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Author's personal copy
Cretaceous Research 29 (2008) 925–929
Contents lists available at ScienceDirect
Cretaceous Research
journal homepage: www.elsevier.com/locate/CretRes
A new amber deposit from the Cretaceous (uppermost Albian-lowermost
Cenomanian) of southwestern France
Didier Néraudeau a, *, Vincent Perrichot a, Jean-Paul Colin a, Vincent Girard a, Bernard Gomez a,
François Guillocheau a, Edwige Masure b, Daniel Peyrot a, Florent Tostain a, Blaise Videt a,
Romain Vullo a
a
b
UMR CNRS 6118, Université Rennes 1, Campus de Beaulieu, 263 avenue du Général Leclerc, 35042 Rennes, France
UMR CNRS 5143, Université P. & M. Curie, case 104, Tour 46-56, 5 ème étage, pièce 22D, 4, place Jussieu, 75252 Paris cedex 05, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 August 2006
Accepted in revised form 4 May 2008
Available online 13 June 2008
A Cretaceous amber deposit has recently been discovered in a quarry of Charente-Maritime (southwestern France), at Cadeuil. This paper presents the sedimentary and palaeoenvironmental settings of
the uppermost Albian-lowermost Cenomanian series including the amber deposit. A preliminary analysis
of the amber samples reveals diverse fossil arthropods (a few mites and at least 20 insect families within
9 orders), as well as numerous micro-organisms, mainly algae and mycelia. A myceloid colony of bacteria,
a flagellate algae and four especially well preserved insects are illustrated (Diptera Dolichopodidae,
Diptera Chironomidae, Hymenoptera Parasitica, and Heteroptera Tingidae). The abundance of the limnic
micro-organisms is discussed in terms of bloom events. Their relative scarcity in almost all the amber
pieces containing fossil arthropods is attributed to differences in the origin of resin: production along
trunk and branches for amber with arthropods; production by aquatic roots for amber rich in algae. The
absence of pollen and spores in amber is attributed to differences in the respective periods of resin and
palynomorph production, which may be related to a seasonal climate during the Albian-Cenomanian
transition in Western Europe.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Insects
Microorganisms
Amber
Uppermost Albian-lower Cenomanian
Charente-Maritime
SW France
1. Introduction
2. Geological setting
During the last eight years, several amber localities were
discovered in the department of Charente-Maritime, in southwestern France. These deposits appear to be amongst the most
fossiliferous amber deposits globally known from the Cretaceous
with those from Canada, Lebanon, Myanmar, New Jersey, Siberia,
and Spain (Perrichot, 2005). The first fossiliferous amber deposit
was discovered in 1999 in a sand quarry at Archingeay-Les Nouillers, and is dated as latest Albian (Néraudeau et al., 2002). In 2000,
a second deposit from the mid lower Cenomanian was found on the
tidal flat at Fouras (Néraudeau et al., 2003). The amber deposit
described in the present paper was discovered at Cadeuil in 2001 in
a new sand quarry, and provides additional data for analysing the
geological and palaeoecological frameworks of the Cretaceous
amber deposits from France.
The Cadeuil area is located at about ten kilometres from the
Seudre estuary (Fig. 1), in the western part of the Saintes synclinal
(Néraudeau & Moreau, 1989). In the quarry under study, the
uppermost Albian to lower Cenomanian deposits occur directly on
top of the Upper Jurassic substratum (Kimmeridgian to Tithonian),
and represent transgressive deposits which have eroded the
underlying strata. These deposits are mainly composed of fluviatile
and paralic sand, but contain several clayey intercalations with
local concentrations of fossil plant cuticles (Gomez et al., 2004). At
the regional scale, Arnaud (1877), Moreau (1976, 1993a) and
Néraudeau et al. (1997, 2002, 2005) considered the alternating sand
and clay beds as belonging to the lithological unit A, which they
subdivided into two subunits: A1, sand of various grain sizes,
arranged in large cross beddings, bearing abundant lignite and
amber accumulations, and latestmost Albian in age according to the
palynology (Néraudeau et al., 2002); A2, fine sand, mainly arranged
in horizontal beds, bearing rare wood remains, and earlymost
Cenomanian in age (Moreau, 1993a,b). The unit A is overlain by
a shelly sand (‘‘falun’’ sensu Vullo et al., 2003) rich in orbitolines
and oysters which marks the base of the lithological unit B (subunit
B1). This unit includes the oldest Cenomanian rudist-bearing facies
* Corresponding author.
