Nicole Limondin-Lozouet

Response of the Selle River to climatic modifications during the Lateglacial and Early Holocene (Somme Basin-Northern France)

Abstract Research on Lateglacial sequences from the Selle valley leads to an overview of its evolution in relation to climatic variations between the end of the Weichselian Upper Pleniglacial and the beginning of the Holocene. The first major modification of the fluvial morphology is dated at the Upper Pleniglacial/Lateglacial transition (13,000 14 C-yr BP). At that time, the response to climatic improvement and environmental modifications is marked by downcutting and evolution from a braided river to a transitional river pattern (Bolling infilling in the newly created channels). After a short cold phase recorded in a thin calcareous bed at the top of the Bolling peat attributed to the Older Dryas (Dr. II), the Allerod is characterized by the deposition of organic overbank silts within a large single channel meandering system. In lower slope environments, this period is also marked by slow rates of colluvial accumulation and by the development of upbuilding soils (Allerod soil). On the other hand, the end of the Lateglacial, is characterised by the infilling of the whole valley by fine calcareous overbank silts during the Younger Dryas cold phase (overflow of a large single channel and lateral input of chalk mud). A second major downcutting phase occurs at the beginning of the Holocene at around 10,000 BP, in parallel with another rapid climatic improvement and the renewed spread of vegetation. From a general point of view, the evolution of fluvial environments in the Selle valley is comparable with many other river valleys in NW Europe, showing that fluvial systems react very quickly to climatic variations of short duration (1000 to 100 years). Finally, in the Upper Selle River, incision events occur clearly before the main modifications of the vegetal cover. They are most likely linked to a rapid shift in the balance between water discharge and sediment supply, caused by climate modifications (shift to more temperate and oceanic conditions), and the resulting environmental changes: cessation in aeolian sedimentation, strong reduction of slope processes, permafrost disappearance and soil development.

Reconstruction of climatic changes during the Late Pleistocene, based on sediment records from the Konya Basin (Central Anatolia, Turkey)

Climatic changes during the last climatic cycle have been studied using three sediment cores from the Konya plain, a now dry, closed and semi-arid lacustrine basin at 1000 m altitude in central Anatolia, Turkey. The reconstruction of regional climatic characteristics and evolution is based on mineral, diatom, pollen and molluscan content of sediments. Correlations are made between cores using 14C and U-Th ages, stratigraphy and drought levels shown by changes in mineral contents. Environmental responses to local and regional climatic changes are traced by trends in authigenic carbonates, evaporites, detrital mineral content and by diatom-inferred salinity levels. Our data have shown that, during the period covering the end of the previous Glacial (Termination II) and the last Interglacial (between c. 150 and 117 ka), peat and freshwater shallow lakes expanded. From 117 to 66 ka, the plain was occupied by lakes, the salinity and existence of which varied in time and space. Specific events are marked by mineralogic and stratigraphic signals at (i) c. 101 ka and (ii) 66 ka. From 66 ka to 30 ka, desiccation of the lake is marked by a hiatus. At c. 27 ka, milder climatic conditions led to the extension of freshwater marshes and lakes in the central depressions while palaeosols developed on the emerged parts of the plain. From 25 to 20·5 ka 14C cal., the sediments of a freshwater to brackish lake are present in one core only. From 20·5 ka 14C cal. onwards, strong evaporitic conditions occurred, the lake edges being transformed into playas. Upper parts of the sequences registered other lacustrine short phases, both before the Younger Dryas and during the Holocene. Copyright

River system evolution and environmental changes during the Lateglacial in the Paris Basin (France).

Abstract Lateglacial sequences from the Paris Basin floodplains provide a general overview of the valleys evolution related to climatic changes from the Weichselian Upper Pleniglacial to the beginning of the Holocene. Comparison between morphostratigraphical and palaeobiological data allows discussion of fluvial dynamics and related palaeoenvironmental conditions. The Upper Pleniglacial/Oldest Dryas transition remains poorly documented. It is represented by sands and silts deposited by a braided channel network. The Bolling begins with a significant incision related to a meandering system which is followed by local organic and minerogenic deposition, contemporaneous with vegetation development. The Older Dryas is evident in several sequences. The Allerod appears more stable and the forest extension is accompanied by a thin soil formation on the banks. The Younger Dryas is characterised by a strong infilling of the valleys by calcareous silts. This last sharp event precedes a second major downcutting phase which takes place in the early Postglacial and is followed by a decline in river flow and sediment supply. This evolution reflects a broad regional pattern of fluvial response which illustrates its sensitivity to climatic change. The study of various morphosedimentary contexts shows their influence on the fluvio-dynamic record and bio-proxies which complicates the detection of minor phases.

