A comparative study of H+ and He+ at sunspot minimum and sunspot maximum

The time-dependent equations of continuity and momentum for O⁺, H⁺ and He⁺ are solved for the section of a mid-latitude flux tube from the lower F2-region to the equator. H⁺ and He⁺ behaviour is compared for both sunspot minimum and sunspot maximum conditions at equinox concentrating on light ion replenishment following a magnetic storm and light ion fluxes.It is found that the He⁺ fluxes vary little from day to day throughout the replenishment period following a magnetic storm. In contrast, the H⁺ fluxes can vary considerably throughout the replenishment period, particularly at sunspot minimum. In addition, our results show that temperatures above 1000 km have an important influence on the variation and magnitude of H⁺ fluxes and consequently also influence the replenishment of H⁺. At sunspot minimum the He⁺ content reaches its maximum value after eight days of replenishment and then starts to decrease whilst the H⁺ content continues increasing. This is explained in terms of night-time H⁺ return flows dragging the He⁺ to regions where it can readily recombine. Consequently lightion depletion following a magnetic storm provides a loss process for neutral helium at sunspot maximum but not necessarily at sunspot minimum.     

Monks on the move? An assessment of mobility at the medieval Nubian monastery of Ghazali,Sudan (ca. 680–1,275 CE)

The location of Ghazali monastery away from the Nile valley within the relatively isolated environs of the Bayuda desert presents a landscape suggestive of mobility toward the monastery by those who chose to reside there as monks. To assess this potentiality, a sample of 37 individuals from the monastic cemetery (Cemetery 2) were analysed for ⁸⁷Sr/⁸⁶Sr and δ¹⁸O to assess residency during dental enamel formation. The data generated bring into question the nature of mobility to Ghazali monastery, particularly in regard to the potential movement of people from the Nile valley, adjacent desertic landscapes, and further afield.     

The last glaciation in the Western Mourne Mountains,Northern Ireland

During the late‐Midlandian (25–13 ¹⁴C ka BP), the last Irish Ice Sheet was thicker in the Western Mourne Mountains than previously argued. Geomorphological and sedimento‐logical analysis shows that regional ice from the Irish Ice Sheet spilled over the mountains, reaching a major limit 5 km along Pigeon Rock Valley. These findings differ from the previous view that a local valley glacier occupied the valley during this period. The pattern of deglaciation was reconstructed using glacial and periglacial evidence. A complex topographic environment in the upper reaches of the valley suggests that regional ice stagnated as it wasted away. During the Nahanagan Stadial (Younger Dryas, ca. 11–10 ka ¹⁴C BP) an arcuate ridge was formed on the western flank of the valley. Calculations suggest that the Equilibrium Line Altitude, influenced by topographic conditions favourable for snow accumulation, was approximately between 1736 m and 1386 m lower during the Nahanagan Stadial than at present.     

Landscape Archaeology in a Dry-Stream Valley near Tell es-Sâfì/Gath (Israel): Agricultural Terraces and the Origin of Fill Deposits

Abstract

As part of the long-term archaeological project being conducted at Tell e-Sâfi/Gath in the semi-arid foothills of the Judean Mountains, a first order dry stream channel located in a valley east of the main site was surveyed and soil pits excavated in selected locations. A ditch, 10 m in length, was dug perpendicular to one of the agricultural terraces, showing that the small valley is filled with soil to a depth of more than 3 m above bedrock. The fill dates mainly to the Byzantine period (ca. 4^th-7^th cent. CE), according to the ceramic sherds. Three check-dam walls and related terraces were found across the width of the valley. Surprisingly, the base of the check-dam does not go deeper than 50 em into the uppermost part of the fill, well above bedrock or gravel layers, while covering only the upper part of the terrace step. Thus we use the term “floating terrace wall” or “floating check-dams”. Each of the terrace walls is about 0.5 m high and 50 m long. The valley is bound by two slopes: (1) a northeast facing slope characterized by Nari outcrops (a hard calcrete crust in the upper part of the chalk bedrock) and soil pockets, and (2) a southwest facing slope without Nari. The source of most valley fill material is apparently from the slope without Nari. The valley shows comparatively little accumulation during the Iron Age and very much accumulation during the Byzantine period. The main cause seems to be human-made earth movement and terrace building during the Byzantine period, rather than passive erosion and accumulation as a result of general environmental pressure by human activity.     

