response of the indian ocean to the tibetan plateau thermal forcing in late spring abstractthe thermal effect of the tibetan plateau tp is known to exert substantial impacts on the atmospheric general circulation suggesting that it may also influence the wind driven circulatio

discriminating stacked distributary channel from palaeovalley fill sand bodies in foreland basin settings abstract stacked fluvial distributary channel deposits and palaeovalley fills can form major multi storey sand bodies with similar thicknesses and with lateral extents often greater than a single exposure consequently they can be difficult to tell apart from one another using outcrop data this study addresses this problem by quantitatively analysing the architecture of five stacked fluvial distributary channel deposits and two palaeovalley fills from the pennsylvanian pikeville and hyden formations of the central appalachian basin usa the a priori interpretation of the sand bodies as stacked distributary channels and palaeovalley fills is possible because a robust in place coal seam correlation framework allows for the recognition of different basin scale architectures for each type aspect ratios 1000 and a regional basinward facies shift at the bases of palaeovalley fills sand body thickness storey thickness position and length of storey contacts within the sand body are similar in both types however they can be distinguished by different up system to down system changes in their respective architectures stacked distributary channel sand bodies thin down system display a decrease in storey thickness an increase in the mean position of storey heights in the sand body and a decrease in the length of storey contacts these trends are the result of down system decrease in channel size and confinement associated with radially distributive fluvial systems palaeovalley fill sand bodies thicken down system display an increase in storey thickness a decrease in the mean position of storey heights and a decrease in the length of storey contacts the increase in sand body and storey thickness are the result of down system increases in original channel size consistent with trunk axial fluvial systems fed by tributaries that predominate during valley formation the down system increase in amalgamation reflects a down system decrease in accommodation from the higher subsidence rate active margin of the basin and is therefore not necessarily characteristic of palaeovalley fill architectures in all basin settings this study emphasises the requirement for detailed correlation work and quantitative analysis of external and internal architectures before the interpretation of sand bodies as stacked distributary channels or palaeovalley fills

mountains and arid climates of middle latitudes simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the northern hemisphere dry climates similar to those observed were simulated over central asia and western interior north america in the experiment with mountains whereas relatively moist climates were simulated in these areas in the absence of orography the experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs downstream of these troughs precipitation bearing storms develop frequently in association with strong jet streams in contrast both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains in addition orography reduces the moisture transport into the continental interiors from nearby oceanic sources the relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late tertiary before substantial uplift of the rocky mountains and tibetan plateau is believed to have occurred

the global climate response to lowering surface orography of antarctica and the importance of atmosphere ocean coupling abstracta global climate model is used to study the effect of flattening the orography of the antarctic ice sheet on climate a general result is that the antarctic continent and the atmosphere aloft warm while there is modest cooling globally the large local warming over antarctica leads to increased outgoing longwave radiation which drives anomalous southward energy transport toward the continent and cooling elsewhere atmosphere and ocean both anomalously transport energy southward in the southern hemisphere near antarctica poleward energy and momentum transport by baroclinic eddies strengthens anomalous southward cross equatorial energy transport is associated with a northward shift in the intertropical convergence zone in the ocean anomalous southward energy transport arises from a slowdown of the upper cell of the oceanic meridional overturning circulation and a weakening of the horizontal ocean gyres causing sea ice in the northern hemisphere to expand and the arctic to cool comparison wi

