Mesoscale raised rim depressions (MRRDs) on Earth: A review of the characteristics,processes, and spatial distributions of analogs for Mars

Fields of mesoscale raised rim depressions (MRRDs) of various origins are found on Earth and Mars. Examples include rootless cones, mud volcanoes, collapsed pingos, rimmed kettle holes, and basaltic ring structures. Correct identification of MRRDs on Mars is valuable because different MRRD types have different geologic and/or climatic implications and are often associated with volcanism and/or water, which may provide locales for biotic or prebiotic activity. In order to facilitate correct identification of fields of MRRDs on Mars and their implications, this work provides a review of common terrestrial MRRD types that occur in fields. In this review, MRRDs by formation mechanism, including hydrovolcanic (phreatomagmatic cones, basaltic ring structures), sedimentological (mud volcanoes), and ice-related (pingos, volatile ice-block forms) mechanisms. For each broad mechanism, we present a comparative synopsis of (i) morphology and observations, (ii) physical formation processes, and (iii) published hypothesized locations on Mars. Because the morphology for MRRDs may be ambiguous, an additional tool is provided for distinguishing fields of MRRDs by origin on Mars, namely, spatial distribution analyses for MRRDs within fields on Earth. We find that MRRDs have both distinguishing and similar characteristics, and observation that applies both to their mesoscale morphology and to their spatial distribution statistics. Thus, this review provides tools for distinguishing between various MRRDs, while highlighting the utility of the multiple working hypotheses approach.     

Sub-bottom profiling and coring of sub-basins along the lower French River, Ontario: insights into depositional environments within the North Bay outlet

Sub-bottom profiling was conducted at eight sub-basins within the lower French River area, Ontario, to investigate deposits preserved within the ancient North Bay outlet. Ten cores were collected that targeted the four depositional acoustic facies identified in the sub-bottom profiling records. The rhythmically laminated/bedded glaciolacustrine deposits of facies I are interpreted to have aggraded within glacial Lake Algonquin and its associated recessional lakes that persisted between 13,000 and 11,300 cal BP (~11,100 and 9,900 BP). The majority of the facies II, III and IV lacustrine deposits accumulated between about 9,500 cal BP (~8,500 BP) and the mid-Holocene, based on radiocarbon-dated organic materials. These deposits represent sedimentation within a ‘large’ lake during the late portion of the Mattawa-Stanley phase, and the Nipissing transgression, Nipissing Great Lakes and post-Nipissing recession phases of lake levels. Two sets of organic-rich sand beds are preserved within facies II deposits and reveal that the large lake lacustrine depositional environment was interrupted during the late Mattawa-Stanley phase between 9,500–9,300 and 9,000–8,400 cal BP (~8,500–8,300 and ~8,000–7,600 BP), when the water surface of Lake Hough fell below the outlet threshold and the lake basin became hydrologically closed. Pre-9,500 cal BP (~8,500 BP), the early and middle portions of the Mattawa-Stanley phase were dominated by erosion, as reflected by an unconformity at the base of facies II that occurs widely in the sub-basins and the general lack of preserved deposits for these intervals in the cores. This erosion is attributed to wave action and fluvial scouring within the outlet mouth during the early and mid-Stanley-Hough low stages and relates specifically to the period when the flowing portion of the North Bay outlet was situated over the lower French River area. This study reveals that the majority of the post-glacial deposits accumulated after the outlet threshold had shifted permanently eastwards and the lower French River area was inundated under the multiple phases of the large lake occupying the Nipissing Lowlands and Georgian-Huron basins, extending well into the mid-Holocene. The occurrence of deposits marking two closed-basin intervals during the late Stanley-Hough stage are well preserved locally within the lacustrine depositional sequence, but identifying earlier closed-basin intervals from the French River stratigraphy is hindered by the lack of preserved pre-9,500 cal BP (~8,500 BP) post-glacial deposits.     

