regional sea level southern oscillation and beach change new south wales australia coastal erosion is a problem of increasing concern that affects 60 of the world s sandy coastline1 this erosion has been attributed to increased storminess tectonic subsidence eustatic sea level rise decreased shoreward sediment movement from the shelf permanent longshore leakage of sediment from beach compartments shifts in global pressure belts resulting in changes in the directional component of wave climates and human interference2 3 no one explanation has worldwide applicability because all factors vary in importance regionally evaluation of factors is complicated by a lack of accurate continuous long term erosional data historical map evidence spanning 100 1 000 yr has been used in a few isolated areas4 7 however temporal resolution has not been sufficient to evaluate the effect of climatic variables air photographic evidence8 is restricted to the past 40 yr and often suffers from insufficient ground control for accurate mapping over time ground surveying of beaches was rarely carried out before 1960 and is often discontinuous in time and space i have resolved the problems of temporal and spatial continuity by studying change for the whole of stanwell park beach new south wales australia for the period 1895 1980 fig 1 i report here that using the average high tide wave run up position measured accurate to 2 5 m from oblique and vertical photographs changes could be linked to regional sea level variation and a globally significant climatic variable the southern oscillation so

deposition of harmattan dust and its influence on base saturation of soils in northern ghana ferruginous soils formed from volta shale deposits in northern ghana are highly weathered have high iron and aluminium oxide contents and a mineralogy dominated by quartz and low activity clays with low effective cec despite their advanced weathering state base saturation values of top soils are generally above 80 and deficiencies of basic cations are uncommon we postulated that the annual deposition of dust from the sahara carried by the harmattan weather system may be responsible for the high base saturation therefore we collected dust material for two entire dry seasons at nyankpala surrounded by highly weathered volta shale deposits and during several events of harmattan and local dust storms at bolgatanga surrounded by a variety of parent materials long distance harmattan dust had a clearly finer particle size distribution than dust collected during local storms but angularity and evidence of weathering on dust particles did not distinguish dust from different sources in bolgatanga soils contained unweathered minerals derived from local parent materials and both local storm and harmattan dust contained large amounts of bases significant amounts of micas and feldspars and k contents up to 3 in the dust collected at nyankpala showed harmattan dust to be the source of k and other bases found on volta shale soils short distance dust in nyankpala was mostly quartz and vegetation ashes dust deposition during one harmattan season at nyankpala amounted to about 15 g m 2 and carried a total of 140 400 300 and 60 mg m 2 of mg ca k and na respectively these amounts could account for the high base saturation of the low cec in volta shale soils

coastal barriers nomenclature processes and classification issues abstract the designation coastal barrier related terms and their varied interpretations and critical concepts in coastal plain and nearshore geology underwent numerous reincarnations over the years this designation was first applied to shore parallel sand and gravel built ocean front islands and spits that separate open marine environments from paralic inshore environments that they shelter a more recently recognized third category includes mainland strandplain chenier and dunefield barriers either as original components of mainland coasts or subsequently welded to the coastal plain a parallel but closely related terminology developed mostly in australia and brazil identifies several specific process categories recognizable in the three basic barrier groups in the absence of lagoons and tidal wetlands shore ridges that front and are contiguous with the mainland coastal plain have been mistakenly assigned to the barrier island category greatly diminished wave energy and consequently minor littoral drift volumes account for the relative rarity and much smaller dimensions of prograded landforms in estuarine islands and bay shore beaches in paralic inshore basins due to wave and related littoral drift processes however diminished in comparison with open marine shores morphological similarities between aggraded landforms of open marine through estuarine settings are to be expected however the multitude of proposed fetch limited diminished wave energy estuarine islands characterized by diminutive narrow beaches sand spits even occasional small dunes and miniature strandplains lack the essential functional attributes intrinsic to true barrier islands while barrier islands may form even on relatively low wave energy and or sediment deficient marine shores the term is inappropriate for islands located in low energy paralic basins including estuaries or in coastal plains where frontal shore ridges are not backed by lagoons landforms erroneously ascribed in a variety of facies settings as barrier islands or islands frequently are mainland attached beach ridge plains or beach fringed marshlands instead narrow marshland beaches and mainland strandplain barriers are segmented into short islands by intervening narrow tidal creeks fluvial distributary channels or storm cuts that separate them improved fundamental and functional definitions of barrier islands their comparison with the many genetic categories of islands and mainland shore beaches found in estuarine basins and wetlands should lead to a better understanding of paralic island evolution processes on the global scale

