comment on formation of chenier plain of the donana marshland sw spain observations and geomorphic model by a rodriguez ramirez and c m yanez camacho marine geology 254 2008 187 196 abstract the application of the regional marine 14 c reservoir effect r to obtain an accurate calibration of conventional marine shell 14 c dates requires prior research concerning the oceanographic conditions and the r of that region rodriguez ramirez and yanez camacho a rodriguez ramirez c m yanez camacho formation of chenier plain of the donana marshland sw spain observations and geomorphic model marine geology 254 2008 187 196 and afterwards a rodriguez ramirez j a morales j borrego and e g san miguel in a reply a rodriguez ramirez j a morales j borrego e g san miguel reply to the comment on formation of chenier plain of the donana marshland sw spain observations and geomorphic model by a rodriguez ramirez and c m yanez camacho marine geology 254 2008 187 196 marine geology 263 2009 123 125 to the comment by j rodriguez vidal f ruiz and l m caceres on the paper mentioned above j rodriguez vidal f ruiz l m caceres comment on formation of chenier plain of the donana marshland sw spain observations and geomorphic model by a rodriguez ramirez c m yanez camacho marine geology 254 2008 187 196 marine geology 263 2009 120 122 use in both cases not only incorrect r values for the calibration of 14 c dates obtained from shell samples collected from the east coast of the gulf of cadiz but they also confuse the r concept with that of r t the 14 c reservoir age because the misunderstanding of these concepts by these authors and in the first case also their failure to take into account the r values obtained by us and already published from the east coast of gulf of cadiz all the calibrated dates presented either in the first paper or in the reply cannot be accepted here i present a new calibrated dataset using accurate r values and i recommend that the conclusions obtained by rodriguez ramirez and their collaborators be revised as j rodriguez vidal f ruiz and l m caceres proposed in their comment

importance of small scale paleo oceanographic conditions to interpret changes in size of california mussel mytilus californianus late holocene santa cruz island california abstract several authors have highlighted the difficulties in disentangling human from natural effects when studying shellfish foraging strategies and archeo malacogical records in coastal settings one of the reasons for this difficulty is the lack of understanding of small scale oceanographic conditions and their influence on coastal and marine species used by people in the past the present study evaluated the influence of environmental conditions on shellfish harvesting during the late holocene around santa cruz island southern california considering small scale nearshore oceanographic variability around the island and its effect on m californianus main shellfish species exploited through prehistory along the coast of california fluctuations in size and abundance of m californianus shells through time and local past sea surface temperature sst values from oxygen isotope analysis of mussel shells are correlated throughout the stratigraphy of two shell midden sites 2200 500 cal b p nearby coasts with different paleo oceanographic characteristics despite the fact that human harvesting seems to have been the main force shaping length and availability of m californianus no clear evidence of human pressure was found on archaeological mussel assemblages results also show that fluctuations in regional sst records santa barbara basin marine core do not represent local sst variations oxygen isotope analyses on mussel shells especially if the archaeological site is located on a coast exposed to strong and consistent upwelling activity by re evaluating human impact on mussel beds during the late holocene around santa cruz island the research presented here demonstrates the importance of considering small scale nearshore oceanography for understanding the archaeological evidence of prehistoric human foraging on important intertidal shellfish species

radiocarbon dating of marine shell samples the marine radiocarbon reservoir effect of coastal waters off atlantic iberia during late neolithic and chalcolithic periods abstract radiocarbon dates on marine shells have not been used as extensively as charcoal or bone dates for the setting up of absolute chronologies because interpreting these dates is complicated by the marine radiocarbon reservoir effect nevertheless marine shellfish were used widely at least during the holocene and their shells are abundant and usually well preserved in archaeological deposits located near shorelines consequently prior research concerning the oceanographic conditions and the marine radiocarbon reservoir effect of a particular coastal area is needed in order to set up reliable chronologies for that region values of regional marine radiocarbon reservoir effect r of coastal waters off atlantic iberia some of its variability along the holocene and its correlation with the upwelling phenomenon were determined during previous research more data related to the r values for western portuguese coastal waters during the late neolithic and the chalcolithic a time interval badly sampled in previous research were recently obtained these values can be compared with r values already determined for the gulf of cadiz besides the importance of these values for a better knowledge of the palaeoceanography and palaeoclimatology of atlantic iberia from now on archaeologists can set up reliable chronologies for late neolithic and chalcolithic contexts using marine shell samples of that origin for radiocarbon dating

