direct determination of the timing of sea level change during termination ii an outcrop within the last interglacial terrace on barbados contains corals that grew during the penultimate deglaciation or termination ii we used combined 230th and231pa dating to determine that they grew 135 8 0 8 thousand years ago indicating that sea level was 18 3 meters below present sea level at the time this suggests that sea level had risen to within 20 of its peak last interglacial value by 136 thousand years ago in conflict with milankovitch theory predictions orbital forcing may have played a role in the deglaciation as may have isostatic adjustments due to large ice sheets other corals in the same outcrop grew during oxygen isotope 18o substage 6e indicating that sea level was 38 5 meters below present sea level about 168 0 thousand years ago when compared to the 18o signal in the benthic v19 30 v19 28 record at that time the coral data extend to the previous glacial cycle the conclusion that deep water temperatures were colder during glacial periods

hurricanes and climate in the caribbean during the past 3700 years bp a multiproxy analysis of lacustrine sediments cored in grand case pond at saint martin north of the lesser antilles archipelago reveals three distinct climatic periods for the last 3700 years from 3700 to 2500 yr cal bp and from 1150 yr cal bp to the present carbonate mud deposition occurred in connection with pond lowstands these periods were also punctuated by severe drought events marked by gypsum laminae and hurricane landfalls leading to marine sand inputs into the pond the intermediate time interval from 2500 to 1150 yr cal bp is typified by black organic mud deposition suggesting that hypoxic to anoxic conditions prevailed at the pond bottom these were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today the carbon isotopic composition of the ostracod perissocytheridea bisulcata shows that the lowest 13c values are recorded during the hypoxic periods as a consequence of bacterial recycling of isotopically depleted org

the belize margin revisited 1 holocene marine facies belize is best known for its 260 km long barrier reef and associated lagoon reef shoals but also exhibits a complete transition from near shore siliciclastics to pure carbonate deposits across a narrow shelf lagoon and in addition has three of the very few occurrences of caribbean atolls published holocene facies relationships on the belize shelf have been semi quantitative in that they are based on quantitative point count thin section data in the northern shelf lagoon and on qualitative estimates of thin section composition in the southern shelf lagoon this contrast has been rectified by point counting southern shelf lagoon thin sections and incorporating the result with published point count data from the northern shelf supplemented by additional information to produce a modified factor analysis facies distribution for the entire shelf the resulting nine facies are extended seaward to include previously published analysis of sediment on the three belize off shelf atolls resulting in a total of 11 facies in addition the carbonate mud distribution has been mapped over both the shelf and atolls with the not unexpected result that in places the distribution pattern clearly indicates a barrier platform source of lagoon deposited carbonate mud dunham s limestone classification terminology has been used as a basis for description to make these relationships more useful to those reconstructing ancient limestone depositional environments

the chronology and structure of the western new caledonian barrier reef tracts abstract the mainland of new caledonia grande terre is surrounded by one of the largest continuous barrier reef system in the world in order to study the development history and internal structure of this system drilling operations have been carried out at two sites amedee and kendec islets located on the barrier reef tract extending from the south west 33 to the north west of new caledonia the extracted cores are 128 50 and 148 75 m in length respectively lithological and paleoecological descriptions combined with uranium thorium dating magnetostratigraphy and nannofossil based biostratigraphy allowed a reef evolutionary scheme to be drawn as a result of the interplay between margin subsidence and sea level changes 11 reef units formed successively during interglacial episodes at high sea levels in both sites depending on the subsidence rate of the western shelf margin major building in new caledonia appears to have started during the mis 11 400 000 yr from shallow water carbonate platform deposits older than 780 000 yr comparing development patterns between the new caledonian barrier reef and the australian great barrier reef clearly indicates that both global climate and regional tectonic history have been the major controls on reef initiation and growth along both sides of the coral sea climatic conditions are likely to have not been optimal before the late quaternary probably resulting in luxuriant reef expansion only during the last 400 000 yr

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

sea level records at 80 ka from tectonically stable platforms florida and bermuda studies from tectonically active coasts on new guinea and barbados have suggested that sea level at 80 ka was significantly lower than present whereas data from the atlantic and pacific coasts of north america indicate an 80 ka sea level close to that of the present we determined ages of corals from a shallow submerged reef off the florida keys and an emergent marine deposit on bermuda both localities are on tectonically stable platforms distant from plate boundaries uranium series ages show that corals at both localities grew during the 80 ka sea level highstand and geologic data show that sea level at that time was no lower than 7 9 m below present florida and may have been 1 2 m above present bermuda the ice volume discrepancy of the 80 ka sea level estimates is greater than the volume of the greenland or west antarctic ice sheets comparison of our ages with high latitude insolation values indicates that the sea level stand near the present at 80 ka could have been orbitally forced

post glacial microbialite formation in coral reefs of the pacific atlantic and indian oceans abstract the occurrence of microbialites in post glacial coral reefs has been interpreted to reflect an ecosystem response to environmental change the greater thickness of microbialites in reefs with a volcanic hinterland compared to thinner microbial crusts in reefs with a non volcanic hinterland led to the suggestion that fertilization of the reefal environment by chemical weathering of volcanic rocks stimulated primary productivity and microbialite formation using a molecular and isotopic approach on reef microbialites from tahiti pacific ocean it was recently shown that sulfate reducing bacteria favored the formation of microbial carbonates to test if similar mechanisms induced microbialite formation in other reefs as well the tahitian microbialites are compared with similar microbialites from coral reefs off vanuatu pacific ocean belize caribbean sea atlantic ocean and the maldives indian ocean in this study the selected study sites cover a wide range of geological settings reflecting variable input and composition of detritus the new lipid biomarker data and stable sulfur isotope results confirm that sulfate reducing bacteria played an intrinsic role in the precipitation of microbial carbonate at all study sites irrespective of the geological setting abundant biomarkers indicative of sulfate reducers include a variety of terminally branched and mid chain branched fatty acids as well as mono o alkyl glycerol ethers isotope evidence for bacterial sulfate reduction is represented by low 34s values of pyrite 43 to 42 enclosed in the microbialites and compared to seawater sulfate slightly elevated 34s and 18o values of carbonate associated sulfate 21 9 to 22 2 and 11 3 to 12 4 respectively microbialite formation took place in anoxic micro environments which presumably developed through the fertilization of the reef environment and the resultant accumulation of organic matter including bacterial extracellular polymeric substances eps coral mucus and marine snow in cavities within the coral framework tof sims analysis reveals that the dark layers of laminated microbialites are enriched in carbohydrates which are common constituents of eps and coral mucus these results support the hypothesis that bacterial degradation of eps and coral mucus within microbial mats favored carbonate precipitation because reefal microbialites formed by similar processes in very different geological settings this comparative study suggests that a volcanic hinterland is not required for microbialite growth yet detrital input derived from the weathering of volcanic rocks appears to be a natural fertilizer being conductive for the growth of microbial mats which fosters the development of particularly abundant and thick microbial crusts

quaternary reef response to sea level and environmental change in the western atlantic the tropical subtropical western atlantic realm harbours abundant fringing reefs two major barrier reefs belize florida several atolls and large reef fringed carbonate platforms bahamas data from belize and south florida indicate that major barrier reefs were established during the high sea levels of the long and warm marine isotope stage 11 reefs formed during pleistocene sea level highstands whereas erosion non deposition and the formation of subaerial exposure surfaces prevailed during lowstands of sea level florida bahamas exposed reefs and platforms with siliciclastic hinterlands were characterized by deposition of clays and sands on fluvial plains belize elevated terraces and outcrops of reefs of the last interglacial of marine isotope stage 5e are evidence of higher than present sea level and temperature that sustained large reef fringed carbonate platforms and ramps in the florida bahamas region and central america belize mexico including ooid deposition in warm and shallow waters during the highstands of marine isotope stages 5c and 5a at sea levels several metres lower than today fringing reefs developed in parts of the caribbean for example in south florida outlier reefs data from the island of barbados support the contention that the postglacial sea level rise from about 120 m was rapid and punctuated by two meltwater pulses ia and ib which bracket the beginning and end of the younger dryas respectively after reflooding of shelves in the early holocene reefs developed preferentially on highs of the underlying karstified pleistocene limestone surface and on former river channel bars many reefs in the western atlantic region kept pace with holocene sea level rise whereas some were drowned reasons for reef drowning are debated and include sea level rise elevation of antecedent topography and deterioration of environmental conditions such as high nutrient input apart from sea level and antecedent topography factors such as exposure to waves and currents storms and sedimentation have controlled reef development the historical decline of acroporid corals in the caribbean realm has been attributed to cooling following the holocene thermal optimum however historical die offs of reef building corals and other reef organisms suggest that some if not all recent declines were unprecedented during the holocene rising temperatures decreasing carbonate saturation increased frequency of major storms high nutrient concentrations and sedimentation overfishing and disease certainly played a role in decline but systematic studies relating these environmental factors to holocene reef building are only in the early stages

