surface mass balance of small glaciers on james ross island north eastern antarctic peninsula during 2009 2015 two small glaciers on james ross island the north eastern antarctic peninsula experienced surface mass gain between 2009 and 2015 as revealed by field measurements a positive cumulative surface mass balance of 0 57 0 67 and 0 11 0 37 m w e was observed during the 2009 2015 period on whisky glacier and davies dome respectively the results indicate a change from surface mass loss that prevailed in the region during the first decade of the 21st century to predominantly positive surface mass balance after 2009 10 the spatial pattern of annual surface mass balance distribution implies snow redistribution by wind on both glaciers the mean equilibrium line altitudes for whisky glacier 311 16 m a s l and davies dome 393 18 m a s l are in accordance with the regional data indicating 200 300 m higher equilibrium line on james ross and vega islands compared with the south shetland islands the mean accumulation area ratio of 0 68 0 09 and 0 44 0 09 determined for whisky glacier and davies dome respectively is similar to the value reported for vega island and within the range of typical values for high latitude glaciers

pleistocene glacial relief of the central part of mt prokletije albanian alps abstract the central and highest area of mt prokletije albanian alps is situated in northern albania and eastern montenegro at 42 30 n the highest peak is maja e jezerces 2694 m detailed geomorphological mapping was used to reconstruct the positions of former glaciers the longest ropojana glacier had a length of 12 5 km and surface of 20 km 2 others include valbona glacier 9 5 km 10 5 km 2 grbaja glacier 5 km 6 7 km 2 and bogicevica glacier 6 km 6 9 km 2 three series of moraines can be distinguished the lowest at an average altitude of 990 m average ela 1750 m the middle series at 1350 m ela 1942 m and the highest at 1900 m ela 2123 m as no advanced dating methods have yet been used to provide a numerical chronological framework for these features hypotheses are made based on the comparison with the advanced studies of other similar mountains in the mediterranean region the moraines of the first stage lowest series correspond to one of pre lgm glaciations middle or even early wurmian the second stage moraines probably correspond to lgm and the third stage could be attributed to younger dryas the mapping included a number of inactive and active rock glaciers as well as three small active glaciers surface 5 ha and less at 1980 2100 m altitude in the area close to maja e jezerces

tectono sedimentary evolution of the southern branch of the western tethys maghrebian flysch basin and lucanian ocean consequences for western mediterranean geodynamics the evolution of the oceanic maghrebian flysch basin and its continuation in the southern apennines was studied by reconstructing mainly representative stratigraphic successions in all sectors a common evolution has been identified rifting and drifting phases are indicated by remnants of oceanic crust jurassic limestones cretaceous palaeogene turbiditic and pelagic deposits the pre orogenic sedimentation was mainly controlled by extensional tectonics and sea level changes the occurrence of a generalized foredeep stage since the early miocene is testified by thick siliciclastic and volcaniclastic syn orogenic flysch successions the deformation of the oceanic areas began in the burdigalian and the resulting nappes were stacked in the growing chains during the middle miocene piggy back basins developed and the building of the chains was accomplished in the late tortonian areal distribution and ages of flysch deposits represent an important tool for the study of the diachronous growth of the accretionary wedges

depositional systems composition and geochemistry of triassic rifted continental margin redbeds of the internal rif chain morocco the middle to upper triassic redbeds at the base of the ghomaride and internal dorsale calcaire nappes in the rifian sector of the maghrebian chain have been studied for their sedimentological petrographic mineralogical and chemical features redbeds lie unconformably on a variscan low grade metamorphic basement in a 300 m thick upward fining and thinning megasequence successions are composed of predominantly fluvial red sandstones with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine grained micaceous siltstones and massive mudstones with some carbonate and evaporite beds this suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems middle triassic to muddy flood and coastal plain deposits the successions are characterized by local carbonate and evaporite episodes in the late triassic the growth of carbonate platforms is related to the increasing subsidence norian rhaetian during the break up of pangea and the earliest stages of the western tethys opening carbonate platforms became widespread in the sinemurian sandstones are quartzose to quartzolithic in composition testifying a recycled orogenic provenance from low grade palaeozoic metasedimentary rocks palaeoweathering indices chemical index of alteration chemical index of weathering and plagioclase index of alteration suggest both a k enrichment during the burial history and a source area that experienced intense weathering and recycling processes these processes were favoured by seasonal climatic alternations characterized by hot episodically humid conditions with a prolonged dry season these climatic alternations produced illitization of silicate minerals iron oxidation and quartz rich red sediments in alluvial systems the estimated burial temperature for the continental redbeds is in the range of 100 to 160 c with lithostatic tectonic loading of ca 4 to 6 km these redbeds can be considered as regional petrofacies that mark the onset of the continental rift valley stage in the western pangea middle triassic before the opening of the western part of tethys in the middle jurassic the studied redbeds and the coeval redbeds of many alpine successions betic tellian and apenninic orogens show a quite similar history they identify a mesomediterranean continental block originating from the break up of pangea which then played an important role in the post triassic evolution of the western mediterranean region

influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas abstract dmowska r and lovison l c 1992 influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 23 43 we have investigated the influence of large scale fault inhomogeneities in large subduction earthquakes on the style of deformation and seismic behavior of the incoming oceanic plate and slab at intermediate depths during the earthquake cycle the zones of the large subduction events of rat islands 1965 alaska 1964 and valparaiso 1985 have been searched for earthquakes with m b 5 0 if available and for time periods as long as possible it has been found that in general the seismicity in the incoming oceanic plate clusters in front of asperities areas of highest seismic moment release and strongest locking and is positioned relative to them in the direction of plate motion it is usually lacking in areas adjacent to non asperities that is to zones that slip during the main event but with appreciably smaller seismic moment release and possibly slip seismically aseismically during the whole cycle similar behavior occurs in the downgoing slab at intermediate depths where seismicity during the cycle clusters but less strongly than in the oceanic crust next to asperities and down dip from them we infer that the locking of asperities causes higher stresses associated with the earthquake cycle itself to occur in areas adjacent to asperities both up dip and down dip from them along the direction of plate motion and that such stressing is much less pronounced in the areas adjacent to non asperities this opens the possibility of identifying the areas of highest seismic moment release in future subduction earthquakes and carries implications for where the highest deformation and possibly precursory phenomena and or nucleation of a future event might occur

geochemistry of permian triassic shales in the salt range pakistan implications for provenance and tectonism at the gondwana margin abstract upper permian and lower triassic griesbachian dienerian smithian and spathian shales in the salt range pakistan were deposited at the margin of gondwana during a time of active rifting xrf and inaa major element trace element and rare earth element ree analyses of shales exhibit progressive change in chemistry from upper permian to spathian sio 2 al 2 o 3 decreases upsection and k 2 o na 2 o increases together with an increase in the chemical index of alteration cia hfs elements are enriched relative to paas at the base of the sequence but are progressively depleted upward most compatible elements are depleted throughout relative to paas sc however is relatively enriched producing a general decline in th sc upward with the exception of a single sample at the base of the sequence ree shows little variation from upper permian to smithian ranging from 159 to 146 but increases to 206 in the spathian chondrite normalised la n yb n also increases upsection from 9 0 to 12 8 eu eu values are 0 48 0 54 in the upper permian dienerian sequence but anomalies become smaller 0 53 0 65 and more similar to paas 0 66 in the smithian and spathian such values are typical of continentally derived sediments but the slight decrease upward suggests a small influx of more mafic material this and decreasing th sc contrasts with increasing la n yb n and ree which imply an increasingly felsic source these anomalies may be resolved by modeling potential sources using the ree and th sc the modeling suggests that the permian dienerian sediments could have been derived from a source of upper proterozoic crust upc phanerozoic granite pg and amphibolite amp in ratios around 60 38 2 in the smithian and spathian proportions change to 76 20 4 and 68 28 4 respectively although the increase in the amp component is small when combined with increase in upc at the expense of pg it is sufficient to approximate the changes in th sc and eu eu la n yb n ratios in the permian dienerian may be influenced by concentrations of hree enriched garnet and zircon cia indices and a cn k relations show that source weathering conditions oscillated between non steady state permian dienerian smithian and steady state griesbachian spathian indicative of episodic uplift at the gondwana margin cia ratios in the spathian are greatest in the spathian indicative of more intense weathering at that time however a cn k relations ree contents and the modeled upc pg amp mix in the spathian could also have been produced by recycling of smithian sediments

climatic interpretation of alpine snowline variations on millennial time scales abstract the depression of snowlines or equilibrium line altitudes of alpine glaciers is often used by glacial geologists to infer variations in mass balance the climatic interpretation of snowline depression however is complicated by the number of factors that control glacier mass balance the simple lapse rate method of temperature interpretation ignores the effects of changes in radiation and snow accumulation the statistical approach to temperature interpretation which regresses precipitation and temperature against snowline altitude neglects the effect of radiation the most comprehensive approach for the climatic interpretation of snowline depression couples the heat and mass balances of a glacier surface a sensitivity analysis that utilizes the coupled heat and mass balance approach indicates that the 1000 m variation in snowline of alpine glaciers on glacial to interglacial time scales could be a result of significant changes in temperature and to a lesser extent changes in insolation snowline variations are sensitive only to relatively large changes in annual accumulation which should also be evident in other proxy records of moisture change the approaches outlined here provide glacial geologists with a summary of how various climatic forcings associated with glaciation may be quantified from snowline data

mass balance of himalayan glaciers using aar and ela methods the accumulation area ratio aar for himalayan glaciers representing zero mass balance is substantially lower than for north america and europe regression analysis suggests 0 44 for the aar representing zero mass balance in the western himalaya a good correlation was observed when this method was applied to individual glaciers such as gara and gor garang in himachal pradesh india the correlation coefficients r using 6 and 7 years of data respectively were 0 88 and 0 96 for gara and gor garang glaciers respectively however when data from six western himalayan glaciers were correlated the correlation was 0 74 the aar was also estimated by using landsat images which can be useful in obtaining a trend in mass balance for a large number of himalayan glaciers for which very little information exists a higher correlation was observed between equilibrium line altitude ela and mass balance the field data from gara and gor garang glaciers shows a high correlation coefficient i e 0 92 and 0 94 respectively the ela values obtained from the landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986 87 and negative for 1987 88

