Diagnosis of weathering damage on rock-cut monuments in Petra, Jordan

Studies of many years—combining in situ investigation and laboratory analysis—have provided comprehensive information on weathering damage on the rock-cut monuments in the ancient city of Petra in Jordan. These rock-cut monuments represent outstanding world heritage. Many hundred monuments were carved by the Nabataeans from bedrock about 2000 years ago. The awareness of increasing weathering damage on the monuments has resulted in international efforts towards their preservation. The damage diagnosis has addressed the complex mutual relationships between stone types, stone properties, monument exposure regimes, environmental influences, weathering phenomena, development and extent of weathering damage and weathering progression. The rocks were classified lithostratigraphically and petrographically. Results on weathering forms, weathering profiles and weathering products obtained from monument mapping, in situ measurements and laboratory studies revealed a complex diversity of weathering phemomena with respect to type and intensity. Damage categories and damage indices were used to create a reproducible quantitative rating of weathering damage. Detailed results on weathering forms allowed the characterization and quantification of weathering progression including weathering prognoses. Stone properties and states of weathering damage were jointly considered for the rating of the rocks’ susceptibility to weathering. The systematic evaluation of weathering damage and monument exposure regimes can enhance the assessment of weathering factors and processes.     

Paleomagnetic events in the brunhes and Matuyama epochs identified from magnetic profiles reduced to the pole

Eleven oceanic magnetic profiles associated with the paleomagnetic time scale younger than the beginning of the Matuyama epoch (2.43 my) have been reduced to the pole, altered to conform to a 3 cm yr^-1 spreading rate, and then all halves added and averaged to obtain a representative symmetric magnetic profile. This final stacked profile emphasizes the subtle anomalies associated with minor paleomagnetic events and minimizes randomly occurring anomalies. The axial anomaly of the stacked profile shows no evidence of the Laschamp event (centered at 0.025 my); however, a minimum at 0.15 my may correspond to the Blake event. A physical model of the stacked magnetic profile consists of a thin, highly magnetized layer with a 40% magnetization decrease at 10 km from the profile center. Magnetization values were modified from Irving and Talwani and the Blake event included. The stacked profile shows two minor anomalies centered at 1.97 my and 2.17 my. The younger anomaly corresponds with the younger Olduvai event (centered at 1.965 my) on the Cox time scale and the W anomaly (centered at 1.99 my) of Emilia and Heinrichs. The older anomaly lies between the older Olduvai event (2.12 my) of Cox and the X anomaly of Heirtzler, and Emilia and Heinrichs; additional work is required to assess the significance of this older event.This material was presented at the Fall Annual Meeting of the American Geophysical Union, December 8, 1971.     

Ductile deformation of garnet in mylonitic gneisses from the Münchberg Massif (Germany)

Mylonitic gneisses from the Münchberg Massif contain single grains (type I) and polycrystalline aggregates (type II) of garnet displaying a distinct elongation parallel to a macroscopic lineation which is interpreted as the result of ductile deformation. Lattice-preferred orientations of quartz (textures) symmetrical to the macroscopic foliation and lineation and the lack of rotational microfabrics indicate that the bulk deformation was pure shear at least during the latest strain increments. Garnet textures measured by EBSD together with microprobe analyses demonstrate that these two structural types of garnet can be related to two different processes of ductile deformation: (1) For the single grains stretching can be attributed to diffusion creep along grain boundary zones (Coble creep). The related mass transfer is indicated by the fact that primary growth zones are cut off at the long faces of the grains while the related strain shadow domains do not show comparable chemical zoning. Pressure solution and precipitation suitable to produce similar structures can be largely ruled out because retrogressive reactions pointing to the presence of free hydrous fluids are missing. (2) For the polycrystalline garnet aggregates consisting of cores grading into fine-grained mantles, dislocation creep and associated rotation recrystallization can be assumed. Continuous lattice rotation from the core to the outer polycrystalline rim allow a determination of the related dominant slip systems which are {100}<010> and equivalent systems according to the cubic lattice symmetry. The same holds for garnets which appear to be completely recrystallized. For this type of fine-grained aggregates an alternative nucleation model is discussed. Due to penetrative dislocation glide in connection with short range diffusion and the resulting lattice rotation, primary growth zones are strongly disturbed.Since for the considered rock unit of the Münchberg Massif peak metamorphic temperatures between 630 and 670 °C can be assumed, this study clearly demonstrates that the inferred processes of ductile garnet deformation can occur not only in HT regimes as often suggested in the literature even if embedded within a matrix of “low-strength” minerals like quartz, feldspars and micas.     