Socio-cultural dimensions of climate change: charting the terrain

We have reached a crucial turning point in debates around climate change. A well established scientific consensus regarding the physical causes, dynamics, and at least many likely implications of anthropogenic climate change has thus far failed to result in any substantial movement towards mitigation. For many, then, the most urgent questions regarding climate change are now socio-cultural ones, such as: how do people come to hold and act on certain beliefs regarding environmental conditions and processes; how do institutional forms and histories shape and constrain the views and options of various sorts of actors; and what are relationships among fossil fuels, climate change, and the historical geographies and future trajectories of capitalism? Far from being simpler than physical and life science questions, these social science questions introduce entirely new sorts of actors, dynamics, and methodological challenges into this already complex and dynamic domain. This special issue takes up these topics. In this essay, we chart some of the major contours of contemporary social science thinking regarding climate change and introduce the articles in the special issue. We begin by examining work, from political science and scholarship on the commons, that foregrounds questions of sovereignty, territoriality, and cooperation with respect to environmental governance. Then we examine work from neoclassical economics and radical political economy, which frame climate change in terms of externalities, or contradiction and crisis, respectively. Finally, we examine the rapidly proliferating work exploring how individuals think and feel about these issues, emphasizing concepts of risk, communication, and governmentality.     

Contending with unequal and privileged access to natural resources and land in the Okavango Delta, Botswana

This paper reviews how state policy and regulatory instruments, including protected area alienations and concessions, have altered or denied the access to land and natural livelihood resources of the indigenous Basarwa and minority subsistence-oriented communities in the Okavango Delta (OD) in Botswana. Drawing on field research and guided by a sustainable rural livelihoods framework, the paper provides an overview of key institutional interventions – in particular the setting up of the Moremi Game Reserve, Wildlife Conservation Policy, Tourism Policy, Agricultural Development Policy and the erection of veterinary fences – that have served to privilege a foreign-owned and dominated commercialized wildlife and nature tourism sector and the export-oriented beef industry in the OD. The officially sanctioned barriers to customary and usufructory rights and access, and the non-recognition of historically embedded traditional land uses have decimated already marginalized resource-based subsistence livelihoods, and precipitated intergroup conflicts over preferential rights and access to resources and opportunities, notably wildlife, non-timber veld products, agriculture and community-based tourism schemes. Such outcomes, moreover, will have consequences for the longer-term sustainability of the OD both as a socioeconomic resource base and as a natural ecosystem.     

A multi-method approach for the identification and quantification of water balance components of two lentic small water bodies

The protection of the globally widespread lentic small water bodies (LSWB) must be based on detailed knowledge about their hydrological connectivity and water balance. The study aimed to identify and quantify water balance components as well as surface-groundwater interaction of two LSWB in a characteristic lowland region with a combination of different methods. This includes the collection of hydrological data and the use of bromide and water stable isotopes (δ²H and δ¹⁸O) as tracers. With their help, mixing models were established, and daily water balances were assessed. The results show a strong bidirectional interaction of both LSWB systems with shallow groundwater. Bromide and stable isotope tracers allowed for the identification of the most relevant in- and outflow sources and pathways. Thereby, isotope data revealed isotopic enrichment typical for open-water bodies and only minor precipitation inputs mainly relevant at the end of the dry season. Water balance calculations suggested accentuated seasonal dynamics that were strongly influenced by shallow groundwater, which represented large inputs into both LSWB. By that, different phases could be identified, with high inflow rates in winter and spring and decreasing fluxes in summer. In one LSWB, a drainage system was found to have a major impact next to the shallow groundwater interaction. The findings of this research provide detailed insights into the influence and importance of shallow groundwater for LSWB in lowland regions. This impacts the diffuse input of agricultural pollutants into these ecologically important landscape features.     

