Reddish Layer Research Articles

Laterally-continuous dolomite layers of the Miocene Pisco Formation (East Pisco Basin, Peru): A window into past cyclical changes of the diagenetic environment

Along the Peruvian coast, the sedimentary succession of the East Pisco Basin is exposed in the Ica Desert. At Cerro Los Quesos, laterally continuous dolomite layers characterise the diatomaceous sediments of the P2 sequence of the Miocene Pisco Formation, where a large number of marine vertebrates are exceptionally preserved, many enclosed in dolomite nodules. In this work, cemented layers from this sequence were described and sampled for petrographic, chemical, microscopic and isotopic analyses. Dolomite occurs in continuous 10–50 cm thick well cemented layers, formed by sediment of different nature: biogenic, terrigenous, volcanoclastic, and phosphatic. The underlying sediments exhibit a yellow layer with sparse dolomite crystals, a black layer with abundant Mn-oxides, and a reddish layer rich in Fe-oxides, indicating redox-related fronts. Two generations of dolomite can be recognised: an early diagenetic microcrystalline one, and a sparry one, filling the large cavities. As observed in both thin sections and on broken surfaces, microcrystalline dolomite also fills the inner spaces of the diatom areolae replicating their finest ultrastructure, such as foramina and cribra and replace calcite shells of foraminifera. δ18O and δ13C values from the microcrystalline dolomite of two layers, selected based on the absence of other carbonate phases (e.g. calcite) and the lack of sparry cement, are in agreement with those reported for the Peru margin and fall in the fields of either sulphate-reduction or methanogenesis.All the data point to dolomite precipitation associated with low-temperature early diagenesis that typically occurs in upwelling settings, where high surface water productivity is responsible for high rates of organic carbon flux to the sea bottom and for the cyclical oxygen depletion at the bottom. Such conditions also promote high abundances of marine vertebrates and the exceptional preservation of their skeletons in the sediments.

Environmental changes revealed by Lower–Middle Ordovician deeper-water marine red beds from the marginal Yangtze Platform, South China: Links to biodiversification

The origin of reddish nodular limestone in the Zitai Formation, a deeper-water type of marine red beds (MRBs) distributed along the marginal Yangtze Platform, South China, is enigmatic. Here we focus on the red colorations through sedimentological, mineralogical and geochemical analyses, as exemplified by the Zitai Formation at the Xiangshuidong section, Songzi City, Hubei Province and the Daling section, Shitai City, Anhui Province. Limestones studied here can be gray, green or red. The grayish limestones are generally below the reddish and/or greenish limestones, whereas the greenish layers are associated with reddish layers in forms of homogenous, banded or mottled limestone. Hematite that is fine and poorly crystalized could be the coloration mineral for the Zitai MRBs, which is largely caused by increased terrigenous iron, when the bottom seawater was oxic. Except that the irregularly banded and mottled reddish-greenish limestone are of a possible diagenetic origin, the primary greenish limestones are related to relatively reducing conditions compared with reddish limestones, as a result of eustatic changes or other fluctuating environmental factors. During this time interval, the Great Ordovician Biodiversification Event (GOBE) was facilitated by highly oxic seawater indicated by MRBs in South China, Baltica and Sibumasu, but the diachroneity of radiations in South China could be ascribed to increased terrigenous supply, emphasizing that regionally environmental factors might be critical for biological radiations at the early stage of the GOBE.

Campanian to Danian dinoflagellate cyst assemblages from the southwestern Tethyan margin (Tattofte section, western External Rif, Morocco): Biostratigraphic and paleobiogeographic interpretations