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

oblique strain partitioning and transpression on an inverted rift the castilian branch of the iberian chain the iberian chain is a wide intraplate deformation zone formed by the tectonic inversion during the pyrenean orogeny of a permian mesozoic basin developed in the eastern part of the iberian massif the n s convergence between iberia and eurasia from the late cretaceous to the lower miocene times produced significant intraplate deformation the nw se oriented castilian branch of the iberian chain can be considered as a key zone where the proposed models for the cenozoic tectonic evolution of the iberian chain can be tested structural style of basin inversion suggests mainly strike slip displacements along previous nw se normal faults developed mostly during the mesozoic to confirm this hypothesis structural and basin evolution analysis macrostructural bouguer gravity anomaly analysis detailed mapping and paleostress inversions have been used to prove the important role of strike slip deformation in addition we demonstrate that two main folding trends almost perpendicular ne sw to e w and nw se were simultaneously active in a wide transpressive zone the two fold trends were generated by different mechanical behaviour including buckling and bending under constrictive strain conditions we propose that strain partitioning occurred with oblique compression and transpression during the cenozoic 2008 elsevier b v all rights reserved

sequence stratigraphic analysis and paleogeographic interpretation of the buntsandstein and muschelkalk facies permo triassic in the se iberian range e spain abstract the iberian ranges is an alpine structure trending nw se in central spain they first appeared as small intracratonic basins in the early permian and experienced different periods of extensional tectonics during the mesozoic and cenozoic controlled by ancient hercynian or older fracture systems and at least two periods of compressive inversion tectonics the permian and triassic of the se iberian ranges are of germanic type within the prevailing buntsandstein and muschelkalk facies eight formations are recognized pollen and spore assemblages and some ammonoid horizons allow for age assessments ranging from thuringian late permian to carnian late triassic two phases of sedimentation can be distinguished during the early extensional period the first phase rift phase led to the development of the lower buntsandstein facies bounded by two angular unconformities and subdivided into two depositional sequences ds 1 and ds 2 the lower one is dominated by alluvial fans deposited in half grabens and the upper one by sandy braided rivers in more symmetrical grabens the second phase thermal or flexural subsidence phase led to the deposition of the uppermost buntsanstein rot and muschelkalk facies mostly shallow marine carbonates subdivided into two depositional sequences ds 3 and ds 4 with well developed lowstand transgressive and highstand systems tracts lst tst and hst intervals the criteria for separating systems tracts and the interplay of tectonics eustatism and rate of sedimentation are discussed ds 3 and ds 4 broadly correspond to 2 1 and 2 2 third order cycles but their limits are about 3 4 m y younger this may be explained by local tectonic factors

sedimentary fractionations between al ti and zr and the genesis of strongly peraluminous granites sedimentary sorting produces alternating shales and sandstones with complementary chemistries the preferential partitioning of quartz and zircon in the coarse grained fraction of the sediments results in a strong fractionation between sio 2 zr and other components al 2 o 3 tio 2 as a consequence shales may be defined chemically as having higher al 2 o 3 sio 2 and tio 2 zr ratios than their source rocks sandstones have the opposite characteristics and vary in composition according to the maturity of their source and the intensity of sorting processes most sedimentary suites display a good correlation between al 2 o 3 sio 2 and tio 2 zr this result is used to evaluate an average bulk composition for recent clastic materials and to model their composition on a ternary al ti zr diagram because the al 2 o 3 tio 2 ratio of igneous rocks is highly sensitive to magmatic differentiation igneous and sedimentary trends crosscut in the al ti zr di

palaeogeography facies and nomenclature of the triassic units in the different domains of the betic cordillera s spain abstract this paper reviews and discusses the different facies and nomenclature of the triassic in the betic cordillera s spain emphasis is placed on problems encountered when studying betic basin facies and palaeogeographic domains in triassic times the betic basin was positioned between the iberian and mesomediterranean plates we therefore propose the designations southiberian triassic and mesomediterranean triassic for the triassic rocks that crop out in the external and internal zones respectively of the cordillera although facies types vary substantially several similarities in their main stratigraphic features link the two palaeogeographic domains thus buntsandstein muschelkalk and keuper facies can be currently distinguished in both domains of the external and the internal zones of the betic cordillera most rocks were coastal and shallow marine sediments deposited across an extensive and varied palaeogeography which defines the sephardic domain for some epochs this last domain shows the influence of alpine fauna and even palaeogeographically gives rise to subdomains characteristic of alpine facies that today crop out in some internal zone units this variety of facies makes the study of the triassic in the betic cordillera all the more interesting