The Regional History of the Guan River Valley,China: Cultural Periphery,Ecological Diversity,and the Development of Social Complexity before A.D. 220

Regional settlement pattern studies in China have overlooked interregional interaction in the development of social complexity. This study examines settlement patterns, land use practices, sociopolitical structure, and interregional interaction from 4000 b.c. to the early Imperial period (before a.d. 221) in the Guan River valley, China. The Guan valley is located at the inter-montane corridor to three cultural core zones in China. An international collaborative team used regional full-coverage survey to locate 96 sites in 135?km² in the Middle Guan valley, the earliest of which dated to the middle Yangshao period (4000–3500 b.c.). In the late Yangshao period (3500–2900 b.c.), occupation increased rapidly and expanded to the upper reach and tributaries of the river. After an occupational collapse during the Early States period (1900–771 b.c.), the population recovered rapidly and reached a new level of organizational complexity in the Eastern Zhou period (770–221 b.c.). This pattern continued into the Qin-Han period (220 b.c.–a.d. 220), when hamlets increased in number and expanded into hilly areas.     

Paleodiet in northern Chile through the Holocene: extremely heavy δN values in dental calculus suggest a guano-derived signature?

Dental calculus extracted from the teeth of 28 prehistoric human skeletons from coastal and valley archaeological sites in northern Chile that date from the Archaic period (∼2300 BC) to the Late Intermediate period (AD 1476) was analyzed for stable isotope (δ¹⁵N, δ¹³C) compositions. δ¹⁵N compositions were extremely heavy (+17.8 to +33.1‰), but comparable to some studies using conventional human biomaterials (hair, nail, muscle) at other prehistoric sites in northern Chile. There was a negative correlation between δ¹⁵N and δ¹³C for coastal sites, but a positive correlation for valley sites. Results for the valley sites point to a diet that was influenced by marine resources throughout all time periods. The unusually heavy δ¹⁵N values for the coastal sites require a dietary component with a δ¹⁵N composition significantly heavier than that of marine resources. The hyper-aridity at the study area (mean annual rainfall of 0.5–0.6 mm/year) is a likely contributing factor to the production of heavy δ¹⁵N values, but is unlikely to account for the heaviest δ¹⁵N values (>+30‰). One possible explanation for the heaviest δ¹⁵N values is that dietary components were impacted by isotopically-heavy guano, which is abundant in the region. Guano may have been used as a fertilizer during crop cultivation at the onset of the Formative period, continuing through the Historic period after Spanish contact. The indirect impact of guano from abundant bird habitats in the region may have influenced wild foodstuffs harvested throughout the pre-agricultural period. Results provide support for the utility of dental calculus as a proxy for obtaining stable carbon and nitrogen isotope signatures for use in paleodietary studies.     

Diet and mobility in Middle Archaic Florida: stable isotopic and faunal evidence from the Harris Creek archaeological site (8Vo24), Tick Island

We explore diet and mobility in Middle Archaic Florida using human burials and faunal remains from the Harris Creek archaeological site (8Vo24) on Tick Island. We conducted stable carbon and oxygen isotopic (δ¹³C, δ¹⁸O) analyses of 50 human enamel samples and strontium isotopic (⁸⁷Sr/⁸⁶Sr) analysis of a subset of 10. Most individuals (46/50) subsisted on local freshwater and terrestrial resources, with relatively depleted δ¹³C values (C₃) and δ¹⁸O values matching those of central and north Florida water resources within the St. Johns River valley. Eight of 10 burials have local, within valley ⁸⁷Sr/⁸⁶Sr values. Two human burials yield marine δ¹³C and ⁸⁷Sr/⁸⁶Sr values, which we interpret as evidence for across valley movement from the coast. Another two individuals show depleted δ¹⁸O values, likely obtained from northern rivers. We also identified potential food resources and non-local foods from the Harris Creek faunal assemblage. We found six species with estuarine and marine habitat preferences; two of which, whelk and quahog, indicate that people of Harris Creek traveled to or traded with coastal areas.     

Identifying food provenience using Sr/Ca ratio in human enamel

The strontium (Sr) concentration in bioapatite of human bone and teeth reflects the Sr concentration in food that is differentiated by two major factors: an abundance of Sr in local soils and the biopurification effect along the trophic levels. Eastern Syria is an area with a relatively high concentration of Sr within the Euphrates valley and a low concentration of Sr beyond the valley. For this reason, the strontium/calcium (Sr/Ca) ratio in human enamel retrieved from skeletons buried in cemeteries within the Euphrates valley may be used as a proxy for food provenience in a local population. A sample of human teeth (N = 72) from Tell Ashara and Tell Masaikh was divided into seven temporal subsets covering periods between c.2200 bce and the early 20th century ce . A significant difference in Sr/Ca values between temporal subsets is observed. The Sr/Ca values in later subsets are negatively correlated with δ¹³C values, indicating the wider exploitation of steppe areas outside the valley with more wild C4 grasses and a low Sr concentration. For periods with lower Sr/Ca values (c.2200–1900 bce and 19th–20th centuries ce ) there is additional textual and isotopic evidence for food transportation from outside the river valley, supporting the interpretation of Sr/Ca values as a proxy for food provenience in this specific area.     

