TY - JOUR
T1 - Multiple early Eocene carbon isotope excursions associated with environmental changes in the Dieppe-Hampshire Basin (NW Europe)
AU - Garel, Sylvain
AU - Dupuis, Christian
AU - Quesnel, Florence
AU - Jacob, Jérémy
AU - Yans, Johan
AU - Magioncalda, Roberto
AU - Fléhoc, Christine
AU - Schnyder, Johann
N1 - Funding Information:
Acknowledgements. S.G. thanks the French “Ministère de l’Enseignement Supérieur et de la Recherche” for a Doctoral grant. We wish to thank Florence Savignac (Sorbonne Université) for her technical support, Jean-Yves Storme for scientific discussion, Hervé Guillou for K-Ar analyses and Elizabeth Rowley-Jolivet for English revision. We also thank Vittoria Lauretano and an anonymous reviewer for their comments and reviews, which considerably improved the manuscript. This paper is a contribution to the Research cooperation contract financially supported by the BRGM (“Paléosurface éocène – PETM” research project) and to the BRGM Scientific Programs “Genèse et caractéristiques des Régolithes” and “Référentiel Géologique de la France”. The work was part of the PalHydroMil project, supported by Agence Nationale de la Recherche Grant ANR-2010-JCJC-607-01. J.Y. thanks the Belgian Science Policy Office, project 688 BR/121/A3/PALEURAFRICA.
Publisher Copyright:
© S. Garel.
PY - 2020
Y1 - 2020
N2 - The early Eocene experienced a series of short-lived global warming events, known as hyperthermals, associated with negative carbon isotope excursions (CIE). The Paleocene-Eocene Thermal Maximum (PETM or ETM-1) and Eocene Thermal Maximum 2 (ETM-2) are the two main events of this Epoch, both marked by massive sea-floor carbonate dissolution. Their timing, amplitude and impacts are rather well documented, but CIEs with lower amplitudes also associated with carbonate dissolution are still poorly studied (e.g. events E1 to H1), especially in the terrestrial realm where hiatus/disconformities and various sedimentary rates in a single succession may complicate the assignation to global isotopic events. Here we present a new high-resolution multi-proxy study on the terrestrial, lagoonal and shallow marine late Paleocene-early Eocene succession from two sites of the Cap d'Ailly area in the Dieppe-Hampshire Basin (Normandy, France). Carbon isotope data (δ13C) on bulk organic matter and higher-plant derived n-alkanes, and K-Ar ages on authigenic glauconite were determined to provide a stratigraphic framework. Palynofacies, distribution and hydrogen isotope values (δ2H) of higher-plant derived n-alkanes allowed us to unravel paleoenvironmental and paleoclimatic changes. In coastal sediments of the Cap d'Ailly area, δ13C values revealed two main negative CIEs, from base to top CIE1 and CIE2, and 3 less pronounced negative excursions older than the NP11 nannofossil biozone. While the CIE1 is clearly linked with the PETM initiation, the CIE2 could either correspond to 1) a second excursion within the PETM interval caused by strong local environmental changes or 2) a global carbon isotopic event that occurred between the PETM and ETM-2. Paleoenvironmental data indicated that both main CIEs were associated with dramatic changes such as eutrophication, algal and/or dinoflagellate blooms along with paleohydrological variations and an increase in seasonality. They revealed that the intervals immediately below these CIEs are also marked by environmental and climatic changes. Thus, this study shows either 1) a PETM marked by at least two distinct intervals of strong environmental and climatic changes or 2) at least one "minor"CIE: E1, E2, F or G, was associated with strong environmental and climatic changes similar to those that occurred during the PETM.
AB - The early Eocene experienced a series of short-lived global warming events, known as hyperthermals, associated with negative carbon isotope excursions (CIE). The Paleocene-Eocene Thermal Maximum (PETM or ETM-1) and Eocene Thermal Maximum 2 (ETM-2) are the two main events of this Epoch, both marked by massive sea-floor carbonate dissolution. Their timing, amplitude and impacts are rather well documented, but CIEs with lower amplitudes also associated with carbonate dissolution are still poorly studied (e.g. events E1 to H1), especially in the terrestrial realm where hiatus/disconformities and various sedimentary rates in a single succession may complicate the assignation to global isotopic events. Here we present a new high-resolution multi-proxy study on the terrestrial, lagoonal and shallow marine late Paleocene-early Eocene succession from two sites of the Cap d'Ailly area in the Dieppe-Hampshire Basin (Normandy, France). Carbon isotope data (δ13C) on bulk organic matter and higher-plant derived n-alkanes, and K-Ar ages on authigenic glauconite were determined to provide a stratigraphic framework. Palynofacies, distribution and hydrogen isotope values (δ2H) of higher-plant derived n-alkanes allowed us to unravel paleoenvironmental and paleoclimatic changes. In coastal sediments of the Cap d'Ailly area, δ13C values revealed two main negative CIEs, from base to top CIE1 and CIE2, and 3 less pronounced negative excursions older than the NP11 nannofossil biozone. While the CIE1 is clearly linked with the PETM initiation, the CIE2 could either correspond to 1) a second excursion within the PETM interval caused by strong local environmental changes or 2) a global carbon isotopic event that occurred between the PETM and ETM-2. Paleoenvironmental data indicated that both main CIEs were associated with dramatic changes such as eutrophication, algal and/or dinoflagellate blooms along with paleohydrological variations and an increase in seasonality. They revealed that the intervals immediately below these CIEs are also marked by environmental and climatic changes. Thus, this study shows either 1) a PETM marked by at least two distinct intervals of strong environmental and climatic changes or 2) at least one "minor"CIE: E1, E2, F or G, was associated with strong environmental and climatic changes similar to those that occurred during the PETM.
KW - Carbon isotope excursions
KW - Dieppe-Hampshire Basin
KW - Early Eocene
KW - Paleohydrology
KW - Palynofacies
KW - PETM
UR - http://www.scopus.com/inward/record.url?scp=85096052909&partnerID=8YFLogxK
U2 - 10.1051/bsgf/2020030
DO - 10.1051/bsgf/2020030
M3 - Article
AN - SCOPUS:85096052909
SN - 0037-9409
VL - 191
JO - Bulletin de la Société Géologique de France
JF - Bulletin de la Société Géologique de France
M1 - 2020030
ER -