Integrating South Pacific Carbon Cycling and Climate History from Late Paleocene to Middle Eocene: an upper Slope Transect from Eastern New Zealand

Benjamin S. Slotnick
Rice University, Department of Earth Sciences
Houston, TX, USA
[email protected]

Prominent global carbon cycle variations operating on both long (>10e6) and short (<10e5) time scales span the Early Paleogene. The well-documented 58-52 Ma interval, which included a significant δ¹³C drop and related CCD deepening, was superimposed by a series of hyperthermal events, each associated with a rapid δ¹³C drop and CCD shoaling. A current issue is whether such hyperthermals occurred during the Late Paleocene and Middle Eocene. The problem partly arises because of a relatively shallow CCD before 58 Ma and after 52 Ma. As such, well-resolved, single-site deepsea records spanning the entire interval are rare. To better understand and constrain Late Paleocene to Middle Eocene carbon cycle changes, we extend carbon isotope and carbonate content records from middle-upper slope and shelf break proto-New Zealand sections now located in Clarence Valley. The new data compliments previous work at these localities, such that detailed records now extend from 58-38 Ma. The long-term δ¹³C drop from 58-52 Ma was followed by a long-term δ13C rise. Numerous geologicallybrief (<0.2 Myr) but relatively small carbon isotope excursions occur through this interval, although it is not clear if they are hyperthermals. In addition, late Early Eocene strata have lower carbonate contents than beds that span the numerous yet distinct clay-rich Early Eocene hyperthermals, an indication that carbonate flux to the seafloor decreased, either because of lower surface water carbonate production or extreme lysoclinal shoaling. These records broadly correlate to preliminary records from other Clarence Valley sections and the southerly Canterbury Basin paleotemperature record.

AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects