Paper No. 38-20
Presentation Time: 8:00 AM-12:00 PM
A PRELIMINARY ASSESSMENT OF THE CONSISTENCY OF NEOGENE SEA SURFACE TEMPERATURE ESTIMATES FROM THE UK’37 AND TEX86 PALEOTHERMOMETERS
A variety of different proxies have been employed to reconstruct past sea surface temperature (SST). Several studies applying different paleothermometers to sediments from the same site have yielded dissimilar estimates of past SST, leading to conflicting interpretations of past climate system behavior. These discrepancies have revealed a need to explore the consistency of climate estimates from different SST proxies. The Uk’37 index, is a well-vetted and widely employed paleothermometer. Contrastingly, TEX86 is a relatively new technique for reconstructing past temperature, which is potentially particularly useful in high temperature environments (>29ºC) where the Uk’37 index reaches saturation. Previous studies that have undertaken paired measurements show temperature offsets and/or reveal differing down core patterns for records derived from these two proxies. Here, we explore long-term (>1 Myr), orbital resolution, paired Uk’37 and TEX86 SST reconstructions from the late Miocene and Pliocene at Site ODP 1088 (41ºS) in the South Atlantic Ocean and Site ODP 846 (3ºS) in the Eastern Equatorial Pacific Ocean. At Site ODP 1088, our records which span ~2.4 to ~4 Ma reveal some intervals in which there is remarkable consistency in structure, absolute SST, and variability between estimates based on Uk’37 and TEX86 methods and others in which temperature estimates are offset by several degrees and variability of the TEX86 estimate is twice that of the Uk’37 estimate. At Site ODP 846, companion Uk’37 and TEX86 records for the interval from ~5.1 to ~6 Ma show similar structure, but TEX86 temperatures are consistently offset toward colder values by several degrees and variability of the TEX86 record is almost twice that observed in the Uk’37 record. These preliminary comparisons suggest additional research aimed at exploring factors such as diagenesis, ecology, seasonality, and calibration which might give rise to the differences observed between the two proxies should be undertaken. Until we better understand the factors that account for differences between Uk’37 and TEX86 estimates, caution should be used in treating records based on these proxies as interchangeable.