ice 5g and ice 6g models of postglacial relative sea level history applied to the holocene coral reef record of northeastern st croix u s v i investigating the influence of rotational feedback on gia processes at tropical latitudes abstract fossil coral reefs along the northeastern coast of st croix in the caribbean sea provide an 8000 year record of dated and interpreted holocene sea level change we herein compare this record with the predictions of models of glacio hydro isostatic adjustment for st croix and for additional sites at similar latitudes in the greater and lesser antilles region rsl predictions are based upon the model ice 5g vm2 and with a modified model ice 6g vm5a both including and excluding the influence of rotational feedback misfits between the modeled sea levels and the local geologic data are most apparent for models without rotational feedback particularly in the prediction of a 2 to 4 m unsupported mid holocene misfit at 4 ka as well as a small amplitude highstand that extends from 2 5 to 1 5 ka incorporation of the influence of rotational feedback provides the best fit to the data largely eliminating the unsupported mid holocene misfit between the data field and the sea level histories predicted by the models without rotational feedback and fitting data older than 5 kyr more closely than a previously published latitudinally averaged sea level curve for the western atlantic the st croix data therefore demonstrate that rotational influence extends at least 27 further south from its 45 n mid latitude extremum along the us east coast and identifies tropical latitudes as influenced by proglacial forebulge collapse implications for reef based sea level reconstruction include the ability to accurately model sea levels at specific tropical sites with partial holocene chronologies using the ice 6g vm5a model with rotational feedback latitudinally averaged sea level curves are therefore of limited use in understanding the relative importance of contributing physical influences on postglacial sea level history

nutrient and temperature controls on modern carbonate production an example from the gulf of california mexico in addition to salinity and temperature nutrient concentrations in surface waters are known to have a significant impact on distribution of carbonate producing biota but have never been quantitatively evaluated against different temperatures along a latitudinal transect the western coast of the gulf of california mexico presents a natural laboratory for investigating the influence of oceanographic parameters such as salinity temperature and chlorophyll a a proxy for nutrients on the composition of a range of modern heterozoan and photozoan carbonate environments along a north south latitudinal gradient spanning the entire warm temperate realm 29 n 23 n chlorophyll a measured in situ at half hour resolution is highly variable throughout the year due to short term upwelling and increases significantly from the southern to northern gulf of california salinity in contrast fluctuates little and remains at an average of 35 from south to north carbonate production ranges from oligotrophic mesotrophic coral reef dominated shallow water areas minimum temperature 18 6 c through mesotrophic eutrophic red algal dominated inner shelf carbonate production in the central gulf minimum temperature 16 c and to molluscan bryozoan eutrophic inner to outer shelf environments minimum temperature 13 7 c the gulf of california data supplemented with oceanographic and compositional information from a database compiled from a spectrum of modern carbonate systems worldwide demonstrates the significance of nutrient control in the formation of heterozoan photozoan and transitional heterozoan photozoan carbonate systems and serves as a basis for more accurately interpreting fossil carbonates

syn depositional alteration of coral reef framework through bioerosion encrustation and cementation taphonomic signatures of reef accretion and reef depositional events the development of coral reef framework and the preservational character of both in situ and rubble coral is strongly influenced by a range of physical chemical and biologically mediated taphonomic processes these operate at or just below the reef framework water interface and can be defined as having either a constructive or destructive effect upon primary reef framework i e coral constituents constructional activities add additional calcium carbonate to the primary framework structure via secondary framework growth and early cementation destructive processes which remove or degrade primary and secondary framework carbonate are associated with the effects of either physical mainly storm disturbance or biological erosion termed bioerosion key bioeroding groups include the grazing fish and echinoid groups as well as the activities of an array of infaunal borers these include specific groups of sponges bivalves and worms termed macroborers as well as cyanobacteria chlorophytes rhodophytes and fungi termed microborers the relative importance of each process and the rates at which they operate vary spatially across individual reef systems in addition many of these processes leave distinctive signatures on or in the coral framework in some cases e g calcareous encrusters these are the skeletons of the organisms themselves whilst in other cases the organism may leave behind a trace of their activity e g macro and microborers these represent useful palaeoenvironmental tools firstly because they often have good preservation potential and secondly because the range and extent of many of the individual species groups and processes involved exhibit reasonably well constrained environment and or depth related distributions as a result these taphonomically important organisms or processes can be used to delineate between reef environments in core or outcrop and to aid the interpretation of reef depositional processes and events this review summarises current understanding regarding the distribution of these species processes within contemporary reef settings and considers the suites of taphonomic signatures that may aid in the recognition and interpretation of depositional environments and events

multi stage reef development on barbados during the last interglaciation by mapping the vertical and lateral distribution of reefal facies on the west and south coast of barbados we have produced a revised model of reef development for the last interglaciation we find that reef architecture around barbados has significant complexity including evidence for wave exposure related variations in reef geometry and at least 3 stages of reef development that were controlled by variations in sea level during the main stage of development an acropora palmata dominated reef crest aggraded 22 m in response to a minimum sea level rise of 20 m during stage 2 a sea cave was cut 3 4 m above the fossil reef crest possibly indicating that reef growth was terminated before sea level reached the highstand similar sequences elsewhere in the caribbean indicate that this early reef demise may not be a local phenomenon several reefs apparently stopped growing between 2 and 4 m and only in sheltered areas did they reach the highstand at 6 m as recorded by intertidal notches this pattern of reef demise has previously been related to rapid sea level rise at the end of the interglacial but stratigraphic data are equivocal the final stage of reef development on barbados occurred when sea level began to fall this fall was rapid leaving a thin but widespread veneer of reef crest deposits over the proximal reef front and discontinuous intertidal and shallow subtidal deposits capping the distal reef front although further dating is required to differentiate these three stages our only reliable u th tims date indicates that almost 50 of the exposed reef had accreted by 129 ka giving an estimate of 15 ka for the main aggradational stage furthermore reports of relict reef crests buried beneath these exposed deposits indicate that our revised model is incomplete and that earlier stages of reef growth occurred during the last interglaciation these earlier stages imply that sea level was at an interglacial level for as long as 20 ka supporting the devils hole record of interglacial duration unfortunately these estimates could not be verified directly because most of our u th data show major stratigraphic age reversals attributed to diagenesis this pattern is also evident in all other well dated reefal units in the caribbean and leads us to conclude that only diagenetically screened precise stratigraphically consistent coral dates can be used to directly estimate the duration of the last interglaciation

rapid rupture directivity determination of moderate dip slip earthquakes with teleseismic body waves assuming reduced finite source approximation for an earthquake with along dip rupture there is opposite directivity effects on down going direct p wave and up going depth phases pp and sp and this can be exploited for resolving fault plane and rupture direction we propose a method to calculate the reduced finite source synthetics for teleseismic p wave and determine the rupture directivity via waveform fitting we verified the effectiveness of this method with forward tests and investigated its robustness against station selection uncertainties in point source parameters and uncertainties in source finiteness parameters we applied this method to the 2011 mw5 8 virginia earthquake the 2008 mw6 0 nevada earthquake and six other dip slip earthquakes for most cases we obtained rupture directivity results consistent with previous studies but the method could fail for along strike ruptures and very shallow earthquakes our method may help mitigate earthquake hazard by improving shake map with rapid rupture directivity analysis

mixed carbonates and siliciclastics in the quaternary of southern belize pleistocene turning points in reef development controlled by sea level change the belize barrier and atoll reefs represent one of the largest reef structures in the atlantic ocean the southern shelf of belize is a classic location of a modern mixed carbonate siliciclastic system whereas knowledge of the holocene deposits in the area is extensive data on the pleistocene system are fragmentary open questions include i the nature of the reef foundations carbonate versus siliciclastics ii the ages of the deposits including the initiation of the barrier reef and iii the response of the mixed system to sealevel fluctuations the results of a study of borings on the southern belize shelf are presented here six up to 105 m long borings were made to better understand the history of this important mixed system uranium series dating in the pleistocene was not possible because of diagenetic alteration however lithostratigraphy strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages results support the contention that the quaternary development in belize was quite similar to that of other major barrier reefs such as the florida reef tract and further afield the great barrier and the new caledonian barrier reefs all of these barrier reefs are mixed carbonate siliciclastic systems and significant reef growth only began after the onset of high amplitude eccentricity controlled sea level changes and as late as during the exceptionally long and warm marine isotope stage 11 some 400 ka in belize early pleistocene sections at bases of borings include mollusc rich wackestones rare coral packstones and marls which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka during the high sea levels of marine isotope stage 25 and possibly earlier marine isotope stage 31 or 37 the belize shelf was subaerially exposed for most of the mid pleistocene and was dominated by siliciclastic sedimentation possibly during marine isotope stages 24 to 12 when highstands were comparatively low continuous reefs at the shelf margin were developing during highstands in the late pleistocene beginning with the long and high highstand of marine isotope stage 11 some 400 ka the southern shelf was flooded entirely and carbonates started to dominate once more reefs developed on top of siliciclastic deposits on the shelf a continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin during late pleistocene lowstands siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform the quaternary belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds however any extrapolations are limited by the fact that fast growing scleractinian reef builders had not yet evolved in the palaeozoic

