genesis of late pleistocene cross valley moraine ridges south central ulster northern ireland four genetic varieties of ice marginal cross valley moraine ridge have been identified in south central ulster northern ireland type i ridges are flat topped composed of stratified water lain sediments and formed by coalescence of a series of supraaquatic deltas type ii ridges are sharp crested composed of stratified water lain sediments and formed by coalescence of a series of subaquatic deltas type iii ridges show mixed morphological and sedimentological characteristics of type i and ii ridges type iv ridges are sharp crested or hummocky composed of poorly sorted and poorly stratified water lain sediments and formed by coalescence of a series of subaquatic sediment gravity flow cones field evidence indicates that cross valley moraine ridges in south central ulster were deposited in proglacial lacustrine environments ridge type depended principally on 1 the nature of the proglacial bedrock slope 2 the manner in which meltwater entered the proglacial zone and 3 ice sheet behaviour during deglaciation particularly within the ice sheet terminus zone

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

sedimentation in a large lake a reinterpretation of the late pleistocene stratigraphy at scarborough bluffs ontario canada a lithofacies code developed for diamicts emphasizes facies variability in the classic upper pleistocene glaciogenic sequence at scarborough bluffs ontario canada lithological breaks along the bluffs are traditionally assigned to incursions of grounded ice margins and to interstadial lakes formed during ice retreat during the early and middle wisconsin detailed sedimentological logging through three diamict units previously formalized as sunnybrook seminary and meadowcliffe tills and intervening sandy lithofacies shows absence of glaciotectonic structures and diamicts associated with grounded glacier ice traction current activity during diamict accumulation postdepositional resedimentation of diamicts into topographic lows accompanied by turbidite activity a subaqueous deltaic origin for intervening sandy lithofacies and loaded transitional and interbedded contacts between sand and diamict the scarborough bluffs sequence may be the preserved bottom stratigraphy of a large lake the bottom stratigraphy results from repeated basinward progradation of deltaic sandy lithofacies over glaciolacustrine diamicts deposited below floating ice whether ice shelf ramp bergs or lake ice a facies model is presented for glaciolacustrine diamict deposition on the floors of enlarged pleistocene lakes trapping substantial volumes of fine grained suspended sediment

geomorphic evidence for active and inactive phases of late devensian ice in north central ireland abstract in the clogher valley north central ireland subglacial and proglacial landforms provide evidence for phases of active and inactive subglacial and ice marginal processes during the late devensian weichselian glaciation 22 13 kyr bp patterns of subglacial rogen moraines and drumlins record east to west ice flow along the valley axis during maximal ice stages eskers superimposed upon the rogen moraines and drumlins record later west to east ice flow and mark the first stages of ice retreat areas of large ice marginal non aligned ridges and mounds are separated by more extensive areas in which no deglacial landforms or sediments are present the non aligned ridges and mounds do not show a dominant directional signature have intricate basal outlines steep slopes and high relief

ultramafic rocks of a fracture zone ophiolite north cascades washington abstract the ingalls complex was deformed in a late jurassic oceanic fracture zone an unusually diverse group of ultramafic tectonites comprise three units in this ophiolite unit 1 consists mostly of poorly to moderately foliated harzburgite and dunite characterized by porphyroclastic textures irregular shaped and tabular dunite bodies probably represent intrusive bodies or residues of partial melting voluminous unit 2 consists mostly of poorly to strongly foliated iherzolite and clinopyroxene bearing harzburgite plagioclase peridotite is present locally olivine and enstatite generally define equigranular mosaics or weakly porphyroclastic textures clinopyroxene however in some samples displays only weak deformation compositional zoning simple growth twins and interstitial commonly poikilitic texture clinopyroxene and plagioclase in these samples probably formed from a melt after recrystallization of olivine and enstatite indicating that these iherzolites are impregnated peridotites other iherzolites and clinopyroxene bearing harzburgites may represent weakly depleted mantle pods of metagabbroic gneiss within unit 2 probably are small intrusions that were deformed as they cooled unit 3 represents a major high temperature 700 900 c shear zone that separates units 1 and 2 and consists of strongly foliated commonly mylonitic iherzolites and hornblende peridotites the latter are the most strongly foliated ultramafites and olivine in them records stresses as high as 275 mpa the abundance of hornblende implies a genetic relationship between mylonitization and the hydration and metasomatism necessary to form such rocks from iherzolites mineral chemistry and geothermometry are typical of mantle tectonites in many ophiolites and oceanic fracture zones there is a particularly strong similarity between the spinels in the ingalls complex and the spinels from the owen and vema fracture zones hornblende in unit 3 ranges from edenite to edenitic hornblende calculated temperatures from cpx opx pairs in unit 2 range from 950 to 1000 c these data are best explained by horizontal and vertical displacements in oceanic fracture zones which may juxtapose lithosphere formed at different structural levels and with different petrologic histories unit 1 represents a block of upper mantle which probably experienced convective upwelling and partial melting beneath a spreading ridge near its intersection with a fracture zone during convective upwelling at least parts of the upper mantle represented by unit 2 were impregnated by a melt the impregnated iherzolite may be accounted for by the edge effect at a fracture zone or reduced melt production at a fracture zone due to ribbon spreading the mylonite zone of unit 3 reworks iherzolites and harzburgites which were originally part of the block represented by unit 2 and probably records deformation in the active segment of the fracture zone these observations document the complexities that may occur in ultramafic rocks within oceanic fracture zones they also suggest that impregnation metasomatism and high stresses are important in these zones

