Karstification as geomorphological evidence of river incision: the karst of Cousance and the Marne valley (eastern Paris Basin)

The Cousance karst (located between the valleys of the Saulx and Marne) has been studied to determine the temporal records of river incision in the eastern Paris Basin, around the ANDRA experimental nuclear waste repository. Two generations of karst are recognized. The first is a palaeophreatic karst indicative of an old base level, now uplifted +75 m above the underground streams. It is underlain and drained by a second generation of karst with active sinks, which records the vertical evolution following the entrenchment of the River Marne. Ten U/Th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes, mainly during isotopic stages 3 and 5 (between 102.4 ± 1.2 and 49.4 ± 0.4 ka bp ) but also during isotopic stage 2 at 16.3 ± 0.1 and 20.9 ± 0.3 ka bp . These dates provide an absolute age limit for the start of vertical development of the karst, at the latest during isotope stage 5c.     

Palynological Analysis of Amber-Bearing Clay from the Lower Cretaceous of Central Lebanon

An amber-bearing lignitic layer of sandy clay from the Lower Cretaceous of Central Lebanon (Mderej-Hammana)yielded a well-preserved,moderately variegated palynoflora,which origin is mixed between land plants and marine microflora.Its detailed analysis led to fulfill its inventory,to propose a paleoenvironmental reconstruction,and to draw the paleoclimate which prevailed over the region:an estuarian area under a rather humid,temperate climate;a variety of ferns grew near the shore-side and in the inward l...     

Speleothem evidence of warm episodes in northeast France during Marine Oxygen Isotope Stage 3 and implications for permafrost distribution in northern Europe

U-Th ages have been obtained by TIMS on the growth periods of a stalagmite from the “Grotte des Puits de Pierre-la-Treiche” (northeastern France), during the middle part of the “Weichselian glaciation” (Marine Isotope Stage 3), between 55.36 ± 0.95 and 53.34 ± 0.49 ka and around 45.85 ± 0.49 ka. These episodes are contemporaneous with abrupt climatic variations recorded in Greenland ice cores (Greenland interstadials 12, 14 and 15) that have been previously recognized in European speleothems. They also coincide with two interstadials, known as “Goulotte” and “Pile” in the Grande Pile pollen sequence (eastern France), which have been correlated with the Moershoofd complex in the Netherlands. Such evidence of speleothem deposition related to temperate episodes gives a strong indication of the absence of continuous shallow permafrost during the middle part of MIS 3 in northeastern France.     

Early Aptian productivity increase as recorded in the Fourcade level of the Ionian zone of GreecePaléoproductivité élevée enregistrée dans le niveau Fourcade de l'Aptien inférieur en zone ionienne (Grèce)

The Mid-Cretaceous ‘upper siliceous zone’ of the Vigla Limestone is studied in detail along the Paliambela section of northwestern Greece. Within it two radiolarite horizons can be identified, the lower being rich in organic matter and named herein as the ‘Fourcade level’. The preserved organic matter is of planktic/bacterial origin and of low thermal maturity. The nannoflora contained within the lower marly argillites consists of a poorly preserved and oligospecific assemblage characterised by the total absence of Nannoconids. Radiolarian assemblages yielded from the Fourcade level are dominated by the family Archaeodictyomitridae. Integrated calcareous nannofossil and radiolarian biostratigraphic results suggest an Early Aptian age for the Fourcade level, which can be thus considered as the local expression of the globally recognised Early Aptian Oceanic Anoxic Event (OAE 1a). To cite this article: T. Danelian et al., C. R. Geoscience 334 (2002) 1087–1093.     

Assessment of shallow groundwater in Lake Nyos catchment (Cameroon,Central-Africa): implications for hydrogeochemical controls and uses

In 1986, carbon dioxide gas exploded from Lake Nyos and killed about 1,800 people. After that disaster, various administrative and research activities have been conducted to mitigate subsequent disasters. However, none of those endeavors have characterized the groundwater chemistry to identify hydrogeochemical processes that control the water chemistry, and the quality of the water for domestic and agricultural uses that support the lives of un-official resettlers around Lake Nyos. Conventional hydrochemical techniques coupled with statistical and graphical analysis were therefore employed to establish the baseline hydrochemical conditions, assess processes controlling solutes distribution in shallow groundwater in the Lake Nyos catchment and explore its usability. Groundwater samples were analyzed for their physical and chemical properties. The wide ranges of electrical conductivity and total dissolved solid values reveal the heterogeneous distribution of groundwater within the watershed. The relative abundance of major dissolved species was Ca > Mg > Na > K for cations and HCO₃ >>> Cl > SO₄ > NO₃ for anions. Piper diagram classified almost all water samples into mixed CaMg–HCO₃ water type. Major ion geochemistry reveals that, in addition to silicates weathering (water–rock interaction), ion exchange processes regulate the groundwater chemistry. Principal component analysis supports the occurrence of water rock interaction. Hierarchical cluster analysis showed that the chemistry of groundwater in the study area is controlled by three main factors, and suggests no hydraulic connectivity between deep lake water and groundwater in the catchment. The quality assessment of the groundwater showed that groundwater parameters are within the acceptable limit of the World Health Organization and Nigeria guidelines for drinking and domestic uses, and water found to be good for irrigation.     

