Foraminiferal Transfer Functions Research Articles

Impact of hydrological changes and vertical motions on Pleistocene marine environments of the eastern coast of the island of Rhodes (Greece)

The island of Rhodes in the eastern Mediterranean Sea is situated in an area affected by an ongoing plate convergence, and its Pleistocene marine environments were influenced by recurring hypoxia and changes in organic matter fluxes. This makes the island an important site to study the influence of orbital-driven climate changes and tectonic-induced vertical motions on the marine benthic ecosystems in near-coastal areas at local and regional scales. We investigated the Early and Late Pleistocene sediment sections at Agathi Beach and Lardos, located on the middle-eastern coast of the island. Our results show variations in oxygen and food levels at the sea floor, including transient phases of enhanced fresh-water and nutrient input to near-coastal environments. These phases occurred at times of Northern Hemisphere summer insolation maxima, simultaneously to the formation of sapropels in the deep-sea basins of the eastern Mediterranean Sea. The application of a benthic foraminiferal transfer function revealed that both sections were influenced by tectonic-driven long-term and short-term vertical motions with higher rates than expected on the island of Rhodes. While Agathi Beach underwent two short-term cycles of uplift and subsidence, Lardos indicates at least three cycles with average rates of vertical motion as high as 8.6 mm/a.

Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone

AbstractLithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, >400 m distribution, ∼0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ∼0.5 m detection threshold for distinguishing coseismic from nonseismic changes.

Paleo-ecologic and neotectonic evolution of a marine depositional environment in SE Rhodes (Greece) during the early Pleistocene

We have studied benthic foraminiferal assemblages in a marine sediment section (Pefka E section) from the Lindos Bay Formation deposited during the early Pleistocene to provide new insights into the paleo-ecologic and neotectonic evolution of the SE part of the island of Rhodes (NE Mediterranean Sea). Relatively high amounts of eutrophic/low oxygen tolerant species and a comparatively high foraminiferal diversity indicate generally mesotrophic conditions at the sea floor and the presence of well-oxygenated bottom waters. These conditions are attributed to generally elevated surface water productivity and related organic matter fluxes during the early Pleistocene, which is in contrast to the modern oligotrophic conditions in this region. The abundance of individual species shows orbital-driven variability in the obliquity (41 kyr) and precessional (∼23 kyr) bands. Obliquity-driven changes in food availability are indicated by increased percentages of Cassidulina carinata s.l. during marine isotope stages (MIS) 44 and 42, reflecting enhanced food fluxes under glacial conditions. Precession-driven changes are observed for Ca. carinata s.l., Cibicidoides pseudoungerianus s.l., Cibicidoides mundulus and Gyroidinoides altiformis. These changes likely reflect prolonged near-coastal phytoplankton blooms triggered by local fresh-water runoff at times of Northern-Hemisphere insolation maxima, coeval to the formation of sapropels in the adjacent deep-sea basins. The application of a benthic foraminiferal transfer function allowed for the identification of a number of short-term subsidence-uplift cycles, superimposed by overall long-term subsidence of the SE coast of Rhodes. Estimated average uplift and subsidence rates vary between ∼4.2 and ∼10.3 mm/yr. These rates of tectonic motions are distinctly higher compared to most other estimates from Rhodes and suggest a complex neotectonic history of the island during the early Pleistocene, involving both large-scale and local motions associated with alternating compressional and extensional regimes.