late holocene environmental change and the anthropization of the highlands of santo antao island cabo verde abstract cabo verde was the first tropical archipelago colonized by europeans historians have suggested that the first colonizers initiated archipelago wide ecosystem degradation loss of vegetation cover and erosion however the human environment interactions that led to the archipelago s current environmental status remain poorly understood here we report the first palaeoecological study of past vegetation change and disturbance regimes for cabo verde we present a 2130 yr old sediment sequence from a volcanic caldera cova de paul located at 1200 m asl on santo antao island for which we analyzed fossil pollen non pollen palynomorphs npps charcoal silica bodies and grain size distribution our analyses do not show evidence of the presence of temperate tropical or subtropical forests growing on the summits of santo antao in pre human times the pollen record shows that scrubland and grasslands dominated the highlands and underwent compositional changes ca 1850 and 1300 cal yr bp these shifts overlap with erosion phases and are linked to intensified seasonality steady rates of sedimentation marked the period 1230 to ca 350 cal yr bp but an increase in charcoal concentrations indicate a drying phase increases in regional and local fire peaks of coprophilous fungi and the presence of new world crop pollen zea mays are interpreted as the onset of portuguese settlement of the highlands after 450 bp sustained erosion between ca 350 and 100 cal yr bp indicate soil degradation and the pollen record shows the increase in introduced herbaceous taxa rosaceae centaurea verbenaceae and exotic tree taxa e g pinus while shifting abundances of coprophilous fungi indicate changes in land use the record shows stabilization of soils in the last century due to recent afforestation of the highlands further palaeoecological studies have the potential to provide further detail of the long term dynamics of cabo verde ecosystems and to inform conservation initiatives

alpine ophiolites product of low degree mantle melting in a mesozoic transcurrent rift zone abstract the alpine ophiolites and their original sedimentary cover upper jurassic radiolarite limestone with ophiolite breccia occur as dismembered tectonic slices often inverted by alpine tectonics or olistoliths among the calc schists cretaceous original petrologic features of the ophiolites are largely masked by the alpine metamorphism but are discernible by the relic mineral chemistry and petrographic reconstruction the residual peridotite is generally plagioclase lherzolite resembling those from oceanic fracture zones but spinel lherzolite is present at davos switzerland and peas france the latter is characterized by higher na 2 o 1 6 of clinopyroxene and lower cr 2 o 3 8 of spinel than the former 30 respectively and resembles subcontinental lherzolites geologic evidence indicates that these two lherzolites were together exposed on the jurassic ocean floor the mafic ultramafic cumulates are of plagioclase type characterized by the scarcity of orthopyroxene and high tio 2 avg 0 8 of clinopyroxene the basaltic volcanics are alkalic rather than tholeiitic in respect to their relic clinopyroxene which is as rich in tio 2 and na 7 o as that in hawaiian alkali basalt the alpine ophiolite association of lherzolitic residual peridotite plagioclase type cumulates and alkalic basalt is reasonable as cogenetic products of low degree partial melting in the mantle geologic and petrologic features of the alpine ophiolites are consistent with a geotectonic model postulating the generation of the alpine ophiolites in an early mesozoic rift zone cut by many transform faults

geotectonic significance of gneissic amphibolites from the vema fracture zone equatorial mid atlantic ridge a large collection of gneissic amphibolites was recovered by two close dredge hauls from the deepest part of the north facing slope of the transverse ridge forming the south wall of the vema fracture zone serpentinites and various types of gabbroic rocks ranging from undeformed slightly uralitized gabbros and norites to flaser and mylonitic gabbros were associated with the gneissic amphibolites in the shallowest of the dredge hauls petrological studies indicate that the amphibolites were derived from similar gabbroic rocks that reequilibrated under stress in the conditions of the amphibolite facies on the other hand the associated meta gabbros display sequences of secondary minerals indicating complex cooling and cataclastic histories without reaching metamorphic equilibrium we tentatively suggest that the gneissic amphibolites and associated metagabbros formed in a vertical shear zone generated in oceanic layer 3 by tectonism associated with the vema fracture zone hydrothermal circulation of seawater along the highly permeable shear zone was activated by magmatic intrusions k ar dating suggests within relatively large analytical uncertainties that the amphibolite metamorphism took place 10 m y ago i e at a time when the dredging sites were located in the vicinity of the spreading center

human responses to middle holocene climate change on california s channel islands abstract high resolution archaeological and paleoenvironmental records from california s channel islands provide a unique opportunity to examine potential relationships between climatically induced environmental changes and prehistoric human behavioral responses available climate records in western north america 7 3 8 ka indicate a severe dry interval between 6 3 and 4 8 ka embedded within a generally warm and dry middle holocene very dry conditions in western north america between 6 3 and 4 8 ka correlate with cold to moderate sea surface temperatures sst along the southern california coast evident in ocean drilling program odp core 893a b santa barbara basin an episode of inferred high marine productivity between 6 3 and 5 8 ka corresponds with the coldest estimated ssts of the middle holocene otherwise marked by warm low productivity marine conditions 7 5 3 8 ka the impact of this severe aridity on humans was different between the northern and southern channel islands apparently related to degree of island isolation size and productivity of islands relative to population fresh water availability and on going social relationships between island and continental populations northern channel islanders seem to have been largely unaffected by this severe arid phase in contrast cultural changes on the southern channel islands were likely influenced by the climatically induced environmental changes we suggest that productive marine conditions coupled with a dry terrestrial climate between 6 3 and 5 8 ka stimulated early village development and intensified fishing on the more remote southern islands contact with people on the adjacent southern california coast increased during this time with increased participation in a down the line trade network extending into the western great basin and central oregon genetic similarities between middle holocene burial populations on the southern channel islands and modern california uto aztecan populations suggest middle holocene movement of people at this time from southern california desert environs westward to the southern islands a migration perhaps stimulated by increased continental aridity

high resolution environmental magnetic study of a holocene sedimentary record from zaca lake california mineral magnetic studies of holocene lake sediments recovered from zaca lake in coastal southern california have yielded a 3000 year high resolution record of terrestrial hydrologic variability an