persistent late pleistocene holocene seasonal upwelling and varves off the coast of california abstract seasonal production of siliceous phytoplankton and a seasonal flux of terrigenous clastic material produced varved sediments along the continental slope off california during the late pleistocene to mid holocene light colored sediment within laminations and in sediment trap samples was deposited during summer upwelling and contains an abundance of the diatoms skeletonema costatum and chaetoceros spp resting spores dark colored sediment deposited in the fall and winter contains abundant thalassiosira pacifica and has more terrigenous material distribution of diatoms in varves shows that seasonal upwelling has persisted along the california coast and has remained strongly seasonal since the late pleistocene

accounting for the marine reservoir effect in radiocarbon calibration abstract the radiocarbon dating method is supported by highly refined calibration data empirically obtained from environmental archives nevertheless marine calibration remains problematic due to the spatiotemporally variable marine reservoir effect mre the currently accepted curve for radiocarbon calibration in the ocean is a global curve partly derived by numerical modelling from its atmospheric counterpart as such this curve cannot account for the effects of local phenomena strongly correlated with 14c signatures in seawater e g ocean dynamics and continental input although the radiocarbon community has suggested the use of regional calibration curves that would better represent the heterogeneous ocean reservoir a reasonable method for their construction has not yet been proposed we directly address this longstanding issue in radiocarbon research by exploring the output of a model for the temporal evolution of the mre the limitations of this model are inherited by our method and this hinders the use of the regional curves derived here in many regions of the world ocean nevertheless the approach described in this paper remains valid regardless of the chosen model and our preliminary results show that with the future development of accurate and highly resolved models for the mre this method may be a promising alternative to the use of r values in the process of marine calibration

mapping of subsurface shell midden components through percussion coring examples from the dundas islands following earlier examples of mapping the subsurface of shell bearing sites using augering we employ percussion coring to identify early holocene shell midden components at two types of sites on the northwest coast of north america we describe a method for mapping subsurface components at shell bearing sites including basal deposits paleosols and transitions between distinct cultural components our research was undertaken for the purpose of identifying early holocene shell middens above the modern shore and as components below large shell midden villages our results augment the developmental trajectory of shell middens on the northwest coast by suggesting that pre 5000 bp forms of these sites may be more common than previously thought in light of these results we argue that the northwest coast cultural historical sequence which locates an increase in the number and rate of accumulation of shell middens beginning 5000 years ago to be premature however there are insufficient data from shell middens in the early holocene a sampling problem that the percussion coring methods described here can address

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

late glacial to holocene changes in winds upwelling and seasonal production of the northern california current system abstract a core 120 km off the coast of southern oregon was examined for changes in lithology diatoms and pollen over the past 30 000 yr primary production during the late pleistocene was about half that of the holocene evidence from diatoms and pollen indicates that summer upwelling was much weaker implying an absence of strong northerly winds early pliocene diatoms found throughout the late pleistocene section were probably derived from diatomites east of the cascades and provide evidence for strong easterly winds over a dry continental interior the findings verify predictions of a climate model based on glacial maximum conditions there is no compelling evidence for a climatic reversal corresponding to the european younger dryas chron during the early holocene 9000 7000 yr b p there may have been years when winds were insufficiently strong to support upwelling so that warm stratified waters lay closer to the coast

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

stability in the south pacific surface marine 14c reservoir over the last 750 years evidence from american samoa the southern cook islands and the marquesas abstract although minor climatic and sea level changes have been documented for the south pacific during the late holocene our understanding of the consequent impact of these changes on the marine 14 c reservoir and therefore the 14 c content of shellfish is limited ultimately this has implications for documenting the chronology of human movement and adaptation in this region in this paper we compare marine reservoir r data obtained from tightly controlled archaeological proveniences with known age pre ad 1950 shells from the southern cook islands american samoa and marquesas islands results indicate that there has been no significant change in the near shore marine reservoir in these three locations over the last ca 750 years furthermore known age pre ad 1950 shell samples provide more precise r values for use in sample calibration than archaeological paired shell charcoal samples this is attributed in part to the limitations of assigning provenance and age to material from archaeological sites on the basis of these results we conclude that the known age pre ad 1950 shell derived r values can be used to calibrate shell 14 c results from deposits of late holocene age