evidence for late quaternary sea level change around st helena island south atlantic summary the evidence presented by daly 1927 for a 3m raised shoreline along only the northwest coast of st helena and its implied absence elsewhere on the island is reappraised in the light of recent fieldwork low benches and abandoned caves have been found preserved on all coasts and are at a greater variety of elevations than supposed previously the morphology of the benches and processes presently affecting them are described and three types of raised beach identified it is argued that the low level features represent three periods of marine erosion to 7 0 9 0 m 3 0 4 5 m and 1 5 2 0 m each attributable to a sea level relatively higher than the present one

coastal environmental changes associated with holocene sea level fluctuation southeastern buenos aires argentina abstract sea level was 2 m higher than present 6000 years ago at southeastern buenos aires province argentina this fluctuation has caused several environmental changes including drift reversal geomorphological features and radiocarbon dating suggest that the mar chiquita barrier grew from north to south during the regression from 4000 years bp in contrast mineral dispersals coastal defenses inlet migrations and wave statistics show that present beach drift is to the north in the same direction as storm induced shelf sediment transport coastal mollusk mass mortalities lagoonal deposits that accumulated during the regression contain abundant remains of mactra isabelleana tagelus plebeius and labiosa plicatella these species are rare in present coastal lagoons many causes have been proposed for the absence of these species in present lagoons and include sudden sea level decline outlet obstruction producing variation in salinity and increased fluvial freshwater inputs the regional character of these mortalities and growth curves indicates that taphonomic feedback processes related to the scarce 2 m involved in the transgressive regressive cycle are the reason for mollusk mortality sand consumption during the latter stages of the holocene transgression sand ramps up to 10 m height at mar del plata cliffs and sand barriers up to 2 km width north of mar chiquita village developed as a result of high wave energy and a plentiful sand supply the subsequent regressive phase produced lagoons tidal flats marshes and cheniers the alongshore growth of barriers meaned their cannibalization misfit foredunes and narrowing driftwards these processes occurred before the drift reversal mentioned above

study on ultra deep azimuthal electromagnetic resistivity lwd tool by influence quantification on azimuthal depth of investigation and real signal this paper proposes a new tool design of ultra deep azimuthal electromagnetic em resistivity logging while drilling lwd for deeper geosteering and formation evaluation which can benefit hydrocarbon exploration and development first a forward numerical simulation of azimuthal em resistivity lwd is created based on the fast hankel transform fht method and its accuracy is confirmed under classic formation conditions then a reasonable range of tool parameters is designed by analyzing the logging response however modern technological limitations pose challenges to selecting appropriate tool parameters for ultra deep azimuthal detection under detectable signal conditions therefore this paper uses grey relational analysis gra to quantify the influence of tool parameters on voltage and azimuthal investigation depth after analyzing thousands of simulation data under different environmental conditions the random forest is used to fit data and identify an optimal combination of tool parameters due to its high efficiency and accuracy finally the structure of the ultra deep azimuthal em resistivity lwd tool is designed with a theoretical azimuthal investigation depth of 27 42 29 89 m in classic different isotropic and anisotropic formations this design serves as a reliable theoretical foundation for efficient geosteering and formation evaluation in high angle and horizontal ha hz wells in the future

