An early Lutetian carbon‐cycle perturbation: Insights from the Gorrondatxe section (western Pyrenees, Bay of Biscay)

Abstract

A distinctive low‐carbonate interval interrupts the continuous limestone‐marl alternation of the deep‐marine Gorrondatxe section at the early Lutetian (middle Eocene) C21r/C21n Chron transition. The interval is characterized by increased abundance of turbidites and kaolinite, a 3‰ decline in the bulk δ13C record, a >1‰ decline in benthic foraminiferal δ13C followed by a gradual recovery, a distinct deterioration in foraminiferal preservation, high proportions of warm‐water planktic foraminifera and opportunistic benthic foraminifera, and reduced trace fossil and benthic foraminiferal diversity, thus recording a significant environmental perturbation. The onset of the perturbation correlates with the C21r‐H6 event recently defined in the Atlantic and Pacific oceans, which caused a 2°C warming of the seafloor and increased carbonate dissolution. The perturbation was likely caused by the input of 13C‐depleted carbon into the ocean‐atmosphere system, thus presenting many of the hallmarks of Paleogene hyperthermal deposits. However, from the available data it is not possible to conclusively state that the event was associated with extreme global warming. Based on our analysis, the perturbation lasted 226 kyr, from 47.44 to 47.214 Ma, and although this duration suggests that the triggering mechanism may have been similar to that of the Paleocene‐Eocene Thermal Maximum (PETM), the magnitude of the carbon input and the subsequent environmental perturbation during the early Lutetian event were not as severe as in the PETM.

Early Eocene climatic optimum: Environmental impact on the North Iberian continental margin

“…The new information complements and extends previously published geochemical (stable isotopes), mineralogical, and foraminiferal data from the Lower-Middle Eocene transition at the Gorrondatxe section (900-1100 m; Payros et al, 2012).…”

Integrated stratigraphy of the Ypresian–Lutetian transition in northern Tunisia: Correlation and paleoenvironmental reconstruction

“…The species richness of planktic foraminifera decreases by about 50% throughout the entire Sj.5-Sj.11 interval and in the middle of the E7b Zone (sample Sj.9). A similar drop in the planktic foraminifera was observed in the Gorrondatxe section at the top of the Chron C21r of the Y/L interval where the percentage of planktic foraminifera also decreases by 50% (Payros et al, 2012). At the top of the section, at the base of the E9 Zone (Sj.14), planktic foraminifera proliferate and thrive after the crisis, also the diversity decreases and cold seawater forms become slightly dominant.…”

“…These reflect very wet weather conditions at this time, with rainfall and mechanical alteration which increased in inland areas and were thus similar to many events in the Paleogene carbon cycle perturbation (Thiry, 2000;Schmitz et al, 2001;Pujalte, 2003, 2007;Nicolo et al, 2007;Agnini et al, 2009;Sluijs et al, 2009Sluijs et al, , 2011Spofforth et al, 2010;Payros et al, 2012). This interval is considerably depleted in carbonate and enriched SiO 2 , which is notable in the Gorrondatxe stratotype (Molina et al, 2011;Payros et al, 2012). Indeed, in this section, at the base of the Lutetian, there is an interval, at the transition from the Chron C21r/C21n, which is remarkable for its low carbonate content that interrupts the limestone-marl series (Fig.…”

“…These mineralogical variations suggest the climatic conditions: rather warm, tropical to subtropical and humid in northern Tunisia at the Y/L boundary. These warm conditions were probably inherited from the global warming that had already begun in the Paleocene/Eocene (Ortiz, 1995;Ben Ismail-Lattrache and Bobier, 1996;Karoui-Yaakoub, 1999Thomas et al, 2000;Karoui-Yaakoub et al, 2011;Payros et al, 2012).…”

“…In the E7b and E8 Zones (Sj.8-Sj.13 interval), the smectite content is very high and almost constant with a maximum equal of 86.93% in Sj.10 sample corresponding to the top of the E7b Zone, but we find a slight drop at Sj.12 precisely at the limit between E7b/E8, where we find a remarkably sharp spike in kaolinite of 22%. However, in the Gorrondatxe section, clay minerals rates decrease in this interval (Payros et al, 2012). The abundance of smectite indicates a subtropical to tropical origin where the rainfall was very low and the landforms were low; it would also indicate a high marine sea level and therefore a marine transgression (Millot, 1970;Robert and Kennett, 1992;Jamoussi et al, 2003).…”