Fossils from Quaternary fluvial archives : sources of biostratigraphical, biogeographical and palaeoclimatic evidence.

Fluvial sedimentary archives have the potential to preserve a wide variety of palaeontological evidence, ranging from robust bones and teeth found in coarse gravel aggradations to delicate insect remains and plant macrofossils from fine-grained deposits. Over the last decade, advances in Quaternary biostratigraphy based on vertebrate and invertebrate fossils (primarily mammals and molluscs) have been made in many parts of the world, resulting in improved relative chronologies for fluviatile sequences. Complementary fossil groups, such as insects, ostracods and plant macrofossils, are also increasingly used in multi-proxy palaeoclimatic and palaeoenvironmental reconstructions, allowing direct comparison of the climates and environments that prevailed at different times across widely separated regions. This paper reviews these topics on a regional basis, with an emphasis on the latest published information, and represents an update to the 2007 review compiled by the FLAG-inspired IGCP 449 biostratigraphy subgroup. Disparities in the level of detail available for different regions can largely be attributed to varying potential for preservation of fossil material, which is especially poor in areas of non-calcareous bedrock, but to some extent also reflect research priorities in different parts of the world. Recognition of the value of biostratigraphical and palaeoclimatic frameworks, which have been refined over many decades in the 'core regions' for such research (particularly for the late Middle and Late Pleistocene of NW Europe), has focussed attention on the need to accumulate similar palaeontological datasets in areas lacking such long research histories. Although the emerging datasets from these understudied regions currently allow only tentative conclusions to be drawn, they represent an important stage in the development of independent biostratigraphical and palaeoenvironmental schemes, which can then be compared and contrasted

Conservation status of a recently described endemic land snail, Candidula coudensis, from the Iberian Peninsula

Research ArticleWe assessed the distribution, population size and conservation status of Candidula coudensis, a recently described endemic land snail from Portugal. From March 2013 to April 2014, surveys were carried out in the region where the species was described. We found an extent of occurrence larger than originally described, but still quite small (13.5 km2). The species was found mainly in olive groves, although it occurred in a variety of other habitats with limestone soils, including grasslands, scrublands and stone walls. Minimum population estimate ranged from 110,000–311,000 individuals. The main identified potential threats to the species include wildfires, pesticides and quarrying. Following the application of IUCN criteria, we advise a conservation status of either “Least Concern” or “Near-threatened” under criterion D (restricted population)info:eu-repo/semantics/publishedVersio

Fossils from Quaternary fluvial archives: sources of biostratigraphical, biogeographical and palaeoclimatic evidence

Fluvial sedimentary archives have the potential to preserve a wide variety of palaeontological evidence, ranging from robust bones and teeth found in coarse gravel aggradations to delicate insect remains and plant macrofossils from fine-grained deposits. Over the last decade, advances in Quaternary biostratigraphy based on vertebrate and invertebrate fossils (primarily mammals and molluscs) have been made in many parts of the world, resulting in improved relative chronologies for fluviatile sequences. Complementary fossil groups, such as insects, ostracods and plant macrofossils, are also increasingly used in multi-proxy palaeoclimatic and palaeoenvironmental reconstructions, allowing direct comparison of the climates and environments that prevailed at different times across widely separated regions. This paper reviews these topics on a regional basis, with an emphasis on the latest published information, and represents an update to the 2007 review compiled by the FLAG-inspired IGCP 449 biostratigraphy subgroup. Disparities in the level of detail available for different regions can largely be attributed to varying potential for preservation of fossil material, which is especially poor in areas of non-calcareous bedrock, but to some extent also reflect research priorities in different parts of the world. Recognition of the value of biostratigraphical and palaeoclimatic frameworks, which have been refined over many decades in the 'core regions' for such research (particularly for the late Middle and Late Pleistocene of NW Europe), has focussed attention on the need to accumulate similar palaeontological datasets in areas lacking such long research histories. Although the emerging datasets from these understudied regions currently allow only tentative conclusions to be drawn, they represent an important stage in the development of independent biostratigraphical and palaeoenvironmental schemes, which can then be compared and contrasted

Discontinuités longitudinales des dynamiques sédimentaires holocènes dans les petites vallées de l'Ouest du Bassin Parisien, l'exemple de la Mue

