Comptes Rendus Géoscience

Clément Poirier

Cyril Poitevin

Éric Chaumillon

Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500

Benoît Issautier

Sophie Viseur

Pascal Audigane

Christophe Chiaberge

Yves-Michel Le Nindre

Handled by Sylvie Bourquin

A new approach for evaluating the impact of fluvial type heterogeneity in CO<sub>2</sub> storage reservoir modeling

Luca Pandolfi

Michele Marroni

Alessandro Malasoma

Handled by Isabelle Manighetti

Stratigraphic and structural features of the Bas Ostriconi Unit (Corsica): Palaeogeographic implications

Iliana Aguilar

Christian Beck

Franck Audemard

Anne-Lise Develle

Mohammed Boussafir

Corina Campos

Christian Crouzet

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C. R. Geoscience 348 (2016) 1–2
http
163eword
om past to current tectonics: Thematic issue dedicated to
an-François Stéphan (1949–2013)
This thematic issue of Comptes rendus Geoscience has
n assembled to honor the memory of our late colleague
 friend Jean-François Stéphan. Jean-François was a
at scientist, specialized in tectonics, and a great
eague who devoted his time for his community. His
rk and actions deeply imprinted both the French and the
rnational Earth Science communities. This volume
gs together contributions of colleagues of Jean-
nçois, who were also close friends or colleagues who
w and deeply appreciated him. Naturally, tectonics is
 common theme of these contributions. Some of the
ers presented here focus on tectonic questions and/or
ions Jean-François worked on during his career; other
ers present studies Jean-François motivated or encour-
d in one way or another; other papers are simply
tonic studies he would have liked. Taken together, the
e papers of this thematic issue take the reader on a
utiful trip, from past to current tectonics.
The first three papers revisit the subduction factories
t were operating in Eurasia in Triassic to Cretaceous
es. Faure et al. (2016) analyze the Triassic tectonic
tures that form the southern margin of the South China
ck, and show from lithostratigraphic, structural and
onological evidence that the South China Block sub-
ted southward below the Qiangtang–Indochina block,
in opposite direction to the common vision. The
thward subduction was coeval with the intraconti-
tal subduction well documented in South-East China.
se results therefore provide a new vision of the Triassic
ductions in China. The papers by Chorowicz (2016) and
son et al. (2016) then take the readers further west, in
ope and adjacent regions. Based on lithostratigraphic
 tectonic analyses, Chorowicz (2016) shows that the
sent Pieniny Klippen Belt in the Carpathians formed
inally along a large north–south transform fault that
 the Neotethys domain from Permian to Early Paleo-
e. The transform fault was likely separating the
ninic and Insubric Oceans in the west from the
Carpathian Embayment and the Vardar oceans in the east.
Its transcurrent motion allowed subductions and obduc-
tions to operate with reverse vergence north and south of
the Neotethys. Sosson et al. (2016) provide additional
information on the Neotethys, in its prolongation further
east, in the Eastern Black Sea-Caucasus region. From new
stratigraphic, tectonic, and petrologic data acquired on
ophiolitic units in the zone, they show that an intra-
oceanic northward subduction was operating within the
Neotethys during the Cretaceous. When the spreading
center of the back-arc basin created by this intra-oceanic
subduction was carried into general subduction below
Eurasia, it opened a window into the slab that weakened
the overlying Eurasia plate. The plate weakening in turn
favored the opening of the Black Sea. The paper thus shows
how the Neotethys subduction factory resulted in produc-
ing some of the major tectonic elements of the Southern
Eurasia plate.
The next paper, by Rangin (2016), examines the
subduction process at a more focused scale, that of the
active margins where two convergent plates are in contact.
Rangin (2016) takes the reader to Asia again and, based on
tectonic data, analyzes the zones of micro-plates that have
formed the active margins in the Philippines, Andaman
Sea, and Burma regions during the Cenozoic. The
Philippines and Andaman Sea margins are shown to have
deformed in a fairly rigid manner, whereas the Burma
margin attests to a non-rigid behavior. The work thus
opens questions on which large-scale mechanisms might
control the mechanical behavior of subduction margins.
The following paper by Calais et al. (2016) keeps the
focus on subduction zones, but now examines how a
typical frontal subduction – that in Lesser Antilles,
transitions to strike-slip fault zones on its lateral edges.
Combining current GPS and long-term geological data, the
authors show that the Caribbean–North American plate
boundary is segmented laterally from frontal subduction in
the east, to oblique subduction with no strain partitioning
Contents lists available at ScienceDirect
Comptes Rendus Geoscience
ww w.s c ien c edi r ec t . c om
://dx.doi.org/10.1016/j.crte.2015.11.0031-0713/ 2015 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Foreword / C. R. Geoscience 348 (2016) 1–22in the center (Puerto Rico), to oblique subduction/collision
with strain partitioning further west (Hispaniola). The
segmentation of the plate boundary is shown to arise from
