tectonic decapitation of a pliocene mega delta on isla del carmen in the gulf of california mexico and a river ran through it abstractthe tiombo conglomerate on isla del carmen in baja california sur represents a mega delta deposited mainly during the middle pliocene early piacenzian age a cross section with the characteristically arched profile of a fan delta is exposed in sea cliffs 60 m high that extend for 2 km along the east side of the fourth largest island in mexico s gulf of california a tidewater aspect to the delta is proven by the inclusion of fossil rich lenses dominated by the pecten patinopecten bakeri which also occurs abundantly together with many other middle pliocene fossils in the arroyo blanco limestone juxtaposed against the south flank of the delta construction inland the conglomerate fills a broad cross island channel approximately 3 km2 in area that ends with cliff exposures of a lesser thickness overlooking the carmen passage between isla del carmen and the peninsular mainland of baja california based on exposures that fail to reveal the full basal contact the combined fluvial and deltaic parts

high frequency cyclicity in a vertical alternation of gilbert type deltas and carbonate bioconstructions in the late tortonian tabernas basin southern spain abstract the deltaic succession in the tabernas basin represents the first deposition of marine sediments deposited during the late tortonian transgression that linked the mediterranean sea to the atlantic ocean through the basins of the betic cordillera the 100 m thick succession consists of seven 5 to 20 m thick vertically stacked wave dominated gilbert type deltas towards the top of each unit coral reef patches overlie the delta plain and are in turn overlain by calcarenites formed by accumulation of branching red algae colonies locally the calcarenite deposits fill microkarst depressions developed on the reefal carbonates during emergence unlike the corals the red branching algae colonies grew at a few metres depth under low energy conditions below wave base the calcarenites derived from branching red algae colonies formed when the delta plain was drowned creating the new accommodation space needed for the progradation of the delta forming of the overlying unit the repeated alternation of coral reef carbonates tropical carbonates and carbonates with bryomol skeletal assemblages temperate carbonates in the deltaic succession is linked to relative sea level changes reflecting the sum of glacio eustatic sea level fluctuations and tectonic subsidence each delta unit is represented by a transgressive systems tract built by the stacking of distributary mouth bars capped by reef patches a maximum flooding surface represented by branching red algal calcarenites and a highstand systems tract consisting of progradational wave dominated gilbert type delta because of the general increase in accommodation space controlled by glacio eustatic sea level rise and tectonic subsidence beach topset strata and distributary mouth bars were preserved in the cases studied subsidence rates exceeded the glacio eustatic sea level lows preventing the development of normal lowstand systems tracts in the delta stack

early deglaciation in the tropical andes the record of ancient glaciers is the principal source of information on high altitude paleoclimate in the tropics but the age of late pleistocene glaciation throughout the tropics is poorly constrained which complicates estimating past climate from glacial records seltzer et al 1 1

facies analysis of a pliocene river dominated deltaic succession siena basin italy implications for the formation and infilling of terminal distributary channels the recent recognition and description of terminal distributary channels in ancient delta front deposits have led to important progress when it comes to understanding delta construction processes the plan view shapes of both modern and ancient river dominated deltas and sediment dispersal within deltas deltaic deposits fed by terminal distributary channels can be observed in the extensive outcrops approximately up to 300 m wide and 50 to 70 m thick in the central sector of the pliocene siena basin in tuscany italy stratigraphic constraints indicate that the deposition occurred in relatively shallow marine settings was not affected by tidal effects and was influenced only locally by wave action as a consequence these rock exposures provide an opportunity to investigate the facies assemblage of an ancient delta complex which was built up almost exclusively as the result of river related processes the studied deltaic succession is composed of vertically stacked parasequence like units which are invariably characterized by the lack of coarse grained distributary channel deposits at the top and an extensive network of terminal distributary channels that controlled the deltaic deposition these deposits were interpreted previously as deep water turbidites this study provides new elements for the correct distinction between hyperpycnal dominated delta fronts and basinal turbidite deposits the terminal distributary channel facies documented in this study are more complex than those investigated in previous research the channels are often passively filled during abandonment phases and not just due to the aggradation and lateral upstream migration of mouth bars as classically proposed moreover the frequent occurrence of mudstone beds just above the basal channel scours may be indicative of an abandonment phase after the channel incision and before its infilling with subsequent implications for the formational and infilling mechanisms of terminal distributary channels furthermore the channel fills are often the result of alternating depositional and erosional phases leading to a complex stratigraphic arrangement

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

broad synchrony of a late glacial glacier advance and the highstand of palaeolake tauca in the bolivian altiplano the morphology and sedimentology of glacially influenced fan deltas on massifs at the margin of the southern altiplano bolivia suggest a broadly synchronous expansion of glaciers and palaeolake tauca during the late glacial interval this is shown by sedimentary successions of glacigenic glacifluvial and glacideltaic facies linking palaeoglaciers with palaeolake tauca on the flanks of cerro azanaques and cerro tunupa at altitudes of 3770 3720 m radiocarbon dates from peat overlain by glacial diamict and glacifluvial outwash indicate that glaciers in this area reached their last glacial maximum extent after ca 13 300 14 c yr bp glacifluvial fan deltas contiguous with the moraines confirm that the advance coincided with a highstand of palaeolake tauca radiocarbon dated to the interval ca 13 500 11 500 yr bp modeling of climatic controls on this glacier advance suggests the primary forcing was increased summer wet season moisture possibly amounting to 600 mm above the modern values of 200 400 mm greater cloud cover probably depressed local temperatures and reduced the evaporation rate the consequent rise in effective annual moisture p e comfortably accommodates a palaeolake 48 50 10 3 km 2 in area and up to 100 m deep in the southern altiplano because the palaeoglacier equilibrium line altitudes rose toward the south and west like the gradient of modern precipitation totals we conclude that the increased late glacial moisture was brought by weather systems similar to those of the present but that atmospheric conditions were cloudier and cooler 1997 john wiley sons ltd

shelf construction in a foreland basin storm beds shelf sandbodies and shelf slope depositional sequences in the upper cretaceous mesaverde group book cliffs utah the upper cretaceous campanian kenilworth member of the blackhawk formation mesaverde group is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of north america analysis of this section at a combination of small sedimentological and large stratigraphical scales reveals the dynamics of progradation of a shelf slope sequence into a subsiding foreland basin four major lithofacies are present in the upper mancos and kenilworth beds of the book cliffs a lag sandstone and channel fill shale lithofacies constitutes the thin basal transgressive sequence which rests on a marine erosion surface it was deposited in an outer shelf environment shale interbedded sandstone and shale and amalgamated sandstone lithofacies were deposited over the transgressive lag sandstone lithofacies as a wave dominated delta and its flanking strand plains prograded seaward analysis of grain size and primary structures in kenilworth beds indicates that there are four basic strata types which combine to build the observed lithofacies the fine to very fine grained graded strata of the interbedded facies are tempestites deposited out of suspension by alongshelf storm flows geostrophic flows there is no need to call on cross shelf turbidity currents density underflows to explain their presence very fine to fine grained hummocky strata are likewise suspension deposits created by waning storm flows but were deposited under conditions of more intense wave agitation on the middle shoreface cross strata sets in this region are bed load deposits that accumulated on the upper shore face in the surf zone lag strata are multi event bed load deposits that are the product of prolonged storm winnowing they occur on transgressive surfaces while the graded beds are tempestites in the strict sense all four classes of strata are storm deposits the distribution of strata types and their palaeocurrent orientations suggests a model of the kenilworth transport system driven by downwelling coastal storm flows and probably by a northeasterly alongshore pressure gradient the stratification patterns shift systematically from upper shoreface to lower shoreface and inner shelf lithofacies partly because of a reduction in fluid power expenditure with increasing water depth but also because of progressive sorting which resulted in a decrease in grain size in the sediment load delivered to successive downstream environments the kenilworth member and an isolated outlier the hatch mesa lentil constitute a delta prodelta shelf depositional system their rhythmically bedded lenticular sandstone and shale successions are a prodelta shelf facies and may be prodelta plume deposits major upper cretaceous sandstone tongues in the book cliffs are underlain by erosional surfaces like that beneath the blackhawk formation which extend for many tens of kilometres into the mancos shale these surfaces are the boundaries of upper cretaceous depositional sequences the sequences are large scale genetic stratigraphic units they result from the arranging of facies into depositional systems the depositional systems are in turn stacked in repeating arrays which constitute the depositional sequences the anatomy of these foreland basin sequences differs

