Associated conchs and opercula of Triplicatella disdoma (Hyolitha) from the early Cambrian of South Australia

Internal moulds of complete shells, including conch and associated opercula, of the hyolith Triplicatella disdoma from Cambrian Series 2, Stages 3–4 of South Australia are described. The conch of T. disdoma is shown to be narrow and cone-shaped, and with a rounded triangular cross-section. The conch shows a gentle dorsal curvature in lateral view. The fossils lack evidence of helens, and the operculum was smaller than the apertural diameter of the conch and could be withdrawn a short distance into the conch. Triplicatella was probably closely related to orthothecid hyoliths.     

Diffusion and kinetic control of weathering layer development

The formation of porous weathering rinds (layers of chemical alteration) on the exterior of rocks is a consequence of dissolution and precipitation of minerals occurring at the mineral–fluid interface within the pores. The speed at which the developed rind advances is controlled by both kinetic reaction rates and the transport of reaction products away from the pore spaces into the outside fluid. We show, using both reaction‐diffusion theory and numerics, that under diffusion limitations, the weathering rate depends on the size and curvature of the sample. This leads to a relationship between rind thickness, δ, and age, t. As the rind thickens, the result in three dimensions differs substantially from the one‐dimensional result of . We describe the conditions under which the one‐dimensional and diffusion‐limited approximations apply and how they evolve as the rock weathers. Under chemical kinetic limitations, the rind advances at a constant rate, dδ/dt = v. We defend the application of a spherical approximation to irregular non‐spherical rocks and apply our results to field observations reported in the literature to show consistency with established methods. Finally, we argue that the variability in size, as well as in mineralogy, over ensembles of grains contributes to heterogeneous weathering rates. We demonstrate that this heterogeneity can contribute to the aging, or gradual decrease with time, of weathering rates previously observed in laboratory and field measurements.     

A STUDY ON LATE MEDIEVAL TRANSPARENT‐GLAZED POTTERY AND ARCHAIC MAJOLICA FROM ORVIETO (CENTRAL ITALY)*

Nineteen samples of medieval transparent‐glazed pottery and archaic majolica from Orvieto (central Italy) were studied. They were classified by archaeological criterion as follows: five transparent‐glazed fragments with green and brown decorations (first half of the 13th century), eight green transparent‐glazed fragments (13th century) and six tin‐glazed fragments with green and brown decorations (second half of the 13th century). SEM–EDX, XRD (the Rietveld method) and XRF were used to characterize the chemical and mineralogical compositions both of the bodies and the coatings. In all of the samples, the paste is Ca‐rich with CaO contents as high as 13–20 wt%. The mineralogical composition is compatible with a firing temperature of about 950°C, which is the typical temperature reached in a wood kiln. No difference was observed between the bodies of transparent‐ and tin‐glazed pottery. In the case of transparent glazes, the burial conditions lead to heavy weathering of the samples. However, on the basis of the analyses carried out in non‐weathered areas, the typical composition is PbO 55–65 wt%, SiO₂31–35 wt%. In tin glazes, the tin is scattered on the mass of the glaze as SnO₂crystals with a concentration of 7–14 wt%. Concerning the decorations, it is established that the green colour is due to the presence of copper, while manganese is responsible for the brown colour. These pigments, which represent the typical colours of ‘archaic majolica’, are spread through the glaze homogeneously, apart from one case in which there is clear evidence of manganese oxide crystals.     

On The Medieval Antiquities of Anglesey

The excavations at Aulnat-Gandaillat are producing evidence of the pre-urban settlement system belonging to the last centuries B.C. The agricultural settlement was also engaged in industry, including the working of bronze, iron, gold, silver, glass, bone and possibly other substances such as coral. It is also providing us with the most refined chronology yet available from a La Tène settlement, and also with details of the development of trade with the Mediterranean world. The site was abandoned around 40–20 B.C. when the oppidum of Gergovie was founded.     

The Enisei River of Central Siberia in the Late Pleistocene

Recent Paleolithic work along the middle Enisei River of central Siberia has revealed a long history of occupation that almost certainly begins in the Middle Pleistocene. Although the evidence for the Lower Paleolithic is somewhat tentative, there is good reason to believe that hunter-gatherers had periodically occupied the middle Enisei before the last interglacial. The steppe environment of the region during the Upper Pleistocene was relatively bountiful; more than 200 Upper Paleolithic sites, both before and after the Last Glacial Maximum, have been located. The region appears to have been abandoned during the Last Glacial Maximum. Most of Soviet and Russian archaeological work has been guided by a cultural–historical orientation, but recently there has been increased interest in developing adaptationist and ecological research strategies. The middle Enisei and the wider central Siberian region are key to understanding early adaptations to the north and the dimensions of Paleolithic population movements.     

