compressive and tensile failure of inclined well bores and determination of in situ stress and rock strength in this paper we investigate the occurrence of compressive and tensile failures of arbitrarily inclined well bores under a wide variety of stress conditions the principal assumptions in this analysis are that the rock is isotropic and that it deforms elastically to the point of failure as has been shown by previous investigators for a given stress state and well bore orientation it is straightforward to predict the orientation of the failures around the well bore as well as whether failure is likely to occur depending on such parameters as rock strength and borehole fluid pressure however as the stress state is almost never known in situ we demonstrate how observations of compressive and tensile wall failures in inclined holes can be used to constrain in situ stress orientations and magnitudes if there are independent data on the magnitude of the least principal stress from either leak off or microfrac tests and on the formation pore pressure we further demonstrate how once the stress state is determined it is possible to assess both an upper bound on the effective in situ rock strength and the degree to which increasing the borehole fluid pressure or mud weight can reduce the likelihood of borehole failure through application of this methodology to an inclined well bore in an area of complex faulting in the gulf of mexico we illustrate how it is possible to utilize observations of borehole failures to determine the magnitude and orientation of the stress tensor in areas such as offshore sedimentary basins where drilling inclined well bores is quite common

the stress regime in a rotliegend reservoir of the northeast german basin in situ stresses have significant impact either positive or negative on the short and long term behaviour of fractured reservoirs the knowledge of the stress conditions are therefore important for planning and utilization of man made geothermal reservoirs the geothermal field gros schonebeck 40 km north of berlin germany belongs to the key sites in the northeastern german basin we present a stress state determination for this lower permian rotliegend reservoir by an integrated approach of 3d structural modelling 3d fault mapping stress ratio definition based on frictional constraints and slip tendency analysis the results indicate stress ratios of the minimum horizontal stress s hmin being equal or increasing 0 55 times the amount of the vertical stress s v s hmin 0 55s v and of the maximum horizontal stress s hmax 0 78 1 00s v in stress regimes from normal to strike slip faulting thus acting stresses in the 4 100 m deep reservoir are s v 100 mpa s hmin 55 mpa and s hmax 78 100 mpa values from hydraulic fracturing support these results various fault sets of the reservoir are characterized in terms of their potential to conduct geothermal fluids based on their slip and dilatation tendency this combined approach can be adopted to any other geothermal site investigation

geochelone in illinois and the illinoian sangamonian vegetation of the type region abstract an investigation of illinoian and sangamonian age deposits in the type region for both pleistocene stages in central illinois has yielded a palynological record spanning the illinoian sangamonian boundary associated with an interglacial fauna containing geochelone crassiscutata the pollen indicates a shift from high picea and pinus to deciduous trees followed by grass and herbaceous taxa and finally a return of deciduous trees this sequence appears to correlate with marine isotopic stages 6 through 5d faunal remains are abundant throughout but megafauna are present only in the interglacial section where geochelone occurs the presence of geochelone suggests above freezing temperatures in central ilinois throughout the year during at least the portion of the sangamonian represented

a model of late quaternary landscape development in the delaware valley new jersey and pennsylvania abstract in the delaware valley of new jersey and eastern pennsylvania the late quaternary history of colluviation fluvial adjustment and soil formation is based on the ages of pre wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid latitude climate changes indicated by marine oxygen isotope records the area is divided into four terranes characterized by sandstone gneiss slate and carbonate rocks since the last pre wisconsinan glaciation 130 ka inferred to be late illinoian each terrane responded differently to chemical and mechanical weathering during the sangamon interglacial stage 130 75 ka in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep highly weathered soil and saprolite and dissolution of carbonate rocks cold climatic conditions during the wisconsinan on the other hand induced erosion of the landscape at rates faster than soil development upland erosion during the wisconsinan removed pre wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium grezes litees and alluvial fans on footslopes fluvial gravel and overlying colluvium in the delaware valley both buried by late wisconsinan outwash are inferred to represent episodes of early and middle wisconsinan 75 25 ka upland erosion and river aggradiation followed by river degradation and colluvium deposition early middle wisconsinan colluvium is more voluminous than later colluvium despite colder possibly permafrost conditions during the late wisconsinan 25 10 ka extensive colluviation during the early and middle wisconsinan resulted from a longer 50 kyr generally cold interval of erosion with a greater availability of easily eroded pre wisconsinan surficial materials on uplands than during the late wisconsinan after recession of late wisconsinan ice from its terminal position soil formation and landscape stability were delayed until the holocene by a lingering cold climate slope erosion colluvium and alluvial fan deposition and eolian sedimentation late quaternary erosion in the delaware valley was dominated by glacial and periglacial processes during glacial stages during the warm interglacial stages soils developed on a more stable landscape these souls were easily colluviated by periglacial erosion during periods of intermittent cold climate

late cenozoic relief evolution under evolving climate a review abstract the present review paper is an attempt to summarize quantitative evidence of late cenozoic changes in topographic relief different meanings of the word relief as it is commonly used and detail the metrics used to quantify it we then specify methodological tools used to quantify relief change primarily low temperature thermochronometry and terrestrial cosmogenic nuclides and analyze published evidence for different regions our review first shows that relief changes and rates of changes are more important at mid than high or low latitudes and appear to be insensitive to mean precipitation rates it also show that relief change is positive relief increases in most of the reported cases 80 we subsequently define two functional relationships between relief and erosion depending on the chosen definition of relief and propose a conceptual model of landscape memory we conclude following others that erosion rates depend non linearly on relief evolution itself being a function of the spatial distribution and rates of erosion the relief increases documented in this review may be to erosion rate increases during the same timescales lastly we discuss the importance of glacial and periglacial processes on late cenozoic relief and erosion rate changes and stress the importance of frost shattering and glacial erosion at mid and high latitudes

geomorphically driven late cenozoic rock uplift in the sierra nevada california geologists have long accepted that the sierra nevada california experienced significant late cenozoic tectonically induced uplift a flexural isostatic model presented here shows however that a large fraction of the primary evidence for uplift could be generated by the lithospheric response to coupled erosion of the sierra nevada and deposition in the adjacent central valley and therefore requires less tectonic forcing than previously believed the sum of range wide erosion and the resultant isostatic rock uplift would have lowered sierra mean elevation by 200 to 1000 meters since 10 million years ago and could also have increased summit elevations during the current period of relief production

biostratigraphy of the last glacial period in europe the european early weichselian early wurmian is characterized by two long and relatively warm interstadials brorup and odderade which can be traced and correlated with certainty across large parts of europe the amersfoort interstadial described earlier from the netherlands has been included in the brorup and represents the older part of it both great interstadials were forested in north west central and southern europe in the north conifer forests prevailed giving way towards the south to deciduous forests the climatic gradient was distinctly steeper mainly due to southward displacement of the gulf stream the two great interstadials are synchronous with the isotopic stages 5a and 5c in the deep sea cores subsequent to eemian brorup and odderade and from within the context of a continuous series two additional and clearly delimited interstadials have been recorded in a new standard profile from oerel nw germany these are now described as the oerel and glinde interstadials they were not forested and belong to the early pleni weichselian the lower one oerel can probably be correlated with the 3rd weichselian wurmian interstadial in southern central europe ognon ii durnten samerberg 3 while the upper one glinde has so far no known counterpart for the younger pleni glacial it is assumed that there was a long phase during which it was not too cold the formation of humic layers during this phase took place at different times partly due to local edaphic factors so that the relevant 14c dates show a wide scatter the hengelo and denekamp interstadials represent only slight ameliorations which facilitated the formation of shrub tundra and can be recorded in certain regions only

late quaternary temporal and event classifications great lakes region north america abstract several temporal and event classifications are used for the quaternary glacial and interglacial record in the great lakes region of north america although based on contrasting principles the classifications as practiced are similar to one another in most respects and they differ little from the classification proposed by chamberlin a century ago all are based on stratigraphic units having time transgressive boundaries thus the associated time spans and events are diachronous where application of geochronologic classification based on isochronous boundaries is not practical or useful we advocate the use of diachronic principles to establish local and regional temporal and event classifications diachronic and event classifications based on such principles are proposed herein for the great lakes region well established names including wisconsin sangamon and illinois are used at the episode or glaciation interglaciation rank without significant redefinition the hudson episode interglaciation is introduced for postglacial time the current interglacial interval the wisconsin episode is divided into the ontario elgin and michigan subepisodes in the eastern and northern parts of the great lakes region and into the athens and michigan subepisodes in the southern and western parts of the great lakes region

modern sangamon and yarmouth soil development in loess of unglaciated southwestern illinois abstract the thebes section in unglaciated southwestern illinois contains a well preserved 500 kyr loess paleosol sequence with four loesses and three interglacial soils various magnetic mineralogical and elemental properties were analyzed and compared over the thickness of soil sola these proxies for soil development intensity have the following trend yarmouth geosol sangamon geosol modern soil quartz plagioclase zr sr and tio 2 na 2 o ratios were most sensitive to weathering frequency dependent magnetic susceptibility and anhysteretic remanent magnetization greatest in a horizons also correspond well with soil development intensity neoformed mixed layered kaolinite expandables suggestive of a warm humid climate were detected in the sangamon and yarmouth soil sola clay illuviation in soils was among the least sensitive indicators of soil development differences in properties among interglacial soils are interpreted to primarily reflect soil development duration with climatic effects being secondary assuming logarithmic decreases in weathering rates the observed weathering in the sangamon geosol is consistent with 50 kyr of interglacial weathering oxygen isotope stage 5 compared to 10 kyr for the modern soil oxygen isotope stage 1 we propose that the yarmouth geosol in the central midwest formed over 180 kyr of interglacial weathering including oxygen isotope stages 7 9 and 11

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

erosional unloading hillslope geometry and the height of the cascade range washington state usa peaks in the cascade range in northern washington state are on average 800 m higher than in southern washington the influences of differential valley excavation and variations in hillslope length and average slope on these altitudinal trends were tested using a 3 dimensional model for isostatic rock uplift and calculations of hillslope length and slope respectively the magnitude of isostatic peak uplift calculated by the model is highly dependent on the flexural rigidity d and the related effective elastic thickness te of the crust of this region crustal rigidity was constrained using published estimates and by estimating the depth of the seismogenic zone in the area d 1 1023 nm and te 24 km with these constraints isostatic compensation due to differential erosion added 700 m and 300 m or 25 overall of height to peaks in the northern and southern cascades respectively deeper valley incision in the northern cascades accounts for 300 m of the 800 m difference in peak altitudes between north and south similarly variation in valley spacing and slope account for 350 m of the difference in mean altitude between northern and southern regions hence at least several hundred m difference in altitude between the northern and southern regions of the cascades in washington must be due to tectonic geologic or geophysical factors rather than surficial and geomorphic effects like isostatic response to valley incision and hillslope geometry copyright 2009 john wiley sons ltd

isostatic and dynamic support of high topography on a north atlantic passive margin abstract substantial controversy surrounds the origin of high topography along passive continental margins here we focus on the well documented elevated passive margin in southwestern scandinavia and quantify the relative contributions of crustal isostasy and dynamic topography in controlling the present topography we find that majority of the topography is compensated by the crustal structure suggesting a topographic age that is in accord with the 400 myr old caledonian orogenesis in addition we propose that dynamic uplift of 300 m has rejuvenated existing topography locally in the coastal region over the last 10 myr such uplift combined with a general sea level fall can help explain a variety of observations that have traditionally been interpreted in favor of a peneplain uplift model we conclude that high topography along the scandinavian margin cannot represent remnants of a peneplain uplifted within the last 20 myr the topography must have been high since the caledonian orogeny

climate change in southern illinois usa based on the age and δ13c of organic matter in cave sediments abstract matrix supported diamicton and uniform to laminated silty fine grained sediment deposited from about 42 500 to 27 600 cal yr b p under slackwater conditions nearly filled two caves in southwestern illinois at some point most of the sediment was flushed from the caves and from about 22 700 to 4000 cal yr b p floods deposited a drape of sandy and silty sediment on remnant slackwater successions cobbly alluvium and bedrock especially from 7700 to 4000 cal yr b p clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly petersburg silt a smectite and illite rich proglacial lacustrine unit present in the overlying illinois episode glacial succession today remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and in at least two locations cover a cobble mantled strath terrace 1 3 to 1 5 m above active stream channels slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes in addition to sinkhole formation and enter caves however the finer organics some of them comminuted during transport into the caves become part of the cave alluvium this finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods twenty four 14c ages on humified organic matter provide chronologic control the 13c values of the organic matter reflect the proportion of c4 type to c3 type vegetation growing in and around swallets and sinkholes at the time of redeposition drought tolerant c4 type vegetation was more prevalent relative to c3 type vegetation from 42 500 to 31 200 cal yr b p compared to conditions from 28 800 cal yr b p to the present the 13c values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols

modeling the flow of glaciers in steep terrains the integrated second order shallow ice approximation isosia 1 the rugged topography of mountain ranges represents a special challenge to computational ice sheet models simulating past or present glaciations in mountainous regions the topography steers glaciers through relatively narrow and steep valleys and as a consequence hereof the flow rate of alpine style glaciers varies significantly at length scales comparable to that of the topography localized flow rate undulations generate longitudinal and transverse stress gradients within the ice which in turn are of known importance to the flow itself whether by internal deformation of the ice or by basal sliding and to the interaction with topography through glacial erosion standard models capable of simulating mountain range scale glaciations build on the so called shallow ice approximation which among other parameters neglects the longitudinal and transverse stress gradients and therefore fails to capture the full effects of the rugged topography and related feedbacks between erosion by glacial sliding and the extent and style of glaciation here we present and test a new depth integrated model framework which on the one hand takes into account the higher order effects related to steep and rugged bed topography while it still on the other hand provides the computational efficiency needed for three dimensional simulations of glaciation and landscape evolution in response to for example long term climate variations the model framework integrated second order shallow ice approximation isosia is based on depth integration of the second order shallow ice approximation although depth integration is not guaranteed to maintain so called second order accuracy the results of computational benchmark experiments show that isosia in spite of its efficient depth integrated structure performs well in situations with steep and rapidly undulating bed topography

comparison of soils in midwestern united states and western europe with the interglacial record abstract paleosols that formed primarily before the last glaciation cannot be adequately explained by a model of holocene like interglacial periods of about 10 000 yr in length which has been inferred from the marine 18 o 16 o record geological and palynological evidence from terrestrial midlatitude sites suggests that temperate conditions conducive to soil formation existed for periods greatly in excess of 10 000 yr during the middle and late pleistocene available data on soils formed during this interval from western europe and midwestern united states are best explained by relatively long interglaciations or the development of composite soils over a number of temperate periods climatic contrasts between the interglaciations appear to have been overemphasized widespread assumptions regarding greater warmth in interglaciations prior to the present one are generally unproven in the absence of precise dating progress in relating paleosols to fragmentary local records of quaternary climatic changes will be achieved by detailed analytical techniques such as soil micromorphology

palaeohydrology vegetation and climate since the late illinois episode 130 ka in south central illinois abstract our interpretation of pollen and ostracode successions from four basins in south central illinois provides a new synthesis of palaeovegetation palaeohydrology and palaeoclimate for the period from the late illinois episode about 130 000 years ago to near the end of the wisconsin episode about 25 000 years ago correlations of pollen biozones between raymond pittsburg and bald knob basins are the basis for identifying the late illinois glacial sangamon interglacial wisconsin glacial and hudson interglacial episodes glacial episodes were identified primarily by the presence of picea pollen and the ostracode limnocythere friabilis whereas interglacial episodes were identified by quercus pollen and by the ostracodes candona caudata and heterocypris punctata within interglacial and glacial episodes pollen and ostracode assemblages varied with changes in moisture balance local palaeohydrology was assessed primarily on the basis of environmental tolerance indices of ostracodes and the stable isotope c o stratigraphy of ostracodal calcite regional moisture balance was assessed from multivariate analyses of the pollen successions three climatic regimes occurred during the sangamon episode 1 one regime was characterised by precipitation exceeding evaporation that promoted basin overflow this climate was inferred from the high percentages generally 80 of deciduous forest pollen peaks in the abundance of liquidambar and fagus pollen indicate that winters may have been slightly warmer and effective moisture slightly greater than at present 2 the second climatic regime was continental similar to the present climate of illinois in which precipitation is equal to or just less than evaporation this climate is inferred from abundant ambrosia pollen 40 to 60 and abundant nektic swimming ostracode valves which suggest a shallow lake these conditions probably developed in association with a heat low over the interior of north america during marine oxygen isotope stages 5e and 5c associated with the transition between the first two climates are fossils of the subtropical ostracode heterocypris punctata and the giant tortoise geochelone crassiscutata that suggest short periods in winter when polar low pressure systems did not extend into illinois as they do today 3 the third climatic regime occurred during the transition from the sangamon interglacial episode to the wisconsin glacial episode a severely continental climate is indicated by the heat tolerant ostracode pelocypris tuberculatum variable 18o values of ostracode valves and high environmental tolerance index values for the ostracode assemblages the weedy chenopodiaceae and amaranthaceae families grew on exposed mudflats the tree pollen associated with this type of climate included low percentages of picea and liquidambar an assemblage that has no modern analogue we suggest that this transitional climatic regime was associated with the large scale changes in the climate system during marine oxygen isotope stage 4

the influence of alpine glaciation on the relief of tectonically active mountain belts a surface processes model incorporating large scale fluvial processes local hill slope processes and glacial erosion is used to investigate the effect of glaciation on the relief of a fast growing narrow orogen the results of several simulations show that glaciers concentrate erosion near peaks fluvial erosion is reduced downstream of glaciers glaciers with frozen bases can lead to an increase in relief and the net affect of glaciation in the absence of widespread basal freezing is to reduce relief

direct land sea correlations in the last interglacial complex isotopic and pollen analyses of an eastern atlantic core permit the first direct correlation of substages 5e and 5c of the marine climatostratigraphical system with the eemian and st germain i respectively of the classical grande pile pollen sequence north east france the vegetational sequences during the warm intervals of the last interglacial complex 125 000 75 000 yr bp indicate that climatic deterioration occurred late on the mid european continent after the initiation of glaciation over continental masses in high latitudes

paleoenvironmental interpretation of multiple soil loess sequence at milford reservoir northeastern kansas abstract a loess soil section near the republican river in northeastern kansas includes three superposed soils paleosols in at least three superposed loess units including peoria loess pl the gilman canyon formation gcf and loveland loess ll the gcf coincides with a composite soil with a 1 3 m thick buried organic rich a horizon that yields ams radiocarbon ages from 30 3 to 22 4 ka or 35 7 to 26 9 ka when calibrated that overlies a 1 6 m oxidized b horizon complex the b subhorizons stratigraphically and morphologically resemble the reddish pedocomplex described elsewhere in kansas and illinois that dates between about 69 and 35 ka the upper ll yields a tl age of about 136 and 130 30 ka thus pl the gcf and ll were probably deposited mainly during the late wisconsinan middle wisconsinan and illinoian oxygen isotope stages ois 2 3 and 6 or about 12 to 24 24 to 60 and 130 to 188 ka respectively soils 1 2 and 3 then formed mainly during ois stages 1 3 and 5 respectively or about 12 to 12 60 to 60 and 73 to 130 ka in comparison with other dated stratigraphic sections in the great plains soils paleosols have relatively simple cumulic horizon sequences as is typical at sites distal from principle loess source regions nonetheless they record a complex pedosedimentary history that reflects climatically driven variations in rates of sedimentation and pedogenesis soil 1 is an udic argiustoll with 21 cm a mollic 69 cm bt argillic 60 cm bk horizons that formed under modern type grassland and climate soil 3 the sangamon paleosol includes a 3 m thick highly rubified and clay rich argillic horizon that based on its morphological properties probably formed under a relatively warm moist equable climate and deciduous type forest soil 2 coincides with the gcf and as such is a pedolithostratigraphic unit that includes a 1 3 m mollic horizon and to 1 6 m oxidized 3btb and 3bcb horizons whereas the oxidized b horizons apparently represent relatively warm moist climatic conditions between about 65 to 35 ka the upper cumulic mollic a horizons of the gcf probably formed under progressively cooling climate and grassland between about 35 7 and 26 9 calibrated radiocarbon ka estimated mean accumulation rates mars of loess range from 0 12 m k yr for the gcf to about 0 5 m k yr for pl

the geochemistry of loess asian and north american deposits compared abstract loess is widely distributed over asia and north america and constitutes one of the most important surficial deposits that serve as terrestrial records of the quaternary the oldest pleistocene loess in china is likely 2 6 ma thus spanning much or all of the pleistocene in north america most loess is no older than the penultimate glacial period with the exception of alaska where the record may go back to 3 0 ma on both continents loess deposits date primarily to glacial periods and interglacial or interstadial periods are represented by paleosols both glacial and non glacial sources of silts that comprise the bulk of loess deposits are found on both continents although loess has been considered to be representative of the average upper continental crust there are regionally distinctive compositions of loess in both asia and north america loess deposits in asia from yakutia tajikistan and china have compositionally distinct major element compositions due to varying abundances of silicate minerals carbonate minerals and clay minerals in north america loess in the mississippi river valley the great plains and alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments trace element geochemistry sc th zr and the rare earth elements also shows regional diversity of loess bodies in both asia and north america on both continents most loess bodies show significant contributions from later cycle altered sedimentary rocks as opposed to direct derivation from igneous rocks further some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average upper crustal felsic rocks intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials ratios of soluble to insoluble elements show depletions in paleosols due to chemical weathering losses of calcite dolomite plagioclase mica apatite and smectite in asia and north america the last interglacial paleosol is more weathered than equivalent modern soils which could be due either to a climate that was warmer and more humid a longer period of pedogenesis or both in asia early pleistocene loess and paleosols are both more weathered than those from the middle and late pleistocene forming prior to a mid pleistocene aridification of asia from uplift of the tibetan plateau understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation past temperature and moisture regimes and even tectonic processes

post 10 ma uplift and exhumation of the northern coast mountains british columbia apatite u th he ages reveal three distinct periods in the exhumation history of the northern coast mountains 54 n a well developed helium partial retention zone indicates little or no exhumation between ca 30 and 10 ma beginning at 10 ma and extending to at least 4 ma the range underwent steady but slow exhumation of 0 22 mm yr after which the exhumation rate increased by at least 70 an 85 km long he age traverse across the orogen at sea level shows that vertical offsets on post 10 ma faults are minor furthermore the sea level he ages 14 2 8 ma inversely correlate with local mean elevation along the traverse these data suggest that the coast mountains first appeared as a significant topographic feature only within the past few million years this history is not consistent with suggestions that uplift of the range resulted from formation of the queen charlotte basin in early middle miocene time we speculate that intense erosion by alpine and continental glaciation after 2 5 ma triggered isostatic uplift and creation of the modern topography of the coast mountains

long continental pollen sequence from washington state u s a correlation of upper levels with marine pollen oxygen isotope stratigraphy through substage 5e abstract fossil pollen from a 7 70 m core and a pit excavated 2 20 m deep in a mire at humptulips located on glacial drift of the olympic peninsula in western washington state presents a continuous record of vegetation since the middle pleistocene chronostratigraphic relations established from sedimentation rates based on finite and infinite radiocarbon dates in the upper 2 m of the deposit cover the last glacial cycle illinoian glaciation and apparently older millennia the pollen stratigraphy contained in 16 pollen assemblage zones shows a sequence of vegetation types including tundra park tundra woodland and closed confierous forest comparison with pollen and oxygen isotope stratigraphy of marine core y72 11 1 from the pacific ocean off oregon establishes direct continental marine correlation of upper levels at humptulips through substage 5e

valley incision and the uplift of mountain peaks simple end member models describe the effect of isostatically compensated valley incision on the elevation of mountain peaks these models allow calculation of the maximum portion of mountain peak elevations attributable to the development of observed relief and predict general downstream patterns of ridgetop uplift in response to erosion by fluvial processes analyses of topographic profiles across major drainages of the central sierra nevada and the tibetan plateau indicate that isostatically compensated valley incision could account for at most 5 10 of the present elevation of mountain peaks in contrast analyses of topographic profiles across the himalaya show that as much as 20 30 of the present elevation of himalayan peaks could be explained by isostatically compensated valley incision the degree to which valley incision is compensated locally however depends on the flexural rigidity of the lithosphere the size of the range and its tectonic boundary conditions these results show that while a tectonic control is required for late cenozoic surface uplift of the sierra nevada a significant portion of the elevation of himalayan peaks may reflect late cenozoic valley incision on the margin of the tibetan plateau

multiple paleosols in pre wisconsinan drift northwestern montana and southwestern alberta summary varying numbers of strongly developed paleosols occur on and between multiple pre wisconsinan diamict mostly till units which cap interfluves east of waterton glacier parks southwestern alberta and northwestern montana investigation of stratigraphy morphology and genesis of the paleosols permits subdivision of quaternary deposits and estimation of the length and climatic characteristics of pre wisconsinan interglacials stratigraphic relations indicate at least five soils in five tills on saint mary ridge and mokowan butte up to three soils in four tills on two medicine ridge two soils in two tills on milk river ridge and one soil in one till on cloudy ridge ages of diamicts probably range from late pliocene to kansan or early illinoian because the paleosol till sequences on mokowan butte and saint mary ridges are not correlative more than five pre late illinoian depositional and soil forming episodes are probably represented in the region paleosols generally include 1 to 5 m thick reddish leached clay rich argillic horizons overlying leached cambic or calcic horizons or indurated calcretes 4 to 15 m thick morphological chemical and mineralogical properties of paleosols resemble those of paleudalfs and paleustalfs suggesting the soils formed over long periods 0 02 to 2 68 ma under climates which were significantly warmer by at least 6 degrees c and moister than today s

ice sheet erosion and the stripping of tertiary regolith from baffin island eastern canadian arctic abstract the erosion of glaciated regions and concomitant changes in ice sheet dynamics through the pleistocene are poorly documented the baffin island landscape which has been shaped by the foxe sector of the laurentide ice sheet lis contains a variety of glacial and proximal glaciomarine sedimentary archives spanning the pleistocene we examine these records to better understand when tertiary regolith was stripped from beneath the foxe sector of the lis till on the interior plateaux of the island in areas with scoured bedrock have low chemical index of alteration cia values low meteoric 10 be 10 be met concentrations and clay mineralogy consistent with erosion from an unweathered bedrock source however in some areas in between fiord onset zones more weathered till is present containing considerably higher cia values high 10 be met concentrations and secondary clay mineral weathering products implying that the till has persisted on the landscape and weathered during successive glaciations using these weathering signatures we analyze the coastal glaciogenic deposits of the clyde foreland formation cff at two sites for evidence of tertiary regolith removal from the interior of baffin island by lis erosion provenance indicators within the cff demonstrate that pleistocene lis ice flow lines across baffin island have remained generally constant the oldest cff glaciogenic unit likely representing one of the first if not the first lis advances across baffin island had high 10 be met concentrations at the time of deposition consistent with extensive regolith erosion evidence of notably weathered sediment is absent in all younger units suggesting that tertiary regolith was likely largely stripped from the interior of the island by 1 6 0 2 ma

the relationship between closure pressures from fluid injection tests and the minimum principal stress in strong rocks abstract closure pressures measured during injection tests such as mini fracs are normally considered an accurate measure of the minimum in situ principal stress magnitude this paper presents stress strength and image log data from the australian cooper basin which suggests that in reservoirs with high in situ stress high tensile strength and weak geological fabrics interpreted closure pressures may be significantly greater than the minimum principal stress closure pressures interpreted from mini frac injection tests in the cooper basin suggest the minimum principal stress varies from 12 4 27 2 mpa km 0 55 1 2 psi ft to better understand the reasons for this variation in closure pressure image logs and mini frac data from 13 treatment zones and core from seven of these treatment zones were analysed the analysis revealed that treatment zones with high measured closure pressures 18 1 mpa km 0 8 psi ft high treating pressures 31 6 mpa km 1 4 psi ft and high measured hydraulic fracture complexity existed in reservoirs with high tensile rock strength 7 mpa 1015 psi and geological fabrics planes of weakness including natural fractures conversely treatment zones with lower measured closure stress 19 mpa km 0 84 psi ft and low hydraulic fracture complexity occurred in reservoirs with lower tensile strength and or no geological fabrics we suggest that closure pressures in rocks with high tensile strength and weak geological fabrics may not be representative of the minimum principal stress magnitude in the cooper basin where they are associated with hydraulic fracture complexity rather they reflect the normal stress incident on pre existing weaknesses that are exploited by hydraulic fluid during the mini frac injection

geochemistry of speleothem records from southern illinois development of 234u 238u as a proxy for paleoprecipitation natural waters universally show fractionation of uranium series u series parent daughter pairs with the disequilibrium between 234 u and 238 u 234 u 238 u commonly used as a tracer of groundwater flow because speleothems provide a temporal record of geochemical variations in groundwater precipitating calcite 234 u 238 u variations in speleothems provide a unique method of investigating water rock interaction processes over millennium time scales we present high precision thermal ionization mass spectrometric tims u series analyses of speleothems and drip waters from fogelpole cave in southern illinois data from all speleothems from the cave show an inverse correlation between 234 u 238 u and u concentration following the pattern observed in groundwaters globally within a 65 cm long stalagmite concordant 234 u 238 u 230 th and 235 u 231 pa ages for 5 samples indicate accurate chronology from 78 5 ka to 30 ka notably 234 u 238 u o which differs from most speleothems by having 234 u 238 u ob1 positively correlates with speleothem growth rate we generalize this to the observation that speleothems globally show 234 u 238 u o deviating farther from secular equilibrium at lower growth rates and approaching secular equilibrium at higher grow rates based on the fogelpole observations we suggest that groundwater 234 u 238 u is controlled by the u oxidation state the u concentration of the water and the fluid velocity a transport model whereby u series nuclides react and exchange with mineral surfaces can reproduce the observed trend between growth rate and 234 u 238 u o based on this result we suggest that 234 u 238 u o in speleothems may record changes in hydrologic flux with time and thus could provide a useful proxy for long term records of

absence of glaciation in illinois during marine isotope stages 3 through 5 a10be inventory and14c ages of material from a core from northernmost illinois support previous interpretations that this area was ice free from ca 155 000 to 25 000 yr ago during much of this period from about 155 000 to 55 000 yr ago 10be accumulated in the argillic horizon of the sangamon geosol wisconsinan loess containing inherited10be was deposited above the sangamon geosol from ca 55 000 to 25 000 yr ago and was subsequently buried by late wisconsinan till deposited by the lake michigan lobe of the laurentide ice sheet the sangamonian interglacial stage has been correlated narrowly to marine oxygen isotope substage 5e our data indicate instead that the sangamon geosol developed during late stage 6 all of stages 5 and 4 and early stage 3

glacial erosion promotes high mountains on thin crust abstract every mountain range on earth is unique in its tectonic evolution but quaternary climate cooling resulted in alpine landscapes with globally similar landforms such as horn shaped peaks cirques and overdeepened valleys on a global scale the impact of glacial and periglacial processes on the geometry of mountain ranges and the relative efficiency of glacial and fluvial erosion are still discussed to address these issues we analyse a novel worldwide dataset of more than 16 000 mountain peaks we relate peak height and steepness to mean elevation and crustal thickness we show that the geometry of mountain ranges systematically varies with latitude and thus with climate for peaks of similar height the steepness increases towards high latitudes while mean elevation and thickness of the supporting crust decrease modelling flexural isostasy based on the topographic load of mountain ranges demonstrates that the crustal thickness required to support peaks of similar height dramatically declines with intensity of glacial erosion in concert with latitudinal trends in peak steepness mean elevation and crustal thickness this shows that quaternary climate cooling reduces the topographic load by transforming the geometry of mountain landscapes from fluvial to glacial conditions we conclude that the prevalence of glacial erosion in cold climate reduces the topographic load of mountain ranges and enables the growth of high mountain peaks even on moderately over thickened crust

influence of terrestrial vegetation on sediment forming processes in kettle lakes of west central minnesota the composition magnetic characteristics and pollen content of sediments from two small kettle lakes near the prairie forest border in west central minnesota were used to infer changes in terrestrial vegetation shoreline erosion eolian inputs carbonate deposition and aquatic productivity several important changes in sediment stratigraphy coincide closely with changes in the terrestrial pollen assemblage accumulation rates of organic inorganic and carbonate sediment fractions as well as the concentration of magnetic particulates increased abruptly as prairie replaced pine forest and decreased gradually throughout the subsequent transitions to oak scrub and later mixed woodland results suggest that by its mediation of wind exposure local vegetation may affect 1 influx of eolian particulates 2 erosion of shorelines 3 water circulation and 4 carbonate equilibria in addition low rates of accumulation of organic matter and increased humidicity during periods of conifer vegetation suggest that humic matter leached from forest soils may influence lake water chemistry and reduce productivity changes in lake level caused by differential rates of evapotranspiration of the various vegetation types conifer forest deciduous hardwood forest brush scrub and prairie could not be detected sediment forming processes can therefore be altered by changes in local terrestrial vegetation through several mechanisms that are independent of changes in lake level

evolution of the molasse basin germany switzerland abstract in the molasse basin 500 1000 m thick mesozoic sediments overlie the variscan basement and locally permo carboniferous grabens containing a largely unknown thickness of clastic sediments the vindelician basement high extended southwestward from the bohemian massif and separated the southern part of the german basin from the tethys shelf triassic early and middle jurassic sediments progressively transgressed over this high which became fully inundated during the late jurassic following a temporary regression sedimentation resumed in the early cretaceous and after another hiatus in the late aptian to campanian during the latest cretaceous to earliest tertiary the area of southern germany became uplifted resulting in a progressive northwestward truncation of cretaceous strata and the late jurassic carbonates at the same time the bohemian massif became upthrusted along northwest striking wrench faults similar faults controlled the upthrusting of the landshut neuoetting high over which some 1 000 m of mesozoic sediments were eroded these wrench and thrust tectonics are part of an extensive compressional deformation in central europe that is supposed to be caused by the latest cretaceous earliest tertiary collision of the adriatic african and european plates during the alpine orogeny the area subsided again during the late eocene and developed into the molasse basin proper in which oligocene to miocene elastics reach a thickness of some 5 000 m near the alpine thrust front subduction and flexuring of the foreland caused numerous essentially basin parallel synthetic and antithetic normal faults the latter form the primary traps for oil and gas accumulations in the molasse basin

present day stress orientation in the molasse basin abstract the present day state of stress in western europe is considered to be controlled by forces acting at the plate boundaries it is assumed that the alpine orogen only influence the regional pattern of present day stress in western europe within the alps themselves we examine the present day maximum horizontal stress orientation in the molasse basin in the alpine foreland in order to investigate the possible influence of the alps on the far field stress pattern of western europe four arm caliper and image logs were analysed in 137 wells in which a total of 1348 borehole breakouts and 59 drilling induced fractures were observed in 98 wells in the german molasse basin the borehole breakouts and drilling induced fractures reveal that stress orientations are highly consistent within the molasse basin and that the present day maximum horizontal stress orientation rotates from n s in southeast germany 002 n 19 to approximately nnw sse in southwest germany and the swiss molasse basin 150 n 24 the present day maximum horizontal stress orientation in the molasse basin is broadly perpendicular to the strike of the alpine front indicating that the stress pattern is probably controlled by gravitational potential energy of alpine topography rather than by plate boundary forces the present day maximum horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the german molasse basin in particular that hydraulically induced fractures are likely to propagate n s and that wells deviated to the north or south may have reduced wellbore instability problems

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

the late cenozoic uplift climate change paradox the geologic evidence for worldwide uplift of mountain ranges in the neogene is ambiguous estimates of paleoelevation vary according to whether they are based on the characteristics of fossil floras on the masses and grain sizes of eroded sediments or on calculations of increased thickness of the lithosphere as a result of faulting detrital erosion rates can be increased both by increased relief in the drainage basin and by a change to more seasonal rainfall patterns the geologic record provides no clear answer to the question whether uplift caused the climatic deterioration of the neogene or whether the changing climate affected the erosion system in such a way as to create an illusion of uplift we suggest that the spread of c4 plants in the late miocene may have altered both the erosion and climate systems these changes are responsible for the apparent contradictions between data supporting uplift and those supporting high elevations in the past

pulses of carbon dioxide emissions from intracrustal faults following climatic warming carbon capture and geological storage represents a potential means of managing atmospheric carbon dioxide levels an analysis of a 135 000 palaeorecord shows that pulses of carbon dioxide leakage from a natural reservoir in utah are associated with episodes of glacial unloading

the role of the 2008 mw 7 9 wenchuan earthquake in topographic evolution seismically induced landslides and the associated isostatic response

a 130 000 year long pollen record from pittsburg basin illinois abstract pittsburg basin in south central illinois contains a sediment record extending from the present back to the end of the late illinoian glaciation when central illinois was covered with picea pinus forest during the last interglaciation a temperate deciduous forest more diverse than holocene quercus carya forest replaced the illinoian late glacial boreal forest prairie pollen types and the charcoal pollen ratio indicating fire frequency temporarily increased then forest with high juniperus percentages became dominant once more as the charcoal pollen ratio dropped after the last interglaciation the charcoal pollen ratio increased again and prairie and wetland surrounded pittsburg basin through the entire wisconsinan glacial age the area was still prairie in late wisconsinan time but with some picea and pinus during the holocene the region has been a mixture of prairie and quercus carya forest during the last interglaciation pittsburg basin was surrounded by vegetation different from that surrounding it during the present interglaciation rather than indicating substantial differences in climate between analogous phases of different glacial interglacial cycles this variation may be due to changes in fire frequency which could be caused by small changes in climate human activity or differences in soil

ecosystem development following deglaciation a new sedimentary record from devils lake wisconsin usa abstract processes and rates of ecosystem development can be reconstructed using lacustrine sedimentary sequences but this approach often requires records that contain the start of primary succession most lakes in the upper midwestern u s were formed by glaciers at the end of the last ice age approximately 11 700 cal yr bp devils lake wisconsin is a rare example of a lake from this region whose sediments extend into the pleistocene and may include the last glacial maximum sediment magnetic geochemical pollen and charcoal records were generated from a 10 m core whose basal sediments may be 28 000 years old together with a previously published pollen record these proxies combine to reveal a history of long term climatic vegetative and geologic change during the late pleistocene to holocene we identify six sedimentary units that indicate a series of consecutive events rather than a predictable trajectory of ecosystem development at the site productivity in the lake was low during the late pleistocene and increased during the holocene as reflected by the sediment lithology which shows a sudden shift from glacial vivianite rich and organic poor clastic dominated sediments to holocene diatomaceous sapropels several important processes initiated around 17 000 cal yr bp including the onset of organic matter accumulation and fire in the terrestrial ecosystem however the post glacial landscape was not devoid of vegetation because pollen assemblages indicate that terrestrial vegetation likely a spruce tundra survived near the site a switch to a hardwood forest period during the holocene also led to a change in the fire regime with increased frequency of burning aquatic ecosystem productivity lagged terrestrial ecosystem productivity throughout the record nutrient cycling as recorded by sedimentary 15n was variable but not directional and appeared to be correlated with climate conditions early in the record and terrestrial ecosystem processes later in the record throughout the holocene magnetic mineral concentration decreased as productivity increased and the source of magnetic material shifted from almost exclusively lithogenic to approximately 50 derived from soil or biogenic sources magnetic grain size ambrosia pollen percentages and charcoal concentration increased and 15n decreased in the most recent part of the record due to anthropogenic influence in the region including agricultural activities

modelling of fractured carbonate reservoirs outline of a novel technique via a case study from the molasse basin southern bavaria germany fluid flow in low permeable carbonate rocks depends on the density of fractures their interconnectivity and on the formation of fault damage zones the present day stress field influences the aperture hence the transmissivity of fractures whereas paleostress fields are responsible for the formation of faults and fractures in low permeable reservoir rocks fault zones belong to the major targets before drilling an estimate for reservoir productivity of wells drilled into the damage zone of faults is therefore required due to limitations in available data a characterization of such reservoirs usually relies on the use of numerical techniques the requirements of these mathematical models encompass a full integration of the actual fault geometry comprising the dimension of the fault damage zone and of the fault core and the individual population with properties of fault zones in the hanging and foot wall and the host rock the paper presents both the technical approach to develop such a model and the property definition of heterogeneous fault zones and host rock with respect to the current stress field the case study describes a deep geothermal reservoir in the western central molasse basin in southern bavaria germany results from numerical simulations indicate that the well productivity can be enhanced along compressional fault zones if the interconnectivity of fractures is lateral caused by crossing synthetic and antithetic fractures the model allows a deeper understanding of production tests and reservoir properties of faulted rocks

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

estimate of three dimensional flexural isostatic response to unloading rock uplift due to late cenozoic glacial erosion in the western united states alpine glacial erosion may strongly influence mountain building through erosionally driven rock uplift and relief production in this paper i use a three dimensional model for the flexural isostatic response of the lithosphere to estimate the potential for late cenozoic erosionally driven rock uplift in the western united states specifically i present a map of the ratio of erosionally driven rock uplift to glacial erosion for this region this ratio depends on the magnitude of the flexural bending stresses that act to limit differential uplift the map is created by constraining the extent of pliocene quaternary alpine glacial erosion in the western united states and solving the three dimensional flexure equation for the resulting lithospheric deflection the map indicates that the magnitude of erosionally driven uplift depends sensitively on the size of the glaciated range and the presence of nearby glaciated ranges as a result regional scale patterns must be considered in order to correctly estimate local amounts of erosionally driven rock uplift the ranges in the western united states with the greatest ratios of uplift to erosion are the san juan mountains and the yellowstone plateau absaroka range because these are extensively glaciated and have glaciated ranges nearby in contrast the wind river range and sierra nevada have ratios of uplift to erosion that are only half as large these results identify which ranges likely underwent the greatest erosionally driven uplift and relief production and provide a widely applicable technique for modeling the flexural isostatic response to loading and unloading in three dimensions

differences between the last two glacial maxima and implications for ice sheet δ18o and sea level reconstructions studies of past glacial cycles yield critical information about climate and sea level ice volume variability including the sensitivity of climate to radiative change and impacts of crustal rebound on sea level reconstructions for past interglacials here we identify significant differences between the last and penultimate glacial maxima lgm and pgm in terms of global volume and distribution of land ice despite similar temperatures and radiative forcing our analysis challenges conventional views of relationships between global ice volume sea level seawater oxygen isotope values and deep sea temperature and supports the potential presence of large floating arctic ice shelves during the pgm the existence of different glacial modes calls for focussed research on the complex processes behind ice age development we present a glacioisostatic assessment to demonstrate how a different pgm ice sheet configuration might affect sea level estimates for the last interglacial results suggest that this may alter existing last interglacial sea level estimates which often use an lgm like ice configuration by several metres likely upward