ultramafic and mafic rocks from the garret transform fault near 13 30 s on the east pacific rise igneous petrology serpentinized peridotites metagabbros and fresh basaltic rocks were dredged from the garret transform fault near 13 s on the east pacific rise two dredge hauls taken on the northern wall from about 3100 3600 m consisted of aphyric and picritic basalts while peridotites gabbros and moderately phyric basalts were recovered in a single dredge located near the deepest part 4616 4820 m of the transform valley well preserved igneous textures and mineralogical assemblages enable us to differentiate between tectonites including harzburgites and clinopyroxene bearing harzburgites and cumulates consisting of plagioclase dunite troctolites olivine gabbros and ilmenite gabbros the harzburgites are likely to represent deep seated peridotites left after extraction of basaltic melt during upper mantle partial melting of a lherzolite the ultramafic cumulates underwent some deformation and show textural and mineralogical evidences which suggest formation at a minimum depth corresponding to the very lower crust it is also inferred that the composition of the coexisting liquid along with early cumulus crystals has a ratio mg mg fe2 of 0 7 high cao na2o ratios and a low ni content about 150 ppm when compared to similar rock types from atlantic fracture zones subsequent uplift during rifting of the oceanic lithosphere enhanced plastic deformation subsolidus recrystallization and retrogressive metamorphism of the gabbros and the ultramafics

mylonitic ductile shear zones within tectonites and cumulates as evidence for an oceanic transform fault in the antalya ophiolite s w turkey summary in the coastal ophiolite belt of antalya especially in the massifs of adrasan and cirali tekirova tectonites and cumulates have preserved their primary structures tectonites display a first high temperature low deviatoric stress deformation s1 linked to the diapiric uplift of the asthenosphere below an east west orientated spreading centre a second mylonitic deformation produced under high deviatoric stress and lower temperature conditions produced shear zones of millimetric to kilometric scale throughout the tectonites and even in the cumulates their mean orientation n 150 e is near to perpendicular to the ridge axis and the associated lineation indicates horizontal essentially sinistral strike slip displacement this deformation must have taken place during the final crystallisation of the cumulates as indicated by its relationship to intrusive gabbroic dykelets representing residual liquids of the cumulates the s2 deformation is attributed to a transform fault situated sw of the coastal complexes later tectonic events include thrusting and wrench faulting again sinistral in a north south trending direction

santa barbara basin diatom and silicoflagellate response to global climate anomalies during the past 2200 years santa barbara basin sbb diatom and silicoflagellate assemblages are quantified from a box core record spanning ad 1940 2001 and an ocean drilling program hole 893a record from 220 bc to ad 1880 the combined relative abundance of the diatoms fragilariopsis doliolus and nitzschia interrupteseriata from continuous two year sampling intervals in the box core varies with sea surface temperature sst suggesting its utility in sst reconstruction the assemblage data from the odp 893a record indicate a broad interval of generally cooler ssts between ad 800 and 1350 which corresponds to the medieval climate anomaly mca a period of generally warmer temperatures across other regions of the northern hemisphere the assemblages also indicate an interval of generally warmer ssts between ad 1400 and 1800 a period of otherwise global cooling referred to as the little ice age lia the changes in assemblages of diatoms and silicoflagellates support the hypothesis that the widespread droughts of the medieval climate anomaly in the western us were associated with cooler eastern north pacific sst the box core assemblages have higher percentages of tropical and subtropical compared to temperate and subpolar species than the odp samples reflecting a response of phytoplankton communities to an unusual 20th century warming pseudonitzschia australis a diatom linked with domoic acid production begins to become more common 3 of the diatom assemblage in the box core only after ad 1985 suggesting a link to anthropogenic activity

magmatic metasomatism in peridotites from the zambales ophiolite evidence for variable amounts of melt induced metasomatism in upper mantle peridotites has been observed in the ultramafic section of the zambales range ophiolite luzon republic of the philippines these peridotites are locally cut by mafic dikes that in some places visibly ooze into the host peridotite the mafic silicate magma invaded the peridotite along grain boundaries and crystallized as poikilitic plagioclase and clinopyroxene compositional data indicate that the mafic material reacted with the peridotite mineral compositions in the mafic dikes are distinct from those in the surrounding peridotite the compositions of residual olivine and orthopyroxene in the peridotite change with the amount of mafic magma within the peridotite fe mg exchange predominates the residual olivine and orthopyroxene in the peridotite are enriched in fe large relative enrichments in other magmaphilic elements na ti at are also evident mafic liquid in transit through the upper mantle may act as a metasomatic agent locally enriching the peridotite through which it passes and producing small scale compositional differences in rocks that otherwise have remarkably uniform compositions

igneous petrogenesis of the yakuno ophiolite japan in the context of the diversity of ophiolites an ophiolite complex includes three major members basaltic volcanics mafic ultramafic cumulates and residual peridotite from the aspect of igneous petrology three distinct types are recognized among the associations of the three members liguria type alkalic basalt plagioclase type cumulates and lherzolite yakuno type high alumina tholeiite clinopyroxene type cumulates and clinopyroxene bearing harzburgite papua type low alumina tholeiite orthopyroxene type cumulates and clinopyroxene free harzburgite in the light of recent experimental studies the three types represent cogenetic complementary products of low 30 degrees of partial melting in the lherzolitic source mantle respectively the cumulates of the yakuno ophiolite show structural and chemical continuity to the underlying residual peridotite and were recrystallized at high pressures 5 10 kb they originated in a deep soft floored magma chamber directly overlying the partially melted residual harzburgite from which the magma was extracted the three members of the yakuno ophiolite were cogenetically formed through a magmatic event induced by a moderate degree of partial melting in the mantle

paleoclimatic interpretations of meadow sediment and pollen stratigraphies from california a comparison of sediment stratigraphies from nine meadow cores in the sierra nevada california with fossil pollen reconstructions of paleoclimates shows excellent correlation between these parameters and confirms the results of recent paleoclimatic models colluvium and alluvium dominate early holocene sedimentary deposits and undoubtedly originated from greater erosion on dry basin side slopes fossil pollen suggests that species characteristic of dry microclimates flourished the transition to peats after 4 5 ka is concurrent with increases in pollen of plants that require abundant soil moisture during the dry summer these results confirm the importance of analysis of the physical stratigraphy of holocene deposits in pollen based reconstructions

