kinematic evolution of the junction of the san andreas garlock and big pine faults california if the san andreas fault with about 300 km of right slip the carlock fault with about 60 km of left slip and the big pine fault with about 15 km of left slip are considered to have been contemporaneously active a space problem at their high angle junctions becomes apparent large crustal masses converge in the area of the junctions as a result of the simultaneous large displacements on the faults we present here a model in which an early straight north northwest trending san andreas deforms to its present bent configuration in response to a westward displacement of crust north of the garlock fault during this deformation the crust north of the garlock in the vicinity of the junction undergoes north south shortening while the fault junction migrates along the trace of the san andreas fault to the southeast relative to its original position as a result of this migration the mojave area is displaced to the east relative to the original junction position we suggest a similar history in mirror image for the big pine fault and the areas of crust adjacent to it

late cenozoic tectonics of the east ventura basin transverse ranges california the east ventura basin originated in the middle miocene as a rift system bounded on one side by the oak ridge simi hills structural shelf and on the other side by a granitic ridge parallel to the san gabriel fault this fault began accumulating right slip 10 12 m y ago at a rate of 4 5 9 mm yr depending on whether total slip is 45 or 60 km slowing to about 1 mm yr in the quaternary north of the santa clara river rifting ended prior to deposition of the uppermost miocene lower pliocene towsley formation south of the santa clara river the rift axis shifted southwest toward the oak ridge simi hills shelf as the towsley formation accumulated against a normal fault ancestor of the santa susana fault a change to contractile tectonics occurred in the pliocene with depos tion of the fernando formation when the newhall potrero anticline developed as a monocline above a blind reverse fault the pico anticline to the southeast and the temescal and hopper ranch modelo anticlines to the northwest may have a similar origin tectonic inversion and displacement on the southwest verging santa susana fault began about 0 5 ma based on appearance of locally derived clasts in the upper saugus formation and its equivalents and continues today along with the southwest verging san cayetano fault farther west also active are northeast verging backthrusts occurring in the east ventura basin fold belt and a segment of the san gabriel fault which now acts as a northeast dipping oblique slip reverse fault northeast trending discontinuities and structures divide the present deformation zone into four segments in the hopper canyon segment at the west end of the area in the west ventura basin the san cayetano fault places miocene modelo formation over pliocene pleistocene strata more than 5 km thick largely at maximum burial to the southeast the newhall potrero segment is characterized by north vergent backthrusts within the east ventura fold belt and by southward thrusting of the basin sequence tectonic inversion over the structural shelf on the santa susana fault farther southeast the placerita segment is marked by reverse faulting on both the santa susana fault and the san gabriel fault southeast of the basin in the san fernando valley the sylmar segment contains a thick pli cene pleistocene sequence overridden by basement rocks of the san gabriel mountains as well as the south verging mission hills granada hills and northridge hills fault zones

ice sheet sources of sea level rise and freshwater discharge during the last deglaciation we review and synthesize the geologic record that constrains the sources of sea level rise and freshwater discharge to the global oceans associated with retreat of ice sheets during the last deglaciation the last glacial maximum 26 19 ka was terminated by a rapid 5 10 m sea level rise at 19 0 19 5 ka sourced largely from northern hemisphere ice sheet retreat in response to high northern latitude insolation forcing sea level rise of 8 20 m from 19 to 14 5 ka can be attributed to continued retreat of the laurentide and eurasian ice sheets with an additional freshwater forcing of uncertain amount delivered by heinrich event 1 the source of the abrupt acceleration in sea level rise at 14 6 ka meltwater pulse 1a 14 15 m includes contributions of 6 5 10 m from northern hemisphere ice sheets of which 2 7 m represents an excess contribution above that derived from ongoing ice sheet retreat widespread retreat of antarctic ice sheets began at 14 0 15 0 ka which together with geophysical modeling of far field sea level records suggests an antarctic contribution to this meltwater pulse as well the cause of the subsequent younger dryas cold event can be attributed to eastward freshwater runoff from the lake agassiz basin to the st lawrence estuary that agrees with existing lake agassiz outlet radiocarbon dates much of the early holocene sea level rise can be explained by laurentide and scandinavian ice sheet retreat with collapse of laurentide ice over hudson bay and drainage of lake agassiz basin runoff at 8 4 8 2 ka to the labrador sea causing the 8 2 ka event

a model of the western laurentide ice sheet using observations of glacial isostatic adjustment we present the results of a new numerical model of the late glacial western laurentide ice sheet constrained by observations of glacial isostatic adjustment gia including relative sea level ind