the influence of intrabasinal faults on the development of a linked thrust system the mesozoic and cenozoic rocks exposed in the arve valley region of the external french alps are used to assess the role of early intrabasinal faults on later thrust fault evolution the early intrabasinal faults produced at some time from latest upper cretaceous to tertiary strike parallel or subparallel to later neo alpine thrusts where early faults dip away from the thrusts they are generally cut through and occasionally are overturned during this process in one example extreme overturning has allowed partial reactivation early faults dipping in the same direction as thrusts may a be reactivated b initiate ramping of the thrust ahead of the preexisting fault c be cut through by the thrust d cause pinning of the thrust at the footwall of the fault and folding against the fault as displacement continues buttressing from this work it is evident that intrabasinal faults exerted a major influence on the distribution of mechanical heterogeneities these heterogeneities include variations of stratigraphic thickness and type across faults fault related unconformities and the presence of the fault itself during the period of contraction such features strongly controlled the development of the stress field produced ahead of an advancing thrust and hence influenced the position of thrust fault propagation within the stratigraphy

slip tendency analysis fault reactivation potential and induced seismicity in a deep geothermal reservoir abstract a slip tendency analysis is used to assess the reactivation potential of shear and dilational fractures in a deep geothermal reservoir in the northeast german basin based on the notion that slip on faults is controlled by the ratio of shear to normal stress acting on the plane of weakness in the in situ stress field the reservoir rocks composed of lower permian sandstones and volcanics were stimulated by hydraulic fracturing a surprisingly low microseismic activity was recorded with moment magnitudes mw ranging from 1 0 to 1 8 the slip tendency analysis suggests a critically stressed reservoir exists in the sandstones whereas the volcanic rocks are less stressed rock failure first occurs with an additional pore pressure of 20 mpa presumed failure planes form a conjugate set and strike nw and ne slip failure is more likely than tensional failure in the volcanic rocks because high normal stresses prevent tensional failure these results from slip tendency analysis are supported by the spatial distribution of recorded microseismicity source characteristics indicate slip rather than extension along presumed ne striking failure planes this suggests that slip tendency analysis is an appropriate method that can be used to understand reservoir behavior under modified stress conditions

paleoclimatic significance of late cenozoic paleosols east of waterton glacier parks alberta and montana abstract stratigraphy and inferred genesis of pre wisconsinan paleosols east of waterton glacier parks provide information on the timing and magnitude of late tertiary quaternary climate changes highly weathered relict and buried paleosols in superposed late tertiary quaternary tills and diamicts on upper miocene pliocene flaxville bench remnants record at least five and up to ten soil forming episodes inferred interglacials separating at least five pre wisconsinan glacial and possibly pre glacial depositional events similar paleosols occur at the surface in outwash alluvium on flaxville and number 2 early pleistocene and number 3 middle and late pleistocene benches the paleosols are clearly not in equilibrium with the present environment rather they resemble fersiallitic soils paleudalfs paleustalfs paleudolls which occur in more southerly latitudes in warmer wetter and more equable climates thus properties of the paleosols suggest they formed under mean annual temperatures mats and precipitation map at least 6 8 c and 40 cm higher than present respectively paleobiological and pedological evidence from eurasia and north america marine records sea level reconstructions and climatological models suggest similar and even greater climatic fluctuations occurred in other middle and high latitude continental regions

a finite difference technique to incorporate spatial variations in rigidity and planar faults into 3 d models for lithospheric flexure summary we present a finite difference formulation for 3 d elastic flexure of the lithosphere which is solved by a direct matrix method to incorporate the effect of spatial variations in rigidity additional terms for the bi harmonic 3 d flexure equation have been derived from a variational displacement formulation as used in finite element methods additionally planar faults are treated as discontinuities these are implemented by an additional degree of freedom for fault heave and a coupled continuum equation for zero differential tilting across the fault the 3 d finite difference results have been tested for line loads point loads and disc loads by analytical solutions and for spatial variation in effective elastic thickness eet by 2 d finite difference solutions fault related flexure patterns are compared to the 2 d analytical broken plate model developed by vening meinesz 1950 we subsequently apply the 3 d fault model to investigate fault controlled 3 d basement geometries in lake tanganyika east africa we show that our model is capable of predicting 3 d basement geometries characteristically observed in rifted basins the modelling results indicate that fault controlled upper crustal flexure patterns are associated with low values for eet a comparison with regional scale model studies showing a superposition of high eet flexure effects supports a multilayered rheological control on continental rifting

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

evolution of topography of post devonian scandinavia effects and rates of erosion abstract the mechanisms and timing of mountain growth in scandinavia remain enigmatic given that the region has not been involved in active orogenesis since the devonian and in any large scale tectonic activities after the ne atlantic breakup during the early cenozoic in this study we combine analysis of the vertical motions of the region caused by dominantly glacial erosion during the quaternary with apatite fission track aft analysis of rocks from the area using numerical models we first quantify how fluvial and glacial erosion carved out the fjords and valleys to a depth of 2 km below the paleosurfaces this erosional episode represents a major local weight loss and results in up to a 0 8 km uplift of rocks and up to a 0 5 km rise of local topography these estimates only marginally depend on the effective elastic thickness of the lithosphere and thus are robust we show then that no correlation exists between sample altitude and published aft data but that a correlation does exist between aft age and the depth below our constructed pre glacial summit surface this correlation demonstrates the robustness of the numerical erosional model quantifies average erosion rates during carboniferous cretaceous at

temporal evolution of fault systems in the upper jurassic of the central german molasse basin case study unterhaching the structural evolution of faults in foreland basins is linked to a complex basin history ranging from extension to contraction and inversion tectonics faults in the upper jurassic of the german molasse basin a cenozoic alpine foreland basin play a significant role for geothermal exploration and are therefore imaged interpreted and studied by 3d seismic reflection data beyond this applied aspect the analysis of these seismic data help to better understand the temporal evolution of faults and respective stress fields in 2009 a 27 km2 3d seismic reflection survey was conducted around the unterhaching gt 2 well south of munich the main focus of this study is an in depth analysis of a prominent v shaped fault block structure located at the center of the 3d seismic survey two methods were used to study the periodic fault activity and its relative age of the detected faults 1 horizon flattening and 2 analysis of incremental fault throws slip and dilation tendency analyses were conducted afterwards to determine the stresses resolved on the faults in the current stress field two possible kinematic models explain the structural evolution one model assumes a left lateral strike slip fault in a transpressional regime resulting in a positive flower structure the other model incorporates crossing conjugate normal faults within a transtensional regime the interpreted successive fault formation prefers the latter model the episodic fault activity may enhance fault zone permeability hence reservoir productivity implying that the analysis of periodically active faults represents an important part in successfully targeting geothermal wells

cenozoic uplift of europe 1 following the diachronous cretaceous neogene onset of seafloor spreading in the northern atlantic and arctic oceans the european passive margin and continental europe underwent a generalized uplift this long wavelength cenozoic uplift has been attributed either to mantle plumes and or to the far field compression in the alps we suggest an alternative mechanism or concause where the asthenosphere depleted at the mid atlantic ridge was shifted relatively eastward beneath the continent because of the net rotation of the lithosphere the partial melting at the oceanic ridge leaves the asthenosphere lighter when migrating beneath the european continental lithosphere the substitution of the older denser mantle with the depleted lighter asthenosphere should have generated an isostatic rebound and associated uplift of about 300 600 m dynamic topography exerted by the mantle flowing eastward could have enhanced the uplift process

a revised crustal stress orientation database for canada abstract the canadian database on contemporary crustal stress has not been revised systematically in the past two decades here we present the results of our new compilation that contains 514 new data records for the orientation data of maximum compressive horizontal stress and 188 data records that were re assessed in total the canadian stress database has now 1667 data records which is an increase of about 45 from these data a new canadian stress map as well as one for the province of alberta is presented to analyse the stress pattern we use the quasi median on the circle as a smoothing algorithm that generates a smoothed stress map of the maximum compressive horizontal stress orientation on a regular grid the newly introduced quasi interquartile range on the circle estimates the spreading of the data and is used as a measure for the wave length of the stress pattern the result of the hybrid wavelength analysis confirms that long spatial wavelength stress patterns 1000 km exist in large areas in canada the observed stress pattern is transmitted through the intra plate regions the results reveal that shorter spatial wave length variation of the maximum compressive horizontal stress orientation of less than 200 km prevails particularly in south eastern and western canada regional stress sources such as density contrasts active fault systems crustal structures etc might have a significant impact in these regions in contrast to these variations the observed stress pattern in the alberta basin is very homogeneous and mainly controlled by plate boundary forces and body forces the influence of curvature of the rocky mountains salient in southern alberta is minimal the present day horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the alberta basin