a tectonic model for ridge transform ridge plate boundaries implications for the structure of oceanic lithosphere abstract the first order geologic and morphologic relationships at along and proximal to ridge transform ridge plate boundaries are used to construct an empirical and speculative tectonic model the distinctive but variable morphotectonic fabric and crustal structure of the transform domain are the product of a tectonic continuum that ranges from very slow rates of strain associated with very thick edges of lithosphere slowly slipping ridge transfrom ridge plate boundaries to extremely high rates of strain associated with very thin edges of lithosphere fast slipping ridge transform ridge plate boundaries the geometry of a ridge transform intersection necessitates the juxtaposition of a relatively cold thick edge of lithosphere against the truncated end of an accreting plate boundary the cold face of lithosphere cools the adjacent wedge of asthenosphere rising beneath the axis of accretion and restricts the amount of partial melting thus attenuating the volume of basaltic melt segregated from the asthenosphere per unit time the shallow level manifestation of this cold edge effect is a thinner oceanic crust at depth the evolving lithosphere thickens rapidly as the cold edge is approached creating changes in the properties of the young lithosphere and forming a weld of upper mantle material against the cold edge of truncating lithosphere the ridge transform weld of upper mantle material creates a shear couple in the lithosphere underlying the intersection resulting in the progressive reorientation of the maximum tensile stress from normal to the ridge axis at some distance from the ridge transform intersection to an oblique angle near the boundary the brittle carapace of oceanic crust that overlies the mantle weld will deform accordingly with the development of oblique dip slip faults the model predicts that the geologic expressions of this cold boundary effect will become more dramatic with increasing thickness of the truncating edge at very slow rates of accretion 100 km juxtapose thick 30 50 km edges of lithosphere against the accreting plate boundary all but nullifying the processes that lead to the emplacement of normal oceanic lithosphere in this environment a relatively strong mantle weld will form at the ridge transform intersection and the thick edges of opposing lithosphere along the length of the transform will tend to confine the strike slip tectonism to a relatively narrow and temporally stable principal transform displacement zone in contrast at very fast rates of accretion large offset transforms 100 km place relatively thin edges of lithosphere

the value of non pollen palynomorphs in interpreting paleoecological change in the great basin nevada usa non pollen palynomorphs npps are identifiable microfossils that survive chemical digestion during pollen extraction and appear in pollen slides they represent important proxies and indicators of environmental change that can be integrated with pollen studies of landscape history npps have been widely studied in europe since the 1970s and regularly included in paleoecological studies whereas in the united states only the most common npps have been routinely tallied the aim of this study is to contribute to the validation of the use of npps in the reconstruction of landscape history we analyzed npps in modern and fossil sediment samples from stonehouse meadow located in spring valley in the eastern part of central nevada we present a total of 64 modern and fossil npps with images and morphological descriptions given for all previously unknown npps and a selection of the most important known npps the comparison of pollen and npps in the fossil sediments improves our interpretation of the ecological changes of the last 8000 yr

a 9170 year record of decadal to multi centennial scale pluvial episodes from the coastal southwest united states a role for atmospheric rivers abstract a well dated 9170 calendar year before present cal yr bp paleohydrologic reconstruction is presented from lower bear lake in the san bernardino mountains of the coastal southwest united states this new multi proxy record is characterized by alternating organic rich carbonate rich sediment units interpreted to reflect hydrologically forced changes in the lake s depositional environment our interpretation of the proxy data indicates nine decadal to multi centennial pluvial episodes pe over the past 9170 cal yr bp of these nine inferred pluvials five are interpreted as more pronounced based on their combined proxy interpretations pe v 9170 8250 pe iv 7000 6400 pe iii 3350 3000 pe ii 850 700 and pe i 500 476 top of core cal yr bp the lower bear lake record indicates that the san bernardino mountains source region for the mojave river and its terminal playa was wet during the same periods within dating errors to several of the major pluvials proposed from the lakes in the sink of the mojave river our comparison extends north also to tulare lake which drains the southcentral western sierra nevada mountains this temporally and spatially coherent signal indicates that a similar climate forcing acted to increase regional wetness at various times during the past 9170 cal yr bp as originally proposed by enzel ely and colleagues e g enzel et al 1989 enzel 1992 ely et al 1994 enzel and wells 1997 we too contend that holocene pluvial episodes are associated with changing the frequency of large winter storms that track across a broad region at decadal to multi centennial timescales we build upon their hypothesis through the addition of new and better dated site comparisons recent advances in the understanding of atmospheric rivers and improved knowledge of the ocean atmosphere dynamics that caused the early 20th century western united states pluvial

radiometric dating 210pb 137cs 241am of recent ombrotrophic peat accumulation and evidence for changes in mass balance the paper summarizes and evaluates the results of 210pb 137cs and 241am analysis on 37 recent ombrotrophic peat profiles from these and previously published data it is concluded that radiometric measurements alone cannot be relied on to give an accurate chronology of peat accumulation where constrained by profiles of 241am activity in the upper part and one or more pollen dated horizons below this 210pb can provide good chronologies of peat accumulation provided the constraint does not displace the calculated 210pb dates by more than c 10 profiles of 137cs activity in most cases fail to contribute significantly to dating recent peat at somewhat degraded sites the residual dry mass of peat representing the last c 150 years is reduced further analysis of well dated profiles suggests that this may reflect loss of catolelm peat newly exposed to aerobic decomposition processes after a fall in water table several mechanisms are proposed for the displacement and net loss of lead including 210pb