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

assimilating the ice 6g_c reconstruction of the latest quaternary ice age cycle into numerical simulations of the laurentide and fennoscandian ice sheets we analyze the effects of nudging 100 kyr numerical simulations of the laurentide and fennoscandian ice sheets towards the glacial isostatic adjustment based gia based ice 6g c reconstruction of the most recent ice age cycle starting with the ice physics approximations of the pism ice sheet model and the searise simulation protocols we incorporate nudging at characteristic time scales f through anomalous mass balance terms in the ice mass conservation equation as should be expected these mass balances exhibit physically unrealistic details arising from pure gia based reconstruction geometry when nudging is very strong f 20 yr for north america while weakly nudged f 1000 yr solutions deviate from ice 6g c sufficiently to degrade its observational fit quality for reasonable intermediate time scales f 100 yr and 200 yr we perturbatively analyze nudged ice dynamics as a superposition of leading order smoothing that diffuses ice 6g c in a physically and observationally consistent manner and higher order deviations arising for instance from biases in the time dependence of surface climate boundary conditions based upon the relative deviations between respective nudged simulations in which these biases follow surface temperature from ice cores and eustatic sea level from marine sediment cores we compute ice core climate adjustments that suggest how local paleoclimate observations may be applied to the systematic refinement of ice 6g c our results are consistent with a growing body of evidence suggesting that the geographical origins of meltwater pulse 1b mwp1b may lie primarily in north america as opposed to antarctica as reconstructed in ice 6g c

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

sea level constraints on the amplitude and source distribution of meltwater pulse 1a sea level rose rapidly during meltwater pulse 1a about 14 500 years ago a reassessment of sea level rise and isostatic adjustment suggests sea level rose roughly 8 to 15 m in total with 0 to 10 m derived from the antarctic ice sheets

late quaternary folding of coral reef terraces barbados uplifted late ouaternary coral reefs on the island of barbados record folding of the emergent crest of the lesser antilles accretionary prism barbados ridge complex since ca 1 ma three northeast striking folds are defined by systematic changes in altitudes in the crest of first high cliff a mostly constructional reef terrace about 125 ka and second high cliff a partially erosional reef terrace about 500 ka the folds have wavelengths of 6 to 8 km and fold axes extend about 10 km the largest anticline rises to the northeast where it has been breached by erosion exposing highly deformed eocene to lower miocene rocks of the scotland district uplift rates based on heights of the last interglacial first high cliff range from 0 07 to 0 44 mm yr quaternary folding on barbados indicates that the crest of the accretionary prism continues to be an active fold belt undergoing northwestsoutheast shortening

reef response to sea level and environmental changes during the last deglaciation integrated ocean drilling program expedition 310 tahiti sea level the last deglaciation is characterized by a rapid sea level rise and coeval abrupt environmental changes the barbados coral reef record suggests that this period has been punctuated by two brief intervals of accelerated melting meltwater pulses mwp occurring at 14 08 13 61 ka and 11 4 11 1 ka calendar years before present that are superimposed on a smooth and continuous rise of sea level although their timing magnitude and even existence have been debated those catastrophic sea level rises are thought to have induced distinct reef drowning events the reef response to sea level and environmental changes during the last deglacial sea level rise at tahiti is reconstructed based on a chronological sedimentological and paleobiological study of cores drilled through the relict reef features on the modern forereef slopes during the integrated ocean drilling program expedition 310 complemented by results on previous cores drilled through the papeete reef reefs accreted continuously between 16 and 10 ka mostly through aggradational processes at growth rates averaging 10 mm yr 1 no cessation of reef growth even temporary has been evidenced during this period at tahiti changes in the composition of coralgal assemblages coincide with abrupt variations in reef growth rates and characterize the response of the upward growing reef pile to nonmonotonous sea level rise and coeval environmental changes the sea level jump during mwp 1a 16 2 m of magnitude in 350 yr induced the retrogradation of shallow water coral assemblages gradual deepening and incipient reef drowning the tahiti reef record does not support the occurrence of an abrupt reef drowning event coinciding with a sea level pulse of 15 m and implies an apparent rise of 40 mm yr 1 during the time interval corresponding to mwp 1b at barbados