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

origin of the permian triassic iberian basin central eastern spain abstract the iberian basin was an intracratonic rift basin in central eastern spain developed since early permian times the basin boundary faults were normal listric faults controlling an asymmetric extension propagating northeast with time hercynian or older lineaments controlled the orientation of the iberian basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high the basin was related with the coeval ebro catalan and cuenca mancha basins and their connections are discussed subsidence curves show that the early permian early jurassic period of extension can be subdivided into three rifting episodes and a flexural one extension factor increases from 1 17 in the northwest to 1 29 near the mediterranean coast the increasing extension rate was accommodated by transfer faults trending nne ssw more important in the levante area the rift evolution is intermittent and seems to reflect distinct stress fields the collapse of the late hercynian orogen and related increased heat flux extension and rifting is the most probable origin of the iberian basin and related basins the origin of the catalan and the valencia prebetic basins is related to the southwards migration of the hesse burgundy rift along the eastern margin of the iberian microplate

the chemistry of barium anomalies in the berisal complex simplon region switzerland the petrographic and geochemical features of two zoisite celsian gneiss outcrops from the berisal complex characterised by a syn kinematic mineral assemblage that contains celsian and barium white micas and a maximum whole rock bao content of 8 36 wt are described the outcrops are enclosed in a larger body of garnet bearing two mica augen gneiss which has intrusive contacts with the surrounding garnet biotite muscovite paragneiss and also contains small outcrops of two mica clinozoisite gneiss the zoisite celsian gneisses are strongly enriched in all alkaline earth elements are depleted in the alkali elements and have high zr hf and nb ta ratios compared with the surrounding gneisses the zoisite celsian two mica clinozoisite and garnet bearing two mica augen gneisses have al cnk molar ratios 1 and the zoisite celsian gneisses are also enriched in zr y and nb chondrite normalised patterns for the rare earth elements ree show light ree enrichment with a negative eu anomaly on the basis of field and geochemical data it is argued that the barium anomalies in the berisal complex are the result of igneous fractionation of barium into anorthosite dominated cognate inclusions within a larger volume of calc alkaline peraluminous melt on the basis of u pb zircon ages a conservative estimate for the age of magma crystallisation is placed at 460 10 ma and thus was related to significant late ordovician granitoid magmatism in gondwana derived microcontinents during collision between avalonia cadomia and gondwana

the influence of source rock type chemical weathering and sorting on the geochemistry of clastic sediments from the quetico metasedimentary belt superior province canada abstract the geochemistry of clastic sediments is controlled by at least four factors source rock composition weathering of the source rocks sorting of the weathered detritus and post depositional alteration during diagenesis and metamorphism in order to evaluate the relative importance of these factors major trace and rare earth element contents were determined for distal and proximal clastic turbidites from the archaean quetico metasedimentary belt the degree of metamorphism of the samples ranges from middle greenschist to upper amphibolite facies simple mixing of archaean mafic and acidic rocks of similar composition to those found in the adjacent granite greenstone terrains will account for the tio2 feot mgo cr sc y and hree contents of the clastic turbidites the metasediments are enriched in lree relative to the mafic acidic rock mixing line indicating that the acidic source was enriched in the lree compared to archaean terrains from other parts of the world some quetico turbidites have an additional fe rich source component possibly a chemical sediment incorporated at the time of turbidite slumping cao na2o k2o rb and sr form trends on bivariant plots that are oblique to the mafic acidic rock mixing line and hence cannot be accounted for by simple mixing of the source rocks chemical weathering of feldspars prior to deposition can account for cao na2o k2o rb and sr trends since cao na2o and sr are lost to the weathering solutions and k2o and rb are retained on the product clays the higher na 2 o cao k 2 o na 2 o rb k 2 o and sr cao ratios but lower cao content of the distal samples suggest that they were derived from a bulk sediment that had experienced a greater degree of chemical weathering than the proximal sediments sorting is the factor that most strongly influences the composition of individual samples within the proximal sample group the coarse grained metagraywackes with their higher quartz feldspar and heavy mineral contents are enriched in sio2 cao na2o sr lree zr and hf relative to the fine grained clay rich metapelites metapelites are enriched in tio2 al2o3 feot mgo k2o cr zn sc y hree cs and rb as a result of their higher clay contents thus the use of clastic sediment compositions in determining average crustal compositions e g for the ree can only give satisfactory results when all grain size fractions are sampled in their correct relative proportions the chemical differences observed between the high and low grade samples can be accounted for by source rock type chemical weathering of the source rocks or sorting post depositional element mobility does not appear to be an important factor in determining the composition of the quetico metasediments

tectonic framework and extensional pattern of the malaguide complex from sierra espuna internal betic zone during jurassic cretaceous implications for the westernmost tethys geodynamic evolution mapping lithostratigraphic biostratigraphic and structural detailed analyses in sierra espuna area internal betic zone se spain have allowed us to reconstruct the jurassic cretaceous evolution of the westernmost mesomediterranean microplate palaeomargin and by correlation with other sectors northern rift central and western internal betic zone to propose a geodynamic evolution for the westernmost tethys extension began from late toarcian when listric normal faults activated these faults are arranged in three categories large scale faults separating hectometric cortical blocks main faults dividing the former blocks into some kilometre length blocks and secondary faults affecting the kilometric blocks this fault ensemble actually outcropping in the sierra espuna area broke the palaeomargin allowing the westerly tethyan oceanic aperture with an extension at about 17 2 extension was not homogeneous in time being the late toarcian to the dogger malm boundary the period when blocks underwent the greatest movement rifting phase leading to the drowning of the area 8 2 extension during the malm drifting phase extension followed 5 7 while during the cretaceous a change to pelagic facies is recorded with an extension of about 3 3 post drift stage this evolution in the westernmost tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low angle fault of the rifting

