Late-glacial and postglacial vegetational history of the Berkshires, western Massachusetts

A pollen analytical investigation of the sediments of Berry Pond, Berkshire County, Massachusetts, has demonstrated a sequence of pollen assemblage zones similar to those detected elsewhere in New England. From about 13,000 to 12,000 yr B.P. the vegetation of the region was treeless, probably tundra. By 11,500 yr tundra had been replaced by open boreal forest. Closed boreal forest became dominant by 10,500 yr. Boreal forests were replaced by mixed coniferous and deciduous forests with much white pine about 9600 yr ago. A “northern hardwoods” complex with much hemlock, beech, and sugar maple succeeded the mixed forests 8600 yr ago. Hemlock declined very rapidly approximately 4800 yr ago and was replaced by birch, oak, beech, ash, and red maple. This decline may have been biologically rather than climatically induced. There is a slight maximum of pine (much of it pitch pine) from 4100 to 2600 yr ago, perhaps indicative of warmer and/or drier conditions. There were slight changes in the forests about 1600 yr ago as chestnut immigrated and spruce and larch increased slightly. European land clearance and subsequent land abandonment are detectable in the uppermost levels.     

Skeletal halites from the Jurassic of Massachusetts, and their significance

Pseudomorphs after skeletal halite occur in a bed of Lower Jurassic lacustrine shale at Holyoke, Massachusetts. The pseudomorphs include pagoda types similar to those described by Southgate and show dissolution furrows. However the shales were deposited in a permanently subaqueous rather than an emergent environment, and the pseudomorphs accordingly grew in brine-saturated sediment. Evaporation to dryness is not therefore essential to the genesis of skeletal halite.     

Regional significance of pre-Wisconsinan till from Nantucket Island, Massachusetts

A major pre-Wisconsinan glacial event is the only possible source of the lower till on Nantucket Island, Massachusetts. The till occurs near the late Wisconsinan drift border and below fossiliferous marine beds of oxygen-isotope stage 5 (Sangamonian) age. It is considered to be Illinoian in age, but the evidence is tenuous. The till is correlated with the lower till of New England, and its presence supports the view that the New England upper and lower tills represent two glaciations. The pre-Wisconsinan (lower) till in New England may correlate with older tills elsewhere in the northeastern United States and in southeastern Canada that are considered to be early Wisconsinan or older in age.     

Sterol diagenesis in Recent sediments from Buzzards Bay,Massachusetts

Sections of a 42 cm core from one area and surface sediments from two other areas of Buzzards Bay, Massachusetts were analyzed for sterols. The distribution of sterols in surface sediments appears to be influenced by benthic faunal composition or factors controlling this composition. A comparison of sterols extracted by Soxhlet-extraction with sterols extracted after subsequent saponification of the sediment showed that the former sterols decrease in concentration while the latter saponified sterols increase in concentration with depth. In both fractions, the individual sterol compositions are similar. A transformation between Soxhlet-extractable and non-Soxhlet-extractable saponified sterols appears to be occurring over the 130 yrs sampled by the core. This transformation is probably due to chemical/physical processes rather than biological processes. Comparison with fatty acid data shows that early diagenesis of sterols is slower than early diagenesis of fatty acids.     

Eocene spheroidal dolomite from the western Sirte Basin, Libya

Scanning electron micrographs of crypto-crystalline (< 4 μm) dolomites found in cores taken from the lower Eocene Facha Member reservoir of the Zella and Aswad fields in Libya show that they consist of tiny globular bodies mixed with anhedral crystals, producing a chalky texture. The sedimentary sequence indicates deposition in upper intertidal/supratidal arid environments and in saline lagoons. The crypto-crystalline dolomite is facies-controlled and probably formed as a primary precipitate, similar to those reported from present-day subaqueous environments in the Coorong of South Australia and Holocene supratidal crusts off Florida. Such chalky-textured dolomites could form local fluid-migration barriers within hydrocarbon reservoirs.     

High-K volcanism in the Afyon region, western Turkey: from Si-oversaturated to Si-undersaturated volcanism

Volcanic rocks of the Afyon province (eastern part of western Anatolia) make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 Ma. The early-stage Si-oversaturated volcanic rocks around the Afyon city and further southward are trachyandesitic volcanic activity (14.23 ± 0.09 Ma). Late-stage Si-undersaturated volcanism in the southernmost part of the Afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages. Melilite–leucitites (11.50 ± 0.03 Ma), spotted trachyandesites, tephryphonolites and lamproites (11.91 ± 0.13 Ma) formed in the first episode; trachyandesites in the second episode and finally phonotephrites, phonolite, basaltic trachyandesites and nosean-bearing trachyandesites during the last episode. The parameter Q [normative q-(ne + lc + kls + ol)] of western Anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10–15 Ma. The magmatism experienced a sudden change in the extent of Si saturation after 14 Ma, during late-stage volcanic activity of Afyon volcanic province at around 12 Ma, though there was some coexistence of Si-oversaturated and Si-undersaturated magmas during the whole life of Afyon volcanic province.     