rapid climatic change in coastal southern california inferred from pollen analysis of san joaquin marsh pollen analysis and five radiocarbon dates of a 687 cm core provide a detailed chronology of environmental change in a marsh at the head of newport bay orange county california sediment deposition kept pace with sea level rise during the early history of the marsh from ca 7000 to 4500 yr b p the site was a freshwater marsh trees were more abundant than today and grassland was the regional vegetation as sea level rose salt marsh gradually invaded the site brief periods of freshwater marsh 3800 2800 2300 and after 560 yr b p correlate with episodes of global cooling during the neoglacial the historic period is marked by the appearance of exotic species particularly erodium cf cicutarium and eucalyptus and the spores of fungi sporormiella and thecaphora peak influx of pollen spores and charcoal probably reflect greater frequency of flooding and erosion ca 5000 yr b p and during the last 1000 yr

tectonic geomorphology of marine terraces santa barbara fold belt california uplifted marine terraces are common landforms in coastal regions where active tectonics are an important component of landscape evolution such as along the coastal stretches of southern california the pattern and elevation of shoreline angles on active folds provide information about rates of uplift and fold growth which is important for defining tectonic models a particularly impressive succession of marine terraces are developed across the santa barbara fold belt sbfb in southern california which comprises an east west linear zone of active folds and mostly blind faults on the coastal piedmont and in the santa barbara channel the fold belt is characterized by several flights of emergent late pleistocene marine terraces uplifted and preserved on the flanks of active anticlines at several locations along the fold belt the first emergent marine terrace is numerically dated by methods that include uranium series dating on terrace corals 14 c dating on terrace shells and detrital charcoal optically stimulated luminescence of marine terrace sands and oxygen isotopic signatures 18 o of mollusks individual marine terraces have as many as four ages using up to three different dating methods providing confidence in terrace chronology ages of higher terraces are estimated assuming a constant rate of uplift for a particular flight of the 31 terraces 22 formed during a time of falling sea level with 9 forming at or near marine oxygen isotope stage mis 3 or 5 highstands ages and rates of uplift of the first emergent terrace vary systematically from west younger and higher to east older and lower the first emergent marine terraces in the westernmost sbfb are approximately 45 ka mis 3 and the rate of local surface uplift is 2 m k y in the central part of the belt first emergent terraces date to 60 70 ka mis 5 and uplift rates decrease to 1 2 m k y first emergent marine terraces preserved in the easternmost fold belt range from 70 ka to 105 ka mis 5 with rates of local surface uplift of 0 5 m k y lower rates of uplift in the eastern end of the fold belt result from the mis 5 terrace being tilted down into the carpinteria syncline rates of vertical uplift in the western end of the fold belt are about six times higher than previously reported suggesting the seismic hazard is also greater

anomalous oceanic lithosphere formed in a leaky transform fault evidence from the western limassol forest complex cyprus detailed studies in the western limassol forest complex cyprus have revealed plutonic and structural histories that differ markedly from the penrose type ophiolite of the troodos massif to the north a tectonized harzburgite of upper mantle origin acts as host to multiple mafic and ultramafic intrusions forming a plutonic core complex mafic and picrite dykes cut and are cut by e w trending shear zones demonstrating syn tectonic magmatism a retrogressive metamorphic and progressive cooling history of the intrusive suite indicates uplift of the host mantle harzburgite while in a sea floor setting it is suggested here that the geological evolution of the western limassol forest complex indicates formation of anomalous oceanic lithosphere in the active domain of an upper cretaceous leaky transform fault

sulfate rich eolian and wet interdune deposits erebus crater meridiani planum mars this study investigates three bedrock exposures at erebus crater an 300 m diameter crater approximately 4 km south of endurance crater on mars these outcrops called olympia payson and yavapai provide additional evidence in support of the dune interdune model proposed for the formation of the deposits at the opportunity landing site in meridiani planum there is evidence for greater involvement of liquid water in the olympia outcrop exposures than was observed in eagle or endurance craters the olympia outcrop likely formed in a wet interdune and sand sheet environment the facies observed within the payson outcrop which is likely stratigraphically above the olympia outcrop indicate that it was deposited in a damp wet interdune sand sheet and eolian dune environment the yavapai outcrop which likely stratigraphically overlies the payson outcrop indicates that it was deposited in primarily a sand sheet environment and also potentially in an eolian dune environment these three outcrop exposures may indicate an overall drying upward trend spanning the stratigraphic section from its base at the olympia outcrop to its top at the yavapai outcrop this contrasts with the wetting upward trend seen in endurance and eagle craters thus the series of outcrops seen at meridiani by opportunity may constitute a full climatic cycle evolving from dry to wet to dry conditions

a late holocene paleoecological record from torrey pines state reserve california abstract paleoenvironments of the torrey pines state reserve were reconstructed from a 3600 yr core from los penasquitos lagoon using fossil pollen spores charcoal chemical stratigraphy particle size and magnetic susceptibility late holocene sediments were radiocarbon dated while the historical sediments were dated using sediment chemistry fossil pollen and historical records at 3600 yr b p the estuary was a brackish water lagoon by 2800 yr b p poaceae grass pollen increased to high levels suggesting that the rising level of the core site led to its colonization by spartina foliosa cord grass the lowest elevation plant type within regional estuaries an increase in pollen and spores of moisture dependent species suggests a climate with more available moisture after 2600 yr b p this change is similar to that found 280 km to the north at 3250 yr b p implying that regional climate changes were time transgressive from north to south increased postsettlement sediment input resulted from nineteenth century land disturbances caused by grazing and fire sedimentation rates increased further in the twentieth century due to closure of the estuarine mouth the endemic pinus torreyana torrey pine was present at the site throughout this 3600 yr interval but was less numerous prior to 2100 yr b p this history may have contributed to the low genetic diversity of this species

