Rietveld Structure Refinement of the Apophyllite Crystals from Deccan Basalt Plateau Using X-ray Powder Diffraction Data

The crystal structure of a rare sample of natroapophyllite from Pune district (western India) located in the Deccan Basalt Plateau has been refined using X-Ray powder diffraction data and the Rietveld method. The Rietveld refinement was carried out using the computer program Diffracplus TOPAS 4.1. The pseudo-Voigt (pV) profile function was used for the fit of the peaks. The Rietveld refinement of the analyzed sample in space group Pnnm (No.58): a=8.94771 Å, b=8.98013 Å, c=15.78878 Å, Z=2, confirm the basic natroapophyllite structure. The chemical composition of the apophyllite crystals from Pune region (India) was determined by EDX analysis. The paper presents a new set of the unit cell parameters and fractional coordinates that define the natroapophyllite crystal structure. The quality of the sample analyzed was pristine, the sample being collected from an association of apophyllite-stilbite crystals of centimetric dimensions. Keywords: natroapophyllite, crystal structure, X-rays diffraction, EDX, Rietveld method

ESTABILIDADE DE CANAIS FLUVIAIS EM TORNO DE PONTES E BUEIROS NA BACIA HIDROGRÁFICA DO PARANÁ III, OESTE DO PARANÁ - EVALUATION OF THE CHANNEL STABILITY IN BRIDGES AND CULVERTS IN PARANÁ III WATERSHED, WESTERN PARANÁ STATE, BRAZIL

As obras de engenharia como pontes, pontilhões e bueiros acarretam mudanças nos processos fluviais que afetam o equilíbrio morfodinâmico e a estabilidade dos canais. O presente trabalho se propõe avaliar o nível de estabilidade dos canais fluviais em torno das citadas obras de engenharia na bacia hidrográfica do Paraná III situada na região Oeste do Estado do Paraná, adotando a metodologia da FHWA (2006). A área da bacia é de 7.979,4 km² e nela predominam rochas basálticas da Formação Serra Geral (Cretáceo) que integram o Terceiro Planalto Paranaense. O nível de estabilidade do canal foi analisado em torno de 46 estruturas (18 pontes, seis pontilhões, 15 bueiros celulares de concreto e sete bueiros tubulares de concreto), todas situadas em estradas federais, estaduais e municipais asfaltadas. Dentre os pontos analisados, 13 estruturas foram classificadas como de nível Excelente e 33 como de nível Bom. Em torno das pontes e pontilhões o número de canais com níveis Excelente e Bom foram iguais, enquanto que nos bueiros predominaram amplamente os níveis Bom, mostrando que as primeiras estruturas criaram menos impactos nos canais fluviais do que os bueiros. Não foi registrado nenhuma estrutura com estabilidade Regular ou Pobre. O predomínio de altos níveis de estabilidade é creditado ao afloramento do substrato basáltico no leito e a baixa erodibilidade dos solos das margens (Nitossolos e Neossolos) conferindo maior estabilidade ao canal. ABSTRACTThe bridges and culverts alter the natural conditions of rivers, causing changes in fluvial processes. The level of stability of river banks and beds around crossing structures was evaluated in the Paraná III watershed, Western region of Paraná State (Brazil), adopting the methodology of FHWA (2006). A watershed has an area of 7,979.4 Km2 and it predominantly basaltic rocks of the Serra Geral Formation (Cretaceous) that make up the basalt plateau with altitudes ranging between 220 and 725 m. The degree of channel stability was analyzed at 46 structures (18 bridges, 15 culverts box, 7 culverts pipe and 6 small bridges). We selected all crossings structures located in the Paraná III watershed along paved roads, positioned outside the urban area. Among the crossings structure, 13 were classified as excellent level of stability and 33 as good level. It was not registered any points with regular or poor stability. The prevalence of high levels of stability is credited to the outcrop of basalt substrate in bed and the low erodibility of the banks soils (Oxisols and Ultisols) providing greater stability to the channel in the vicinity of the structures.

