Change of black shale organic material surface area during oxidative weathering: Implications for rock-water surface evolution

Black shale oxidative weathering plays a significant role in a variety of processes including acid mine drainage and atmospheric CO₂ control. The modeling of weathering is highly dependent on reactive surface area. In this study it is shown that black shale oxidative weathering is regulated mainly by the external, geometrical surface area of rock polyhedrons and the organic matter’s (OM) internal surface area. The internal rock surface area decreases dramatically during OM dissolution from ∼15 m²/g to ∼5 m²/g. A linear relationship was found between the decrease of internal rock surface area and quantity of OM dissolved. Optical roughness analyses of black and bleached shale surface area reveal the formation of macropores due to the dissolution of mesoporous and probably microporous OM. However, due to deconsolidation, the geometrical external rock polyhedron surface area increases during weathering. Black shale polyhedrons show a doubling of their external surface area as OM decreases. This provokes an increase of the shale volume which is easily accessible by fluids. The increase of the external rock surface area seems to be self-accelerating during weathering. The upscaling of external and internal rock surface area evolution during weathering presented in this study demonstrates the possible application of these results to the improved understanding of a chemical transport in a variety of natural systems.     

The farmer,the worker and the MP

The territorial dimension of the digital divide is usually considered as a phenomenon that penalizes the peripheral regions, especially in terms of regional economic development. Taking into account the territorial networking of ICT (Information & Communication Technologies) infrastructures—particularly high-speed networks—provides what is probably the principal reason for such a perception. This is particularly true considering that the most-peripheral regions and those with the smallest population densities are also the poorest in terms of ICT infrastructures. In Western countries, however, the digital divide is no longer the result of network-related problems. Nowadays, the issue of the skills required to adequately exploit the potential of ICT is at the forefront. Yet this evolution is likely to lead to an inversion of the inequalities between the centre and the periphery, as populations without such skills—recent immigrants, the unemployed, the illiterate, people with little education or on low incomes and other socially marginalized people—are generally concentrated in urban centres. Consequently, the priority for reducing inequalities of access to ICT resources is no longer the provision of high-performance ICT infrastructures for peripheral regions, but rather the implementation of continuing education and social action policies within the urban centres.     

Contrasting red bed diagenesis: the southern and northern margin of the Central European Basin

We compare the diagenetic evolution of deeply buried Rotliegend (Permian) red bed sandstones at the southern and northern margin of the Central European Basin (CEB) in Germany. Main target is to evaluate the influence of maturation products from hydrocarbon (HC) source rocks during red bed diagenesis. At the southern margin of the CEB, thick coal-bearing Carboniferous source rocks are omnipresent beneath the Rotliegend. They contain dominantly gas-prone terrigenous organic material and some oil source rocks. Hydrocarbons were generated from Late Carboniferous onwards throughout most of basin subsidence. At the northern margin of the CEB, source rocks are almost absent due to deep erosion of Carboniferous rocks and a low TOC of local Lower Carboniferous relics. Early diagenetic processes are comparable at both basin margins. Significant differences in burial diagenetic evolution are spatially correlated to the occurrence of hydrocarbon source rocks. Burial diagenesis at the southern margin of the CEB is characterized especially by bleaching of red beds, major dissolution events, pervasive illite formation, impregnation of pore surfaces with bitumen, and formation of late Fe-rich cements. Almost none of these features were detected at the northern basin margin. Instead, relatively early cements are preserved down to maximum burial depths. This suggests that major diagenetic mineral reactions in deeply buried red bed sandstones are controlled by the presence or absence of maturing hydrocarbon source rocks.     

