TY - JOUR

T1 - Two-phased collapse of the shallow-water carbonate factory during the late Pliensbachian–Toarcian driven by changing climate and enhanced continental weathering in the North-western Gondwana Margin

AU - Krencker, Francois-Nicolas Frédéric

AU - Fantasia, Alicia

AU - Danisch, Jan

AU - Martindale, Rowan

AU - Kabiri, Lahcen

AU - El Ouali, Mohamed

AU - Bodin, Stéphane

N1 - Funding information: This research was financed by the Deutsche Forschungsgemeinschaft (DFG , project n° BO 3655/1-1 ), Bochum University, Germany, granted to Stéphane Bodin (SB) and the Aarhus Universitets Forskningsfond (grant n° AUFF-E-2015-FLS-8-77 ), Aarhus University, Denmark, granted to Stéphane Bodin (SB), as well as the NSF EAR Grant # 1848393 , The University of Texas Austin, United States, granted to Rowan Martindale (RCM). Alexis Nutz, Laura Henkel, Martin Hönig, Tim Kothe, Nick Ettinger, Hannah Brame, Sean Kacur, and Mickaël Charpentier are thanked for their help during field expeditions and for laboratory work at Bochum and Aarhus. We are grateful to Editor Alessandra Negri and Jean-François Deconinck and an anonymous reviewer for their constructive comments and suggestions on this manuscript. The authors would like to dedicate this study to the memory of the late Professor Karl Föllmi. This research was financed by the Deutsche Forschungsgemeinschaft (DFG, project n? BO 3655/1-1), Bochum University, Germany, granted to St?phane Bodin (SB) and the Aarhus Universitets Forskningsfond (grant n? AUFF-E-2015-FLS-8-77), Aarhus University, Denmark, granted to St?phane Bodin (SB), as well as the NSF EAR Grant #1848393, The University of Texas Austin, United States, granted to Rowan Martindale (RCM). Alexis Nutz, Laura Henkel, Martin H?nig, Tim Kothe, Nick Ettinger, Hannah Brame, Sean Kacur, and Micka?l Charpentier are thanked for their help during field expeditions and for laboratory work at Bochum and Aarhus. We are grateful to Editor Alessandra Negri and Jean-Fran?ois Deconinck and an anonymous reviewer for their constructive comments and suggestions on this manuscript. The authors would like to dedicate this study to the memory of the late Professor Karl F?llmi.

PY - 2020/9

Y1 - 2020/9

N2 - The end Pliensbachian–Toarcian is characterized by several carbon-cycle perturbations and faunal turnovers (e.g., ammonites and foraminifera), which are most likely triggered by pulses of the Karoo-Ferrar-Chon Aike large igneous province. The majority of information about these events is based on detailed studies of sites deposited in deep-water settings, which leaves vast uncertainties about the expression of, and response to, these events in shallow-marine ecosystems. Here, we present a comprehensive assessment of paleoclimatic impacts on neritic depositional environments from the latest Pliensbachian through the middle Toarcian in the central High Atlas Basin, Morocco, and compare those with changes observed in coeval neritic environments within the western Tethyan realm. A total of four new stratigraphic sections were investigated in the southern part of central High Atlas Basin and these new sections are synthesized with six previously published sections, distributed over eight localities. Correlations between sections are based on biostratigraphy, chemostratigraphy and lithostratigraphy. In Morocco, two episodes of carbonate factory shutdown are observed, spanning the Pliensbachian/Toarcian boundary and the Polymorphum/Levisoni transition. Each carbonate factory collapse correlates to well-documented environmental disturbances during the latest Pliensbachian–middle Toarcian interval, including the Toarcian Oceanic Anoxic Event (T-OAE). Moreover, each episode of carbonate factory shutdown coincides with an interval characterized by a significant increase of coarse siliciclastic input in the basin, further demonstrating the link between global warming, increased continental weathering, and ecosystem turnovers. Furthermore, these two episodes of carbonate factory shutdown are each followed by episodes of renewed carbonate production, showing the resilience of the neritic carbonate factory in this region. The first recovery interval, occurring during the late Polymorphum Zone, is associated with a mixed siliciclastic‑carbonate system. The second episode of carbonate recovery quickly follows the shutdown associated with the onset of the T-OAE. It is associated with an abiotic-dominated carbonate production mode, resulting in an elevated ooid production. A full recovery of biotic carbonate production only occurs in the late stage of the T-OAE. Although biotic turnover occurs at both events, from a shallow-marine perspective, the major biotic and abiotic crisis occurred at the Pliensbachian/Toarcian boundary and not during the T-OAE. This is in contrast to the deep-marine record, where the T-OAE is often inferred to be the most significant event. An enhanced hydrological cycle and the subsequent increase of continental nutrient shedding might have triggered the most severe changes of the carbonate productivity at the Pliensbachian/Toarcian transition; whereas, ocean acidification and increased storm activity likely played a significant role at the onset of the T-OAE.