transgressive origin of channeled estuarine deposits in the point lookout sandstone northwestern new mexico a model for upper cretaceous cyclic regressive parasequences of the u s western interior 1 regionally correlatable regressions recorded in upper cretaceous strata from the united states western interior represent low order cyclic progradations of the epeiric seaway shoreline stratigraphic intertonguing of coastal sandstone deposits and marine shales developed in response to higher order depositional cycles where episodic transgressions interrupt regressions a simple model based on walther s law of facies has most often been used to interpret these deposits including channeled estuarine sandstones commonly found at the top of the sequence the regressive phase history is presumed to reflect progradation of a barrier island and its associated environments whereas transgressions are presumed to be mainly erosive i propose an alternative explanation for these deposits based on time stratigraphic architecture and component facies distributions of the point lookout sandstone in the northwestern san juan basin new mexico interpretations of outcrop measured sections and well log correlations suggest an individual parasequence is actually the product of a depositional couplet that includes a regressive phase and a transgressive phase strand plain progradation during the regressive phase produced upward coarsening shoreline deposits deposition during the transgressive phase occurred mainly in a zone landward of a reworked shoreline trend and comprises a lagoonal estuarine system specific examples of transgressive backbarrier deposits are described from outcrops of the point lookout sandstone these facies include an areally extensive fine grained variably stratified lagoonal deposit and an upward fining cross bedded sandstone deposited in highly migratory tidal channels the channeled estuary developed by infilling of the backbarrier lagoon the deposition of these backbarrier facies during episodic transgressions is significant for reinterpreting the typical vertical lithologic succession in cyclic regressive stratigraphic sequences the backbarrier deposits are separated from the strand plain deposits by a flooding surface and do not represent environments that translated seaward during shoreline progradation transgressive estuarine deposits appear to be an important potential reservoir facies in the point lookout section each estuarine sandstone is developed as a discrete reservoir unit at the landward limit of a parasequence these sandstones can be correlated into the subsurface and their distribution mapped parallel to depositional strike the distribution of channeled estuarine reservoirs can be predicted and effectively exploited based on the depositional couplet model

provenance signatures recorded in transgressive sandstones of the upper cretaceous iberian seaway abstract maximum mesozoic transgressions flooded many continental areas worldwide forming a wide and shallow seaway on the iberian microplate during the late cretaceous several siliciclastic and mixed siliciclastic carbonate units developed along the iberian massif cratonic area while at the same time epeiric carbonate platforms spanned iberia these siliciclastic deposits unconformably cover the variscan basement as well as the permian and triassic deposits this study focuses on sandstone provenance in central spain in a transgressive relatively quiet tectonic setting with a wide rock variety in the potential source areas results shown in this paper can be applied in analogue systems transgressive sandstones often form important hydrocarbon reservoirs due to their high primary porosity the cretaceous siliciclastic deposits are included in four formations ranging in age from the cenomanian to the early coniacian the deposits were initially of fluvial origin followed by a coastal tidal setting quantitative petrographic analysis of sandstones from these formations reveals compositional variations related to provenance and weathering degree the oldest formation utrillas fm was deposited on a paleorelief surface sandstone composition changes from arkosic sandstones in the depressed area petrofacies p1a to younger quartzarenites when sediments were deposited on top of the paleotopographic high petrofacies p1b quartz grains in both sub petrofacies are angular to subangular and the framework is poorly sorted intense weathering conditions are deduced for petrofacies p1b manifested by grain infiltration clay coatings and the absence of plagioclase grains and alteration features on k feldspars all these observations have been related to wetter conditions during p1b deposition main source areas of the utrillas fm were ordovician metasediments and orthogneisses permian volcanic rocks and triassic buntsandstein facies petrofacies 2 encompasses the three coastal tidal formations constituted mainly by subarkoses generally showing a subangular and poorly sorted framework the deduced source areas are mainly associated with variscan granitoids pre ordovician schists and paragneisses and ordovician metasediments glauconite and carbonate grains support intrabasinal inputs the low degree of sorting of this petrofacies related to a low energy sedimentary environment produced lower values of original porosity compared to transgressive sandstone hydrocarbon reservoirs also intrabasinal inputs promoted carbonate cementation and contribute to almost occlude the porosity

