Interactive comment on “ Crustal uplifting rate associated with late-Holocene glacial-isostatic rebound at Skallen and Skarvsnes , Lützow-Holm Bay , East Antarctica : evidence of a synchrony in sedimentary and biological facies on geological setting ”

The initial decision of the two reviewers was to reject the paper. The reviewers identified major issues with the methodology, such as doubt about the applicability of 16S rRNAbased DGGE profiling to increase the accuracy of the reconstructed geo-history; the need for correction of C14 dates (and error bars) for the marine reservoir effect because it has important implications for the calculation of the uplift rate and its comparison with


Introduction
Previous studies have modeled glacial rebound and sea-level change arising from the recession of large-scale continental ice sheets since the Last Glacial Maximum (LGM), which led to eustatic sea-level changes and glacio-isostatic responses in Antarctica (e.g.Nakada and Lambeck, 1989;Lambeck, 1993;James and Ivins, 1998;Bentley, 1999;Yokoyama et al., 2001;Anderson et al., 2002;Huybrechts, 2002;Ivins  and James, 2005;Yokoyama et al., 2006).Since the initial work of Yoshikawa and Toya (1957), studies undertaken in the L ützow-Holm Bay area of East Antarctica have advanced our knowledge of relative sea-level change during the Holocene.Geological approaches involving techniques such as bedrock GPS and VLBI (Very Long Baseline Interferometry) measurements (e.g.Yoshida and Moriwaki, 1979;Hayashi and Yoshida, 1994;Igarashi et al., 1995;Kaminuma et al., 1996;Maemoku et al., 1997;Miura et al., 1998a, b, c;Soudarin et al., 1999;Shibuya et al., 2003;Fukuzaki et al., 2005;Ohzono et al., 2006).Maemoku et al. (1997) suggested that the East Antarctic Ice Sheet (EAIS) covered the southern part of L ützow-Holm Bay during the LGM.The Holocene marine limit along the Soya Coast is estimated to have been approximately 18 m above mean sea level (a.m.s.l.), based on analyses of indigenous raised beach deposits such as bivalve fossils (Laternula elliptica: Miura et al., 1998c) combined with modeling studies (Nakada et al., 2000), which indicate considerable regional isostatic rebound in response to a reduction in ice volume.Based on these studies, it was concluded that most of the present-day ice-free areas along the southern Soya Coast had become free of the EAIS by the mid-Holocene (Miura et al., 1998c).As an endemic suspension feeder, radiocarbon dating of fossil L. elliptica tests is a potentially valuable means of assessing past relative sea-level changes.However, such applications are potentially limited by our understanding of the ecological characteristics of L. elliptica, thus requiring further consideration of the significance of these fossil dates.
The advances made in the above studies have led to the development of plausible models of crustal movement within coastal areas in East Antarctica.Although little is known of the geology of the Soya Coast within L ützow-Holm Bay, sedimentary facies exposed in ice-free coastal areas provide important clues in reconstructing the paleo-environment (e.g.Matsumoto et al., 2006).In this study, we focus on temporal variations in the chemical and microbiological assemblages of sediments recovered from two lakes (at Skallen and Skarvsnes) along the Soya Coast, L ützow-Holm Bay.We identified marine-lacustrine transitions recorded in the lake sediments with the aim of accurately determining the timing of emergence.Our data are combined Figures

