ALBERT

Beschreibung: Red Pompeian paintings, very famous for their deep intensity, are currently suffering from darkening. The origins of this darkening degradation are not clearly identified yet and remain a major issue for curators. In the specific case of cinnabar (HgS)-based red pigment, a photoinduced conversion into black metacinnabar is usually suspected. This work is focused on the blackening of red cinnabar paintings coated on a sparry calcite mortar. Different samples exhibiting different levels of degradation were selected upon visual observations and analyzed by synchrotron-based microanalytical techniques. Atomic and molecular compositions of the different debased regions revealed two possible degradation mechanisms. On one hand, micro X-ray fluorescence elemental maps show peculiar distributions of chlorine and sulfur. On the other hand, X-ray absorption spectroscopy performed at both Cl and S K-edges confirms the presence of characteristic degradation products: (i) Hg- Cl compounds (e.g., corderoite, calomel, and terlinguaite), which may result from the reaction with exogenous NaCl, in gray areas; (ii) gypsum, produced by the calcite sulfation, in black coatings. Metacinnabar is never detected. Finally, a cross section was analyzed to map the in-depth alteration gradient. Reduced and oxidized sulfur distributions reveal that the sulfated black coating consists of a 5-ím-thick layer covering intact cinnabar.

Beschreibung: Published

Beschreibung: 7484-7492

Beschreibung: reserved

Beschreibung: Aeromagnetic data were collected over the Hall Basin and adjacentcoastal land areas of northern Nares Strait during the 2001 Canadian-GermanNares Strait Expedition to provide an improved onshore-offshore linkage ofgeological structures related to the Late Cretaceous Early PaleogeneEurekan Orogeny. The total field magnetic anomaly data are characterized bybroad long-wavelength anomalies compatible with thick sequences of nonmagneticSilurian and Devonian carbonate facies. On the Greenland side ofthe survey block, the magnetic anomalies are generally positive, possiblyreflecting the magnetic characteristics of deeply buried crystalline rocks of thePaleozoic platform. Over Ellesmere Island, the magnetic anomalies are low inamplitude, suggesting a different basement composition from Greenland. Twolinear northeast oriented positive magnetic anomalies are observed on JudgeDaly Promontory. One extends along the south coast between Carl Ritter Bayand the mouth of Daly River. The second occurs over the northern end of thepeninsula and extends offshore from Cape Baird to Robeson Channel. Fromfield samples, this anomaly has been correlated with thrust fault-boundedTertiary sedimentary basins, which have increased susceptibility valuescaused by the content of basalt clasts. The thrust fault, bounding the southernedge of these basins has been mapped as a continuous feature across JudgeDaly Promontory, however, the absence of a continuous magnetic anomaly islikely the result of complete erosion of the sedimentary wedge. The amplitudeof this anomaly decreases south of Carl Ritter Bay, as a result of decreasedcontent of basalt clasts. A small magnetic anomaly at 81.3 °N, 66.8 °W alsocoincides with an isolated outcrop of Tertiary rocks, associated with a differentfault. The offshore extension of these anomalies indicates a continuity ofthe Tertiary basins northeastward to Robeson Channel and to the LincolnSea. It does not follow a simple continuous line, but appears to be broken insubsections of slightly differing directions. Similar offsets are observed in aparallel magnetic anomaly in Hall Basin suggesting crosscutting NWSEtrending faults. The magnetic anomalies and onshore geological observationssuggest that the Wegener Fault is not a simple strike-slip fault, but a complexsystem of faults and a chain of blocks and basins.