Diatom-inferred salinity changes in relation to Holocene sea-level fluctuations in estuarine environments of Argentina

Espinosa, M.A., Hassan, G.S. & Isla, F.I., September 2012. Diatom-inferred salinity changes in relation to Holocene sea-level fluctuations in estuarine environments of Argentina. Alcheringa 36, 377–391. ISSN 0311-5518.

The analysis of diatoms from three sedimentary sequences in the Quequén Grande River basin (Buenos Aires province, Argentina) has allowed the reconstruction of local and regional palaeosalinity changes in relation to Holocene sea level fluctuations. An established diatom-based salinity transfer function is used in combination with autecological methods to reveal a maximum sea level between ca 7000 and 6000 ¹⁴C years BP. This marine influence was recorded in deposits exposed 2 km and 12 km upstream, but not 32 km from the mouth. The fossil diatom assemblages are characteristic of an estuarine lagoon with maximum inferred salinities of 15‰. When the Holocene transgression began to flood the former valley (ca 7000 ¹⁴C years BP), brackish lagoons evolved into estuarine settings in the lower valley, but shallow freshwater ponds with salinities <4‰ persisted at 32 km from the mouth.     

A comparison between the Mediterranean climates of Eurasia and the Americas

On the 19th and 20th September 1981 heavy rain fell throughout Scotland. Almost 140mm was recorded for the 24 hours up to 9.00 am on the 20th at Dundonnell in Wester Ross, an event with a recurrence interval of approximately 120 years. The storm generated a peak discharge of c.60m³ s‐¹ on the Ardessie Burn which drains a 13.3km² catchment on the northwestern slopes of An Teallach. The resulting flood caused severe localised bank erosion and partially destroyed a fish farm. The total volume of measured flood deposits exceeded 1800 tonnes, approximately equal to 14 years normal average annual non‐dissolved sediment output. The identification of specific sediment source areas and deposition sites allows an assessment of geomorphic work in terms of direct landscape adjustment in response to extreme rainfall. The flood stresses the importance of rare events in the landscape evolution of upland environments and the influence of antecedent catchment conditions.     

Geomagnetic storms in the Antarctic F-region. I. Diurnal and seasonal patterns for main phase effects

New analysis procedures are used to show that the main phase mid-latitude storm effects conform to consistent patterns in local time when suitable selection rules are applied, with averaging over several years. Changes in $\text{ƒoF2}$, with respect to estimated quiet-time values, are analysed in terms of a_p(τ), a new geomagnetic index derived to take account of integrated disturbance. Reduction of $\text{ƒoF2}$ is greatest during the early morning hours, in summer, at higher geomagnetic latitudes, near solar minimum and through the more active periods. The various dependencies are quantitatively determined for the first time by creating an average ‘steady state’ disturbance, rather than following specific storm events. This approach will permit tests of competing theories using available modelling programs.     

‘Torrents of Terror’: the August 1998 Storm and the Magnitude,Frequency and Impact of Major Floods in the Illawarra Region of New South Wales

The Illawarra Region some 80 kilometres south of Sydney is characterised by a prominent coastal escarpment that rises to 700 m within 12 km of the coast and forms a locus for frequent, high intensity rainfall events. One of the most recent recorded events occurred on 17 August 1998 with rainfall intensities at several pluviometers exceeding 120 mm hr^‐1 over a duration of one hour, with up to 249 mm falling in 3.5 hours during the main storm burst. Detailed pluviometer data indicate that the storm was non‐stationary and moved down catchment producing a widespread zone of 120 mm hr^‐1 intensity rainfall over a 30 minute duration across mid‐lower catchment areas after similar intensity but longer duration rainfall in catchment headwaters. Slope‐area reconstructions of peak discharge indicate that small catchments on the escarpment within the zone of maximum intensity experienced close to 100% rainfall‐runoff relationships, with peak discharges correlated to short duration (<1 hr) peak rainfall intensities. Widespread erosion occurred particularly where urban development had encroached on natural water courses. Debris/hyperconcentrated flows originating from both anthropogenic and natural sediment sources caused damage to urban areas. This paper provides an overview of the spatial and temporal characteristics of the 17 August 1998 storm, the hydrologic and geomorphic response of the streams, and the nature of damage to urban areas. It reassesses the frequency of recent high‐magnitude rainfall/flood events in the region, discussing the relationships between rainfall intensities, estimates of flood magnitudes and stormwater channel capacities.     