new gas geothermometers for geothermal exploration calibration and application calibration of five gas geothermometers is presented three of which used co2 h2s and h2 concentrations in fumarole steam respectively the remaining two use co2h2 and h2sh2 ratios the calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures after establishing the gas content in the aquifer gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions it is shown that the concentrations of co2 h2s and h2 in geothermal reservoir waters are fixed through equilibria with mineral buffers at temperatures above 230 c epidote prehnite calcite quartz are considered to buffer co2 two buffers are involved for h2s and h2 and two functions are therefore presented for the geothermometers involving these gases for waters containing less than about 500 ppm chloride and in the range 230 300 c pyrite pyrrholite epidote prehnite seem to be involved but pyrite epidote prehnite magnetite or chlorite for waters above 300 c and waters in the range 230 300 c if containing over about 500 ppm the gas geothermometers are useful for predicting subsurface temperatures in high temperature geothermal systems they are applicable to systems in basaltic to acidic rocks and in sediments with similar composition but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones the geothermometry results may be used to obtain information on steam condensation in upflow zones or phase separation at elevated pressures measured aquifer temperatures in drillholes and gas geothermometry temperatures based on data from nearby fumaroles compare well in the five fields in iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected the results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled icelandic fields

modern and last local glacial maximum snowlines in the central andes of peru bolivia and northern chile late pleistocene snowlines in the central andes were 500 1200 m lower than at present radiocarbon dates imply that the late pleistocene glacial maximum in the region occurred prior to 20 14c ka but lack of maximum limiting ages adds considerable uncertainty to the exact timing snowline modeling demonstrates that snowlines in the eastern and western cordilleras of the central andes respond differently to temperature and precipitation changes in the eastern cordillera the snowline is near the level of the annual 0 c isotherm and melting occurs throughout the year here snowlines are sensitive to temperature changes but relatively insensitive to accumulation changes in the western cordillera the snowline rises 1000 higher owing to increasing aridity and the snowline exhibits a much stronger sensitivity to accumulation changes the consistent 1200 m snowline depression along the eastern cordilleras of the central andes can be modeled by a mean annual cooling of 5 9 c this is inconsistent with the 2 c cooling in tropical sea surface temperatures suggested by climap reconstructions the 800 1000 m snowline depression in the western cordillera cannot be accounted for solely by cooling but also requires an increase in precipitation

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

resistivity structure of the upper crust in iceland the results of numerous resistivity soundings from all parts of iceland are analyzed the resistivity and the p wave velocity of the uppermost kilometer in the crust show a strong correlation with the geological structure of iceland by estimating porosity from p wave velocity archie s law is found not to be valid in general the temperature dependence of nine water saturated basaltic rock samples was investigated in a laboratory showing stronger temperature dependence than expected from pore fluid conduction these two facts suggest that interface conduction is the most important conduction mechanism a relation between bulk resistivity fracture porosity pore fluid resistivity and temperature is established comparison of regional bulk resistivity with different zeolite zones shows that the resistivity is mainly a function of the maximum depth of burial of the lava pile emphasizing the importance of clay minerals and zeolites for the measured bulk resistivity

tropical climate at the last glacial maximum inferred from glacier mass balance modeling model derived equilibrium line altitudes elas of former tropical glaciers support arguments based on other paleoclimate data for both the magnitude and spatial pattern of terrestrial cooling in the tropics at the last glacial maximum lgm relative to the present lgm elas were maintained by air temperatures that were 3 5 to 6 6 c lower and precipitation that ranged from 63 wetter in hawaii to 25 drier on mt kenya africa our results imply the need for a 3 c cooling of lgm sea surface temperatures in the western pacific warm pool sensitivity tests suggest that lgm elas could have persisted until 16 000 years before the present in the peruvian andes and on papua new guinea

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

rapid incision of a small coarse and steep fan delta in response to base level fall the case of nahal qedem the dead sea israel the dead sea has been continuously dropping 0 4 1 0 m yr 1 since the middle of the 20th century and thus provides a unique field laboratory for studying in real time the response of drainage systems to a non tectonic base level fall the aim of this work is to study the short term ongoing erosive response to a rapid base level drop in a small steep fronted erodible fan delta setting the work explores the controls of the steep qedem fan delta guided by its clinoform structure on its incision longitudinal profiles of the fan delta and of its entrenched channel were measured in the field sedimentary facies changes fluviatile shallow lacustrine and beach were followed along exposures the existence of large boulders provided an opportunity to examine the uncertain role of armouring and boulder flux on incision the field study was combined with digital elevation models dems that were extracted from pairs of overlapping aerial photos maps of erosion and deposition were prepared using a change detection algorithm the longitudinal profile of the entrenched channel was found to be steep and linear the outlet temporarily hangs elevated and ungraded above the retreating lake level indicating years without incision flow events which cause lags in response to the rapid lake level drop in spite of the large boulders the small drainage basin and precipitation volume over the basin of the qedem the recorded vertical incision rates in the unconsolidated sediments are as high as 0 8 m yr 1 i e similar to those of the largest wadis draining to the dead sea the steep front of the fan delta is suggested to be a main factor controlling the efficient incision a unique transport mechanism of rolling boulders following undercutting contributed to the entrenchment efficiency copyright 2010 john wiley sons ltd

a sand gravel gilbert delta subject to base level change laboratory experiments were conducted on a sand gravel gilbert delta to gain insight on its dynamics under varying base level base level rise results in intensified aggradation over the topset as well as a decrease in topset slope and topset surface coarsening the signals of which migrate in an upstream direction preferential deposition of coarse sediment in the topset results in a finer load at the topset foreset break which creates a fine signature in the foreset deposit base level fall has the opposite effects entrainment of the topset mobile armor causes a coarsening of the load at the topset foreset break and so a coarse signature in the foreset deposit the entrainment of the topset substrate and fine top part of the foreset may follow which causes a fining of the load and a fine signature in the foreset deposit the fact that the upstream sediment supply requires a certain slope and bed surface texture to be transported downstream under quasi equilibrium conditions counteracts the effects of base level change this information travels in the downstream direction in nature base level change is likely so slow that the upstream sediment load maintains the topset slope and bed surface texture and so keeps the topset in a quasi equilibrium state base level change is therefore not expected to leave a clear signal in a mixed sediment gilbert delta other than a change in elevation of the topset foreset interface

the application of an indirect electromagnetic geothermometer to temperature extrapolation in depth we study the feasibility of the application of an indirect em geothermometer developed recently to the temperature extrapolation in depth using magnetotelluric data collected in the seismically active northern tien shan faulted area bishkek geodynamic test site kyrgyzstan and hengill geothermal zone iceland the approach used is based on the artificial neural network technique which does not imply the prior knowledge of the electrical conductivity mechanisms on the one hand and provides temperature estimates based on the analysis of the implicit conductivity temperature relations on the other the samples for neuronet teaching consisted in the well temperature records and electrical conductivity values determined for the same depths from the magnetotelluric data measured in the vicinities of eight boreholes in each testing area the testing of the taught neuronets was carried out using the temperature records not involved in the teaching process the results indicate that the temperature extrapolation accuracy essentially depends on the ratio between the well length and the extrapolation depth in particular in extrapolation to a depth twice as large as the well depth the relative error is 5 6 and in case of threefold excess the error is around 20 this result makes it possible to increase significantly the depth of indirect temperature estimation in the earth s interior in particular for geothermal exploration based on the available temperature logs the practical application of an indirect electromagnetic geothermometer could provide the following facilities 1 more exact temperature estimation in the extrapolation mode 2 remote temperature estimates in the boreholes in areas characterized by extreme conditions for conventional geothermometers

