Julie Dabkowski 12, Salomé Granai 12, Laurent Brou 3, HenriGeorges Naton 1 1 GéoArchÉon, ViévillesouslesCôtes, France; julie.dabkowski@geoarcheon.fr 2 Laboratoire de Géographie Physique : Environnements Quaternaires et Actuels (UMR CNRS 8591), Meudon 3 Centre national de recherche archéologique, Service d archéologie préhistorique, Bertrange Luxembourg
Belgium Germany France
Belgium Germany France Malacological study by Richard Meyrick (2000) Tufa up to 8 mhigh C14 datings a broad part of the Holocene covered Environmental reconstructions environment dynamic since the Preboreal forest clearance c.1640 ±60 yr BP (17401340 cal. BP)
New coring 45 m of tufa + underlying formations Meyrick s profile (uppermost 4 m only) Aims: Detailed stratigraphic description Underlying fluvial (?) deposits New sampling (malacology, palynology, geochemistry)
Upper profile Detailed stratigraphic profile 54 geochemical samples (continuously every 5 cm) 41 malacological samples (continuously every 10 cm, parallel to geoch. samples) No material for dating Cores Lithologic description 64 geochemical samples (continuously every 5 cm in average) 25 malacological samples (continuously every 1020 cm according to lithology, parallel to geoch. samples) Few material for dating
Cores C2 Dark organic sandy clay (C4) Dabkowski et al., 2015The Holocene
Upper profile Silty white lime mud (shallow pool) Indurate massive tufa (barrier) Dabkowski et al., 2015The Holocene
Upper profile Oncolithic facies (flow deposits) Paleosoils Terra belgica ceramic fragment (Roman occupation: I st or early II d century) Silty white lime mud (shallow pool) Indurate massive tufa (barrier) Dabkowski et al., 2015The Holocene
Upper profile Mature perched springline tufa mount (Pedley,1990; Pedley et al., 2003) Fine sandy tufa to thinly bedded horizontal crusts (paludal conditions) Oncolithic facies (flow deposits) Paleosoils Terra belgica ceramic fragment (Roman occupation: I st or early II d century) Silty white lime mud (shallow pool) Indurate massive tufa (barrier) Dabkowski et al., 2015The Holocene
New interpretations (Salomé Granai, GéoArchÉon) Relative frequency (%) of species Zonation based on ecological criteria Meyrick s data (2000) Abundance (number of shells) of species Zonation based on appearance of specific taxa Shade demanding Mesophile Marshland Aquatic Optimum forest Forest clearance Platyla polita (c. 7500 BP) Open woodland (Boreal forest) Discus rotundatus (c. 8400 BP) Open marsh with shade demanding species virtually absent Marsh with some shade Number of shells
New interpretations (Salomé Granai, GéoArchÉon) Relative frequency (%) of species Zonation based on ecological criteria Meyrick s data (2000) Abundance (number of shells) of species Zonation based on appearance of specific taxa Shade demanding Mesophile Marshland Aquatic Optimum forest Forest clearance Platyla polita (c. 7500 BP) Humid open woodland Open woodland (Boreal forest) Postglacial warming? Pioneer species Increasing moisture Number of shells Discus rotundatus (c. 8400 BP) Open marsh with shade demanding species virtually absent Marsh with some shade
Continuous sampling every 5 cm (UP + cores) 118 samples 4 proxies: Stable isotopes (δ 18 O, δ 13 C) Service de Spectrométrie de Masse Isotopique MNHN, Paris (special thanks to M. Balasse, J. Ughetto and D. Fiorillo) Trace elements ratios (Mg/Ca, Sr/Ca) Laboratoire des Sciences du Climat et de l Environnement CNRSCEAUPVC, Gifs/Yvette (special thanks to E. Douville and L. Bourdier) Temperature (δ 18 O) Humidity conditions as moisture availability (δ 13 C) and rainfall intensity (Mg/Ca, Sr/Ca)
Temperature + + Humidity (rainfalls) Chronology (C14 and biochrono.) 900 ±50BP 1640 ±60BP 8390 ±100BP 9950 ±130BP Confidence intervals: δ 18 O = ±0.08 δ 13 C = ± 0.04 Mg/Ca and Sr/Ca ±3% + Humidity ( Temperature ) + Dabkowski et al., 2015The Holocene Dabkowski et al., unpublished
Temperature + + Humidity (rainfalls) Chronology (C14 and biochrono.) 900 ±50BP 1640 ±60BP 8390 ±100BP 9950 ±130BP Confidence intervals: δ 18 O = ±0.08 δ 13 C = ± 0.04 Mg/Ca and Sr/Ca ±3% + Humidity ( Temperature ) + Dabkowski et al., 2015The Holocene Dabkowski et al., unpublished
Temperature + + Humidity (rainfalls) Chronology (C14 and biochrono.) 900 ±50BP 1640 ±60BP 8390 ±100BP 9950 ±130BP Confidence intervals: δ 18 O = ±0.08 δ 13 C = ± 0.04 Mg/Ca and Sr/Ca ±3% + Humidity ( Temperature ) + Dabkowski et al., 2015The Holocene Dabkowski et al., unpublished
Malacology (new interpretations, S. Granai) Stratigraphy Temperature Geochemistry + + Humidity (rainfalls) Shade demanding Mesophile Postglacial warming? Pioneer species Increasing moisture + Humidity + ( Temperature )
Malacology (new interpretations, S. Granai) Stratigraphy Temperature Geochemistry + + Humidity (rainfalls) Shade demanding Mesophile? Humid open woodland Postglacial warming? Pionner species Increasing humidity + Humidity + ( Temperature )
Malacology (new interpretations, S. Granai) Stratigraphy Paludal Temperature Geochemistry + + Humidity (rainfalls) Shade demanding Mesophile Flow deposits/ Paleosoils Shallow pool? Humid open woodland Postglacial warming? Pionner species Increasing humidity + Humidity + ( Temperature )
Mature perched springline tufa mound (until c. 900 BP) Tufa still precipitating nowadays No late Holocene tufa decline at Direndall Favourable climatic conditions (rainfall intensity) No human impact (despite archaeological evidence of increasing agriculture since the 1 st century) Consistency of environmental and climatic data Increase of humidity (rainfall) / No significant temperature variations Rainfall intensity = main factor driving Holocene forest development To do: New malacological study to precise climate / environment interactions Tufa develops from the Early Preboreal to present day Underlying fluvial deposits assigned to Tardiglacial Direndall = a reference site To do: New C14 dating to strengthen the chronological framework Investigation on underlying deposits (palynology, tephrochronology) Investigation on recent and modern tufa deposits