Dating problems in Icelandic archaeology

For many decades tephrochronology has been used as a scientific method for dating archaeological as well as geological remains in Iceland. Recently, parts of the tephrochronology for the eruptions of the famous volcano Hekla have been questioned by the author. This is due to obvious differences in dating results of archaeological artefacts from the valley of Thjórsárdalur in southern Iceland and the current tephrochronological dating of its devastation. While the devastation of the valley has been dated to AD 1104 and is thought to have been caused by a huge eruption of mount Hekla in that year, the artefacts from excavations and stray finds, as well as new ¹⁴C results, show somewhat later 12th‐13th century dates. The paper deals with this obvious discrepancy, which has hitherto been ignored, together with the results of archaeological excavations in 1983–86 at Stóng in Thjórsárdalur; it also gives a critical analysis of the historical methodology of the tephrochronologists.     

The solar eclipse of 26 February 1979: analysis and modelling of primary pair production,electron density and ionic composition

The solar eclipse of 26 February 1979 was observed from Red Lake, Canada, (52 °N, 91 °W) where totality occurred at about 1053 local time. Several research groups and government agencies participated in an extensive ground- and rocket-based observational program directed at the middle atmosphere. At the time of the eclipse, an extensive geomagnetic storm was in progress and the middle atmosphere was undergoing temperature and circulation changes associated with a stratospheric warming. Concurrent observations of atmospheric constituents, solar radiation, electron flux and other middle atmosphere parameters were obtained as inputs for a D-region predictive chemical computer code, DAIRCHEM, tailored to eclipse conditions. Ion pair production rates were computed by an E-region infrared radiance model and were used as necessary source function input values for DAIRCHEM computations. The computations yielded predictions of electron and total positive ion densities about totality. The positive ion measurements of a supersonic Gerdien condenser and a subsonic blunt probe during the eclipse were in agreement with the model computations and provided normalizing summations of total positive ions for the interpretation of mass spectrometer measurements. The chemical computer code identified principal routes for increase and removal of key species such as O₂⁺, NO⁺, hydrated clusters and negative ions. The dominant precursor ion for pair production hydrates was O₂⁺ and the chemistry was characteristic of the disturbed D-region.     

Magnetic field of the magnetospheric ring current and its dynamics during magnetic storms

This review examines models existing in the literature which describe the magnetic field produced by the ring current (DR) at the Earth's surface based on the energy balance equation. The parameters of this equation, the injection function F and decay parameter τ are considered to depend on parameters of the interplanetary medium and the DR intensity. The existing models are shown to be able to describe the DR variations with sufficient accuracy (r.m.s. deviation δ between the experimental and modelled values of DR for 170 magnetic storms is 5 < δ < 15 nT and the correlation coefficient between the two is 0.85 <r<1). The models describe that part of the geomagnetic field variation at low latitudes during a magnetic storm that is controlled by the geoeffective characteristics of the interplanetary medium and which thus responds immediately to its variations (the driven part).The values of τ are significantly less during the main phase of a magnetic storm than during the recovery phase. This reflects the difference in the main mechanisms of ion loss from the ring current during the two phases of the storm. These are the interaction of ions with hydromagnetic waves during the main phase of the storm with its intervals of intense plasma injection into the inner magnetosphere and charge exchange with the cold hydrogen geocorona during the recovery phase.     