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

mid wisconsinan environments on the eastern great plains abstract few sites on the eastern great plains contain paleobotanical records for the mid wisconsin we report on four sites two stream cutbanks and two quarry exposures ranging in age from 50 to 23 4 ka the oldest site at 50 ka contains a suite of macrofossils from prairie and disturbed ground habitats with no representation of trees indicating an open prairie by 38 ka the assemblages include aquatic wetland mudflat and prairie elements with rare specimens of populus betula cf papyrifera salix and at the most northerly site picea this assemblage suggests a prairie parkland with interspersed marshes cooler temperatures and increased moisture populus and salix continued to be represented from 36 to 29 ka but the only other taxon was carex a hiatus may be present at some time during this interval after 29 ka picea became dominant on the uplands and it was joined by sedges in local wetlands at sites near riverine loess sources loess accumulation began to fill in the wetlands and organic deposition ceased some time after 29 ka

foreland normal fault control on northwest himalayan thrust front development in the trans indus ranges along the western part of the northwest himalayan thrust front unconformities changes in paleocurrent directions and locally derived conglomerates in synorogenic foreland basin deposits provide evidence for major local deformation at 3 5 ma the tectonic history of the trans indus ranges has previously been described in terms of a single episode of major thrusting at 1 ma thus our work implies that there were two distinct phases of deformation in conjunction with published evidence in the salt range to the east for two phases of deformation 6 to 5 ma and 2 5 ma to present this study demonstrates that these two phases of deformation are regionally significant and probably correlative along the entire present day nw himalayan thrust front reconstruction of possible source areas for the locally derived conglomerates shows that the earlier deformation is probably related to normal faulting these results suggest that the tectonic evolution of the area along the present day thrust front is characterized by 1 latest miocene to early pliocene formation of north dipping normal fault zones total throw 600 m within the foreland basin related to syn orogenic flexure of the indian plate and 2 late pliocene to early pleistocene initiation of south directed thrusting along the present day thrust front related to outward growth of the nw himalayan thrust wedge the location of the present day thrust front appears to be controlled by north dipping normal faults and monoclines that formed during the earlier deformation and subsequently localized structural ramps during later thrusting

frictional properties and slip stability of active faults within carbonate evaporite sequences the role of dolomite and anhydrite seismological observations show that many destructive earthquakes nucleate within or propagate through thick sequences of carbonates and evaporites for example along the apennines range italy carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes 5 0 mw 6 3 however little is known about the frictional properties of these rocks which are dominated by dolomite and anhydrite and differ from typical quartzofeldspathic rocks here we report on laboratory experiments designed to illuminate friction constitutive properties and associated microstructures of anhydrite and dolomite fault rocks we performed frictional sliding experiments on powdered samples for a range of normal stresses n from 10 to 150 mpa and sliding velocities from 1 to 300 m s experiments employed the double direct shear configuration and were conducted both dry at room temperature and water saturated at 75 c under true triaxial stresses at 25 c sliding friction is 0 65 for all samples and conditions studied at 75 c samples develop cohesive strength and sliding friction ranges from 0 4 to 0 5 for n from 10 to 35 mpa velocity step tests were used to assess rate state frictional behavior at 25 c the slip behavior is velocity strengthening neutral for all samples microstructural observations indicate localized deformation on r1 riedel and incipient y shear planes with marked grain size reduction at 75 c and larger strain we find that rate state friction behavior correlates with velocity dependent layer dilation and compaction and this is associated with the development of through going y shear planes we conclude that elevated temperature strain and the presence of pore fluids enhance shear localization into continuous y shear planes which could promote frictional instability at seismogenic depth within dolomite anhydrite sequences

pleistocene relief production in laramide mountain ranges western united states gently sloped summits and ridges collectively referred to as summit flats are abundant in many laramide ranges in the western united states the erosion rate of summit flats is 10 m m y on the basis of the concentrations of cosmogenic radionuclides because erosion rates in valleys between summit flats are an order of magnitude faster relief within these ranges is currently increasing by about 100 m m y if summit flat erosion is slower than rock uplift driven by the isostatic response to valley erosion then this relief production could result in increased summit elevations the mean depth of material eroded from a smooth surface fit to existing summit flats varies from 280 to 340 m in four laramide ranges based on geographic information system gis analyses of digital elevation models this erosion would result in a maximum of 250 300 m of rock uplift assuming airy isostasy however because the laramide ranges examined here are narrow relative to the flexural wavelength of the lithosphere erosionally driven rock uplift is limited to 50 100 m over the past several million years summit erosion would approximately offset this rock uplift therefore we conclude that summit elevations have remained essentially constant even though several hundred meters of relief has been produced on the basis of valley and summit erosion rates and the average depth of erosion we estimate that relief production in laramide ranges began at ca 3 ma we hypothesize that this relief production was climatically driven and was associated with the onset or enhancement of alpine glaciation in these ranges

a multi parameter rock magnetic record of the last glacial interglacial paleoclimate from south central illinois usa pittsburg basin a small kettle lake in south central illinois was formed after the retreat of the illinoian ice sheet 130 ka b p and the sedimentary record includes the last interglacial glacial cycle curie temperature measurements xrd analyses and thermal demagnetization of a low temperature j indicate that the magnetic fraction is characterized by rs oxidized magnetite and magnetic iron sulfides the grain size of the magnetic fraction was estimated from armrj ratios rs frequency dependent susceptibility and hysteresis parameters these measurements show that glacial sediments contain coarse grained presumably detrital material while interglacial samples have an additional fine grained magnetic component which cannot be explained by a single catchment or climatic process early interglacial samples show magnetic properties characteristic of authigenic biogenically produced magnetite while late interglacial samples are probably influenced by pedogenesis around the basin q 1997 elsevier science b v

a study of clay pore water and sporopollens for characterizing paleoenvironments in the hebei plain northern china abstract we developed a clay pore water cpw isotopic method for tracing paleoenvironments characterized by sporopollens the thick clayey layers have the advantage of preserving pore water regardless of whether the water is inherent in the clayey layers or not therefore the clayey layers are a suitable target from which paleoenvironmental information can be extracted sediment sporopollens as well as cpw deuterium and oxygen isotopes were investigated in drilling cores obtained from a 130 m borehole at a field site in hengshui in the north china plain our interpretation of 18 o in cpw was consistent with sporopollens climate indices indicating that cpw was an effective proxy for obtaining paleoenvironmental information sporopollens species were abundant in the cores but the quantity of each species was low furthermore mean annual temperature and precipitation curves were established using a pollen climatic response surface model the results indicated two warm humid periods 5 2 0 m 22 6 11 m and one cold dry period 8 8 6 4 m in the holocene as well as two warm humid periods 90 6 83 m 110 6 108 2 m and three cold dry periods approximately 40 m 66 4 56 8 m approximately 100 m in the late pleistocene data derived from the sporopollens and cpw cumulatively elucidate the environmental change in northern china

growth of normal faults in multilayer sequences a 3d seismic case study from the egersund basin norwegian north sea abstract we investigate the structural style and evolution of a salt influenced extensional fault array in the egersund basin norwegian north sea through analysis of 3d reflection seismic and well data analysis of fault geometry morphology throw distribution and syn kinematic strata reveal an intricate but systematic style of displacement and growth suggesting an evolution of 1 initial syn sedimentary fault growth contemporaneous with salt mobilization initiated during the late triassic 2 cessation of fault activity and burial of the stagnant fault tips and 3 subsequent nucleation of new faults in the cover above contemporaneous salt re mobilization initiated during the late cretaceous with downward propagation and linkage with faults stage 3 was apparently largely controlled by salt mobilization in response to basin inversion as reactivated faults are located where the underlying salt is thick while the non reactivated faults are found where salt is depleted based on the 3d throw analyses we conclude that a combination of basement faulting and salt re mobilization is the driving mechanisms behind fault activation and reactivation even though the sub and supra salt faults are mainly geometrically decoupled through the salt a kinematic coupling must have existed as sub salt faults still affected nucleation and localization of the cover faults

patterns of holocene environmental change in the midwestern united states abstract four pollen sequences along a transect from north central iowa to southeast wisconsin reveal the distribution of prairie and forest during the holocene and test the use of pollen isopolls in locating the holocene prairie forest border prairie was dominant in central iowa and climate was drier than present from about 8000 to 3000 yr b p during the driest part of this period in central iowa 6500 5500 yr b p mesic forest prevailed in eastern iowa and wisconsin suggesting conditions wetter than at present prairie replaced the mesic forest about 5400 yr b p in eastern iowa but did not extend much farther east mesic forests were replaced in southern wisconsin and northern illinois about 5400 yr b p by xeric oak forests this change from mesic to xeric conditions at 5400 yr b p was widespread and suggests that the intrusion of drier pacific air was blocked by maritime tropical air from the gulf of mexico until the late holocene in this area

