Orbital chronology of Early Eocene hyperthermals from Site RH-323, Northern Negev (Israel)

The early Eocene (~56-49 Ma) is punctuated by several transient global warming events, known as hyperthermals, superimposed on very high mean global temperatures and elevated atmospheric CO2 levels. Hyperthermal events, such as the well-documented Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma), are characterized by negative carbon isotope excursions. These are interpreted as perturbations in the global exogenic carbon pool and deep ocean carbonate dissolution - signifying massive carbon injection into the ocean-atmosphere system. High resolution analysis of sedimentary archives has evidenced that hyperthermals initiated during maxima in orbital eccentricity, suggesting a climatic trigger for carbon input. Cyclostratigraphy, therefore, provides a unique tool to complement proxy records in the characterization of hyperthermal. Indeed, the identification of an orbital signature in marine and continental sedimentary succession provides an ideal trait-d’union between stratigraphic observation and paleoceanographic/paleoclimatic interpretation.

Here we present a cyclostratigraphic study of early Eocene marls and chalks from core RH-323, collected from the northern Negev Desert in Israel. The PETM in this region is well described but other hyperthermals are essentially unexplored. The unique location of this sedimentary succession, accumulated on a continental slope of the South Tethys at ~ 500–700 m paleo-depth, provides new insights into the relationship between global oceanic perturbation and local variability in a relatively arid region. Eccentricity-dependent variation in magnetic susceptibility and bulk stable oxygen and carbon isotope data from this locality allowed us to develop an astronomically tuned age model, which contributes to the identification of important hyperthermals, including the PETM, ETM2 and ETM3. The patterns also allow for cycle and event-based correlation to and comparison with oceanic records such as Ocean Drilling Program (ODP) Sites 1262 (Atlantic Ocean) and 1209 (Pacific Ocean) and with outcropping sections of the Tethys such as those of Contessa Road and Bottaccione (Gubbio, Italy). Emerging from these comparisons are remarkable patterns in the occurrence of cherts, with potential relevance for the global silicon cycle.