microbialite development patterns in the last deglacial reefs from tahiti french polynesia iodp expedition 310 implications on reef framework architecture abstract the widespread occurrence of microbialites in the last deglacial reef frameworks 16 6 ka bp implies that the accurate study of their development patterns is of prime importance to unravel the evolution of reef architecture through time and to reconstruct the reef response to sea level variations and environmental changes the present study is based on the sedimentological and chronological analysis 14c ams dating of drill cores obtained during the iodp expedition 310 tahiti sea level on the successive terraces which typify the modern reef slopes from tahiti it provides a comprehensive data base to investigate the microbialite growth patterns i e growth rates and habitats to analyze their roles in reef frameworks and to reconstruct the evolution of the reef framework architecture during sea level rise the last deglacial reefs from tahiti are composed of two distinctive biological communities 1 the coralgal communities including seven assemblages characterized by various growth forms branching robust branching massive tabular and encrusting that form the initial frameworks and 2 the microbial communities developed in the primary cavities of those frameworks a few meters 1 5 to 6 m below the living coral reef surface where they heavily encrusted the coralgal assemblages to form microbialite crusts the dating results demonstrate the occurrence of two distinctive generations of microbialites the reefal microbialites which developed a few hundred years after coralgal communities in shallow water environments whereas the slope microbialites grew a few thousands of years later in significantly deeper water conditions after the demise of coralgal communities the development of microbialites was controlled by the volume and the shape of the primary cavities of the initial reef frameworks determined by the morphology and the packing of coral colonies the most widespread microbialite development occurred in frameworks dominated by branching thin encrusting tabular and robust branching coral colonies which built loose and open frameworks typified by a high porosity 50 in contrast their growth was minimal in compact coral frameworks formed by massive and thick encrusting corals where primary cavities yielded a low porosity 30 and could not host a significant microbialite expansion

three stage evolution of the los angeles basin southern california we propose that an episode of transtension dominated development of the los angeles basin area from 12 to 6 ma following middle miocene transrotation and prior to the modern transpressional regime transtension resulted from the releasing bend of the san gabriel chino hills cristianitos fault which acted as the primary transform boundary in southern california during this episode such an interpretation implies that significant transform motion did not occur on the southern san andreas fault prior to 6 ma and that the gulf of california has opened primarily since 6 ma we propose a three stage model for evolution of the los angeles basin and vicinity within the evolving transform fault system transrotation 18 12 ma transtension 12 6 ma and transpression 6 0 ma timing of these stages correlates with microplate capture events which occurred during conversion from a convergent margin to a transform margin

holocene to pliocene tectonic evolution of the region offshore of the los angeles urban corridor southern california 1 quaternary tectonism in the coastal belt of the los angeles urban corridor is diverse in this paper we report the results of studies of multibeam bathymetry and a network of seismic reflection profiles that have been aimed at deciphering the diverse tectonism and at evaluating the relevance of published explanations of the region s tectonic history rapid uplift subsidence in basins folds and thrusts extensional faulting and strike slip faulting have all been active at one place or another throughout the quaternary period the tectonic strain is reflected in the modern physiography at all scales los angeles la basin has filled from a deep submarine basin to its present condition with sediment impounded behind a large sill formed behind uplifts near the present shoreline newport trough to the south southeast of la basin also accumulated a large volume of sediment but remained at midbathyal depths throughout the period there is little or no evidence of quaternary extensional tectonism in either basin although as much as 6 km of subsidence which mainly occurred by sagging has been recorded in places since the middle miocene the uplifts include folded and thrust faulted terranes in the palos verdes hills and the shelves of santa monica and san pedro bays the uplifted areas have been shortened in a southwest northeast direction by 10 or slightly more and some folds are reflected in the bathymetry two large adjacent midbathyal basins santa monica and san pedro show strong evidence of subsidence and slight west northwest extension 10 during the same time folding was taking place in the uplifts the tectonic boundaries between uplifts and basins are folded normal faulted reverse faulted and strike slip faulted depending on location the rapid quaternary uplift and subsidence along with the filling of la basin have produced a reversal in the regional physiography in the early pliocene la basin was a submarine deep palos verdes and the shelves comprised a northeast basin slope and the present offshore basins and catalina island formed an emergent or shallowly submerged shelf since extensional compressional and lateral strains are all locally in evidence simple notions that this part of southern california underwent a change from miocene transtension to quaternary transpression fail to explain our observations