Revising Estimates of Spatially Variable Subsidence during the A.D. 1700 Cascadia Earthquake Using a Bayesian Foraminiferal Transfer Function

Revising Estimates of Spatially Variable Subsidence during the A.D. 1700 Cascadia Earthquake Using a Bayesian Foraminiferal Transfer Function

Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida

To address a paucity of Common Era data in the Gulf of Mexico, we reconstructed ~1.1m of relative sea-level (RSL) rise over the past ~2000years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regional-scale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollution, 137Cs and pollen chronohorizons. Our proxy reconstruction was combined with tide-gauge data from four nearby sites spanning 1913–2014CE. Application of an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model to the combined proxy and instrumental dataset demonstrates that RSL fell from ~350 to 100BCE, before rising continuously to present. This initial RSL fall was likely the result of local-scale processes (e.g., silting up of a tidal flat or shallow sub-tidal shoal) as salt-marsh development at the site began. Since ~0CE, we consider the reconstruction to be representative of regional-scale RSL trends. We removed a linear rate of 0.3mm/yr from the RSL record using the EIV-IGP model to estimate climate-driven sea-level trends and to facilitate comparison among sites. This analysis demonstrates that since ~0CE sea level did not deviate significantly from zero until accelerating continuously from ~1500CE to present. Sea level was rising at 1.33mm/yr in 1900CE and accelerated until 2014CE when a rate of 2.02mm/yr was attained, which is the fastest, century-scale trend in the ~2000-year record. Comparison to existing reconstructions from the Gulf coast of Louisiana and the Atlantic coast of northern Florida reveal similar sea-level histories at all three sites. We explored the influence of compaction and fluvial processes on our reconstruction and concluded that compaction was likely insignificant. Fluvial processes were also likely insignificant, but further proxy evidence is needed to fully test this hypothesis. Our results indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century.

Impact of eustatic and tectonic processes on the southeastern Mediterranean shelf during the last one million years: Quantitative reconstructions using a foraminiferal transfer function

Benthic foraminifera-based transfer function models provide accurate sea-level reconstructions for shelf and coastal environments around the world. This study presents for the first time results of a foraminiferal transfer function aiming at the reconstruction of relative sea-level in the southeastern Mediterranean shelf during the past one million years. A Weighted Averaging-Partial Least Squares (WA-PLS) regression method was used for the development of the transfer function based on an extensive set of surface samples (modern training data set) from the study area. The transfer function was applied to three shelf sediment successions retrieved from Haifa Bay, Israel. The Modern Analog Technique (MAT) and the random TF test were used to investigate similarity between modern and fossil foraminiferal faunas, testing the reliability and significance of our model for paleowater depth reconstruction. The performance of the WA-PLS transfer functions suggests a strong relationship between the observed and estimated water depths in the modern data set with relatively precise reconstructions of 7.0m (Root Mean Squared error of Prediction) over a water depth range of 3 to 80m. The deepest paleo water depths were reconstructed for the earliest sea-level highstands recorded in the sediment records (MIS 27? and MIS 29?) in the down-faulted boreholes due to tectonic movements, whereas the younger interglacial sedimentary units (MIS 25?, 13, 11, 7, 5.5 and 1) were mostly deposited at <15m water depths or slightly deeper during MIS 7. The relative sea-level history of the southeastern Mediterranean shelf reveals deviations from the global sea-level trend during MIS 5.5, which may have resulted from minor tectonic movements in the study area and/or un-representation of the phase of maximum sea-level in the sediment succession. Our paleowater depth estimates demonstrate a shallowing trend during the Holocene, generally matching other regional Mediterranean sea-level records.

Late Quaternary paleoceanographic evolution of the Aegean Sea: planktonic foraminifera and stable isotopes

Aspects of the paleoclimatic and paleoceanographic evolution of the Aegean Sea since ~130 ka are revealed by quantitative variations in planktonic faunal assemblages, the Δ18O and Δ13C isotopic composition of benthic and planktonic foraminifera, and Mg/Ca ratios in planktonic foraminifera extracted from five 6-10-m-long piston cores. Independent sea surface temperature (SST) estimates obtained using planktonic foraminiferal transfer functions and the Mg/Ca ratios show excellent agreement, with r2 correlation coefficients of 0.92-0.95. Planktonic foraminiferal assemblages are similar, through time, across several deep basins, suggesting that major changes must have occurred in near synchroneity across the Aegean Sea. The data suggest that sapropels S3, S4, and S5 were deposited under a stratified water column during times of increased primary productivity and the development of a deep chlorophyll maximum layer. Under such conditions, oxygen advection via intermediate water flow must have been significantly reduced, in turn implying bottom water stagnation. Sapropel S1 lacks a deep phytoplankton assemblage; this faunal contrast between S1 and older sapropels indicates that S1 must have been deposited in the absence of a deep chlorophyll maximum layer. Cluster analysis shows a consistent coupling of Globigerina bulloides with Globigerinoides ruber during times of nonsapropel deposition, interpreted to require a stratified euphotic zone composed of a warm, nutrient-poor upper layer and a cooler, nutrient-rich lower layer. The covariation of these two species suggests increased river runoff that controlled the fertility and stratification of the surface waters.