size specific steady state accumulation area ratio an improvement for equilibrium line estimation of small palaeoglaciers abstract characteristic distribution of the steady state accumulation area ratio aar0 of valley and corrie glaciers was investigated in a global dataset comprised of 46 glaciers there is a positive relationship between aar0 and glacier area with smaller glaciers having lower values of aar0 compared with larger glaciers the relationship between glacier area s and steady state aar of studied glaciers can be optimally described by a logarithmic regression equation this relationship is thought to be a globally valid approximation if the size of the glacier is not smaller than 10 1 km2 in the case of palaeoglaciers an aar0 value of 0 44 0 07 is best applied on glaciers with areas in the range 0 1 1 km2 0 54 0 07 for glaciers covering areas between 1 and 4 km2 and 0 64 0 04 for glaciers larger than 4 km2 this assumes insignificant debris cover for the investigated palaeoglaciers the proposed size specific aar0 values take into account the geometric hypsometric properties of palaeo glaciers the results have major importance for palaeoglaciological reconstructions in many regions of former marginal niche glaciation characterized by small former glaciers

gondwana derived microcontinents the constituents of the variscan and alpine collisional orogens abstract the european variscan and alpine mountain chains are collisional orogens and are built up of pre variscan building blocks which in most cases originated at the gondwana margin such pre variscan elements were part of a pre ordovician archipelago like continental ribbon in the former eastern prolongation of avalonia and their present day distribution resulted from juxtaposition through variscan and or alpine tectonic evolution the well known nomenclatures applied to these mountain chains are the mirror of variscan resp alpine organization it is the aim of this paper to present a terminology taking into account their pre variscan evolution at the gondwana margin they may contain relics of volcanic islands with pieces of cadomian crust relics of volcanic arc settings and accretionary wedges which were separated from gondwana by initial stages of rheic ocean opening after a short lived ordovician orogenic event and amalgamation of these elements at the gondwanan margin the still continuing gondwana directed subduction triggered the formation of ordovician al rich granitoids and the latest ordovician opening of palaeo tethys an example from the alps external massifs illustrates the gradual reworking of gondwana derived pre variscan elements during the variscan and alpine tertiary orogenic cycles

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

determining steady state accumulation area ratios of outlet glaciers for application of outlets in climate reconstructions abstract a steady state glacier equilibrium line altitude ela can be determined by the accumulation area ratio aar method aar varies with climate balance ratio and glacier type glacier geometry the method involves calculating steady state accumulation area ratios aar0 from mass balance characteristics of glaciers by statistical methods in order to confirm the application of linear regression to calculate aar0 in the case of outlet glaciers a method to reveal the mathematical relationship between annual net balance bn and aar was developed analyses carried out on bn aar data sets for 14 outlet glaciers showed that the best approximation for the bn aar relationship is linear with an average squared correlation coefficient of 0 786 but relatively strong non linearity was detected for several glaciers a possible explanation lies in the hypsometry of the observed glaciers results confirm the application of linear regression to calculation of aar0s for outlet glaciers an average aar0 of 0 58 was estimated as the type specific aar0 for outlet glaciers

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

former plateau ice fields in the godeanu mountains southern carpathians first evidence of glaciated peneplains in the carpathians abstract the existence of plateau ice fields in the southern carpathians has long been suggested due to the widespread presence of the bor scu surface in the region the bor scu surface is a peneplain consisting of flat plateaus in the elevation range of 1800 2200 m a s l it is present throughout the southern carpathians with the most typical appearance in the godeanu mountains these plateaus could have served as ice accumulation sites during the pleistocene glaciations as they were well above the steady state equilibrium line altitude ela 0 direct geomorphological evidence on the existence of plateau ice fields and thus well founded reconstructions are absent due to the lack of glacial landforms on the plateaus in order to test the existence of plateau ice fields a previous geomorphological survey and theoretical ice surface profiles based on a steady state perfectly plastic ice flow model were used based on these methods maps and three dimensional surface models of the former glaciers were created the ela 0 s of the paleoglaciers were estimated by the accumulation area ratio aar method according to our results three major ice fields on the central plateaus and several smaller ice fields on wide saddles were present in the godeanu mountains during the maximal glaciation the ice fields fed numerous surrounding valley glaciers several independent valley and cirque glaciers completely separated from the ice fields were also present further from the central mass of the mountain range the average ela 0 of the northern 1855 2 m a s l and the southern 1700 2 m a s l glaciers differed greatly we suggest that the surprisingly high average ela 0 of the northern glaciers was mostly caused by the missing lower sections of these paleoglaciers from our reconstructions due to the destroyed terminal glacial landforms however the terminal glacial landforms are quite well preserved in the southern valleys thus the average ela 0 of the southern paleoglaciers was suitable to correlate the maximal glaciation of the godeanu mountains with the maximal glaciation of the neighbouring retezat mountains