British late glacial and Holocene climatic history reconstructed from land snail assemblages

gations have enabled refinement of the stratigraphic scheme, as shells of land snails occur in quantity throughout the sequence (Preece, 1998). They provide a detailed mollusk succession from the beginning of the late glacial until the present day. The late-glacial assemblages are dominated by species of open country and marsh, but shadeintolerant species are replaced by a succession of woodland species during the early part of the Holocene. Following forest clearances during the Neolithic and Bronze Age (5000‐3000 yr B.P.), these closed forest communities show a reversion to grassland assemblages, with only minor indications of scrub (Fig. 2). A detailed chronology for this succession is provided by a series of

Quantification and regulation of organic and mineral sedimentation in a late-Holocene floodplain as a result of climatic and human impacts (Taligny marsh, Parisian Basin, France)

Quantification in grams per metres squared per year of the sediment accumulation in a flood plain (‘marsh’) located in the southwestern Parisian basin showed that there is no close relationship between the accumulation of organic matter (OM) and mineral matter (MM) during the late Holocene, and provided an accurate view of the distinct yield and storage conditions of both sediment components. Endogenic OM accumulation in peaty sediments is not related to the climate but to felling of the alder forest and its substitution by Cyperaceae and paludal taxa in the marsh (Iron Age and Middle Ages). MM accumulation expresses mainly the sediment yield on the slopes, determined by landuse. During an initial phase (from the late Neolithic to the early Middle Ages), land-use change from crop cultivation to pastureland, possibly related to climate deterioration, led to a decrease in the sediment yield. During a second phase, since the early Middle Ages, the considerable development of crop cultivation over pasturing, even during periods of climate deterioration (such as the ‘Little Ice Age’), led to a sharp increase in sediment yield. However, although sediment yield was high, the hydrodynamics in the fen did not favour particle retention. Thus, since the Neolithic, yield and storage of OM and MM sediment have been marked by human activities, initially with high climatic stress, but since the Middle Ages without significant climatic stress.

Le Tardiglaciaire du bassin de la Somme : éléments de synthèse et nouvelles données [The Lateglacial from the Somme basin : first synthesis and new data]

The multidisciplinary research on the Lateglacial sequences from the Somme basin (stratigraphy, sedimentology, palynology, malacology, prehistory and 14 C dates) leads to a general overview of the valley evolution between the end of the Weichselian Upper Pleniglacial and the beginning of the Holocene. Important changes in fluvial morphology and sedimentation, related to global climatic variations, are identified. The first major modification of the fluvial morphology is dated from the Upper Pleniglacial / Lateglacial transition (13 000 BP 14 C) : valley response to climatic improvement and vegetation development is marked by an incision and the evolution from a braided channel pattern to a transitional system at the beginning of the Bolling (multichannel). During the Allerod the system is characterised by a large single channel meandering system in which overbank organic silts are deposited. Both the molluscs and the pollen indicate the development of the vegetation but the environment is still relatively open. Between the Bolling and the Allerod, the data from sedimentology, malacology and palynology indicates the occurrence of a short cold phase which is attributed to the Older Dryas (Dryas II). The end of the Lateglacial, is characterised by a very important infilling of the whole valley by fine calcareous silts during the Younger Dryas cold phase. (single meandering channel). A new major incision phase underlines the beginning of the Preboreal around 10 000 BP. Then during the Preboreal the previous channel is progressively fed by organic deposits and by peat. In this framework, the evolution of the local Palaeolithic occupation is characterised by a long hiatus between 23 000 and 13 000 BP ( 14 C), followed by a very important development of the number of settlements during the Allerod (Final Palaeolithic). A new gap is observed during the Younger Dryas cold phase, followed by a come back of the last Upper Palaeolithic people at around 10 000-9 800 BP (Belloisien). The Early Mesolithic is dated at about 9 800 - 9 700 BP.