A quantitative reconstruction of the paleoenviornmental variations of the South Yellow Sea inner shelf based on benthic foraminiferal transfer functions

Transfer functions between the benthic foraminiferal fauna of seventy-one sediment surface-samples retrieved from the South Yellow Sea inner shelf and the environmental factors, including the summer bottom-water salinity (S (s)), the summer bottom-water temperature (T (s)) and the winter bottom-water temperature (T (w)) have been developed utilizing weighted averaging partial least square regression (WA-PLS). Subsequently, the transfer functions have been applied to a late Holocene piston core SY01 from the South Yellow Sea inner shelf, established the variation curves of the S (s), T (s), and T (w) during the last 3.9 cal. ka. The S (s) and T (s) showed a nearly synchronous trend to the published stalagmite delta O-18 curve from the Jiuxian Cave, meaning they could be used as reliable indicators for the summer monsoon. Similarly, the T (w) could be used as an indicator for the winter monsoon for its synchronous change to the insensitive grain size variation of the core ZY-2 retrieved from the Central Yellow Sea mud area. These results suggest that transfer functions based on benthic foraminiferal fauna can be a potentially useful tool in palaeoceanographic and palaeoenvironmental research along the Chinese seaboard.

Sediment transport on the inner shelf off Khao Lak (Andaman Sea, Thailand) during the 2004 Indian Ocean tsunami and former storm events: evidence from foraminiferal transfer functions

Abstract. We have investigated the benthic foraminiferal fauna from sediment event layers associated with the 2004 Indian Ocean tsunami and former storms that have been retrieved in short sediment cores from offshore environments of the Andaman Sea, off Khao Lak, western Thailand. Species composition and test preservation of the benthic foraminiferal faunas exhibit pronounced changes across the studied sections and provide information on the depositional history of the tsunami layer, particularly on the source water depth of the displaced foraminiferal tests. In order to obtain accurate bathymetric information on sediment provenance, we have mapped the distribution of modern faunas in non-tsunamigenic surface sediments and created a calibration data set for the development of a transfer function. Our quantitative reconstructions revealed that the resuspension of sediment particles by the tsunami wave was restricted to a maximum water depth of approximately 20 m. Similar values were obtained for former storm events, thus impeding an easy distinction of different high-energy events.

Changes in planktic foraminiferal faunas, temperature and salinity in the Gulf Stream during the last 30,000 years: influence of meltwater via the Mississippi River

Variations in the distribution of planktic foraminiferal faunas, temperature and salinity in the surface water of the Gulf Stream during the last 30,000 years have been reconstructed based on a sediment core from the Blake Ridge, subtropical western Atlantic Ocean. Temperatures and salinities were calculated using planktic foraminiferal transfer functions and previously published oxygen isotope values. Productivity was estimated using the >106 μm size fraction of planktic foraminifera. The reconstructed values show that temperature variations have been small during the investigated period with a total range of only 3 °C. The highest temperatures, about 1.5 °C above the present temperature in the area, occurred during the late Glacial, Heinrich event 1 and the mid Holocene time periods. The lowest temperatures, about 1.5 °C below the present temperatures, occurred during the Bølling interstadial. The early Holocene period was relatively cool. The low temperatures during the Bølling interstadial and during the early Holocene are in contrast to the northeastern Atlantic, where the Bølling interstadial was the warmest period of the deglaciation, and the early Holocene the warmest during the Holocene. We attribute the lower temperatures during the Bølling and early Holocene periods to colder meltwater from the Laurentide Ice Sheet flowing into the Gulf of Mexico through the Mississippi River system and carried to the Blake Ridge via the Gulf Stream.

