Environmental Radioactivity, Radon, Isotope Geochronology, Stable Isotope applied to paleoclimate and paleoenvironment, Speleothems, Travertine and Tufa

POSTER: Multiproxy record of environmental and climatic variations during the Eemian from the Northern France calcareous tufa of Caours: combining petrography, malacology and geochemistry.

by Julie Dabkowski

Co-authored with Nicole Limondin-Lozouet, Pierre Antoine, Julian Andrews, Christine Chaussé, Pierre Carbonel, Jean-Luc Locht and Alina Marca-Bell.
Presented at the INQUA Congress 2011 (Bern), in session 69 "Reconstructing environmental impacts of climate changes from MIS 5 to present, based on terrestrial and lacustrine archives".

The site of Caours exhibits a calcareous tufa deposit of >10 000 m2 and up to 3.5 m thick, overlying lower terrace... more The site of Caours exhibits a calcareous tufa deposit of >10 000 m2 and up to 3.5 m thick, overlying lower terrace fluvial deposits of a Somme River (Northern France) tributary. The whole calcareous tufa sequence is attributed to the Eemian Interglacial (MIS 5e) according to its location within the Somme River terraces system, palaeontological data, and U/Th TIMS dating (average of 124 ± 4 ky BP). Since 2005, archaeological excavations of a Middle Palaeolithic site at the base of the tufa formation have provided long stratigraphic profiles (up to 20m long), supporting multidisciplinary studies. Palaeoenvironmental data from a petrographic study and molluscs were compared to geochemical proxies recording temperature (δ18O) and humidity (δ13C and trace elements Mg and Sr).
In thin section the main Cyanobacteria taxa precipiting tufa were identified as the fossil genus Broutinella and Ponsinella. Broutinella built massive “cauliflower” tufas. This subaqueous facies is associated with aquatic molluscs and ostracods. Ponsinella produces the “mille-feuilles” facies with thin laminations testifying of diffuse flow periods. This facies is associated to malacofauna dominated by land snails.
The cauliflower facies is dominant in the lower part of the sequence, where more pluvial conditions are suggested by δ13C data. This wettest part is also the warmest according to δ18O, and corresponds to the expansion of woodland molluscs. Moreover, the maxima of temperature and humidity (from δ18O and δ13C) are correlated with the Climatic Optimum (highest number of forest species diversity and mollusc shells). In the upper part, the mille-feuilles facies becomes better developed as spring flow waned, based on the δ13C data. Dry conditions are also indicated by mollusc fauna which record a landscape of mainly open areas and some forest remnants.
Clear environmental modifications caused by climatic changes are thus reconstructed from the tufa at Caours especially around the Interglacial Optimum.

Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calcite de tufs pléistocène du nord de la France : exemple des séquences de Caours (SIM 5e; Somme) et La-Celle-sur-Seine (MIS 11 ; Seine-et-Marne)

by Julie Dabkowski

Co-authored with N. Limondin-Lozouet, P. Antoine, A. Marca-Bell and J. Andrews.
Published in Quaternaire, 22 (4), 2011

RECORD OF CLIMATIC CHANGES DURING INTERGLACIALS FROM STABLE ISOTOPES IN NORTHERN FRANCE PLEISTOCENE TUFA CALCITE:... more RECORD OF CLIMATIC CHANGES DURING INTERGLACIALS FROM STABLE ISOTOPES IN NORTHERN FRANCE PLEISTOCENE TUFA CALCITE: EXAMPLES OF CAOURS (MIS 5e; SOMME) AND LA CELLE (MIS 11; SEINE ET MARNE).
Tufas are mainly composed of calcite (CaCO3) which makes them suitable for geochemical investigation, especially oxygen and carbon stable isotopes (δ18O and δ13C). These isotopic parameters have already been shown to record temperature and humidity variations in the Holocene tufas, proving their suitability as climatic proxies. This study focuses on two French Pleistocene sites, Caours and La Celle. Results are compared to palaeoenvironmental, especially malacological, data. This comparison shows that δ18O and δ13C in tufas are important proxies of palaeoclimatic variation during Pleistocene interglacials, just as they are during the Holocene.


La composition minéralogique des tufs calcaires, essentiellement constitués de CaCO3, permet l’utilisation d’indicateurs climatiques géochimiques et en particulier l’étude des isotopes stables de l’oxygène et du carbone (δ18O et δ13C). Ces derniers sont déjà bien connus dans les tufs holocènes comme marqueurs des variations de température et d’humidité. L’analyse des isotopes stables a été réalisée ici sur les séquences de tuf pléistocènes de Caours (SIM 5e, Somme) et de La Celle (SIM 11, Seine et Marne). Les résultats de cette étude géochimique ont été comparés aux données paléoenvironnementales, notamment malacologiques. Ces premières analyses montrent que, comme dans le cas des tufs holocènes, les variations des isotopes stables du carbone et de l’oxygène dans les tufs pléistocènes constituent des indicateurs fiables des variations climatiques au cours des interglaciaires pléistocènes.

Petrogenesis of Artifact-Bearing Fossil-Spring Deposits from Kharga Oasis, Egypt

by Kathleen Nicoll

--> Citation: Nicoll, K.; Giegengack, R.; Kleindienst, M.R.; 1999. Petrogenesis of Artifact-Bearing Fossil-Spring Deposits from Kharga Oasis, Egypt. Geoarchaeology: An International Journal. v. 14: p. 849-863.

ABSTRACT Petrographic and geochemical study of artifact-bearing fossil-spring tufas in stratigraphic contexts... more ABSTRACT Petrographic and geochemical study of artifact-bearing fossil-spring tufas in stratigraphic contexts associated with Upper Acheulean and Middle Stone Age-to-historic artifacts provides a basis for characterizing and comparing Quaternary tufa deposition and diagenesis across the Kharga Oasis region of south-central Egypt. Analysis of tufa deposits at Refuf Pass, Midauwara Pass, A‘in ‘Amur, and Umm el Dabadib suggest that the low Mg-carbonates were precipitated by similar inorganic and biogeochemical processes operating within freshwater spring-fed alkaline stream environments throughout Quaternary time. Detailed petrographic studies suggest that the tufas are relatively pristine, with the original rock textures well preserved with minimal postdepositional alteration. Microstratigraphic details indicate that a variety of interformational facies were present within the former stream environments; understanding these contexts is valuable for interpreting prehistoric human activities.

U-series dating and isotope geochemical study of the Gellért Hill (Budapest) travertine

by Sándor Kele