late holocene δ13c and pollen records of paleosalinity from tidal marshes in the san francisco bay estuary california abstract records of stable carbon isotopes 13c are presented from cores collected from four san francisco bay marshes and used as a proxy for changes in estuary salinity the 13c value of organic marsh sediments are a reflection of the relative proportion of c3 vs c4 plants occupying the surface and can thus be used as a proxy for vegetation change on the marsh surface the four marshes included in this study are located along a natural salinity gradient that exists in the san francisco bay and records of vegetation change at all four sites can be used to infer changes in overall estuary paleosalinity the 13c values complement pollen data from the same marsh sites producing a paleoclimate record for the late holocene period in the san francisco bay estuary the data indicate that there have been periods of higher than average salinity in the bay estuary reduced fresh water inflow including 1600 1300 cal yr b p 1000 800 cal yr b p 300 200 cal yr b p and ca a d 1950 to the present periods of lower than average salinity increased fresh water inflow occurred before 2000 cal yr b p from 1300 to 1200 cal yr b p and ca 150 cal yr b p to a d 1950 a comparison of the timing of these events with records from the california coast watershed and beyond the larger drainage of the bay reveals that the paleosalinity variations reflected regional precipitation

radiocarbon dating and the old shell problem direct dating of artifacts and cultural chronologies in coastal and other aquatic regions abstract archaeologists have long recognized the problem of the old wood effect in radiocarbon dating charcoal and wood samples the age of which may be hundreds of years older than their use by humans such problems have resulted in significant changes in how most researchers select wood and charcoal samples for 14 c dating with many now using relatively short lived carbonized materials for dating despite the significant strides made in our understanding of the potential biases of the old wood effect little emphasis has been placed on the possible impacts of dating old shell in archaeological deposits the use of marine shell for 14 c dating is widespread in coastal areas around the world including a growing emphasis on the dating of individual shell artifacts via accelerator mass spectrometry ams in dating shell artifacts we have obtained several dates older than associated 14 c dates for short lived subsistence remains from the same deposits including great disparities 10 000 years and more subtle differences 100 years these discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts including shells collected from fossil deposits older archaeological sites and beaches the problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection analysis of multiple 14 c dates on a variety of materials and proper calibration procedures

measurement of significant marine paleotemperature variation using black abalone shells from prehistoric middens abstract the archaeological record from the last millennium in southern california indicates that a period of significant cultural change was associated with a reported marine paleoenvironmental disruption ca 1150 1250 a d a lengthy warm water anomaly may have in part precipitated more complex sociopolitical and economic responses we develop independent verification of the perturbation originally deduced from sediment core data using archaeological data respiratory pore number allometry in the black abalone shell is known to vary clinally in modern populations in response to temperature induced variation in rate of growth we use developmental trajectories of abalone from dated stratified archaeological deposits to reconstruct prehistoric seawater temperatures

implications of a freshwater radiocarbon reservoir correction for the timing of late holocene settlement of the elk hills kern county california abstract uncertainties regarding the magnitude of freshwater radiocarbon reservoir effects can introduce random errors into dates on archaeological freshwater carbonates as a result many archaeologists avoid dating freshwater shells unless no other datable materials are available the chronology of prehistoric occupation of the former naval petroleum reserve no 1 npr 1 at elk hills kern county has been established with 50 radiocarbon dates on freshwater mussels gonidea and anodonta sp characterization of any freshwater radiocarbon reservoir effect is crucial for the accurate interpretation of inferred settlement and subsistence changes on the elk hills paired charcoal and freshwater mussels sampled from closely associated contexts were dated to identify a freshwater reservoir effect paired anodonta and gonidea sp shells were dated to investigate interspecific differences in fractionation results indicate that a 340 20 14 c yr correction should be applied to conventional 14 c dates on freshwater carbonates in the buena vista basin before calendar calibration evidence of interspecific differences is inconclusive dates recalibrated with the reservoir correction indicate that widespread occupation of the elk hills is correlated with increasing precipitation towards the end of the medieval climatic anomaly and during the little ice age suggesting that slough resource exploitation may have been driven by regional population pressure rather than drought related declines in aquatic productivity

ancient long distance trade in western north america new ams radiocarbon dates from southern california abstract eleven olivella biplicata spire lopped shell beads from six sites located 250 365 km inland from the pacific coast of southern california produced ams dates between 11 200 and 7860 cal bp olivella shell beads were well documented items of prestige and media of exchange in native california and recovery of these examples from inland contexts indicates low level exchange between resident populations of the coast and the southwestern great basin by at least 10 300 10 000 cal years bp these findings represent some of the earliest unequivocal evidence for long distance trade in western north america and push the antiquity of this important form of inter group interaction back several thousand years earlier than previously thought