Cambrian–Ordovician non-marine fossils from South Australia

Newly discovered trace and body fossils from the Grindstone Range Sandstone of South Australia reveal evidence of megascopic life on land during the Cambrian–Ordovician. Arthropod trackways (Diplichnites gouldi) are interpreted here to have formed on land. The most persuasive evidence for this view is that footprints vary in clarity along the length of the trackway as it traversed moist then dry silt, then biological soil crust. Compatible, though not diagnostic of walking on land is trackway symmetry, without one side buoyed up by current. The footprints bulge outward and are partially filled with miniature talus cones. Footprints also are alternate as in walking, rather than opposite as in sculling. Arthropod resting traces (Selenichnites sp. indet.) have 11 lateral furrows, and footprints are bundled into sets of 8–11, most like euthycarcinoids. No arthropod dwelling burrows were found in associated palaeosols, so the track maker was more likely amphibious than fully terrestrial. Associated trace fossils include a new ichnotaxon of burrow, Myrowichnus arenaceus gen. et sp. nov. Thallose impressions (Farghera robusta gen. et sp. nov.) have the radiating dichotomous form of lichens, algae and liverworts. All these trace and body fossils were found in weakly developed palaeosols. Other palaeosols in the same formation are evidence of terrestrial ecosystems of modest biomass, weathering, carbon sequestration and stability in dry tropical regions.     

Constraining groundwater flow in the glacial drift and saginaw aquifers in the Michigan Basin through helium concentrations and isotopic ratios

³He and ⁴He concentrations in excess of those in water in solubility equilibrium with the atmosphere by up to two and three orders of magnitude are observed in the shallow Glacial Drift and Saginaw aquifers in the Michigan Basin. A simplified He transport model shows that in situ production is negligible and that most He excesses have a source external to the aquifer. Simulated results show that ³He and ⁴He fluxes entering the bottom of the Saginaw aquifer are 7.5 × 10^?14 and 6.1 × 10^?7 cm³STPcm^?2 yr^?1, both of which are lower than fluxes entering the underlying Marshall aquifer, 1.0 × 10^?13 and 1.6 × 10^?6 cm³STPcm^?2 yr^?1 for ³He and ⁴He, respectively. In contrast, He fluxes entering the Saginaw aquifer are higher than fluxes entering the overlying Glacial Drift aquifer of 5.2 × 10^?14 and 1.5 × 10^?7 cm³STPcm^?2 yr^?1 for ³He and ⁴He, respectively. The unusually high He fluxes and their decreasing values from the lower Marshall to the upper Glacial Drift aquifer strongly suggest the presence of an upward cross‐formational flow, with increasing He dilution toward the surface by recharge water. These fluxes are either comparable to or far greater than He fluxes in deeper aquifers around the world. Model simulations also suggest an exponential decrease in the horizontal groundwater velocity with recharge distance. Horizontal velocities vary from 13 to 2 myr^?1 for the Saginaw aquifer and from 18 to 6 myr^?1 for the Marshall aquifer. The highly permeable Glacial Drift aquifer displays a greater velocity range, from 250 to 5 myr^?1. While Saginaw ⁴He ages estimated based on the simulated velocity field display an overall agreement with ¹⁴C ages, ¹⁴C and ⁴He ages in the Glacial Drift and Marshall aquifers deviate significantly, possibly due to simplifications introduced in the He transport model leading to calculation of first‐order approximation He ages and high uncertainties in Glacial Drift ¹⁴C ages.     

Preservation of bird bones: erosion versus digestion by owls

Surface damage to bird bones from pellets of three species of owls (S. aluco, A. otus and B. bubo) was compared with that of bird bones exposed to weathering and soil corrosion (Záskogo Cave in the Western Balkan Mountains, Bulgaria and Ciemna Cave, southern Poland). Scanning electron microscopy and light microscope examinations indicate that the effects of weathering of bird bones (extensive pitting and flaking away on whole bones, holes with sharp edges, depressions with rough bottoms and sharp edges of breakage) are distinguishable from those of digestion (rounding of hole edges on articular ends and sometimes on shafts, rounding of breakage). However, soil corrosion may produce similar rounding to that of digestion, which may hamper taphonomic interpretations of fossil assemblages. Two stages of weathering in bird bone are distinguished. Generally, the kind of damage done to bird bones is similar to that done to mammalian remains. Taphonomic studies of fossil bird remains should take into account a combination of features, including surface damage, fragmentation and possible chemical alterations of bone tissues. © 1997 John Wiley & Sons, Ltd.     