chronology for fluctuations in late pleistocene sierra nevada glaciers and lakes mountain glaciers because of their small size are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in greenland late in the last glacial period are part of global scale climate variability or are restricted to the north atlantic region correlation of cosmogenic chlorine 36 dates on sierra nevada moraines with a continuous radiocarbon dated sediment record from nearby owens lake shows that sierra nevada glacial advances were associated with heinrich events 5 3 2 and 1

a new conceptual model of the icelandic crust in the hengill geothermal area based on the indirect electromagnetic geothermometry abstract application of the indirect electromagnetic geothermometer calibrated by available temperature well logs has enabled the construction of the three dimensional temperature model of the hengill geothermal area iceland up to a depth of 20 km its analysis showed that the background temperature of the icelandic crust above 20 km does not exceed 400 it is overlapped by a network of interconnected high temperature low resistive channels which braid through the crust mainly at a level of 10 15 km and root to a depth greater than 20 km accordingly the probable heat sources feeding the geothermal system are supposed to be the intrusions of the hot partially molten magma upwelling from the mantle through faults and fractures the comparison between the vertical temperature cross sections and the projections of the earthquake hypocenters showed that they all are located in the areas where temperature does not exceed 400 which is a gabbro solidus in a silica rich icelandic crust joint analysis of the temperature model together with the resistivity and residual bouguer gravity anomalies enabled us to explain the distribution of the earthquake hypocenters by different geothermal regimes in adjacent parts of the area and cooling of large massifs of the partially molten solidified magma beneath seismically active areas basing on the above inferences we suggest a new self consistent conceptual model of the icelandic crust which agrees with most of the previous geophysical results and provides an explanation for the facts that the previous models failed to explain

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

tectonically induced adjustment of passive margin accommodation space influence on the hydrocarbon potential of the orange basin south africa a seismic stratigraphic investigation integrated with the structural modeling of the southern part of the orange basin passive margin south africa demonstrates that a single tectonic event resulted in a significant alteration to both the location and style of sediment accumulation during its postrift evolution this alteration to the margin has a significant effect on the hydrocarbon system of the area we predict that it increased the hydrocarbon potential of the area the evolution of the margin can be divided into two principal phases the first comprised an overall aggradational shelf margin with little or no deformation during the cretaceous deposition during the late cretaceous was punctuated by an episode of margin tilting that resulted in significant erosion of the inner margin and alteration of the margin architecture the second phase of deposition during the tertiary occurred to the west of the cretaceous shelf margin and was characterized by significant margin instability and the development of a coupled growth fault and toe thrust system this change in passive margin configuration and the associated switch in the location of overburden accumulation is likely to have increased the petroleum prospectivity of the deep water part of the margin we predict that the rapid western seaward migration of sediment accumulation resulted in the maturation of the high quality distal source interval whereas the resulting toe thrust geometry provides suitable structural traps for the hydrocarbons

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

the effects of fluctuating base level on the structure of alluvial fan and associated fan delta deposits an example from the tertiary of the betic cordillera spain the villanueva complex is a lacustrine alluvial fan fan delta system which accumulated on the northern margin of the guadix basin during the pliocene five transitional zones can be distinguished from proximal to distal areas proximal alluvial fan mid fan fan fringe transition zone proximal fan delta and distal fan delta lacustrine this paper focuses on sedimentation in the fan fringe and the proximal fan delta areas where the effects of fluctuations in the base level lacustrine level are more easily observed the stratigraphical succession is here characterized by an alternation of fine lacustrine sediments mudstones and siltstones and gravels the gravels appear as isolated channels stacked channels lenses and sheets the isolated channels which have a v shaped profile and better developed wings towards the top appear in the fan fringe zone and in the fan delta the stacked channels originate in the fan fringe zone and evolve laterally and distally to isolated channels the lenticular gravel bodies lenses are well represented throughout the fan delta and present small channels at the base indicating a radial flow pattern finally the sheets are characteristic of the fan fringe zone the first episodes of channel incision occurred at lowstand lake level the channels and lenses developed in rising lake level conditions and sheet deposit took place at highstand lake level although the final form of the lithosome was heavily controlled by the fluctuations in lake level it depended on the relative proportions of gravel and silt sedimentation the gravel siltstone interface therefore represents an equilibrium surface between the proportions of sedimentation of these lithologies the bodies mentioned above are organized in coarsening and thickening upwards sequences tens of metres thick in which a distal to proximal evolution can be observed from isolated channels to lenses or from stacked channels to sheets the building and thickness of these sequences were controlled by fluctuations in the lake level an initial fall in base level caused lengthening of the channels and entrenchment from distal to proximal areas and a continuous increase in supply due to erosion in the drainage basin installed on the subaerial fan when the lake level rose lobes were formed at the channel endings and overbank processes were made possible thus generating radial channels whose levees were formed by amalgamation with the levees of the main lens channels at the same time sheets were formed in proximal areas where the available amount of sediment was greater

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

amplitude frequency and drivers of caspian sea lake level variations during the early pleistocene and their impact on a protected wave dominated coastline the caspian sea the largest isolated lake in the world witnessed drastic lake level variations during the quaternary this restricted basin appears very sensitive to lake level variations due to important variations in regional evaporation precipitation and runoff the amplitude frequency and drivers of these lake level changes are still poorly documented and understood studying geological records of the caspian sea might be the key to better comprehend the complexity of these oscillations the hajigabul section documents sediment deposited on the northern margin of the kura basin a former embayment of the caspian sea the 2035 m thick well exposed section was previously dated by magneto biostratigraphic techniques and provides an excellent record of early pleistocene environmental lake level and climate changes within this succession the 1050 m thick apsheronian regional stage between ca 2 1 ma and 0 85 ma represents a particular time interval with 20 regressive sequences documented by sedimentary and palaeontological changes sequences are regressing from offshore to coastal lagoonal or terrestrial settings and are bounded by abrupt flooding events sediment reveals a low energy wave dominated reflective beach system wave baselines delimiting each facies association appear to be located at shallower bathymetries compared to the open ocean water depth estimations of the wave baselines allow reconstruction of a lake level curve recording oscillations of ca 40 m amplitude cyclostratigraphic analyses display lake level frequency close to 41 kyr pointing to allogenic forcing dominated by obliquity cycles and suggesting a direct or indirect link with high latitude climates and environments this study provides a detailed lake level curve for the early pleistocene caspian sea and constitutes a first step towards a better comprehension of the magnitude occurrence and forcing mechanisms of caspian sea lake level changes facies models developed in this study regarding sedimentary architectures of palaeocoastlines affected by repeated lake level fluctuations may form good analogues for other semi isolated basins worldwide

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

the deep geothermal structure of the mid atlantic ridge deduced from mt data in sw iceland iceland is very active tectonically as it is crossed by the mid atlantic ridge and its associated rift zones and transform faults the high temperature geothermal systems are located within the neo