A comparison of chironomid biostratigraphy from Lake Vuolep Njakajaure with vegetation, lake-level, and climate changes in Abisko National Park, Sweden

Chironomid remains from the sediment of Lake Vuolep Njakajaure reflect limnological conditions resulting from changing climate and vegetation throughout the Holocene, but do not strictly follow accepted climate trends or the vegetation history based on regional pollen and macrofossil analyses. Chironomid community changes appear to be influenced by organic nutrient input from the surrounding catchment vegetation and lake hydrology, both of which are indirectly responding to some combination of climate change, hypolimnetic oxygen concentration, and changes in basin morphology. The chironomid-based quantitative mean July air-temperature reconstruction differs from other regional quantitative records; this discrepancy is likely related to limnological conditions particular to Lake Vuolep Njakajaure. Comparison of a northern Swedish temperature transfer function and one from western Canada reveals differences in the mean July air-temperature optima of several common taxa, suggesting that the existing conservative estimates of Holocene climate change in northern Sweden may be underestimated due to the limited temperature gradient captured by the Swedish training set.     

The reserves of extracted resources: Historical data

The available data on known reserves of extracted resources have not previously been tabulated and graphed. In this article we compile the reserves data in one place for the first time. This serves to (1) show the trends in the reserves series, (2) make the series available to others, and (3) place the reserves data in the context of price data for which longer series have been available, and with which they can now be seen to be consistent in both showing increasing availability rather than increasing scarcity.     

Chemical characteristics and genesis of the quartz-feldspathic rocks in the Archean crust of Greenland

A total of 108 samples of meta-tonalites, metagranodiorites, granites and meta-tholeiites representing groups of Early to Late Archean age and different metamorphic history from SW and SE Greenland have been analyzed for Ca, K and 28 trace elements. There is no systematic change of the chemical composition with age observable. The results support petrologic experiments which suggest that tonalites and granodiorites (the most abundant rocks of the Archean crust) are partial melting products of a mafic lower crust. Modelling suggest that this crust consisted of garnet amphibolite derived from a source with a bulk composition resembling a slightly enriched rather than depleted mantle. The Ce_N/Yb_N ratio is above 10 in the majority of tonalites. Most samples have no Eu anomaly because of a balanced contribution from the minerals of a mafic rock (or a plagioclase-free source). The positive Eu anomaly of some granodiorites and of a minor proportion of tonalites can be explained as being caused by plagioclase accumulation during differentiation or by partial melting of plagioclase-rich fractions. Modelling with Zn excludes an origin of tonalitic melts by differentiation of basaltic to dioritic magmas. The Archean meta-diorites, meta-tonalites and meta-granodiorites from Greenland have generally lost some K and S relative to their suggested magmatic protoliths. Loss of Rb, Tl, Pb and K and relative gain of Ca, Sr, Ba and Sc connected with granulitization of meta-tonalites can be explained in the majority of cases by separation of about 25 percent granitic partial melt. High K/Rb, K/Pb, Zn/Cd and Nb/Th ratios of granulites plus low ratios of granites are almost in balance with intermediate ratios of amphibolite-facies tonalites. Retrogression of granulites into amphibolites was accompanied by introduction of Pb, Tl, Rb, Ba, Sr and K from Na-Cl-rich brines circulating on fractures. A comparison of the abundance of 24 elements (characterized by different compatibility) in the Archean crust of Greenland with the present bulk crust reflects only minor changes (Th, Nb) if at-all in the chemical composition of the continental crust since the Archean.     

Loss of metals from pelites during regional metamorphism

In aluminous metapelites the ratio H₂O⁺/K₂O decreases with increasing metamorphic grade and degree of reaction. This ratio is a very practical indicator for the progress of the mineral reconstitution during progressive metamorphism. With decreasing values of the ratio H₂O⁺/ K₂O the Cu concentration and the following element ratios also decrease either continuously or in stepwise fashion: Tl/K₂O, Ba/K₂O, Pb/K₂O, Bi/K₂O, Hg/K₂O, Sr/Na₂O, Zn/(Fe²⁺+Mg), Cd/(Fe²⁺+Mg); Rb/K₂O remains approximately constant. In the aluminous metapelites of the Damara Orogen in Namibia the following losses occur between the biotite isograd and anatexis: 61% Cu, 20% Tl, 34% Ba, 59% Pb, 86% Bi, 46% Hg, 30% Sr, 25% Zn, 31% Cd. Thus the potential of regional metamorphism to form hydrothermal deposits in the low grade environment should not be neglected.     

