palaeoclimatic implications of the occurrence of the arcoid bivalve anadara trapezia deshayes in the quaternary of australasia abstract the arcoid bivalve anadara trapezia deshayes 1840 is a eurythermal estuarine mollusc that flourishes at present in eastern australia between port phillip bay victoria and townsville in northern queensland a trapezia first appeared in the australian quaternary fossil record during oxygen isotope stage ois 7 in new zealand where it is now extinct the earliest known occurrences are in the rangitawa fossil beds and in uppermost castlecliffian strata west of wanganui north island ois 11 ca 400 ka the species had an extensive distribution during the last interglacial maximum ois 5e in both australia and new zealand and appears to have had a slightly wider than present geographic range in southeastern australia during the middle holocene as shown by records from tasmania and western victoria where it no longer lives apart from an isolated population inhabiting oyster harbour western australia a trapezia has not been confirmed living in coastal waters west of port phillip bay victoria it became extinct in new zealand sometime after ois 5e the extensive distribution and abundance of a trapezia and other fauna of subtropical affinity during the last interglacial maximum in areas where both are now extinct appears to be associated with an enhanced leeuwin current at that time coinciding with higher less seasonally concentrated levels of precipitation and river discharge the arrival of a trapezia in australasian coastal waters may have been a consequence of planktonic dispersal from southern south america a bravardi del rio from the middle miocene puerto madryn formation on the valdes peninsula argentina may be a possible ancestor for a trapezia

pollen distribution in marine sediments on the continental margin off northern california abstract pollen analysis of 84 samples from surface sediment of the continental margin off northern california between 38 and 39 n and 123 and 124 w shows that the composition of pollen assemblages in this part of the north pacific ocean reflects the regional vegetation of the russian river and other local drainage basins of the northern coast of california systematic trends in the quantitative and qualitative variations in these marine pollen assemblages show that fluvial and marine transport are important factors in determining the nature of pollen assemblages offshore these conclusions are supported by the analyses of pollen in rivers of the north coast of california and in particulate matter collected in a mid slope sediment trap

earthquakes a hand on the aftershock trigger received wisdom relates that static stress change associated with an earthquake mainshock is the prime mover of its aftershocks but a fresh look at the data points the finger at wave surfing dynamic stress

direct correlation of terrestrial and marine paleoclimatic records from four glacial interglacial cycles dsdp site 594 southwest pacific abstract over the last 350 ka changes in the composition of vegetation on new zealand inferred from pollen analysis of the upper 40 m of dsdp site 594 at 2 4 ka sample intervals reflect regional climatic variations which appear synchronous with implied variations in glacier fluctuation and in global climatostratigraphy described from sedimentary and oxygen isotope records from the same samples nelson et al 1985 pollen assemblages from isotope stages 1 5e 7a 7b and 9 are distinguished by conifer and broadleaf forest taxa which vary in composition between the last four interglacials suggesting significant differences in precipitation temperature and or migration rates glacial pollen assemblages which imply the expansion of herbland and decline in forest components show less variation and generally indicate comparatively cool conditions on the east coast of south island interstadial vegetation is composed of a mosaic of shrubland herbland vegetation the close correspondence between variations in the amplitude and timing of these continuous records of forest development in the changing vegetation of south island new zealand and oxygen isotope climatostratigraphy supports previous suggestions that late quaternary southern and northern hemisphere climatic fluctuations were essentially synchronous

