Neodymium isotope ratios of Cretaceous fish teeth

• Main Authors: MacLeod, Kenneth G, Isaza-Londoño, Carolina, Martin, Ellen E, Jiménez Berrocosco, Álvaro, Basak, Chandranath
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 2011
• Subjects: Ocean Drilling Program; ODP; North Atlantic Deep Water; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.792572; https://doi.org/10.1594/PANGAEA.792572

The mechanics of ocean circulation during the Late Cretaceous greenhouse interval remain contested (MacLeod and Hoope, 1992, doi:10.1130/0091-7613(1992)020<0117:ETIBWB>2.3.CO;2; Frank and Arthur, 1999, doi:10.1029/1998PA900017; MacLeod and Huber, 2001; Abramovich et al., doi:10.1029/2009PA001843; Isaza-Londono et al., doi:10.1029/2004PA001130; MacLeod et al., 2005, doi:10.1130/G21466.1), with the role of North Atlantic Deep Water in ocean circulation particularly debated: the relative warming of the North Atlantic during the termination of the greenhouse interval has been attributed to heat piracy from North Atlantic Deep Water formation (Isaza-Londono et al., doi:10.1029/2004PA001130; MacLeod et al., 2005, doi:10.1130/G21466.1), but the sources of Cretaceous deep water have been difficult to resolve. Nd isotopes as captured by seafloor sediments and expressed as epsilon-Nd(t) reflect the region in which the water mass was formed. Here we present epsilon-Nd(t) measurements from Cretaceous- to Palaeogene-aged sediments from four cores in the tropical North Atlantic. Before 69 Myr ago, we find extremely low epsilon-Nd(t) values of about -16, consistent with the presence of a warm, saline deep water mass formed in the low latitudes (MacLeod et al., 2008, doi:10.1130/G24999A.1; Jiménez Berrocoso et al., 2010, doi:10.1130/G31195.1). By 62 Myr ago, epsilon-Nd(t) values had risen to -11, similar to values reported from the northern North Atlantic over the past 65 million years, but lower than most contemporaneous values in the South Atlantic (Robinson et al., 2010, doi:10.1130/G31165.1) and Pacific oceans ((MacLeod et al., 2008, doi:10.1130/G24999A.1; Frank et al., 2005, doi:10.1029/2004PA001052 ). We therefore suggest that the epsilon-Nd(t) shift reflects the increasing influence of a northern-sourced water mass at this site, indicating the onset or intensification of deep- or intermediate-water formation in the North Atlantic 69 Myr ago. Our findings support the heat piracy model and imply that circulation ...