archaeological littoral sites on the northern coast of santa cruz valuable evidence of sea level changes on the continental patagonian coasts argentina geological studies are fundamental to archaeologists as they provide essential data to understand certain processes involved in the present archaeological record when working on marine coastal archaeology the information provided by geomorphologic studies with regards to the evolution and dynamics of coastal marine lines is essential to assess the availability and accessibility of certain marine coastal areas and their resources to human populations of the past this is also the key to reach correct cultural interpretations however on certain occasions archaeological information can also offer valuable alternative data for geologists to reach geological interpretations for instance when working on the evolution and changes of coastal sea lines in this case spatial and temporal scales must be regarded this idea is supported on the experience gained through research done on the patagonian atlantic coast at the two archaeological localities introduced in this paper cabo blanco where we evaluate models of evolution of the coastline with a number of radiocarbon dates from excavated sites and punta medanosa where we discuss the temporal depth of the formation of the coastal ridges for the mid holocene transgression

evidence for smoothly falling sea level relative to north queensland australia during the past 6 000 yr post glacial sea level curves are expected to differ between different parts of the world as a result of global isostatic changes1 or perhaps other forms of geoidal changes2 i report here results from the inner part of the northern great barrier reef which seem to show a pattern of smoothly falling sea level during the past 6 000 yr the results are consistent with stratigraphical results from prograded mangrove coasts on the nearby north queensland mainland the region is remote from the tectonically active margin of the south west pacific ocean and the results contribute to the global data set relevant to isostatic changes being assembled by the international sea level project igcp project no 61 they also provide a baseline relevant to holocene coral reef growth in the inner great barrier reef

sea level fluctuations during the last 8600 years in the de la plata river argentina abstract the de la plata river considered from the geomorphologic point of view can be defined as a unit composed of a set of features genetically linked together which were formed as a result of the post last glacial maximum transgression regional stratigraphical morphological and topographical studies carried out in the de la plata river and surrounding areas of eastern argentina determined that the holocene evolution of the area was the result of processes resulting from relative sea level fluctuations in order to date the different stages of evolution a curve of sea level fluctuations was constructed after a selective choosing of samples with reliable ages supported by field geological evidence the curve shows a rapid initial transgressive event and the maximum highstand of mean sea level at 6000 yr bp at a relative elevation of 6 5 m above present the following regressive event was characterized by a discontinuous fall in sea level geomorphological evidence suggests that sea level fall could have experienced minor changes in rate as well as moments of stability that are not shown by the curve short interruptions in the geological record can be explained either by the same minor changes in sea level or by a change in wave regime correlation of transgressive regressive events with paleoclimatic and biogeographic information proposed that holocene sea level fluctuations in the de la plata river were mainly controlled by climatic changes

late quaternary glacial history of george vi sound area west antarctica during the last glacial maximum in west antarctica separate ice caps developed on alexander island and on palmer land became confluent in george vi sound and discharged northward from latitude 72 s radiocarbon 32 000 yr and amino acid approximately 120 000 yr age determinations on shell fragments hiatella solida found in basal till suggest a wisconsin age for the glaciation that incorporated them the pattern of ice flow differed from that deduced for this area in the climap reconstruction following the maximum stage there was a stadial event when outlet valley glaciers flowed from smaller ice caps into george vi sound more widespread recession permitted the george vi ice shelf to deposit palmer land erratics on eastern alexander island before isostatic recovery raised them to final elevations of about 82 m the ice shelf may have been absent at about 6500 yr b p when large barnacles bathylasma corolliforme were living in the sound small glaciers readvanced to form at least two terminal moraines before the ice shelf re formed and incorporated the barnacle shells into its moraine on alexander island the shells gave a 14c age corrected for antarctic conditions of about 6500 yr b p and an amino acid ratio consistent with a holocene age valley glaciers readvanced over the ice shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice cored moraines probably during the little ice age such oscillations may represent a climatic control not yet observed in the dry valleys of victoria land the only other part of antarctica studied in detail for glacier fluctuations

