New Jurassic amber outcrops from Lebanon

International audienceAmber predating the Lower Cretaceous is extremely rare. During the past two decades, records of discoveries of amber sites have increased considerably worldwide. We report herein the discovery of ten new outcrops of amber from the Late Jurassic in Lebanon, in addition to other nine outcrops described by Azar et al. (2010). Some of these outcrops gave large centimetric sized amber pieces. Each of these new amber outcrops is described, and its infrared spectrum is given. Though the Jurassic amber yielded to date no more than some fungal inclusions, this discovery is significant and promising especially in the reconstruction of the paleoenvironment

Nouveaux gisements fossilifères à Charophytes barrémiens dans les "Grès du Liban" auct. (Liban), avec un point de vue critique sur la nature de Munieria Deecke, 1883

The "Grès du Liban" auct. is the thick basal unit of the Lower Cretaceous series in Lebanon. There are two key levels in this dominantly siliciclastic unit: the "Banc de Mréjatt" and the "Calcaire à pisolithes", the latter of which includes limestones and marls with Charophyta. The rich charophyte assemblage described by Grambast and Lorch (1968) from a site near Jezzine is Barremian (possibly Early Barremian) in age, not Bedoulian as previously stated. Besides gyrogonites and utricles, charophyte thalli are rather common; they are ascribed to two organ genera, Munieria Deecke, 1883, and Charaxis Harris, 1939. Based on topotypic material (from the Pia Collection), Munieria baconica Deecke, 1883, the type-species of the genus, is reassessed. In addition, the species Clypeina parvula Carozzi, 1946, is transferred to the revised genus Munieria, and a new species of Charaxis is described.Les "Grès du Liban" auct. constituent l'épaisse unité à la base des séries du Crétacé inférieur au Liban. Il y a deux niveaux-repères dans cette unité essentiellement silicoclastique : le "Banc de Mréjatt" et le "Calcaire à pisolithes" ; ce dernier comporte des passées calcaires ou marneuses à Charophytes. La riche association de Charophytes décrite par Grambast et Lorch (1968) comme provenant d'un site proche de Jezzine est d'âge barrémien (peut-être Barrémien inférieur) et non bédoulien comme cela était indiqué précédemment. À côté des gyrogonites et des utricules, les thalles de Charophytes sont plutôt communs ; ils sont attribués à deux genres d'organes, Munieria Deecke, 1883, et Charaxis Harris, 1939. Sur la base de matériel topotypique (provenant de la Collection Pia), Munieria baconica Deecke, 1883, l'espèce-type du genre, est réexaminée. Pour compléter cette étude, nous transférons l'espèce Clypeina parvula Carozzi, 1946, dans le genre Munieria révisé et décrivons une nouvelle espèce du genre Charaxis

Avancées dans une réécriture de l'histoire de la transition du Jurassique au Crétacé dans le Mont Liban

The stratigraphic framework of the Upper Jurassic and Lower Cretaceous strata of Lebanon that dates back to Dubertret's publications required either consolidation or full revision. The preliminary results of our investigations in the Mount Lebanon region are presented here. We provide new micropaleontological and sedimentological information on the Salima Oolitic Limestones, which is probably an unconformity-bounded unit (possibly Early Valanginian in age), and the "Grès du Liban" (Barremian in age). Our revised bio- and holostratigraphic interpretations and the new age assignations lead us to emphasize the importance of the two hiatuses in the sedimentary record below and above the Salima, i.e., at the transition from the Jurassic to the Cretaceous.Le canevas stratigraphique du Jurassique supérieur et du Crétacé inférieur du Liban date des publications anciennes de Dubertret et aurait donc besoin d'être soit toiletté et consolidé, soit révisé de fond en comble. Les résultats préliminaires de nos recherches dans la région du Mont Liban sont exposés ici. Nous fournissons des données micropaléontologiques et sédimentologiques inédites sur les Calcaires oolithiques de Salima, qui constituent vraisemblablement une unité lithostratigraphique particulière, une "UBU", car encadrée par deux discontinuités (probablement d'âge Valanginien inférieur), et sur le Grès du Liban (d'âge barrémien). Nos nouvelles interprétations bio- et holostratigraphiques, ainsi que nos nouvelles attributions chronostratigraphiques, nous permettent de souligner l'importance des deux lacunes sédimentaires encadrant les Calcaires oolithiques de Salima, c'est-à-dire des lacunes significatives situées dans l'intervalle de transition du Jurassique au Crétacé