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

younger dryas sea level and meltwater pulse 1b recorded in barbados reef crest coral acropora palmata the younger dryas climate event occurred during the middle of the last deglacial cycle and is marked by an abrupt shift in the north atlantic polar front almost to its former glacial position trending east to west using high precision and high accuracy u th dated barbados reef crest coral acropora palmata we generate a detailed sea level record from 13 9 to 9000 years before present kyr b p and reconstruct the ice volume response to the younger dryas cooling from the mid allerod 13 9 kyr b p to the end of the younger dryas 11 65 kyr b p rates of sea level rise decreased smoothly from 20 mm yr 1 to 4 mm yr 1 culminating in a 400 year slow stand before accelerating into meltwater pulse 1b mwp 1b the mwp 1b event at barbados is better constrained as beginning by 11 45 kyr b p and ending at 11 1 kyr b p during which time sea level rose 14 2 m and rates of sea level rise reached 40 mm yr 1 we propose that mwp 1b is the direct albeit lagged response of the northern hemisphere ice sheets to the rapid warming marking the end of the younger dryas coinciding with rapid warming in the circum north atlantic region and the polar front shift from its zonal to meridional position 11 65 kyr b p as predicted by glaciological models the ice sheet response to rapid north atlantic warming was lagged by 400 years due to the thermal inertia of large ice sheets the regional circum north atlantic younger dryas climate event is elevated to a global response through sea level changes starting with the global slowdown in sea level rise during the younger dryas and culminating with mwp 1b no meltwater pulses are evident at the initiation of the younger dryas climate event as is often speculated

late quaternary sea level change and evolution of belfast lough northern ireland new offshore evidence and implications for sea level reconstruction the interplay of eustatic and isostatic factors causes complex relative sea level rsl histories particularly in paraglacial settings in this context the past record of rsl is important in understanding ice sheet history earth rheology and resulting glacio isostatic adjustment field data to develop sea level reconstructions are often limited to shallow depths and uncertainty exists as to the veracity of modelled sea level curves we use seismic stratigraphy 39 vibrocores and 26 radiocarbon dates to investigate the deglacial history of belfast lough northern ireland and reconstruct past rsl a typical sequence of till glacimarine and holocene sediments is preserved two sea level lowstands both max 40 m are recorded at c 13 5 and 11 5k cal a bp each is followed by a rapid transgression and subsequent periods of rsl stability the first transgression coincides temporally with a late stage of meltwater pulse 1a and the rsl stability occurred between c 13 0 and c 12 2k cal a bp younger dryas the second still slowstand occurred between c 10 3 and c 11 5k cal a bp our data provide constraints on the direction and timing of rsl change during deglaciation application of the depth of closure concept adds an error term to sea level reconstructions based on seismic stratigraphic reconstructions

comment on younger dryas sea level and meltwater pulse 1b recorded in barbados reefal crest coral acropora palmata by n a abdul et al based on new u th ages of corals drilled offshore barbados abdul et al 2016 have confirmed the existence of the abrupt stratigraphic feature called meltwater pulse 1b mwp 1b which they interpret as being due to a very large and global sea level step change dated at about 11 3 kyr before present approximately 15 m and equivalent to twice the amount of water stored in the present greenland ice sheet this contrasts with the tahiti record in which mwp 1b is essentially absent or very small as carlson and clark 2012 and lambeck et al 2014 also conclude in their recent reviews of deglacial sea levels at the global scale however the evidence provided by abdul et al and their main conclusions are not convincing as they are affected by the following three main problems which may explain the apparent discrepancies problem 1 barbados is located in a subduction zone which was also active throughout the late glacial period furthermore the barbados cores studied by abdul et al were drilled on both sides of the extension of a tectonic feature identified at the southern tip of barbados south point as underlined by several studies of the barbados stratigraphy problem 2 fossil samples of acropora palmata may not be reliable sea level markers during rapid and large sea level rises indeed the asexual reproduction strategy of this species may not be optimal to keep up when the water depth is increasing very rapidly this may in part explain why the living depth of a palmata at barbados was significantly greater than 5 m during some periods of the last deglaciation notably between 14 5 and 14 kyr b p and possibly between 14 and 11 5 kyr b p problem 3 the slow glacio isostatic adjustment and the rapid responses due to gravitational changes of ice and water masses complicate the interpretation of individual relative sea level rsl records at specific locations therefore the barbados and tahiti record cannot be compared directly in terms of absolute sea level values as done by abdul et al in addition different glaciohydroisostatic adjustments at the two sites may also have contributed to the observed discrepancy between their deglacial rsl records

