A High‐Fidelity Benthic Stable Isotope Record of Late Cretaceous–Early Eocene Climate Change and Carbon‐Cycling

Abstract

The Late Cretaceous–Early Paleogene is the most recent period in Earth history that experienced sustained global greenhouse warmth on multimillion year timescales. Yet, knowledge of ambient climate conditions and the complex interplay between various forcing mechanisms are still poorly constrained. Here we present a 14.75 million‐year‐long, high‐resolution, orbitally tuned record of paired climate change and carbon‐cycling for this enigmatic period (~67–52 Ma), which we compare to an up‐to‐date compilation of atmospheric pCO2 records. Our climate and carbon‐cycling records, which are the highest resolution stratigraphically complete records to be constructed from a single marine site in the Atlantic Ocean, feature all major transient warming events (termed “hyperthermals”) known from this time period. We identify eccentricity as the dominant pacemaker of climate and the carbon cycle throughout the Late Maastrichtian to Early Eocene, through the modulation of precession. On average, changes in the carbon cycle lagged changes in climate by ~23,000 years at the long eccentricity (405,000‐year) band, and by ~3,000–4,500 years at the short eccentricity (100,000‐year) band, suggesting that light carbon was released as a positive feedback to warming induced by orbital forcing. Our new record places all known hyperthermals of the Late Maastrichtian–Early Eocene into temporal context with regards to evolving ambient climate of the time. We constrain potential carbon cycle influences of Large Igneous Province volcanism associated with the Deccan Traps and North Atlantic Igneous Province, as well as the sensitivity of climate and the carbon‐cycle to the 2.4 million‐year‐long eccentricity cycle.

The Magnitude of Surface Ocean Acidification and Carbon Release During Eocene Thermal Maximum 2 (ETM‐2) and the Paleocene‐Eocene Thermal Maximum (PETM)

“…(c) Bulk carbonate δ 13 C during ETM-2 from Sites 1209 (burgundy line;Gibbs et al, 2012), 1210 (open burgundy circles; this study), and 1265 (light purple line;Stap et al, 2009). Panels b and c are placed on the Ypresian age model ofWesterhold et al (2017), consistent with the Late Cretaceous-Early Eocene age model ofBarnet et al (2019).…”

“…(a) Late Paleocene‐Early Eocene (LPEE) benthic δ 13 C and δ 18 O records from ODP Sites 1209 (red and orange) and 1262 (blue and light blue), compiled by and placed on the age model of Westerhold et al () and Barnet et al (), respectively. (b) Benthic δ 13 C and δ 18 O records during Eocene Thermal Maximum 2 (ETM‐2) from ODP Sites 1209 (closed red and orange circles; Harper et al, ; McCarren, ), 1210 (open red and orange circles; this study), and 1265 (blue and light blue lines; Stap, Lourens, Thomas, et al, ).…”

Expedition 378 Preliminary Report: South Pacific Paleogene Climate

“…High-quality, multiple-hole cored Cenozoic sedimentary successions from the Atlantic (ODP Legs 171B, 207, and 208 and Inte-grated Ocean Drilling Program Expedition 342) and Pacific (ODP Legs 198 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321) yielded high-resolution geochemical records that also led to the development of astronomically calibrated age models (e.g., Röhl et al, 2007;Westerhold et al, 2011Westerhold et al, , 2018Littler et al, 2014;Lauretano et al, 2016;Barnet et al, 2019). Expedition 378 will contribute a unique section including crucial time intervals for the South Pacific area that will be integrated into the global chronostratigraphy.…”

Global mean surface temperature and climate sensitivity of the EECO, PETM and latest Paleocene

“…56 Ma) and iii) the latest Paleocene (LP,. We use six independent methods to obtain new GMST estimates for these three time periods, employing recently compiled datasets of SST and LAT estimates (Hollis et al, 2019) and BWT estimates (Cramer et al, 2009;Westerhold et al, 2018;Barnet et al, 2019). We also undertake a suite of additional sensitivity studies to explore the influence of particular proxies on each GMST estimate.…”

“…Dataset Ddeep consists of bottom water temperatures (BWTs) for the latest Paleocene, PETM and EECO. Benthic foraminifera δ 18 O values for the latest Paleocene, PETM and EECO come from previous compilations (Westerhold et al, 2018;Barnet et al, 2019;Cramer et al, 2009), adjusted to Cibicidoides following established methods (Cramer et al, 2009), allowing temperature to be calculated using Eq. 9 of Marchitto et al 2014:…”