spatial and temporal variations of glacial erosion in the rhone valley swiss alps insights from numerical modeling the present day topography of the european alps shows evidence of intense glacial reshaping however significant questions regarding alpine landscape evolution during glaciations still persist in this study we focus on the rhone valley swiss alps and use a numerical model to estimate patterns and magnitudes of glacial erosion comparing modeling results on a reconstructed pre glacial topography and the present day landforms we find that the landscape response to glaciation is more complex than a simple buzzsaw mechanism by which glacial erosion sets the height of mountain ranges or increase of relief due to localized valley incision instead glacial erosion propagates headward as the landforms evolve from a fluvial to a glacial state leading to an initial increase of local relief followed by subsequent erosion at high elevations it has also been proposed that the mid pleistocene climatic transition of glacial interglacial oscillations from periods of 40 kyr with symmetric shapes to periods of 100 kyr with asymmetric shapes promoted glacial erosion within the alps although this change of climate periodicity may have contributed to enhance glacial erosion our results suggest that other factors such as an increase in rock uplift and or progressive climate cooling are required to explain enhanced glacial carving at view the mathml source 1ma

post variscan to early alpine sedimentary basins in the tauern window eastern alps the crystalline basement of the tauern window is locally covered by palaeozoic to mesozoic sediments that experienced alpine tectonometamorphism the sedimentary cover has been subdivided into mappable lithological units the correlation of these units the use of some dated marker intervals and independent palinspastic restoration provide evidence that the depositional area was differentiated into basins and swells at the end of the variscan orogeny during the carboniferous and permian intermontane basins formed in basement rocks and mainly continental clastics accumulated in elongate troughs later probably during the triassic there was levelling of the previous relief and subsidence of the basins but continental sedimen tation still prevailed although interrupted by some marine transgressions thereafter probably during the jurassic the area was progressively flooded and the sedimentation became increasingly calcareous the upper jurassic carbonates document complete submergence in some areas the upper jurassic carbonates directly rest on crystalline basement indicating renewed tectonic stretching the sedimentary cover shows striking similarities with coeval deposits within the germanic basin and the study area is therefore considered to have been part of the southern european continental margin of the tethys the so called vindelician land

a normal faulting stress regime in the bavarian foreland molasse basin new evidence from detailed analysis of leak off and formation integrity tests in the greater munich area se germany abstract leak off and formation integrity test data from the central part of the bavarian foreland molasse basin have been investigated in detail to infer information about the stress regime of the cenozoic basin fill the detailed analysis of leak off test data from the bavarian foreland molasse basin and lithology dependent analysis of leak off test and formation integrity data is the first of its kind in a published study only test data from shale rich sequences have been considered all data yield minimum principal stresses that are smaller than an estimated vertical stress range in combination with critical stress and frictional equilibrium theory the data indicate that the stress regime in the greater munich area and possibly the far field stress regime of the bavarian foreland molasse basin are most likely of an extensional nature normal faulting stress regime under the assumption of frictional equilibrium a friction coefficient between 0 2 and 0 4 best explains failure in shale dominated sections of the central part of the bavarian foreland molasse basin and can be used to estimate the minimum horizontal stress shmin however even in the spatially restricted domain of the greater munich area the stress regime might vary towards a strike slip stress regime most likely in the vicinity of fault zones and or due to variations in mechanical rock strength the results of this study have great impact and relevance to improved planning of drilling campaigns future numerical modelling and the general understanding of the evolution of the bavarian foreland molasse basin additional leak off tests and extended leak off tests are recommended to fully unravel the spatial variation and geologic control factors of the stress regime of the entire bavarian foreland molasse basin

contemporary vertical velocity of the central basin and range and uplift of the southern sierra nevada 1 we estimate the present day vertical velocity field in the central basin and range and sierra nevada mountains and consider causative processes we analyzed data from 16 continuously operating global positioning system stations finding that relative vertical velocity precision wrms scatter is 0 25 mm yr these data demonstrate that the southern sierra nevada is experiencing uplift of 0 5 mm yr relative to a local reference frame in southern nevada and 1 mm yr relative to stations in the northern mojave desert as a possible source of these motions we explored post seismic viscoelastic relaxation following the 1872 owens valley and 1952 kern county earthquakes with models of laterally homogeneous lower crust and upper mantle viscosity post seismic deformation from these two earthquakes cannot entirely explain the data set lateral variations in viscosity or contributions from other regional earthquakes may also be important

130 000 yr continuous pollen record from clear lake lake county california pollen analysis of a 115 m sediment core from clear lake lake county california provides a climatic record that is continuous for the past 130 000 yr the pollen record reflects migrations of the tree species of the california coast ranges in response to the climatic changes of the last glacial cycle during interglacials the clear lake pollen rain was dominated by quercus oak pollen during cooler periods oak pollen was replaced by pollen of coniferous species the curve for quercus pollen strongly resembles and is used to correlate with both deep sea oxygen isotope curves and the climatic record from certain european pollen studies

genesis of soils and landscapes in the ridge and valley province of central pennsylvania abstract the characteristics and properties of the soils on the ridge tops footslopes and adjacent limestone valley areas in the ridge and valley of central pennsylvania have been strongly influenced by their parent material and geomorphic history the ridge top soils have developed in sandstone colluvium which mantles sandstone residuum the upper part of the original residual ridge top soil was truncated during late wisconsinan time and then covered with local colluvium or it was cyroturbated these sandstone parent materials have been stable since the late wisconsinan and have sandy skeletal dystrochrepts and haplorthods developed in them the haplorthods are minor soils and are associated with local concentrations of coniferous vegetation during the late wisconsinan the sandstone colluvium also moved downslope and was mixed with bedrock and residual material from shale and limestone and deposited on the footslope over a pre wisconsinan soil developed in older colluvium or limestone residuum the footslope surface colluvial soils vary in texture and drainage because of their parent material their location in discharge areas and fragipan development the age of the brown surface colluvium is considered late wisconsinan and the age of the pre wisconsinan buried soils is not known the buried soil s bright red rubified color and argillic horizon indicate a much greater degree of soil development than noted in the brown surface colluvium and its age may be correlated with isotope stage 6 the soils developed at the surface in the colluvium are mainly ultisols although some poorly drained soils particularly in limestone material are alfisols the ultisols are parent material ultisols and the poorly drained alfisols have a high base status in their parent material or were recharged with bases from the groundwater the soils of the limestone valleys are developed in residuum the residuum accumulated from the insoluble residues after the caco 3 was leached from the bedrock if the residuum is thick 2 to 3 m the soils date back many hundreds of thousands of years but are still classified as hapludalfs in addition to being old the surface of the hapludalfs has been modified by periglacial truncation and the addition of eolian materials these processes have given the upper 50 cm of the hapludalfs a late wisconsinan age but the bulk of the b horizon is many thousands of years older eolian material has also been added to the ridge top soils as well as the colluvial soils the mineralogy of all the soils in this landscape including the buried paleosols does not show significant clay mineral weathering this appears anomalous considering the degree of oxidation of the buried paleosols and the limestone soils and their estimated age

paleo geomorphology of the sierra nevada california from u th he ages in apatite new apatite u th he ages from the central sierra nevada california place limits on the morphology and evolution of longitudinal profiles of major transverse river drainages developed in the late cretaceous helium ages from a new orogen parallel constant elevation sample transect are relatively uniform 60 ma and not correlated with topography unlike those from a similar lower elevation transect approx 15 km to the west we interpret the marked difference in the two orogen parallel profiles to reflect a headward decrease in long wavelength transverse relief at the time of cooling consistent with either a concave up stream gradient typical of those observed near the headwaters of modern sierran trunk streams or a convex gradient like those found along slope breaks of eroding plateau edges from the san joaquin drainage we obtained a new helium age versus elevation profile which has a comparable slope to those previously reported for the yosemite valley kings canyon and mt whitney areas this new profile yields slightly older ages at a given elevation as expected from its position adjacent to the largest major drainage the age versus elevation profiles imply that the mean denudation rate of the region in the cenozoic was about 0 04 to 0 05 mm yr we show that long wavelength 70 km relief inferred from longitudinal helium age variations is a strong function of erosion rate such that even relatively subdued relief is detectable with helium age profiling provided that denudation rates were low using the rate implied by sierran age versus elevation profiles we infer long wavelength relief of 1500 500 m in the late cretaceous by analogy with modern orogenic plateaus this value of long wavelength relief suggests a cretaceous interior cordilleran plateau lay at an elevation of at least 3000 m