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

depositional record of an avulsive fluvial system controlled by peat compaction neogene most basin czech republic this paper illustrates the response of a fluvial depositional system to the interplay between peat compaction and clastic sediment supply at a range of spatial and temporal scales as documented by extensive exposures in an open cast mine in the most basin part of the oligo miocene oh e rift eger graben basin system in the czech republic the most basin is characterized by the occurrence of a number of phenomena resulting from syn and post depositional interactions between clastic sedimentary systems and the underlying accumulation of organic material that was the precursor of the main lignite seam of up to 45 m thickness the studied strata are interpreted as deposits of an avulsive mixed load fluvial system the large scale depositional architecture documents an existence of at least five stratal packages up to 1500 m wide and up to several tens of metres thick representing a record of long term evolution of a clastic floodplain bordered by accumulating peat within each of the packages several small scale channel belts were documented individual packages are separated by carbonaceous mudstones indicating a period of reduced clastic input and interpreted as due to avulsion of the fluvial channels out of the floodplain limit two main mutually linked processes controlled the evolution of the studied fluvial system i syndepositional compaction of the underlying peat and ii avulsions of the channels away from the original floodplain resulting in formation of a new floodplain the processes which caused the channels of the hrabak fluvial system to reach the avulsion threshold were i decrease of rate of creation of accommodation leading to increased sinuosity and thus to a decreased channel slope and ii cross floodplain tilting of the channel belt caused by differential compaction of underlying organic rich substratum

depositional systems and sequence stratigraphy of coarse grained deltas in a shallow marine strike slip setting the bohemian cretaceous basin czech republic deposits of coarse grained gilbert type deltas showing varying degrees of reworking of foresets by basinal currents were identified in middle turonian to early coniacian sandstones of the bohemian cretaceous basin the progradation of the deltaic packages earlier interpreted as large scale subaqueous dunes shelf ridges or subaqueous fault scarp accumulation terraces was controlled by high and low frequency relative sea level changes in a relatively slowly subsiding intracontinental strike slip basin end member types of the bohemian cretaceous coarse grained deltas are deep water deltas characterized by thick 50 80 m foreset packages with steep 10 30 foresets and shallow water deltas which deposited thin 15 m packages with foresets typically between 4 and 10 the differences in thickness and foreset slope angle were controlled predominantly by the accommodation available during progradation the depositional regime of the deltas was governed by i the fluvial input of abundant sand bedload with a minor proportion of gravel ii gravity flows most probably caused by liquefaction of the upper part of the unstable foreset slope and iii migration of sandy bedforms on the foreset slopes the bedform migration was driven by unidirectional currents of possible tidal origin individual foreset packages represent systems tracts or parts of systems tracts of depositional sequences a variety of stacking patterns of high frequency sequences exists in the basin caused by low frequency relative sea level changes as well as by local changes in sediment input because of generally low subsidence rates fluvial or beach topset strata were not preserved in the cases studied the absence of preserved fluvial facies which has been one of the main arguments against the fluvio deltaic origin of the sandstone bodies is explained by erosion of the topsets during transgression and their reworking into coarse grained lags of regional extent covering ravinement surfaces

a northern lead in the orbital band north south phasing of ice age events abstract re analysis of existing data sets shows that they are fully consistent with northern insolation control of ice age cycles and do not provide strong support for alternate models invoking tropical or southern controls the coldest time of the last 100 ka in central greenland was nearly synchronous with the minimum in summer insolation about 24 ka bp thousand years before 1950 approximately one third of the total termination i warming since then was achieved over the almost 10 ka before the abrupt warming into the bolling which some workers have interpreted as the start of the warming southern warming as recorded in the byrd station antarctica ice isotopic record lagged northern warming co2 rise was roughly synchronous with southern warming methane rise may have been delayed a little as was sea level rise and the change in the isotopic composition of atmospheric oxygen was delayed significantly the data for the extrema just before termination ii are consistent with occurrence of the same phasing as for termination i but with somewhat different progression of the two terminations once initiated perhaps because of differences in the forcing

the sisters creek formation pleistocene sediments representing a nonglacial interval in southwestern british columbia at about 18 ka sisters creek formation is formally defined stratotypes are established for it and the time space chart is updated for the fraser lowland southwestern british columbia the sisters creek is a pleistocene formation comprising in situ and reworked organic rich sediments and nonorganic silt sand and gravel the formation was deposited during the port moody interstade within the late wisconsinan fraser glaciation 18o stage 2 between the coquitlam stade early fraser glaciation and the main vashon stadial maximum that occurred about 14 5 ka the sisters creek formation represents a glacial recession in southwestern british columbia that generally coincided with the timing of the last global glacial maximum the new time space chart implies that in fraser lowland the fraser glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains which remained ice covered during interstades

eocene post rift tectonostratigraphy of the rockall plateau atlantic margin of nw britain linking early spreading tectonics and passive margin response a regional study of the eocene succession in the uk sector of the rockall plateau has yielded new insights into the early opening history of the ne atlantic continental margin data acquired from british geological survey borehole 94 3 on the rockall high provides a high resolution record of post rift early to mid eocene subaqueous fan delta development and sporadic volcanic activity represented by pillow lavas tuffs and subaerial lavas this sequence correlates with the east rockall wedge which is one of several prograding sediment wedges identified across the rockall plateau whose development was largely terminated in the mid lutetian linking the biostratigraphical data with the magnetic anomaly pattern in the adjacent ocean basin indicates that this switch off in fan delta sedimentation and volcanism was coincident with the change from a segmented transform margin to a continuously spreading margin during chron c21 however late stage easterly prograding sediment wedges developed on the hatton high during late mid to late eocene times these can only have been sourced from the hatton high which was developing as an anticline during this interval this deformation occurred in response to mid to late eocene compression along the ocean margin possibly associated with the reorganisation to oblique spreading in the iceland basin which culminated at the end of the eocene with the formation of the north hatton anticline and the deformation tilting of these wedges a series of intra eocene unconformities of which the mid lutetian unconformity is the best example has been traced from the rockall plateau to the faroe shetland region and onto the greenland conjugate margin bordering the early ocean basin whilst there appears to be some correlation with 3rd order changes in eustatic sea level it is clear from this study that tectonomagmatic processes related to changes in spreading directions between greenland and eurasia and or mantle thermal perturbations cannot be discounted

morphology and sedimentology of two contemporary fan deltas on the southeastern baja california peninsula mexico abstract the san juan de los planes drainage basin is located on the southeastern margin of the baja california peninsula approximately 20 km southeast of the city of la paz pleistocene alluvial fans have been built into the basin from the surrounding areas of high relief and are presently being eroded at the fan apex the dissection depth ranges from 20 to 40 m and is 6 to 15 m at the coast the sediments have been redeposited in several active modern fan deltas built out into the narrow shelf of la ventana bay shelf width ranges from 0 to 5 km average 3 km wave energy is delivered from southeasterly storms and from the local sea breeze winds the respective wave heights average 2 and 1 m the agua caliente and las canoas fan deltas the subjects of this paper are located on the active el sargento fault zone and are fed by channels that deeply dissect the older fan surfaces the agua caliente fan delta is a classic gilbert type delta with a steeply inclined delta front wave reworking and redistribution of the sediments at the delta face are important and a wave cut terrace has developed at about 6 m depth the las canoas fan delta is a shoal water profile hjulstrom type with a gently inclined delta front wave energy is less important the alignments of the coasts of both fans are controlled by the fault line sediment supply is largest for the las canoas fan delta the fan deltas are examples of this depositional form as it has developed in an arid tectonically active high relief and narrow neo trailing edge margin

architectural stacking patterns of the ebro delta controlled by holocene high frequency eustatic fluctuations delta lobe switching and subsidence processes abstract during the late pleistocene and holocene 125 ka b p to present a type 1 4th order depositional sequence comprising regressive lowstand transgressive and highstand system tracts formed worldwide the holocene 10 ka b p to present part of this contains the latest and present highstand systems tract hst within this and the underlying transgressive systems tract tst of the ebro delta in northeastern spain higher frequency 5th to 6th order sea level fluctuations are recognised these form retrogradational and progradational high frequency depositional sequence sets within the tst and hst respectively each high frequency sequence comprises 1 a basal highly reflective shell lag associated with an erosional transgressive surface 2 aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies but inland are represented by thick peats 3 progradational deposits composed of sandy delta front facies displaying slope clinoforms these pass seawards into prodeltaic grey silts and landwards into red silts and pebbly sands of delta plain facies the progradational deposits downlap towards their bases the aggradational deposits formed in response to a period of rising sea level and a rapid increase in accommodation space progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea level fall the relative sea level curve for the delta has a stepped character caused by the punctuation of the 4th order sea level trend by higher frequency eustatic fluctuations as well as by high subsidence rates of about 1 75 mm per year the tst comprises retrogradational parasequences that onlap the underlying pleistocene gravels the maximum flooding surface separating the tst from the hst was formed about 6900 yrs b p on the basis of14c dating of peats the hst comprises progradational deltaic and aggradational units stacked as progradational high frequency parasequence sets the hst of the ebro delta is compared with other deltaic sequences around the world in particular with that of the mississippi delta a tentative chronology of the high frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented