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Full with previously published raised beached dates using L. elliptica, thereby enabling the development of a quantitative approximation model of the mean crustal uplifting rate during the late Holocene.
2 Materials and method 2.1 Geological location and sampling Imura et al. (2003) and co-workers documented the spatial distribution of lakes upon the continental ice margin of the Soya Coast region, revealing a wide variety of profiles ranging from freshwater lakes affected by continental glaciers to saline lakes that evaporated following their isolation from the ocean in response to Holocene uplift.Skallen is a 14.1 km 2 ice-free coastal area of rocky hills located in east L ützow-Holm Bay (Fig. 1).
Figure 2 shows photographs of the landscape in this area and of the water inlet and outlet at Lake Skallen Oike (hereafter L. Skallen; see Table 1), which is located in central Skallen.Skarvsnes is the largest ice-free area (61 km 2 ) along the Soya Coast.Lake Oyako (hereafter L. Oyako) is located within Skarvsnes, near Kizahashi Beach (Miura et al., 1998c).These two lakes are presently separated from the open ocean by sills with heights (overflowing points) of 10 and 5 m a.m.s.l., respectively.The present tidal range along Soya coast is within ca.±0.5 m (e.g.Aoki et al., 2000).Lake sediments were collected from these lakes using push-type corers during the 47th Japan Antarctica Research Expedition (December 2005 to February 2006; see the core images in Fig. 3).The cores were cut into 3-10 cm intervals and stored at 0-4 • C or −20 • C for onshore geochemical analysis and 16S rRNA analysis, respectively.

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Opal-A was identified by X-ray diffraction (XRD, Mac Science Co. Ltd.) to acquire the signal of amorphous biogenic silica derived from diatoms, namely siliceous primary producers.Color data were obtained using a digital color meter (SPAD 503, Konica Minolta) and revised Standard Soil Color Charts (e.g.Oyama and Takehara, 2005).
After HCl pretreatment for freeze-dried sediments, carbon and nitrogen isotopic ratios were mainly determined using an isotope ratio mass spectrometer (IRMS; Delta Plus XP, ThermoFinnigan) coupled with a Flash elemental analyzer (EA; EA1112, Ther-moFinnigan) via a Conflo III interface (e.g.Ohkouchi et al., 2005).For a small number of analyses we also used an elemental analyzer-isotope ratio mass spectrometer (Costech 4010 Elemental Analyzer; ThermoFinnigan Delta plus Mass Spectrometer).Carbon and nitrogen isotopic compositions are expressed as the per mil (‰) deviation from the standard, as follows: for carbon and δ 15 N=[( 15 N/ 14 N) sample /( 15 N/ 14 N) standard −1]×1000 (‰) for nitrogen.Elemental analyses of carbon, nitrogen, and sulfur were performed using a Micro CORDER JM10 (J-Science Lab Co., Ltd.).Some of the sedimentary organic carbon fractions after HCl pretreatment were analyzed to obtain radiocarbon age ( 14 C), corrected after the δ 13 C value, using an accelerator mass spectrometer (AMS) housed at the University of Tokyo, Japan (Yokoyama et al., 2007), and by Beta Analytic Inc., Florida, USA.
In order to refine our uplift model, we re-assessed previously published radiocarbon ages of fossil L. elliptica shells sampled from raised beaches.In particular, we reconsidered the depth habitat, based on a review of ecological literature, in order to more accurately determine the age of sedimentation of these fossils.Introduction

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Diatom analysis to confirm biological facies
In addition to chemical analysis for amorphous biogenic silica, sediments from core Sk5S were prepared for diatom analysis following a standard procedure, involving heating (70 6•C) in hydrogen peroxide to remove organic matter, followed by the addition of 10% HCl to remove carbonates (Battarbee et al., 2001).Following chemical treatment, samples were rinsed three times in de-ionized water and concentrated by centrifugation (1500 rpm).The residual diatom material was mounted upon microscope slides using Norland ® optical adhesive, and fixed under ultraviolet light.A minimum of 300 diatoms were counted per sample using phase-contrast light microscopy at 400× and 1200× (oil immersion) magnification, following Hirano (1983), Krammer and Lange-Bertalot (1986, 1988, 1991a, b), Medlin and Priddle (1990), and Spaulding et al. (2008).