Arenig trace fossils from the Salamanca area,western Spain

Trace fossils are recorded at two localities from the ‘Armorican Quartzite’ (Lower Ordovician) in the Salamanca area, western Spain. Sixteen ichnospecies, belonging to twelve ichnogenera, are described; all ichnospecies occur in the upper part of the unit, only four in the lower part. The ichnogenera comprise Arthrophycus, Cruziana, Daedalus, Didymaulichnus, Diplichnites, Diplocraterion, cf. Gor-. dia, Monomorphichnus, Muensteria, Palaeophycus, Planolites, and Rusophycus. The presence of Cruziana furcifera, C. goldfussi, C. rugosa, and C? cf. imbricata indicate that the upper part of the unit is of Arenig age. The lower part has yielded only the two former ichnospecies and may extend down into the Tremadoc. The species of Cruziana and their stratigraphical significance are discussed.     

Micas from the Khaluta carbonatite deposit,western Transbaikal region

The Khaluta carbonatite deposit located in the western Transbaikal region was formed during the Late Mesozoic rifting in the southern framework of the Siberian Craton. Carbonatite is associated with shonkinite and syenite and is accompanied by fenitization. The composition of mica in more than 160 samples of country rocks, carbonatites, silicate rocks, and fenites was studied. The Fe³⁺ and Fe²⁺ contents, as well as oxygen isotopic composition, were determined. The Mg and Fe contents increase, whereas the Ti and Al contents decrease in micas when passing from silicate rocks and fenites to carbonatites. Micas from carbonatites are depleted in Al, enriched in Fe³⁺, and distinguished by high Si and F contents. According to our calculations, in some cases Al replaces Si in the tetrahedral site instead of replacement of Fe³⁺ as is characteristic of tetraferriphlogopite. Formally, the mica from carbonatites falls within the tetraferriphlogopite field, but typical inverse pleochroism is not always observable. The δ¹⁸O values of micas from carbonatite, shonkinite, syenite, and fenite are similar to those of mantle-derived silicate minerals. The δ¹⁸O values in the minerals coexisting with phlogopite testify to their isotopic equilibrium and make it possible to calculate the crystallization temperature of carbonatite.     

High-resolution compositional mapping of matrix phases: implications for mass transfer during crenulation cleavage development in the Moretown Formation,western Massachusetts

High-resolution compositional maps provide a new tool for investigating mass transfer during cleavage formation. The Moretown Formation of western Massachusetts contains a well-developed crenulation cleavage with alternating mica-rich crenulation limbs and mica-poor crenulation hinges. Compositional mapping shows two generations of plagioclase, the second of which was synchronous with the crenulation cleavage. A significant amount of the syn-crenulation plagioclase (10–20% modally) grew in hinge domains. A small amount of syn-crenulation plagioclase (∼1%) and a large amount of phengitic muscovite grew in limb domains. The maps also show that uncrenulated domains experienced mass transfer and reactivation of older cleavages, and thus cannot be used as ‘undeformed’ reference domains for comparison with crenulated regions. Compositional mapping facilitates a new degree of integration between petrologic and structural analysis. Knowledge of the structural context of compositional domains allows better selection of phases and compositions for interpreting metamorphic reactions and linking metamorphism to deformational stages. Knowledge of syntectonic reactions provides new insights into mass transfer and volume change during deformation. In the Moretown Formation, plagioclase- and phengite-producing reactions play a large role in controlling the nature and magnitude of mass transfer, but microstructures control the location of reactants and products within the evolving fabric.     

Experiences from the planning,construction and supporting of a road tunnel subjected to heavy rockbursting

Summary A 5360 m long road tunnel along a fjord with mountains rising steeply up to 1500 meters above sea level has recently been completed in Norway. 3 km of the tunnel was subjected to rockbursting caused by high and anisotropic stresses in the Precambrian gneisses. During the construction it was necessary to install 15 000 rock-bolts. Steelfibre reinforced shotcrete was successfylly applied for the first time to help stabilize the spalling rock. Supporting measures were only needed for the half of the tunnel closest to the fjord. 2600 m³ shotcrete was used.The paper outlines the preinvestigations and the design approach used for tunnels subjected to high and anisotropic stresses, and gives information about the construction and the support works carried out. A tunnel mapping system is described together with a classification of rockbursting activity in tunnels. Stresses in the rock were calculated by the use of finite element models and measured with doorstopper cells and the CSIR three-dimensional gauge. Comparisons of calculated and measured stresses are carried out.Rockbursting activity as observed along the tunnel is related to the estimated and observed stresses as well as to the properties of the rocks. Simple classification systems are used to correlate the results. Experiences from the use of the support are given.     