middle tertiary extension recorded by lacustrine fan delta deposits plush ranch basin western transverse ranges california abstract the plush ranch formation upper oligocene and lower miocene consists of more than 1800 m of nonmarine sedimentary and volcanic rocks that record the history of an extensional basin referred to here as the plush ranch basin distinctive depositional facies provenance and sediment transport directions along each basin margin suggest an asymmetric basin shape that is consistent with a half graben origin the northern basin margin consists of sandstone dominated alluvial plain deposits 0 1 1 5 m thick normally graded lenticular sandstone beds small deltaic sequences 1 2 m thick were formed where these alluvial systems flowed southward into a lake lenses of massive boulder rich granitic breccia that represent rockslide deposits derived from a nearby northern granitic provenance nterfinger with the alluvial plain facies in contrast to the northern margin the southern basin margin is represented by coarse grained fan delta deposits matrix and clast supported lenticular conglomerate beds 0 2 5 m thick with interbedded trough cross bedded pebbly sandstone represent braided stream and flood flow and or noncohesive debris flow deposits of alluvial fans that drained a highland area to the south the alluvial fan deposits interfinger to the north with several types of subaqueous sediment gravity flow facies including turbidite sandstone beds and matrix supported debris flow conglomerate each of the basin margin depositional systems grades basinward and to the east into lacustrine deposits that include organic rich dark shale evaporite and limestone the lacustrine deposits represent the central and eastern parts of the plush ranch basin which received little coarse siliciclastic sediment basalt deposits that are at least 50 m thick in the west and thicken eastward are interbedded mainly with the lacustrine facies the southern margin of the plush ranch basin formed along a north dipping normal slip fault along which dip separation increased toward the southwest the northern margin developed on the tilted hanging wall block of this fault this fault was later reactivated in post middle miocene time as the present left lateral strike slip big pine fault the plush ranch is one of several extensional and transtensional basins that formed in southern california and western arizona about 25 20 ma as a response to the change from a convergent to a strikeslip tectonic regime along western north america

a data calibrated distribution of deglacial chronologies for the north american ice complex from glaciological modeling article i nfo past deglacial ice sheet reconstructions have generally relied upon discipline specific constraints with no at tention given to the determination of objective confidence intervals reconstructions based on geophysical inversion of relative sea level rsl data have the advantage of large sets of proxy data but lack ice mechanical constraints conversely reconstructions based on dynamical ice sheet models are glaciologically self consistent but depend on poorly constrained climate forcings and sub glacial processes as an example of a much better constrained methodology that computes explicit error bars we present a dis tribution of high resolution glaciologically self consistent deglacial histories for the north american ice com plex calibrated against a large set of rsl marine limit and geodetic data the history is derived from ensemble based analyses using the 3d mun glacial systems model and a high resolution ice margin chronol ogy derived from geological and geomorphological observations isostatic response is computed with the vm5a viscosity structure bayesian calibration of the model is carried out using markov chain monte carlo methods in combination with artificial neural networks trained to the model results the calibration provides a posterior distribution for model parameters and thereby modeled glacial histories given the observational data sets that takes data uncertainty into account final ensemble results also account for fits between com puted and observed strandlines and marine limits given the model including choice of calibration parameters input and constraint data sets and vm5a earth rhe ology we find the north american contribution to mwp1a was likely between 9 4 and 13 2 m eustatic over a 500 year interval this is more than half of the total 16 to 26 m meltwater pulse over 500 to 700 years with lower values being more probable indicated by the barbados coral record fairbanks 1989 peltier and fairbanks 2006 if one assumes a 5 meter living range for the acropora palmata coral 20 ka ice volume for north america was likely 70 1 2 0 m eustatic or about 60 of the total contribution to eustatic sea level change we suspect that the potentially most critical unquantified uncertainties in our analyses are those related to model structure especially climate forcing deglacial ice margin chronology and earth rheology

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

a model for neogene crustal rotations transtension and transpression in southern california two episodes of crustal rotation have occurred in the regions of southern california and the mojave desert since the beginning of miocene time an early miocene episode of clockwise crustal rotation is associated with widespread north south to north northeast south southwest crustal extension throughout southeast california and western arizona this episode is apparently related to changing subduction parameters of the farallon plate a middle miocene and later episode of clockwise rotation in the transverse ranges and bordering areas is related to shear between the pacific and north american plates in both episodes clockwise crustal rotations first occur in a deforming zone which has a component of extension across its trend and shear along its trend the effects of extension are most pronounced in the earlier episode but clear in the later one also the pacific north american deforming zone began contracting in width during pliocene time but clockwise rotations continued and are probably in progress today