Geochemistry and nitrogen isotopic compositions of sedimentary facies
In the core sediments, we observed distinct soft-mat laminations made up of microbial mat, silt and clay layers, unaffected by bioturbation (Fig. 3).The upper sections of core Sk5S (from L. Skallen) consist of soft dark-black microbial mat with olive black, greenish black, and bluish black coloring, while the lower sections of the core are largely gray to dark gray (Fig. 3a and c).Although the reason is unconfirmed, a sediment deformation was observed at the depth of 260 cm in L. Skallen, likewise 110 cm in Ok5S (see also Fig. 4).Since we could not distinguish the sedimentary facies by the sediment color monitoring and lithological description, we conducted geochemical analysis including major element and nitrogen isotopic composition.
Figure 4 shows depth profiles of chemical trends in the two cores.Lake sediments within cores Sk5S (L.Skallen) and Ok5S (L.Oyako) record a transition from marine to lacustrine conditions including temporal brackish conditions, as indicated by various Introduction

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Full chemical components such as carbon and nitrogen contents, nitrogen isotopic compositions, and major element contents (Fig. 4).The total carbon (TC) content shows a marked increase beginning at 180 cm depth in core Sk5S and 90 cm depth in Ok5S.In Sk5S, the sedimentary TC content is less than 4 wt% in sediments deeper than 180 cm, but is up to 7.9 wt% immediately above 180 cm and 19.7 wt% at 45 cm depth.Although the trend is less clear in Ok5S, the TC content jumps from 2.5 to 6.4 wt% passing upward across 90 cm depth.Similar trends are observed in both cores in profiles of total nitrogen (TN) and C/N.In Sk5S, total sulfur (TS) content is strongly elevated at 80-180 cm depth, probably reflecting the accumulation of sulfides under meromictic conditions.The nitrogen isotopic composition (δ 15 N) of bulk organic matter within lake sediments shows a significant shift at the marine-lacustrine transition.Representative values of +6.1‰ at the mid-depth of 315.0 cm in Sk5S and +6.7‰ at the mid-depth of 151.5 cm in Ok5S are indicative of marine sediments (Fig. 4), whereas the 15 Ndepleted isotopic composition of shallow sediments within the cores (∼0‰) suggests that nitrogen assimilation occurred in a freshwater environment.

Major components of sedimentary facies and opal-A signatures in marine stage
The compositional trends of inorganic major elements also indicate a marked marinelacustrine transition in each of the cores (Fig. 4).The lower, marine sediments in both lake cores were substantially SiO 2 -enriched (<73% in Sk5S; <57% in Ok5S) indicating high SiO 2 end-member values for the marine sediments and low SiO 2 associated with more recent freshwater conditions.The mixture of these two end-members can be illustrated in a SiO 2 -Al 2 O 3 diagram, in which contrasting mixing trends are observed across 180 cm depth in core Sk5S and 90 cm depth in core Ok5S (Fig. 5).In both cores, the high SiO 2 end-member compositions suggest a large contribution by biogenic silica in Antarctic seawater (Cortese et al., 2004)  that in shallower parts (165 cm), supporting the biological origin of this silicate (Fig. 6).
The reduction in opal-A abundance within the shallower part of the section suggests a decrease in diatom abundance, possibly associated with a net reduction in productivity, an increase in non-silicate photoautotrophs such as cyanobacteria (unpublished data) and an increase in dilution by minerogenic matter.It is interesting to note that Fe 2 O 3 (wt%) in the Sk5S sediment was negatively correlated with SiO 2 (wt%) and positively correlated with total C&N contents.Based on the Fe 2 O 3 -Al 2 O 3 plot, the main deposition source of iron oxide in L. Skallen might have changed during the marinelacustrine transition, while L. Oyako has followed a constant trend.Bed-rock is one of possible sources of iron oxide imported from seeping ground water/surface water and wide catchment basin in the L ützow-Holm Bay region (e.g.Kawakami and Motoyoshi, 2004; see also Fig. 2).X-ray diffraction analyses of sediment from core Sk5S indicate abundant opal-amorphous (opal-A) in deeper parts of the section (355 cm) relative to that in shallower parts (165 cm), confirming the biological origin of silicate (Fig. 6).The reduction in opal-A abundance within the shallower part of the section suggests a decrease in diatom abundance and an increase in non-silicate photoautotrophs such as cyanobacteria (unpublished data).

