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.
Abstract An integrated stratigraphic study of the upper Paleocene to lower Eocene Scaglia limestones of the Contessa Road section has allowed us to identify the classical markers of the Paleocene-Eocene transition. The section provides a good magnetostratigraphic record as well as a continuous calcareous nannofossil and foraminiferal biostratigraphy. A negative Carbon Isotopic Excursion (CIE) occurs in the lower part of Chron C24r. The calibration to calcareous plankton zonation indicates that the CIE occurs in the lowermost part of calcareous nannofossil Zone NP10 and the upper part of Zone CP8, that is in the planktonic foraminiferal Zone P5. In the same stratigraphic interval, a distinct turnover in the calcareous benthic foraminifera and a sharp change in the Deep Water Agglutinated Foraminiferal (DWAF) assemblages have been recognised. The record of DWAF, however, indicates a gradual initiation of such a change beginning some 150 k.y. before the CIE and BEE.
A new analysis of Deep Sea Drilling Project (DSDP) Leg 84 data demonstrates that the dominant process controlling the Guatemala margin tectonic evolution since ca. 25 Ma is subduction-erosion. Data from benthic foraminifera, assemblages from upper-slope DSDP Sites 568, 569, and 570 indicate long-term, progressive subsidence from upper to middle bathyal depths (600‐1000 m) ca. 19 Ma to modern abyssal depths (.2000 m). Rapid subsidence migrated landward starting at the Oligocene-Miocene boundary time under the current middle slope, where it increased sharply ca. 19 Ma, reached the current upper slope by ca. 15 Ma, and arrived at the uppermost slope ca. 2 Ma. Subsidence indicates crustal thinning by basal tectonic erosion of mass from the underside of the upper plate. Under the assumption that, in the Miocene, the morphology of the forearc was similar to that of today, landward migration of the trench was at a rate of 0.8‐0.9 km/m.y. This linear rate corresponds to a tectonic erosion rate of the submerged forearc of 11.3‐13.1 km 3 ·m.y. 21 ·km 21 . The evolution of arc magmatism and superfast spreading at the East
Chron C17n (magnetostratigraphy).Cyclostratigraphic analysis of the Bartonian-Priabonian transition of the Alano section as well as radioisotopic data of the Tiziano tuff layer provide an absolute age (37.710 -37.762Ma, respectively) of this bed and, consequently, of the base of the Priabonian Stage.