A comprehensive approach to the study of methane-seep deposits from the Lincoln Creek Formation, western Washington State, USA

ABSTRACT A comprehensive approach using palaeontology, petrography, stable isotope geochemistry and biomarker analyses was applied to the study of seven small methane‐seep carbonate deposits. These deposits are in the Oligocene part of the Lincoln Creek Formation, exposed along the Canyon and Satsop Rivers in western Washington. Each deposit preserves invertebrate fossils, many representing typical seep biota. Authigenic carbonates with δ¹³C values as low as ?51‰ PDB reveal that the carbon is predominately methane derived. Carbonates contain the irregular isoprenoid hydrocarbons 2,6,11,15‐tetramethylhexadecane (crocetane) and 2,6,10,15,19‐pentamethylicosane (PMI), lipid biomarkers diagnostic for archaea. These lipids are strongly depleted in ¹³C (δ¹³C values as low as ?120‰ PDB), indicating that archaea were involved in the anaerobic oxidation of methane. Small filaments preserved in the carbonate may represent methanotrophic archaea. Archaeal methanogenesis induced the formation of a late diagenetic phase, brownish calcite, consisting of dumbbell‐shaped crystal aggregates that exhibit δ¹³C values as high as +7‰ PDB. Clotted microfabrics of primary origin point to microbial mediation of carbonate precipitation. Downward‐directed carbonate aggregation in the seeps produced inverted stromatactoid cavities. Large filaments, interpreted as green algae based on their size, shape, arrangement and biomarkers, imply that deposition occurred, in places, in water no deeper than 210 m.     

Inferences from a corrosion study of a bronze cannon,applied to high level nuclear waste disposal

A bronze cannon was used as an analogue of corrosion processes for Cu. The cannon has been embedded in clay sediments in the Baltic Sea since 1676. Corrosion products are cuprite and malachite, mainly derived from transformation of tenorite inclusions of the bronze alloy. The bronze matrix exhibits little corrosion and a conservative estimate for the maximum corrosion of Cu is <10 mm in 100,000 a. Mechanisms for the chemical corrosion processes are suggested.     

A tunnel section through a prograding Namurian (Arnsbergian,E2a) delta,in the western Bowland fells,north Lancashire

The Wyresdale Tunnel was driven through Roeburndale Grit Group sediments in the western Bowland Fells. An Arnsbergian age for the strata is confirmed in a palynological study. The tunnel provided a section through a prograding delta front sequence, and proved the Roeburndale Grit Group to be much thicker than previously recorded. Syndepositional instability within the deltaic sediments is illustrated by slumps and debris slides. A comparison is made with modern deltas. It is suggested that the regional variation in sediment thickness is tectonically controlled.     

U-Pb zircon,Rb-Sr and Sm-Nd geochronology of high- to very-high-pressure meta-acidic rocks from the western Alps

Three meta-acidic rocks from the western Italian Alps, a magnesiochloritoid-bearing metapelite from the Monte Rosa massif, a coesite-pyrope-quartzite from the Dora Maira massif and the Monte Mucrone granite in the Sesia Zone, have been studied by U-Pb zircon, Rb-Sr on whole-rock, apatite and phengite and Sm-Nd wholerock methods. The mineral parageneses of the investigated rocks indicate high- to very-high-pressure and medium-to-high-temperature metamorphism. This combined isotopic study has enabled us to constrain the ages of magmatic and metamorphic events and also to compare the behaviour of U-Pb zircon systems in three intensely metamorphosed areas of the Pennine domain. The U-Pb zircon data have yielded a magmatic age for the Monte Mucrone granite at 286±2 Ma. This result confirms the occurence of late-Hercynian magmatism in the Sesia Zone, as in other Austro-Alpine units and in other areas of the European crystalline basement. In the Monte Rosa massif, a geologically meaningless lower intercept age of 192±2 Ma has been interpreted as an artefact due to a complex evolution of the U-Pb zircon system. The magmatic shape of the zircons implies a magmatic or volcano-sedimentary protolith for this rock, originally considered as a metasediment. The very-high-pressure metamorphism in the Dora Maira quartzite has produced an opening of the U-Pb zircon system at 121+12–29 Ma. The Rb-Sr data support the occurence of high-grade metamorphism during Cretaceous times. Phengites model ages are slightly younger than the U-Pb zircon lower intercept ages due to cooling phenomena or possible response of the phengites to a later deformation. The Nd model ages from the whole-rock samples, as well as the U-Pb upper intercept ages from zircons of all three investigated rocks, indicate the presence of Proterozoic crustal components inherited from the precursors of these meta-acidic rocks. The studied zircon populations and their U-Pb systems apparently showed open-system behaviour only when affected by extreme metamorphic conditions (700–750° C, > 28 kbar), whereas eclogite-facies conditions of 500–550° C and 14–16 kbar were not enough to disturb significantly the U-Pb zircon evolution. It is also probable that the sedimentary or magmatic origin of the protoliths of these meta-acidic rocks, which involved different characteristics such as grain-size and fluid phase concentration and composition, could be another important factor controlling the U-Pb zircon system behaviour during metamorphic events.     