reconstruction of equilibrium line altitudes for tropical and sub tropical glaciers past fluctuations of tropical and sub tropical glaciers provide important palaeoclimate proxies for regions where other forms of evidence are rare however published equilibrium line altitude ela estimates for tropical and sub tropical glaciers at the lgm vary widely reflecting the diversity of methods and approaches employed by different research groups this complicates regional and global comparisons of ela estimates and emphasises the need for standardised methods the distinctive character of tropical and sub tropical glaciers however means that standard methods for reconstructing former glacier limits elas and palaeoclimate need to be adapted for local conditions many methods of ela reconstruction explicitly or implicitly make assumptions about glacier mass balance gradients and care needs to be taken that the choice of accumulation area ratios aars balance ratios brs and terminus to head ratios thars is appropriate as such indices are influenced by climatic regime debris cover and other factors ela reconstructions should employ multiple methods and should be cross checked and fully reported to allow assessment of the accuracy of ela estimates reliable glacier chronologies are equally important dating should be based on multiple radiometric techniques wherever possible and method of dating the type of material dated and the context of the date must all be reported

interpretation of neovolcanic versus palaeovolcanic sand grains an example from miocene deep marine sandstone of the topanga group southern california despite abundant data on volcaniclastic sand stone the compositional spatial and temporal distribution of volcanic detritus within the sedimentary record is poorly documented one of the most intricate tasks in optical analysis of sand stone containing volcanic particles is to distinguish grains derived by erosion of ancient volcanic rocks i e palaeovolcanic noncoeval grains from grains generated by active volcanism subaqueous and or subaerial during sedimentation neovolcanic coeval grains deep marine volcaniclastic sandstones of the middle topanga group of southern california are interstratified with 3000 m thick volcanic deposits both subaqueous and subaerial lava and pyroclastic rocks ranging from basalt andesite to dacite these rocks overlie quartzofeldspathic sandstones petrofacies 1 of the lower topanga group derived from deep erosion of a mesozoic magmatic arc changes in sandstone composition in the middle topanga group provide an example of the influence of coeval volcanism on deep marine sedimentation volcaniclastic strata were deposited in deep marine portions of a turbidite complex volcaniclastic apron built onto a succession of intrabasinal lava flows and on the steep flanks of subaerially emplaced lava flows and pyroclastic rocks distinctive petrofacies 2 5 directly overlying basalt and basaltic andesite lava flows petrofacies 2 is a pure volcanolithic sandstone including vitric microlitic and lathwork volcanic grains and neovolcanic crystals plagioclase pyroxene and olivine the abundance of quenched glass palagonite fragments suggests a subaqueous neovolcanic provenance whereas sandstones including andesite and minor basalt grains suggest subaerial neovolcanic provenance this petrofacies probably was deposited during syneruptive periods testifying to provenance from both intrabasinal and extrabasinal volcanic events deposited during intereruptive periods impure volcanolithic petrofacies 3 includes both neovolcanic 85 and older detritus derived from plutonic metamorphic and palaeovolcanic rocks during post eruptive periods the overlying quartzofeldspathic petrofacies 4 and 5 testify to progressive decrease of neovolcanic detritus 48 14 and increase of plutonic metamorphic and palaeovolcanic detritus the upper topanga group calabasas formation conformably overlying the middle unit has dominantly plutoniclastic sandstone petrofacies 6 neovolcanic detritus is drastically reduced 4 whereas palaeovolcanic detritus is similar to percentages of the lower topanga group petrofacies 1 the middle topanga group sandstones are vertically organized into four

interlaboratory standardization and calibration of day mineral crystallinity and crystallite size data clay mineral crystallinity and crystallite domain size data determined by x ray diffraction xrd are methods extensively used in the characterization of very low grade metamorphic conditions however the lack of sufficient interlaboratory standardization has made comparisons between different research groups unreliable due to significant variations in numerical results obtained a consequence of the different machine conditions measurement methods and sample preparations used during analysis a calibration approach to the standardization of data using rock chip standards is presented which allows data sets produced by different research groups to be directly and quantitatively compared a standardized scale the crystallinity index standard cis is proposed with illite crystallinity anchizonal boundary limits of 0 25d 2 and 0 42d 2 and equivalent illite crystallite sizes of 52 and 23 nm respectively determined by the warren averbach method calibrating both old and new data will enable more reliable comparisons between similar and contrasting geological environments and should improve the accuracy and reliability of correlations made between xrd data and other indicators of very low grade metamorphism hence increasing the value of such clay mineral studies