internal anatomy of a mixed siliciclastic carbonate platform the late cenomanian mid turonian at the southern margin of the spanish central system the late cenomanian mid turonian succession in central spain is composed of siliciclastic and carbonate rocks deposited in a variety of coastal and marine shelf environments alluvial plain estuarine lagoon shoreface offshore hemipelagic and carbonate ramp three depositional sequences third order are recognized the atienza patones and el molar sequences the patones sequence contains five fourth order parasequence sets while a single parasequence set is recognized in the atienza and el molar sequences systems tracts can be recognized both in the sequences and parasequence sets the lowstand systems tracts only recognized for atienza and patones sequences are related to erosion and sequence boundary formation transgressive systems tracts are related to marine transgression and shoreface retreat the highstand systems tracts are related to shoreface extension and progradation and to carbonate production and ramp progradation sequences are bounded by erosion or emergence surfaces whose locations are supported by mineralogical analyses and suggest source area reactivation probably due to a fall in relative sea level transgressive surfaces are subordinate erosion and or omission surfaces with a landward facies shift interpreted as parasequence set boundaries the co existence of siliciclastic and carbonate sediments and environments occurred as facies mixing or as distinct facies belts along the basin mixed facies of coastal areas are composed of detrital quartz and clays derived from the hinterland and dolomite probably derived from bioclastic material siliciclastic flux to coastal areas is highly variable the maximum flux postdates relative sea level falls carbonate production in these areas may be constant but the final content is a function of changing inputs in terrigenous sediments and carbonate content diminishes through a dilution effect carbonate ramps were detached from the coastal system and separated by a fringe of offshore fine grained muds and silts as distinct facies belts the growth of carbonate ramp deposits was related to the highstand systems tracts of the fourth order parasequence sets during the growth of these ramps some sediment starvation occurred basinwards progradation and retrogradation of the different belts occur simultaneously suggesting a sea level control on sedimentation in the study area the co existence of carbonate and siliciclastic facies belts depended on the superimposition of different orders of relative sea level cycles and occurred mainly when the second order third order and fourth order cycles showed highstand conditions

the effects of orography on midlatitude northern hemisphere dry climates abstract the role of mountains in maintaining extensive midlatitude arid regions in the northern hemisphere was investigated using simulations from the gfdl global climate model with and without orography in the integration with mountains dry climates were simulated over central asia and the interior of north america in good agreement with the observed climate in contrast moist climates were simulated in the same regions in the integration without mountains during all season but summer large amplitude stationary waves occur in response to the tibetan plateau and rocky mountains the midlatitude dry regions are located upstream of the troughs of these waves where general subsidence and relatively infrequent storm development occur and precipitation is thus inhibited in summer this mechanism contributes to the dryness of interior north america as a stationary wave trough remains east of the rockies but is not effective in eurasia due to seasonal changes in the atmospheric circulation the dryness

late cenozoic uplift in southern asia and the american west rationale for general circulation modeling experiments geologic evidence suggests significant increases in uplift rates and absolute elevation in several areas during the late cenozoic especially in the last 10 m y regions of major uplift include the tibetan plateau and himalayan mountains of southern asia and the sierra nevada colorado plateau basin and range rocky mountains and high plains of the american west uplift occurred at a scale large enough to affect regional and global climate in a number of ways several of which we evaluate by general circulation model experiments in accompanying papers

infiltrated clays in fluvial jurassic sandstones of reconcavo basin northeastern brazil abstract fluvial sandstones and conglomerates of the sergi formation a jurassic unit of reconcavo basin northeastern brazil contain significant amounts of interstitial detrital clays which are interpreted as the product of early mechanical infiltration developed in an arid semi arid environment within such an environment the lowered water table allowed muddy waters of episodic runoff to infiltrate through the coarse alluvium concentrating the clays in the upper phreatic zone near the sources of influent seepage petrographic textures considered to be typical of mechanically infiltrated mi clays are herein presented using examples from the sergi formation these textures include 1 ridges and bridges 2 geopetal fabrics 3 loose aggregates 4 anisopachous coatings of tangentially accreted lamellae cutans 5 massive aggregates and 6 shrinkage patterns developed during diagenesis in addition their detrital aspect as revealed by sem observations and the presence of impurities in the interior of the clay aggregates were also used as evidence for the interpreted origin of the clays in most hydrocarbon reservoirs in the sergi formation the clays described in this paper are among the main controls on porosity and permeability distribution commonly zones with maximum clay concentration are the main internal permeability barriers within the sergi formation reservoirs