Proterozoic metavolcanics from western Sierras Pampeanas terrane, Argentina

A series of medium grade metamorphic rocks of the western sector of the Sierras Pampeanas Terrane in central western Argentina are represented by amphibolites, gneisses and schists derived from sedimentary as well as from igneous rocks. The metavolcanics consist of amphibolites, quartz-K-feldspar-muscovite schists, and hornblende-biotite and biotite-epidote-plagioclase schists. Based on petrographic and geochemical data they are interpreted as originating as basaltic tholeiites, rhyolites and mesosilicic volcanics. The distribution and geochemical behavior are similar to present day western Pacific lavas, mainly those developed on island arcs or heavily attenuated continental crust. Based on these characteristics, an accretionary tectonic model involving a series of island-arc collisions is proposed for the Proterozoic. The complex Proterozoic tectonic history of the western Sierras Pampeanas has been partially obliterated by the emplacement of the Early Paleozoic magmatic arc rocks.     

Late Vistulian insect assemblages from Zabinko, western Poland

Insect analysis was carried out in deposits from a Late Vistulian site at Zabinko, western Poland. Geomorphological, lithostratigraphical and palaeobotanical investigations have been carried out earlier at the same section and published elsewhere. The analysed samples are dated from c. 12,600 to 12,200 BP. A total of 54 insect taxa were determined, the majority being Coleoptera. No major change in the insect fauna during this 400 years period could be detected from the study. The presence of specific phytophagus beetles suggests the same local vegetational environment as reconstructed from the plant macrofossil record, namely a shallow pool with a well-developed reed vegetation. The pool was situated in an open landscape with scattered trees and herb vegetation. The climatic reconstruction from the insect assemblages suggests a cool temperate climate with an average July temperature of 14–15C, During the same time period arctic/ksubarctic conditionsd, with mean July temperatures of c. 10–12C, prevailed in southernmost Scandinavia. The climatic amelioration in western Poland seems to have started possibl 500 years earlier than in southern Sweden.     

Geochemical interactions resulting from carbon dioxide disposal on the seafloor

The storage of CO_2(liquid) on the seafloor has been proposed as a method of mitigating the accumulation of greenhouse gases in the Earth's atmosphere. Storage is possible below 3000 m water depth because the density of CO_2(liquid) exceeds that of seawater and, thus, injected CO_2(liquid) will remain as a stable, density stratified layer on the seafloor. The geochemical consequences of the storage of CO_2(liquid) on the seafloor have been investigated using calculations of chemical equilibrium among complex aqueous solutions, gases, and minerals. At 3000 m water depth and 4°C, the stable phases are CO_2(hydrate) and a brine. The hydrate composition is CO₂·6.3H₂O. The equilibrium composition of the brine is a 1.3 molal sodium-calcium-carbonate solution with pH ranging from 3.5 to 5.0. This acidified brine has a density of 1.04 g cm⁻³ and will displace normal seawater and react with underlying sediments. Seafloor sediment has an intrinsic capacity to neutralize the acid brine by dissolution of calcite and clay minerals and by incorporation of CO₂ into carbonates including magnesite and dawsonite. Large volumes of acidified brine, however, can deplete the sediments buffer capacity, resulting in growth of additional CO_2(hydrates) in the sediment. Volcanic sediments have the greatest buffer capacity whereas calcareous and siliceous oozes have the least capacity. The conditions that favor carbonate mineral stability and CO_2(hydrates) stability are, in general, mutually exclusive although the two phases may coexist under restricted conditions.The brine is likely to cause mortality in both plant and animal comunities: it is acidic, it does not resemble seawater in composition, and it will have reduced capacity to hold oxygen because of the high solute content. Lack of oxygen will, consequently, produce anoxic conditions, however, the reduction of CO₂ to CH₄ is slow and redox disequilibrium mixtures of CO₂ and CH₄ are likely. Seismic or volcanic activity may cause conversion of CO_2(liquid) to gas with potentially catastrophic release in a Lake Nyos-like event. The long term stability of the CO_2(hydrate) may be limited: once isolated from the CO_2(liquid) pool, either through burial or through depletion of the CO₂ pool, the hydrate will decopose, releasing CO₂ back into the sediment-water system.