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

a long late quaternary record from lake poukawa hawke s bay new zealand abstract the lake poukawa basin is a large co seismic depression located at 20 m above mean sea level in hawke s bay in eastern north island new zealand we present a detailed environmental history of the basin for the last c 60 ka based on analyses of the top 105 m of a 200 m core record dating control is provided by radiocarbon optically stimulated luminescence osl and u th disequilibrium ages the chronology is supported by nine tephras of inferred age including marker tephras kawakawa 22 590 230 yr bp at 18 25 m core datum tahuna c 35 43 ka at 33 1 m core datum and rotoehu 45 50 ka at 39 1 m core datum disagreements between some of the older tephra ages and the numerical ages from the osl and u th dating mean that more than one age model can be applied three major lithostratigraphic units are identified a basal calcareous silt with lignitic peats between 105 28 and 98 58 m of marine oxygen isotope stage mis 3 age an extended sequence of detrital shelly sands and silts between 98 58 and 8 m of mis 3 and 2 age and a holocene peat unit mis 1 from 8 to 0 m alternatively but less likely the basal unit may represent stage mis 5a and the detrital shelly sands would then contain an amalgam of mis 4 3 and 2 deposits we propose a notably moist phase represented by the peat which our numerical dating model places near the start of isotope stage 3 this suggests the existence of mild conditions during an interstadial in central new zealand at c 55 50 ka when a podocarp beech broadleaf forest of near interglacial affinity surrounded the basin the interstadial is marked by both lake and peat formation in the basin after 50 ka a thermal decline set in though the climate remained moist initially under these conditions the poukawa basin was rapidly infilled by alluvial fan deposits from the surrounding hills the floor of the basin was occupied by grasses and sedges responding to both the highly disturbed environment and swampy conditions in the basin after the deposition of the rotoehu ash effective precipitation declined markedly and woody shrubs expanded across the previously swampy basin floor the data suggest an apparent thermal decline of c 6 7 c for much of mis 2 and the latter half of mis 3 the holocene was marked by the establishment of fen and lake environments on the basin floor prior to human disturbance podocarp broadleaf forest surrounded the basin

vegetation and climate change during the last interglacial glacial cycle in western tasmania australia abstract cool temperate phyllocladus aspleniifolius nothofagus cunninghamii rainforest occurred in western tasmania during isotope substage 5e during most of the last glacial stage substage 5d to stage 2 the vegetation was subalpine woodland and shrubland or alpine grassland herbland and heathland montane and subalpine rainforest existed at mid altitude 516 m during substages 5a and 5c during stage 2 the late wisconsin glacial maximum most of western tasmania had alpine grassland and herbland vegetation with areas of sclerophyll woodland and rainforest taxa below 100 m on valley floors near the coast cool temperate rainforest developed again during late glacial times after 14 k 14 c yr bp with maximum development of nothofagus cunninghamii rainforest in the early holocene estimates of temperature depression based on depression of the altitudinally zoned vegetation communities a lapse rate of 0 65 c 100 m and comparison with marine core rc 11 120 from the southwestern sub polar indian ocean indicate that the early stadials substages 5b and 5d were cold and the early interstadials substages 5a and 5c were cool stage 4 was cold and probably fully glacial temperature increased early in stage 3 but then decreased with some fluctuations towards stage 2 the late wisconsin glacial maximum an abrupt increase in temperature of ca 6 c occurred after 14 k 14 c yr bp

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

a hypothesis for delayed dynamic earthquake triggering 1 it s uncertain whether more near field earthquakes are triggered by static or dynamic stress changes this ratio matters because static earthquake interactions are increasingly incorporated into probabilistic forecasts recent studies were unable to demonstrate all predictions from the static stress change hypothesis particularly seismicity rate reductions however current dynamic stress change hypotheses do not explain delayed earthquake triggering and omori s law here i show numerically that if seismic waves can alter some frictional contacts in neighboring fault zones then dynamic triggering might cause delayed triggering and an omori law response the hypothesis depends on faults following a rate state friction law and on seismic waves changing the mean critical slip distance dc at nucleation zones

anomalous stress diffusion in earthquake triggering correlation length time dependence and directionality 1 it has been recently suggested that moderate and large earthquakes can be triggered by similarly sized events at very long range here we study the main characteristics of earthquake triggering by determining its correlation length time dependence and directionality the problem is examined at a global level by using the harvard centroid moment tensor catalogue our results show that the correlation lengths depend only weakly on the magnitude thresholds involved no significant systematic triggering is observed for distances greater than the lithospheric thickness 100 150 km and the correlation length magnitude is similar to the seismogenic thickness 10 20 km the mean triggering distance and correlation length both increase with time very slowly compared with what would be expected from a normal diffusion process this is consistent with a clock advance on the failure time based on the constitutive rules for subcritical crack growth following a transient change in the loading stress the power law scaling disappears after a few months a functional form for the probability of triggering as a function of time and distance is proposed on the basis of the properties of near critical point systems the model fits the data well and could be used to calculate conditional probabilities for time dependent seismic hazard due to earthquake triggering an apparent directionality effect that was observed in the data set can be attributed to an artefact of poor depth determination these results do not preclude individual long range triggering with a potential directionality effect but they do rule out a statistical correlation at distances much greater than the thickness of the lithosphere