The origin of glacial alpine landscape in Tröllaskagi Peninsula (North Iceland)

The Tröllaskagi peninsula is located in north central Iceland, between meridians 19º30’W and 18º10’W , limited by Skagafjödur fiord to the west and the Eyjafjödur fiord to the east, jutting out into the North Atlantic to latitude 66º12’N and linked to the central Icelandic highlands to the south. The peninsula is a Tertiary basalt plateau topped by flat summits with altitudes of 1000-1500 m, intensely dissected by the drainage network. The aim of this present study is to synthesize the recent advances in our understanding of the landscape and its dynamics in the Tröllaskagi peninsula and find the origin of its significant difference from the rest of Iceland. Results of the most recent research suggest the situation of Tröllaskagi as ice-free, delimited by the two great glacial outlets flowing down from the Icelandic Ice Sheet through the Skagafjödur and Eyjafjödur fiords, from at least the Oldest Dryas to the end of the Early Preboreal. Inland in Tröllaskagi, the glaciers formed in the north-facing cirques without losing their alpine characteristics during the Late Pleistocene and Holocene. The advances of these glaciers during the Oldest, Older and Youngest Dryas and the Early Preboreal were only a few hundred metres greater than the most important advance in the second half of the Holocene, during the Little Ice Age. Only a few of these glaciers remained debris-free and are sensitive to the minor climate oscillations. The rest, due to the important geomorphological activity on their walls, developed into debris-covered and rock glaciers and lost this significant dynamism.

Paleoenvironment of Jawa basalt plateau, Jordan, inferred from calcite speleothems from a lava tube

This paper explores the environmental conditions that faced the people of ancient Jawa during the Holocene, as well as previous prehistoric periods of the mid-late Pleistocene. Calcite speleothems in a lava tube are dated using the U-Th method, to marine oxygen isotope stage 7 from ∼ 250 to 240 ka and from ∼ 230 to ∼ 220 ka; and the stage 5/4 transition between ∼ 80 and 70 ka. The available evidence indicates general aridity of the Black Desert during most of the mid-late Quaternary, punctuated by short wetter periods, when the Mediterranean cyclonic systems intensified and penetrated the north Arabian Desert. These Mediterranean systems had a longer and more intense effect on the desert fringe closer to the Mediterranean and only rarely penetrated the Black Desert of Jawa. The results do not exclude some increase of rainfall which did not change water availability dramatically during the warm Holocene. The ancient Jawa city appears to have depended on technological ability to build elaborate runoff-collection systems, which became the prime condition for success.

The regional distribution of zeolites in the basalts of the Faroe Islands and the significance of zeolites as palaeotemperature indicators

The first maps of the regional distribution of zeolites in the Palaeogene basalt plateau of the Faroe Islands are presented. The zeolite zones (thomsonite-chabazite, analcite, mesolite, stilbite-heulandite, laumontite) continue below sea level and reach a depth of 2200 m in the Lopra-1/1A well. Below this level, a high temperature zone occurs characterised by prehnite and pumpellyite. The stilbite-heulandite zone is the dominant mineral zone on the northern island, Vágar, the analcite and mesolite zones are the dominant ones on the southern islands of Sandoy and Suðuroy and the thomsonite-chabazite zone is dominant on the two northeastern islands of Viðoy and Borðoy. It is estimated that zeolitisation of the basalts took place at temperatures between about 40°C and 230°C. Palaeogeothermal gradients are estimated to have been 66 ± 9°C/km in the lower basalt formation of the Lopra area of Suðuroy, the southernmost island, 63 ± 8°C/km in the middle basalt formation on the northernmost island of Vágar and 56 ± 7°C/km in the upper basalt formation on the central island of Sandoy. A linear extrapolation of the gradient from the Lopra area places the palaeosurface of the basalt plateau near to the top of the lower basalt formation. On Vágar, the palaeosurface was somewhere between 1700 m and 2020 m above the lower formation while the palaeosurface on Sandoy was between 1550 m and 1924 m above the base of the upper formation. The overall distribution of zeolites reflects primarily variations in the maximum depth of burial of the basalt rather than differences in heat flow. The inferred thinning of the middle and upper basalt formation from the central to the southern part of the Faroes is in general agreement with a northerly source area for these basalts, centred around the rift between the Faroes and Greenland. The regional zeolite distribution pattern is affected by local perturbations of the mineral zone boundaries that reflect local differences in the temperature, perhaps related to the circulation of water in the underground. The zonal distribution pattern suggests that these temperature anomalies are in part related to NW–SE-trending eruption fissures or zones of weakness separating the present islands and are subparallel to transfer zones in the Faroe–Shetland Basin. Both the regional and the local distribution of zeolite assemblages are probably a reflection of the basic volcanic-tectonic pattern of the Faroe Islands.