Power of the Rank Adjacency Statistic to Detect Spatial Clustering in a Small Number of Regions

The rank adjacency statistic D is a statistical method for assessing spatial autocorrelation or clustering of geographical data. It was originally proposed for summarizing the geographical patterns of cancer data in Scotland (IARC 1985). In this paper, we investigate the power of the rank adjacency statistic to detect spatial clustering when a small number of regions is involved. The investigations were carried out using Monte Carlo simulations, which involved generating patterned/clustered values and computing the power with which the D statistic would detect it. To investigate the effects of region shapes, structure of the regions, and definition of weights, simulations were carried out using two different region shapes, binary and nonhinary weights, and three different lattice structures. The results indicate that in the typical example of considering Canadian total mortality at the electoral district level, the D statistic had adequate power to detect general spatial autocorrelation in twenty‐five or more regions. There was an inverse relationship between power and the level of connectedness of the regions, which depends on the weighting function, shape, and arrangement of the regions. The power of the D statistic was also found to compare favorably with that of Moran's I statistic.     

Hunting strategies in the Late Glacial of northern Europe: A survey of the faunal evidence

Presented here is a general overview of the evidence concerning the procurement strategies in the Late Glacial of northwestern Europe. Their rich faunal assemblages make Stellmoor and Meiendorf, in northern Germany, key sites in this respect. Both may be considered specialized reindeer hunting camps. A survey of the hunting techniques and exploitation patterns reflected by the material from these sites emphasizes the differences between the Hamburgian and the Ahrensburgian economies.     

The Changing Face of PEQ

Abstract

The spectacular relief of the sandstone inselbergs is maintained by an interplay of geological structure and weathering/erosion processes, in that vertical joints and faults provide the foci along which most weathering and erosion take place. There are three major varieties of sandstone breakdown; the first is failure of large rock masses along vertical joints, leading to rockfall. Associated with this process is the mechanical breaking of falling blocks upon impact, in some cases right down to the origjnal sand grains. Rockfall maintains vertical or steep slopes, provided basal talus is removed. The second variety is liberation of small blocks by weathering along closely-spaced joints and bedding planes. Rock prone to this style of erosion tends to be less steep and may have basal slopes buried by rubble. The third variety is grain by grain weathering by solution of cement. This process is the most fundamental, as it not only wears away the surfaces but attacks joints, leading to the processes described above. Grain by grain weathering is slowed or prevented on some surfaces by development of oxide rinds, particularly where run-off is concentrated.

These processes result in deposition of debris at slope bases, but in most cases the debris is quickly reduced to sand and removed by wind and water. Relatively clean slope bases allow slopes to retreat parallel to themselves. Where debris collects faster than it is reduced to sana, slope angles tend to decline until they reach the angle of repose of the debris.

Differences in structural expression of the various lithological units result in differing erosional characteristics. The Saleb Formation is typified by relatively gentle slopes littered with debris, due to thinly spaced joints. The Ishrin Formation, witll widely spaced vertical joints, is typified by rockfall of large masses. It is the major cliff-former. Grain by grain weathering, influenced by variations in varnish development, has produced spectacular tafoni on some Ishrin cliffs. The Disi Formation is extremely friable and although slopes are relatively gentle they are mostly rubble free. The Disi in many places forms rounded domelike shapes which may be due to exfoliation along pressure-relief joints. The Um Sahm Formation is highly fractured and similar in appearance to the Saleb.

Igneous rocks, where exposed below the sandstones, are undergoing chemical weathering, particularly along joints. The results are tors, tafoni, and large amounts of grüss.

The desert floor between inselbergs is in some places a bare bedrock surface with an integrated drainage network, and in other places a sand or playa surface. Running water seems to have been a major agent in shaping the floor, but is less important now than in the past. Transportation of sand by wind is common but there is no evidence for significant eolian aggradation or degradation at the present time.

A minimum rate of surface retreat by grain by grain weathering is 5 cm./1,000 years, based on weathering ofNabataean ruins. Overall slope retreat should be significantly greater, due to added effects of rockfall and removal of blocks by running water.     