A palynological study of the Upper Cretaceous–lower Paleocene outcrop section at Tattofte (westernmost External Rif, Morocco) has produced a well-preserved palynological assemblage rich in dinoflagellate cysts (dinocysts). For the first time, these assemblages have allowed us to determine the age of this section, to highlight a new Cretaceous–Paleogene boundary, and to make paleobiogeographic interpretations. The samples analyzed yielded 209 dinocyst species and 81 biostratigraphic dinocyst events (first occurrence, or FO, and last occurrence, or LO). We recognized the upper Campanian based on the FOs of Areoligera coronata, Areoligera reticulata, Areoligera senonensis, Cerodinium diebelii and Andalusiella mauthei subsp. mauthei, as well as the LOs of Batiacasphaera solida, Odontochitina costata, Odontochitina porifera, Sentusidinium eisenackii, Trichodinium castanea and Trithyrodinium suspectum. The lower Maastrichtian is determined by the FOs of Isabelidinium bujackii, Palaeocystodinium golzowense and Trithyrodinium evittii, and by the LO of Alterbidinium acutulum, and the upper Maastrichtian is recognized primarily by the FOs of Cerodinium speciosum subsp. speciosum, Disphaerogena carposphaeropsis, Glaphyrocysta perforata and Manumiella seelandica and the LO of Dinogymnium spp. The Danian is recognized on the basis of the FOs of several taxa, including Carpatella cornuta, Danea californica and Senoniasphaera inornata. The succession of the dinocyst events in the uppermost part of the studied interval has revealed a relatively complete record across the Cretaceous–Paleogene boundary. The Cretaceous–Paleogene boundary coincides with a 8 cm-thick reddish layer, which resembles those observed previously in the Cretaceous–Paleogene boundary reference sections in the Mediterranean area, most notably the Cretaceous–Paleogene boundary stratotype at El Kef (Tunisia). The upper Campanian dinocyst assemblage indicates a subtropical to temperate setting, while the Maastrichtian and lower Danian assemblages indicate a subtropical to warm temperate setting. The incursion of a few higher latitude cold-water dinocyst species in these provinces during the latest Campanian and around the Cretaceous–Paleogene boundary may suggest a southward migration of these species, probably related to short cooling episodes and ocean circulation.

Monitoring Ex Situ Electrokinetic Remediation (EKR) using Nitric Acid as Chelating Agent

Heavy metal has become a serious world crisis due to natural and man-made sources. Zinc contamination in soil is caused by world urbanization and modernization. The Electrokinetic Remediation (EKR) is a green technology aiming at removing zinc contaminated soils. This paper aims to compare the electrokinetic process between Pure System and Nitric acid as chelating agents. The ex situ remediation method using soil box successfully demonstrated that nitric acid which attracted artificial contaminated zinc had been precipitated at the vicinity of cathode terminal in a form of reddish layer. In conclusion, nitric acid is highly recommended as solution for enhancing electroosmosis process.

Quantitative analysis of planktonic foraminifera across the Cretaceous-Paleogene transition and observations on the extinction horizon, Haymana Basin, Turkey

The Haymana Basin, Turkey, hosts complete record of sedimentation across the Cretaceous-Paleogene (K-Pg) boundary. To examine the K-Pg boundary transition and delineate the bioevents, two consecutive sections (UH and UKHB) were measured and sampled at high resolution. Three biozones were established: Plummerita hantkeninoides, P0 and Pα. A detailed quantitative study on planktonic foraminifera was carried out for the P. hantkeninoides and the P0 zones for 63–150 μm and >150 μm size fractions. Results show dominance of ecological generalists with small, simple tests over ecological specialists with large, robust, ornamented morphologies. Heterohelicids are the most dominant group on both size fractions throughout the late Maastrichtian, however right after the K-Pg boundary Guembelitria cretacea blooms and dominates the planktonic foraminiferal assemblage in early Danian P0 Zone. The K-Pg boundary characterizes itself as 2–3 mm thick reddish oxidized layer and its transition reveals a series of events: A rapid change in sedimentation from Maastrichtian mudstones to Danian marls. A sudden annihilation of large, ornamented ecological specialists (e.g., Globotruncana, Rugoglobigerina, Planoglobulina) right at the reddish layer (even though quantitative study revealed that there is a systematic reduction in the foraminiferal species richness throughout the P. hantkeninoides Zone). Spikes of calcareous dinoflagellate Thoracosphaera and fecal pellets right after the K-Pg boundary in the Danian P0 Zone. Anomalous increase in CaO rich spherules and amorphous grains coupled with barite crystals right at the K-Pg boundary layer. Paleobathymetric calculations also revealed approximately 400 m paleodepth for the study area corresponding the upper bathyal zone.

Structural variation and the development of thick rhyolite lava: A case study of the Sanukayama rhyolite lava on Kozushima Island, Japan

Geological studies of ancient rhyolite lavas are required for understanding flow dynamics because rhyolite lava eruption is an infrequent event. The Pleistocene Sanukayama rhyolite lava is about 130 m thick and located on Kozushima Island, Japan. Vertical sections of the lava are well exposed in the sea cliff and in a dissected valley, providing a good opportunity for the elucidation of the internal structural variations. The vertical lithofacies variations are classified into three zones of pumiceous, obsidian, and crystalline from the top to the base, respectively. The exposed area is considered to correspond to the upper half of the lava. In the boundaries between each zone, the lithofacies are mingled rather than exhibiting gradual change. This indicates that rheological contrasts are arisen within the lava due to differences of vesicularity and/or crystallinity. Various heterogeneous structures are recognized throughout the lava such as obsidian and reddish layers in the pumiceous zone, strongly deformed white-colored bands and a clastic layer in the obsidian zone, and dark-colored bands in the crystalline zone. We demonstrate on the basis of geological evidences and magnetic studies that these heterogeneous structures originated mostly from shear-induced fracturing within the advancing lava. This study indicates that brittle lava fracturing during ductile-brittle transition likely governs the acceleration of rhyolite lava heterogeneity.