glaucony from the cretaceous of the sierra de guadarrama central spain and its application in a sequence stratigraphic context detailed sedimentological and geochemical analyses of upper cretaceous glaucony bearing deposits from the middle portion of the castro de fuentiduena formation in central spain enable identification of a multiphase history of glaucony accumulation despite its relatively high maturity k2o 7 glaucony from the transgressive subtidal sandstones has anomalously low concentration in the host rock generally 10 suggesting remobilization from a different source the remarkable thickness of the glaucony bearing horizons concurrently with concentration of glaucony in laminae small size and high degree of roundness and sorting provide further evidence for an allochthonous origin of the green grains in contrast authigenic glaucony from the overlying offshore clays exhibits higher abundance up to 45 and lower maturity k2o 7 and is interpreted to have formed in situ allochthonous glaucony originally developed in more distal areas during a prolonged period of sediment starvation the green grains were then swept away from their place of origin and concentrated into tidal bars and channels within the upper transgressive systems tract of the third order depositional sequence maximum concentration of autochthonous glaucony is recorded at the transition from tidal influenced to offshore deposits this glaucony which is relatively less evolved due to lower time available for maturation is interpreted to reflect the turnaround from transgressive to highstand conditions marking the condensed section of the depositional sequence as postulated by previous sequence stratigraphic models this study documents that allochthonous glaucony can be widespread throughout the transgressive systems tract tst while the condensed section cs typically hosts autochthonous glaucony contrary to the existing literature however this study shows that glaucony from the tst may be even more mature than glaucony from the cs if enough time for maturation during transgression is allowed before the ultimate concentration of the green grains identification of spatial and temporal characteristics of glaucony thus is critical to a reliable sequence stratigraphic interpretation of the glaucony bearing deposits

mountain uplift and surface temperature changes mountain uplift significantly affects both sea surface temperature sst and land surface temperature this was studied using a coupled atmosphere mixed layer ocean model with and without mountains the global mean sst dropped 1 4 c with mountain uplift mainly due to increased lower tropospheric clouds in the subtropical eastern pacific increased clouds hinder solar radiation into the ocean and lower sst the increased frequency of stratus incidence is related to subtropical anticyclones intensified by a strong temperature contrast between the continent and ocean in mountainous regions land surface temperature drops due to the lapse rate effect when this effect is eliminated the continental interior does not become as cool with mountain uplift because clouds become fewer and the surface drier due to decreased moisture transport southern asia becomes cooler because monsoon induced precipitation wets the ground and increases clouds our result showed greater northern high latitude temperature changes than the previous study indicating the importance of cloud related feedback in paleoclimate modeling

diagenetic paths in the margin of a triassic basin nw zone of the iberian chain spain buntsandstein deposits generated in a slowly subsiding basin on the western margin of the iberian chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick conglomerates sandstones and shales diagenetic processes in sandstones can be grouped as eodiagenetic mesodiagenetic and telodiagenetic eodiagenesis can be associated with muschelkalk keuper and probably early jurassic times mesodiagenesis is probably related to jurassic times diagenetic chemical reactions suggest a maximum burial less than 1 5 km and low temperatures 120oc patterns of porosity reduction by compaction and cementation suggest four diagenetic stages 1 loss of primary porosity by early mechanical compaction 2 early cementation kfeldspar and dolomite 3 dissolution of cements and 4 framework collapse by re compaction these stages are manifested by the presence of two types of sandstone type i sandstones present high intergranular volume mean 30 type ii sandstones are characterized by high compactional porosity loss and exhibit low values of intergranular volume mean 16 9 type ii sandstones are associated with the dissolution of cement and later re compaction of type i sandstones an intermediate telodiagenetic phase is deduced and related to the sharp unconformity between lower cretaceous sediments and the underlying sediments this suggests that a mechanically unstable framework collapsed during the cretaceous generating type ii sandstones the analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins

forcing of late cenozoic northern hemisphere climate by plateau uplift in southern asia and the american west geologic evidence indicates that net vertical uplift occurred on a large kilometer scale and at accelerating rates during the middle and late cenozoic in plateaus of southern asia and the american west based on this evidence general circulation model sensitivity tests were run to isolate the unique effects of plateau uplift on climate the experiments simulated significant climatic changes in many places some far from the uplifted regions the basic direction of most of these simulated responses to progressive uplift is borne out by changes found in the geologic record winter cooling of north america northern europe northern asia and the arctic ocean summer drying of the north american west coast the eurasian interior and the mediterranean winter drying of the north american northern plains and the interior of asia and changes over the north atlantic ocean conducive to increased formation of deep water the modeled changes result from increased orographic diversion of westerly winds from cyclonic and anticyclonic surface flow induced by summer heating and winter cooling of the uplifted plateaus and from the intensification of vertical circulation cells in the atmosphere caused by exchanges of mass between the summer heated and winter cooled plateaus and the mid latitude oceans disagreements between the geologic record and the model simulations in alaska and the southern rockies and plains may be related mainly to the lack of narrow mountain barriers in the model orography taken together the observed regional trends comprise much of the pattern of late cenozoic climatic deterioration in the northern hemisphere that culminated in the plio pleistocene ice ages the success of the uplift sensitivity experiment in simulating the correct pattern and sign of most of the observed regional climatic trends points to uplift as an important forcing function of late cenozoic climatic change in the northern hemisphere at time scales longer than orbital variations however the modest amplitude of the uplift induced cooling simulated at high latitudes indicates a probable need for additional climatic forcing