International audienceGeomorphologic and palaeoenvironmental researches conducted in the Mue valley allow improving the valley bottom sedimentation knowledge in the Plain of Caen and more generally in the sedimentary area of Lower Normandy, both poorly known areas of the Paris basin. They underline the extent, the heterogeneity and the originality of the Postglacial infilling. The systematic geomorphologic survey in this valley bottom, 24 km long, is based on boreholes and core drillings in the key areas. The Lateglacial filling is missing like in most of the valleys of Normandy while the Holocene sedimentation is 4 to 15 m thick. Its longitudinal arrangement is characterized by sections with different morphologic and sedimentary features. The succession of tufaceous, peaty, detritic or mixed deposits illustrates the fluvial system complexity and offers opportunity for multi-proxy analyses. To establish the Holocene chronostratigraphy and to determine the role of the palaeohydrologic and anthropogenic control in the sedimentary changes, sedimentologic, malacologic, pollen analyses and radiocarbon dating (21) have been undertaken. The filling begins around 9000 14C BP with tufaceous deposits. Locally, they are very thick (7 to 13 m) and form barriers in the valley bottom. From the Atlantic and Sub-Boreal periods (6500-4500 14C BP) peat deposits become widespread, in particular behind the tufa barriers. Nevertheless, the onset of the alluvial aggradation is diachronic along the valley bottom and the alluvial sedimentation has a high variability in relation with the valley morphology and the local geological controls. Since the Bronze Age (3500 14C BP) and mainly during the Iron Age and Gallo-Roman period, the spread of detritic alluvial sedimentation derived from the erosion of tufaceous deposits and loamy soils testifies the increase of land use changes within the river basin. However the spatial variability of landscapes and sedimentation is also strongly controlled by local human activities. The research underlines the necessity of longitudinal studies to take into account the spatial and time discontinuities of the Holocene hydro-sedimentary systems even in small order valleys in sedimentary basins.Les recherches géomorphologiques et paléoenvironnementales entreprises dans la vallée de la Mue contribuent à la connaissance de l'évolution des dynamiques de fonds de vallée dans la Plaine de Caen et plus généralement de la partie sédimentaire de la Basse-Normandie restées à l'écart des études récentes sur l'Holocène. Elles soulignent l'ampleur, l'hétérogénéité et l'originalité des remplissages sédimentaires postglaciaires. L'inventaire systématique du remplissage de cette vallée de 24 km de long s'est appuyé sur la réalisation de sondages ainsi que sur des carottages dans les secteurs clefs. La sédimentation tardiglaciaire apparaît absente comme dans de nombreuses vallées normandes mais la sédimentation holocène est particulièrement dilatée atteignant 4 à 15 m. Elle obéit à un dispositif longitudinal marqué par la succession de plusieurs tronçons aux caractéristiques morphologiques et sédimentaires différentes. La succession de formations tufacées, tourbeuses, détritiques ou mixtes révèle la complexité du fonctionnement du système fluvial en même temps qu'elle offre un potentiel intéressant pour les analyses multiparamètres. Les analyses sédimentologiques, malacologiques et palynologiques appuyées sur la réalisation de 21 datations radiocarbones permettent de reconstituer la chronostratigraphie des 9 derniers millénaires et d'apprécier le rôle des facteurs paléohydrologiques et anthropiques dans la mutation des milieux sédimentaires. La sédimentation qui s'amorce au début de l'Holocène (9000 14C BP) se caractérise par la mise en place de formations tufacées parfois très dilatées (de 7 à 13 m) qui sont à l'origine de la construction de véritables seuils dans le fond de vallée. Ce n'est qu'au cours de l'Atlantique et du début du Subboréal (6500-4500 14C BP) que le remplissage sédimentaire, principalement tourbeux se généralise, en particulier en arrière des seuils à sédimentation carbonatée. Le diachronisme de ces séquences sédimentaires souligne le poids des conditions locales. A partir de l'âge du Bronze (3500 14C BP), les formations détritiques résultant de l'érosion des tufs et des sols limoneux des plateaux se développent puis prennent de l'ampleur au cours de l'Âge du Fer et de l'époque gallo-romaine attestant l'emprise croissante des hommes sur les milieux. Cet article souligne l'intérêt d'étendre les recherches dans les trois dimensions des systèmes fluviaux afin de prendre en compte les discontinuités spatio-temporelles des systèmes hydro-sédimentaires holocènes, même dans des vallées de faible ordre

Discontinuités longitudinales des dynamiques sédimentaires holocènes dans les petites vallées de l'Ouest du Bassin Parisien, l'exemple de la Mue