Characteristics, nature, and formation of palaeosurfaces within dunes on Fuerteventura

AbstractThe appearances of palaeosurfaces intercalated into palaeo-dune fields on Fuerteventura are multifaceted. Although reddened layers in these dune sediments might suggest that strong soil-formation processes have taken place, the combination of aridity and parent material, namely biogenic carbonate sand of shelf origin, reveals that strong soil formation seems unlikely. These sediments rather represent de- and recalcification processes only. Solely in the case of admixed material of volcanic origin and dust deposits further soil-forming processes seem to be possible. Hematite-rich Saharan dust contributes to reddish colouration of the palaeosurfaces. In addition, CaCO3-coated iron particles appear to be ingredients of dust being leached after deposition and transformed to hematite. Overall, we propose much weaker soil-forming processes during the Pleistocene than previously postulated. Our findings support the relevance of local environments. Carbonate sands of shelf origin hinder strong soil formation and the reddish layers separating dune generations are palaeosurfaces, which mainly consist of Saharan dust. After deposition of allochthonous material, these layers are overprinted by weak soil-forming processes. The formation of palaeosurfaces primarily depends on morphodynamically stable periods during limited sand supply. Our data suggest a cyclicity of processes in the following order: (1) sand accumulation, (2) dust accumulation and weak soil formation, and (3) water-induced erosion. For the Canary Islands, we support the assumption of glacial maxima being periods of increased levels of moisture. In combination with rising sea level, we propose that favorable conditions of surface stability occur immediately after glacial maxima during periods of starting transgression, whereas regression periods immediately after sea-level high stands seem to yield the highest sand supply for the study area.

Vertical Variation of Lead Content in Sediment Collected from Man‐made Tamagawa Dam Lake in Akita Prefecture, Japan

AbstractAlternation layered lake sediment that had accumulated over a period of 22 years, from 1990 to 2012, was collected from the Tamagawa Dam Lake, which is located in the northeastern part of Akita Prefecture. The lake water is acidified (pH = 4.1) by the inflow of high‐acidic thermal water (pH = 1.2) from the Obuki Hot Spring, the main hot spring in the Tamagawa Hot Spring area. The vertical variations in Si, Al, Fe, Ti, and Pb contents of the sediment were determined by XRF, EPMA, and LA‐ICP‐MS in order to clarify the sedimentation processes of the lake sediment. The layers consisting of the sediment could be mostly classified into three types: dark brown, yellowish brown, and reddish layers. The contents of Si, Al, Fe, and Ti corresponded to the variation in color of each layer in the sample. Based on the Si, Al, and Fe contents in the sediment of Tamagawa Dam Lake, the sources of these elements were classified as detrital origin in dark brown and yellowish brown layers (Si, Al, and Ti) and chemical precipitate origin in reddish layers (Fe). Detrital components were derived from volcanic rocks in the watershed of Tamagawa Dam Lake. The variation of Pb content did not accord with the color of layers. The content of Pb in the sediment of Tamagawa Dam Lake ranges from 45 to 522 ppm. The vertical variation of Pb content in sediment corresponded to the temporal variation of Pb content in thermal water from the Obuki Hot Spring from 1990 to 2012. A large influence of hydrothermal activity of the Tamagawa Hot Spring on the vertical distribution of Pb was found during the active period of the Obuki Hot Spring, resulting in high Pb content within layers at 5–8 cm from the bottom of the sample. T‐Fe2O3‐rich reddish layers were also found in this range. Therefore, it is assumed that T‐Fe2O3 and Pb originated from Obuki Hot Spring and precipitated in Tamagawa Dam Lake. However, no correlation was found between T‐Fe2O3 and Pb contents for any of the dark brown, yellowish brown, and reddish layers. Some layers with high Pb content were also found to have high SiO2 and Al2O3 contents. These findings indicate that there are several possibilities for the sedimentation process of Pb. The sedimentation of Pb as well as that of T‐Fe2O3 in Tamagawa Dam Lake provides a good example of the accumulation of elements by chemical precipitation away from the source of elements.