sensitivity of eurasian climate to surface uplift of the tibetan plateau experiments with climate models are used to illustrate how earth s climate could be expected to change if surface uplift occurred the experiments contrast two climate simulations one with all continents at sea level and one with present day mountains and plateaus the simulations in the eurasia sector show that surface uplift increased elevation produces marked increases in the intensity of summer and winter monsoons of asia with development of wetter climates to the south and east of the tibetan plateau and drier climates to the north and west of the plateau there is a general cooling in northern polar latitudes comparison of simulations from two different models shows that the magnitude of the simulated changes depends upon how the models calculate the land surface hydrology and the ocean temperature the simulated changes produced by surface uplift agree in a general way with many geologic indicators of late cenozoic climate change the results suggest that surface uplift of mountains and platea

enso modulation by mountain uplift how climate changes will modify the behavior of el nino southern oscillation enso is one of the important questions in future climate projections an investigation under different climate forcing gives us a good insight on the mechanism of enso variability and its changes in this paper sensitivity on enso by progressive mountain uplift is investigated with an atmosphere ocean coupled general circulation model we used eight different mountain heights 0 no mountain 20 40 60 80 100 control run 120 and 140 land sea distribution is the same for all experiments and all mountains in the world are uniformly varied systematic changes in precipitation and circulation fields as well as sst are obtained with progressive mountain uplift in the summertime the precipitation area moved inland of the asian continent with mountain uplift while the pacific subtropical anticyclone and associated trade winds became stronger the western pacific warm pool and enso also systematically changed when the mountain height is low a warm pool is located over the central pacific due to weak trade winds in the pacific the model enso is strongest its frequency longest and is most periodic in the no mountain run the model enso becomes weaker shorter and less periodic when the mountain height increases strengthening the mean state trade winds and narrowing meridional extent of equatorial wind and ocean response by mountain uplift would be responsible for enso modulation

the madrid basin and the central system a tectonostratigraphic analysis from 2d seismic lines abstract data from deep boreholes seismic surveys and surface geology are used to reconstruct the sedimentary infilling of the cenozoic madrid basin eight main depositional sequences and seismic units are recognised from the paleogene the latter four of these sedimentary sequences were deposited in a continental environment under the influence of tectonic activity in the central system the toledo mountains the iberian chain and the sierra de altomira the sedimentary infill shows an overall coarsening upward trend from upper cretaceous formations to syn tectonic conglomerate deposits followed by a fining upward sequence and moderate reactivation of some faults during the late miocene pliocene the syn tectonic sediments are oligocene early miocene in age the foredeep is oriented northeast southwest and shows a sediment thickness of up to 3800 m in areas close to the central system several types of tectonic structures are recognised including imbricate thrust systems thrust triangle zones fault propagation folds back thrust systems and pop up structures the frontal thrusts were subjected to significant erosion and late miocene sediments onlap the anticlines of the onshore foreland nw se trending positive flower structures have been recognised in the eastern part of the basin the total northwest southeast shortening across the contact between the madrid basin and the central system is approximately 5 km of which 2 3 km occurred across the southern border thrust the simultaneous basement uplift of the central system and the tectonic escape of the sierra de altomira have been interpreted as a consequence of constrictive deformation within the pyrenean foreland of the iberian microplate

