TY - JOUR

T1 - Transient and secular changes in global carbon cycling during the early Bajocian event

T2 - Evidence for Jurassic cool climate episodes

AU - Bodin, Stéphane

AU - Malte, Mau

AU - Sadki, Driss

AU - Danisch, Jan

AU - Nutz, Alexis

AU - Krencker, Francois-Nicolas Frédéric

AU - Kabiri, Lahcen

N1 - Funding information: This research was financed by the Aarhus Universitets Forskningsfond (grant n° AUFF-E-2015-FLS-8-77 ) and the Independent Research Fund Denmark (DFF, grant n° 9040-00188B ). We thank Alicia Fantasia for fruitful discussion, as well as the two anonymous reviewers and Howard Falcon-Lang, whose constructive comments helped to improve this manuscript. This research was financed by the Aarhus Universitets Forskningsfond (grant n? AUFF-E-2015-FLS-8-77) and the Independent Research Fund Denmark (DFF, grant n? 9040-00188B). We thank Alicia Fantasia for fruitful discussion, as well as the two anonymous reviewers and Howard Falcon-Lang, whose constructive comments helped to improve this manuscript. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

PY - 2020/11

Y1 - 2020/11

N2 - The early Bajocian event was characterized by a protracted, ca. 4 Myr-long positive carbon isotope excursion that has been recognized in both marine and continental records. It is concomitant with a marine eutrophication event that led to regional demises of the neritic carbonate factory, as well as floral and faunal turnovers. The ultimate cause and modality of this event remains uncertain. In this study, we present a high-resolution, biostratigraphically calibrated, bulk organic matter carbon isotope dataset derived from the marine sedimentary record of the Central High Atlas Basin in Morocco and spanning the upper Aalenian–lower upper Bajocian. Within the context of the overall lower Bajocian positive carbon isotope excursion, this curve displays a complex trend of subordinated positive and negative shifts, which can be correlated to the high-resolution bulk carbonate carbon isotope record of southeastern France and southern Spain. The presence of a similar complex shape in these carbon isotope records over a large paleogeographic area highlights that the carbon cycle perturbation associated with the early Bajocian event was more intricate than previously depicted. Using the difference in carbon isotope fractionation between the carbonate and organic matter records as a first-order tracer of atmospheric pCO 2 variations implies that the late early Bajocian was characterized by two interludes (late Propinquans and late Humphriesianum chronozones) of low greenhouse gas concentrations. This inference is supported by high-resolution paleotemperature and global sea-level records, suggesting the transient development of polar ice caps during the Middle Jurassic.

AB - The early Bajocian event was characterized by a protracted, ca. 4 Myr-long positive carbon isotope excursion that has been recognized in both marine and continental records. It is concomitant with a marine eutrophication event that led to regional demises of the neritic carbonate factory, as well as floral and faunal turnovers. The ultimate cause and modality of this event remains uncertain. In this study, we present a high-resolution, biostratigraphically calibrated, bulk organic matter carbon isotope dataset derived from the marine sedimentary record of the Central High Atlas Basin in Morocco and spanning the upper Aalenian–lower upper Bajocian. Within the context of the overall lower Bajocian positive carbon isotope excursion, this curve displays a complex trend of subordinated positive and negative shifts, which can be correlated to the high-resolution bulk carbonate carbon isotope record of southeastern France and southern Spain. The presence of a similar complex shape in these carbon isotope records over a large paleogeographic area highlights that the carbon cycle perturbation associated with the early Bajocian event was more intricate than previously depicted. Using the difference in carbon isotope fractionation between the carbonate and organic matter records as a first-order tracer of atmospheric pCO 2 variations implies that the late early Bajocian was characterized by two interludes (late Propinquans and late Humphriesianum chronozones) of low greenhouse gas concentrations. This inference is supported by high-resolution paleotemperature and global sea-level records, suggesting the transient development of polar ice caps during the Middle Jurassic.

KW - Atmospheric pCO

KW - Carbon isotopes

KW - Central High Atlas Basin

KW - Middle Jurassic

KW - Morocco

KW - Organic matter

UR - http://www.scopus.com/inward/record.url?scp=85089245345&partnerID=8YFLogxK

U2 - 10.1016/j.gloplacha.2020.103287

DO - 10.1016/j.gloplacha.2020.103287

M3 - Article

VL - 194

JO - Global and Planetary Change

JF - Global and Planetary Change

SN - 0921-8181

M1 - 103287

ER -