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

siliciclastic foundations of quaternary reefs in the southernmost belize lagoon british honduras analyses of a closely spaced lattice of seismic profiles from the southernmost belize lagoon combined with logs of nearby drill holes reveal that the quaternary late pleistocene plus holocene reefs and carbonate sediments are growing on siliciclastic sediments which have an alluvial and delta like morphology the residual relief of these coastal plain deposits localized initial coral growth or an accumulation of calcareous skeletal material favored sites for these were elevations such as levees and bars of remnant channels and deltaic lobes

holocene development of the belize barrier reef previously knowledge of the holocene development of the belize barrier reef bbr the largest reef system in the atlantic ocean was limited to one location carrie bow cay we present new data from 11 rotary drill cores taken at 9 locations and 36 radiometric ages that indicate that the bbr was established from 8 26 to 6 68 ky bp on pleistocene reef limestones presumably deposited during oxygen isotope stage 5 the nonsynchronous start of holocene reef growth was a consequence of variation in elevation of antecedent topography largely controlled by underlying nne trending structures from north to south pleistocene elevation decreases along these structural trends probably reflecting differential subsidence and variations in karst topography reef anatomy is characterized by three facies in order of decreasing abundance these facies are represented by corals mainly acropora palmata and members of the montastraea annularis group by unconsolidated sand and rubble and by well cemented coral grainstones rudstones holocene reef accumulation rates average 3 25 m ky the degree of reef consolidation is negatively correlated with holocene thicknesses indicating that slowly growing reefs are better cemented than fast growing ones we present a holocene sea level curve for belize based on 36 dates from this study and 33 dates from our previous studies in the area

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

interferometric synthetic aperture radar insar atmospheric correction gps moderate resolution imaging spectroradiometer modis and insar integration atmospheric effects represent one of the major limitations of repeat pass interferometric synthetic aperture radar insar in this paper gps and moderate resolution imaging spectroradiometer modis data were integrated to provide regional water vapor fields with a spatial resolution of 1 km 1 km and a water vapor correction model based on the resultant water vapor fields was successfully incorporated into the jet propulsion laboratory california institute of technology roi pac software the advantage of this integration approach is that only one continuous gps station is required within a 2030 km 1354 km modis scene application to ers 2 repeat pass data over the los angeles southern california integrated gps network scign area shows that this integration approach not only helps discriminate geophysical signals from atmospheric artifacts but also reduces water vapor effects significantly which is of great interest to a wide community of geophysicists

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

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

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

platforms of the nicaraguan rise examples of the sensitivity of carbonate sedimentation to excess trophic resources the nicaraguan rise is an active tectonic structure in the western caribbean carbonate accumulation on its platforms has not kept pace with relative holocene sea level rise despite a tropical location remote from terrigenous sedimentation trophic resources apparently exceed levels favoring coral reef development because sponge algal communities dominate the drowning western platforms in contrast to mixed coral algal benthos on pedro bank and well developed coral reefs along the north coast of jamaica concentrations of biotic pigments in sea surface waters show a corresponding west east gradient oceanic waters flowing over the western banks carry nearly twice as much biotic pigment as oceanic waters north of jamaica sources enriching the western caribbean are terrestrial runoff upwelling off northern south america and topographic upwelling over the nicaraguan rise that relatively modest levels of trophic resources can suppress coral reef development holds important implications for understanding carbonate platform drownings in the geologic record

global compilation of interferometric synthetic aperture radar earthquake source models 1 comparisons with seismic catalogs 1 while many earthquakes have now been studied using interferometric synthetic aperture radar insar data a full assessment of the quality and additional value of insar source parameters compared to seismological techniques is still lacking we compile a catalog of source models obtained using insar and estimate the corresponding centroid moment tensor cmt parameters we refer to this compilation as the icmt archive we compare source parameters from over 70 insar studies of 57 global earthquakes with those in the global cmt gcmt international seismological centre isc and engdahl hilst buland ehb seismic catalogs we find an overall good agreement between fault strike dip and rake values in the gcmt and icmt archives likewise the differences in seismic moment between these two archives are relatively small and we do not find support for previously suggested trends of insar leading to larger moments than seismic data however epicentral locations show substantial discrepancies which are larger for the gcmt median differences of 21 km than for the ehb and isc catalogs median differences of 10 km since insar data have a high spatial resolution and thus should map epicentral locations accurately this allows us to obtain a first independent estimate of epicentral location errors in the seismic catalogs earthquake depths from insar are systematically shallower than those in the ehb catalog with a median of differences of 5 km while this trend may be partly due to unmodeled crustal complexity it is also compatible with the observation that the rupture of crustal earthquakes tends to propagate upward in the seismogenic layer

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

estimating source parameters from deformation data with an application to the march 1997 earthquake swarm off the izu peninsula japan we have applied two monte carlo optimization techniques simulated annealing and random cost to the inversion of deformation data for fault and magma chamber geometry these techniques involve an element of randomness that permits them to escape local minima and ultimately converge to the global minimum of misfit space we have tested the monte carlo algorithms on two synthetic data sets we have also compared them to one another in terms of their efficiency and reliability we have applied the bootstrap method to estimate confidence intervals for the source parameters including the correlations inherent in the data additionally we present methods that use the information from the bootstrapping procedure to visualize the correlations between the different model parameters we have applied these techniques to gps tilt and leveling data from the march 1997 earthquake swarm off of the izu peninsula japan using the two monte carlo algorithms we have inferred two sources a dike and a fault that fit the deformation data and the patterns of seismicity and that are consistent with the regional stress field

punctuated global tropical cyclone activity over the past 5 000 years 1 there are now a substantial number of millennial scale records of tropical cyclones from a variety of locations globally some of these such as those in the atlantic and gulf of mexico show patterns of long term generally intense tropical cyclone tc behaviour that have been suggested to be due to either variations in enso or shifts in the position of the atlantic high pressure system and the jet stream comparisons are made here of the sedimentary overwash records from the gulf of mexico and atlantic ocean basin with the overwash records from the north west pacific and beach ridge records from the south west pacific and south east indian ocean basins there is a substantial degree of synchroneity in global intense tc behaviour over the past 3 000 to 5 000 years one of the most striking aspects of these records is they all display extended alternating periods centuries to millennia of relative quiescence and heightened intense tc activity irrespective of both the resolution and type of long term tc record the cause s of this punctuated activity are at present difficult to identify but are likely exogenic in origin rather than due to an intrinsic aspect of the records or the methods used to derive them the identification of punctuated global long term tc behaviour is important for understanding future tc activity and for assessing risk to coastal communities

event preservation in lagoonal reef systems paleontological data suggest that coral populations in the caribbean were consistently healthy for the past 2 3 k y beginning in the 1980s however disease outbreaks bleaching episodes hurricanes and other perturbations caused catastrophic coral mortality and regional turnover an alternative hypothesis based on historical sources posits that coral populations were already declining more than a century ago these hypotheses can be distinguished only if turnover events are reliably preserved in the holocene record of coral reefs push cores extracted from uncemented lagoonal reefs in belize showed that a direct hit by hurricane iris in 2001 did not disrupt the signature of the recent turnover event which entered the subfossil record essentially intact cores from lagoonal systems in several areas of the caribbean do not support the hypothesis that corals declined before the 1980s

a review of calcareous nannofossil astrobiochronology encompassing the past 25 million years this paper presents a review of astrobiochronological calibration of recent to late oligocene calcareous nannofossil datum events biohorizons included in the paper are those of the widely used standard nannofossil zonations of martini e 1971 standard tertiary and quaternary calcareous nannoplankton zonation in farinacci a ed proceedings of the second international conference on planktonic microfossils roma rome ed tecnosci vol 2 pp 739 785 and okada h and bukry d 1980 supplementary modification and introduction of code numbers to the low latitude coccolith biostratigraphy zonation bukry 1973 1975 marine micropaleontology 51 321 325 as well as supplementary biohorizons proposed in the literature the biohorizons have been selected on the basis of the unambiguous taxonomy of the index taxa and their biostratigraphic usefulness we emphasise the application of rigorous methodology in nannofossil studies which permits an evaluation of biohorizons in terms of reliability and calibrates their potential correlatability astrochronological age estimates rely on the geologic timescale developed by the ics in 2004 with some new calibrations included we provide an overview of the relative position of biohorizons versus the astronomically calibrated ages of magnetic reversals and reference isotope stratigraphies surprisingly there are still few high resolution quantitative biostratigraphic studies of astrochronologically tuned sections in spite of the central role of such studies in addressing fundamental problems such as the tempo and mode of plankton evolution