Performance documentation of the Longard Tube at Del Mar,California 1980–1983

The Longard Tube experimental revetment installed in Del Mar, California in December 1980 has been monitored and its performance documented until it subsided and became ineffective during the severe winter storms of December 1982 to March 1983. The data suggest that the tube had no measurable effect on the sand level at Del Mar beach. The beach profile monitoring program conducted by Scripps in Del Mar since 1974 served as important background information for the design and interpretation of the monitoring program measurements.The tube experienced relatively minor storm wave interaction during winter 1980–1981. This was followed by heavy beach accretion on the entire reach in spring 1981 and an unusually mild winter of 1981–1982. By July 1982 the tube was totally buried behind a berm extending 35 m seaward. The severe winter storm waves of 1982–1983 coupled with high sea level due to high spring astronomical tides, sustained onshore westerly winds and low atmospheric pressure, eroded the sand level on Del Mar beach to the lowest level in at least 10 years. The Longard Tube settled differentially by up to 2 m and was continually overtopped at high tide, rendering it ineffective by late January 1983. It was removed in March 1983. The principal conclusion of the study is that the Longard Tube configured as it was in the Del Mar test is not a substantial enough barrier to effectively prevent beach sand erosion during severe storm events on the Southern California coast.     

Proper motion measurements in various young stellar object jets in Taurus

We present proper motion measurements for a number of knots in the jets and bow shocks of the outflows from DG Tau, DG Tau B, T Tau, CoKu Tau 1, FS Tau, and FS Tau B in the nearby Taurus-Auriga star forming region. From these measurements and the available radial velocity data we derive tangential velocities, spatial velocities, angles of the outflows with respect to the plane of the sky, and in a couple of cases the pattern motions of the knots relative to the flow speed.     

Multi-scale rock surface area quantification—a systematic method to evaluate the reactive surface area of rocks

An integration of methods to quantify the surface area of porous solid materials with a broad span of spatial resolution is presented. The application of it is to detect and quantify the rock surface area modifications caused by fluid-rock interactions on different scales from several nanometres to metres. The new approach is to study the fluid-accessible surface area of rock fragments during dissolution processes.In this paper, diverse methods for surface quantification at different levels of surface detail were adapted for the application of rock surface quantification and porosimetry measurements. The geometric external surface area of rock fragments can be determined by paraffin wax coating and, in special cases, by parallelepiped surface estimations. This geometrical surface area of rock polyhedrons is equal to the macroscopic bounding surface area of a rock volume. Representative surface details on the scale of micrometres to millimetres on geometrical surface area can be quantified by mechanical roughness analyses. The resultant roughness factors are compared to optical roughness quantifications by confocal laser scanning microscopy and white light interferometry and can indicate modifications of the pore space up to several hundred nanometres. The comparison of rock pore space data, measured by both mercury intrusion porosimetry and nitrogen adsorption, quantifies the surface area of pores with a diameter of approximately 2 nm.These various surface data at different levels of detail were integrated to get an estimation of this surface area, which affects fluid-rock interactions. The proposed concept has the potential to trace the multi-scale rock surface area evolution in response to fluid-rock interaction processes.The importance of this concept is its application beyond the laboratory survey. For example, additionally to their specific surface area, the reactive surface area of rock particles in a mining dump is controlled by geometrical size and surface roughness of particles.     

AMS 14C dating of tundra lake sediments using chironomid head capsules

Radiocarbon dating of late-Quaternary sediments from high-latitude lakes is often complicated by the influx of old carbon, reservoir effects, or both. If terrestrial plant macrofossils are also absent, the dating of bulk sediment often provides the only means to establish chronologies for these problematic sediment sequences. Given that chironomid (non-biting midge) remains are sufficiently abundant in many northern lakes to be ¹⁴C-dated via the accelerator mass spectrometry (AMS) method, we decided to explore their utility in age-model development. Five age determinations based on chironomid material were obtained from a lake sediment core sampled in the shrub tundra of northern Québec. These results were compared to six AMS bulk sediment ages, as well as to a date obtained from Drepanocladus spp. The chironomids yielded consistently younger ages (with increasing age offset upcore), confirming both the presence of a reservoir effect and the value of chironomids in establishing more reliable ¹⁴C chronologies.     