The effect of sea surface properties on shell morphology and size of the planktonic foraminifer Neogloboquadrina pachyderma in the North Atlantic

The variability in size and shape of shells of the polar planktonic foraminifer Neogloboquadrina pachyderma have been quantified in 33 recent surface sediment samples throughout the northern Atlantic Ocean and correlated with the properties of the ambient surface waters. The aim of the study was to determine whether any of the morphological features could be used to reconstruct sea surface properties in the polar realm of the North Atlantic, where most paleotemperature proxies appear to fail. The analyses revealed that shell morphology is only weakly controlled by habitat properties, whereas shell size showed a strong correlation with sea surface temperature. The regression of mean shell size on sea surface temperature revealed the presence of two trends among the sinistrally coiled shells: a continuous increase in shell size with decreasing SST in sediments deposited under polar water masses and a continuous increase in shell size with increasing SST in samples from transitional waters. The second trend mirrors the trend observed for dextrally coiled shells, which are frequent in the same samples and signal the presence of N. incompta. The identical mean shell size trends among the sinistral and dextral specimens in the temperate samples confirms the results of earlier genetic studies which indicated the existence of a small but distinct proportion of opposite coiling in N. incompta, to which the sinistral shells in the temperate samples could be attributed. The linear correlation between mean shell size and sea surface temperature in the polar domain (summer SST<9°C) has been used to develop an empirical formula for the reconstruction of past sea surface temperatures from shell sizes in fossil samples. The standard error of the residuals of the linear regression is 2.36°C (1 sigma), which implies a much larger error than for most paleothermometers, but enough precision to allow resolution between results by individual paleothermometers in the polar domain. The resulting regression model has been applied on two sediment cores spanning the interval from the Last Glacial Maximum (LGM) to the present day. The results from core PS1906-1 are consistent with ice-free conditions during the LGM in the Norwegian Sea. The SST estimates for the LGM inferred from N. pachyderma shell size are similar or slightly higher than those for the latest Holocene. The results do not indicate anomalously high SST during the glacial and the LGM reconstructions thus appear more consistent with the results from foraminiferal transfer functions and geochemical proxies. Both sediment cores show the highest reconstructed SST during the early Holocene insolation optimum.

Assessment of sea surface temperature changes in the Gulf of Cadiz during the last 30 ka: implications for glacial changes in the regional hydrography

Abstract. New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

Reassessing transfer-function performance in sea-level reconstruction based on benthic salt-marsh foraminifera from the Atlantic coast of NE North America