Urban water stress and poor sanitation in Ghana: perception and experiences of residents in the Ashaiman Municipality

Access to safe and adequate water and to sanitation has been a global developmental priority due to their intrinsic impacts on the achievement of the sustainable development goals. Despite the implementation of several measures to improve access to safe water and sanitation, urban dwellers in Ghana struggle to acquire water and access sanitation facilities. This paper identified and examined the vulnerable conditions of households to environmental inadequacies of potable water and sanitation and measures aimed at reducing the risks associated with them in the Ashaiman Municipality. The study revealed that, access to adequate water supply was not necessarily dependent on the physical location of house units, but on factors such as lack of building permit, financial constraints, rental conditions, administrative procedures and ill-suited housing arrangement. Inadequate solid and liquid waste management practices and poor drainage systems were major problems identified in the Municipality. The paper argues that water, drainage systems and logistics for waste management in deprived communities must be provided by the local government and service providers through public–private partnership agreements. We conclude that, planning rules, regulations and procedures should be strictly adhered to and vigorously enforced by the Municipality in order to have a well-organized and planned urban environment.     

Evolution of Çamlık fissure-ridge travertines in the Başkale basin (Van,Eastern Anatolia)

Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Ba?kale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Ba?kale basin is located between the Ba?kale Fault Zone (BFZ) characterised by Çaml?k fault and I??kl?–Zirani? fault. It is located between dextral Yüksekova Fault Zone and southern end of dextral Guilato–Siahcheshmeh–Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Çaml?k fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Çaml?k fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.     

A new biostratigraphic correlation for Late Cretaceous–Paleocene strata of the Gulf of Guinea: Evidence from dinoflagellate cysts

A new biostratigraphic correlation for Late Cretaceous and Palaeocene strata of the Côte d’Ivoire–Ghana continental margin has been developed from the identification of significant dinoflagellate cyst events in ODP Hole 959D. The Late Cretaceous stage boundaries are mostly consistent with previous studies. However, the Maastrichtian/Danian boundary is placed much lower than previously recognized on the basis of the first occurrences of Carpatella cornuta and Damassadinium californicum. The base of the Selandian is recognized from the last occurrence of Cerodinium diebelii and the first occurrence of Adnatosphaeridium multispinosum. The base of the Thanetian is recognized from the first occurrence of Areoligera gippingensis. The rarity of the age-marker taxa is the main reason for different age determinations among studies of the same section.     

Early diagenesis impact on precise U-series dating of deep-sea corals: Example of a 100-200-year old Lophelia pertusa sample from the northeast Atlantic

Deep-sea coral has proved useful for paleoceanographic reconstructions and for documenting ¹⁴C-ages of water masses using ²³⁰Th-ages. However, for precise and accurate U-series dating, further information on coral-age structure, growth rate and diagenetic evolution is still needed. To document such processes, we used U-Th-²²⁶Ra systematics in a 40 cm diameter, Lophelia pertusa specimen collected in 1912 from the Eastern Atlantic (Sea of the Hebrides). External parts of the specimen are thought to have been alive when collected whereas more internal parts were likely dead. The “live-collected” and “dead” parts of the skeleton were sampled and analyzed for their ²³⁰Th, ²³²Th, ²³⁴U, ²³⁸U, ²²⁶Ra and Ba contents by thermal ionization and multicollector inductively coupled plasma mass spectrometry. ²³⁰Th/²³⁴U ratios in the most recent parts yielded ages of 86 ± 6 a and 92 ± 9 a, in agreement with the date of recovery. The older parts yielded ²³⁰Th ages ranging from 169 ± 15 to 211 ± 10 a (n = 5), but had a 31% higher U content than more recent parts of the skeleton. This raises concerns about the possibility of secondary diagenetic U uptake, although an environmentally controlled U/Ca shift between coral growth stages cannot be ruled out. ²²⁶Ra/Ba measurements were made, and model- ²²⁶Ra/Ba ages averaging 250 ± 12 yr were calculated for the older part, assuming a constant initial ²²⁶Ra/Ba ratio in bottom waters. These ages are slightly older than ²³⁰Th-ages, suggesting either that ²²⁶Ra/Ba ratios of ambient-seawater changed over time or that a diagenetic phenomenon have affected the U-series system, or both. Scanning electron microscope observations revealed bioerosion and secondary biomineralization in the older part of the coral skeleton, supporting the hypothesis that diagenetic processes may have influenced the ages obtained by the U-series toolbox. Modeled U-series ages for such an open system are discussed. However, a comparison between ¹⁴C- and ²³⁰Th-ages performed on both pristine and bioeroded parts of the coral gives coherent values (ca 450 a) for the preindustrial ¹⁴C-reservoir age of North Atlantic waters. It remains to be determined, however, whether diagenesis occurs rapidly over a short period of time, or whether it continues for longer periods. In the latter case, diagenetic processes would hamper paleoceanographic interpretations as well as the precise calculation of ¹⁴C ages of deep-water masses, based on comparative U/Th- and ¹⁴C-chronologies.