TY - JOUR

T1 - Neritic Carbonate Crisis During the Early Bajocian: Divergent Responses to a Global Environmental Perturbation

AU - Bodin, Stéphane

AU - Hönig, Martin

AU - Krencker, Francois-Nicolas Frédéric

AU - Danisch, Jan

AU - Kabiri, Lahcen

N1 - Funding information: This research was financed by the Deutsche Forschungsgemeinschaft (DFG, project no. BO 3655/1). Analytical work in the isotope laboratory at Bochum was supported by Andreas Hollweg, Tim Kothe, Beate Gehen, Katrin Schauerte and Andrea Niedermayr. We warmly thank Nicolas Christ for providing materials and advices on the Assoul Formation, as well as Volker Dietze and Sixto Rafael Fernandez-Lopez for their help with regard to Bajocian ammonites biochronostratigraphical range. This manuscript benefited from the review of Baptiste Suchéras-Marx and Alexis Godet, as well as the editorial comments of Thomas Algeo.

PY - 2017

Y1 - 2017

N2 - The Early Bajocian witnessed a global environmental perturbation, characterized by faunal and floral turnovers and a positive carbon isotope excursion. In Italy, this environmental perturbation coincided with an eutrophication event and a carbonate crisis, but this has so far not been adequately reported from other settings, leaving doubt about the extent and nature of these phenomena. In this paper, we are reporting on an extensive neritic carbonate factory demise that occurs in the upper Lower Bajocian of Morocco, more precisely in the upper Propinquans – lower Humphriesianum Zones. This demise coincided with the acme of the global carbon isotope perturbation, recorded by a 3‰ positive carbon isotope excursion in the bulk organic matter of Morocco, but not in the micritic phase, due to the fact that the Moroccan carbonate δ 13C record is more sensitive to local rather than global influences. Furthermore, we observe that the Lower Bajocian of Morocco is relatively enriched in arenitic siliciclastic deposits, suggesting increased weathering and nutrient levels along the northwestern margin of Africa during the Early Bajocian. However, comparison with neighboring European basins highlights the non-uniqueness and different timing of the response of shallow-water carbonates to the Early Bajocian environmental perturbations, as some regions present no sign of carbonate factory crisis. Hence, we postulate that local factors were important in mediating the response of neritic carbonate factories to this global environmental perturbation. We notably highlight the role of large Early Bajocian sea-level fluctuation as a trigger for carbonate factory change and demise in Morocco.

AB - The Early Bajocian witnessed a global environmental perturbation, characterized by faunal and floral turnovers and a positive carbon isotope excursion. In Italy, this environmental perturbation coincided with an eutrophication event and a carbonate crisis, but this has so far not been adequately reported from other settings, leaving doubt about the extent and nature of these phenomena. In this paper, we are reporting on an extensive neritic carbonate factory demise that occurs in the upper Lower Bajocian of Morocco, more precisely in the upper Propinquans – lower Humphriesianum Zones. This demise coincided with the acme of the global carbon isotope perturbation, recorded by a 3‰ positive carbon isotope excursion in the bulk organic matter of Morocco, but not in the micritic phase, due to the fact that the Moroccan carbonate δ 13C record is more sensitive to local rather than global influences. Furthermore, we observe that the Lower Bajocian of Morocco is relatively enriched in arenitic siliciclastic deposits, suggesting increased weathering and nutrient levels along the northwestern margin of Africa during the Early Bajocian. However, comparison with neighboring European basins highlights the non-uniqueness and different timing of the response of shallow-water carbonates to the Early Bajocian environmental perturbations, as some regions present no sign of carbonate factory crisis. Hence, we postulate that local factors were important in mediating the response of neritic carbonate factories to this global environmental perturbation. We notably highlight the role of large Early Bajocian sea-level fluctuation as a trigger for carbonate factory change and demise in Morocco.

KW - Carbon isotopes

KW - Drowning

KW - High Atlas

KW - Jurassic

KW - Morocco

UR - http://www.scopus.com/inward/record.url?scp=85006421211&partnerID=8YFLogxK

U2 - 10.1016/j.palaeo.2016.12.017

DO - 10.1016/j.palaeo.2016.12.017

M3 - Article

VL - 468

SP - 184

EP - 199

JO - Palaeogeography, Palaeoclimatology, Palaeoecology

JF - Palaeogeography, Palaeoclimatology, Palaeoecology

SN - 0031-0182

ER -