its Neogene tectonic history, which highlights the control
of the long-term plate boundary properties onto current
deformation, including earthquakes and inter-seismic
loading.
The next two papers consider faults in general and
examine some of their fundamental properties. Perrin et al.
(2016) analyze the surface traces of about 50 continental
faults spanning a broad range of lengths, ages, and slip
modes, and whose direction of long-term lengthening is
known. They show that, independently of the parent fault
size and slip mode, networks of splay faults are systemati-
cally observed off the propagating fault tips, where they
have a length and a map-view width systematically scaled
to the parent fault’s length. The genetic and generic tip
splay networks are discussed in terms of permanent
damage resulting from fault growth. Chemenda et al.
(2016) provide a numerical model describing the 3-D
formation and evolution of a strike-slip fault in an
elastoplastic medium. The model reveals the development
of a wide and deep damage zone adjacent to the parent
fault, with a flower-type geometry in the vertical plane.
The details of the fault and damage evolution are revealed,
which provides important insights into the understanding
of natural faulting. In particular, the fault evolves as a
complex 3-D fault zone including different segments, and
damage widens rapidly as the fault grows, both away from
its trace and from surface to depth.
The next paper by Aguilar et al. (2016) keeps the reader
on strike-slip faults, and more specifically focuses on the El
Pilar dextral fault in Venezuela. The question is to examine
whether large prehistorical earthquakes on this fault have
significantly disturbed sedimentation in the Gulf of
Cariaco. Based on various sedimentary analyses of twelve
short cores extracted in the Gulf, the authors find evidence
of a widespread fine-grained siliciclastic deposit within
the Gulf, whose age suggests that it likely formed during
the large 1853 AD earthquake on the fault. It is proposed
that the earthquake induced large submarine landslides
that modified the topography of the Gulf entrance, which
in turn promoted upwelling and open marine water flows
from the Cariaco Basin, presently attested to by the
observed siliciclastic deposit.
Finally, Masse and Laurent (2016) take the reader to
the present time, and place him/her at the boundary
between geology and tectonics, history of geological
sciences, and exploitation of natural resources. The
authors show how geological studies have progressed
over the last century in Angola, and how this progress has
been fed both by mining and petroleum companies
interested in the local resources, and by the passion of
scientists that were also explorers.
Altogether the nine papers brought together in this
issue provide important new insights into some of the
most important tectonic features: subduction zones,
continental (especially strike-slip) faults, large earthqua-
kes, and interseismic deformation. In doing so, they render
a tribute to Jean-François Stéphan, who worked on all these
topics, with constant passion and creativity.
References
Aguilar, I., Beck, C., Audemard, F., Develle, A.-L., Boussafir, M., Campos, C.,
Crouzet, C., 2016. Last millenium sedimentation in the Gulf of Cariaco
(NE Venezuela): evidence for morphological changes of gulf entrance
and possible relations with large earthquakes. C. R. Geoscience 348,
(this issue).
Calais, E., Smythe, S., Mercier de Lépinay, B., Prépetit, C., 2016. Plate
boundary segmentation in the northeastern Caribbean from geodetic
measurements and Neogene geological observations. C. R. Geoscience
348, (this issue).
Chemenda, A.I., Cavalié, O., Vergnolle, M., Bouissou, S., Delouis, B., 2016.
Numerical model of formation of a 3-D strike-slip fault system. C. R.
Geoscience 348, (this issue).
Chorowicz, J., 2016. Genesis of the Pieniny Klippen Belt in the Carpa-
thians: possible effects of a major paleotransform fault in the Neo-
Tethyan domain. C. R. Geoscience 348, (this issue).
Faure, M., Lin, W., Chu, Y., 2016. Triassic tectonics of the southern margin
of the South Cjhina Block, 2016. C. R. Geoscience 348, (this issue).
Masse, P., Laurent, O., 2016. Geological exploration of Angola from Sumbe
to Namibe: a review at the frontier between geology, natural resour-
ces and the history of geology. C. R. Geoscience 348, (this issue).
Perrin, C., Manighetti, I., Gaudemer, Y., 2016. Off-fault tip splay networks:
a genetic and generic property of faults indicative of their long-term
propagation. C. R. Geoscience 348, (this issue).
Rangin, C., 2016. Rigid and non-rigid micro-plates: Philippines and
Myanmar-Andaman case studies. C. R. Geoscience 348, (this issue).
Sosson, M., Stephenson, R., Sheremet, Y., Rolland, Y., Adamia, S., Melko-
nian, R., Kangarli, T., Yegorova, T., Avagyan, A., Galoyan, G., Hässig, M.,
Danielan, T., Meijers, M., Müller, C., Sahakyan, L., Sadradze, N., Alania,
V., Enukidze, O., 2016. The eastern Black Sea–Caucasus region during
Cretaceous: new evidence to constrain its tectonic evolution. C. R.
Geoscience 348, (this issue).
Isabelle Manighetti
Université de Nice–Sophia Antipolis, Géoazur, bâtiment 4,
250, rue Albert-Einstein, 06560 Valbonne, France
E-mail address: manighetti@geoazur.unice.fr
Available online 17 December 2015