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

late quaternary relative sea level in southern california and monterey bay abstract few records of late quaternary relative sea level rsl are available for the pacific coast of north america south of san francisco bay a region where rsl data would be particularly useful for constraining vertical rates of tectonic motion this paper provides the first regional uplift corrected late quaternary rsl history for southern california derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore estuarine and freshwater deposits in sediment cores from coastal southern california we also provide a local uplift corrected rsl history for monterey bay central california generated from 48 radiocarbon ages from elkhorn slough and surrounding environments our resulting compilations show rapid sea level rise from 15 ka which begins to decelerate to present mean sea level pmsl between 6 and 8 ka late holocene

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

orbital suppression of wind driven upwelling in the california current at 6 ka 1 marine records clearly show activity in the california current cc system to have been altered during the mid holocene however the specific nature of cc activity during this period remains ambiguous as proxies that suggest cooler than present sea surface temperatures co occur in mid holocene marine sediments with multiple proxies that suggest decreased coastal upwelling to test the sensitivity of wind driven upwelling in the cc to mid holocene orbital forcing we have employed a high resolution regional climate model rcm the seasonality of modern cc wind driven coastal upwelling simulated by the rcm is in strong agreement with observational data further we show that changes in the seasonality of solar insolation induced by mid holocene milankovitch forcing decrease early and peak season coastal upwelling in the cc along with increasing late season coastal upwelling these results are in agreement with several marine and terrestrial proxies suggesting that relative to present cc activity during the mid holocene was characterized by a longer and less vigorous upwelling season with decreased seasonal contrast

quaternary sea level history and the origin of the northernmost coastal aeolianites in the americas channel islands national park california usa abstract along most of the pacific coast of north america sand dunes are dominantly silicate rich on the california channel islands however dunes are carbonate rich due to high productivity offshore and a lack of dilution by silicate minerals older sands on the channel islands contain enough carbonate to be cemented into aeolianite several generations of carbonate aeolianites are present on the california channel islands and represent the northernmost quaternary coastal aeolianites on the pacific coast of north america the oldest aeolianites on the islands may date to the early pleistocene and thus far have only been found on santa cruz island aeolianites with well developed soils are found on both san miguel island and santa rosa island and likely date to the middle pleistocene the youngest and best dated aeolianites are located on san miguel island and santa rosa island these sediments were deposited during the late pleistocene following the emergence of marine terraces that date to the last interglacial complex 120 000 yr to 80 000 yr based on radiocarbon and luminescence dating the ages of these units correspond in time with marine isotope stages mis 4 3 and 2 sea level was significantly lower than present during all three time periods reconstruction of insular paleogeography indicates that large areas to the north and northwest of the islands would have been exposed at these times providing a ready source of carbonate rich skeletal sands these findings differ from a previously held concept that carbonate aeolianites are dominantly an interglacial phenomenon forming during high stands of sea in contrast our results are consistent with the findings of other investigators of the past decade who have reported evidence of glacial age and interstadial age aeolianites on coastlines of australia and south africa they are also consistent with observations made by darwin regarding the origin of aeolianites on the island of st helena in the south atlantic ocean more than a century and a half ago

california current system response to late holocene climate cooling in southern california 1 new holocene high resolution planktonic foraminiferal assemblage data from santa barbara basin california documents variability in ocean circulation as the california current system responded to millennial scale climate change during late holocene climatic cooling climatic variability increased at 4 ka when a series of extreme cool events notably at 2 2 1 5 and 0 8 ka associated with glacial advance in the pacific northwest punctuated the predominantly warm holocene simultaneously high subtropical species abundance suggests increased interannual variability el nino frequency severity or greater seasonality during the late holocene planktonic foraminiferal assemblages indicate that the magnitudes of climatic shifts were greatest after 1 5 ka during an interval of extreme terrestrial hydrological variability in western north america and that the coolest interval of the holocene in santa barbara basin was coincident with the little ice age

temperature and currents on the southern california shelf a description of the variability abstract temperature and horizontal current observations at three water depths 15 30 and 60 m over the southern california shelf are reported for four discrete periods during 1978 79 roughly corresponding to each of the principal seasons the vertical structure of temperature changes markedly during the year the water over the shelf is weakly stratified in the winter n 50 cpd but stratification is stronger in the summer n 250 cpd seasonal changes in vertically averaged temperature are comparatively unimportant long term averages of the longshore currents are to the south near the surface in all seasons with amplitudes ranging up to 10 cm s 1 in the winter during spring and summer the stratification is accompanied by shear in the vertical structure of these long term current averages with surface currents sweeping to the south but with deeper colder water flowing in the opposite direction currents fluctuating at subtidal frequencies are predominantly alongshore and are strongest durin