Eocene paleosols on King George Island, Maritime Antarctica: Macromorphology, micromorphology and mineralogy

We investigated the origin of reddish layers between basalt flows in an Early Eocene volcanic succession in King George Island, Maritime Antarctica. Previous studies in the area classified these layers as regolith surfaces, baked zones and paleosols, but the properties of these layers and the reasons for their classification are not clarified. Since the Early Eocene epoch was one of the warmest phases on Earth during the Cenozoic, a proper investigation of these layers is crucial to obtain additional regional information about the paleoenvironment.The focus of this study is on three profiles located in the Admiralty Bay on King George Island. They were classified as paleosols based on field, micromorphological and mineralogical properties. Main soil forming processes identified by micromorphological analyses were clay neoformation, pedo-/bioturbation and a weak redoximorphosis. The occurrence of plant residues in all profiles was a reliable indicator that these soils formed a land surface during the Early Eocene. Abundant weathered volcanic glass and pyroclasts may indicate andosolization although the main diagnostic features for Andosols, which are the presence of nanocrystalline minerals and organic matter accumulation, were not detected or only in small amounts, respectively. The long-term burial of the paleosol could be a reason for lacking of these diagnostic features. Clay minerals associated with moderately weathered volcanic soils (smectite) were detected in the X-ray diffraction analysis. A predominantly reddish colour of most of the soil horizons is given by hematite, confirmed by the determination of pedogenic oxides. Nevertheless, rubification was not solely a result of pedogenesis but also of reddening of oxyhydroxides by dehydration during diagenesis. Other diagenetic processes were burial compaction, loss of organic matter and induration. In the horizons directly buried by a basalt flow, voids were filled by zeolite crystals, an effect related to lava cooling. Another possible diagenetic effect was the geochemical rejuvenation and homogenization of the profiles. Despite the occurrence of these features, the results are in agreement with previous studies, indicating a humid temperate paleoclimate for King George Island during the Early Eocene.

Late Quaternary pedogenesis of lacustrine terraces in Gallocanta Lake, NE Spain

Transitional areas of lake margins are complex environments whose evolution is strongly controlled by flooding frequency and persistence. The edaphic development of lacustrine marginal environments can be reconstructed by combining detailed geomorphological analysis with a systematic edaphic study of toposequences. This approach has been applied to a set of recent lacustrine terraces in the downwind palustrine area of the Gallocanta saline lake, located in a semiarid area in NE Spain. Up to five terraces, from 1.6 to 4.5m above the lake bottom, have been identified and mapped using stereo photointerpretation and airborne LiDAR data. Several cycles of water level fluctuations, as part of a general trend towards lake desiccation, have generated stepped terrace levels. The soils of these terraces have different morphological characteristics and provide evidences for the Gallocanta paleolake being larger than that of the present day. The soils have a sandy loam texture with variable clay content (1% to 46%) and a predominantly carbonate composition (mean=26%). The soils are developed in a sequence of lacustrine carbonate-rich (mean=37%) fine-grained gray layers overlaying detrital (mean=51% gravels) and frequently erosive, carbonate-poor reddish layers. The pedogenesis of the downwind palustrine area is mainly characterized by poorly-developed carbonate accumulations and common redox mottles associated with water level fluctuations in the lake, which continuously rejuvenate or truncate the soils. Integrating pedological and geomorphological features provides insight into recent complex lacustrine and soil forming processes and facilitates management strategies and plans for this protected saline environment.

Electrochemical study of the corrosion behaviour of carbon steel in fracturing fluid

Corrosion behaviour of carbon steel (K-55) in fracturing fluid was studied with a rotation cylinder electrode, under static and rotation conditions by means of several electrochemical techniques which are as follows: open circuit potential (OCP) decay, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The corrosion rate was determined by weight loss measurements. The electrode surface after a prefixed immersion time was characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that carbon steel showed anodic dissolution behaviour that increased under rotating condition. The cathodic polarisation current density also increased with the electrode rotation due to the increased oxygen diffusion on the electrode surface. Two different oxide layers were formed: a dark, thin layer of magnetite tightly adhering to the electrode surface, characterised by localised corrosion spots, and a porous reddish layer of poorly adhering hematite (Fe2O3) and maghemite (γ-Fe2O3). Under higher rotation rate, the developed oxide layer was not so stable, owing to the shear stress induced between the solution and the specimen surface, enhancing the corrosion rate.