Last millennium sedimentation in the Gulf of Cariaco (NE Venezuela): Evidence for morphological changes of gulf entrance and possible relations with large earthquakes

Mohammad A. Kilzi

Michel Grégoire

Valérie Bosse

Mathieu Benoît

Youssef Driouch

Michel de Saint Blanquat

Pierre Debat

Handled by Marc Chaussidon

Geochemistry and zircon U–Pb geochronology of the ultramafic and mafic rocks emplaced within the anatectic series of the Variscan Pyrenees: The example of the Gavarnie–Heas dome (France)

Yves Lagabrielle

Camille Clerc

Alain Vauchez

Abdeltif Lahfid

Pierre Labaume

Bernard Azambre

Serge Fourcade

Jean-Marie Dautria

Very high geothermal gradient during mantle exhumation recorded in mylonitic marbles and carbonate breccias from a Mesozoic Pyrenean palaeomargin (Lherz area, North Pyrenean Zone, France)

Nathaelle Onanga Mavotchy

Abderrazak El Albani

Alain Trentesaux

Claude Fontaine

Anne-Catherine Pierson-Wickmann

Philippe Boulvais

Armelle Riboulleau

Lauriss Ngombi Pemba

Florent Pambo

François Gauthier-Lafaye

THE ROLE OF THE EARLY DIAGENETIC DOLOMITIC 
CONCRETIONS IN THE PRESERVATION OF THE 2.1 GA 
PAEOLENVIRONMENTAL SIGNAL: PALEOPROTEROZOIC OF 
THE FRANCEVILLE BASIN, GABON 
 
Nathaelle ONANGA MAVOTCHY, Abderrazak EL ALBANI*, Alain TRENTESAUX, 
Claude FONTAINE, Anne-Catherine PIERSON-WICKMANN, Philippe BOULVAIS, 
Armelle RIBOULLEAU, Lauriss NGOMBI PEMBA, Florent PAMBO, François 
GAUTHIER-LAFAYE 
 
*Corresponding author 
 
Supplementary material 
 
 
Supplementary information 
1- Geological setting 
The FA Formation is essentially formed of fluvial and deltaic sandstone deposits 
on top of which are located the well-known Oklo nuclear reactors (Gauthier-Lafaye and 
Weber, 1989; 2003; Gauthier-Lafaye et al., 1989). A transition from siliciclastic-
dominated fluvial-deltaic to marine sedimentation is systematically observed at the top of 
the FA Formation (Gauthier-Lafaye and Weber 2003; Préat et al., 2011).  
The FB unit consists of marine sediments deposited mainly below storm wave 
base. Because of its diverse lithological composition, the FB unit is further divided into 
the FB1 (a, b, and c) and FB2 (a and b) subunits. The FB1a and FB1b subunits consist of 
interlayered shales, sandstones, and conglomerates, fining upwards to predominantly 
shales at the top. The FB1c subunit mainly consists of shales, but also contains a thin iron 
formation overlain by black shales and a thick interval rich in manganese (Mn). The 
FB2a subunit consists of sandstone beds deposited in channels near the fair-weather wave 
base. These are sharply overlain by the FB2b subunit including finely-laminated black 
shales interbedded with thin siltstone layers deposited by waning storm surges. The 
previously reported large colonial organisms (El Albani et al., 2010, 2014), were 
collected from the FB2b black shales.  
 The overlying FC Unit is dominated by dolomites and stromatolitic cherts, 
indicating shallow-water conditions. Stromatolites are found on topographic highs at the 
base of the FC unit (Weber, 1968). The FD unit corresponds to black shales deposited 
during a transgressive phase (Canfield et al., 2013, Ngombi-Pemba et al., 2014). 
 