high temperature alteration of abyssal ultramafics from the islas orcadas fracture zone south atlantic ultramafic rocks dredged from the islas orcadas fracture zone along the sw indian ocean ridge 6 e and 54 s show evidence of progressive hydration beginning at temperatures greater than 600 c and perhaps as high as 900 c and continuing to less than 50 c there are two principal types of alteration present in the ultramafic rocks both of which are the result of hydration reactions the first type of alteration involves hydration of original clinopyroxene orthopyroxene and olivine to amphibole talc secondary olivine and serpentine the second is a vein type of alteration and results in the formation of veins of amphibole chlorite talc and serpentine the alteration appears to be episodic the sequence of events suggested by the petrography is 1 clinopyroxene altering to amphibole 2 orthopyroxene altering to talc or talc olivine 3 supersolvus hornblende veining 4 coexisting actinolite hornblende veining 5 chlorite chlorite actinolite or chlorite secondary clinopyroxene veining 6 talc veining 7 serpentine veining and 8 pervasive serpentinization the alteration fluid is most likely seawater it is suggested that the high temperature alterations may reflect seawater circulation into the upper mantle

prehistoric fires and the shaping of colonial transported landscapes in southern california a paleoenvironmental study at dune pond santa barbara county using a novel combination of paleoecologic proxies including pollen non pollen palynomorphs npps macroscopic charcoal and spheroidal carbonaceous particles scps 5000 years of landscape change fire history and land use have been reconstructed from dune pond santa barbara county california the pond was sensitive to holocene regional climatic variability showing different phases of lower 4600 3700 cal yr bp 2100 700 cal yr bp historical period and higher 3700 2100 cal yr bp 700 150 cal yr bp local moisture availability during this period the landscape was dominated by a coastal mosaic vegetation including dune mats coastal scrub and salt marshes on the dunes and backdunes with chaparral and oak woodland growing in the valley plains and foothills fire was intimately linked with such dominating mosaic vegetation and the combination of wet conditions and the presence of nearby human settlement were a trigger favoring coastal fires for at least two periods from 3100 to 1500 cal yr bp and from 650 cal yr bp until the 18th century in both cases fire was an important tool to keep an open coastal landscape attractive to hunting wildlife finally matching this varied range of high resolution paleoecological proxies with historical records we could characterize the development of colonial transported landscapes following the euro american settlement of santa barbara the introduction of livestock grazing by spanish colonists favored erosive processes and the introduction of fecal borne parasites in freshwater bodies negatively impacted salt and brackish coastal marshes and promoted the invasion of alien grasses and ruderals this agro pastoral landscape was consolidated during the american period with a greater role for cultivation the development of industrial activities and increased population despite negative environmental consequences such as the loss of native habitats exotic land uses and plants introduced during the historical period significantly contributed to the configuration of a cultural landscape which forms part of the cultural heritage of california

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

the late holocene dry period multiproxy evidence for an extended drought between 2800 and 1850 cal yr bp across the central great basin usa abstract evidence of a multi centennial scale dry period between 2800 and 1850 cal yr bp is documented by pollen mollusks diatoms and sediment in spring sediments from stonehouse meadow in spring valley eastern central nevada u s we refer to this period as the late holocene dry period based on sediment recovered stonehouse meadow was either absent or severely restricted in size at 8000 cal yr bp beginning 7500 cal yr bp the meadow became established and persisted to 3000 cal yr bp when it began to dry comparison of the timing of this late holocene drought record to multiple records extending from the eastern sierra nevada across the central great basin to the great salt lake support the interpretation that this dry period was regional the beginning and ending dates vary among sites but all sites record multiple centuries of dry climate between 2500 and 1900 cal yr bp this duration makes it the longest persistent dry period within the late holocene in contrast sites in the northern great basin record either no clear evidence of drought or have wetter than average climate during this period suggesting that the northern boundary between wet and dry climates may have been between about 40 and 42 n latitude this dry in the southwest and wet in the northwest precipitation pattern across the great basin is supported by large scale spatial climate pattern hypotheses involving enso pdo amo and the position of the aleutian low and north pacific high particularly during winter

morphology internal composition and origin of drumlins in the southeastern part of the chelmno dobrzyn lakeland north poland abstract the sedimentology of four drumlins in north poland formed by complex basal ice flow along elongated glacial depressions in the southeastern part of the chelmno dobrzyn lakeland is examined in detail field data indicate that they developed initially by deformation and erosion of a variety of subglacial bed materials including till glaciofluvial and glaciolacustrine sediments with subsequent formation of proto drumlin nuclei models for formation of these nuclei due to complex pore water pressure perturbations on high and low permeability glacier beds are presented the proto drumlin nuclei that developed became relatively stable obstacles resistant to the shear stress imposed by overriding basal ice stabilised nuclei acted as points where till accumulation commenced proceeding by accretion of basal debris episodic erosion by subglacial meltwater produced discontinuous sandy intercalations within the accreting till beds