late quaternary vegetation and climate change in southeastern australia palynological evidence from marine core e55 6 abstract palynological analysis of core e55 6 obtained from off shore western victoria provides a record of vegetation and climate change in the southeastern south australian and western victorian region spanning much of the last 125 000 yr an accompanying oxygen isotope record provides a chronology for the sequence the pollen record suggests that maximum effective precipitation occurred during the height of the last interglacial oxygen isotope substage 5e with wet sclerophyll forest and rainforest widespread in the region effective precipitation appears to have decreased during substage 5d promoting the expansion of dry sclerophyll communities then increased slightly during substage 5c with the limited re occurrence of wetter forest types climatic conditions gradually became drier from substage 5b with the replacement of eucalypt dominated forest by more open heath and mallee type communities in the arid glacial conditions of isotopic stage 4 a brief phase of increased effective precipitation occurred during the interstadial stage 3 with limited expansion of eucalyptus followed by a steady decline in effective precipitation and the expansion of open heath and grass communities pollen is very sparse in the top section of the core making environmental interpretation difficult nevertheless it appears that grass and heath communities dominated the region during stage 2 there is no clear record of the holocene due to the presence of mudflow sediments in the top of the core the pollen evidence also suggests that continental shelf exposed as sea levels fell was colonised by a mosaic of coastal vegetation including myrtaceae dominated scrub eucalypt and casuarina woodland asteraceae and chenopodiaceae dominated heath and grassland the charcoal record expressed as a ratio to pollen concentration gives evidence of increased burning during the height of the last interglacial period most likely in response to increased fuel loads with the expansion of eucalypt dominated forest this record also indicates a second phase of increased burning commencing in stage 2 which gives possible evidence for increased anthropogenic activity in the region

a high resolution record of vegetation and climate through the last glacial cycle from caledonia fen southeastern highlands of australia a blocked tributary has provided a rare site of long term sediment accumulation in montane southeastern australia this site has yielded a continuous detailed pollen record through the last ca 140 000 years and revealed marked vegetation and environmental changes at orbital to sub millennial scales radiocarbon and optically stimulated luminescence osl or optical ages provide some chronological control for the last ca 70 000 years most of the sediment is inorganic but with well preserved pollen that accumulated under unproductive and probably largely ice covered lake conditions the lake was surrounded by low growing plants with an alpine character exceptions include three discrete periods of high organic sedimentation in the basin and forest development in the surrounding catchment the two major periods of forest expansion are related to the last interglacial and the holocene with the third shorter period considered to represent an interstadial in the early part of marine isotope stage mis 3 the latter part of the last glacial period is characterised by abrupt sub millennial amelioration events that may relate to documented global oscillations emanating from the north atlantic there are systematic changes through the record that can be partly attributed to basin infilling but the progressive reduction and regional extinction of some plant taxa is attributed to a long term trend towards climatic drying copyright 2007 john wiley sons ltd

stratigraphy pollen analysis and paleoclimatic interpretation of pulbeena swamp northwestern tasmania sedimentary palynologic and 14c analysis of 480 cm of freshwater marl and swamp peat deposits formed under the influence of fluctuating artesian springs provides a paleoenvironmental and paleoclimatic record of approximately 65 000 yr for northwestern tasmania the holocene pollen zone 1 11 000 0 yr b p climate was warm and moist and forest vegetation was dominant throughout the area during the later part of the last glacial stage pollen zone 2 35 000 11 000 yr b p the climate was generally drier and grassy open environments were widespread the driest part of this period occurred between 25 000 to 11 000 yr b p when temperatures in western tasmania were markedly reduced during the last major phase of glaciation prior to 35 000 yr b p pollen zones 3 9 a long interstadial complex dating to the middle of the last glacial stage is recognized during this period the climate was generally moist and forest and scrub communities were more important than during the later part of the last glacial stage except during pollen zone 5 when high gramineae plus compositae values suggest drier conditions high gramineae and compositae values also occur in pollen zone 10 at the base of the diagram they suggest that a phase of drier and cooler climatic conditions occurred during the early part of the last glacial stage