AB - The end Pliensbachian–Toarcian is characterized by several carbon-cycle perturbations and faunal turnovers (e.g., ammonites and foraminifera), which are most likely triggered by pulses of the Karoo-Ferrar-Chon Aike large igneous province. The majority of information about these events is based on detailed studies of sites deposited in deep-water settings, which leaves vast uncertainties about the expression of, and response to, these events in shallow-marine ecosystems. Here, we present a comprehensive assessment of paleoclimatic impacts on neritic depositional environments from the latest Pliensbachian through the middle Toarcian in the central High Atlas Basin, Morocco, and compare those with changes observed in coeval neritic environments within the western Tethyan realm. A total of four new stratigraphic sections were investigated in the southern part of central High Atlas Basin and these new sections are synthesized with six previously published sections, distributed over eight localities. Correlations between sections are based on biostratigraphy, chemostratigraphy and lithostratigraphy. In Morocco, two episodes of carbonate factory shutdown are observed, spanning the Pliensbachian/Toarcian boundary and the Polymorphum/Levisoni transition. Each carbonate factory collapse correlates to well-documented environmental disturbances during the latest Pliensbachian–middle Toarcian interval, including the Toarcian Oceanic Anoxic Event (T-OAE). Moreover, each episode of carbonate factory shutdown coincides with an interval characterized by a significant increase of coarse siliciclastic input in the basin, further demonstrating the link between global warming, increased continental weathering, and ecosystem turnovers. Furthermore, these two episodes of carbonate factory shutdown are each followed by episodes of renewed carbonate production, showing the resilience of the neritic carbonate factory in this region. The first recovery interval, occurring during the late Polymorphum Zone, is associated with a mixed siliciclastic‑carbonate system. The second episode of carbonate recovery quickly follows the shutdown associated with the onset of the T-OAE. It is associated with an abiotic-dominated carbonate production mode, resulting in an elevated ooid production. A full recovery of biotic carbonate production only occurs in the late stage of the T-OAE. Although biotic turnover occurs at both events, from a shallow-marine perspective, the major biotic and abiotic crisis occurred at the Pliensbachian/Toarcian boundary and not during the T-OAE. This is in contrast to the deep-marine record, where the T-OAE is often inferred to be the most significant event. An enhanced hydrological cycle and the subsequent increase of continental nutrient shedding might have triggered the most severe changes of the carbonate productivity at the Pliensbachian/Toarcian transition; whereas, ocean acidification and increased storm activity likely played a significant role at the onset of the T-OAE.

KW - Carbonate factory shutdown

KW - Early Jurassic

KW - Morocco

KW - Oceanic Anoxic Event

KW - Tethys Ocean

UR - http://www.scopus.com/inward/record.url?scp=85089818462&partnerID=8YFLogxK

U2 - 10.1016/j.earscirev.2020.103254

DO - 10.1016/j.earscirev.2020.103254

M3 - Article

VL - 208

JO - Earth-Science Reviews

JF - Earth-Science Reviews

SN - 0012-8252

M1 - 103254

ER -