formation of the yangtze shoal in response to the post glacial transgression of the paleo yangtze changjiang estuary china abstract the yangtze shoal lies east of the yangtze changjiang river estuary china at water depths of 25 55 m and is one of the largest subaqueous sheet like sand banks in the world previous studies have not reached a consensus regarding its origin and timing of formation mainly due to the scarcity of coring and high resolution seismic profiling in the shoal we recovered a 70 20 m long sediment core cre 1402 through the sand shoal and acquired 1586 km of high resolution shallow seismic profiles across the estuary and shoal we conducted systematic analyses of the core including its sedimentary characteristics down core changes in benthic foraminiferal assemblages and 14c and optically stimulated luminescence osl dating we also analyzed the seismic stratigraphy and integrated these results with data from other previously well studied cores onshore and offshore of the yangtze river mouth our results indicate that the stratigraphic architecture in the paleo yangtze estuary i e the area from the present day delta plain to the subaqueous delta and yangtze shoal was controlled mainly by changes in sea level during the post glacial transgression the post 14 ka sedimentary successions in the paleo estuary rest unconformably on fluvial or coastal deposits that formed mainly before mis 1 and are separated by three distinctive bounding surfaces corresponding to mwp 1a mwp 1b or the rapid sea level rise at ca 11 5 ka shortly after the younger dryas cold period and the 8 2 ka event respectively and the maximum marine flooding surface mfs the depositional unit of the yangtze shoal ranges in thickness from 6 to 32 m the shoal exhibits large scale sw dipping generally 0 5 2 foresets with local cross cutting of foresets which are composed mainly of very fine to medium grained sands the shoal is underlain by muddy intertidal to subtidal flat deposits that formed during the younger dryas with an erosional surface corresponding to mwp 1b or the rapid sea level rise at ca 11 5 ka between these and the shoal deposits the yangtze shoal came into being mainly between ca 11 5 and 7 0 ka in the form of tidal sand ridges actively moving southwestwards under intense and reciprocal tidal currents on a tidal shelf the tidal sand ridges have evolved into sheet like tidal sand banks with relatively low relief as a result of tidal remobilization under rotary tidal currents since ca 7 0 ka when the mfs formed therefore the yangtze shoal can be considered to comprise quasi active tidal sand banks

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

evolution of ocean temperature and ice volume through the mid pleistocene climate transition earth s climate underwent a fundamental change between 1250 and 700 thousand years ago the mid pleistocene transition mpt when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing over this time an increase occurred in the amplitude of change of deep ocean foraminiferal oxygen isotopic ratios traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep ocean temperature we have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios our results suggest that the mpt was initiated by an abrupt increase in antarctic ice volume 900 thousand years ago we see no evidence of a pattern of gradual cooling but near freezing temperatures occur at every glacial maximum

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

pliocene transpressional modification of depositional basins by convergent thrusting adjacent to the big bend of the san andreas fault an example from lockwood valley southern california 1 the big bend of the san andreas fault in the western transverse ranges of southern california is a left stepping flexure in the dextral fault system and has long been recognized as a zone of relatively high transpression compared to adjacent regions the lockwood valley region just south of the big bend underwent a profound change in early pliocene time 5 ma from basin deposition to contraction accompanied by widespread folding and thrusting this change followed the recently determined initiation of opening of the northern gulf of california and movement along the southern san andreas fault at about 6 1 ma with the concomitant formation of the big bend lockwood valley occupies a 6 km wide fault bounded structural basin in which converging blocks of paleoproterozoic and cretaceous crystalline basement and upper oligocene and lower miocene sedimentary rocks plush ranch formation were thrust over miocene and pliocene basin fill sedimentary rocks in ascending order caliente formation lockwood clay and quatal formation all the pre quatal sedimentary rocks and most of the pliocene quatal formation were deposited during a mid tertiary period of regional transtension in a crustal block that underwent little clockwise vertical axis rotation as compared to crustal blocks to the south ensuing pliocene and quaternary transpression in the big bend region began during deposition of the poorly dated quatal formation and was marked by four converging thrust systems which decreased the areal extent of the sedimentary basin and formed the present lockwood valley structural basin none of the thrusts appears presently active estimated shortening across the center of the basin was about 30 percent the formerly defined eastern big pine fault now interpreted to be two separate oppositely directed contractional reverse or thrust faults marks the northwestern structural boundary of lockwood valley the complex geometry of the lockwood valley basin is similar to other tertiary structural basins in southern california such those that underlie cuyama valley the ridge basin and the east ventura basin

barbados based estimate of ice volume at last glacial maximum affected by subducted plate coral records from the barbados have been used to infer that due to ice expansion sea level was 120 m lower than today during the last glacial maximum a 3d simulation of the mantle in this region suggests these estimates were biased by the presence of a subducted slab and indicates the sea level difference was closer to 130 m