high precision ams 14c chronology for gatecliff shelter nevada abstract gatecliff shelter provides a deeply stratified record of human environment interaction in the desert west spanning most of the middle and late holocene the well preserved 10 m deep deposits serve as an important reference sequence for technological and subsistence change in the great basin archaeological work started at gatecliff in 1970 and a geochronological framework was established based on 47 uncalibrated radiocarbon 14 c dates obtained from several conventional radiometric laboratories between 1972 and 1982 these radiocarbon dates are not well accommodated within a bayesian chronological model for these important deposits due to multiple temporal reversals and large analytical errors this model was discarded in favor of one based on a combination of high precision ams 14 c dates of short lived carbonized plant remains supplemented with existing 14 c dates culled from the original set using a bayesian chronological model summed probabilities of the modeled posterior distributions of these 14 c dates n 24 show episodic use of the shelter as a logistic hunting camp between 6050 and 3315 cal bp a significant hiatus in occupation between 3315 and 2145 cal bp and more persistent use by family bands after this time in the future this high precision chronology will provide the foundation for reinterpreting broader patterns of technological and subsistence change in the intermountain west and evaluating these changes relative to high resolution climate records

oxygen isotopic analysis of archaeological shells to detect seasonal use of wetlands on the southern pacific coast of mexico abstract oxygen isotopic ratios in modern and archaeological marsh clam shells polymesoda radiata from the acapetahua estuary in southwestern mexico record large scale salinity fluctuations caused by alternating wet and dry seasons thus prehistoric patterns of rainfall can be reconstructed and the season of molluscan death can be estimated changes in the oxygen isotopic patterns preserved in marsh clam shells from late archaic period c 3000 1800 bc archaeological deposits indicate that the season of shellfish harvesting changed dynamically through time in this region based on this study and other lines of archaeological evidence we argue that hunter gatherers during the early stages of the late archaic period visited locations in the littoral zone throughout the year with a focus during dry season months through the late archaic period a general trend occurred toward wet season use of these locations this culminated at the end of the late archaic period with the exclusive use of the littoral zone during wet season months these data indicate a fundamental shift in the way these estuarine locations were being used we argue that people living in this region altered their overall subsistence strategy during the late archaic period due to scheduling conflicts that occurred with the adoption of maize agriculture

the near surface dynamics of coastal upwelling abstract an attempt is made to examine some observational and theoretical aspects of upper ocean dynamics in regions of strong coastal upwelling upper ocean is roughly defined as about the upper 10 30 m of the water column for most systems first the basic surface ekman and mixed layers are discussed including some of the modifications due to upwelling next coastal upwelling fronts and their associated circulation are treated finally areas of strongly three dimensional upwelling are classified and discussed horizontal advection of heat and momentum appear to be generally important for the near surface dynamics of coastal upwelling and these phenomena make realistic theoretical treatments especially difficult

resolving varve and radiocarbon chronology differences during the last 2000 years in the santa barbara basin sedimentary record california abstract santa barbara basin sbb is well known for producing high quality paleoclimate reconstructions but the validity of correlations between the basin and other regions rests upon age model accuracy yet the two independent and well established chronologies based on varve counting and radiocarbon dating do not consistently agree during the last two millennia here the validity of age model assumptions is tested including whether 1 the regional reservoir age of surface waters was invariably 641 119 years through time and or 2 sbb laminae couplets are consistently annual varves and counted with sufficient precision this high resolution 14 c study of sbb sediments compares 49 mixed planktonic foraminiferal carbonate and 20 terrestrial organic carbon 14 c dates to the varve chronology to extend the high resolution paleoclimate chronology of the basin back 2000 years evidence indicates that regional reservoir ages do not remain constant through time with r i e regional reservoir age minus variations in the global mixed layer ocean reservoir age fluctuating between 80 and 350 years second there is a consistent r 2 0 96 undercounting of the varves between 150 and 1700 ad based on a new varying r 14 c chronology indicating that some laminae couplets may not be annual loss of varves may occur when low riverine input and infrequent winter storm activity during drought intervals fail to supply a siliciclastic layer