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

variscan tectonics in the malaguide complex betic cordillera southern spain stratigraphic and structural alpine versus pre alpine constraints from the ardales area province of malaga i stratigraphy abstract in the betic cordillera the pre alpine deformation in the paleozoic basements is rather poorly known at ardales several classic sections of the malaguide complex belong to two distinct superposed alpine tectonic units including both paleozoic basement and mesozoic tertiary cover rocks within the alpine footwall unit new stratigraphic studies allow the documentation of upper ordovician silurian and lower and middle devonian conodont associations in particular silurian lower devonian limestones rest on a devonian lower carboniferous succession by means of a tectonic contact the latter sealed by unconformable triassic redbeds consequently the tectonic superposition of the studied paleozoic successions is interpreted as the result of a variscan thrust the conodont color alteration index shows average values around 5 5 5 independent of the conodont association and age and the tectonic position of the studied samples this indicates that the malaguide paleozoic successions were affected

the mesozoic continental rifting in the mediterranean area insights from the verrucano tectofacies of southern tuscany northern apennines italy in the alpine mediterranean region the continental redbeds and shallow marine siliciclastics related to the early depositional phases of the late permian mesozoic continental rifting are referred to as the most common representative of the verrucano tectofacies the verrucano type successions exposed in southern tuscany are diachronous spanning from triassic to earliest jurassic in age and accumulated within the tuscan domain a paleogeographic region of continental crust that due to the opening of the piedmont ligurian ocean formed part of the adria passive margin they belong to the metamorphic verrucano group and the non metamorphic pseudoverrucano fm viewed overall these verrucano type successions appear to manifest five episodes or pulses of an ongoing continental rifting with the exception of the first episode that developed entirely within a terrestrial setting each one is represented by basal verrucano type continental siliciclastics overlain by compositionally mixed marine deposits which resulted from four diachronous post middle triassic transgressions this suite of tectonic pulses produced the progressive westward widening backstepping of the tuscan domain in the rifting south tuscany area

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

the glacial history of the dinaric alps montenegro abstract large areas of montenegro were glaciated during the pleistocene this paper presents evidence from the massifs of central montenegro including durmitor and sinjajevina moracke planine maganik prekornica and vojnik glacial deposits have been subdivided on the basis of morphostratigraphy and soil weathering and 31 u series ages from cemented tills provided a geochronological framework the largest glaciation occurred before 350 ka when a series of conjoined ice caps over the massifs of central montenegro covered a total area of nearly 1500 km 2 these formed during mis 12 and correspond with the largest skamnellian stage glaciations in greece to the south later middle pleistocene glaciations occurred during the penultimate glacial cycle correlating with the vlasian stage in greece mis 6 when ice caps covered an area of 720 km 2 over central montenegro there is also geochronological evidence of glacial deposits dating from the interval between mis 12 and mis 6 before the interglacial complex of mis 7 this glaciation appears to have been very similar in extent to that which occurred during mis 6 the last glacial cycle in central montenegro was characterised by valley and cirque glaciers covering a total area of 49 km 2 it is very likely that glaciers have been present in the mountains of central montenegro during every glacial cycle since a small glacier still survives today the smaller glaciers of the last glacial cycle are likely to have been associated with summer temperatures that were warmer than those of earlier cold stages the striking contrast in the extent and thickness of ice cover during the cold stages of the pleistocene has an important bearing on the geomorphological and biological evolution of the balkans

the palaeozoic evolution in the alps from gondwana to pangea more than 50 of the alps expose fragments of palaeozoic basement which were assembled during the alpine orogeny although the tectonic and metamorphic history of the basement units can be compared to that of the variscan crust in the alpine foreland most of the basement pieces of the alps do not represent the direct southern continuation of variscan structural elements evident in the massif central the vosges black forest or the bohemian massif the basement units of the alps all originated at the gondwana margin they were derived from a precambrian volcanic arc suture fringing the northern margin of gondwana from which they were rifted during the cambrian ordovician and silurian a short lived ordovician orogenic event interrupted the general rifting tendency at the gondwana active margin after the ordovician the different blocks drifted from the gondwana margin to their pangea position colliding either parallel to armorica with laurussia or with originally peri gondwanan blocks assembled presently in armorica from the devonian onwards many basement subunits underwent the complex evolution of apparently oblique collision and nappe stacking docking started in the external massifs the penninic and lower and middle austroalpine units in approximately devonian early carboniferous times followed by the upper austroalpine and the south alpine domains in the visean and the namurian times respectively wrenching is probably the best mechanism to explain all syn and post collisional phenomena since the visean followed by post orogenic collapse and extension it explains the occurrence of strike slip faults at different crustal levels the formation of sedimentary troughs as well as the extrusion and intrusion of crustal and mantle derived magmas and allows for contemporaneous rapid uplift of lower crustal levels and their erosion from the stephanian onwards all regions were deeply eroded by large river systems