Relations for local magnitude at seismic station Berggiesshübel

Summary New calibrating functions for the local magnitude M_L based on the maximum ratio of amplitude and period of the S_g - wave, the short-period surface wave and the duration of the whole seismogram and its part starting with the arrival of the S_g -wave recorded by the short-period vertical seismograph at Berggiesshübel (BRG) have been derived. The consistency of these magnitudes was tested for weak earthquakes and industrial blasts in the magnitude range of 1.7–3.5 and epicentral distances up to 80 km. Their differences were 0.2 of a magnitude unit at most, with the exception of the surface wave magnitudes which were systematic by about 0.9 of a magnitude unit greater. The calibrating function for the S_g - wave was compared with the functions for M_L(POT) and M_L(TRI) which were derived by other authors for several Central European seismic stations, including BRG.     

Präorogene Versenkungstiefe und Orogenese als Diagenesefaktoren für altpaläozoische Kontinentalrandbildungen der Nördlichen Appalachen in Quebec,Kanada

This paper presents data and preliminary interpretations on the diagenesis of Early Paleozoic continental margin deposits along a traverse of the Quebec Appalachians near Quebec City, Canada. Regional variations in diagenesis were studied using the thermal maturation of organic matter in shales (reflectance measured on asphaltic bitumen, 105 samples) and illite crystallinity (330 samples). These revealed a regional southeastward increase in grade from the late middle and late stage of diagenesis to epimetamorphism, which is reflected in the distinction of four zones: Zone I representing the late middle diagenetic stage has a mean reflectance in oil (R₀) between 1.0 and 1.5% and illite crystallinity between 5.5 and 8.0 mm. Zone II (late diagenetic stage) is characterized by R₀=1.5–2.6% and illite crystallinity between 3.5 and 5.5 mm. Anomalously poor illite crystallinities in Zone II (i. e. 5.5 to 8.0 mm) were obtained for black shales, in which improvement of crystallinity lags behind red and green shales. Zone II is subdivided into subzones IIA and IIB. In the former, reflectance and illite crystallinity increase, within individual nappes, as a function of age or depth of burial. In the latter no such dependence is observed, instead diagenetic grade increases regionally in a southeastward direction as it does in zones III and IV. Zone III represents the anchizone in which observed reflectance values R₀ range from 2.6 to 4.0% and illite crystallinities from 2.0 to 3.1 mm. In Zone IV (epizone) illite crystallinity is less than 2.0 mm (In terms of reflectance the anchi-zone/epizone boundary was not defined). Zones I and IIA are anomalous in that lower tectonic units are diagenetically less altered than higher tectonic units: R₀ varies from 1.71 to 2.30% for the highest tectonic unit (Cambrian Chaudière Nappe), 1.53 to 1.90% (Cambro-Ordovician Bacchus Nappe) and 1.08 to 1.46% (Lower Ordovician Pointe-de-Lévy Nappe) for the middle tectonic units, and 1.01 to 1.15% for the lowest tectonic unit (Middle Ordovician Quebec Promotory Nappe). Thermal maturation and mineral diagenesis in zone IIA are probably due solely to sedimentary burial at the original site of deposition (by an estimated 6 to 7 km of younger sediments) because in this zone the highest diagenetic grade occurs in the highest tectonic unit. Diagenesis in the nappes of zone I probably required additional tectonic burial by the higher nappes because original sedimentary thicknesses that once overlay these Lower and Middle Ordovician rocks appear insufficient to have caused the observed degree of diagenesis. Diagenesis in zone IIA, therefore, was most likely formed entirely before orogenesis; in zone I it is probably partly pre-orogenic in origin and has been transported during nappe-movement. In contrast, diagenesis and metamorphism in zones IIB to IV are interpreted as related to regional synorogenic heating in conjunction with the Taconic orogeny. Thermal maturation levels in zone I indicate that the rocks have not yet passed the “oil window” which is of interest for petroleum exploration in Quebec. An extended English version of this paper is in preparation for the Bulletin of Canadian Petroleum Geology (Ogunyomi et al., ms.).