polygenetic ophiolite belt of the california sierra nevada geochronological and tectonostratigraphic development the assumption that ophiolite sequences are generated at essentially one point in geologic time by the process of sea floor spreading is critical for modern concepts in the tectonics of ophiolites and for topics dealing with their structure and petrology however this assumption has only been verified in a few locations by an integrated geochronological and structural stratigraphic approach many ophiolite sections are reconstructed from structurally disrupted sequences with the idealized ocean floor model in mind such reconstructions are prone to error without adequate age control on each of the reconstructed fragments this is a significant problem in structurally complex regions where more than one generation of ophiolite may be present in this paper new pb u zircon ages are presented for key locations along a 375 km segment of the western sierra nevada ophiolite belt these age data are combined with structural stratigraphic observations and published ages and significant tectonic implications for the ophiolite belt emerge three different ophiolitic assemblages are recognized with igneous ages of about 300 200 and 160 m y b p rocks of the 300 m y assemblage are in a completely disrupted array of metamorphic tectonite slabs and serpentinite matrix melange fragments of upper paleozoic seamounts occur in association with the ophiolitic melange and together these assemblages constitute the basement framework for the western sierra pb u and k ar isotopic systematics are complex within this framework and indicate a polymetamorphic history systematics in the 200 and 160 m y assemblages are less complex and give tighter igneous age constraints rocks of the 200 m y assemblage are in a semi intact state with only local tectonite and melange zones rocks of the 160 m y assemblage are intact but nevertheless deformed both the 200 and 160 m y assemblages have equivalent age basinal volcanic sedimentary sequences that lie unconformably above the ophiolitic melange basement in each case the basinal sequences locally extend conformably into the upper stratigraphic levels of the age equivalent ophiolite sections these relations along with vestiges of intrusive contacts between the edges of both younger ophiolites and the melange basement indicate that the younger ophiolites underwent igneous formation in proximity to the melange basement the sierran ophiolite belt is considered to have formed by a multistage process initiated by the early mesozoic tectonic accretion of upper paleozoic sea floor in general proximity to the ancient continental margin regional metamorphism and ophiolitic melange resulted this accretionary nucleus became the basement of jurassic age primitive volcanic arc terranes which underwent rifting episodes during the production of the 200 and 160 m y ophiolites the rifting episodes resulted in the formation of sedimentary basins which were the depositional sites of volcanic sedimentary sequences non volcanic sources for the basinal sedimentary rocks include the melange basement and continental margin terranes contact zones between pre existing basement and the juvenile ophiolitic sequences created during the rifting episodes consist of dynamothermal metamorphic aureoles protoclastic deformation zones and cross cutting dikes such edge zone assemblages are in most localities obscurred or destroyed by superimposed deformations resulting from convergent and perhaps transform motions along basin edges both the 200 and 160 m y basins were destroyed by compressional orogenic episodes shortly after their formational episodes destruction of young ophiolite floored basins may be a common course of events when small oceanic type plates are generated along continental margin environments such tectonic settings are ideal for the emplacement of young ophiolite sheets

coastal flooding and the 1861 2 california storm season abstract a series of large storms attributed to atmospheric river conditions struck the california coast in the winter of 1861 2 although historical accounts document inland flooding little is known about how the 1861 2 storms impacted the now heavily developed california coast here we show that the 1861 2 storms emplaced a deposit of beach sand up to 50 cm thick over 450 m inland within a southern california salt marsh this deposit is unprecedented in the post european sediments of the marsh and more extensive than that derived from any other historical event it is comparable in scale to hurricane and tsunami washover fans in back barrier environments along other coastlines the presence of overwash deposits in carpinteria suggests that the 1861 2 storm season was erosive enough to remove coastal barriers allowing for inundation of parts of the coastline currently developed efforts to prepare for a recurrence of an 1861 2 like storm season should address potential coastal impacts likewise interpretations of past washover deposits should consider these unusually prolonged stormy periods in addition to hurricane and tsunami inundation

enhanced late holocene enso pdo expression along the margins of the eastern north pacific abstract pacific climate is known to have varied during the holocene but spatial patterns remain poorly defined this paper compiles terrestrial and marine proxy data from sites along the northeastern pacific margins and proposes that they indicate 1 suppressed enso conditions during the middle holocene between 8000 and 4000 cal bp with a north pacific that generally resembled a la nina like or more negative pdo phase and 2 a climate transition between 4200 and 3000 cal bp that appears to be the teleconnected expression to a more modern like enso pacific compared to modern day conditions the compiled data suggest that during the middle holocene the aleutian low was generally weaker during the winter and or located more to the west while the north pacific high was stronger during the summer and located more to the north coastal upwelling off california was more enhanced during the summer and fall but suppressed during the spring oregon and california sea surface temperatures ssts were cooler the santa barbara basin had an anomalous record suggesting warmer ssts late holocene records indicate a more variable el nino like and more positive pdo pacific the aleutian low became more intensified during the winter and or located more to the east the north pacific high became weaker and or displaced more to the south coastal upwelling off california intensified during the spring but decreased during the fall oregon and california ssts became warmer recording the shoreward migration of sub tropical gyre waters during the fall while spring upwelling cooler sst increased in the santa barbara basin the high resolution proxy records indicate enhanced enso and pdo variability after 4000 cal bp off southern california 3400 cal bp off northern california and by 2000 cal bp in southwestern yukon a progressively northward migration of the enso teleconnection during the late holocene is proposed

a 9000 year flood history for southern california a revised stratigraphy of varved sediments in santa barbara basin abstract the center of santa barbara basin sbb preserves annual laminations through most of the holocene providing an important locality for high resolution late quaternary paleoclimate and paleoceanography reconstructions an accurate chronology is necessary for these sediment based records and enables comparisons with more distal data time series of similar quality here we present an improved high resolution radiocarbon chronology for the last 9000 yrs based on 89 accelerator mass spectrometric ams 14c dates of mixed planktonic foraminiferal carbonate from three sediment cores collected in sbb mv0811 14jc spr0901 06kc and odp hole 893a accurate core to core correlation is demonstrated using prominent gray flood and olive turbidite layers identified in sbb and dated in multiple cores gray layer deposits were found more frequently in wetter intervals as determined by multi proxy hydroclimate records in southern california e g lake deposits and tree rings mass accumulation rates mars calculated for the sbb depocenter using the improved radiocarbon age model indicate high mars are associated with these gray layers that have been associated with floods thus sediment accumulation in sbb is largely controlled by sediment delivery via river runoff following precipitation events although mars may also be influenced by other factors that enhance erosion in river catchments folded sediment is observed within the basal core section of mv0811 14jc which stratigraphically correlates with 14c age reversals in odp hole 893a we associate this sediment slump feature with the large goleta submarine slide complex in santa barbara channel and estimate the submarine slide event occurred at 9000 200 yrs bp furthermore small olive turbidite layers identified and dated in sbb can be temporally linked with large earthquakes along san andreas fault and can therefore potentially reconstruct earthquake history in southern california