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

the belize margin revisited 2 origin of holocene antecedent topography the importance of antecedent topography in dictating holocene facies patterns has been generally recognized there is however disagreement as to origin or lithology of the antecedent topography particularly with respect to the siliciclastic or carbonate nature of the underlying topography and structural patterns to help resolve these problems published and unpublished information have been compiled to produce a structural fabric map of onshore and offshore belize that includes a new geologic map of the country the map along with illustrated seismic lines demonstrates the occurrence of a number of nne trending transpressional faults in which landward directed thrusting is consistently displayed along with tectonic inversion offshore wells in conjunction with the seismic lines document the inversion as post eocene suggesting a similar age for transpressional fault movement presumably the landward directed thrusting reflects the opposing force of eastward directed subduction along the western margin of central america relative to the westward seafloor spreading of the caribbean cayman ridge the belize faults show little current seismicity but nevertheless the resulting structures have affected quaternary carbonate deposition as evidenced on an illustrated seismic line by both seaward and landward bi directional progradation of the reef margin from an underlying structural high the structural influence on the development of holocene antecedent topography is further suggested by the occurrence of a bouguer gravity plateau in the same shelf area that marks the occurrence of the belize lagoon rhomboid shelf atolls the youngest documented lithology of 12 illustrated offshore exploration wells is miocene carbonate in some wells the carbonate is interpreted as extending into the pliocene and holocene although no age diagnostic criteria are in evidence in other wells siliciclastics of unknown age and thickness are identified as overlying neogene carbonates the regional distribution and age of onshore limestones suggests that unroofing of the cretaceous carbonate cap of the maya mountains siliciclastic sediment source did not occur until late in neogene time perhaps no earlier than late pliocene consequently the maya mountains could not have been a major offshore source of siliciclastics until the quaternary information on the lithology of the immediately underlying pre holocene is provided by limited penetration core data and shallow resolution seismic lines these show that antecedent pleistocene limestones beneath the holocene reefs were deposited around 130 000 b p isotope stage 5e the thickness of the overlying holocene shelf margin reef capped carbonates increases along depositional strike from a few meters in the north to more than 25 m in the south in contrast piston cores and seismic data from the southern shelf lagoon collectively document the occurrence of antecedent siliciclastic topography the southward dip of both carbonate and siliciclastic antecedent surfaces is presumably a reflection of increasing southerly subsidence increasing antecedent erosional relief in the same direction reflects the pronounced southerly increase in paleo rainfall that presumably paralleled that of present day rainfall

reconstructing 7000 years of north atlantic hurricane variability using deep sea sediment cores from the western great bahama bank q1 enso show abrupt changes around 6000 yrs b p but most coastal sedimentary records do not span this time period establishing longer records is essential for understanding mid holocene patterns of storminess and their climatic drivers which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep sea and bank edge sediments may offer an unexplored archive of long term hurricane activity here we develop this new approach reconstructing more than 7000 years of north atlantic hurricane variability using coarse grained deposits in sediment cores from the leeward margin of the great bahama bank high energy event layers within the resulting archive are 1 broadly correlated throughout an offbank transect of multi cores 2 closely matched with historic hurricane events and 3 synchronous with previous intervals of heightened north atlantic hurricane activity in overwash reconstructions from puerto rico and elsewhere in the bahamas lower storm frequency prior to 4400 yrs b p in our records suggests that precession and increased nh summer insolation may have greatly limited hurricane potential intensity outweighing weakened enso and a stronger west african monsoon factors thought to be favorable for hurricane development

inferred seismic fault associated with the 1998 m 6 2 zhangbei shanyi earthquake hebei province china abstract the shallow ms 6 2 1998 zhangbei shanyi earthquake that affected the northwest region of beijing china occurred at the intersection of two active fault zones located on the north and east edges of the ordos tableland a detailed map of the intensity distribution of damaged building shows that the most damaged area was centered 8 to 10 km away from the epicenter including an ellipsoidal region with a strike of nne where more than 70 to 90 of buildings were destroyed many chimneys and gate pillars were broken and fell toward the sse ssw direction in the western side of the most damaged area and to the nne nnw direction in the eastern side aftershocks were also concentrated in the most damaged area it is inferred that the boundary of the downfallen direction change is the surface trace of the seismic fault based on the seismic data the distribution of damaged buildings and the downfallen directions of 70 chimneys and gate pillars it is identified that the seismic fault is a thrust fault striking nne and dipping 40 to 50 northwest with a large right lateral displacement component

interferometric synthetic aperture radar atmospheric correction gps topography dependent turbulence model 1 over the last two decades repeat pass interferometric synthetic aperture radar insar has been widely used as a geodetic technique for measuring the earth s surface including topography and deformation like other astronomical and space geodetic techniques repeat pass insar is limited by the variable spatial and temporal distribution of atmospheric water vapor in this paper a topography dependent turbulence model gttm for short has been developed using gps data only to produce zenith path delay difference maps for insar atmospheric correction application of the gttm model to ers tandem data over the los angeles southern california integrated gps network area has shown that use of the gttm can reduce water vapor effects on interferograms from 10 mm down to 5 mm which is of great interest to a wide community of geophysicists the principal finding of this paper is that interpolation methods should be applied to zenith total delay ztd differences from different times instead of ztd values themselves for the purpose of insar atmospheric correction this is crucial to reduce if not completely remove topographic effects on ztd values

the 2010 mw 6 8 yushu qinghai china earthquake constraints provided by insar and body wave seismology 1 by combining observations from satellite radar body wave seismology and optical imagery we have determined the fault segmentation and sequence of ruptures for the 2010 mw 6 8 yushu china earthquake we have mapped the fault trace using displacements from sar image matching interferometric phase and coherence and 2 5 m spot 5 satellite images modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical with the central segment dipping 70 to the southwest slip occurs mainly in the upper 10 km with a maximum slip of 1 5 m at a depth of 4 km on the southeastern segment the maximum slip in the top 1 km i e near surface is up to 1 2 m and inferred locations of significant surface rupture are consistent with displacements from sar image matching and field observations the radar interferograms show rupture over a distance of almost 80 km much larger than initial seismological and field estimates of the length of the fault part of this difference can be attributed to slip on the northwestern segment of the fault being due to an mw 6 1 aftershock two hours after the main event the remaining difference can be explained by a non uniform slip distribution with much of the moment release occurring at depths of less than 10 km the rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2 5 km s southeastward toward the town of yushu located at the end of this segment accounting for the considerable building damage strain accumulation since the last earthquake on the fault segment beyond yushu is equivalent to an mw 6 5 earthquake

sea level oscillations during the last interglacial highstand recorded by bahamas corals whether sea level was stable during the last interglacial remains a subject of debate an analysis of the u th ages of coral reefs in the bahamas corrected for open system behaviour confirms the presence of at least one oscillation within the sea level highstand