Climate and environmental changes recognized by micromorphology in Paleolithic deposits at Arene Candide (Liguria, Italy)

The lowermost part of the stratigraphic sequence of the Arene Candide Cave, a key Upper Palaeolithic site in Italy, attests to significant climate and environmental change at the beginning of the Late Pleniglacial in coastal Liguria (Northwest Italy). These archaeological layers were studied using a suite of mineralogical and chemical technique including a contextual sedimentological analysis (micromorphology). This study shows that the lower layers are dominated by cryoclastic sediments covered by cyclically organized blackish and reddish layers, or lenses. The black layers mainly consist of bird and bat guano deposits, interfingered with thin brownish sandy-silt layers of aeolian origin, that contain large amount of Ca phosphate. In contrast, the bright red layers are rubified sediment due to Fe re-oxidizing in insoluble form. In these layers evidence of syngenetic freeze-thaw cycles, associated with gelifluction processes, indicates a cool episode in a (semi) arid periglacial environment coupled to an increase in humidity between ca. 31 and 27 ka cal BP. Subsequently, the occurrence of features associated with repeated runoff and debris flow processes that caused a significant accumulation of poorly layered and sorted materials in the overlying sediments indicates a further intensification of humid conditions and reflects a longer phase of more humid and temperate climate. This change from arid to semiarid/humid climates resulted in an increase in sediments resulting from the erosion of Pliocene marine terraces and soils located outside the cave. The identification in the studied sequence of guano layers and the scarcity of artefacts, in conjunction with an absence of clear cultural micromorphological evidence, support an interpretation of sporadic human occupation of this part of the cave during Middle Upper Palaeolithic (Gravettian). Therefore, the finding in such a context of the lavish ceremonial burial of the so called "Young Prince" may suggest that the cave was used as a special place for burials at that time.

Sp608 Successful Mucosal Transplantation from Stomach to Esophagus for Stricture Prevention after Widespread Circular Endoscopic Submucosal Dissection (ESD) For Early Esophageal Squamous Cell Carcinoma - Report of a First Case in Man with 1 1/2 Year Transplant Survival

Secondary stricture formation is the major drawback for resections >3 cm or more than 75% of the esophageal circumference at esophageal ESD. In March 2011 we embarked on animal experiments regarding esophageal resection and re-transplantation of esophageal and gastric mucosal patches in pigs under an approved protocol (NLVL No: 33-42502-06/1151) for stricture prevention. CASE REPORT: A 72 y old man with swallowing difficulty (DG1); tabacco use of 20 py until >15 y ago. Prior rectal resection with sigma anus praeter for a T2 distal rectal cancer. EGD: Suspicion of early squamous cell cancer (Paris IIa; EUS UT1a, m, N0), >75% circum-ferential tumor spread within the cervical esophagus and upper sphincter area (17-25 cm aborally). Biopsy: SC HG-IEN. On April 13, 2011 we performed an EGD under general anesthesia with tracheal intubation with first tubular ESD over 10 cm from the lower hypopharynx through the UES from 17-27 cm followed by a 9x4 cm ESD in the gastric antrum. The healthy gastric specimen retrieved was cut longitudinally into 3 mucosal stripes that were attached to the denuded esophageal muscular layer by means of hemoclips. The stripes were gently pressed against the wall by a non-covered self-expanding metal stent with the intent to allow also a luminal nutrition of the specimen. The sphincter area of 1.5 cm length had to be spared. The esophageal specimen showed a non-invasive low horny early squamous cell cancer (pT1a G2 L-, V-) and curative resection (R0; invasion depth of lamina propria max. 150 microns). Stent removal was performed at day 20 and was cumbersome due to local mucosal hyperplasia. However, multiple islets of gastric mucosa had successfully grown at the esophageal resection site. The patient was discharged on day 24 and regularly seen as outpatient. We observed a stepwise circular spread out of the reddish layer over an area of 5-6 cm within the next 6 months. Stenosis was successfully prevented. Biopsy proved antral HP-negative mucosa. 1 1/2 years later the patient is free of complaints. This first case of a successful gastro-esophageal endoscopic mucosal transplant with one year follow-up after wide- spread ESD in the esophagus for an early squamous cell cancer opens a new perspective for systematic research in this field.

Successful mucosal transplantation from stomach to esophagus for stricture prevention after widespread circular endoscopic submucosal dissection (ESD) for early esophageal squamous cell carcinoma – report of a first case in man with 1 year transplant survival after preliminary animal experiments in the pig