Preliminary health risk assessment for polybrominated diphenyl ethers and polybrominated dibenzo-p-dioxins/furans in seafood from Guangzhou and Zhoushan, China

Dietary intake is one of the important routes of human exposure to brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs). The use of PBDEs may also result in exposure to polybrominated dibenzo-p-dioxins and dibenzofurans (PBDDs/DFs), as these compounds are impurities in technical mixtures of BFRs and can also be formed unintentionally by the same processes that generate chlorinated dioxins. This study determined the concentrations of polybrominated compounds in common seafood in Guangzhou and Zhoushan, and assessed the health risks of these chemicals via consumption of contaminated seafood. Seafood samples (fish, bivalves, shrimp, crab, and cephalopods) purchased from local markets in 2003 and 2004 were analyzed for PBDEs and PBDDs/DFs. The highest concentration of total PBDEs (46.3 ng g(-1) lipid wt.) was detected in fish from Guangzhou, in which BDEs 47 and 209 were the two predominant congeners. The total daily intakes of PBDEs, PBDDs, and PBDFs were, 946, 6.39, and 6.54 pg kg(-1) body weight (bw) in Guangzhou, and 489, 4.99, and 7.65 pg kg(-1) bw in Zhoushan, respectively. The hazard ratios for PBDDs and PBDFs were both greater than unity, indicating that these compounds may pose some health risks to the local population.     

The Romanian earthquake of August 30, 1986: A study based on GEOSCOPE very long-period and broadband data

The Romanian earthquake of August 30, 1986 is the second largest intermediate depth event in this area since the worldwide deployment of digital instrumentation, and the first one since the installation of GEOSCOPE network. It offers the unique opportunity to document this well-known but poorly understood zone of deep continental seismicity using high quality teleseismic data in different frequency bands. The source is well constrained both from very-long period surface wave data observed on GEOSCOPE stations and, independently, from body wave modelling at various worldwide stations. The depth obtained is approximately 140 kilometers, the seismic moment, 0.8 10²⁷ dyne-cm and the mechanism from both data sets is very similar to that of the previous 1940 and 1977 Vancrea events, indicating that these events, although having occurred at noticeably different depths, are expressions of the same tectonic process. However, from the detailed study of the source using broadband data, it can be inferred that the source presents much less complexity than the 1977 event.     

L’influence de certaines substances toxiques,contenues dans les eaux d’égouts municipaux,sur les bactériesEscherichia coli etPseudomonas fluorescens

The toxic influence of phenol, aniline, pyridine and chrome, substances often found in municipal wastewaters, on the bacteriaEscherichia coli andPseudomonas fluorescens was examined. The non-toxic, growth limiting, toxic and lethal doses were determined on the basis of observations made ofE. coli andP. fluorescens reproduction and respiration patterns. Comparative test series were set up with the various doses in different nutrient cultures to ascertain whether the bacterias’ multiplication process or carbohydrate decomposition was more sensitive to the chemicals.     

A survey of lunar transient phenomena

Periodic and morphological characteristics of lunar transient phenomena (LTP) are described. Some early historical records are reviewed. Most sites of LTP's show evidence of internal disturbance either initiated from within or by volcanic modification of impact formations. Some individual crater sites are described. The probability of the reliability of at least some, and probably most, reports has been increased by the later discovery of the periodic nature of the deep-focus and shallow moonquakes; spurious reports would not have produced the periodicity of LTP's, but random errors would increase the noise level.The conclusion to be drawn from the inadequacy of external energy sources is that some energy must be injected from within the moon, probably in the excitation of gases, but this must remain speculation until better data is obtained. The underlying problem now is still the difficulty of obtaining permanent instrumental records; only twenty heterogeneous reports are at present known.     

After horton

The divergent and yet related problems of post-Hortonian studies of drainage density and channel network geometry are viewed against the difficulties of defining first-order channels and basins. It is proposed that the junction of an unbranched perennial (or blue-line) channel with another perennial channel be taken as the starting point for definitions and that the entire contour-crenulation network tributary to that point be considered the first-order stream. It is shown that the concept of network diameter may be used to describe the networks so delimited and that it appears to provide a useful starting point for interregional comparisons. Finally, an analysis of Blyth and Rodda's (1973) data on channel lengths and discharge indicates that network diameter may be as closely related to discharge as is channel length itself.