Fisherfolk and farmers: Carbon and nitrogen isotope evidence from Middle Horizon Ancón,Peru

This study investigates human dietary patterns and economic trends at the coastal site of Ancón, Peru during the Andean Middle Horizon (550AD –1000AD ) using stable isotopic data from 32 individuals buried at the site. δ¹³C and δ¹⁵N results from human bone collagen and δ¹³C from human tooth enamel and bone carbonate indicate that inhabitants consumed a mixed diet composed primarily of marine protein and C₄ resources, with only marginal reliance on C₃ foods. Over time, Ancóneros appear to have relied more heavily on C₄ resources, particularly maize, despite the fact that the crop could not have been grown locally. These results are notable given that C₃ rather than C₄ or marine foods dominate the site's archaeological record. These data suggest that Ancón's inhabitants either had access to more fertile land up‐valley where maize could be cultivated successfully or that they engaged in trade relationships with their valley neighbours. A third possibility is that increased maize consumption at Ancón during the Middle Horizon resulted from Wari imperial influence and interregional exchange. Comparisons of δ¹³C values in enamel and bone carbonate from Ancón individuals indicate that δ¹³C_{carb_enamel} values are significantly more positive than δ¹³C_{carb_bone} values. This suggests that the diets of young children were systematically enriched in ¹³C compared to that of adults, perhaps as a result of nursing activity and/or differential dietary practices among various age groups at the site. Copyright © 2009 John Wiley & Sons, Ltd.     

The Excavations at Tel 'Eton (2006–2009): A Preliminary Report

Abstract

Tel 'Eton, commonly identified with biblical 'Eglon, is a large site in the trough valley in the southeastern Shephelah. Since the summer of 2006, Bar-Ilan University has been carrying out a large-scale exploration project at the site and its surroundings. The excavations were preceded by a detailed mapping of the site, which was subsequently divided into 39 sub-units. This was followed by survey and shovel tests in each of those units, and by full-scale excavations in four excavation areas. It appears that the site was first settled in the Early Bronze Age, and again in the Middle Bronze Age to the late Iron Age (8^th century BCE). Following a settlement gap in the 7^th–5^th centuries BCE, the site was resettled for a short period in the late Persian or early Hellenistic period. Among the major finds is a thick Assyrian destruction layer (8^th century BCE), which sealed many houses with their content, including many pottery vessels, metal artifacts, and botanical material (some still within the vessels), and many additional finds. The present article summarizes the results of the explorations of the site in 2006–2009.     

HOLOCENE ACCUMULATION OF COLLUVIAL AND ALLUVIAL SEDIMENTS IN THE WEIßE ELSTER RIVER VALLEY IN SAXONY,GERMANY*

Geoarchaeological investigations at two archaeological excavation sites lead to new results with respect to the Holocene landscape development of an archaeologically important loess landscape of Central Europe. Colluvial and alluvial sediments were sampled during archaeological excavations on the valley edge of the Weiße Elster and dated by means of ¹⁴C, TL and dendrochronology, and on the basis of archaeological finds. Thus, for the first time, the development of a valley edge of a river in the Leipzig area, which has been continuously settled for 7300 years, can be reconstructed. The first soil erosion on the valley edge is established towards the end of the Atlantic period. During the High Middle Ages, a colluvial sediment developed. Its deposition time can be limited to between ad 1000 and 1100. The flood loam near Großstorkwitz, which can be stratified by means of the soil and colluvial deposits, originated in the late Sub‐Boreal and early Sub‐Atlantic, as well as after ad 1100. During the first millennium ad, a soil developed in the older flood loam, which indicates a phase of reduced flood loam sedimentation.     

Aquatic resources in human diet in the Late Mesolithic in Northern France and Luxembourg: insights from carbon,nitrogen and sulphur isotope ratios

We investigated the contribution of freshwater resources to the diet of seven Late Mesolithic hunter-gatherers (ca. 5300–7000 BC) from Northern France and Luxembourg using stable isotope ratios. In addition to the carbon and nitrogen stable isotope ratios (δ¹³C, δ¹⁵N), we explored the potential of the sulphur isotopic ratios (δ³⁴S) to detect and quantify the proportion of protein derived from aquatic foodstuff. In only two sites, animal remains from an associated settlement were available and subsequently examined to decipher the isotopic differential between terrestrial and freshwater resources. The quantification of their relative contribution was simulated using a Bayesian mixing model. The measurements revealed a significant overlap in δ¹³C values between freshwater and terrestrial resources and a large range of δ¹⁵N values for each food category. The δ³⁴S values of the aquatic and terrestrial animals were clearly distinct at the settlement in the Seine valley, while the results on fish from Belgium demonstrated a possible overlap in δ³⁴S values between freshwater and terrestrial resources. Local freshwater ecosystem likely contributed to ca. 30–40 % of the protein in the diet of the individuals found in the Seine settlement. Out of this context, the isotopic signature and thus contribution of the available aquatic foods was difficult to assess. Another potential source of dietary protein is wild boar. Depending on the local context, collagen δ³⁴S values may contribute to better assessment of the relative contribution of freshwater and terrestrial resources.