International audienceGeomorphologic and palaeoenvironmental researches conducted in the Mue valley allow improving the valley bottom sedimentation knowledge in the Plain of Caen and more generally in the sedimentary area of Lower Normandy, both poorly known areas of the Paris basin. They underline the extent, the heterogeneity and the originality of the Postglacial infilling. The systematic geomorphologic survey in this valley bottom, 24 km long, is based on boreholes and core drillings in the key areas. The Lateglacial filling is missing like in most of the valleys of Normandy while the Holocene sedimentation is 4 to 15 m thick. Its longitudinal arrangement is characterized by sections with different morphologic and sedimentary features. The succession of tufaceous, peaty, detritic or mixed deposits illustrates the fluvial system complexity and offers opportunity for multi-proxy analyses. To establish the Holocene chronostratigraphy and to determine the role of the palaeohydrologic and anthropogenic control in the sedimentary changes, sedimentologic, malacologic, pollen analyses and radiocarbon dating (21) have been undertaken. The filling begins around 9000 14C BP with tufaceous deposits. Locally, they are very thick (7 to 13 m) and form barriers in the valley bottom. From the Atlantic and Sub-Boreal periods (6500-4500 14C BP) peat deposits become widespread, in particular behind the tufa barriers. Nevertheless, the onset of the alluvial aggradation is diachronic along the valley bottom and the alluvial sedimentation has a high variability in relation with the valley morphology and the local geological controls. Since the Bronze Age (3500 14C BP) and mainly during the Iron Age and Gallo-Roman period, the spread of detritic alluvial sedimentation derived from the erosion of tufaceous deposits and loamy soils testifies the increase of land use changes within the river basin. However the spatial variability of landscapes and sedimentation is also strongly controlled by local human activities. The research underlines the necessity of longitudinal studies to take into account the spatial and time discontinuities of the Holocene hydro-sedimentary systems even in small order valleys in sedimentary basins.Les recherches géomorphologiques et paléoenvironnementales entreprises dans la vallée de la Mue contribuent à la connaissance de l'évolution des dynamiques de fonds de vallée dans la Plaine de Caen et plus généralement de la partie sédimentaire de la Basse-Normandie restées à l'écart des études récentes sur l'Holocène. Elles soulignent l'ampleur, l'hétérogénéité et l'originalité des remplissages sédimentaires postglaciaires. L'inventaire systématique du remplissage de cette vallée de 24 km de long s'est appuyé sur la réalisation de sondages ainsi que sur des carottages dans les secteurs clefs. La sédimentation tardiglaciaire apparaît absente comme dans de nombreuses vallées normandes mais la sédimentation holocène est particulièrement dilatée atteignant 4 à 15 m. Elle obéit à un dispositif longitudinal marqué par la succession de plusieurs tronçons aux caractéristiques morphologiques et sédimentaires différentes. La succession de formations tufacées, tourbeuses, détritiques ou mixtes révèle la complexité du fonctionnement du système fluvial en même temps qu'elle offre un potentiel intéressant pour les analyses multiparamètres. Les analyses sédimentologiques, malacologiques et palynologiques appuyées sur la réalisation de 21 datations radiocarbones permettent de reconstituer la chronostratigraphie des 9 derniers millénaires et d'apprécier le rôle des facteurs paléohydrologiques et anthropiques dans la mutation des milieux sédimentaires. La sédimentation qui s'amorce au début de l'Holocène (9000 14C BP) se caractérise par la mise en place de formations tufacées parfois très dilatées (de 7 à 13 m) qui sont à l'origine de la construction de véritables seuils dans le fond de vallée. Ce n'est qu'au cours de l'Atlantique et du début du Subboréal (6500-4500 14C BP) que le remplissage sédimentaire, principalement tourbeux se généralise, en particulier en arrière des seuils à sédimentation carbonatée. Le diachronisme de ces séquences sédimentaires souligne le poids des conditions locales. A partir de l'âge du Bronze (3500 14C BP), les formations détritiques résultant de l'érosion des tufs et des sols limoneux des plateaux se développent puis prennent de l'ampleur au cours de l'Âge du Fer et de l'époque gallo-romaine attestant l'emprise croissante des hommes sur les milieux. Cet article souligne l'intérêt d'étendre les recherches dans les trois dimensions des systèmes fluviaux afin de prendre en compte les discontinuités spatio-temporelles des systèmes hydro-sédimentaires holocènes, même dans des vallées de faible ordre