late quaternary palaeoceanography near tasmania southern australia abstract this study of the palaeoceanographic record south of australia is based on two cores taken from lower circumpolar deep water depths core e27 30 located south of tasmania in water depth of 3552 m to the north of the present location of the subtropical convergence and core e55 6 from the continental margin off victoria at 2346 m depth in a region of very low surface productivity a preliminary examination of planktonic foraminiferal faunas in core e27 30 located south of tasmania provides a record of movement of the subtropical convergence through the late quaternary that is consistent with records elsewhere in the southeast indian ocean the convergence has been located equatorward of its present position through much of the late quaternary with poleward excursions in the holocene and at oxygen isotope stage 5e benthic foraminiferal faunas contrast strongly in the two cores despite their location at similar depths within the same water mass core e55 6 is largely dominated by deep infaunal taxa while core e27 30 has a high proportion throughout of epifaunal taxa the benthic foraminiferal fauna in core e27 30 is dominated by epistominella exigua known to feed directly on phytoplankton detritus in the modern deep sea abundances of that species coincide with the presence of the subtropical convergence at or near the site indicating that surface phytoplankton production has had a major influence on benthic productivity dissolution records in the two cores also differ markedly core e55 6 records a strong dissolution event in oxygen isotope stage 4 the cause of the event is not clear although it appears to be associated with increased productivity levels this pronounced dissolution event is not evident in core e27 30 suggesting either the event is localised or that the record in core e27 30 has been overprinted by the convergence the extent to which the records in the two cores vary emphasises the influence of frontal structures on core records in this region and the need to take this into account when investigating southern ocean history

an early to middle pleistocene palynological record from the volcanic crater of pejark marsh western plains of victoria southeastern australia abstract a discontinuous 70 m sediment core was extracted from the volcanic crater of pejark marsh to temporally extend the existing quaternary record of vegetation and environments from the western plains of victoria the sequence was fission track dated to the early middle pleistocene transition both the sediments and the aquatic pollen indicate a general lake shallowing and progressive increase in drying and peat deposition events the major dry land pollen taxa are similar to those that dominate the late quaternary records from the area and indicate the alternation of regionally dominant sclerophyll forest during wetter periods and steppe or open woodlands during drier periods a major feature of the pollen record is the presence of a number of regionally extinct taxa in the basal half of the record some of these taxa including araucaria canthium and microcachrys represent major range extensions of previously considered regionally extinct taxa into the pleistocene tentative correlation with the marine oxygen isotope record suggests that the sequence may extend from isotope stages 30 to 17 with major changes within the record relating to the transition from the higher frequency lower amplitude orbitally forced climatic cycles of the early pleistocene to the lower frequency higher amplitude cycles of the middle late pleistocene

a chronology for the long pollen record from lake wangoom western victoria australia as derived from uranium thorium disequilibrium dating the chronology of a long pollen record from lake wangoom one of the few long palaeoenvironmental records from southeastern australia is discussed in light of the acquisition of new uranium thorium disequilibrium utd dates of crucial importance has been the estimation of ages for two major pre holocene phases of forest expansion recorded in the sequence with implications for the timing of periods of high effective precipitation in the region the new utd ages indicate that the oldest forest phase falls within the penultimate interglacial whereas the later phase corresponds with the last interglacial this is older than indicated by previously reported utd and radiocarbon dates but confirms a chronology based on direct correlation with the pollen record from marine core e55 6 the new chronology of the lake wangoom sequence provides evidence that phases of sustained forest development in southeast australia relate to interglacial periods in comparison interstadial periods appear to be characterised by only minor arboreal development marked differences in the pattern of vegetation development evident in each of the interglacials are thought to reflect varying climatic and anthropogenic influences copyright 2002 john wiley sons ltd