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

a global compilation of coral sea level benchmarks implications and new challenges i present a quality controlled compilation of sea level data from u th dated corals encompassing 30 studies of 13 locations around the world the compilation contains relative sea level rsl data from each location based on both conventional and open system u th ages i have applied a commonly used age quality control criterion based on the initial 234u 238u activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150 000 yr this analysis reveals scatter of rsl estimates among coeval coral benchmarks both within individual locations and between locations particularly during marine isotope stage mis 5a and the glacial inception following the last interglacial the character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics glacio isostacy u series dating and or coral position to elucidate robust underlying patterns with confidence limits i performed a monte carlo style statistical analysis of the compiled coral data considering appropriate age and sea level uncertainties by its nature such an analysis has the tendency to smooth obscure millennial scale and finer details that may be important in individual datasets and favour the major underlying patterns that are supported by all datasets this statistical analysis is thus functional to illustrate major trends that are statistically robust what we know trends that are suggested but still are supported by few data what we might know subject to addition of more supporting data and improved corrections and which patterns data are clear outliers unlikely to be realistic given the rest of the global data and possibly needing further adjustments prior to the last glacial maximum and with the possible exception of the 130 120 ka period available coral data generally have insufficient temporal resolution and unexplained scatter which hinders identification of a well defined pattern with usefully narrow confidence limits this analysis thus provides a framework that objectively identifies critical targets for new data collection improved corrections and integration of coral data with independent stratigraphically continuous methods of sea level reconstruction

locations of selected small earthquakes in the zagros mountains the zagros mountains of southern iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between arabia and eurasia due to the lack of dense local seismic or geodetic networks the inferred kinematics of the collision in iran is mainly based on catalogs of teleseismically determined earthquake locations we surveyed all mw 4 5 earthquakes in the harvard centroid moment tensor hcmt and international seismological centre isc catalogs that occurred in the zagros mountains during the period 1992 2002 and that were spanned by interferometric synthetic aperture radar insar images from the ers 1 and 2 satellites we invert the observed deformation for the best fitting point source single fault plane and distributed fault slip for four earthquakes and one unexplained deformation event we find that we can precisely locate earthquakes that are too small to be well located by either the hcmt or isc catalogs allowing us to tie specific earthquakes to active geologic structures

modern carbonate siliciclastic transitions humid and arid tropical examples climate and tectonic setting largely control characteristics of transitions between carbonate and siliciclastic sediments in depositional systems three examples selected from both humid and arid tropical settings are discussed order to illustrate details of these relationships the eastern shelf area of nicaragua is an area where siliciclastic and carbonate sediments actively interfinger under humid tropical conditions extremely high rainfall 4 5 m yr 1 in the southern part of coastal plain coupled with a correspondently high sediment flux to the nearshore shelf results in an inner shelf that is dominated by siliciclastics density gradients and persistent momentum provided by the trade winds force turbid coastal waters to the south and confine siliciclastic sediments to a coast parallel zone approximately 20 km wide the remainder of the broad shelf is characterized by carbonate sediments and reefs the mid shelf area has a coarse carbonate sediment cover composed largely of the calcareous green alga halimeda the outer shelf displays rugged topography associated with reef development skeletal carbonates containing abundant coral and coralline algal grains are characteristic of the seaward margin of the shelf significant amounts of siliciclastic sediment are confined to the nearshore part of the shelf and the transition from siliclastics to carbonates occurs over a distance of 20 km or less a second example from the humid tropics focuses on the living reefs of indonesia that are surrounded by fine grained siliciclastics a warm rainy climate results in rapid weathering of volcanic rocks from the indonesian archipelago and abundant sediment input to the shallow 40 70 m deep sunda shelf in the northern hemisphere winter monsoonally driven marine processes rrive water and sediment to the east down the axis of the java sea during summer the direction of transport is reversed this bidirectional process regime not only leaves its imprint in reef and carbonate platform morphology but also results in widespread distribution of siliciclastics from adjacent source areas isolated reefs as well as small and generally elongate reef rimmed carbonate platforms 0 5 10 km long rise 40 50 m above a sea floor composed largely of siliciclastic sediments in these cases facies transitions are very abrupt until environmental conditions curtail the carbonate producing communities of these platforms carbonate buildups and associated skeletal sediments will coexist with wider spread and more abundant siliciclastics a third example from a low latitude arid setting shows that facies transitions from carbonates to siliciclastics typically take place over short distances the lack of significant rainfall coupled with high relief along fault controlled basin margins promotes aperiodic but powerful episodes of siliciclastic that build directly into the marine environment high sloping and narrow coastal plains composed of overlapping fans result the steep seaward ends of these fans are maintained and protected from marine erosion by coral reefs and associated carbonates regionally siliciclastic to carbonate facies changes in these arid settings take place over very shor distances a few kilometers at most however on a local scale carbonates may be replaced by siliciclastics over distances as small as a few tens of meters

computer simulation of reef growth light is one of the major controls on reef growth and carbonate production the growth of present reef builders depends largely upon the amount of light available for photosynthesis as light decreases with water depth so does reef growth the computer model presented extends this principle by combining two functions one for photosynthesis and the other for the extinction of light in water the model is used to simulate the growth of alacran reef mexico two reefs of the great barrier reef and the reefs of the windward platform of st croix us virgin islands the model also gives an accurate simulation of the growth of fore reef walls in belize in agreement with the accretion hypothesis developed for this feature

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

the 1998 mw 5 7 zhangbei shangyi china earthquake revisited a buried thrust fault revealed with interferometric synthetic aperture radar 1 the 1998 mw 5 7 zhangbei shangyi china earthquake is the largest to have occurred in northern china since the large 1976 ms 7 8 tangshan earthquake due to its proximity to beijing the capital of china it has therefore gained a lot of attention a great number of studies have been conducted using seismic and geodetic data but few are able to identify conclusively the orientation of the primary fault plane for this earthquake in this paper two independent ers synthetic aperture radar interferograms are used to determine precisely the location and magnitude of coseismic surface displacements 11 cm in the radar line of sight modeling the event as dislocation in an elastic half space suggests that the earthquake is associated with a buried shallow nne ssw oriented thrust fault with a limited amount of lateral displacement which is consistent with seismic intensity distribution and aftershock locations

sea level rise depth dependent carbonate sedimentation and the paradox of drowned platforms a mathematical model of carbonate platform evolution is presented in which depth dependent carbonate growth rates determine platform top accumulation patterns in response to rising relative sea level this model predicts that carbonate platform evolution is controlled primarily by the water depth and sediment accumulation rate conditions at the onset of relative sea level rise the long standing paradox of a drowned platform arose from the observation that maximum growth rate potentials of healthy platforms are faster than those of relative sea level rise the model presented here demonstrates that a carbonate platform could be drowned during a constant relative sea level rise whose rate remains less than the maximum carbonate production potential this scenario does not require environmental changes such as increases in nutrient supply or siliciclastic sedimentation to have taken place a rate of relative sea level rise that is higher than the carbonate accumulation rate at the initial water depth is the only necessary condition to cause continuous negative feedbacks to the sediment accumulation rates under these conditions the top of the carbonate platform gradually deepens until it is below the active photic zone and drowns despite the strong maximum growth potential of the carbonate production factory this result effectively resolves the paradox of a drowned carbonate platform test modelling runs conducted with 2 5 m and 15 m initial sea water depths at bracketed rates of relative sea level rise have determined how fast the system catches up and maintains the keep up phase this is the measure of time necessary for the basin to respond fully to external forcing mechanisms the duration of the catch up phase of platform response termed carbonate response time scales with the initial sea water depth and the platform top aggradation rate the catch up duration can be significantly elongated with an increase in the rate of relative sea level rise the transition from the catch up to the keep up phases can also be delayed by a time interval associated with ecological re establishment after platform flooding the carbonate model here employs a logistical equation to model the colonization of carbonate producing marine organisms and captures the initial time interval for full ecological re establishment this mechanism prevents the full extent of carbonate production to be achieved at the incipient stage of relative sea level rise the increase in delay time due to the carbonate response time and self organized processes associated with biological colonization increase the chances for platform drowning due to deepening of water depth ca 10 m furthermore this implies a greater likelihood for an autogenic origin for high frequency cyclic strata than has been estimated previously