Enhancing mobile applications by combination of GNSS and W-CDMA

The location requirements for emergency callers outside urban areas can hardly be fulfilled without global navigation satellite systems (GNSS). Consequently, interest in positioning techniques based on use of a GNSS such as GPS or on the cellular network infrastructure itself is growing rapidly in the mobile-telephone community. Moreover, the increasing demand for commercial location-based services (LBS) has driven cellular-phone and network manufacturers to focus on positioning solutions which are even more accurate than the regulatory mandates for positioning of emergency callers. One example of these upcoming LBS is our PARAMOUNT project, which aims at improving user-friendly info-mobility services for hikers and mountaineers by combining wireless communications (GMTS), satellite navigation (GNSS) and geographic information systems (GIS), based on a mobile client/server architecture. The availability of mobile phones or PDAs with combined GNSS and cellular network-based wireless communication on a high integration level is one primary demand of such LBS applications. Based on this, we will give some initial answers to the question of whether mobile handset architecture synergies exist for the combination of GNSS with wireless location in CDMA cellular wireless networks. In order to identify synergies, we will outline similarities and differences between wireless communication and satellite navigation. In this respect, we pay particular attention to the so-called RAKE receiver architecture employed in mobile CDMA cellular handsets. Our initial investigations will show that the RAKE receiver architecture, on which mobile CDMA cellular handsets are based, will most likely be the one most suitable for achieving synergies between the two positioning techniques within the same mobile handset architecture. Consequently, several receiver components could be used to handle both types of signals (navigation and communications), resulting in a reduction of manufacturing costs and in a decrease in energy consumption. Electronic Publication     

C‐band SAR backscatter characteristics of Arctic sea and land ice during winter

Abstract

Synthetic Aperture Radar (SAR) data has become an important tool for studies of polar regions, due to high spatial resolution even during the polar night and under cloudy skies. We have studied the temporal variation of sea and land ice backscatter of twenty‐four SAR images from the European Remote Sensing satellite (ERS‐1) covering an area in Lady Ann Strait and Jones Sound, Nunavut, from January to March 1992. The presence of fast ice in Jones Sound and glaciers and ice caps on the surrounding islands provides an ideal setting for temporal backscatter studies of ice surfaces. Sample regions for eight different ice types were selected and the temporal backscatter variation was studied. The observed backscatter values for each ice type characterize the radar signatures of the ice surfaces. This time series of twenty‐four SAR images over a 3‐month period provides new insights into the degree of temporal variability of each surface. Ice caps exhibit the highest backscatter value of ‐3.9 dB with high temporal variability. Valley glacier ice backscatter values decrease with decreasing altitude, and are temporally the most stable, with standard deviations of 0.08–0.10 dB over the 90‐day period.

First‐year ice and lead ice show a negative trend in backscatter values in time and a positive correlation of up to 0.59 with air temperature over the 90‐day period. For first‐year ice and lead ice, episodes of large temperature fluctuations (±12°C) are associated with rapid changes in backscatter values (±2 dB). We attribute the backscatter increase to a temperature‐induced increase in brine volume at the base of the snow pack. Multi‐year ice, conglomerate ice and shore ice are relatively stable over the 3‐month period, with a backscatter variation of only a few dBs. An observed lag time of up to three days between backscatter increase/decrease and air temperature can be attributed to the insulation effect of the snow cover over sea ice. The net range of the backscatter values observed on the most temporally stable surface, valley glacier ice, of about 0.30 dB indicates that the ERS‐1 SAR instrument exceeds the 1 dB calibration accuracy specified for the Alaska SAR Facility processor for the three winter months.     

The fine structure of the solar atmosphere in the far ultraviolet

High resolution spectroheliograms in the ultraviolet emission lines He i, He ii, O iv, O v, and Ne vii have been photographed during a sounding rocket flight. Simultaneously, broad band filtergrams of the far ultraviolet solar corona were obtained from the same flight. This paper describes qualitatively the spatial distribution of the UV emission. A comparison with an H filtergram is made. The most significant results can be summarized as follows: We find most of the ultraviolet emission concentrated around spicules, with different degree of concentration, decreasing with higher temperatures. 4 different areas of ultraviolet emission can be distinguished. (1) The normal network, bright in all UV emission lines from the chromosphere into the corona. (2) The coronal holes, bright in all UV emission lines up to 600 000 K but depressed in coronal lines from 1 million degrees upward. (3) The coronal depressions near active centers, absence of all ultraviolet emissions and (4) Active regions, where ultraviolet emission comes from plages, sunspots and coronal loops. High non-thermal Doppler velocities can be found in certain plage kernels around 10⁵ to 2 × 10⁵ K. Sunspots are bright in the ultraviolet, but do not exhibit He i or He ii emission. The corona above sunspots is weak. Sunspots do not show high non-thermal Doppler velocities. The He i and He ii emission does not follow either chromospheric, transition zone or coronal pattern; one can recognize some typical behavior of each.