Excavations at Mad Mans Window, Glenarm, Co. Antrim: Problems of Flint Exploitation in East Antrim

This study examines the archaeological significance of the material from a group of Neolithic chipping floors rescued during the rebuilding of the Antrim coast road, at Mad Mans Window, south of Glenarm, Co. Antrim. It shows that the lithic production strategies vary significantly between assemblages although it is presumed that they are all Neolithic in date and come from the same area of coast. It is apparent that flint axe production was of limited importance on these sites and that in spite of the abundance of flint available along the Antrim coast, relatively few polished flint axes were manufactured. Instead the numerous flint caches found in adjacent parts of the north-east of Ireland tend to produce scrapers and blades. Hoards containing arrowheads may be confined to the Bronze Age.Around 300 polished flint axes and roughouts are known from Ireland. These are frequently small and only partially polished. A limited number of highly polished axes with ground flat side facets have been designated sub-type A. The tendency to use porcellanite rather than flint for axe manufacture may be due to its ability to withstand robust shock.During the last 100 years, the role of flint as a key resource in the stone age of north-eastern Ireland has always been recognized but this has usually led to an uncritical assumption as to the paramount importance of flint. Work in recent years has shown that its significance in attracting and retaining Mesolithic settlement may have been over-emphasized.The role of the flint industries in the Irish Neolithic in this region has never been properly assessed, either in relation to older Mesolithic manufacturing traditions or in the broader context of supply to the Neolithic communities of this part of Ireland.In particular, good or even reasonable quality flint is usually only exposed in Cretaceous outcrops along a narrow strip on the edge of the basalt plateau and, therefore, has a very limited availability in parts of Co. Antrim as well as parts of Counties Down and Deny. As a contrast, erratic and beach flint is available in some quantity down the east coast of Ireland from Co. Down to Wexford. A second potential constraining factor is that unlike Britain, where flint was exploited for axe manufacture in the east and other rocks in the west, flint sources and porcellanite for axe manufacturing are both found adjacent to each other in the same corner of Co. Antrim. In particular, a number of more substantial chipping floors of Neolithic age are known, e.g. the opencast quarry sites at Ballygalley Head. The purpose of this study is to assess the role of flint production on the Antrim coast with particular reference to its significance in the Neolithic. This topic will be developed in the context of an analysis of the material found at Mad Mans Window near Glenarm.

The dykes and sills of the Early Tertiary Faeroe Island basalt plateau

ABSTRACTThe Early Tertiary basalt plateau of the Faeroe Islands is cut by dykes and sills. Chemical analyses show a two-fold division of the intrusive rocks into a group of low-TiO2 (0·73–1·93%), MORB-type tholeiitic basalts and a group of high-TiO2 (2·09–3·90%) tholeiitic basalts. The low-TiO2 group comprises about 15% picrites and olivine-phyric basalts and 85% plagioclase-phyric basalts, and shows a chemical range largely explicable in terms of low-pressure fractional crystallisation of olivine ± plagioclase ± clinopyroxene. The high-TiO2 group is strongly dominated by plagioclase-phyric basalts with only few olivine-phyric compositions. The chemical trends are less regular than those formed by the low-TiO2 basalt dykes and a number of subgroups may be identified on the basis of bulk rock chemistry. Dykes belonging to a specific subgroup were probably fed from the same magma chamber.Petrographically and chemically the dykes and sills are clearly related to the upper 2·5 km of the lava sequence. Field evidence suggests that some of the dykes were contemporaneous with the exposed lavas, while other dykes and the sills were intruded in response to a slight doming of the plateau during the final stages of volcanic activity. Our investigations demonstrate that high-TiO2 and low-TiO2 magmas were both emplaced until the very end of magmatism, with the latter being mainly concentrated in the northern part of the archipelago. We briefly sketch a possible relationship between the supposed NE-Atlantic mantle plume, the distribution of the various magma types and the location of the Early Tertiary continental splitting zone north of the islands.