25th International Meeting on Organic Geochemistry IMOG 2011

P-211
Paleocene-Eocene Thermal Maximum impacts on terrestrial
environments. Insights from the organic matter evolution in the
Vasterival section (Dieppe-Hampshire Basin, France)
Sylvain Garel 1 , Johann Schnyder 1 , Jérémy Jacob 2 , Mohammed Boussafir 2 , Christian
Dupuis 3 , Jean-Yves Storme 4 , Johan Yans, Alina Iakovleva 5 , Emile Roche 6 , Claude
LeMilbeau 2 , Florence Quesnel 7
1 ISTeP, Université P. & M. Curie, UMR 7193 du CNRS, Paris, France, 2 Institut des Sciences de la Terre
d'Orléans, ISTO, Université d'Orléans, UMR 6113 du CNRS/INSU, Orléans, France, 3 Service de Géologie
Fondamentale et Appliquée, Université de Mons, Mons, Belgium, 4 FUNDP, Département de Géologie,
Université de Namur, Namur, Belgium, 5 Geological Institute, Russian Academy of Sciences, Moscow,
Russian Federation, 6 Laboratoire de Paléontologie Végétale, Université de Liège, Liège, Belgium,
7 GEO/G2R, BRGM, Orléans, France (corresponding author:jeremy.jacob@univ-orleans.fr)
The Paleocene-Eocene Thermal Maximum (PETM,
55.8 Ma [1]) is regarded as one of the most rapid
global warming of the Cenozoic era, with temperature
increase of 4-8°C in about 10-20 ka [2]. Thus, it is
often proposed as a potential analogue of future
climatic conditions expected in the IPCC screenplays.
The PETM is recorded in both marine and continental
deposits by an abrupt negative Carbon Isotope
Excursion (CIE) associated with other sedimentary
and biological anomalies. The consequences of the
PETM on terrestrial environments are less
documented than in marine ones. This limits our
regional- and global-scale understanding of the
impact of such a climate change on continents and
the associated response of ecosystems.
This study focuses on the Vasterival section (Seine-
Maritime, Upper Normandy) located in the southern
part of the Dieppe-Hampshire Basin, in which the
PETM is attested by a negative δ 13 Corg shift in the
organic matter (OM), and confirmed by the
stratigraphic record in this locality belonging to the
Cap d‘Ailly composite section [3]. The 2 m thick
section, which presents a notably well preserved OM,
is mainly constituted by terrestrial sediments from
lacustrine to coastal swamp environments, and in
which OM-poor clays are followed by OM-rich clays,
centimetric lignite beds and clays with roots
evidences. The uppermost part of the section is
constituted by 50 cm thick lagoonal clay with shell
debris that records the Apectodinium acme.
Global organic geochemical, palynofacies and
isotopic analyses were performed on thirty samples.
The total organic carbon of this section is ranging
from 0.5 % for OM-poor-clays to 45 % for lignite levels.
Hydrogen Index (from 6 to 210 mg HC/g TOC),
Oxygen Index (from 80 to 630 mgCO2/g TOC) and
Tmax values (from 410 to 430°C) show that the OM is
of Type III (terrestrial higher plants), and immature.
These results are reinforced by palynofacies
observations that show a large amount of lignocellulosic
phytoclasts in most of the samples. In the
uppermost shale the presence of many Apectodinium
species would suggest the continuity of the PETM in
marine deposits. Thus, the continental deposits would
represent a time interval that includes the uppermost
Paleocene and the basal part of the PETM.
Lipid biomarkers extracted from twenty five samples
were quantified and their hydrogen and carbon
isotopic composition were determined by GC-irMS.
Important changes in palynofacies, biomarker
assemblages and compound-specific isotopic data
are coincident with the CIE onset interval. This is
consistent with an important environmental
modification in the Vasterival area during the Early
Eocene that could be linked to the PETM climatic
change.
References
[1] Aubry, M. P., Ouda, K., Dupuis, C ., Berggren, W.
A., Van Couvering, J A., and the Members of the
Working Group on the Paleocene/Eocene Boundary,
2007. The Global Standard Stratotype-section and
Point (GSSP) for the base of the Eocene Series in the
Dababiya section (Egypt). Episodes 30 (4): 271-286.
[2] Zachos, J. C., Pagany, N., Sloan, L., Thomas, E.,
Billups, K., 2001. Trends, rythms, and aberrations in
global climate 65 Ma to Present. Science 292: 686–
693.
[3] Dupuis, C., Steurbaut, E., De Coninck, J. and
Riveline, J., 1998. The Western Argiles à Lignites
facies. In: M. Thiry and C. Dupuis (Eds.), The
Paleocene/Eocene boundary in Paris basin: the
Sparnacian deposits. Field trip guide. ENSMP Mém.
Sc. De la Terre, 34, 60-71.
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