Abstract:
We present a new multiproxy (TEX (sub 86) , delta (super 18) O and Mg/Ca), marine temperature history for Canterbury Basin, eastern New Zealand, that extends from middle Paleocene to middle Eocene, including the Paleocene-Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). In light of concerns that proxy-based sea surface temperature (SST) estimates are untenably warm for the southwest Pacific during the Eocene, we review the assumptions that underlie the proxies and develop a preliminary paleo-calibration for TEX (sub 86) that is based on four multiproxy Eocene records that represent an SST range of 15-34 degrees C. For the southwest Pacific Paleogene, we show that TEX (sub 86) (super L) exhibits the best fit with the Eocene paleo-calibration. SSTs derived from related proxies (TEX (sub 86) (super H) , 1/TEX (sub 86) ) exhibit a systematic warm bias that increases as TEX86 values decrease (a warm bias of 4-7 degrees C where TEX (sub 86) <0.7). The TEX (sub 86) (super L) proxy indicates that southwest Pacific SST increased by approximately 10 degrees C from middle Paleocene to early Eocene, with SST maxima of 26-28 degrees C (tropical) during the PETM and EECO and an SST minimum of 13-16 degrees C (cool-warm temperate) at the middle/late Paleocene transition (58.7 Ma). The base of the EECO is poorly defined in these records but the top is well-defined in Canterbury Basin by a 2-5 degrees C decrease in SST and bottom water temperature (BWT) in the latest early Eocene (49.3 Ma); BWT falls from a maximum of 18-20 degrees C in the EECO to 12-14 degrees C in the middle Eocene. Overall, cooler temperatures are recorded in the mid-Waipara section, which may reflect a deeper ( approximately 500 m water depth) and less neritic depositional setting compared with Hampden and ODP 1172 ( approximately 200 m water depth). The high SSTs and BWTs inferred for the PETM and EECO can be reconciled with Eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto-East Australian Current is taken into account. Abstract Copyright (2012) Elsevier, B.V.