Lebanese Jurassic versus Cretaceous amber: Chemical characterization

International audienceAbout 400 different amber outcrops have been found in Lebanon, which are dated as Early Cretaceous ("Neocomian", about 140-120 Ma).Lebanese Cretaceous amber is recognized as being one of the most fossiliferous in the world, with a large variety of arthropods (insects, arachnids) and botanical remains found preserved in the fossilized tree resin [1]. These fossils provide information on a vanished ecosystem that existed at the time of the resin secretion by a certain botanical family. Plant remains found in some amber pieces are assignable to two potential families of conifers, the still extant Araucariaceae and the exclusively extinct Cheirolepidiaceae. More recently, we added 19 further amber outcrops which we dated as Late Jurassic (Basaltic Kimmeridgian age circa 150 Ma), and in which we found fungal inclusions but no plant or insect inclusions to date [2, 3]. The high number of outcrops and the different ages are a great potential to reconstruct the evolution of past forest environments. But biological inclusions are not sufficient and the chemical characterization of amber itself allows us to shed light on the potential tree source of the resins through different chemical biomarkers which are characteristic of different families of plants. A more complete reconstruction of these ancient ecosystems is thus possible by combining the chemical and biological studies. To investigate the respective botanical sources of Cretaceous and Jurassic Lebanese ambers, we conducted a comparative chemical characterization using both Fourier Transform Infrared spectroscopy (FTIR) and Pyrolysis-Gas Chromatography-Mass Spectroscopy (Py-GC-MS) analyses. The latter reveals that both Jurassic and Cretaceous ambers belong in the Class Ib amber (a classification based on Polylabdanoides skeleton) along with a potential presence of Abietane and Pimarane skeleton. The FTIR analysis, shows a high resemblance between both ambers which present some affinities with modern resins of the conifer families Araucariaceae and Cupressaceae, though the extinct family Cheirolepidiaceae cannot be excluded as a potential source. Finally these results suggest a rather stable forest paleoenvironment in Lebanon during these two geological ages, as both Cretaceous and Jurassic ambers have probably the same botanical origin

The first non‐marine ostracod fauna from the Lower Barremian dysodiles of Lebanon

International audienc

New Jurassic amber outcrops from Lebabon

International audienceReports of amber of occurrence predating the Lower Cretaceous are extremely rare. During the past two decades, records of discoveries of amber sites have increased considerably worldwide, consequently to the alertness by the scientific community of the importance and conservational pristine quality of the amber. Lebanon is weil known to contain abundant Lower Cretaceous amber outcrops (more than 400 localities). A number of these outcrops yielded the oldest amber containing intensive biological inclusions. We report herein the discovery of nineteen outcrops of amber from the Late Jurassic in Lebanon. Sorne of these outcrops gave large centimetric sized amber pieces. These new amber sites are ail located in the Northern part of Mount Lebanon in volcano-Iateritic Late Jurassic deposits (Kimmeridgian age, circa -150 Million Years). The amber is found in lens of lignite mixed with laterites and pyrite that occupy pits in a volcano-basaltic complex sail. The characterization of these Late Jurassic ambers is performed by studying their chemical constitution via FTIR (Fourier Transform InfraRed) spectroscopy. Though the new Jurassic amber yielded to date no more than some fungal inclusions, but the discovery of such material is very significant and promising especially in the reconstruction of the paleoenvironment. It also opens great prospects to reveal hopefully some Late Jurassic fossil arthropods

Révision de la "Falaise de Blanche" (Crétacé inférieur) au Liban et définition de l'Étage Régional Jezzinien

