TY - JOUR

T1 - Carbon-isotope events during the pliensbachian (Lower jurassic) on the African and European margins of the nw tethyan realm

AU - Mercuzot, Mathilde

AU - Pellenard, Pierre

AU - Durlet, Christophe

AU - Bougeault, Cedric

AU - Meister, Christian

AU - Dommergues, Jean Louis

AU - Thibault, Nicolas

AU - Baudin, Frangois

AU - Mathieu, Olivier

AU - Bruneau, Ludovic

AU - Huret, Emilia

AU - El Hmidi, Khalid

PY - 2020

Y1 - 2020

N2 - Early Jurassic palaeoenvironments and palaeoclimates, based on chemostratigraphy, have been extensively studied for the northern Tethyan margin. For the first time, high-resolution chemostratigraphy for the entire Pliensbachian is proposed for the African Tethyan margin (Morocco), and compared with new sections from the European Tethyan margin (France). Precise ammonite determinations, completed by calcareous nannofossil distribution, provide an accurate biostratigraphic framework from the Upper Sinemurian to the Upper Pliensbachian. Bulk inorganic carbon (S13Ccarb) and organic carbon (S13Corg) isotope signals are used to characterise and compare carbon-cycle trends in the Central High Atlas Basin (Amellago-Ikis section, Morocco), the Paris Basin (Montcornet borehole, France), and the Subalpine Basin (Serre-Pongon section, France). Comparison of this new dataset with previously published geochemical data from European basins confirms the existence of five distinct carbon-isotope events, synchronous at the scale of the NW Tethyan Realm: (1) a clear -2%o negative excursion of 513Ccarb and 513Corg, corresponding to the Sinemurian-Pliensbachian Boundary Event (SPBE), probably associated with a massive release of light carbon by volcanism and hydrothermalism during the breakup of Pangea; (2) a positive excursion (+ 1 to + 1.5%o) in the Valdani and Luridum subzones (Ibex Zone), reflecting increased organic matter storage under warm climate conditions; (3) a broadly negative event from the Davoei Zone to the lower part of the Margaritatus Zone, associated with major oceanographic reorganisation in a transgressive context, and possible enhanced hydrothermalism related to the opening of the Hispanic corridor; (4) a positive carbon excursion (+2%o) during the Subnodosus and Gibbosus subzones (Margaritatus Zone), corresponding to the Late Pliensbachian Event (LPE), associated with organic matter storage; (5) an end-Margaritatus-Spinatum negative excursion, associated with sea-level fall, probably driven by glacio-eustasy. This new high-resolution carbon-isotope dataset highlights the synchroneity of carbon-cycle trends throughout the NW Tethyan Realm. Several major isotopic events, prior to those of the Toarcian, must therefore have occurred at a supra-regional to global scale during the Pliensbachian, involving significant internal and external geodynamic mechanisms.

AB - Early Jurassic palaeoenvironments and palaeoclimates, based on chemostratigraphy, have been extensively studied for the northern Tethyan margin. For the first time, high-resolution chemostratigraphy for the entire Pliensbachian is proposed for the African Tethyan margin (Morocco), and compared with new sections from the European Tethyan margin (France). Precise ammonite determinations, completed by calcareous nannofossil distribution, provide an accurate biostratigraphic framework from the Upper Sinemurian to the Upper Pliensbachian. Bulk inorganic carbon (S13Ccarb) and organic carbon (S13Corg) isotope signals are used to characterise and compare carbon-cycle trends in the Central High Atlas Basin (Amellago-Ikis section, Morocco), the Paris Basin (Montcornet borehole, France), and the Subalpine Basin (Serre-Pongon section, France). Comparison of this new dataset with previously published geochemical data from European basins confirms the existence of five distinct carbon-isotope events, synchronous at the scale of the NW Tethyan Realm: (1) a clear -2%o negative excursion of 513Ccarb and 513Corg, corresponding to the Sinemurian-Pliensbachian Boundary Event (SPBE), probably associated with a massive release of light carbon by volcanism and hydrothermalism during the breakup of Pangea; (2) a positive excursion (+ 1 to + 1.5%o) in the Valdani and Luridum subzones (Ibex Zone), reflecting increased organic matter storage under warm climate conditions; (3) a broadly negative event from the Davoei Zone to the lower part of the Margaritatus Zone, associated with major oceanographic reorganisation in a transgressive context, and possible enhanced hydrothermalism related to the opening of the Hispanic corridor; (4) a positive carbon excursion (+2%o) during the Subnodosus and Gibbosus subzones (Margaritatus Zone), corresponding to the Late Pliensbachian Event (LPE), associated with organic matter storage; (5) an end-Margaritatus-Spinatum negative excursion, associated with sea-level fall, probably driven by glacio-eustasy. This new high-resolution carbon-isotope dataset highlights the synchroneity of carbon-cycle trends throughout the NW Tethyan Realm. Several major isotopic events, prior to those of the Toarcian, must therefore have occurred at a supra-regional to global scale during the Pliensbachian, involving significant internal and external geodynamic mechanisms.

KW - Ammonite biostratigraphy

KW - Carbon-isotope excursion (CIE)

KW - Chemostrati-graphy

KW - Early Jurassic

KW - Pliensbachian

KW - Tethyan margins

U2 - 10.1127/nos/2019/0502

DO - 10.1127/nos/2019/0502

M3 - Journal article

AN - SCOPUS:85079322860

VL - 53

SP - 41

EP - 69

JO - Newsletters on Stratigraphy

JF - Newsletters on Stratigraphy

SN - 0078-0421

IS - 1

ER -