the last glacial cycle from wyelangta the otway region of victoria australia abstract this paper presents the first long quaternary palynological record from the otway region of victoria an area which is biogeographically important in that it is an outlier of the southeastern highlands containing distinctive forest vegetation with great similarities to the island of tasmania the record is derived from a small remnant patch of cool temperate rainforest dominated by nothofagus cunninghamii surrounded by tall open eucalypt forest three clear phases are identified an older rainforest phase dated to beyond 40 000 years bp which probably represents the latter part of oxygen isotope stage 5 a phase of more open vegetation which covers at least part of the last glacial period and a younger rainforest phase of holocene age the record is significant in providing refinements to late quaternary climatic estimates from southeastern australia utilising the climatic profiles of key rainforest taxa and in indicating the likely presence and nature of a glacial rainforest refugium the occurrence of a major rain forest tree phyllocladus during the early forest phase and of the subalpine taxon gunnera during the last glacial period taxa now restricted to tasmania demonstrates an even greater biogeographic link to this island in the recent past their extinction on the mainland is consistent with the general demise of cool temperate taxa with close gondwanan affinities on the australian mainland through the late cenozoic period their late disappearance contributes to the growing list of mainland extinctions of ancient and geographically interesting taxa adding weight to the proposal that aboriginal burning has had a substantial impact on the australian landscape during the last glacial cycle

wetting and drying of australia over the past 300 ka alternately dry and wet climatic episodes across central and eastern australia during the past 300 ka have greatly affected australia9s rivers lakes and dune fields evidence of widespread climate and flow regime changes has been provided by 75 thermoluminescence tl dates and 18 u th dates from alluvial and eolian sediments fluvial conditions dominated part of the last two interglacials stage 5 and 7 resulting in large sand loads in rivers in the present simpson desert and southeastern australia during the last interglacial fluvial activity in central australia peaked at 110 ka stage 5 pluvial probably 5 10 ka behind world temperature and sea level maxima following the last late interglacial wet phase aridity associated with dune building spread from central australia toward its margins achieving greatest intensity during the last glacial maximum a less widespread wet phase identified at about 55 35 ka stage 3 subpluvial is associated with high lake levels and paleochannel activity in southeastern australia this tl record of variable continental aridity in australia correlates well with global changes including the variable eolian dust flux into central china the northern pacific ocean and antarctica

a late pleistocene and holocene vegetation and environmental record from lake wangoom western plains of victoria australia abstract pollen microfaunal and sedimentological evidence from the top 20 m of sediment in a closed volcanic crater lake is used to construct a detailed record of vegetation and environmental conditions through the holocene and a substantial part of the late pleistocene radiocarbon dating suggests that the sequence covers tha last 51 000 yr or so high lake levels and the presence of forest or woodland vegetation indicate that the holocene and the basal few thousand years of the record experienced wet and warm conditions the earliest period was succeeded by a long phase of lower but variable moisture levels before more arid conditions resulted in the replacement of forest and woodland by herbaceous vegetation and frequent lake drying periods of slight amelioration occurred between about 27 000 and 19 000 and before 15 000 radiocarbon yr ago maximum aridity occurred between about 19 000 and 10 000 yr b p a period incorporating the height of the last glacial during the pleistocene the lake became gradually more saline but has been fresh during the holocene even under low lake levels an increase in charcoal values is recorded probably around 20 000 years ago and this could have resulted from increased burning as a result of the activities of aboriginal people this may have also caused a change in understorey vegetation from one composed largely of asteraceae to grassland the record is compared with others from southeastern australia and there is good correspondence through the last 20 000 or 30 000 yr but before this problems of dating and the condensed nature of most sequences prevent detailed correlation

the contributions of uranium thorium and marine palynology to the dating of the lake wangoom pollen record western plains of victoria australia abstract an extended pollen record from lake wangoom provides clear evidence for two climatic cycles incorporating three major effective precipitation peaks the existing radiocarbon dates and age estimates derived from uranium thorium dating and correlation with the pollen sequence from an isotopically dated marine record presented here provide conflicting chronologies for these cycles the radiocarbon dates indicate the youngest and middle precipitation peaks correspond respectively to the holocene and the last major interstadial oxygen isotope stage 3 by extrapolation the oldest peak correlates most closely with substage 5c uranium thorium disequilibrium dates suggest both the middle and oldest precipitation peaks occur within the isotope stage 5 complex the middle phase corresponding with an interstadial and the oldest with the height of the last interglacial the most reliable chronology at least for the later cycle is considered to be provided by comparison with the pollen record from a marine core with an oxygen isotope sequence from offshore victoria this record indicates that the last time precipitation levels attained those of the holocene was during the last interglacial period and suggests that the wangoom record extends back to the penultimate interglacial of isotope stage 7