ESD in the esophagus is an expert technique for ‘en bloc’ resection of mucosal cancers >2cm in size. I can provide a quasi-surgical specimen and significantly reduces the risk of local recurrence compared to piecemeal EMR. However, secondary stricture formation is the major drawback for resections >3cm and of more than 75% of the esophageal circumference. Multiple bouginage sessions or temporary stent placement may be required limiting the QoL. Experimental approches include transplantation of buccal or dermal cell grafts as well as systemic and local steroid applications. However, clinical experience is very limited so far. Since march 2011 be had been performing animal experiments concerning esophageal resection and re-transplantation of esophageal and gastric mucosal patches in pigs under an approved protocol (NLVL No: 33–42502–06/1151) with first preliminary but encouraging results when the following clinical presented. Case report: A 72 y male pat. with swallowing difficulty; tabacco use of 20 py until >15y ago. Prior rectal resection with sigma anus praeter for a T2 distal rectal cancer. EGD: Suspicion of early squamous cell cancer (Paris IIa; EUS UT1a, m, N0), >75% circum-ferential superficial tumor spread within the cervical esophagus and upper sphincter area (17–25cm aborally). Biopsy: SC HG-IEN. Discussion of the different treatment options in our interdisciplinary tumor board and with the patient: tubular endoscopic resection alone with 80–100% stricture probability, thermal ablation, radical surgery, primary chemoradiation or an experimental approach as compassionate use with primary ESD in the esophagus and secondary gastro-esophageal mucosal patch transplantation. On April 13, 2011 we performed an EGD under general anesthesia with tracheal intubation with first tubular ESD over 10cm from the lower hypopharynx through the UES from 17–27cm followed by a 9×4cm ESD in the gastric antrum. The healthy gastric specimen prelieved was cut longitudinally into 3 mucosal stripes which were attached to the denuded esophageal muscular layer by means of hemoclips. The specimen were gently pressed against the wall by a non-covered self-expanding metal stent to allow luminal and vascular nutrition of the specimen. The sphincter area of 1.5cm length had to be spared in order to not compress the lower larynx with the stent and to avoid unsupportable pain for the patient. After a control the following day the patient could be extubated. The esophageal specimen showed a non-invasive low horny early squamous cell cancer (pT1a G2 L-, V-) and and curative resection (R0; invasion depth of lamina propria max. 150 microns). Stent removal was performed at day 20 pp and was cumbersome due to local mucosal hyperplasia. However, multiple islets of gastric mucosa had successfully grown at the esophageal resection site. The patient was discharged on day 24 and regulary seen as outpatient. We observed a stepwise circular spread out of the reddish layer over an area of 5–6cm within the next 6 month and successful prevention of stenosis. Biopsy proved antral HP-negative mucosa. Unfortunately a 1–1.5cm non-transplant covered segment in the sphincter area showed a repetive tendency to stricture formation serving quasi as ‘natural’ control and requiring multiple ambulatory bouginage treatments but allowing a (semi-) solid diet without restrictions for most food products (DG1). Conclusions: The so far unique case of a gastro-esophageal endoscopic mucosal transplant with one year follow-up after wide-spread ESD in the esophagus for an early squamous cell cancer opens a new perspective for systematic research in this field.

The importance of U-series disequilibrium of sediments in luminescence dating: A case study at the Roc de Marsal Cave (Dordogne, France)

A multidisciplinary study of the Roc de Marsal Cave gave us the opportunity to re-examine the known problem posed by U-series disequilibria in sediments in the field of palaeodosimetric dating. Apart from burnt flints and heated limestones, the material being dated, THAT IS our principal concern here, is made of burnt sediment samples collected from a reddish layer that forms the very base of the Roc de Marsal Mousterian sequence (Couche B). U-series disequilibria of long life nuclides in sediments were observed: as a general trend, the activity of 238U is greater than that of 226Ra. Important discrepancies in age determination can occur according to the origin of the disequilibrium and its kinetics. To characterise these ancient modifications of radioactivity and constrain the range of possible variations of annual doses, a statistical study of 238U, 226Ra and 232Th activities, measured by gamma spectrometry, was carried out. It shows that the sediment was mainly enriched in mobile uranium. This conclusion is in accordance with the results of complementary measurements of 230Th and 234U performed by alpha spectrometry. On the kinetics side, two models of time-variation of U and daughter concentrations are compared, taking experimental data into account. A detailed presentation of the methodology and the method of calculation of dose rates, and particularly time-averaged dose rates in such a situation, is given.