Abstract The need to increase the number and distribution of sea-level records spanning the last few hundred years has led to particular interest in developing high-precision, geologically based sea-level reconstructions that capture decimetre and multi-decadal scale changes. Transfer functions for tide level are statistical tools that quantify the vertical relationship between inter-tidal microfossils and elevation within the tidal frame and their use in sea-level reconstruction is growing in popularity. Whilst a range of sampling strategies, dataset qualities and underlying statistical models have been used in transfer-function development, all variants share the common requirement of accurately extracting precise species–elevation relationships from surface data, and reliably applying these to fossil assemblages to infer past conditions. We present surface foraminiferal data from six transects sampled at three sites spanning a large latitudinal range extending from Newfoundland (Canada) to North Carolina (USA). These data demonstrate that significant spatial differences exist within the high-marsh foraminiferal assemblages commonly used to reconstruct past relative sea-level (RSL). We standardise these data to account for inter-site differences in tidal range using several variants of the standardised water level index (SWLI) of Horton et al. (1999b) and show that the best performance is achieved by using the highest occurrence of foraminifera as the upper tidal datum level. The standardised surface foraminiferal data are used to develop a suite of foraminiferal transfer functions for tide level which are then applied to fossil assemblages from two sediment cores to reconstruct palaeomarsh-surface elevation. We highlight the manner in which species–elevation relationships are extracted and modified during transfer-function development, and the impacts that choices in dataset composition and transfer-function type have on the resulting reconstructions. Our results graphically illustrate the importance of these choices and the impacts of temporal and spatial variability in foraminiferal distributions, none of which are adequately represented or discernible from the standard summary statistics of performance that commonly accompany transfer-function reconstructions. We conclude that a more explicit treatment of the transfer-function development process is required to support the growing body of precise RSL reconstructions that are now appearing in the literature. To that end, we make the following four recommendations for a framework to assist in transfer-function development that will allow better record inter-comparison and minimise the potential for producing precise but ultimately inaccurate reconstructions: 1) sampling for surface data should focus on capturing complete species response curves rather than simply compiling modern analogues for fossil material; 2) The similarity between the surface assemblages used to produce transfer functions and the fossil assemblages to which they are applied, should be better quantified using a range of statistical approaches, and must accompany any reconstruction; 3) where modern analogues are lacking in local surface assemblages, data from additional sites should be added, with selection based on fulfilling the requirements of the previous two recommendations. The manner in which individual species optima are combined to produce a composite optimum, and the extent to which this provides a reasonable representation of the surface data should also be documented; 4) the application of WA PLS component 2 (and higher) cannot be justified solely on the grounds of increased performance measures (e.g. r2jack and RMSEP), and if applied, the pattern of optima updates should be used to highlight species that may distort reconstructions.

Paleobathymetric history of the Western Mediterranean Sea shelf during the latest glacial period and the Holocene: Quantitative reconstructions based on foraminiferal transfer functions

We present results of the palaeobathymetric evolution in cool-water shelf carbonate environments of the Western Mediterranean Sea during the latest glacial period and the Holocene. For this quantitative approach, we used the Weighted Averaging-Partial Least Squares (WA-PLS) regression method for the development of benthic foraminifera-based transfer functions, and the Modern Analog Technique (MAT) to test the robustness of the models. Transfer functions were created on the basis of recent benthic foraminiferal assemblages in surface samples (modern data sets), and were then applied to fossil samples in sediment cores from the Alboran Platform, the Oran Bight and the Mallorca Shelf. The performance of the WA-PLS transfer functions suggests a close relationship between the observed and estimated water depths in the modern data sets with a precision of ~ 11 m (Root Mean Squared error of Prediction (RMSEP)) within water depths ranging from 38 to 160 m. The estimated relative sea-level histories of the Alboran Platform and the Mallorca Shelf show a total relative sea-level rise of ~ 50 m with sample-specific errors of approximately ±7 m and generally match the global and regional Mediterranean Sea records. Inconsistencies in the paleobathymetric estimates are strongly attributed to redeposition processes, dating problems and to minor effects of an under-representation of modern samples from shallower water depths.

The application of intertidal foraminifera to reconstruct coastal subsidence during the giant Cascadia earthquake of AD 1700 in Oregon, USA