provenance environmental and paleogeographic controls on sandstone composition in an incised valley system the eocene la meseta formation seymour island antarctica abstract the eocene la meseta formation is the youngest exposed unit of the back arc james ross basin antarctic peninsula cropping out in seymour marambio island the formation comprises 720 m of clastic sedimentary rocks of deltaic estuarine and shallow marine origin it was subdivided into six unconformity based units valle de las focas acantilados campamento cucullaea i cucullaea ii and submeseta allomembers grouped into three main facies associations facies association i represents valley confined deposition in a progradational aggradational tide dominated and wave influenced delta front delta plain environment facies association ii includes tidal channels mixed tidal flats tidal inlets and deltas washover and beach environments facies association iii represents nonconfined tide and storm influenced nearshore environments la meseta formation sandstones are quartzofeldspathic with some hybrid arenites glauconite and carbonate bioclasts rich sandstone detrital modes are subdivided into two distinctive petrofacies the low quartz petrofacies petrofacies i q 12 interpreted to retain the original provenance signal and the high quartz petrofacies petrofacies ii q 55 and l 1 4 is clearly dominated by volcanic derived clasts it developed at times of high sea level and or during later stages of the valley fill when an energy fence at the shoreline prevented delivery of sediment from the antarctic peninsula thus enhancing the relative participation of local volcanic sources

the role of air sea interactions in regulating the thermal effect of the tibetan iranian plateau on the asian summer monsoon the thermal effect of the tibetan iranian plateau tip on the asian summer monsoon and the role of air sea interactions over the indian ocean in regulating the effects of the tip are explored the results demonstrate that the direct thermal effect of the tip produces a lower troposphere cyclonic circulation in the area surrounding the tip and increases the continental precipitation over south and east asia it also decreases the precipitation over the tropical indian ocean and increases the sea surface temperature sst of the tropical indian ocean with a large gradient zone located along 10 n but decreases sst of the western coast of indonesia in the lower troposphere the air sea interaction induced by the tip thermal forcing produces an anticyclonic circulation surrounding the tip and a stronger westerly flow to the south of the anticyclone a circulation dipole thus forms to the south of the tip together with this horizontal dipole a meridional circulation dipole is generated to the south of the tip which is characterized by strong air ascent from 10 to 15 n where a strong westerly flow occurs and the descent of air over the southern slope of the tip and south hemisphere these results demonstrate that the indirect effect of the air sea interaction over the indian ocean induced by the tip thermal forcing is to counteract its direct effect on the asian summer monsoon the uncertainty of this indirect effect is also discussed

sensitivity of east asian monsoon climate to the uplift of the tibetan plateau abstract using the cola center for ocean land atmosphere studies general circulation model a series of numerical experiments were conducted to examine the impact of uplift of the tibetan plateau on the evolution of the monsoon climate in east asia an attempt was made to isolate the effect of the plateau uplift from the changes in other forcing mechanisms we examined the spatial and temporal variation patterns of a variety of climatic variables and indices including monsoon intensity sea level pressure surface and upper air winds temperature at different levels precipitation air humidity and soil moisture our results suggest that the evolution of the east asia monsoon may be more sensitive to the uplift of the tibetan plateau than that of the south asia monsoon moreover the effect of the plateau uplift on the east asia winter monsoon is more significant than that on the summer monsoon in the northern part of east asia north china the formation of the monsoon climate is marked mainly by the establishment of the northerly winds in winter or the winter monsoon system corresponding to the uplift of the plateau when the height reaches approximately 50 of its current elevation on the other hand the establishment of the monsoon climate in the southern part of east asia the yangtze river valley and the area south of it may be much earlier than that in the northern part

variscan syncollisional extension in the iberian massif structural metamorphic and geochronological evidence from the somosierra sector of the sierra de guadarrama central iberian zone spain abstract the rocks affected by the variscan orogeny in the sierra de guadarrama central iberian zone can be separated into two domains a high grade western domain and a medium to low grade eastern domain these domains are separated by the berzosa riaza shear zone a new integrated analysis of structural metamorphic and u pb monazite age data indicates that the berzosa riaza shear zone is a major d2 extensional structure associated with oblique crustal scale extensional shearing and important decompression low p high t metamorphism associated with the d2 event overprints earlier barrovian metamorphic assemblages formed during the variscan d1 compressional event the kilometre scale berzosa riaza shear zone exhibits a s c mylonitic front at its base and a crenulation front at its top with successive fabric development under different p t conditions indicating crustal thinning textural relationships and u pb dating of monazite indicate that the main d2 extensional event took place between 337 2 and 326 3 ma early mid carboniferous a late d2 extensional episode overprinted the major d2 ductile shear zone along narrow low grade oblique normal detachment zones kinematic indicators in both d2 and late d2 fabrics indicate a displacement of the upper structural levels to the southeast field relationships microstructures and qualitatively derived p t t d paths suggest that the early mid carboniferous syncollisional extension in the sierra de guadarrama was associated with the major extensional collapse of the variscan hinterland central iberian zone and was contemporaneous with the earliest thrusting in the foreland