electrical conductivity temperatures and fluids in the lower crust we have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models we avoided those data where purely conductive heat flow suggested temperatures more than about 1000 sup 0 c substantially higher than solidus temperatures and outside the range of validity of heat flow models the resulting plots of log conductivity sigma versus 1 t demonstrate that even low conductivity layers lcl have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits in addition tectonically active regions show systematically higher conductivities than do shield areas because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions these materials probably account for the relatively higher conductivities of rocks in situ in the crust free water in amounts of 0 01 0 1 in fracture porosity could explain crustal conductivities other possibilities are graphite hydrated minerals in rare instances and sulfur in combination with other volatiles as most of the temperatures are less than 700 sup 0 c partial melting seems likely onlymore in regions of highest heat flow where the conductive temperature profiles are inappropriate another result is that at a given temperature crustal high conductivity layes hcl are more conductive by another order of magnitude and show more scatter than do lcl s less

experimental delta formation in crater lakes and implications for interpretation of martian deltas 1 the morphology of delta deposits in crater lakes on mars is indicative of upstream e g flow discharge and sediment properties and downstream e g basin characteristics parameters from which the hydrological conditions at the time of formation can be inferred to investigate the influences of these parameters on delta morphology we experimentally created deltas in crater shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures we reproduced three categorically different types of deltas including most of the types that have been identified on mars our most striking observation is that water level behavior itself a unique function of flow discharge basin size and hypsometry and basin floor permeability can explain most delta morphologies observed on mars stepped retrograding deltas formed during water level rise prograding deltas formed during water level still stand and during water level fall deltas were partially destroyed by erosion on mars numerous retrograding and prograding deltas were preserved most of them without indications of channel incisions or other fluvial modification we conclude that the main difference between a single foreset prograding delta and a multiple foreset retrograding delta is the behavior of the water level in the basin these simple delta morphologies cannot be reconciled with long duration hydrological activity because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event which parsimoniously argues for short duration hydrological activity

extensive early and middle wisconsin glaciation on the western olympic peninsula washington and the variability of pacific moisture delivery to the northwestern united states abstract large glaciers descended western valleys of the olympic mountains six times during the last wisconsin glaciation terminating in the pacific coastal lowlands the glaciers constructed extensive landforms and thick stratigraphic sequences which commonly contain wood and other organic detritus the organic material coupled with stratigraphic data provides a detailed radiocarbon chronology of late pleistocene ice margin fluctuations the early wisconsin lyman rapids advance which terminated prior to ca 54 000 14c yr b p represented the most extensive ice cover subsequent glacier expansions included the hoh oxbow 1 advance which commenced between ca 42 000 and 35 000 14c yr b p the hoh oxbow 2 advance ca 30 800 to 26 300 14c yr b p the hoh oxbow 3 advance ca 22 000 19 300 14c yr b p the twin creeks 1 advance 19 100 18 300 14c yr b p and the subsequent undated twin creeks 2 advance the hoh oxbow 2 advance represents the greatest ice extent of the last 50 000 yr with the glacier extending 22 km further downvalley than during the twin creeks 1 advance which is correlative with the global last glacial maximum local pollen data indicate intensified summer cooling during successive stadial events because ice extent was diminished during colder stadial events precipitation not summer temperature influenced the magnitude of glaciation most strongly regional aridity independently documented by extensive pollen evidence limited ice extent during the last glacial maximum the timing of glacier advances suggests causal links with north atlantic bond cycles and heinrich events

effects of the readvance of an ice margin on the seismic character of the underlying sediment abstract seismic stratigraphy from a 65 km long transect of the lake melville fjord basin southeast labrador canada has revealed seven cycles of ice front advance retreat from a stratigraphic interval which regionally is correlated to 10 9 ka bp a maximum thickness of 400 m of glacimarine sediments ice contact submarine fans and associated finegrained debris totally 9 8 km 3 was deposited the thick ice contact deposits terminal moraines provide evidence that the lake melville basin was occupied by a grounded temperate tidewater glacier during this early holocene period of deglaciation detailed interpretation of the acoustic architecture of four associated ice contact fans shows that they were formed mainly during advance of the ice front only thinner sediment packages were emplaced during ice front stillstand episodes a subglacial unit equivalent to these foreset subunits mapped on the ice proximal side of the fans is relatively uniform in thickness the subglacial unit is interpreted as a basal deformation layer formed during the ice front advance seismic data from lake melville support the idea of asymmetric ice front advance retreat cycles the individual cycle however shows a more complex pattern than the simple slow advance stillstand rapid retreat model as suggested from many modern tidewater glaciers if the regional chronology is correct these advance retreat cycles have an average duration of 150 yrs they apparently occurred during a period of drastic ablation of the laurentide ice sheet as a result of an unknown combination of extrabasinal and intrabasinal factors

sea level related architectural trends in coarse grained delta complexes distinct stratigraphical styles of delta development can be related to basically different patterns of relative sea level base level change 1 an overall rise with periods of standstill and without significant fall rs 2 an overall rise with superimposed falls rf 3 an overall fall with superimposed rises fr and 4 an overall fall with periods of standstill and no significant rises fs the related stratigraphical models contain either preserved elements of prototype deltas or show characteristic trends in development from one prototype delta into another each stratigraphical model is characterized by lateral and vertical lithofacies features which can be reasonably well established from outcrop in coarse clastic basin margins where age control is poor sedimentological and stratigraphical delta models as presented here may help refining reconstructions of basin fill patterns and basin subsidence kinematics

sequence stratigraphy of the mesozoic domeyko basin northern chile the domeyko basin of northern chile records late triassic to early cretaceous mixed carbonate and siliciclastic marine deposition along the western margin of gondwana sequence stratigraphical analysis has identified five long term sequences of 11 17 ma duration comparison of the relative sea level fluctuations interpreted from the domeyko basin succession with those documented from other similar aged south american marginal basins and northern hemisphere basins allows the distinction of regional from global events relative sea level fall in the early pliensbachian early aalenian and early valanginian and rises in the early hettangian early and late toarcian early and late bajocian late bathonian and early oxfordian of the domeyko basin appear time equivalent to similar events in other southern and northern hemisphere basins and are thus interpreted to be products of global sea level cycles long term relative sea level falls in the early bathonian late oxfordian early valanginian and rise in the late kimmeridgian are interpreted to be tectonically driven continental scale changes in sediment accommodation space the domeyko basin succession thus appears to have been dominantly controlled by global sea level fluctuations during the early to mid jurassic and by continental scale but not global fluctuations during the mid jurassic to mid cretaceous interpreted to have been driven by the fragmentation of gondwana

nass river on the move radar facies analysis of glaciofluvial sedimentation and its response to sea level change in northwestern british columbia the nass valley of northwestern british columbia is a glacial fiord containing extensive glaciomarine and glaciofluvial sediments two parallel braidplains separated by a bedrock ridge were deposited within the fiord mapping of these deposits led to the hypothesis that the braidplains must have terminated at deltas however a lack of surface exposures meant that ground penetrating radar was needed to investigate these deposits radar facies analysis aided in the identification of braidplain braid delta and glaciomarine depositional environments as well as underlying bedrock several deltas graded to different sea levels were discovered allowing inferences to be made about the relationship of falling sea level to sediment architecture the upper section of the western braidplain is graded to a sea level of 185 m above sea level asl indicating that the proto nass river flowed on the western side of the bedrock ridge when the sea was at that level however the river moved to the east side of the ridge as sea level fell depositing the extensive aiyansh braidplain braid delta which is graded to a 152 m sea level stand several other deltas also formed at this sea level stand avulsion occurred and the river flowed on the west side of the ridge again when sea level fell to 134 m asl the river remained in this position throughout late glacial time and eventually evolved into the modern nass river the coarse grained deposits are indicative of forced regression with both stepped top attached and detached stratal architecture present