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

sea level fingerprinting as a direct test for the source of global meltwater pulse ia the ice reservoir that served as the source for the meltwater pulse ia remains enigmatic and controversial we show that each of the melting scenarios that have been proposed for the event produces a distinct variation or fingerprint in the global distribution of meltwater we compare sea level fingerprints associated with various melting scenarios to existing sea level records from barbados and the sunda shelf and conclude that the southern laurentide ice sheet could not have been the sole source of the meltwater pulse whereas a substantial contribution from the antarctic ice sheet is consistent with these records

geomorphic indicators of active fold growth south mountain oak ridge anticline ventura basin southern california south mountain oak ridge near ventura california is an asymmetric anticlinal uplift forming at the present time above the active buried oak ridge reverse fault shortening along the oak ridge fault accumulated largely in quaternary time and is responsible for the growth and present topography of the westernmost 15 km of the ridge during the past 0 5 m y tectonic geomorphic analysis using several indices of active tectonics provides information concerning fold growth stream gradient indices are relatively high in the northern eroded fold scarp of the ridge a pattern consistent with the existence of active rapid slip on the oak ridge fault mountain front sinuosity along the northern slope of the anticlinal ridge roughly decreases from 2 to 1 toward the westernmost 10 km of observed surface folding valley floor width to valley height ratios along the northern flank of the ridge generally decrease westward from 1 5 to 0 5 values of the hypsometric integral along the northern flank increase significantly from 0 35 to 0 4 maximum 0 55 from east to west drainage density varies from 4 to 6 km km2 along both flanks of the south mountain oak ridge anticline entrenchment of streams into the southern backlimb of the fold along the westernmost 9 km of the structure decreases from 20 m to 1 m from east to west apparent backlimb rotation as measured by dip of strata along the westernmost 7 km of the fold decreases from east to west from 35 to 20 fold growth of the south mountain oak ridge anticline occurred during the past 0 5 ma following deposition of the saugus formation lateral and vertical fold growth were likely produced by westward decrease in fault slip along the buried oak ridge fault

final deglaciation of the scandinavian ice sheet and implications for the holocene global sea level budget abstract the last deglaciation of the scandinavian ice sheet sis from 21 000 to 13 000 yr ago is well constrained by several hundred 10be and 14c ages the subsequent retreat history however is established primarily from minimum limiting 14c ages and incomplete baltic sea varve records leaving a substantial fraction of final sis retreat history poorly constrained here we develop a high resolution chronology for the final deglaciation of the sis based on 79 10be cosmogenic exposure dates sampled along three transects spanning southern to northern sweden and finland combining this new chronology with existing 10be ages on deglaciation since the last glacial maximum shows that rates of sis margin retreat were strongly influenced by deglacial millennial scale climate variability and its effect on surface mass balance with regional modulation of retreat associated with dynamical controls ice volume estimates constrained by our new chronology suggest that the sis contributed 8 m sea level equivalent to global sea level rise between 14 5 ka and 10 ka final deglaciation was largely complete by 10 5 ka with highest rates of sea level rise occurring during the bolling allerod a 50 decrease during the younger dryas and a rapid increase during the early holocene combining our sis volume estimates with estimated contributions from other remaining northern hemisphere ice sheets suggests that the antarctic ice sheet ais contributed 14 4 5 9 m to global sea level rise since 13 ka this new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea level rise was lost from the ais during the last deglaciation

large scale quaternary detachments in ventura basin southern california the ventura basin is an east north east trending trough in the california transverse ranges which records major quaternary detachment faulting at three levels the earliest thrusting occurred along weak siltstone interbeds in a sequence dominated by competent basin plain turbidite sandstone because sedimentation continued during thrusting the age rate and direction of thrusting can be worked out faulting began 1 3 m y ago and ceased 0 65 m y ago with a maximum slip rate of 2 8 mm yr to the southeast the fault set moved up a 45 ramp and ended as a blind thrust the ramp had topographic expression on the seafloor diverting turbidites around the ramp and preserving ash beds along with other hemipelagic sediments on its crest following the end of deposition 0 2 m y ago the competent basin plain turbidites underwent flexural slip folding over an incompetent miocene sequence dominated by shale underlying competent paleogene strata were not folded the south flank of the ventura avenue anticline tilted at 3 4 rad yr the anticlinal crest rose at a rate of 15 16 mm yr decelerating to 4 3 5 2 mm yr and the anticline and an adjacent syncline shortened at a rate of 20 mm yr the high rate of folding in the ventura avenue oil field resulted in overpressured sandstone reservoirs and oil water interfaces which have not had time to reach gravity equilibrium the red mountain san cayetano and santa susana faults mark the surface expression of a seismically active midcrustal detachment which produced convergence across the ventura basin at rates as high as 23 mm yr total convergence across the eastern san cayetano fault near fillmore is 11 600 2000 m in the last million years