the southern hemisphere westerlies in the australasian sector over the last glacial cycle a synthesis abstract the southern hemisphere westerlies in the southwest pacific are known to have waxed and waned numerous times during the last two glacial cycles though even semi continuous histories of the westerlies extend back no more than about 20 000 years we have good evidence for at least three scales of events a westerly maximum occurs at the last glacial maximum there is less conclusive evidence for another westerly maximum in the late holocene and for a minimum at ca 11 ka it is too early to ascribe even a cycle to these data but there are grounds to suggest that milankovitch precessional forcing may underlie the observed pattern there is also a quasi 2600 year cycle present in antarctic ice cores that appears to correlate to variation in westerly flow there is strong centennial scale variability in historical times the little ice age lia ca 1400 1850 was associated with a poleward shift in the circumpolar trough in the southern ocean strengthened westerly circulation over tasmania and a strengthening of southwesterly circulation and neoglaciation in southern new zealand while the preceding period 800 1400 ad was less certainly marked by reduced westerly flow from modern records we know that decadal and inter annual variability is important e g pacific decadal oscillation high latitude mode also known as the antarctic oscillation el nino southern oscillation only a minority of the proxies examined can identify changes on these temporal scales but data from tree rings ice cores and laminated lake sediments do indicate systematic changes in these phenomena through time rossby wave patterns are shown to play a critical role in long duration events as well as at the synoptic scale we conclude that westerly circulation is as strong now as at any time in the last glacial cycle in addition changes in latitudinal boundaries in the westerlies may be nearly as large in inter annual zonal shifts ca 2 maximum as in glaciation interglaciation movements ca 3 4 there is however reasonable evidence of strengthening weakening across much of the westerly belt at westerly maxima minima such as the lia early holocene

paleoenvironmental reconstruction using stable isotopes and trace elements from archaeological freshwater bivalve shell fragments in northwest patagonia argentina abstract stable oxygen and carbon isotopes 18o and 13c and the trace elements manganese mn and strontium sr were analyzed in archaeological bivalve diplodon chilensis shell fragments recovered from parque diana cave patagonia argentina to analyze the temporal trends of human occupation of the north patagonia forest with climatic conditions recorded at regional scale but poorly known at local scale for this site we established a stratigraphic sequence of thirteen 10 cm thick layers spanning the period c 2370 bp to c 580 bp and grouped these layers into three cultural components according to this region s climate with rain and snow concentrated in winter and dry summers our data suggest that these components are contemporary with three climatic periods a dry period indicated by high values of 18oshell 13cshell and sr ca ratio mn ca ratio does not show any significant trend in the lower component is associated with brief incursions of hunter gatherers from the eastern steppe in the middle component low 18oshell 13cshell and sr ca ratios suggest a humid climate with increased supply of meteoric and or melt water along with terrestrial plants organic matter and soil carbonates to the river according to the archaeological evidence in this period hunter gatherers from the pacific coast and forest started to colonize the area across the andes cordillera at the beginning of the upper component which is mostly contemporary with the expression of the medieval climatic anomaly mca the proxies are not totally coincident but a tendency to progressively drier conditions could be inferred except for layer 4 for 18oshell and layer 5 for sr ca ratio 18oshell 13cshell and sr ca ratio show consistently high levels in the upper than in the middle component in layer 5 18oshell and 13cshell are elevated with respect to the middle component while sr ca ratio remains low in layer 4 13cshell and sr ca ratio are high while 18oshell shows a negative peak in layers 3 to 1 18oshell 13cshell and sr ca ratio remain at high levels indicating an arid warm climate with high aquatic plant productivity in coincidence with the expression of the mca reported for this region in a partially contemporaneous period 1080 1250 ad at this time the occupation of the site by groups of the same origin as those present in the middle component became permanent extensive and intensive use of local resources in this period can be inferred from the quality and quantity of artifacts recovered