E-mail address: [email protected] (D. Néraudeau).
0195-6671/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cretres.2008.05.009
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D. Néraudeau et al. / Cretaceous Research 29 (2008) 925–929
Fig. 1. Geographical and geological settings of the uppermost Albian to lower Cenomanian amber deposits from Charente-Maritime (southwestern France): Archingeay/LesNouillers (upper Albian); Fouras (mid lower Cenomanian); Cadeuil (uppermost Albian to lowermost Cenomanian).
in this region (Néraudeau et al., 1997). In the Cadeuil area, the main
amber deposit is located in the top of the subunit A1.
3. Lithostratigraphy and palaeoenvironments
The basal sediments of the geological section of Cadeuil consist
of 2 m of coarse sand (A1), which is of brackish to coastal marine
origin. The sand includes three remarkable fossiliferous horizons,
which follow on top of 0.5 m of sand barren in fossils (Fig. 2). The
first horizon (A1a) consists of a few clayey lenses bearing plant
cuticle compressions (sensu Schopf, 1975 and Martin-Closas and
Gomez, 2004); the second one (A1b) provides a large amount of
lignite, i.e. an accumulation of fossil wood, together with numerous
pieces of amber; the third horizon (A1c) consists in a hard and
coarse sandstone with metric cross beddings, which correspond to
a succession of channels. This horizon locally includes lignite and
amber, sometimes with marine mollusk accumulations. A few selachian (e.g., ‘‘Carcharias’’ (Cappetta and Case, 1975)) and pycnodontiform teeth and echinoid fragments (undetermined
spatangoids and cidaroids) are locally associated with the mollusks.
The section continues with 10 to 15 m of estuarine sand and clay
alternations, which are arranged in horizontal beds and which
constitute the subunit A2. The lower part of A2 mainly consists of
white fine sand devoid of fossils, while the middle and upper parts
include clay beds, and display a few layers bearing fossil plant
cuticles.
In this quarry, the top of the coarse fossiliferous sandstones is
considered as the limit between subunits A1 and A2. The sandstones from the level A1c are dated as early Cenomanian by
ostracods, such as the species Neocythere inornata Colin, 1974 or the
genera Curfsina, Mauritsina, Dordoniella, and Spinoleberis (Colin,
1974; Damotte et al., 1981). However, the lignite and clay from
levels A1a and A1b are not clearly dated because they are devoid of
any Cenomanian markers but contain dynocysts which apppeared
in the late Albian and survived in the Cenomanian, such as Palaeohystrichophora infusorioides Deflandre, 1935 and Oligosphaeridia
poculum Jain, 1977. According to the sequence stratigraphy analysis
of all the Albian-Cenomanian sections from the same region (Videt,
2004) the subunit A1, as observed in Cadeuil, can be correlated with
the A1 partly dated by palynology as latest Albian at Archingeay-Les
Nouillers (level A1sl2 in Néraudeau et al., 2002). Finally, the amber
from Cadeuil can be dated as latest Albian-earliest Cenomanian.
The top of the Cadeuil section corresponds to the lower part of
the subunit B1 (« faluns » sensu Vullo et al., 2003). It begins by 0.5 m
of carbonate-rich sand (B1a), especially rich in the large benthic
foraminifer Orbitolina concava (Lamarck, 1816), in small oysters
(Rhynchostreon, Ceratostreon, Rastellum), in echinoids (Goniopygus
menardi (Desmarest, 1825), Tetragramma variolare (Brongniart,
1822), Nucleopygus aff. similis (d’Orbigny, 1856)), and in selachian
teeth (‘‘Carcharias’’ amonensis, Tribodus morlati (Landemaine, 1991),
Hybodus sp.). Finally, this sand is overlain by limestones bearing
large rudists (Ichthyosarcolithes triangularis Desmarest, 1817),
crustaceans (Protocallianassa), oysters (Rhynchostreon, Ceratostreon), and echinoids (Periaster undulatus (Agassiz, 1847)).