Changes in species assemblages of intertidal foraminifera can be used to estimate the amount of earthquake-related subsidence during plate-boundary earthquakes at the Cascadia subduction zone. The accuracy and precision of foraminiferal methods in paleoenvironmental reconstruction is underpinned by the relations between contemporary taxa and their environment, which are used to calibrate fossil foraminiferal assemblages in sediment sequences. A contemporary training set of surface sediment samples from five intertidal marshes along the Oregon coast was used to determine foraminiferal distributions and prevailing environmental control(s) along elevational transects. Dominant taxa include Balticammina pseudomacrescens, Trochamminita irregularis, Haplophragmoides wilberti, Trochammina inflata, Jadammina macrescens and Miliammina fusca. Unconstrained cluster analysis and detrended correspondence analysis was used to identify two elevation-dependent faunal zones: Faunal Zone I (upland, high marsh, middle marsh) dominated by Balticammina pseudomacrescens, Haplophragmoides wilberti and Trochammina inflata, and Faunal Zone II (low marsh and tidal flat) dominated by Miliammina fusca. Site-specific differences in assemblages at three marshes enabled further subdivision of Faunal Zone I. Zone Ia is based on one or more of Balticammina pseudomacrescens, Trochammina inflata, Trochamminita irregularis and Haplophragmoides sp., and Zone Ib on Jadammina macrescens, Haplophragmoides sp., Trochammina inflata and Miliammina fusca. Canonical correspondence analysis (CCA) and partial CCA of the training set from the Nehalem River marsh transect was used to infer that the zonation of foraminifera is elevation-dependent (39% of explained variance). A transfer function was developed to reconstruct sudden changes in relative sea-level during plate-boundary earthquakes in Oregon. The results indicate a robust performance of the transfer function ( r jack 2 = 0.82) with the error estimate (RMSEP jack = 0.20 m) comparable to local and regional transfer functions from other temperate marshes. To illustrate the potential of the technique, the transfer function was applied to reconstruct subsidence during the AD 1700 earthquake using at Alsea Bay, Oregon. The reconstruction (0.18 ± 0.20 m) is less than half the subsidence estimate of Nelson et al. [2008. Great-earthquake palogeoesy and tsunamis of the past 2000 years at Alsea Bay, central Oregon coast, USA. Quaternary Science Reviews, 27, 747–768] using their foraminiferal transfer function, perhaps because of differences in taxonomy and the species relationship to elevation.

Factors controlling the distribution of planktonic foraminifera in the Red Sea and implications for the development of transfer functions

The Red Sea is an extreme marine environment, with conditions limiting the application of standard geochemical proxies for the reconstruction of paleoclimate. In order to develop paleoenvironmental reconstruction methods which are not dependent on chemical signals, we investigated the distribution of planktonic foraminifera in the surface sediments and assessed the viability of constructing foraminiferal transfer functions in this basin. We find a distinct gradient in the faunal assemblage along the basin's axis, which is reflected in a high correlation between faunal composition and all considered environmental parameters (temperature, salinity, chlorophyll a concentration, stratification, and oxycline depth). As a result, transfer functions constructed by different methods (ANN, MAT, IKM, WA-PLS) appear to be able to estimate all of these parameters with a high average accuracy (15% of the parameter's range in the Red Sea). However, redundancy analysis of the distribution of foraminiferal assemblages in surface sediments alone did not yield unambiguous results in terms of which of the considered factors exerts a primary control on the foraminifera distribution and which of the observed relationships are the result of the mutual correlation among the environmental factors. To disentangle the effect of individual environmental parameters, we applied the obtained transfer functions on a newly generated Holocene record from the central Red Sea. The integration of published paleoclimate reconstructions with our data allowed us to identify productivity as the most likely primary control of the planktonic foraminifera distribution in the Red Sea. The generated transfer functions can estimate paleoproductivity with acceptable accuracy (RMSEP chlorophyll a = 0.1 mg/m 3; ~ 8% of recent range), but only under such conditions in the past when circulation patterns and salinity levels in the basin were fundamentally comparable to the present day. Since productivity in the central and southern Red Sea is closely linked with the Monsoon-driven water exchange across the Strait of Bab al Mandab, the resulting reconstructions can provide indirect information on the mode and intensity of the monsoonal system in the past.

Recent sea-level changes in the southern Bay of Biscay: transfer function reconstructions from salt-marshes compared with instrumental data

In order to assess the accuracy and regional significance of salt-marsh reconstructions of former sea level based on foraminiferal transfer functions, we compared the calibration of the foraminiferal assemblages of two salt-marsh cores from two estuaries using the regional transfer function constructed for the southern Bay of Biscay. The foraminifera-based reconstructions were placed into a temporal framework using 137 Cs, heavy metal concentrations, and 210 Pb-derived sediment accumulation rates. The resulting relative sea-level (RSL) curves were compared with the nearest tide-gauge data (Santander). The two RSL trends from core sediments show excellent agreement and are in very good agreement with instrumental data, providing a regional relative sea-level rise of 1.9 mm yr -1 for the 20th century.