Revised astrochronology for the Aim el Beida section (Atlantic Morocco): No glacio-eustatic contrpl for the onset of the Messinian Salinity Crisis

Glacio-eustatic sea level lowering has often been proposed as a key mechanism for explaining the onset of the Mediterranean evaporites during the Messinian Salinity Crisis (MSC). To examine the role of glacio-eustacy during the progressive isolation of the Mediterranean in more detail, we reinvestigated the Ain el Beida quarry section that is located at the Atlantic margin of Morocco and therefore free of destructive MSC-related complications. The section consists of deep marine, cyclically bedded (reddish/beige), silty marls of late Messinian age. The reddish layers reveal the same characteristic signals as found in the Mediterranean sapropels (Globigerinoides spp. maxima and δ¹⁸O minima), suggesting that they correspond to precession minima and, hence, (boreal) summer insolation maxima.We have established an integrated stratigraphy (calcareous plankton biostratigraphy, magnetostratigraphy, stable isotope stratigraphy and cyclostratigraphy) and an astronomical tuning of the Ain el Beida section by using conventional techniques and calibration methods. The astronomical ages for the biostratigraphic events and paleomagnetic reversals are in good agreement with the Mediterranean chronology, and confirm our cyclostratigraphic correlations. Stable isotope analyses reveal that the peak glacial stages TG22 and TG20 clearly post-date the initiation of the Messinian evaporites in the Mediterranean and that there is no evidence for a glacio-eustatic control for the onset of the MSC.Only the TG12-11 transition seems to correspond to a major intra-MSC event, i.e. the beginning of the Upper Evaporites. The typical Lago Mare facies of the Upper Evaporites was thus deposited during warmer climate conditions and associated higher global sealevel stands.

Il porgetto di conservazione della cappella di Tas-Salvatur (Kalkara, Malta) : analisi diagnostiche

The origins of the Tas-Salvatur chapel go back to the 15th century, but historical events brought about demolitions (at the beginning of the Great Siege of 1565 by order of the Grand Master Jean Parisot de la Vallette, and during the uprising against the French in 1798), re-edifications (in 1670 by prior Fra Giovanni Bichi) and interventions over the ages. Inaccessible during past years to parishioners and completely abandoned, the whole chapel is at present the subject of a conservation project carried out by the Malta Center for Restoration within the Cottonera Rehabilitation Project. In the first phase of restoration works, several scientific analyses were performed in order to define the nature of constituent materials and to evaluate the causes and the effects of deterioration processes. Original polychrome layers and repainting were found on the statue of the Madonna with Child situated in the external niche, on the altar, on the overhanging frame and on the sepulchral monument located in the interior of the chapel. Optical microscopy (under visible and UV light), SEM-EDX and FT-IR analysis were carried out identify the painting materials, the remnants of external plastering layers on the facade and the internal ones. Most of the repainting layers are made of lead white (2 PbCO3 PbCO3 Pb(OH)2) and lithopone [BaSO4 + ZnS (ZnO)]. The frame was originally gilded with a guazzo technique and covered later on with several layers of paint. The sepulchral monument in memory of Fra Giovanni Bichi was originally covered with a reddish layer of ochre on stone, while the central framed medallion and the relief portrait of the deceased were gilded (a missione). Below, on the lion's head that forms the lower part of the coat of arms, a brilliant vermilion red (HgS) was revealed under the gray repainting layers. Distribution of salts in the external masonry was evaluated and quantitative data were obtained by means of IC analysis. Tests for the extraction of salts were performed on the lower part of the altar. Sulphatation processes were found where subflorescences of gypsum are the main cause of the loss of stone material (flaking).

Mineralogy of a natural As-rich hydrous ferric oxide coprecipitate formed by mixing of hydrothermal fluid and seawater: Implications regarding surface complexation and color banding in ferrihydrite deposits