Shifts Along a Spectrum: A Longitudinal Study of the Western Eurasian Realized Climate Niche

ABSTRACT

Climate niches that modern humans and earlier hominin ancestors occupied have changed dramatically over time, but the extent of those changes has gone largely undocumented. This study investigates the manner in which the realised hominin climate niche has expanded, contracted, or stayed stationary across four time periods (Last Interglacial, Last Glacial Maximum, Mid-Holocene, and 1950–2000) in Western Eurasia. Using spatially gridded general circulation model data and site locations this study examines climate variables from archaeological sites and current Western Eurasian cities to describe both the regional Western Eurasian fundamental and realised climate niches. Changes between the three prehistoric periods and modern-day time period are analysed by calculating each realised niche breadth, overlap, position, and variance. Results indicate that as global temperatures cooled from the Last Interglacial to Last Glacial Maximum, populations expanded their climate niche breadth beyond that of earlier Neanderthal groups, shifting toward regions with less seasonal variation. Conversely, Mid-Holocene humans, who saw the proliferation of both agriculture and population, contracted their realised climate niche space. The contraction and expansion of realised climate niche space illustrates how hominins have evolved the capacity to shift their niche through changes to their subsistence strategy and adaptations to overall climatic conditions.     

Estimates of Upper Palaeolithic meta-population size in Europe from archaeological data

Three databases (2961 georeferenced archeological sites, simulated climatic variables simulating a typical “warm” phase of the isotopic stage 3 (IOS3 project), and ethnographic of hunter–gatherers (HG)) were used to estimate the size, growth rate and kinetics of the metapopulation of HG during four periods of the Upper Paleolithic in Europe. The size of the metapopulation was obtained by multiplying a demographic density (per 100 km²) by the size of the population territory of HG. Demographic density for each period was calculated by successively backprojecting a reference density obtained for the Late Glacial with inter-period growth rate of the archeological sites. From the Aurignacian to the Glacial Maximum, the metapopulation remained in a positive quasi-stationary state, with about 4400–5900 inhabitants (95% confidence interval (CI95%): 1700–37,700 inhabitants). During the Glacial Maximum, the metapopulation responded to the cold: (i) by moving the northern limits of its maximum expansion zone towards the low latitudes by 150–500 km from west to east, (ii) by concentrating in few refuge zones (mainly Périgord, Cantabria and the Ibérian coasts), (iii) by becoming perhaps distributed in smaller groups than during the pre and post Glacial Maximum. The metapopulation reached 28,800 inhabitants (CI95%: 11,300–72,600) during the mid-Late Glacial recolonisation.     

Deglaciation and Human Colonization of Northern Europe

Few places worldwide experienced Late Glacial ecological shifts as drastic as those seen in the areas covered by, or adjacent to, the massive ice sheets that blanketed much of the northern hemisphere. Among the most heavily glaciated regions, northern Europe underwent substantial ecological shifts during and after the Last Glacial Maximum. The climatically unstable Pleistocene–Holocene transition repeatedly transformed far-northern Europe, placing it among the last regions to be colonized by Paleolithic societies. As such, it shares paleoenvironmental and archaeological analogues with other once glaciated areas where human populations, entrenched in periglacial environments prior to glacier retreat, spread into newly deglaciated territories. Perhaps most significant for northern Europeans were post-glacial effects of the Younger Dryas and Preboreal periods, as shifts in climate, plant, and animal communities elicited several adaptive responses including innovation, exploration, and the eventual settlement of once glaciated landscapes. This paper is a detailed review of existing archaeological and paleoecological evidence pertaining to the Late Upper Paleolithic of northern Europe, and offers theoretical observations on human colonization models and ecological responses to large-scale stadial and interstadial events.     

792 or 793? Charlemagne’s canal project: craft,nature and memory

In autumn 793, Charlemagne visited the fossatum magnum (the ‘big ditch’ or canal) between the Rhine and Danube. Excavations, dendrochronology and a re‐reading of Carolingian Annals shed new light on the chronology and setting of this canal, which was planned in 792, initiated in 793, and abandoned later that year. The abandonment is attested by both written and archaeological evidence. The different versions of the annals offer a unique opportunity for comparison with the archaeological record. Evidence that works of Vitruvius circulated in the Carolingian court suggests that Charlemagne’s advisers were drawing on classical tradition when they pitched the idea of digging the canal.     