Une malacofaune nouvelle du Pléistocène moyen à Soucy (Yonne - France): Biogéographie et paléoécologie

Fine alluvial deposits of Middle Pleistocene age at Soucy (Yonne) have yielded abundant and original terrestrial and aquatic malacofaunas including an extinct species of pulmonate gastropod: Aegopis klemmi. This species was known only from early Middle Pleistocene interglacial deposits in central Europe. Composition and evolution of malacological assemblages indicate interglacial conditions. The occurrence of several species of modern central European distribution suggests more continental conditions than at present.

Successions malacologiques du Tardiglaciaire weichsélien : Corrélations entre séries du Nord de la France et du Sud-Est de la Grande-Bretagne [Comparison of lateglacial molluscan successions from northern France and southeastern England]

Three new Lateglacial molluscan successions from the Oise and the Seine valleys are reported and compared with the Somme valley references (Limondin, 1995). Malacological data from northern France and southeastern England Lateglacial sequences show close affinities. The early Lateglacial deposits yield impoverished faunas with abundant Vallonia. The Allerod appears to be a very stable episode with richer and more diverse assemblages. Occurrences of some xerophilous taxa, particularly Helicopsis striata and Trochoidea geyeri, are typical of this period The Younger Dryas cold period is marked by a decrease in the abundance of molluscs and the development of some hygrophilous cold-resistant taxa (Trichia hispida, Succinea oblonga, Columella columella). Consistency of malacological successions over a large area demonstrates that this material can be used for Lateglacial chrono-climatic characterization. This is specially important for a period mainly represented by calcareous deposits leading to the loss of all organic fossils except molluscs.

Middle Pleistocene Human Remains from Tourville-la-Rivière (Normandy, France) and Their Archaeological Context

Despite numerous sites of great antiquity having been excavated since the end of the 19th century, Middle Pleistocene human fossils are still extremely rare in northwestern Europe. Apart from the two partial crania from Biache-Saint-Vaast in northern France, all known human fossils from this period have been found from ten sites in either Germany or England. Here we report the discovery of three long bones from the same left upper limb discovered at the open-air site of Tourville-la-Rivière in the Seine Valley of northern France. New U-series and combined US-ESR dating on animal teeth produced an age range for the site of 183 to 236 ka. In combination with paleoecological indicators, they indicate an age toward the end of MIS 7. The human remains from Tourville-la-Rivière are attributable to the Neandertal lineage based on morphological and metric analyses. An abnormal crest on the left humerus represents a deltoid muscle enthesis. Micro- and or macro-traumas connected to repetitive movements similar to those documented for professional throwing athletes could be origin of abnormality.

Une inhumation sous tumulus de l’Âge du Bronze et une occupation de la fin du Néolithique à Gonesse, La Fosse aux Larrons (Val-d’Oise)

Decouvert fortuitement en 1976 suite a un decapage industriel, un tumulus a couronne de pierres comportant une inhumation centrale a fait l’objet d’une fouille de sauvetage. Situe dans la vallee du Crould au nord de Paris, les diverses etudes environnementales (geoarcheologie, malacologie, palynologie) ont permis de restituer l’evolution du paysage durant le Subboreal et l’insertion des occupations humaines successives. La stratigraphie revele une premiere implantation caracterisee par une couche archeologique partiellement conservee comportant des vestiges ceramiques, lithiques et des restes de faune. Des artefacts de meme nature se retrouvent dans la constitution du tumulus edifie ulterieurement en partie au detriment de cette occupation initiale. L’etude du monument montre en effet un creusement peripherique destine a collecter des sediments pour former un noyau central ceinture d’une couronne de pierres recouverte d’une chape de terre elle-meme surmontee d’un mince niveau organique. Au centre se trouvait un inhume de sexe masculin depourvu de mobilier, objet d’une etude anthropologique detaillee. Les datations 14C, les analyses environnementales et l’examen du mobilier concordent pour situer avec vraisemblance les restes d’habitat au debut du Neolithique final et l’edification du tumulus a la charniere de l’Âge du Bronze ancien et moyen.