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

midlatitude shelf seas in the cenomanian turonian greenhouse world temperature evolution and north atlantic circulation 1 an 8 million year record of subtropical and midlatitude shelf sea temperatures derived from oxygen isotopes of well preserved brachiopods from a variety of european sections demonstrates a long term cenomanian temperature rise 16 20 c midlatitudes that reached its maximum early in the late turonian 23 c midlatitudes superimposed on the long term trend shelf sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations in the mid cenomanian and the late turonian two minor shelf sea cooling events 2 3 c coincide with carbon cycle perturbations and times of high amplitude sea level falls although this evidence supports the hypothesis of potential glacioeustatic effects on cretaceous sea level the occurrence of minimum shelf sea temperatures within transgressive beds argues for regional changes in shelf sea circulation as the most plausible mechanism the major carbon cycle event in the latest cenomanian oceanic anoxic event 2 is accompanied by a substantial increase in shelf sea temperatures 4 5 c that occurred 150 kyr after the commencement of the 13c excursion and is related to the spread of oceanic conditions in western european shelf sea basins our oxygen isotope record and published 18o data of pristinely preserved foraminifera allow the consideration of north atlantic surface water properties in the cenomanian along a transect from the tropics to the midlatitudes on the basis of fossil derived 18o estimated w ranges and modeled salinities temperature salinity density ranges were estimated for tropical subtropical and midlatitude surface waters accordingly the cenomanian temperate shelf seas waters have potentially the highest surface water density and could have contributed to north atlantic intermediate to deep waters in the preopening stage of the equatorial atlantic gateway

effects of mountain uplift on east asian summer climate investigated by a coupled atmosphere ocean gcm abstract to study the effects of progressive mountain uplift on east asian summer climate a series of coupled general circulation model cgcm experiments were performed eight different mountain heights were used 0 no mountain 20 40 60 80 100 control run 120 and 140 the land sea distribution is the same for all experiments and mountain heights are varied uniformly over the entire globe systematic changes in precipitation pattern and circulation fields as well as sea surface temperature sst appeared with progressive mountain uplift in summertime precipitation area moves inland on the asian continent with mountain uplift while the pacific subtropical anticyclone and associated trade winds become stronger the mountain uplift resulted in an sst increase over the western tropical pacific and the maritime continent and an sst decrease over the western indian ocean and the central subtropical pacific there is a drastic change in the east asian circulations with the threshold value

petrology of fluvial sands from the amazonian foreland basin peru and bolivia modal sand compositions in nine rivers draining the proximal part of the amazonian retroarc foreland basin in peru and bolivia provide support for the recycled orogen provenance model of dickinson and suczek average compositions of 52 sand samples from the rio madre de dios and its tributaries are qfl 74 5 21 qmflt 60 5 35 qplvmlsm 44 10 46 lmlvls 69 18 13 and qmpk 91 4 5 these compositions accurately reflect the predominance of sedimentary and metasedimentary rocks in the cordillera oriental of the andean orogen the ultimate source terrane for the sands of the modern foreland basin rivers of the madre de dios basin can be classified in one of three ways 1 rivers that head in the subandean fold thrust belt 2 rivers that are actively incising a subtle intraforeland uplift overlain by quaternary and upper tertiary foreland basin fill and 3 trunk rivers that collect both type 1 and type 2 rivers the rivers that drain the fold thrust belt carry sands that are slightly more lithic than those carried by rivers that drain the intraforeland uplift the intraforeland derived sands are relatively enriched in volcanic rock fragments lmlvls 70 22 8 whereas sands derived from the fold thrust belt are relatively enriched in sedimentary rock fragments lmlvls 66 9 24 the overriding control on sand composition is the relative area of bedrock type exposed in the fold thrust belt sands reworked from tertiary and quaternary foreland basin fill are relatively enriched in quartz possibly owing to intense weathering of sediments in the soil profile the preservation of predictable and systematic mixing patterns in sand compositions from different rivers suggests that sandstone petrologic data may be augmented by paleocurrent isopach and textural data to facilitate detailed reconstruction of drainage patterns in ancient nonmarine foreland basins