controls on stratigraphic architecture in contemporaneous delta systems from the eocene roda sandstone tremp graus basin northern spain abstract the eocene roda sandstone of the spanish pyrenees is comprised of two coeval coarse grained delta systems which share correlatable surfaces but show a markedly different internal facies architecture the two deltas developed contemporaneously with the differences in internal architecture attributed to basin morphology and the role of two distinct sediment sources while the correlatability of the larger scale packages indicates an external allocyclic control as such the roda sandstone provides the possibility to address the relative roles of different parameters known to interact and control stratal architecture the roda sandstone crops out at the ne margin of the tremp graus basin a piggyback basin initiated in palaeogene times in the foreland of the southern pyrenees the study area 30 km2 is composed of the well understood and well exposed parts of the roda sandstone cropping out along the isabena valley and the less worked and less exposed outcrops to the north along barranco de ricans and barranco de codoneras data for this study include a combination of conventional sedimentology data coupled with analyses of 3d virtual outcrop models based on these methods 8 different facies associations have been distinguished their distribution suggests that the roda sandstone is composed of two different but coeval delta systems and their linked subenvironments a gilbert type delta outcropping along isabena valley and a shoal water fan delta along barranco de ricans and barranco de codoneras along the isabena valley the outcrops of the gilbert type deltaic system are composed of at least 6 distinct packages roda u z characterized by texturally mature delta front sandstones separated by offshore mudstones the stacked basinward stepping architecture of the roda u y units here represents a minimum of 3 major phases of sw directed progradation capped by hardground horizons formed during the subsequent flooding phases tidally modified delta front deposits found in the distal exposures of roda y represent the redistribution of the delta toeset by w nw directed ebb tidal currents active during advanced stages of progradation of the gilbert type delta the more gentle sloping shoal water fan delta system found in barranco de ricans and barranco de codoneras is characterized by progradational to aggradational stacking of texturally immature wave modified mouth bar sandstone packages separated by offshore mudstones the zone of interference between the gilbert type and shoal water delta is dominated by wave reworked sediments deposited as shoreface barrier and spit deposits biostratigraphic dating suggests that the roda sandstone was deposited during a 3rd order relative sea level cycle as a shelf margin systems tract however the stacking of the individual roda u y units demarcated by offshore mudstones both within the gilbert type and the shoal water deltaic systems suggest that 4th order fluctuations occurred these 4th order units are physically correlatable between the two deltaic systems which implies that both deltas responded synchronously to a combination of regional subsidence and eustatic sea level fluctuations the differing internal architecture such as the steeply dipping textural mature foreset beds of the gilbert type delta versus the more gentle sloping textural immature mouth bars of the shoal water fan delta are controlled by different hinterland characteristics and intrabasinal topography

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

subdivision of glacial deposits in southeastern peru based on pedogenic development and radiometric ages the cordillera vilcanota and quelccaya ice cap region of southern peru 13 30 14 00 s 70 40 71 25 w contains a detailed record of late quaternary glaciation in the tropical andes quantification of soil development on 19 moraine crests and radiocarbon ages are used to reconstruct the glacial history secondary iron and clay increase linearly in quelccaya soils and clay accumulates at a linear rate in vilcanota soils which may reflect the semicontinuous addition of eolian dust enriched in secondary iron to all soils in contrast logarithmic rates of iron buildup in soils in the cordillera vilcanota reflect chemical weathering high concentrations of secondary iron in vilcanota tills may mask the role of eolian input to these soils soil age estimates from extrapolation of field and laboratory data suggest that the most extensive late quaternary glaciation occurred 70 000 yr b p this provides one of the first semiquantitative age estimates for maximum ice extent in southern peru and is supported by a minimum limiting age of 41 520 14c yr b p a late glacial readvance culminated 16 650 cal yr b p in the cordillera vilcanota following rapid deglaciation of unknown extent an advance of the quelccaya ice cap occurred between 13 090 and 12 800 cal yr b p which coincides approximately with the onset of the younger dryas cooling in the north atlantic region moraines deposited 394 cal yr b p in the cordillera vilcanota and 300 cal yr b p on the west side of the quelccaya ice cap correlate with little ice age moraines of other regions

development of pleistocene glaciomarginal lake in the foreland of the sudetes sw poland abstract numerous glaciomarginal lakes existed during the pleistocene in the sudetes and their foreland sw poland because of damming off by an ice sheet in the mountain area they were formed in the valleys or intermountain basins during the phase of maximum ice extent in the mountain foreland they were developed at the front of the more active ice margin in the period preceding the maximum ice sheet advance the latter lakes were less confined by the topography and their contact with the ice sheet was often considerably larger this caused their different development the sedimentological development of a small lake of this type located near mokrzeszow was studied the lake was characterized by high variability in water level and high energy depositional processes because of its small size the lake responded very quickly to all changes in external factors the lake became filled mainly by a coarse grained delta this happened in several phases because the water level fluctuated considerably owing to oscillations in the ice sheet extent during lowstands the delta became incised locally subaqueous fans were formed the lake basin eventually became overridden by the ice sheet

early warming of tropical south america at the last glacial interglacial transition glaciation in the humid tropical andes is a sensitive indicator of mean annual temperature here we present sedimentological data from lakes beyond the glacial limit in the tropical andes indicating that deglaciation from the last glacial maximum led substantial warming at high northern latitudes deglaciation from glacial maximum positions at lake titicaca peru bolivia 16 s and lake junin peru 11 s occurred 22 000 to 19 500 calendar years before the present several thousand years before the bolling allerod warming of the northern hemisphere and deglaciation of the sierra nevada united states 36 5 to 38 n the tropical andes deglaciated while climatic conditions remained regionally wet which reflects the dominant control of mean annual temperature on tropical glaciation

evolution in basin fill style during the mesozoic gondwana continental break up in the godavari triple junction se india abstract consistent changes are observed in the mesozoic sedimentary lithofacies and palaeocurrents during the transition from the continental gondwana nw se trending chintalpudi graben cg to the coastal gondwana ne sw trending krishna godavari coastal basin kgcb in the godavari triple junction gtj the mesozoic continental gondwana sediments include the kamthi early triassic kota jurassic and gangapur early cretaceous formations coastal gondwana succession comprising the raghavapuram early cretaceous and the tirupati middle to late cretaceous formations transversely superimpose the continental gondwana the continental gondwana is mainly cross stratified sandstone and fossiliferous glossopteris and ptilophyllum flora clay assemblage of alluvial environment palaeocurrent is towards nw in the kamthi formation wnw in the kota formation and centripetal in the gangapur formation the raghavapuram formation kgcb comprises of grey carbonaceous clay sandstone association of se flowing delta plain distributories with inter distributory swamps and fossiliferous white clay a mix of ptilophyllum flora and invertebrate fauna of prodelta shallow marine environment the succeeding sandstone conglomerate facies of the tirupati formation middle to late cretaceous with se palaeocurrent indicates delta progradation whereas the infratrappean clay limestone beds mainly invertebrate fauna of maastrichtian age point to delta abandonment prior to the k t boundary volcanism tectono sedimentary model presented in this communication incorporates that the change from the continental gondwana to coastal gondwana had occurred in four stages during stage i late carboniferous to early jurassic the sediments were deposited by a north westerly flowing alluvial system whose distal source was located in southeast beyond the east coast of india stage ii middle to late jurassic is marked by westerly shift in palaeocurrents attributed to an obstruction caused by an upliftment of the mailaram high parallel to the ne sw eastern ghat trend stage iii early cretaceous is heralded by the onset of deltaic sedimentation in se due to separation of landmass that supplied detritus to the cg until the end of the jurassic during stage iv the delta progradation is accentuated by the basement uplift eastern ghat mobile belt it is suggested that the change over from continental gondwana to coastal gondwana had occurred over a time span of about 70 my between late jurassic to cretaceous and controlled by phase wise upliftment of the basement as a corollary to the gondwana continental break up