triassic redbeds in the malaguide complex betic cordillera spain petrography geochemistry and geodynamic implications abstract sandstone petrography and mudstone mineralogy and geochemistry of triassic mudstones and sandstones from continental redbeds of the malaguide complex betic cordillera southern spain provide useful information on provenance palaeoclimate and geodynamics during the early stages of the pangea break up and on their diagenetic evolution the sandstones are quartzarenites to sub litharenites with minor lithic fragments and rare feldspars the mudstone samples show a paas like elemental distribution the samples likely record recycling processes from their metasedimentary basement rocks that significantly affected the weathering indices and monitors cumulative effects including a first cycle of weathering at the source rocks sandstone composition and chemical mineralogical features of mudstones record a provenance derived from continental block and recycled orogen that were weathered under warm and episodically wet climate source areas were located towards the east of the present day malaguide outcrops and were formed by fairly silicic rock types made up mainly of palaezoic metasedimentary rocks similar to those of the paleozoic underlying series with subordinate contributions from magmatic metamorphic sources and a rare supply from mafic metavolcanic rocks clay mineral distribution of mudstones is dominated by illite and illite smectite mixed layer that result from differences in provenance weathering and burial temperature history illite crystallinity values illitization of kaolinite occurrence of typical authigenic minerals and apatite fission track studies coupled with a subsidence analysis of the whole malaguide succession suggest burial depths of at least 4 6 km with temperatures of 140 160 c typical of the burial diagenetic stage and confirm the middle miocene exhumation of the betic internal domain tectonic stack topped by the malaguide complex

pleistocene ice caps on the coastal mountains of the adriatic sea ice caps once covered large areas of mount orjen 1894 m on the adriatic coast of montenegro bosnia herzegovina croatia the largest ice cap covered an area of c 165 km2 and reached a maximum ice thickness of c 450 m in some areas reaching down to 500 m above modern sea level u series dating of secondary carbonates within moraines indicates that the most extensive glaciation occurred during the middle pleistocene correlating with a major phase of glaciation in greece to the south during mis 12 c 480 430 ka later less extensive glaciations are also recorded in the cirques and valleys and correlate with glaciations during mis 6 190 130 ka and mis 5d 2 110 11 7 ka each phase of glaciation would have required large amounts of snow accumulation under modern precipitation values which at c 5000 mm are some of the highest in europe mean annual temperatures would need to be only c 5 6 c lower in order to form similar sized glaciers today a mean annual temperature depression of 12 13 c would still require 1000 mm of snow accumulation water equivalent to balance ablation suggesting sustained moisture supply during pleistocene cold stages such sustained precipitation supply during pleistocene cold stages is likely to have been facilitated by major temperature contrasts between the european landmass and the mediterranean sea which are likely to have sustained lee side vortices to the south of the alps in the gulf of genoa and adriatic sea forming weak moisture bearing depressions which tracked across the eastern adriatic coastal mountains large ice caps on the dinaric alps would have blocked the inland penetration of these depressions resulting in much drier conditions in the balkan interior creating favourable conditions for the deposition of thick accumulations of loess the last glaciers on orjen formed during the younger dryas 12 9 11 7 ka and confirm the influence of north atlantic ocean circulation on pleistocene climate change in this part of the mediterranean

new palaeomagnetic data from the betic cordillera constraints on the timing and the geographical distribution of tectonic rotations in southern spain a palaeomagnetic investigation has been carried out at 14 sites on jurassic red nodular limestones from the central and eastern part of the external zones of the betic cordillera subbetic and prebetic zones progressive thermal demagnetisation of samples from the subbetic zone reveals the presence of two stable magnetic components of the natural remanent magnetisation 1 a secondary neogene syn folding component and 2 the original jurassic magnetisation as similar characteristics have been reported in jurassic limestones from the western subbetic zone a widespread remagnetisation event took place within 106 years in the entire subbetic region during neogene times in contrast in the prebetic region no evidence for a secondary overprint has been detected palaeomagnetic jurassic declinations indicate variable and locally very large clockwise rotations 35 140 but the two sites in the north westernmost part of the investigated region are not rotated the use of both components of magnetisation and the incremental fold test results allowed the timing of block rotations in the subbetic zone to be constrained rotations in the western subbetic occurred after the acquisition of the secondary overprint whereas in the central part of the subbetic zone they were completed by the time of the remagnetisation event

sedimentary evolution of the mesozoic continental redbeds using geochemical and mineralogical tools the case of upper triassic to lowermost jurassic monte di gioiosa mudrocks sicily southern italy the continental redbeds from the internal domains of the central western mediterranean chains have an important role in the palaeogeographic and palaeotectonic reconstructions of the alpine circum mediterranean orogen evolution since these redbeds mark the triassic jurassic rift valley stage of tethyan rifting the composition and the sedimentary evolution of the middle triassic to lowermost jurassic continental redbeds of the san marco d alunzio unit peloritani mountains southern italy based on mineralogical and chemical analyses suggests that the studied mudrock sediments share common features with continental redbeds that constitute the internal domains of the alpine mediterranean chains phyllosilicates are the main components in the mudrocks the 10 a minerals illite and micas the i s mixed layers and kaolinite are the most abundant phyllosilicates the amount of illitic layers in i s mixed layers coupled with the illite crystallinity values ic are typical of high degree of diagenesis corresponding to a lithostatic tectonic loading of about 4 5 km the mineralogical assemblage coupled with the a cn k plot suggest post depositional k enrichments palaeoweathering proxies pia and ciw record intense weathering at the source area further the studied sediments are affected by reworking and recycling processes and as consequence it is likely these proxies monitor cumulative effect of weathering the climate in the early jurassic favoured recycling and weathering occurred under hot episodically humid climate with a prolonged dry season the source area is the low grade paleozoic metasedimentary basement mafic supply is minor but not negligible as suggested by provenance proxies