Plato and the Theodosian Code

The codification project initiated in 429 ad that resulted in the Theodosian Code was originally designed to integrate three types of law: one, imperial constitutions since Constantine; two, the legal material collected in the tetrarchic Codices Gregorianus and Hermogenianus; and three, a florilegium of juristic writings and responsa. The ultimate aim was to condense all this in a single comprehensive law book that would govern the entire life of the empire and its subjects. As this paper shows, such a project had no precedent in Roman legal history and in fact ran counter to the traditional multiplicity of legal sources in Rome. This prompts a question: from where did the intellectual fathers of the codification project drew inspiration for such a revolutionary idea? In the paper's second part, I argue that one important model for the codification project of 429 could have been the legal code Plato designed for the ideal state of the Laws.     

Recovering the histories of women religious in England in the central Middle Ages: Wilton Abbey and Goscelin of Saint-Bertin

Building upon the efforts made by scholars over the past 20 years to enrich our understanding of the vibrancy and sophistication of the literary cultures fostered within English communities of women religious during the central Middle Ages, this article shows that these women kept their communities' histories and preserved their saints' cults through their own writing. The evidence for this is uncovered through comparative analysis of the two extant versions of the post-mortem miracles of the late Anglo-Saxon saint Edith of Wilton (c.961–c.984): the Vita et translatio Edithe, composed c.1080 by the Flemish hagiographer Goscelin of Saint-Bertin (c.1040–d. after 1107), and the early fifteenth-century Middle English Wilton Chronicle. This analysis reveals that the writer of the Chronicle depended on a collection of Edith's and other Wilton saints' miracles that was maintained by their consorors throughout the late tenth and eleventh centuries, independently of Goscelin's account.     

The geochemical evolution of very dilute CO2‐rich water in Chungcheong Province,Korea: processes and pathways

A geochemical study was carried out on the CO₂‐rich water occurring in granite areas of Chungcheong Province, Korea. In this area, very dilute and acidic CO₂‐rich waters [62–242 mg l^?1 in total dissolved solid (TDS), 4.0–5.3 in pH; group I) occur together with normal CO₂‐rich waters (317–988 mg l^?1 in TDS, 5.5–6.0 in pH; group II). The concentration levels and ages of group I water are similar to those of recently recharged and low‐mineralized groundwater (group III). Calculation of reaction pathways suggests that group I waters are produced by direct influx of CO₂ gas into group III type waters. When the groundwater is injected with CO₂, it develops the capacity to accept dissolved solids and it can evolve into water with very high solute concentrations. Whether the water is open or closed to the CO₂ gases becomes less important in controlling the reaction pathway of the CO₂‐rich groundwater when the initial pco ₂ is high. Our data show that most of the solutes are dissolved in the CO₂‐rich groundwater at pH > 5 where the weathering rates of silicates are very slow or independent of pH. Thus, groundwater age is likely more important in developing high solute concentrations in the CO₂‐rich groundwaters than accelerated weathering kinetics because of acidic pH caused by high pco ₂.     

Chemical Weathering of Detrital Sediments in the Taklamakan Desert,Northwestern China

Based on the analysis of major‐element compositions of detrital sediments from the Taklamakan Desert of northwestern China, this paper aims to study chemical weathering in a hyper‐arid desert environment. The major‐element compositions are basically similar to the Upper Continental Crust but show a clear enrichment of CaO and depletion of Na₂O and K₂O, indicating the enrichment of carbonates and the decomposition of sodium and potassium silicates. The indexes of chemical alteration are relatively low and correlate negatively with the content of Na₂O, implying that the degree of chemical weathering is weak and mainly controlled by the weathering of sodium feldspars. An A‐CN‐K model demonstrates that the detrital sediments from the Taklamakan Desert have a high homogeneity in the trend of chemical weathering. They are weathered less than sands and soil in many other Chinese deserts, and also less than similar detrital sediments in many other countries. This evidence suggests a low degree of mineralogical maturity in the Taklamakan Desert. The aeolian sediments of different ages have similar indexes of chemical weathering, suggesting that the degree of chemical weathering was consistent in the Taklamakan Desert throughout the period of aeolian deposition. The low degree of chemical weathering is caused principally by extreme aridity, rapid rejuvenation of detrital sediments associated with strong aeolian processes, and an intensive input of fluvial deposits, as well as a lack of vegetation. Due to the high concentration of erodible minerals, the desert is quite vulnerable to soil erosion and land degradation.