holocene mangrove dynamics and relative sea level changes along the tanzanian coast east africa abstract there is continued uncertainty regarding the rate timing duration and direction of holocene sea level for the indian ocean and indeed the wider tropical realm we present the first synthesis and a new chronology for holocene relative sea level rsl using a range sediment cores retrieved from mangrove ecosystems in three locations along coastal tanzania this study applies the relationship of ratios between the key mangrove taxa of sonneratia bruguiera ceriops s bc ranging from 0 to 22 9 and sonneratia rhizophora s r ranging from 0 to 2 29 vegetation and altitude to interpret mangrove dynamics and refine the vertical errors associated with relative sea level change the variations in mangrove taxa ratios in the sediment cores obtained from each site shows mangrove development at different periods during the holocene from around 7900 cal yr bp an early to mid holocene rsl rise occurred from 7900 to 4600 cal yr bp that may have reached a higher level than present a lower rsl occurred after 4600 cal yr bp resulting in mangroves retreating seaward at all three study locations before a low magnitude rsl rise occurred between 4400 and 2000 cal yr bp another rsl rise is recorded at 500 cal yr bp before falling to a level lower than present at 100 cal yr bp there is evidence of a recent rsl rise recorded from mangrove ratios during the last century in addition the sedimentation rates among sites are relatively different due to different altitudinal ranges with freshwater input sediment supply and progradation having significantly more effect in the rufiji delta 2 1 10 9 mm cal yr 1 than at the zanzibar sites 0 3 6 6 mm cal yr 1

palaeoenvironmental conditions during the early peopling of southernmost south america late glacial early holocene 14 8 ka b p abstract environmental conditions in southernmost south america the patagonian andes and the extra andean plains during the early peopling of the region in late glacial early holocene times are herein described different glacial advances or stabilization phases in valley glaciers occurred several millennia after the last glacial maximum lgm as a consequence of regional cold climatic episodes according to clapperton 1993 two advances during the late glacial took place ca 15 14 14 c ka and 12 10 14 c ka b p a cold event during this last period probably correlative with the younger dryas episode in the northern hemisphere has been observed in the palynological record a tundra environment dominated until ca 13 10 14 c ka b p afterwards a gramineous steppe with forest refuges developed the transition steppe forest lasted to the middle holocene when the nothofagus forest took over the arrival of man in southernmost south america ca 13 14 c ka b p or even before probably took place while glaciers were still present in most andean valleys sea level was much lower than today and tundra environments dominated the extra andean plains moreover peopling in the isla grande de tierra del fuego would have occurred not later than 11 8 14 c ka b p when the present magellan straits valley was still occupied by a meltwater discharge braided stream fed by the receding magellan glacier

late holocene sea level changes in the northwest tuamotu islands french polynesia abstract field surveys of several sea level indicators exposed in situ reef framework conglomerates coral colonies and tridacna shells in a growth position sea corrosion notches carried out on six atolls from the nw tuamotus mataiva rangiroa arutua kaukura apataki and takapoto and data from four subsurface boreholes drilled through mataiva show that during the late holocene mean sea level msl reached a maximum elevation at approximately 0 9 m it remained above the present msl from between 6000 and 5500 yr b p until at least 1200 yr b p human settlements on the atolls were extremely unlikely and probably impossible throughout this time the area investigated seems to have been tectonically quite stable during the late holocene a local curve of msl variations may be representative of the regional eustatic pattern

historical changes in the shoreline and littoral processes on a headland bay beach in central chile abstract we applied parabolic and logarithmic adjustments and methods of cartographic overlay to the sandy littoral of concon bay central chile to determine the changes associated with the shoreline and their relation with littoral processes in a typical bay on an active continental margin and with a microtidal regime a set of historical reference points was built by means of aerial photographs and topographies for the period 1945 2008 given the form of the shoreline to the southern section of the bay we applied the classical logarithmic formula of yasso 1965 and the functions incorporated in the coastal modeling system sistema de modelamiento costero smc of the universidad de cantabria in the northern section a method of map overlay was applied the oluca sp model of the smc was used to determine the influence of waves refraction on the types of changes of the shoreline information on waves 1985 2006 mean sea level 2001 2006 and variations in the mean size of beach sediment were used to relate the changes in the plan form of the bay there has been little spatio temporal variability in the shoreline of the bay over the last 65 years the southern section had a mean shoreline retreat rate of 0 55 m year 1945 2008 in spite of the large variability produced in an estuary dominated by waves the best adjustment was obtained with the logarithmic function in the northern section the mean accretion rate was 0 39 m year 1954 2008 the plan form and the historical changes of the shoreline are closely associated with the seasonal changes of the waves and the presence of rocky thresholds in the area the mean sea level did not produce important effects in the types of change