holocene paleoecology of an estuary on santa rosa island california abstract the middle to late holocene history and early anglo european settlement impacts on santa rosa island california were studied through the analysis of sediments in a small estuarine marsh a 5 4 m long sediment core produced a stratigraphic and pollen record spanning the last 5200 yr three major zones are distinguishable in the core the lowermost zone 5200 to 3250 yr b p represents a time of arid climate with predominantly marine sediment input and high chenopodiaceae and ambrosia pollen values the intermediate zone 3250 yr b p to 1800 a d is characterized by greater fresh water input and high values for asteraceae and cyperaceae pollen and charcoal particles the uppermost zone 1800 a d to present documents the unprecedented erosion sedimentation and vegetation change that resulted from the introduction of large exotic herbivores and exotic plants to the island during anglo european settlement the identification of pollen grains of torrey pine pinus torreyana documents the persistence of this endemic species on the island throughout the middle to late holocene

the impact of hydroclimate and dam construction on terrigenous detrital sediment composition in a 250 year santa barbara basin record off southern california abstract the recurrence and magnitude of southern california hydroclimate extremes are poorly resolved due to the relatively short duration

fire and vegetation history on santa rosa island channel islands and long term environmental change in southern california the long term history of vegetation and fire was investigated at two locations soledad pond 275 m from ca 12 000 cal a bp and abalone rocks marsh 0 m from ca 7000 cal a bp on santa rosa island situated off the coast of southern california a coastal conifer forest covered highlands of santa rosa during the last glacial but by ca 11 800 cal a bp pinus stands coastal sage scrub and grassland replaced the forest as the climate warmed the early holocene became increasingly drier particularly after ca 9150 cal a bp as the pond dried frequently and coastal sage scrub covered the nearby hillslopes by ca 6900 cal a bp grasslands recovered at both sites pollen of wetland plants became prominent at soledad pond after ca 4500 cal a bp and at abalone rocks marsh after ca 3465 cal a bp diatoms suggest freshening of the abalone rocks marsh somewhat later probably by additional runoff from the highlands introduction of non native species by ranchers occurred subsequent to ad 1850 charcoal influx is high early in the record but declines during the early holocene when minimal biomass suggests extended drought a general increase occurs after ca 7000 cal a bp and especially after ca 4500 cal a bp the holocene pattern closely resembles population levels constructed from the archaeological record and suggests a potential influence by humans on the fire regime of the islands particularly during the late holocene copyright 2009 john wiley sons ltd

historic and holocene environmental change in the san antonio creek basin mid coastal california using a combination of pollen non pollen palynomorphs npps and charcoal particle stratigraphies from sediment cores from two sites along with historical records we reconstructed paleoenvironmental change in mid coastal california the san antonio creek section contains a discontinuous holocene length record while mod pond includes a continuous late holocene record together the records allow for interpretation of most of the present interglacial the longer record documents coastal sage scrub and chaparral dominated by woodland elements early in the holocene to about 9000 yr ago a potential decline in woodland communities with drying conditions during the middle holocene to about 4800 yr ago and an expansion of coastal sage scrub with grassland during the late holocene evidence for climatic fluctuations during the last 1000 yr at mod pond is equivocal suggesting that the medieval climate anomaly little ice age had modest impact on the mod pond environment however evidence of significant environmental change associated with cultural transitions in the 18th 19th centuries is stark introduction of non native plants establishment of cattle and sheep grazing missionization of the native population changes in burning practices during the spanish period and enhanced cropping activities during north american settlement worked together to substantially modify the mid california coastal landscape in about a century s time

a 560 year record of santa ana fires reconstructed from charcoal deposited in the santa barbara basin california microscopic charcoal from varved santa barbara basin sediments was used to reconstruct a 560 yr record a d 1425 to 1985 of santa ana fires comparison of large 3750 m2 charcoal with documented fire records in the santa barbara ranger district shows that high accumulations correspond to large fires 20 000 ha that occurred during santa ana conditions the charcoal record reconstructed a minimum of 20 large fires in the santa barbara region during the study period the average time between fires shows no distinct change across three different land use periods the chumash period apparently characterized by frequent burning the spanish early american period with nominal fire control and the 20th century with active fire suppression pollen data support the conclusion that the fire regime has not dramatically changed during the last 500 yr comparison of large charcoal particle accumulation rates and precipitation reconstructed from tree rings show a strong relationship between climate and fire history with large fires consistently occurring at the end of wet periods and the beginning of droughts

mantle flow at oceanic spreading centers models derived from ophiolites abstract the internal structures of eleven ophiolite complexes have been structurally investigated the attitude of the foliation and the lineation in the peridotites is related to asthenospheric flow in the uppermost mantle at an oceanic spreading center from the orientation of these structures with respect to the paleohorizontal plane two oceanic situations are distinguished the horizontally spreading asthenosphere illustrated by the table mountain massif newfoundland is characterized by 1 a homogeneous regular and sub horizontal plastic flow pattern over large distances 2 b flat paleo mono and absence of large scale folding 3 c rare economical chromite deposits and depleted mantle the diapirically spreading asthenosphere illustrated by the acoje type philippines displays 1 a inhomogeneous and sub vertical plastic flow pattern 2 b deformed paleo moho and large scale folds 3 c important economical chromite deposits and less depleted mantle presumably due to secondary magmatic impregnation this leads to vogt s model of asthenospheric flow beneath an oceanic ridge the direction of which being equated with the dike swarm in this model the horizontally spreading asthenosphere is derived from the diapirically spreading one in the following way the vertical mantle flow at the diapir center diverges horizontally in every direction including that parallel to the ridge at about 50 km from the diapir center the mantle flow becomes progressively perpendicular to the ridge due to the damming effect of transform faults an important economical consequence of this model is that large chromite deposits are expected preferentially in the diapiric type of ophiolite because chromite is preferentially precipitated at the diapir center from pristine magma