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

mangrove swamp stratigraphy and holocene transgression grand cayman island west indies abstract the island of grand cayman in the western caribbean has an extensive mangrove swamp vegetation numerous cores have been taken in and adjacent to these swamplands and these reveal that the swamps are generally underlain by a transgressive sequence of sediments the basal unit of this sequence consists of a laminated or non laminated crust formed in a subaerial environment locally these crusts are overlain by plastic mud deposited in seasonally flooded environments mangrove peat forms the upper unit of the transgression within most of the swamplands overlying the other units where these are found and reaching thicknesses of more than 4 m the final stage of marine incursion is recorded to the east of north sound where in water depths of 10 200 cm shelly mud occurs overlying mangrove peat in contrast to this to the west of north sound there is a regressive sequence in which shelly marl underlies a localised sea grass peat and mangrove peat this regressive sequence records local progradation of mangroves into marine environments the transgressive sedimentary sequence on grand cayman is similar to transgressive sedimentary sequences described from the florida everglades mangrove complex florida bay and the belize shelf on grand cayman however the stratigraphy is less complex because there are not extensive freshwater peat forming environments or intertidal and supratidal carbonate environments samples of mangrove peat were collected from the peat bedrock interface along a surveyed profile across barkers peninsula on grand cayman radiometric dating of these implies that sea level was approximately 185 cm below the present level at least 2100 years bp comparison of these dates with dates on mangrove peat from elsewhere suggests that submergence on grand cayman has taken place at a similar rate to that in florida

improved chronostratigraphic reference curve of late neogene seawater 87sr 86sr we present a reference curve of seawater 87 sr 86 sr variation through the past 7 m y based on 455 samples of planktonic foraminifera from ocean drilling program odp site 758 in the indian ocean this single site curve is superior to extant curves because of several features 1 a continuous sedimentary section free of disturbances 2 a well determined and precise chronostratigraphy that is calibrated to numeric age on the basis of continuous magnetostratigraphy and a refined astronomical time scale 3 a high temporal resolution sample interval averages 15 ka 4 an improved analytical reproducibility and 5 a uniformly high sample quality the gross structure of the site 758 curve is generally similar to that observed in previous work but the increased temporal resolution and decreased analytical scatter of the curve provide improved chronostratigraphic resolution at the 95 confidence level uncertainties on age estimates range from 0 60 m y in the lower pleistocene and upper miocene to 2 03 m y in the middle pliocene moreover this detailed record identifies two periods of steplike increases in seawater 87 sr 86 sr 6 10 to 5 80 ma and 1 46 to 1 13 ma that are characterized by rates of change of 150 10 6 m y these features if verified at other sites indicate abrupt changes in the sr mass balance of the ocean and may be used as precise event markers in late neogene marine sections

the structural and sedimentological controls on the reoccupation of quaternary incised valleys belize southern lagoon a grid of high resolution single channel seismic data from the belize southern lagoon has documented the development of several generations of stacked late pleistocene 400 ka holocene incised valley fills a feedback mechanism between tectonics reefal buildups and incised valley location is apparent in the data incised valleys are recognized as medium to high amplitude reflections that truncate reflections produced by older strata on the seismic data the holocene valley fills in the belize southern lagoon contain three seismic facies units from bottom to top 1 a basal unit characterized by moderately high amplitude chaotic reflections or progradational patterns that downlap onto the valley floor 2 a middle unit characterized by continuous horizontal near transparent reflections that drape the basal unit and onlap the valley walls and 3 an upper unit that consists predominantly of transparent to low amplitude low angle downlapping reflections the middle and upper units are separated by an erosional surface based on core evidence and seismic facies analysis the basal middle and upper seismic and sedimentary facies units are interpreted as fluvial and carbonate sands estuarine muds and marine sands and muds respectively the erosional surface separating the upper and middle units is interpreted to be a ravinement surface that marks the transition from brackish estuarine conditions to open marine conditions faulting decreases and reefal buildups increase upsection the oldest valleys mimic structural trends and flow through areas currently occupied by extensive carbonate reefs rapid high amplitude late pleistocene sea level rises may have led to wides pread reef development creating a template that subsequent incisions reoccupation valleys followed regardless of structural trends the intimate relationship among tectonics sea level change carbonate reef buildups and incised valley reoccupation serves as a model for understanding ancient tropical mixed carbonate siliciclastic systems accelerator mass spectrometer 14c dates of sediment core samples marine gastropods marine mollusks barnacles worm tubes peat and oysters indicate all the sediment cored 1 4 m in this study is holocene in age between 4740 60 and 11 230 90 14c age this radiocarbon dating consistently links the erosional surface between the upper and middle units with the intersection of the regional sea level curve nonmarine marine boundary

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

u series and amino acid racemization geochronology of bermuda implications for eustatic sea level fluctuation over the past 250 000 years abstract bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of late pleistocene eustatic sea level fluctuation has been reconstructed from a detailed study of geological field relationships combined with an extensive programme of u series and amino acid racemization geochronology only twice in the past 250 000 yr has sea level in bermuda been above its present level once at approximately 200 k y when it stood at about 2 m and most recently at 125 4 k y when it stood at 5 1 m these times of interglacial high sea level are characterized by the development of patch reefs and marine calcarenites at elevations above present sea level episodes of lower sea stand onto the bermuda platform at elevations higher than 20 m are observed within the two interglacial periods and are characterized by the deposition of eolianites by contrast glacial periods are times of residual soil formation and deposition of speleothems in caves at elevations below present sea level excellent correlation is observed between the bermuda glacio eustatic sea level record and other marine and terrestrial paleoclimate records

a plate tectonic model for the mesozoic and early cenozoic history of the caribbean plate abstract we present a model in which the caribbean plate is an intra american feature formed along the caribbean spreading center as opposed to the current model that considers the caribbean plate as a far travelled crustal segment that formed in the pacific region paleomagnetic data which cover an age range from jurassic through paleocene indicate the ophiolite complexes in costa rica and panama formed in an equatorial position the ophiolites did not fundamentally change their position relative to south america since their origin basaltic rocks of the lower part of the ophiolites are of mid ocean ridge type suggesting formation at a spreading center they are interpreted to have formed as part of the proto caribbean crust at a spreading axis in an intra american position during jurassic and early cretaceous times the upper part of the ophiolites is mainly built up by island arc and intraplate basalts the island arc basalts evolved at the central american landbridge which started in the middle cretaceous the intraplate basalts are related to the caribbean plateau basalt which thickened and stiffened the caribbean crust in middle cretaceous to probably campanian times changes in relative plate motions along the middle american convergent plate margin are reflected by orientations and time sequences of paleostress tensors calculated from fault slip data in southern mexico and costa rica kinematic indicators from mylonite zones display sinistral movement along secondary shear zones within the southern mexican crustal complexes and along the northern boundary of the chortis block in the motagua polochic fault system this reflects the eastward drift of the chortis block since the beginning of the cenozoic at this time the chortis block became part of the caribbean plate which moved more than 1000 km towards the east relative to the north and south american plates during the cenozoic

fault identification for buried strike slip earthquakes using insar the 1994 and 2004 al hoceima morocco earthquakes summary the 1994 m w 6 0 and 2004 m w 6 5 al hoceima earthquakes are the largest to have occurred in morocco for 100 yr and give valuable insight into the poorly understood tectonics of the area bodywave modelling indicates the earthquakes occurred on near vertical strike slip faults with the nodal planes oriented nw se and ne sw distinguishing between the primary fault plane and auxiliary planes using either geodetic or seismic data is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized buried strikeslip earthquakes preliminary studies using aftershock locations and surface observations have been unable to identify the orientation of the primary fault plane for either earthquake conclusively we use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity for the 2004 earthquake inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data however the ne sw best fit fault plane has an unrealistically high fault slip to length ratio and we conclude the nw se striking nodal plane is the primary fault plane and slip was right lateral we carry out tests on synthetic data for a buried strike slip earthquake in which the orientation of the fault plane is known a priori independent of geometry missing data and correlated noise models produced assuming the auxiliary plane to be the fault plane have very high fault slip to length ratios the 1994 earthquake had a smaller magnitude and comparisons of model misfits and slip to length ratios do not conclusively indicate which of the nodal planes is the primary fault plane nonetheless the insar data provides valuable information by improving the accuracy of the earthquake location by an order of magnitude we carry out a multiple event relocation of the entire earthquake sequence including aftershocks making use of the absolute locations for the 1994 and 2004 main shocks from our insar study the aftershock locations are consistent with a nw se orientated fault plane in 2004 and suggests that the 1994 earthquake occurred on a ne sw fault perpendicular to the fault which ruptured in 2004 previous tectonic models of the area proposed a bookshelf model of block rotation with nne ssw left lateral faults this model requires modification to accommodate the observation of right lateral slip on a nw se fault plane for the 2004 earthquake and we prefer to interpret the fault orientations as due to a zone of distributed shear with a right lateral fault striking at 115 and conjugate clockwise rotating left lateral faults striking at 25