International audienceThe "Falaise de Blanche" is a prominent cliff, consisting mostly of Lower Cretaceous limestones that extends as linear outcrops over most of the Lebanese territory and provides geologists a remarkable reference for stratigraphic studies. However, until now, this unit was lacking a clear definition. We introduce herein the Jezzinian Regional Stage, the type-locality of which is at Jezzine. It equates as an unconformity-bounded unit and, per definition, it is framed by two discontinuities. Because we identified an additional, median sequence-boundary, poorly-expressed in the type-section but better at Aazour, only 4.5 km westward of Jezzine, the new regional stage implicitly spans two sequences. The lithostratigraphic framework being properly redefined, we were able to investigate time-constrained micropaleontological assemblages, consisting mostly of benthic foraminifers and calcareous algae. Typically Southern Tethysian, these assemblages contribute to high-resolution, holostratigraphic correlations with the Persian Gulf area, on the eastern part of the Arabian Plate. The Jezzinian interval correlates with the upper part of the Kharaibian Regional Stage (also known as "Thamama II" reservoir unit in the oil industry). In turn, the Jezzinian is indirectly correlated with the Northern Tethysian Urgonian stratigraphic units where it corresponds to a rather short interval encompassing the standard Barremian - Bedoulian stage boundary. Locally the upper discontinuity is associated to a significant intra-Bedoulian hiatus. The macrofossil assemblages found in the Jezzinian (echinids) and above it (ammonites) support, or at least do not contradict, our micropaleontological dating.Les calcaires du Crétacé inférieur de la "Falaise de Blanche" affleurent sur une grande partie du territoire libanais. Ils apparaissent dans le paysage sous forme d'escarpements linéaires saillants constituant autant de points d'ancrage remarquables pour tout recalage stratigraphique. Toutefois, jusqu'à très récemment, cette unité était piètrement caractérisée : il lui manquait notamment une définition rigoureuse. Nous introduisons ici l'Étage Régional Jezzinien, dont la localité-type est sise à Jezzine. Il s'agit d'une unité stratigraphique particulière, aussi appelée U.B.U. (pour "unconformity-bounded unit"), une unité qui, par définition, est encadrée par deux discontinuités. Parce que nous avons identifié une limite de séquence supplémentaire, en position médiane, peu exprimée dans la section-type, mais beaucoup mieux à Aazour, à 4,5 km à peine à l'ouest de Jezzine, le nouvel étage régional devrait implicitement couvrir deux séquences. Le canevas lithostratigraphique étant clairement redéfini, nous avons pu étudier les associations micropaléontologiques, constituées essentiellement de foraminifères benthiques et d'algues calcaires, associations dorénavant relativement bien contraintes du point de vue de leur âge. Typiquement sud-téthysiennes, elles facilitent les corrélations holostratigraphiques à haute résolution avec la région du Golfe persique, sur le côté oriental de la Plaque arabique. L'intervalle Jezzinien correspond ainsi à la partie supérieure de l'Étage Régional Kharaibien (aussi connu comme unité réservoir "Thamama II" dans l'industrie pétrolière). À son tour, le Jezzinien est indirectement corrélé avec les unités stratigraphiques urgoniennes nord-téthysiennes où il correspond à un intervalle relativement court comprenant la limite des étages standards (internationaux) Barrémien et Bédoulien. Localement la discontinuité sommitale est associée à un hiatus intra-Bédoulien significatif. Les associations macropaléontologiques reconnues dans le Jezzinien (échinides) et au-dessus de cette unité (ammonites) viennent à l'appui de notre datation micropaléontologique ou tout au moins ne la contredisent pas

Geochemical and petrographic analyses of new petroleum source rocks from the onshore Upper Jurassic and Lower Cretaceous of Lebanon

International audienceThe recent interest in the Lebanese petroleum potential led to new studies mainly concerning marine petroleum source rocks, without taking in consideration the dysodiles and other associated facies from the Upper Jurassic and the Lower Cretaceous. These organic-rich outcrops of metric thickness (max. 3 m) are of limited lateral extension and often found next to volcanic deposits. Sixty-three samples were collected from 25 different localities, and were subdivided into three facies that are presented in this paper: (i) dysodiles formed by the superposition of millimetric layers that are easy to separate; (ii) dysodiles-like with distinct, but more compacted layers; (iii) non-dysodiles where the layering is not visible. The aim of this work is to assess the origin of these organic-rich rocks, and to evaluate their source rock potential. We used herein Rock-Eval pyrolysis, elemental analysis, palynofacies observation, organic petrography and molecular geochemical analyses. Rock-Eval pyrolysis reveals a very good to excellent source-rock potential for all above cited rock types, with average total organic carbon (TOC) of 14 ± 7% for the dysodiles, 19 ± 12% for the dysodiles-like and 13 ± 9% for the non-dysodiles. Hydrogen index (HI) and oxygen index (OI) values indicate a type I to II kerogen for the dysodiles (average HI = 649 ± 162 mg HC/g TOC), type I to II kerogen for the dysodiles-like (average HI = 340 ± 182 mg HC/g TOC) and type III kerogen for the non-dysodiles (average HI = 145 ± 42 mg HC/g TOC). The dominance of fluorescent amorphous organic matter (AOM) and alginite macerals confirm an algal/bacterial source of organic matter for the dysodiles. The presence of opaque AOM, phytoclasts, sporinites and cutinites macerals, suggests a variable terrestrial organic matter input for the dysodiles-like and non-dysodiles. Maturity parameters such as Tmax values (on average 428 ± 7 °C for dysodiles, 429 ± 6 °C for dysodiles-like and 424 ± 10 °C for non-dysodiles), vitrinite reflectance (1) indicate that the organic matter is still thermally immature. The present study sheds light on the long forgotten dysodile shales and similar material, and their importance as potential source rocks or oil shales. A comparison with local and regional source rocks is provided in order to emphasize the specific character of the dysodile deposits