard et al., 1996) and biostratigraphic datums to check the similarity in character of the curves. These records were stacked and averaged (three-point smooth), forming the Site 850 composite record. Site 844 was also correlated to the lower part of the Site 850 composite and appended to the bottom of the record in order to extend its range back to the middle Miocene. Expedition 320 Site U1335 (black curve) was correlated to the bottom of this composite record, again using biostratigraphic datums, to check the similarity in character of the two records near the join. This exercise was repeated to join Site U1335 to the Site 1218 record (green curve). Because the base of Site U1335 is several hundred meters below the seafloor, its compacted density was substantially offset from the Site 1218 values. A density offset value of 0.44 was added to all density values of the Site 1218 record. Near the Eocene/Oligocene boundary, the Site 1218 density record was correlated to that of Site 1334 (the site with the highest carbonate content) with an added density offset of 0.22 (purple curve). This completes the megasplice density record back to the top of the middle Eocene. rmcd = revised meters composite depth.
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