amino acid geochronology resolution and precision in carbonate fossils changes in indigenous proteins preserved in carbonate skeletons can be used to estimate the time elapsed since death of the organism racemization the most widely used reaction in amino acid geochronology refers to the inversion of l amino acids to their d configuration for the protein amino acid l isoleucine racemization occurs about only one of the two chiral carbon atoms this reaction epimerization proceeds from an initial dl ratio near zero to an equilibrium ratio of about 1 30 the reaction rate is controlled primarily by temperature and to a lesser degree by the nature of the proteins themselves a variable related to taxonomy and the extent of protein degradation analyzing monospecific samples minimizes the taxonomic variable the resolving power of dl ratios as relative age indices is a function of the reaction rate degree of natural variability and analytical uncertainty natural variability is defined as the spread in ratios in five well preserved shells of the same age from a single stratum and is primarily related to taxonomy it can range from 20 or more in taxa of low reliability to 1 in taxa of greatest integrity 5 to 10 is to be expected analytical uncertainty within a single laboratory is relatively insignificant amounting to no more than 2 but interlaboratory comparisons suggest caution in comparing ratios determined at different laboratories or by different techniques sampling appropriate portions of a shell is essential to minimize variability in dl ratios site temperature exerts the greatest control on reaction rate hence resolving power for tropical sites 25 c age differences 1 ka can be resolved within the holocene and ca 5 to 10 ka for older samples as the rate decreases equilibrium is attained after 150 to 300 ka the reaction rate is substantially lower at mid latitude sites ca 10 c where equilibrium requires about 2 ma and resolution within the last glacial cycle is no better than 10 to 20 ka arctic sites 10 c show almost no measurable racemization within the holocene and in extreme cases even within the last 100 ka equilibrium is not attained in 10 ma the extent of amino acid racemization epimerization in carbonate fossils provides chronological information for the critical time period beyond radiocarbon dating dl ratios can be used directly as relative age indices and with suitable calibration can provide reasonable estimates of absolute age and or effective diagenetic temperature improving the accuracy of racemization based age estimates requires a better understanding of racemization kinetics in carbonate systems

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

new constraints on the origin of the australian great barrier reef results from an international project of deep coring two new boreholes provide the first direct evidence of the age of the australian great barrier reef an inner shelf sequence total depth 86 m basal age 210 40 ka comprises a dominantly siliciclastic unit thickness 52 86 m overlain by four carbonate units total thickness 0 34 m a shelf edge and slope sequence total depth 210 m reveals three major sections 1 a lower section of resedimented flows deposited on a lower slope 2 a mid section including intervals of corals rhodoliths and calcarenites with low angle graded laminae and 3 an upper section of four shelf margin coral reef units separated by karst surfaces bearing paleosols sr isotope and magnetostratigraphic data indicate that the central great barrier reef is relatively young post bruhnes matuyama boundary time and our best estimate for the onset of reef growth on the outer barrier system is ca 600 280 ka this date suggests that reef initiation may have been related to the onset of full eccentricity dominated glacio eustatic sea level oscillation as inferred from large amplitude saw tooth 100 k y 18o cycles after marine isotope stage 17 rather than to some regional environmental parameter a major question raised by our study is whether reef margins globally display a similar growth history the possibility of a global reef initiation event has important implications for basin to shelf partitioning of caco3 atmospheric carbon dioxide levels and global temperature change during quaternary time

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

the transient nature of the empty bucket model of reef sedimentation abstract the geometry of modern reefs has been likened to an empty bucket with the narrow reef rim comprising the container pail that encloses the water filled bucket while the analogy is valid the assumption that this constitutes a final geometry is not examples from the indian pacific and atlantic oceans individually and collectively demonstrate current filling of the lagoons by reef perimeter sand aprons since sea level only approximated its present position 3 to 6 ky ago it follows that the observed extent of modern highstand lagoon filling is minimal if the filling process was to continue unabated the result would be a flat topped bank but during the pleistocene low stands of sea level aborted the filling process extrapolating these relationships to the geologic record suggests that the empty bucket model of unfilled reef lagoon space is greatest during icehouse high frequency glacial fluctuations of sea level alternatively filled buckets in which cycle thickness approximates accommodation space are probably largely restricted to greenhouse time intervals the co occurrence of quaternary high amplitude frequency sea level changes with rapidly growing scleractinian corals probably enhanced the occurrence of empty bucket morphologies

highstands during marine isotope stage 5 evidence from the ironshore formation of grand cayman british west indies abstract the ironshore formation on grand cayman is formed of six unconformity bounded packages units a f units a b c and d known from the subsurface in the northeastern part of grand cayman formed during marine isotope stages mis 11 9 7 and 5e respectively unconformities at the tops of units a b and c are highlighted by terra rossa and or calcrete layers strata in core obtained from wells drilled in george town harbour and exposed on the west part of grand cayman belong to unit d and the newly defined units e and f corals from unit e yielded th u ages of 104 ka whereas conch shells from unit f gave ages of 84 ka unit e equates to mis 5c whereas unit f developed during mis 5a th u dating of corals and conchs from the ironshore formation on the western part of grand cayman shows that unit d formed during the mis 5e highstand whereas units e and f developed in association with highstands at 95 110 ka mis 5c and 73 87 ka mis 5a unit e 5 m thick in the offshore cores is poorly represented in onshore exposures unit f which unconformably overlies unit d at most localities is formed largely of fossil poor cross bedded ooid grainstones the unconformity at the top of unit d a marine erosional surface with up to 2 5 m relief is not characterized by terra rossa or calcrete in the offshore cores or onshore exposures unit d formed with a highstand of 6 m asl whereas units e and f developed when sea level was 2 to 5 asl and 3 to 6 m asl respectively thus the highstands associated with mis 5e 5c and 5a were at similar elevations

progress in esr dating of pleistocene corals a new approach for de determination abstract esr dating has been widely applied for dating of corals of the age up to 500 000 to 600 000 years ago many studies have yielded promising results but the accurate determination of the equivalent dose d e remains a major limitation inflexion points in the dose response curve are shown to hinder correct fitting and limit the reliability of d e values here we present a new approach to obtain more reliable d e values

geochemical and geophysical implications of the radiocarbon calibration abstract a precise and accurate chronological framework is crucial to study the dynamics of a variety of phenomena which occurred during the last 45 000 years although the 14 c dating method has been widely applied since the 1950s it is recognized that the atmospheric 14 c 12 c ratio has not been stable during the past in order to calculate accurate ages these fluctuations have to be corrected by means of a calibration curve obtained by comparing raw 14 c measurements with true calendar ages provided by independent dating methods the calibration curve obtained so far is characterized by a long term trend with raw 14 c ages being significantly younger than calendar ages during most of the last 45 000 years abrupt 14 c shifts which occurred over centuries to millennia are superimposed on this long term trend of decreasing atmospheric 14 c 12 c ratio to a certain extent it is possible to outline the different causes of atmospheric 14 c variations by considering complementary information obtained from other cosmogenic nuclides studied at different latitudes 1 most high frequency changes in the atmospheric 14 c 12 c ratio are linked to magnetic fluctuations of solar origin as revealed by studying the last three centuries for which direct observations of the sun are available a similar conclusion is derived by comparing 14 c 12 c events with 10 be and 36 cl concentration maxima in polar ice cores 2 the long term trend shift of 14 c ages is due to a long period of decreased shielding effect of the geomagnetic dipole field which occurred over the interval between 10 000 and 40 000 years bp this interpretation is supported by paleomagnetic measurements performed on volcanic and sedimentary rocks and by 10 be and 36 cl analysed in low and high latitude records 3 a prominent and rapid atmospheric 14 c 12 c excursion occurred between 13 000 and 11 500 cal yr bp thus corresponding to the younger dryas cold period by contrast with the 14 c variability mentioned above which is linked to 14 c production changes this so called 14 c age plateau is probably due to an abrupt variation in the rates of exchange within the global carbon cycle this interpretation is supported by independent geochemical proxies and by numerical modelling of the carbon cycle

