NEODYMIUM ISOTOPIC RECONSTRUCTION OF LATE PALEOCENE - EARLY EOCENE THERMOHALINE CIRCULATION

High-resolution Nd isotopic records constructed from fossil fish teeth reveal the composition of the Atlantic, Southern, Indian, and Pacific Oceans and Caribbean Sea during the late Paleocene - early Eocene. Sites in the Atlantic, Indian and Southern Oceans (Sites 213, 401, 527, 549, 690, and 1051) are characterized by relatively non-radiogenic Nd isotopic values (~-9.5 e_Nd(0)). More radiogenic e_Nd(0) values at intermediate depths in the Pacific (Site 865) and in the deep Caribbean (Site 1001) suggest that these water masses had different sources of Nd than the Atlantic, Indian or Southern Oceans. Neodymium isotopic records from the eight sites combined with paleogeographic reconstructions suggest that the dominant source of late Paleocene - early Eocene deep waters was the Indian and Atlantic sector of the Southern Ocean.

The Nd isotopic data suggest that a fundamental change in thermohaline circulation did not precede the onset of the carbon isotope excursion (CIE) at the P/E boundary. The relatively consistent Nd isotopic values within each major ocean basin across the onset of the Paleocene-Eocene thermal maximum (PETM) provide no evidence for a change in the location of deep-water formation. However, the intriguing feature that emerges from the e_Nd(0) data of P/E boundary interval is the possibility of a transient change in deep-water source regions and thermohaline circulation patterns as a consequence of the PETM warming. During the recovery phase of the CIE significant positive e_Nd excursions at Sites 213 and 527 correlate approximately with a negative excursion in Caribbean Site 1001. The convergence of South Atlantic (Site 527), Indian Ocean (Site 213) and Caribbean (Site 1001) deep waters toward an average Pacific e_Nd(0) value of ~-5 suggests the possibility of a transient tropical Pacific source of intermediate/deep waters. A paucity of fish teeth in the Site 401, 549, and 690 sections resulted in a gap in this portion of the record thus precluding identification of the radiogenic e_Nd(0) excursion in the North Atlantic and Southern Ocean.