4. Amber, inclusions, and plant remains
4.1. Plant assemblage
The wood assemblage preserved in the uppermost Albianlowermost Cenomanian lignite of Cadeuil quarry is entirely
composed of conifers, mainly of the very common Mesozoic morphogenus Agathoxylon (Araucariaceae?), and this is valid both for
the basal lignite accumulation (A1b) as well as for the overlying
sandstone (A1c). In addition, A1c also bears a few wood fragments
identified as Podocarpoxylon (Podocarpaceae), Brachyoxylon, and
Protopodocarpoxylon (Cheirolepidiaceae?) (Perrichot, 2005). The
palynological analysis of A1a by Peyrot et al. (2005) revealed
lycophytes (Retitriletes), ferns (e.g. Cicatricocisporites, Deltoidospora,
Reticulosporis), conifers (e.g. Araucariacites, Classopollis, Inaperturopollenites),
cycads/gingkoes
(Monosulcites/Cycadopites),
and
angiosperms (Afropollis, Clavatipollenites, Tricolpites). Though a few
cuticles of the conifer Glenrosa have been identified, the main
component of the fossil plant cuticles from A1a is by far the cheirolepidiaceous conifer Frenelopsis. The recurrent association of
a large number of these conifer leaves together with the pollen
grains Classopollis provides a challenge to the question of the
identity of the main amber-producing trees for the AlbianCenomanian deposits of the Charentes (Cheirolepidiaceae or/and
Araucariaceae?).
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to honey-coloured and brown pieces (frequent, up to 80 mm).
According to the analysis of the wood fragments embedded in
amber, Agathoxylon would be the main plant source for the amber
from Cadeuil, as is suggested for other amber deposits from
Charente-Maritime by Perrichot (2005). Until now, we have identified about fifty fossil arthropods, mainly insects (Table 1), and
numerous micro-organisms preserved in the amber samples.
Hymenoptera is the largest group in terms of numbers of specimens as well as in terms of diversity, with at least five families
recognized: Braconidae, Megalyridae (Fig. 3A), Platygastridae,
Scolebythidae, Trigonalidae, and an undetermined family in Chalcidoidea. Diptera is the second largest group in terms of numbers of
specimens, including the families Ceratopogonidae, Chironomidae
(Fig. 3B), Dolichopodidae (Fig. 3C), and Psychodidae (Azar et al.,
2007). Other arthropods include a few Acari, Blattodea, Homoptera,
Lepidoptera, Psocoptera, Thysanoptera, and Heteroptera with the
oldest known bug of the family Tingidae (Fig. 3D). Amongst
the micro-organisms, colonies of bacteria (Fig. 3E), green algae of
the genus Enallax (Girard, in press) (Fig. 3F), cyanophyceae, mycelia,
and undetermined germinating fungal spores have been found.
As in the other uppermost Albian-lower Cenomanian amber
deposits from the Charente-Maritime region (Archingeay-Les
Nouillers and Fouras, Fig. 1), almost all the amber samples from
Cadeuil which contain algae are lacking arthropod inclusions, while
the amber pieces which contain arthropods are lacking
palynomorphs.
5. Discussion
In previous sedimentological and palaeontological studies on the
Charente-Maritime amber deposits, an estuarine environment partially influenced by marine incursions was assumed for the latest
Albian epoch at Archingeay-Les Nouillers (Néraudeau et al., 2002),
and a more strongly marine-influenced environment was assumed
for the earliest Cenomanian period at Fouras (Néraudeau et al.,
2003). This is highlighted by the invertebrate fauna, which at
Archingeay-Les Nouillers is restricted to a few brackish to coastal
oysters of one single species (Striostrea sp., Videt and Platel, 2005),
whereas at Fouras oysters are more abundant and diversified
Table 1
Arthropod inclusions in amber from Cadeuil
Order
Taxon
N
Acari
Auchenorrhyncha
Blattaria
Coleoptera
Heteroptera
Lepidoptera
Psocoptera
Thysanoptera
Diptera
indet.
Fulgoroidea
indet.
indet.
Tingidae
indet.
indet.
indet.
Ceratopogonidae
Chironomidae
Dolichopodidae
Psychodidae
Nematocera indet.
Brachycera indet.
Braconidae
Megalyridae
Platygastridae
Scolebythidae
Trigonalidae
Chalcidoidea
indet.