climatic and hydrologic oscillations in the owens lake basin and adjacent sierra nevada california oxygen isotope and total inorganic carbon values of cored sediments from the owens lake basin california indicate that owens lake overflowed most of the time between 52 500 and 12 500 carbon 14 14 c years before present b p owens lake desiccated during or after heinrich event h1 and was hydrologically closed during heinrich event h2 the magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 sierra nevada glaciations occurred between 52 500 and 23 500 14 c years b p most of the glacial advances were accompanied by decreases in the amount of discharge reaching owens lake comparison of the timing of glaciation with the lithic record of north atlantic core v23 81 indicates that the number of mountain glacial cycles and the number of north atlantic lithic events were about equal between 39 000 and 23 500 14 c years b p

reconstructing low levels of lake lisan by correlating fan delta and lacustrine deposits abstract reconstruction of paleo shorelines of lake lisan the late pleistocene precursor of the dead sea is based on sequence stratigraphy of fan delta and lacustrine deposits that are exposed at the perazim valley southwest of the dead sea the shoreline sediments are physically correlated with lacustrine aragonites their ages are determined by u series dating to establish a lake level curve for the time interval between 55 and 35 kyr during most of this period lake lisan was at a relatively low level which fluctuated between 280 and 290 m below sea level m bsl the minimum lake stand 330 m bsl was reached at 47 kyr and lasted for 3 4 kyr this episode is marked by a depositional hiatus in the section and formation of an erosional channel the studied period correlates with the global marine isotope stage 3 the low stand of lake lisan during most of this period indicates relative dry climatic conditions in the region

the wandering of the volga delta a response to rapid caspian sea level change due to its very low gradient and absence of tide and surf the volga delta is an even more extreme example of the fluvially dominated type than the mississippi delta however it differs from all other large delta systems in that it borders a closed basin the caspian sea now at 26 m below global sea level caspian sea level is much more dynamic than that of the world oceans and rises at present about 1 5 cm yr a hundred time the eustatic rate within the quatemary sea level oscillations of at least 5 orders of magnitudes have been distinguished which seem grossly out of phase with eustatic sea level between the weichselian early khvalyn highstand of 50 m and the early holocene mangyshlak lowstand at 80 m the apex of the volga delta has wandered over 700 km alongstream the present day volga delta is not a highstand deposit but probably represents a minor transgression in a major regressional stage the delta does not show a coarsening upwards sedimentary sequence but consists of a weichselian transgressional fining upwards sequence topped by eolian deposits in which the delta distributary channels have been incised present day sedimentation is limited to a narrow fringe along the delta front and to deeper waters over 200 km offshore sea level changes outpaced aggradation to such an extent that volga sediment is spread over the whole north caspian plain sequence stratigraphical principles are difficult to apply because sea level cycles of five orders of magnitude are superimposed and because there is not enough sediment loading or tectonic subsidence to create sufficient accommodation space

formation of glaciolacustrine late pleistocene end moraines in the tasman valley new zealand abstract detailed examination of the tekapo formation in the tasman valley new zealand has identified 20 facies and five facies associations these associations are delta foresets and bottomsets sediment density flows ice contact lake sediments with ice rafted debris and resedimentation deposits and outwash gravels interpretation of the sediment landform associations informed by observations at modern glacier termini suggests that the late pleistocene tekapo formation moraines have been formed by downwasting of a more expanded tasman glacier during the early stages of glacier retreat ponds on the glacier surface develop into thermokarst lakes which enlarge and coalesce to form a large supraglacial lake continued downwasting causes the lake outlet river to entrench into the impounding latero frontal ice cored moraine lowering the lake level this exposes lake bottom sediments and forms shorelines on the proximal slopes of the ice cored moraine as the ice cored moraine melts these lake sediments are deformed and deposited against the mt john moraine the observations and interpretations reported here suggest the late pleistocene end moraine is a constructional feature not a structural glaciotectonic feature as suggested by previous studies

the subsurface temperature assessment by means of an indirect electromagnetic geothermometer abstractadvances have been made in the subsurface temperature estimation basing on the indirect electromagnetic geothermometer the approach used was based on the artificial neural network technique which contrary to other available approaches does not imply the prior knowledge of the electrical conductivity mechanisms and rock properties application of the indirect em geothermometer to the interwell space interpolation in three areas tien shan kyrgyzstan soultz sous forets france and hengill iceland characterized by different geologic environments indicated that the temperature estimation errors are controlled by four factors faulting distance between the em site and the area where the temperature is estimated meteoric and groundwater flows and lateral geologic inhomogeneity although the latter factor is less restrictive if appropriate em inversion tools are used it was demonstrated that the extrapolation errors depend on two factors spacing between the em site and the borehole and ra

topography and significance of a basinwide sequence bounding erosion surface in the cretaceous cardium formation alberta canada abstract the cardium formation turonian coniacian upper cretaceous of the western interior seaway alberta contains six marine sandier upward successions bounded by seven basin wide erosion surfaces in the subsurface erosion surface e5 is associated with major oil and gas fields and is penetrated by thousands of wells a topographic map of e5 based on 6126 well logs and over 1100 measured cores shows a series of subparallel elongate highs steps and lows which trend northwest southeast parallel to tectonic trends and to the actively rising cordillera to the southwest the steps are about 10 km apart and the relative relief step to adjacent low is up to 25 m the steps are asymmetrical with a steeper face to the northeast the e5 erosion surface cuts into offshore marine hummock cross stratified sandstones and interbedded mudstones and it records a lowering of relative sea level our interpretation suggests that erosion was in neither a fully subaqueous nor a fully subaerial environment instead it involved relative sea level lowering and subaerial erosion followed by major modification of the landscape during transgressive shoreface erosion at times of relative stillstand during overall transgression gravel was supplied to the shoreface and was reworked a short distance alongshore by waves these conglomerates now form important oil and gas reservoirs the asymmetry of the steps and lows indicates that the originally flat sea floor was tilted northeastward immediately before erosion giving a gradient of about 1 1000 during transgression shorefaces were incised into the tilted surface to form a stepped morphology also during transgression the sea floor was gradually restored to its pre tilting position each of the six marine sandier upward sequences along with the erosion surface at the top occupies an average of 470 000 years and we estimate that transgression took at least 100 000 to 200 000 years

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

fluvial response to an historic lowstand of the great salt lake utah understanding fluvial adjustments to base level changes benefits the fields of sequence stratigraphy geomorphology and petroleum geology this investigation is a modern case study of the channel dynamics of lee creek and the goggin drain two streams that are part of the jordan river drainage into the endorheic great salt lake of northern utah a lacustrine system that has experienced multiple decadal scale base level changes since 1965 the lake level has fluctuated in elevation more than 6 m transitioning from an historic lowstand 1284 m a s l and in 2009 2010 approaching an historic lowstand this study uses detailed aerial images fieldwork and lidar data to link the modern geomorphology and channel hydraulics to specific variations in sediment transport channel form and avulsion behavior although lee creek and the goggin drain are situated only a few kilometers apart and share similar shore zone gradients substrates and vegetation patterns and have been subjected to the same changes in lake level their channel forms have evolved very differently differences in discharge patterns are likely the most influential factor causing the meandering form of lee creek and the braiding channel of the goggin drain despite the differences in discharge total sediment eroded from the two streams is comparable and can be attributed to similar stream power unit stream width in the two streams although lee creek has not recently been avulsive three major avulsions of the goggin drain have taken place since 1965 two possible styles of avulsion are interpreted an allogenic response to changing base level and an autogenic response dictated by channel morphology and hydraulics despite a wealth of available information avulsions cannot be unequivocally attributed to one style or another caution should be used when attempting to link the complex process of avulsion to causal mechanisms copyright 2011 john wiley sons ltd