holocene sea level changes along the strait of magellan and beagle channel southernmost south america abstract radiocarbon dated marine sediments from five coastal sites along the strait of magellan and beagle channel in southernmost chile permit construction of a curve of relative sea level fluctuations during the holocene morphologic and stratigraphic data point to coastal submergence during the early holocene as the sea rose to a maximum level at least 3 5 m higher than present about 5000 yr ago progressive emergence then followed during the late holocene data from widely separated localities define a smooth curve the form of which is explainable in terms of isostatic and hydroisostatic deformation of the crust resulting from changing ice and water loads apparently anomalous data from one site located more than 100 km behind the outer limit of the last glaciation may reflect isostatic response to deglaciation the sea level curve resembles one derived by clark and bloom 1979 in proceedings of the 1978 international symposium on coastal evolution in the quaternary sao paulo brasil pp 41 60 sao paulo using a spherical earth model both in amplitude and in the timing of the maximum submergence

early holocene bone technology at the la olla 1 site atlantic coast of the argentine pampas abstract la olla 1 in the pampas of argentina is an open air site located on the atlantic coast in the monte hermoso district southern buenos aires province bones in lacustrine layers outcrop during very low tide exposed by longshore drift based on an initial analysis of the faunal assemblage two species of sea mammal guanaco pampean deer greater rhea and a fish were represented in the almost 300 bones recovered during the rescue excavation the lithic assemblage consisted of unifacially flaked tools rounded cobbles reduced by bipolar technique flakes and artifacts with flat abraded surfaces radiocarbon determinations of c 7300 and 6600 bp came from sea mammal femora an informal bone tool recovered from the site is made from the left proximal tibia of an adult otariid it is identified as a utilitarian bone tool on the basis of use wear characters that are restricted in distribution and as a fracture based bone tool on the basis of technological characters the element was dynamically impacted in the mid diaphysis region use wear characters are loss of edge angularity microflaking pitting striae and polish microflaking occurs along the posterior fracture surface and exterior adjacent cortical surface pitting of the fracture surface extends along the entire length of the worn edge but is most concentrated along the posterior fracture surface a multitude of very fine striae runs parallel to the fracture edge the area of striations is limited to this edge with a well demarcated boundary covering all of these characters is differential wear polish this high gloss polish is strongly reflective and occurs over very worn and rounded areas providing a very bright melted appearance based on these different use wear patterns the la olla 1 bone tool is interpreted as a dual purpose implement most likely used for carcass dismemberment and hide processing the la olla 1 tool is unusual in that it is made from pinniped bone biomechanical analysis of southern fur seal bone indicates however a strong suitability for impact related tasks and therefore an appropriate choice for use as butchering tools