geochemistry δ13c δ15n 13c nmr and residence times 14c and osl of soil organic matter from red brown earths of south australia implications for soil genesis abstract soil forming processes important to the development of red brown earths duplex soils in southeastern australia have been investigated by a combination of techniques including isotopic 13c 15n 14c spectroscopic 13c nmr mir optically stimulated luminescence dating osl and phytolith analyses a distinct increase in clay content corresponding changes in the abundance of major elements as well as changes in organic chemistry 13c nmr stable isotope trends 13c 15n and phytolith abundance are apparent in the transition from the very sandy a horizon to the clayey b horizon in three soil profiles from the coonawarra padthaway region of south australia these structural and chemical changes between the a and the b horizons are associated with an abrupt increase in both 14c bulk soil organic matter and osl burial ages of individual quartz grains while previous interpretations have promoted the formation of duplex red brown earths as due to clay illuviation we propose a two stage soil formation which may be related to paleoclimatic changes during and after the last glacial maximum our data suggest that a major part of the a horizon was aeolian derived and was deposited over the last 10 000 years whereas much of the b horizon although originally aeolian has been extensively modified over much longer periods of time tens of thousands of years these results indicate the influence of different substrates sandy versus clayey process and time for formation as well as paleoclimatic history on the physical properties of the soil and the chemical characteristics of the organic matter within the soil profile

global omori law decay of triggered earthquakes large aftershocks outside the classical aftershock zone 1 triggered earthquakes can be large damaging and lethal as evidenced by the1999 shocks in turkey and the 2001 earthquakes in el salvador in this study earthquakes with ms 7 0 from the harvard centroid moment tensor cmt catalog are modeled as dislocations to calculate shear stress changes on subsequent earthquake rupture planes near enough to be affected about 61 of earthquakes that occurred near defined as having shear stress change 0 01 mpa the ms 7 0 shocks are associated with calculated shear stress increases while 39 are associated with shear stress decreases if earthquakes associated with calculated shear stress increases are interpreted as triggered then such events make up at least 8 of the cmt catalog globally these triggered earthquakes obey an omori law rate decay that lasts between 7 11 years after the main shock earthquakes associated with calculated shear stress increases occur at higher rates than background up to 240 km away from the main shock centroid omori s law is one of the few time predictable patterns evident in the global occurrence of earthquakes if large triggered earthquakes habitually obey omori s law then their hazard can be more readily assessed the characteristic rate change with time and spatial distribution can be used to rapidly assess the likelihood of triggered earthquakes following events of ms 7 0 i show an example application to the m 7 7 13 january 2001 el salvador earthquake where use of global statistics appears to provide a better rapid hazard estimate than coulomb stress change calculations

post 1906 stress recovery of the san andreas fault system calculated from three dimensional finite element analysis 1 the m 7 8 1906 san francisco earthquake cast a stress shadow across the san andreas fault system inhibiting other large earthquakes for at least 75 years the duration of the stress shadow is a key question in san francisco bay area seismic hazard assessment this study presents a three dimensional 3 d finite element simulation of post 1906 stress recovery the model reproduces observed geologic slip rates on major strike slip faults and produces surface velocity vectors comparable to geodetic measurements fault stressing rates calculated with the finite element model are evaluated against numbers calculated using deep dislocation slip in the finite element model tectonic stressing is distributed throughout the crust and upper mantle whereas tectonic stressing calculated with dislocations is focused mostly on faults in addition the finite element model incorporates postseismic effects such as deep afterslip and viscoelastic relaxation in the upper mantle more distributed stressing and postseismic effects in the finite element model lead to lower calculated tectonic stressing rates and longer stress shadow durations 17 74 years compared with 7 54 years all models considered indicate that the 1906 stress shadow was completely erased by tectonic loading no later than 1980 however the stress shadow still affects present day earthquake probability use of stressing rate parameters calculated with the finite element model yields a 7 12 reduction in 30 year probability caused by the 1906 stress shadow as compared with calculations not incorporating interactions the aggregate interaction based probability on selected segments not including the ruptured san andreas fault is 53 70 versus the noninteraction range of 65 77