the table rocks sandstone a fluvial friction dominated lobate mouth bar sandbody in the westphalian b coal measures ne england abstract westphalian b duckmantian alluvial coal measures along the northumberland coast ne england comprise coal capped coarsening upward crevasse splay sequences of shale siltstone and sandstone interbedded with a number of major distributary channel sandbodies including the table rocks sandstone lithofacies architectural analysis and outcrop geometries divide the table rocks sandstone into flaggy sandstone massive sandstone heterolithic and mudstone facies associations each comprising up to 7 lithofacies types the three sandy facies associations are characterised by lenticular bed geometries on different scales producing a hierarchy of lensoid packages and associated bounding surfaces all showing typical offset stacking patterns 1 lenses represent individual lenticular cross bed sets bounded by 1st order surfaces 2 packages of lenses called lens clusters are bounded by 2nd order surfaces and are the basic architectural building block of the sandy facies associations and 3 vertically stacked lens clusters called amalgamated lens clusters bounded by 3rd order surfaces the table rocks sandbody has a laterally extensive irregular lobate subsurface plan geometry it displays a radial palaeocurrent pattern with 180 dispersion and it forms part of a 14 m thick coarsening upward regressive sequence it is interpreted as a composite lobate crevasse splay delta system that prograded into a shallow interdistributary fresh to brackish water lake up to 14 m deep the shallow lake water fluvial input and extensive development of traction structures such as cross bedding and ripple cross lamination suggests a friction dominated delta in which the four facies associations can be interpreted in terms of discrete elements of the mouth bar environment the flaggy sandstone facies association represents the main axial part of the mouth bar system the erosively based massive sandstone facies association major subaqeous distributary channels the lithologically more variable heterolithic facies association the medial mouth bar and the mudstone facies association the distal mouth bar fringe and prodelta within this environmental setting amalgamated lens clusters are interpreted as small discrete mouth bar sand lobes whose offset imbricate stacking pattern reflects channel spacing and bifurcation the rate of channel shifting or shallow depths and lack of accommodation space thus lens clusters are interpreted as discrete growth elements of the mouth bar sand lobes and lenses as individual bedforms making up these growth elements because of the high rate of channel shifting lack of extensive erosion of the mouth bar lobes and deposition of low discharge fines the lobes retained much of their original depositional geometry thereby providing advantageous gradients for offset deposition and stacking of adjacent sand lobes although the delta complex was maintained by frequent crevassing from the feeder channel and by subsidence due to contemporaneous compaction and or local tectonism it was deeply incised on two occasions by subaqeous channels in response to high magnitude floods or falling lake level

sequence analysis of early saalian glacial lake deposits nw germany evidence of local ice margin retreat and associated calving processes abstract this paper presents a detailed analysis of high resolution facies architecture of glaciolacustrine ice margin deposits which formed at the southern margin of the scandinavian ice shield the ice margin depositional systems are characterised by coarse grained deltas and subaqueous fans which are formed by stacked transgressive regressive sequences recording an overall lake transgression interrupted by minor short term lake level falls the delta complexes at the northern margin of glacial lake rinteln are thought to reflect a relatively stable position of the ice margin in front of the weser chains mountain ridges the onset of delta progradation probably represents a halt in ice advance and a related high sediment supply period the sedimentary facies and depositional architecture resemble those of nonglacial gilbert type deltas except for the deposition of glacial debris the main delta progradation is recorded from the highstand systems tract when high meltwater and sediment discharge occurred during the melt season a forced regression during opening of outlets led to the formation of subaerially exposed sequence boundaries and the erosion of the highstand systems tract deeply incised channels incised valleys were filled during the subsequent transgression at the eastern lake margin subaqueous fan deposits reflect an unstable ice front that was rapidly retreating and subject to periodic calving which resulted in the generation of floating icebergs dumping ice rafted debris and ploughing into subaqueous fan deposits the rapid retreat of this eastern ice margin is interpreted to result from the overall lake level rise the fan stacking pattern and bulk geometry were determined by the ice front fluctuations the shifting of meltwater outlets and the short term lake level fluctuations depositional processes reflect the character of sediment supply and distance from the ice margin ice proximal upper fan deposits are characterised by coarse grained gravel deposited by debris flows that document continuous discharge slump and slide deposits are related to steep depositional slopes the mid fan contains basinward fining and thinning deposits of quasi steady and surge type high and low density turbidity currents indicating more ice distal and periodic deposition the outer fan deposits mainly consist of surge type low density turbidites and glacial debris dumped by icebergs the forcing parameters governing the development of depositional sequences in both delta and fan settings were lake level fluctuations sediment yield rates and physiography the depositional sequences were deposited on a time scale of seventh and eighth order high frequency cycles 101 102 years in this short time span lake level fluctuations were on the order of 120 m therefore accommodation space was largely controlled by lake level and subsidence can be ignored

interplay between tectonics and compaction in a rift margin lacustrine delta system miocene of the eger graben czech republic the early miocene bilina palaeodelta consists of fluvio deltaic and lacustrine clastics deposited along the south eastern margin of the extensional most basin part of the eger graben in north bohemia czech republic the bilina succession shows evidence of repeated advances of an axial deltaic system across a thick accumulation of organic material and clay in the hangingwall of an active fault exposures up to ca 4 5 km long in the bilina open cast mine help bridge the gap between seismic scale and typical outcrop scale of observation and thus allow the relationships between small scale and basin scale stratal geometries to be evaluated the bilina palaeodelta deposits include sand dominated fluvial channel fills and heterolithic sheets interpreted as delta plain strata sand dominated mouth bar wedges and heterolithic sheets of prodeltaic deposits passing distally into lacustrine clays the depositional environment is interpreted as a fluvial dominated mixed load lacustrine delta with a high degree of grain size segregation at the feeder channel mouths on the largest temporal and spatial scales variable tectonic subsidence controlled the overall advance and retreat of the delta system the medium term transgressive regressive history was probably driven by episodes of increased subsidence rate however at this temporal scale the architecture of the deltaic sequences deltaic lobes and correlative lacustrine deposits was strongly affected by i compaction of underlying peat and clay which drove lateral offset stacking of medium term sequences and ii growth of a fault propagation fold close to the active bilina fault at the smallest scale the geometries of individual mouth bars and groups of mouth bars short term sequences reflect the interaction among sediment loading compaction and growth faulting that produced high frequency relative lake level fluctuations and created local accommodation at the delta front

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

temperature profiles in the earth of importance to deep electrical conductivity models deep in the earth the electrical conductivity of geological material is extremely dependent on temperature the knowledge of temperature is thus essential for any interpretation of magnetotelluric data in projecting lithospheric structural models the measured values of the terrestrial heat flow radiogenic heat production and thermal conductivity of rocks allow the extrapolation of surface observations to a greater depth and the calculation of the temperature field within the lithosphere various methods of deep temperature calculations are presented and discussed characteristic geotherms are proposed for major tectonic provinces of europe and it is shown that the existing temperatures on the crust upper mantle boundary may vary in a broad interval of 350 1 000 c the present work is completed with a survey of the temperature dependence of electrical conductivity for selected crustal and upper mantle rocks within the interval 200 1 000 c it is shown how the knowledge of the temperature field can be used in the evaluation of the deep electrical conductivity pattern by converting the conductivity versus temperature data into the conductivity versus depth data

distributary channels and their impact on sediment dispersal a global analysis of world deltas with details from a natural and an anthropogenic influenced delta demonstrates how distributary channels control the flux of sediment into the coastal ocean the study addresses the range in the number of distributary channels across world deltas using remote sensing techniques a power law relationship is found between the number of distributary channels and the length of river and separately the delta gradient these relationships hold for all types of deltas whether controlled or strongly influenced by waves river discharge tides or ice permafrost or sea ice nature controlled deltas such as the klinaklini delta have distributary channels that act as overflow conduits that become active during flooding events anthropogenic controlled deltas like the po delta have distributary channels that are controlled for flood mitigation or low flow maintenance anthropogenic influences greatly impact the natural rate of delta progradation through changes in sediment supply controlling the position of distributary channels and impacting subsidence from gas and groundwater extraction even with flood controls the po delta traps 16 of the sediment load in its channels that are becoming super elevated at rates of 4 to 10 cm yr with respect to the delta plain a new model is formulated and shown to predict accurately the sediment flux through each channel along with their hydraulic properties deltas with high numbers of distributary channels produce hypopycnal plumes with reduced transport capacity as a result sediment diffuses out of the multi channel deltas as a buoyantly driven plume rather than as a momentum driven jet