palaeoenvironmental evolution and sea level fluctuations along the southeastern pampa grasslands coast of argentina during the holocene holocene pollen and diatom analyses and complementary data from 18o and 13c malacology and sedimentology have provided a detailed record of vegetation history and palaeoenvironmental change at arroyo las brusquitas on the southeastern coast of the pampas of argentina especially in relation to past sea levels holocene palaeosalinity trends were estimated by detrended correspondence analysis and by salinity indexes based on pollen and diatom data as a consequence of sea level rise from the postglacial an extensive wave cut platform formed over which holocene infilling sequences were deposited unconformably in these sequences variation in pollen and diatom assemblages occurred in agreement with changes in mollusc diversity and abundance isotope values and sediment deposits between ca 6700 and 6190 14c yr bp 6279 6998 cal yr bp saline conditions predominated in an environment highly influenced by tides and salt water during the holocene sea level highstand between ca 6200 and 3900 14c yr bp 4235 4608 cal yr bp shallow brackish water bodies formed surrounded by saltmarsh vegetation that became more widespread from 5180 14c yr bp 5830 6173 cal yr bp to 3900 14c yr bp in relation to a sea level stabilisation period within the regression phase less saline conditions marked by frequent variations in salinity predominated between ca 3900 and 2040 yr 14c bp 1830 2160 cal yr bp the intertidal saltmarsh environment changed into a brackish marsh dominated by freshwater conditions and sporadic tidal influence halophytic vegetation increased towards ca 200014c yr bp indicating that saline conditions may be due to either desiccation or an unusually high tide range with rare frequency after ca 2000 14c yr bp the sedimentary sequences were buried by aeolian sand dunes changes in holocene vegetation and environments in las brusquitas area are in agreement with data obtained from various southeastern coastal sites of the pampa grasslands copyright 2005 john wiley sons ltd

glacial isostatic adjustment and the free air gravity anomaly as a constraint on deep mantle viscosity summary a gravitationally self consistent theory for relative sea level variations forced by pleistocene deglaciation events is employed to explore the extent to which rsl and free air gravity observations together constrain the viscosity of the mantle beneath the seismic discontinuity at 670 km depth a trade off is revealed between errors in the assumed deglaciation history and errors in the inferred value of the viscosity of the lower mantle taking full account of such uncertainty plausible values of the viscosity beneath the transition region are bounded above by 1023 poise cgs units the preferred value is at least a factor of 2 lower than this and is strongly constrained by the observed free air gravity anomaly over hudson bay the calculations described in detail here show for the first time that the relatively large gravity anomalies observed over sites of wurm wisconsin deglaciation do not require any pronounced increase of mantle viscosity with depth in order to explain them

mid to late holocene evolution of transgressive dunefields from rio grande do sul coast southern brazil abstract the aim of this paper is to examine the dunefield evolution of the rio grande do sul rs coastal stretch from torres to mostardas which presents progradational aggradational and retrogradational barriers the stratigraphy and sedimentary facies of 26 cores along 9 profiles were analyzed the stratigraphy of the cores along the profiles agreed with the suggested barrier types the northern area comprises prograded barriers in jardim do eden and magisterio retrograded barriers in dunas altas an aggradational barrier and the southernmost profiles solidao sao simao and mostardas retrograded barriers three major periods of soil formation and dunefield stabilization were found from 4820 to 3970 cal yr bp in 2760 2460 cal yr bp and from 1570 to 710 cal yr bp these periods coincide with periods where the literature cites an increase in moisture during the mid to late holocene this coincidence of soil formation and wet climate indicates that the climate might be controlling dunefield evolution on the rs coast since 5000 yr bp the stratigraphic data of the three most representative cores were correlated and along with the available ages from palaeosols and the facies descriptions 10 phases of aeolian activity and stabilization were recognized for the mid littoral of rs

holocene sea level history evidence from coastal sediments of the northern rio grande do norte coast ne brazil the holocene sea level history of the mesotidal northern rio grande do norte coast ne brazil was reconstructed from sedimentology and ams radiocarbon dating of beachrock and tidal lagoonal sediments at 7000 cal year bp at 3 m sea level stood and passed the modem sea level 6700 cal year ago the holocene highstand reached 1 3 m above modem sea level at 5900 cal year bp as determined by beachrock samples from the uppermost part of an intertidal foreshore deposit a 5700 cal year old shell midden overlies this beachrock that represents the spring tide sea level after the highstand sea level dropped to its present position beachrock samples from intertidal upper foreshore deposits were used for elevation and age control beachrock positions with their error bars are all within the tidal range envelope therefore no secondary oscillations during the sea level fall can be confirmed a linear sea level fall of this magnitude can be explained by the mechanism of equatorial ocean syphoning c 2005 elsevier b v all rights reserved

