Carbonate saturation dynamics during the Paleocene–Eocene thermal maximum: Bathyal constraints from ODP sites 689 and 690 in the Weddell Sea (South Atlantic)

• Published in: Marine geology Vol. 303-306; pp. 75 - 86
• Main Authors: Kelly, D. Clay, Nielsen, Tina M.J., Schellenberg, Stephen A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.2012
• Subjects: Biochemistry; Carbon; carbonate sedimentation; Carbonates; Compensation; Dissolution; Intervals; lysocline; Marine; ODP Site 689; Paleocene–Eocene thermal maximum; Recovery; Sedimentation; Weddell Sea; ODP Site 689; Weddell Sea; Paleocene–Eocene thermal maximum; carbonate sedimentation; lysocline
• ISSN: 0025-3227; 1872-6151
• DOI: 10.1016/j.margeo.2012.02.003

Spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient (~55.5Ma) global warming event known as the Paleocene–Eocene thermal maximum (PETM), yet the magnitude of lysocline shoaling in the Southern Ocean is poorly constrained due to limited spatial coverage in the circum-Antarctic region. This shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the Site 690 PETM reference section to those herein reconstructed for nearby Site 689. Biochemostratigraphic correlation of the two records reveals that the first ~36ka of the carbon isotope excursion (CIE) signaling PETM conditions is captured by the Site 689 section, while the remainder of the CIE interval and nearly all of the CIE recovery are missing due to a coring gap. A relatively expanded stratigraphy and higher carbonate content at mid-bathyal Site 689 indicate that dissolution was less severe than at Site 690. Thus, the bathymetric transect delimited by these two PETM records indicates that the lysocline shoaled above Site 689 (~1,100m) while the calcite compensation depth remained below Site 690 (~1,900m) in the Weddell Sea region. The ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification. Further, biochemostratigraphic evidence indicates the tail end of the CIE recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters. ► We provide added constraints on lysocline movement in Southern Ocean during PETM. ► First 36ka of PETM are captured by the Site 689 record. ► Lysocline initially shoaled to depths shallower than Site 689 (~1,100m). ► Site 689 PETM section is much thicker than correlative part of Site 690 section. ► Carbonate sedimentation recovered earlier at Site 689 than at deeper Site 690.