2-Materials and methods  
 Carbonate concretion samples were collected in the Moanda area. From polished 
sections, the concretions and surrounding black shales were characterised by optical 
microscopy and scanning electron microscopy (SEM). After carbon metallization, the 
samples were observed using the FEI Quanta 200 microscope from the UMR 8187 LOG 
CNRS-University of Lille, which is equipped with an EDS system and uses a Bruker 
Xflash 3001 detector associated to a Quantax software. Analytical conditions were an 
accelerating voltage of 15 kV and a working distance of 10 mm in backscattered or 
secondary electron mode. The global mineralogical composition of these samples was 
determined by X-ray diffraction (XRD) using the ANAlytical XpertPro diffractometer 
from the UMR 7285 IC2MP CNRS-University of Poitiers. Major, minor, trace and rare 
earth elements in bulk sediment were analyzed at the Service d’Analyse des Roches et 
des Minéraux facility of the Centre National de la Recherche Scientifique (Vandœuvre-
les-Nancy, France) using ICP-AES (major and minor elements) and ICP-MS (trace and 
rare earth elements) after fusion with LiBO2 and HNO3 dissolution. Precision and 
accuracy were better than 1% (mean 0.5%) for major and minor elements and better than 
5% for trace and rare earth elements, as checked by international standards and analysis 
of replicate samples (Carignan et al., 2001). Analyses of stable isotopes (δ13C, δ18O) were 
performed on 27 host rock and carbonate concretion samples. Carbonates were reacted 
with anhydrous phosphoric acid under thermostated conditions (50°C) until completion. 
The isotopic compositions were measured on a VG Optima triple collector mass 
spectrometer at the stable isotope laboratory from the UMR 6118 Géosciences Rennes 
CNRS-University of Rennes 1. The isotopic ratios are expressed in ‰ relative to the PDB 
(Belemnitella americana of Pee Dee Formation). The analytical uncertainty is ±0.2‰ for 
O, and ±0.1‰ for C; it was estimated using replicate analysis of some samples and 
reproducibility of international (NBS 19) and in-house (Prolabo Rennes) standarts. 
Samples for organic carbon analysis were treated with 10% HCl to remove carbonate, 
rinsed with distilled water, and freeze-dried. The isotopic composition of organic carbon 
was then determined using an elemental analyzer (EA-CE 1500 NA, Carlo Erba) coupled 
with an isotope ratio mass spectrometer (IRMS) (VG Isoprime; UMR PEGASE – INRA 
Rennes). Tin capsules were used for sample loading. The analytical uncertainty is ±0.2‰ 
for C of organic carbon. 
Supplementary figures 
 
 
 
Figure S1: Lithostratigraphic column of the Francevillian Group. 
 
 
 
 
 
 
 
Figure S2: Distribution of carbonate concretions and silt-sandstone beds within host 
black-shales (yellow dots) in the Francevillian B Formation at the Moanda station. (A) 
Lower section displaying alignments A1 and A4. (B) Upper section displaying alignments 
A4 to A8. The middle grey layer corresponds to a fine sandstone layer (see Fig. 2). Note 
that some alignments are not visible at this scale. 
 
 
Figure S3: Morphologies of carbonate concretions within the black shale host in the 
Francevillian B formation. (A) Rounded concretion, (B) Ellipsoidal (flattened) concretion 
(alignment A5, nodule N1). Numbers refer to analyzed samples, (C) Flattened and 
fractured concretions of more than 2-m long, (D) Ellipsoidal concretions of 5 to 15 cm 
long, (E and C) differential compaction of black shale host around concretions. 
 
 
 
Figure S4: XRD Powder diffractograms of different samples from the centre of a 
concretion (A) to the upper and lower edges (B) and lateral edge (C), and in the black 
shale host rock (D). Identified minerals are Dolomite (Do), Pyrite (Py), Quartz (Q), 
Plagioclase (P), Mica or Illite (M), Chlorite (C), and Mixed-layer (ML). 
 