assessing links between late holocene climate change and paleolimnological development of pena lagoon using opal phytoliths physical and geochemical proxies abstract opal phytolith geochemical and sedimentological data from two cores taken in pena lagoon a small water body on the atlantic shore of uruguay are presented in this paper the choice of this specific sampling location aimed to obtain high resolution records to infer late holocene environmental and climatic changes in southeastern uruguay in order to improve previous models for early and middle holocene the combined record of two cores extends to 2500 14c bp with a sedimentation rate ranging between 0 6 and 2 mm y 1 a multiproxy approach allowed the identification of changes in dynamics particularly organic matter and sediment input variability from the watershed with this information differences in the amount and extent of environmental signals were evaluated and a comprehensive climate change model was generated especially for the last 1500 years three main climatic events were distinguished the oldest which lasted until 700 ad was characterized by temperate and humid conditions the second extended until 1200 ad and warmer and wetter conditions were inferred but also a colder and drier pulse was observed in between this second event was assigned to the warm medieval period wmp during the third event assigned to the little ice age lia which extended until the present a high variability in climate was observed but also three dry cold phases reaching their maxima by 1300 1600 and 1900 ad were inferred

holocene coseismic and aseismic uplift of isla mocha south central chile abstract during the past 6000 years isla mocha a 12 km long island 30 km off the coast of south central chile experienced a 38 m fall of relative sea level caused primarily by rapid tectonic uplift of the island as many as 18 raised shorelines strandlines record this uplift historic accounts of uplift during the great earthquakes m 8 of 1835 and 1960 suggest some of the more prominent prehistoric strandlines also emerged during great earthquakes on the interface between the nazca and south america plates but the close elevational spacing of strandlines subdued morphology of strandline beaches scarcity of exposed bedrock wave cut platforms and the extremely high rates of aseismic uplift ca 70 mm yr of the island since the last great earthquake suggest that many strandlines were raised by aseismic rather than coseismic uplift strandline heights and 14 new radiocarbon ages on marine shells show that the present day uplift rate is more than three times the net rate ca 20 mm yr of the past 1000 years the recent high rate probably reflects increased aseismic slip on an inferred thrust fault in the overriding south america plate isla mocha overlies an area of high stress concentration between two major segments of the chilean subduction zone the inferred high rate of slip on the thrust fault may be a response to stress changes on the plate interface near the boundary between the segments

holocene raised beaches along the northern coast of the beagle channel tierra del fuego argentina abstract raised beaches developed during holocene times along the northern beagle channel coast these deposits contain a rich marine fauna especially shelled organisms such as mollusks four holocene marine sites along the northern coast of the beagle channel have been analysed from west to east they are bahia ensenada playa larga bahia brown and cutalataca airfield they were studied in relation to relative altitude sediment type faunal composition and radiocarbon dates the area is characterized by several discontinuous terraces with elevations varying from about 1 5 to 10 m above sea level their possible origin 1 due to tectonic uplifting in comparison with raised beaches of the northern part of tierra del fuego and 2 resulting from glacio isostatic recovery taking into account the ice retreat is discussed seventeen species of mollusks eight bivalves nine gastropods were collected from the study sites all of them are living species from the beagle channel and have been interpreted as representative of holocene paleocommunities in this channel these species show no evidence of substantial climatic changes during the holocene although minor temperature fluctuations cannot be ruled out yet

middle late holocene palynology and marine mollusks from archipielago cormoranes area beagle channel southern tierra del fuego argentina abstract the palynology and marine mollusks of a marine sequence from rio ovando 54 51 s 68 35 w archipielago cormoranes beagle channel has been studied in order to reconstruct paleoenvironmental conditions during the middle late holocene the dinoflagellate cyst assemblages from rio ovando sequence reflect fjord estuarine environments close to terrestrial ice field affected by glacier meltwater discharge and characterized by short term oscillations of sea surface water parameters the base of the section which is dated at about ca 4160 14 c yr b p 4736 cal yr b p palynological subzone ro 2c is characterized by a high species diversity of dinocyst and mollusks and it is immediately followed by an interval palynological subzone ro 2b characterized by the presence of the echinidinium islandinium complex and the monospecific mytilus mollusk assemblage this subzone registers an inverse correlation between nothofagus dombeyi type and echinidinium islandinium complex concentration values during ca 4160 14 c yr b p 4736 cal yr b p 4064 14 c yr b p 4540 cal yr b p suggesting a variable climatic condition probably related to neoglacial episodes occurred in the southern patagonia andes during this interval the pollen assemblages permit direct correlations with the onshore palynostratigraphy from southern of tierra del fuego the high percentages of nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest confirming the existence of a variable cool and wet climate for the archipielago cormoranes area during the middle late holocene