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

modeling carbonate platform sedimentation lag comes naturally sedimentation on carbonate platforms is commonly found to lag relative sea level change particularly when platforms reestablish themselves after emersion models of platform sedimentation usually reproduce this lag with the help of special lag parameters a cellular automaton is used here to model the way that platforms are colonized by carbonate producing organisms this model shows that lag is a natural result of colonization and is considerably more complex than allowed for by other sedimentation models the model predicts that there are two types of platform one in shallow water the other in deeper water which are cross coupled dynamical attractors

earthquake deformation cycle on the san andreas fault near parkfield california six moderate earthquakes are thought to have ruptured the parkfield segment of the san andreas fault since 1857 the similar characteristics of the three seismically recorded events together with the quasi regular 22 year recurrence interval have led to the forecast of a similar event in 1988 5 years in this study the potential for the hypothesized earthquake is assessed by estimating the time required for interseismic straining to recover the strain energy released by the most recent june 1966 parkfield earthquake for a simple model of the earthquake cycle this interval is proportional to the ratio of the 1966 seismic moment to the interseismic moment deficit rate baseline lengths measured before and after the 1966 earthquake are inverted to estimate the magnitude and distribution of the combined coseismic and transient postseismic slip although the geodetic data determine only broad spatial averages of the fault slip they do require that slip at depth exceeded the surface offsets measured in 1966 inversions with extreme prior models are calculated to assess the range of seismic moment and moment deficit rates consistent with the available geodetic data inversions assuming only that the slip distributions are to some degree smooth yield strain energy recovery intervals of 14 25 years extreme values range from as little as 6 years to as much as 29 years in comparison historic recurrence intervals of parkfield earthquakes range from 12 to 32 years these results are consistent with the expectation of a magnitude 5 6 earthquake near parkfield by 1993

last interglacial sea stands on barbados and an early anomalous deglaciation timed by differential uplift three major sea level maxima between 137 and 120 kyr b p are documented by surveys of pairs of wave cut notches and other features associated with the broadly defined last interglacial coral terrace on barbados regression analysis of elevation differences between notch pair members as a function of their uplift rates at seven sites yields the age difference between first and third sea stands and their eustatic sea level difference these results when combined with stratigraphic data from the bahamas bermuda and western australia and a chronology based on age limits of corals from the bahamas and western australia yield an endpoint age and eustatic low tide elevation of 136 7 kyr b p and 7 4 m respectively for the first sea stand 126 kyr b p and 5 6 m for the second and 120 5 kyr b p and 3 0 m for the third the first sea stand is the result of an anomalous deglaciation that was completed during low northern summer milankovitch insolation this is contrary to the milankovitch hypothesis that orbitally controlled insolation largely determines the variations of glacial ice volume it implies that internal factors within the earth s climate system can be much stronger than the effects of insolation variations

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

hurricane control on shelf edge reef architecture around grand cayman rimming the outer shelf of grand cayman is a submerged 87 km long shelf edge reef that rises to within 12 m of mean sea level it consists of an array of coral armoured buttresses aligned perpendicular to shore and separated by steep sided sediment floored canyons individual buttresses have a diverse coral dominated biota and consist of three architectural elements a shield like front wall colonized by platy corals a dome shaped crown colonized by head corals and a shoreward projecting spur covered by varying amounts of branching coral buttresses are commonly fronted by coral pinnacles that in some areas have amalgamated with buttress walls to produce pinnacle and arch structures as margin orientation changes shelf edge reef architecture shows systematic variations that are consistent with changes in fetch and height of hurricane waves along margins exposed to fully developed storm waves shelf edge reef buttresses are deep have large amplitudes and are dominated by robust head corals these characteristics are consistent with hurricane induced pruning of branching corals and the flushing of significant quantities of sand from buttress canyons by return flows along margins impacted by fetch limited storm waves reef buttresses are shallower have intermediate amplitudes and have a significantly higher proportion of branching corals these characteristics are consistent with less coral pruning and sand flushing by weaker hurricane waves along margins fully protected from storm waves the buttresses canyon architecture of the shelf edge reef breaks down producing a series of shallow undulating branching coral dominated ridges that merge laterally into an unbroken belt of coral these characteristics correspond with negligible amounts of pruning and flushing during hurricanes in addition to differences between margins local intra marginal changes in shelf edge reef architecture are consistent with changes in the angle of hurricane wave approach open sections of the shelf edge reef which face directly into storm waves are pruned of branching corals and the fragments swept back onto the shelf producing extensive spurs by contrast on more sheltered obliquely orientated sections storm waves sweep debris along and off shelf producing little or no spur development instead the debris shed seawards accumulates in front of the buttress walls and initiates the development of coral pinnacles over time repeated buttress pruning and canyon flushing during hurricanes not only controls reef architecture but may also influence accretion patterns vertical accretion is limited by the effective depth of storm wave fragmentation once this hurricane accretion threshold is reached the reef moves into a shedding phase and accretes laterally via pinnacle growth amalgamation and infilling consequently the reef steps out over its own debris in a kind of balancing act between lateral growth and slope failure a pattern widely recognized in ancient reefs

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

holocene development of three isolated carbonate platforms belize central america abstract locally operating factors such as topography of the reef basement and exposure to waves and currents rather than regionally effective factors such as the post glacial sea level rise in the western atlantic explain the different holocene developments of the three isolated carbonate platforms glovers reef lighthouse reef and turneffe islands offshore belize a series of nne striking tilted fault blocks at the passive continental margin forms the deep basement of the belize reefs glovers and lighthouse reefs are located on the same fault block while turneffe islands is situated west of lighthouse reef on an adjacent fault block the three platforms are surrounded by deep water and have surfacebreaking reef rims significant differences exist between platform interiors glovers reef has only 0 2 of land and an 18 m deep well circulated lagoon with over 800 patch reefs lighthouse reef has 3 of land and a well circulated lagoon area patch reefs are aligned along a nne striking trend that separates a shallow western 3 m and a deeper eastern 8 m lagoon turneffe islands has 22 of land that is mainly red mangrove interior lagoons are up to 8 m deep and most have restricted circulation and no patch reefs surface sediments are rich in organic matter in contrast the northernmost part of turneffe islands has no extensive mangrove development and the well circulated lagoon area has abundant patch reefs holocene reef development was investigated by means of 9 rotary core holes that all reached pleistocene reef limestones and by radiometric dating of corals maximal holocene reef thickness reaches 11 7 m on glovers reef 7 9 m on lighthouse reef and 3 8 m on turneffe islands factors that controlled holocene reef development include the following 1 holocene sea level the margin of glovers reef was flooded by the rising holocene sea ca 7500 ybp that of lighthouse reef ca 6500 ybp and that of turneffe islands between 5400 and 4750 ybp all investigated holocene reefs belong to the keep up type even though the three platforms were flooded successively and hence the reefs had to keep pace with different rates of sea level rise 2 pre holocene topography pleistocene elevation and relief are different on the three platforms this is the consequence of both tectonics and karst different elevations caused successive reef initiation and they also resulted in differences in lagoon depths variations in pleistocene topography also explain the different facies distribution patterns on the windward platforms that are located on the same fault block on lighthouse reef tectonic structures are clearly visible such as the linear patch reef trend that is aligned along a pleistocene fault on glovers reef only short linear trends of patch reefs can be detected because the pleistocene tectonic structures are presumably masked by the higher holocene thickness the lower pleistocene elevation on glovers reef is probably a consequence of both a southward tectonic tilt and stronger karstification towards the south related to higher rainfall 3 exposure to waves and currents glovers reef lighthouse reef and the northernmost part of turneffe islands receive the maximum wave force as they are open to the caribbean sea adjacent lagoons are well circulated and have luxuriant patch reef growth and no extensive mangrove development by contrast most of turneffe islands is protected from the open caribbean sea by lighthouse reef to the east and is only exposed to reduced wave forces allowing extensive mangrove growth in these protected areas

patterns and mechanisms of coseismic and postseismic slips of the 2011 mw 7 1 van turkey earthquake revealed by multi platform synthetic aperture radar interferometry on 23rd october 2011 a mw 7 1 reverse slip earthquake occurred in the bardakci saray thrust fault zone in the van region eastern turkey earlier geodetic studies have found different slip distributions in terms of both magnitude and pattern in this paper we present several cosmo skymed csk envisat asar and radarsat 2 interferograms spanning different time intervals showing that significant postseismic signals can be observed in the first three days after the mainshock using observations that combine coseismic and postseismic signals is shown to significantly underestimate coseismic slip we hence employed the csk pair with the minimum postseismic signals to generate one conventional interferogram and one along track interferogram for further coseismic modelling our best fit coseismic slip model suggests that 1 this event is associated with a buried nnw dipping fault with a preferable dip angle of 49 and a maximum slip of 6 5 m at a depth of 12 km and 2 two unequal asperities can be observed consistent with previous seismic solutions significant oblique aseismic slip with predominant left lateral slip components above the coseismic rupture zone within the first 3 days after the mainshock is also revealed by a postseismic csk interferogram indicating that the greatest principal stress axis might have rotated due to a significant stress drop during the coseismic rupture