Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): Implications for defining the Ypresian/Lutetian boundary stratotype

Abstract

. 2008: Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): Implications for defining the Ypresian/Lutetian boundary stratotype. Lethaia , Vol. 41, In this paper, we present an integrated study of a 115-m-thick section that spans the Ypresian/Lutetian boundary at Agost (Betic Cordillera, SE Spain). Our study includes magnetostratigraphic results and biostratigraphic and palaeoenvironmental data derived from planktic foraminifera, small and larger benthic foraminifera, and calcareous nannofossils. Our results demonstrate that the Agost section is continuous and spans from Zones P9 to P12 (E7 to E10), Zones CP11 to CP14a (NP13 to NP16), Zones SBZ11 to SBZ15, and Chrons C22n to C19r. The first occurrence (FO) of H. nuttalli (base of P10) and the FO of G. nuttalli (base of E8) are found within Chron C20r, at a much younger age (3-5 Myr) than previously considered in standard calibration schemes. Similarly, the boundary between SBZ12 and SBZ13 is located within Chron C21n, also at a younger age than previously considered. On the contrary, the FO of B. inflatus (base of CP12b) is found within Chron C21r, which conforms to the magnetostratigraphically calibrated age of ca. 48 Ma (middle part of C21r) considered in standard calibration schemes. These results corroborate earlier studies and indicate that all the events that have been proposed to mark the Ypresian/Lutetian boundary appear at different stratigraphic intervals and have different ages. Based on our results from Agost and on data from other sections elsewhere, we suggest that the Ypresian/Lutetian boundary might be approximated by the FO of B. inflatus (base of CP12b). The Agost section might be considered as a potential candidate to locate the Global Stratotype Section and Point (GSSP) of the base of the Lutetian Stage, because it includes all the events that might be selected as marker events for the Ypresian/Lutetian boundary and it fulfils most of the geological, biostratigraphic and infrastructure requirements demanded for definition of a GSSP. ᮀ Agost , Betic Cordillera , biostratigraphy , calcareous nannofossils , Global Stratotype Section and Point , larger benthic foraminifera , magnetostratigraphy , planktic foraminifera , small benthic foraminifera , Ypresian/ Lutetian boundary .

Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale

“…The P9/P10 zonal boundary is therefore a surprising 3.1 myr younger than in BKSA95. The significantly younger calibrations for the LO of Hantkenina and Guembelitrioides nuttalli are also confirmed by Ortiz et al (2008) and Larrasoaña et al (2008) from the Agost Section in Spain. Payros et al (2007) used the time scale, here we recalibrate the FAD of Globigerinatheka kugleri, Hantkenina singanoae, Guembelitrioides nuttalli and Turborotalia frontosa to Cande and Kent (1995), resulting in FADs of 44.4,44.5,46.4 and 49 Ma,respectively (Figs.…”

“…The enhancements in deep sea drilling recovery, multiple coring, high resolution sampling both offshore and onshore, has improved the calibrations with the magnetostratigraphy and/or modified the species ranges and allowed many of the planktonic foraminiferal bioevents to be revised. For example, detailed biostratigraphic investigations from Ceara Rise Pearson and Chaisson, 1997;Turco et al, 2002), equatorial Pacific Ocean (Wade et al, 2007), Indian Ocean (Hancock et al, 2002) and the Gorrondaxte and Agost sections in Spain (Payros et al, , 2009Larrasoaña et al, 2008;Ortiz et al, 2008) have resulted in revision of the calibrations of numerous bioevents. Most of these changes are small and incremental in nature, but some (e.g., the revision of the lower-middle Eocene by Payros et al, 2007) are major developments.…”

On the age of the Early/Middle Eocene boundary and other related events: cyclostratigraphic refinements from the Pyrenean Otsakar section and the Lutetian GSSP

“…The first occurrence of D. sublodoensis, which marks the base of Zone CP12a was found at 41 m. However, transitional forms between D. lodoensis and D. sublodoensis were found between 32 and 41 m. Similar specimens were found in Gorrondatxe between the first rare occurrence of D. sublodoensis and its common occurrence higher in the succession , suggesting that in Otsakar the CP11/12a boundary could actually be located somewhere between 32 and 41 m. A similar trend in the abundance of D. sublodoensis was also observed in other sections (Agnini et al 2006;Larrasoaña et al 2008). …”

“…This suggests that Zone CP13a is not represented in the Otsakar section, as the last occurrence of B. inflatus can be used to approach the base of Zone CP13a (Aubry, 1983;Varol, 1989;Bernaola et al 2006;Larrasoaña et al 2008). From this level upwards B. inflatus was found in all samples.…”

Deep-Water Benthic Foraminifers from the Paleocene and Eocene of the North Pacific Region: Paleontology, Biostratigraphy, and Paleoceanological Reconstructions

“…16). It is possible that this warming episode corresponds to the Middle Lutetian hyperthermal recorded in the pelagial of the western Mediterranean and Austrian Alps and in the Crimea Caucasian region (Ortiz et al, 2008;Larrasoaña et al, 2008;Egger, 2010, 2011;Zakrevskaya et al, 2011;.…”