holocene sea level fluctuation in the southern hemisphere abstract if rising sea levels dominate in the northern hemisphere nh falling or fluctuating sea levels predominate in the southern hemisphere sh endogenic processes tectonics isostasy or geoidal changes could explain local or regional mean sea level msl fluctuations but not an hemispherical one evidence from south america africa antarctica australia and the pacific and indian oceans suggest that the holocene transgression rose above the present msl in higher latitudes before the tropics by plotting latitude against the age of msl arrival at present coasts good correlation is observed oceanic salinity mixing has been already proposed to explain this mid holocene sea level fluctuation climate could be the only factor responsible for this hemisphere wide behavior of msl it has been suggested previously that the climate of the sh precedes that of the nh by 3000 years the climatic optimum or maximum warmth occurred predominantly about 6000 bp in the nh but about 10 9000 bp in the sh short term climatic effects on the sea level monsoons southern oscillation el nino phenomena should have significant occurrences during the past in the windiest oceanic hemisphere this latitudinal trend in former msl should be considered when using shorelines as reference points for measuring vertical crustal movements

lithospheric thickness antarctic deglaciation history and ocean basin discretization effects in a global model of postglacial sea level change a summary of some sources of nonuniqueness the global model of postglacial relative sea level variations that has been developed over the past decade is employed to investigate the constraints that it may be invoked to place on the timing of the deglaciation of west antarctica the analyses presented here confirm the suggestion of p wu and w r peltier 1983 geophysical journal of the royal astronomical society74 377 450 that the model of this event employed inj a clark and c s lingle 1979quaternary research11 279 298 may be simply modified to rectify the misfits between theory and observation that are otherwise obtained at southern hemisphere sites a large number of southern hemisphere relative sea level data are shown to require that the retreat of antarctic ice substantially lagged the retreat of northern hemisphere ice if the deglaciation of antarctica was abrupt the time of onset of antarctic deglaciation is thereby shown to coincide with the time of most rapid northern hemisphere deglaciation sensitivity tests are performed which demonstrate that this result is relatively insensitive to the discretization employed to represent the ocean basins the only exception to this general rule obtains at some coastal sites at which a trade off is revealed between the delay of west antarctic melting and the thickness of the lithosphere required to reconcile the observed local variations of relative sea level at such sites which are all in the far field of the ice sheets some attention must be paid to the accuracy of the local finite element representation of the oceans and to the details of the antarctic deglaciation history

the brazilian sea level curves a critical review with emphasis on the curves from the paranaguaand cananeia regions abstract relative sea level curves for the mid to late holocene have been proposed for eight different sectors along the brazilian coast this paper aims to review the data used to construct the curves proposed for two sectors the paranaguaand cananeia regions in southeast brazil more specifically we analyze the palaeo sea level indicators vermetid tubes shells wood fragments and shell midden deposits related to 1 the sea level maximum of the mid holocene and 2 the two secondary oscillations that would have occurred between 4100 3800 years b p and 3000 2700 years b p the sedimentary deposits of the coastal plain as well as vermetid datings suggest a mid holocene sea level maximum between 3 5 and 4 m the great majority of the indicators used to infer the secondary oscillations in previous studies were derived from shell middens besides being unreliable palaeo sea level indicators these data also showed inconsistencies that undermine the existence of such oscillations the plot of all the data derived from vermetid samples found along the brazilian coast also indicate a rather smoother sea level fall in the last 5100 years