Great-earthquake paleogeodesy and tsunamis of the past 2000 years at Alsea Bay, central Oregon coast, USA

The width of plate-boundary fault rupture at the Cascadia subduction zone, a dimension related to earthquake magnitude, remains uncertain because of the lack of quantitative information about land-level movements during past great-earthquake deformation cycles. Beneath a marsh at Alsea Bay, on the central Oregon coast, four sheets of tsunami-deposited sand blanket contacts between tidal mud and peat. Radiocarbon ages for the sheets match ages for similar evidence of regional coseismic subsidence and tsunamis during four of Cascadia's great earthquakes. Barring rapid, unrecorded postseismic uplift, reconstruction of changes in land level from core samples using diatom and foraminiferal transfer functions includes modest coseismic subsidence (0.4±0.2m) during the four earthquakes. Interpretation is complicated, however, by the 30–38% of potentially unreliable transfer function values from samples with poor analogs in modern diatom and foraminiferal assemblages. Reconstructions of coseismic subsidence using good-analog samples range from 0.46±0.12 to 0.09±0.20m showing greater variability than implied by sample-specific errors. From apparent high rates of land uplift following subsidence and tsunamis, we infer that postseismic rebound caused by slip on deep parts of the plate boundary and (or) viscoelastic stress relaxation in the upper plate may be almost as large as coseismic subsidence. Modest coseismic subsidence 100km landward of the deformation front implies that plate-boundary ruptures in central Oregon were largely offshore. Ruptures may have been long and narrow during earthquakes near magnitude 9, as suggested for the AD 1700 earthquake, or of smaller and more variable dimensions and magnitudes.

Reconstruction of sea-surface temperatures in Suruga Bay (central Japan) during oxygen isotope 6.5, using planktonic foraminiferal transfer functions

We reconstruct both summer and winter sea surface temperatures (SSTs) at around 177ka (marine isotope stage 6.5) from planktonic foraminiferal assemblages in the Kunosan Formation in the Udo Hills along Suruga Bay, central Japan. The results show that the SSTs were 2-3°C colder than today and are comparable to those at Kashimanada today. This may imply that the subtropical Kuroshio Front was located off Suruga Bay during MIS 6.5.

No-analog planktonic foraminiferal faunas in the glacial southern South China Sea: Implications for the magnitude of glacial cooling in the western Pacific warm pool

Sea-surface temperature (SST) estimates in the sediment core MD01-2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern South China Sea (SCS) during the Last Glacial Maximum (LGM) relative to modern temperatures. These results are in contrast to substantial cooling of 2–5 °C inferred by geochemical (U k' 37, Mg/Ca ratios) and terrestrial proxies from the western tropical Pacific region. Using multivariate statistics we show that the glacial southern SCS harboured unique planktonic foraminiferal assemblages that have no modern analogs. Analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from Mg/Ca data but that this signal is subdued by superimposed variations in the relative abundance of Pulleniatina obliquiloculata and Neogloboquadrina pachyderma (dextral). These species occur in glacial samples at proportions that are not observed in the calibration data set. The glacial high abundance of N. pachyderma (dextral) are interpreted to reflect a seasonal (winter) inflow of cold surface water from the northeast via the Bashi Strait due to the combined effects of an intensified winter monsoon, a southward shift of the polar front and the eastward migration of the Kuroshio Current. In contrast, processes controlling the high relative abundances of P. obliquiloculata during the LGM may be unique to the southern SCS. We propose a scenario involving a stronger (winter) mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow-dwelling, warm indicators to establish larger populations during the LGM. Our results indicate that a no-analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western Pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical (Mg/Ca ratios; alkenone unsaturation index) marine proxies is a more likely scenario.