 
 
 
 
Figure S5: Petrography of internal structure of ovoid concretion in alignment A5: (A) 
Dolomitic matrix showing two dolomitic phases (Ferroan dolomite (clear) and pure 
dolomite (dark) in the part of the concretions; (B) view of an organic-rich lamina 
showing wavy lamination; (C) close to the central pyritic stripe, small organic matter 
clusters in an homogenous matrix; (D) at the top of concretion, disperse patches of 
organic matter; (E) recrystallised dolomite in the porosity (arrow) close to the host-rock. 
(F) Massive pyrite crystals (light grey) in the centre of each concretion and enclosing 
xenomorphic dolomite (dark grey). 
 
 
 
Figure S6: (A) PAAS-normalised REE+Y patterns of carbonate concretion (center #45, 
#46; see Suppl. Tab. 2) and edge (#56)), and black shale host rock (#33). (B) PAAS 
normalised REE+Y pattern of the carbonate phase in the nodule centre (#45, #46) 
compared to present day Pacific seawater (Alibo and Nozaki, 1999) and Paleoproterozoic 
seawater (Bau and Dulski, 1996). PAAS values according to Taylor and MacLennan 
(1985). 
 
 
Figure S7: Lateral evolution in dolomitic concretion (A) of the carbonate content 
CaMg(CO3)2, (B), the carbon (C), and the oxygen (D) isotope compositions of the 
carbonate fraction. 
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Supplementary table 2: Geochemical data on the Paleoproterozoic concretions and 
enclosing rock in Moanda section. See accompanying .xls file 
 
Supplementary table 3: Paleotemperature calculated from the oxygen isotope 
composition of the centre of Moanda concretions, using different seawater-dolomite 
fractionation factors, and using different values for the isotopic composition of seawater 
(δ18Ow): value for an ice-free world (-1‰) and different values for Paleoproterozoic 
seawater (-8.5 and -6‰; Jaffrés et al. 2007). The temperature dependence of the 
fractionation factor α is calculated using the equation: 103 ln α = A.106 / T² + B.103 / T + 
C 
 
 
Vasconcelos 
et al. (2005) 
Matthews 
et al. (1977) 
Fritz and 
Smith (1970) 
Zheng (1999) 
Parameters for the equation 
A 2.73 3.06 2.62 4.06 
B 0 0 0 -4.65 
C 0.26 -3.24 2.1 1.71 
Calculated paleotemperature (°C) 
Nodule 1, δ18O = -7.6 ‰ (PDB) 
δ18Ow = -1 ‰ (SMOW) 67.4 63.3 74.7 63.1 
δ18Ow = -8.5 ‰ (SMOW) 23.3 24.4 26.6 26.9 
δ18Ow = -6 ‰ (SMOW) 36.1 35.9 40.3 37.6 
Nodule 2, δ18O = -7.9 ‰ (PDB) 
δ18Ow = -1 ‰ (SMOW) 69.6 65.2 77.1 64.9 
δ18Ow = -8.5 ‰ (SMOW) 24.8 25.7 28.1 28.1 
δ18Ow = -6 ‰ (SMOW) 37.7 37.3 42.1 38.9 
 
 
 
 
 
 
References 
 
Alibo, D.S., Nozaki, Y., 1999. Rare earth elements in seawater: Particle association, 
shale-normalization and Ce oxidation. Geochim. Cosmochim. Acta 63, 363–372. 
Bau, M., Dulski, P., 1996. Distribution of yttrium and rare-earth elements in the Penge 
and Kuruman iron-formations, Transvaal Supergroup, South Africa. Precam. Res. 
79, 37-55. 
Canfield, D.E., Ngombi-Pemba, L., Hammarund, E.U., Bengston, S., Chaussidon, M., 
Gauthier-Lafaye, F., Meunier, A., Riboulleau, A., Rollion-Bard, C., Rouxel, O., 
Asael, D., Pierson-Wickmann, A.-C., El Albani, A., 2013. Oxygen dynamics in the 
aftermath of the Great Oxidation of Earth’s atmosphere. PNAS 110, 16736-16741. 
Carignan, J., Hild, P., Mevelle, G., Morel, J., Yeghicheyan, D., 2001. Routine analyses of 
trace elements in geological samples using flow injection and low pressure on-line 
liquid chromatography coupled to ICP-MS: A study of geochemical reference 
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The role of the early diagenetic dolomitic concretions in the preservation of the 2.1-Ga paleoenvironmental signal: The Paleoproterozoic of the Franceville Basin, Gabon

Isabelle Manighetti

From past to current tectonics: Thematic issue dedicated to Jean-François Stéphan (1949–2013)

René Blanchet

In memory of Jean-François Stéphan

CV2 - Editorial board ENG

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