late quaternary climatic change on the american north pacific coast temporal changes in solar radiation caused by variations in the earth s orbit figure prominently in current quaternary climate theory1 4 experimental design of atmospheric circulation models emphasizes the importance of solar radiation in the heating of interglacial land and ocean surfaces at different seasons of the year whereby monsoon type circulation seasonal shifting of regional cyclonic and anticyclonic centres develops while during glacial ages seasonality is greatly modified by the influence of ice sheets5 7 we investigated the late quaternary climate of the north pacific where according to modelling solar radiation in the early holocene at the time of the summer solstice is high and in the late holocene is relatively low we compared quantitative temperature and precipitation estimates from southern alaska obtained by application of transfer functions to fossil pollen records with estimates from western washington8 and southern british columbia9 data extending over 10 000 years show a broadly consistent pattern of climatic change in general agreement with predicted variations in solar radiation and their effect on atmospheric circulation and seasonal duration of pressure systems over the north pacific ocean in the early holocene as monsoon type circulation became established with melting of glaciers the subtropical north pacific anticyclone annually regulated climate for a longer period at higher latitudes than at present so that warmth and dryness high summer radiation increased in southern alaska the aleutian low pressure centre locus of cyclonic storm activity intensified during the late holocene resulting in colder and more humid coastal climate low summer radiation over much of the year and increased frequency of glacier growth in the cordillera

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

shell midden sclerochronology abstract sclerochronological analysis of shell midden faunal remains offers a unique opportunity to study climate and environmental change in relation to human activity middens exist near most aquatic habitats almost worldwide for much of the late pleistocene and holocene they afford good preservation of accretionary calcium carbonate remains such as mollusk shells and fish otoliths in comparatively well dated contexts as such midden samples are a source of sequential proxy records of past climate and environmental conditions and may provide detailed pictures of human environment interaction however midden samples present several challenges to the development and application of sclerochronological proxies including unique taphonomic concerns here these challenges are outlined within descriptions of the major applications of midden sclerochronology archeological concerns including season of capture reconstructing the history of anthropogenic environmental impacts and paleoclimate environment proxy reconstructions

a numerical procedure for the solution of the steady state variable density groundwater flow equation a numerical code is developed for the solution of the three dimensional steady state groundwater flow equation in which groundwater density varies with spatial position and is treated as known spatially dependent parameter the integrated finite difference grid elements of the numerical code are rectangular when viewed along the vertical direction but their top and bottom surfaces parallel or are coincident with the interfaces between the geologic strata within the solution region conditions that are sufficient for the accuracy of the code are derived approximate solutions for pressure head as determined from the code are compared for accuracy with several exact analytic test solutions

holocene foraminiferal radiocarbon record of paleocirculation in the santa barbara basin differences in radiocarbon apparent ages between coexisting planktonic and benthic b p foraminifers in the santa barbara basin contain information about changes in the age and thus the source of water entering the basin the holocene sequence indicates a greater variability in circulation than previously detected during the early holocene ca 9 ka b p 1 4 c apparent age differences fluctuated between 220 and 560 1 4 c yr similar to rapid variations seen during the younger dryas and the last glacial episode during the relatively stable middle holocene 8 5 2 ka b p 1 4 c apparent age differences averaged 440 1 4 c yr after 2 ka the average b p 1 4 c apparent age difference increased to 620 1 4 c yr which has persisted until the present the shift in b p 1 4 c apparent age differences likely represents a change in the strength or source of north pacific intermediate water production and is concurrent with changes in regional climate patterns as well as with changes in temperature and accumulation rates measured in the greenland ice sheet project 2 ice core suggesting large scale changes in atmospheric circulation patterns

marine radiocarbon reservoir effect along the northern chile southern peru coast 14 24 s throughout the holocene abstract through an extensive sampling and dating of pairs of associated shells and charcoal fragments combined with reanalysis of all the available previous data we reconstruct the evolution throughout the holocene of the regional marine radiocarbon reservoir effect r values along the northern chile southern peru area 14 24 s after elimination of the cases in which the terrestrial component yielded older ages than the marine shells to which they were associated the study is based upon data from 47 pairs of associated marine and terrestrial material our results suggest major changes in both the magnitude and variability range of r during the whole holocene period 1 between 10 400 and 6840 cal yr bp high values 511 278 yr probably result from a strengthened se pacific subtropical anticyclone and shoaling of equatorial subsurface waters during intensified upwelling events 2 between 5180 and 1160 cal yr bp lower values 226 98 yr may reflect a major influence of subtropical water and diminished coastal upwelling processes 3 during the last thousand years high values between 355 105 and 253 207 yr indicate an increased influence of 14 c depleted water masses and of enso for the early twentieth century a r value of 253 207 yr was calculated