We characterized the most As-rich natural hydrous ferric oxide (HFO) material ever reported using powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XRF), light element analysis using gas chromatography (GC), visible-infrared (vis-IR) diffuse reflectivity, 57 Fe Mössbauer spectroscopy, and superconducting quantum interference device (SQUID) magnetometry. We find that the natural As-HFO material is very similar to synthetic coprecipitated As-HFO materials, but is significantly different from all known natural and synthetic As-free HFO materials and ferrihydrite samples. The pXRD patterns show systematic differences with patterns for 2-line ferrihydrite, that are interpreted as evidence for significant populations of oxygen-coordinated Fe-As pairs. Observations by TEM, combined with energy dispersive spectroscopy (EDS) microanalysis, show agglomerations of nanophase primary particles and no evidence for other Fe- or As-bearing phases. Mössbauer spectroscopy shows octahedrally coordinated Fe 3+ , with a large fraction (~20%) of the octahedral Fe environments that are significantly distorted by the presence of As, compared to the Fe local environments in As-free ferrihydrite and HFO samples. The loss on ignition (LOI) is quantitatively consistent with OH + H 2 O, measured by GC, which, in turn, is consistent with ~1 nm diameter primary particles having all their surface cations (Fe 3+ , As 5+ , Si 4+ , C 4+ ) coordinated on the free surface side by OH - and OH 2 . The banding into adjacent yellowish and reddish layers that occurs in the As-HFO deposits was studied by performing mineralogical analyses of the separated adjacent layers of two couplets of yellowish and reddish material. The yellowish samples were found not to contain secondary crystalline phases (as did the reddish samples, in small amounts) and to be relatively As-rich, C- and Si-poor. The observed anticorrelations between As and Si and between As and inorganic C suggest that natural HFOs, which usually contain significant molar amounts of Si, may not be as efficient at surface complexing As (and P) as their Si and C-free synthetic counterparts, unless formed by co-precipitation with the As (or P). The yellowish and reddish layers were also clearly resolved by both Mössbauer spectroscopy and magnetometry. Complexation of arsenate onto the HFO core was found to significantly increase the average quadrupole splitting (QS) obtained from Mössbauer spectroscopy by an amount that could not be explained by other chemical differences and that is consistent with an ~1 nm diameter particle size and somewhat smaller HFO core. The Munsell hue YR index (5-10 YR) was found to be strongly correlated to the average QS, thereby establishing that the color differences, corresponding to the measured shifts of the main visible band edge, are due to the local distortions in the [6]Fe3+ environments that are induced by As complexation, via their influence on the relevant ligand field transitions. SQUID magnetometry allows the following observations. (1) The superparamagnetic to superferromagnetic transitions occur at 25 K and lower in As-HFO, compared to 55 K in synthetic 2-line ferrihydrite, suggesting a smaller magnetic primary particle (or core) size for As-HFO and inter-particle magnetic interaction reduction by surface complexed As, Si, and C. (2) The ratio of supermoment magnitude to magnetic particle size (m 2 /n, where m is the net number of Fe 3+ atomic moments per supermoment and n is the number of Fe 3+ cations per particle or HFO core) decreases with increasing As content in the sequence synthetic-HFO > reddish-As-HFO > yellowish-As-HFO. (3) The magnetic susceptibility magnitudes for As-HFO and synthetic 2-line ferrihydrite differ by a factor of 10 and suggest different supermoment formation mechanisms (m 2 /n < 1 vs. m 2 /n > 1, respectively) related to differences in intra-particle cationic and anionic disorder and magnetic particle size.

Integrated stratigraphy and astrochronology of the Messinian GSSP at Oued Akrech (Atlantic Morocco)

A much improved high-resolution integrated stratigraphy (calcareous plankton biostratigraphy, magnetostratigraphy, cyclostratigraphy) is presented for the classic section of Oued Akrech (Atlantic Morocco) straddling the Tortonian–Messinian boundary. Magnetobiostratigraphic correlations with time-equivalent and astronomically dated sections in the Mediterranean indicate that cyclic alternations of indurated light beige coloured marls and softer, more clayey and reddish coloured marls are dominantly precession-controlled. Characteristic sedimentary cycle patterns, in particular those reflecting precession–obliquity interference, allow for one possible tuning, thus providing accurate astronomical ages for cycles, calcareous plankton events and magnetic reversals. The tuning further indicates that the reddish layers are the equivalent of sapropels in the Mediterranean. The Messinian Global boundary Stratotype Section and Point (GSSP) has recently been formally defined at the base of the reddish layer of cycle No. 15 in section Oued Akrech. This level coincides closely with the first regular occurrence of the Globorotalia miotumida group and is astronomically dated at 7.251 Ma. The global correlation potential is guaranteed by the straightforward calibration of the Oued Akrech magnetostratigraphy to the geomagnetic polarity time scale, locating the GSSP within C3Br.1r. In the marine realm the calcareous nannofossil genus Amaurolithus provides a series of extremely useful events to delimit the boundary on a global scale. The astronomical tuning guarantees a direct first-order calibration of the Messinian GSSP to the standard geological time scale once, as anticipated, the late Miocene part of the astronomical time scale has been incorporated.

The colours of Ca-rich ceramic pastes: origin and characterization

The colour changes found in the wall thickness of archaeological calcareous ceramics are analysed. The main colour change from creamy to reddish is due to the incorporation of Fe 3+ in several calcium silicates and aluminosilicates developed during firing. Iron appears as iron oxides (haematite and maghemite) and as structural iron, either in tetrahedral coordination related to the dehydrated clay minerals and to the melilites, or in octahedral coordination related to the pyroxenes of fassaite–diposide type. The creamy colour is related to the complete decomposition of calcite, a significant development of pyroxenes, and to the low presence of iron oxides. Haematite is determined across the creamy and reddish layers except in the outer surface, where maghemite is determined. The presence of maghemite and Fe 2+ in the outer surfaces agrees with the use of a low reducing atmosphere at the end of the firing process.