antarctic ice dynamics amplified by northern hemisphere sea level forcing sea level rise due to ice loss in the northern hemisphere in response to insolation and greenhouse gas forcing is thought to have caused grounding line retreat of marine based sectors of the antarctic ice sheet ais 1 3 such interhemispheric sea level forcing may explain the synchronous evolution of global ice sheets over ice age cycles recent studies that indicate that the ais experienced substantial millennial scale variability during and after the last deglaciation4 7 roughly 20 000 to 9 000 years ago provide further evidence of this sea level forcing however global sea level change as a result of mass loss from ice sheets is strongly nonuniform owing to gravitational deformational and earth rotational effects8 suggesting that the response of ais grounding lines to northern hemisphere sea level forcing is more complicated than previously modelled1 2 6 here using an ice sheet model coupled to a global sea level model we show that ais dynamics are amplified by northern hemisphere sea level forcing as a result of this interhemispheric interaction a large or rapid northern hemisphere sea level forcing enhances grounding line advance and associated mass gain of the ais during glaciation and grounding line retreat and mass loss during deglaciation relative to models without these interactions the inclusion of northern hemisphere sea level forcing in our model increases the volume of the ais during the last glacial maximum about 26 000 to 20 000 years ago triggers an earlier retreat of the grounding line and leads to millennial scale variability throughout the last deglaciation these findings are consistent with geologic reconstructions of the extent of the ais during the last glacial maximum and subsequent ice sheet retreat and with relative sea level change in antarctica3 7 9 10

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

reply to comment by e bard et al on younger dryas sea level and meltwater pulse 1b recorded in barbados reef crest coral acropora palmata by n a abdul et al abdul et al 2016 presented a detailed record of sea level at barbados 13 9 9 kyr b p tightly constraining the timing and amplitude during the younger dryas and meltwater pulse 1b mwp 1b based on u th dated reef crest coral species acropora palmata the younger dryas slow stand and the large 14 meter rapid sea level jump are not resolved in the tahiti record tahiti sea level estimates are remarkably close to the barbados sea level curve between 13 9 and 11 6 kyr but fall below the barbados sea level curve for a few thousand years following mwp 1b by 9 kyr the tahiti sea level estimates again converge with the barbados sea level curve abdul et al 2016 concluded that tahiti reefs at the core sites did not keep up with intervals of rapidly rising sea level during mwp 1b we counter bard et al 2016 by showing 1 there is no evidence for a hypothetical fault in oistins bay affecting one of the barbados coring locations 2 that the authors confuse the rare occurrences of a palmata at depths 5 meters with the thickets of a palmata fronds representing the reef crest facies and 3 that uncertainties in depth habitat proxies largely account for differences in barbados and tahiti sea level differences curves with a palmata providing the most faithful proxy given the range in tahiti paleo depth uncertainties at the cored sites the most parsimonious explanation remains that tahiti coralgal ridges did not keep up with the sea level rise of mwp 1b

quaternary flake tectonics of the california transverse ranges p residual studies suggest that the pacific american plate boundary in the upper mantle lies in the central mojave desert northeast of its crustal position at the san andreas fault focal mechanisms of some relatively deep microearthquakes suggest a flattening with depth of north dipping thrust faults resulting in a mid crustal detachment in which the central transverse ranges move south relative to the mantle this makes sense geologically if the central transverse ranges and western mojave desert are considered as tectonic flakes of brittle crystalline rocks underlain by ductile pelona schist or catalina schist which makes up the zone of decollement such ductile schists would occur today at depths comparable to those at which they were metamorphosed the detachment breaks through to the surface at the point dume malibu coast fault zone and the red mountain san cayetano santa susana sierra madre cucamonga fault zone the latter coinciding with the southern edge of the palmdale bulge the transverse ranges flake now moves west northwest relative to the western mojave flake south southwest relative to the pacific plate and northwest relative to the great valley sierra nevada the mantle boundary may rejoin the san andreas fault north of a southwest trending zone of high seismicity in the tehachapi mountains which may be produced by convergence the age of the present tectonic system may be the same as the age of the break through thrust faults these are probably no older than 2 m y and may be even younger

wind induced oscillator dynamics in the black sea revealed by lagrangian drifters 1 lagrangian drifter observations of the black sea circulation between 2002 and 2003 show six transitions between two meta stable states representing single gyre structures centered in either the western or eastern sub basin of the black sea respectively the major mechanisms driving such an oscillator dynamics are ekman pumping for the eastern sub basin and most likely a resonance excitation for the western sub basin the sea strongly amplifies the wind responses of 120 day periodicity data analysis demonstrates that two gyre structure knipovich spectacles was a transient between the states residence time for the sea to occupy either state is mainly determined by the instability of the gyres wind variability and probably variations in the pycnocline this behavior is a manifestation of a bimodal dynamical regime which affects the long term climatic large scale transport and mixing of bio geochemical substances