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Abstract. Coherent variation in CaCO₃ burial is a feature ofthe Cenozoic eastern equatorial Pacific. Nevertheless, there has been along-standing ambiguity in whether changes in CaCO₃ dissolution or changesin equatorial primary production might cause the variability. Sinceproductivity and dissolution leave distinctive regional signals, a regionalsynthesis of data using updated age models and high-resolution stratigraphiccorrelation is an important constraint to distinguish between dissolutionand production as factors that cause low CaCO₃. Furthermore, the newchronostratigraphy is an important foundation for future paleoceanographicstudies. The ability to distinguish between primary production anddissolution is also important to establish a regional carbonate compensationdepth (CCD). We report late Miocene to Holocene time series of XRF-derived (X-rayfluorescence) bulk sediment composition and mass accumulation rates (MARs) from easternequatorial Pacific Integrated Ocean Drilling Program (IODP) sites U1335,U1337, and U1338 and Ocean Drilling Program (ODP) site 849, and we also report bulk-density-derived CaCO₃ MARs at ODP sites 848, 850, and 851. We usephysical properties, XRF bulk chemical scans, and images along withavailable chronostratigraphy to intercorrelate records in depth space. Wethen apply a new equatorial Pacific age model to create correlated agerecords for the last 8 Myr with resolutions of 1–2 kyr. Large magnitudechanges in CaCO₃ and bio-SiO₂ (biogenic opal)more »MARs occurred withinthat time period but clay deposition has remained relatively constant,indicating that changes in Fe deposition from dust is only a secondaryfeedback to equatorial productivity. Because clay deposition is relativelyconstant, ratios of CaCO₃ % or biogenic SiO₂ % to clayemulate changes in biogenic MAR. We define five major Pliocene–Pleistocene low CaCO₃ % (PPLC) intervalssince 5.3 Ma. Two were caused primarily by high bio-SiO₂ burial thatdiluted CaCO₃ (PPLC-2, 1685–2135 ka, and PPLC-5, 4465–4737 ka),while three were caused by enhanced dissolution of CaCO₃ (PPLC-1, 51–402 ka, PPLC-3, 2248–2684 ka, and PPLC-4, 2915–4093 ka). Regional patterns ofCaCO₃ % minima can distinguish between low CaCO₃ caused by highdiatom bio-SiO₂ dilution versus lows caused by high CaCO₃dissolution. CaCO₃ dissolution can be confirmed through scanning XRFmeasurements of Ba. High diatom production causes lowest CaCO₃ %within the equatorial high productivity zone, while higher dissolutioncauses lowest CaCO₃ percent at higher latitudes where CaCO₃ production islower. The two diatom production intervals, PPLC-2 and PPLC-5, havedifferent geographic footprints from each other because of regional changesin eastern Pacific nutrient storage after the closure of the Central American Seaway.Because of the regional variability in carbonate production andsedimentation, the carbonate compensation depth (CCD) approach is onlyuseful to examine large changes in CaCO₃ dissolution.