TOTAL, inclusions
2
1
2
1
1a
1
2
1
4
4
3b
1c
2
4
2
1
4
1
2d
2
5
46
Hymenoptera
Fig. 2. Stratigraphical section of the Cadeuil quarry.
4.2. Amber, arthropods and micro-organisms
a
b
The preserved amber shows a wide variety of colours and sizes,
ranging from yellow translucent pieces (rare, smaller than 30 mm)
c
d
Ambarcader eugenie Perrichot et al., 2006.
Microphorites deploegi Nel et al., 2004.
Sycorax neli Azar et al., 2007.
Guyotemaimetsha enigmatica Perrichot et al., 2004.
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D. Néraudeau et al. / Cretaceous Research 29 (2008) 925–929
Fig. 3. Various fossil inclusions in Albian-Cenomanian amber from Cadeuil (Charente-Maritime, SW France). A, Hymenoptera Megalyridae; B, Diptera Chironomidae; C, Diptera Dolichopodidae, Microphorinae: Microphorites deploegi Nel et al., 2004; D, Heteroptera Tingidae Ambarcader eugenei Perrichot et al., 2006; E, Myceloid colony of bacteria; F, Green algae.
(Acutostrea lingularis (Lamarck, 1819), Gyrostrea delettrei (Coquand,
1865), Rhynchostreon suborbiculatum (Lamarck, 1801)) (Videt and
Platel, 2005), and are associated with marine mollusks (Arca sp.,
Pterodonta, sp., Turbo sp.), selachians and ophidians (Néraudeau
et al., 2003; Vullo et al., 2005). In comparison, the amber deposit
from Cadeuil represents a depositional environment which is more
strongly influenced by marine conditions. Indeed, the sandstones
containing lignite and amber (A1c) bear locally marine invertebrates, including numerous bivalves (Arca sp., Neitheia sp.) and
gastropods (Emarginula sp., Fusus sp., Turbo sp., Turritella sp.), and
a few test fragments of irregular and regular echinoids (spatangoids
and cidaroids), which are stenohaline organisms. This palaeoenvironmental interpretation fits well with the palaeogeographical
location of the Cadeuil quarry, which is interpreted to have been
more central in the Aquitain basin than those assumed for the
Archingeay-Les Nouillers and Fouras localities (see Fig. 1).
Finally, this new amber deposit is especially interesting because it
contains both species previously identified in the contemporaneous
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D. Néraudeau et al. / Cretaceous Research 29 (2008) 925–929
amber of Archingeay-Les Nouillers, as well as unpublished, possibly
endemic (?) species. The species common to the two amber deposits,
such as the dolichopodid fly Microphorites deploegi described for
Archingeay by Nel et al. (2004), confirm their biostratigraphic
correlation inferred from palynological data, whereas the newly
identified species, such as the megalyrid wasp figured in this paper
(Fig. 3A), increase our knowledge of the latest Albian to early
Cenomanian entomofauna from the coastal ecosystems of Western
Europe.
Moreover, the abundance of algae in numerous large, nondrop-shaped pieces of amber in which arthropod inclusions are
generally absent, indicates that a large part of the resin probably
exuded from submerged conifer roots, and/or was produced
during periods of algal blooms. Finally, the absence of pollen and
spores of higher plants in fossil resin that has trapped terrestrial
arthropods (insects, arachnids) lends further support to the
hypothesis that the period of resin secretion did not coincide with
the period of pollen production. These different observations could
argue in favour of a season influenced climate pattern during the
Albian-Cenomanian transition.
Acknowledgements
The authors are greatly indebted to Eugène Arnaud and Laurent
Lacombe who collected some amber arthropods studied herein.
They thank Peter Cobbold who revised the english language. This
article is a contribution to to the ANR Project AMBRACE (n BLAN071-184190),to the IFB program ‘‘Interactions biodiversité végétale–
changements globaux à la transition Crétacé inférieur–supérieur
d’Europe occidentale,’’ and to the French-Spanish program Picasso
‘‘Evolution paléobiologique et paléoenvironnementale des gisements d’ambre du Crétacé d’Espagne et de France.’’ Our research
was financially supported by UMR 6118 CNRS, and BG by projects
BTE2001–0185-C02–01 and B052001–0173 of the Spanish
government and project 2001SGR-75 of the Catalan government.
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