Radiocarbon age determination of sedimentary organic matter
The geochemical data indicate that environmental change (i.e., a marine-lacustrine transition) associated with disconnection of the lakes from marine conditions occurred at 180 cm depth in core Sk5S (L.Skallen) and 90 cm depth in Ok5S (L.Oyako).We obtained AMS radiocarbon dates for organic matter in the cored sediments both above and below these depths (Fig. 4 and Table 2).Yoshida and Moriwaki (1979)  and 90 cm depth in Ok5S as a DIC (dissolved inorganic carbon) reservoir correction (Yoshida and Moriwaki, 1979;Hayashi and Yoshida, 1994;Ingolfsson et al., 1998).
We did not perform reservoir corrections for radiocarbon dates obtained for sediments from the lacustrine stage, as the carbon residence time is considered to have been negligible for the sediments dated to yield marine DIC reservoir ages.Indeed, the radiocarbon ages of freshwater lacustrine lake sediments in East Antarctica including those at Langhovde, Skarvsnes, and West Ongul Island over the past 2300 years show a linear trend (Matsumoto et al., 2006).Under these protocols, we obtained ages for the marine-lacustrine transition of 2940±100 cal yr BP for L. Skallen and 1060±90 cal yr BP for L. Oyako, thereby providing emergence ages for these two areas (Fig. 4).Relative sea-level change is recorded in the analyzed lake sediments as a marine-lacustrine transition arising from sea-level change and crustal uplift of the basin sills (Fig. 8).We also estimated the age of the first sediments deposited at the two sites following deglaciation (Figs. 4 and 8).Based on ages obtained for the lowermost sediments in each core, initial sedimentation process started by at least 5293-5559 cal yr BP (2 σ) at L. Skallen and by 1383-1610 cal yr BP (2 σ) at L. Oyako.

Biological facies of fossil diatoms and the marine-lacustrine transition
The transition from marine to freshwater conditions is clearly documented by sedimentary diatom assemblages in the core from L. Skallen (Fig. 6c), consistent with the geochemical data.Below 200 cm depth in the core, over 70% of the diatoms and other siliceous microfossils are typical of coastal marine taxa, including various Thalassiosira species, Fragilariopsis curta (Van Heurck) Hustedt, Amphiprora sp.ovalis K ützing.Such taxa are typically brackish (Fukushima, 1962), suggesting the influence of coastal/estuarine conditions at some stage during the depositional period.
The relative abundance of estuarine taxa increases at depths of less than 200 cm in the core, coinciding with a decrease in the abundance of marine phytoplankton.Marine taxa are scarce above 175 cm depth, replaced by a predominantly freshwater flora of low diversity.Diversity is lowest in the uppermost sediments (between 15 and 150 cm depth), where diatom assemblages are dominated by Amphora oligotrophenta Howarth, Navicula arcuata Heiden in Drygalski, and Navicula molesta Krasske in Hustedt, with lesser concentrations of Stauroneis anceps Ehrenberg, Diploneis subcincta (A.Schmidt) Cleve, Navicula gregaria Donk in Cleve-Euler, Achnanthes hankiana Grunow, and Amphora ovalis K ützing.All of these taxa can be found in contemporary lake environments in the Skarvsnes area (Hirano, 1983) and in freshwater creeks in the McMurdo Dry Valleys region of Antarctica (Spaulding et al., 2008).
The transition from marine to freshwater conditions is clearly documented by sedimentary diatom assemblages in the core from L. Skallen (Fig. 6c), consistent with the geochemical data.Below 200 cm depth in the core, over 70% of the diatoms and other siliceous microfossils are typical of coastal marine taxa, including various Thalassiosira species, Fragilariopsis curta (Van Heurck) Hustedt, Amphiprora sp., numerous Chaetoceros spores, and the silicoflaggelate Distephanus speculum (Ehrenberg) Haeckel.The freshwater-tolerant taxa within these sediments include Achnanthidium brevipes (C.Agardh) Cleve, Navicula directa (W.Smith) Ralfs, Cocconeis imperatrix M. Peragallo, Pinnularia quadraterea var.bicuneata Heiden and Kolbe, and Amphora ovalis K ützing.Such taxa are typically brackish (Fukushima, 1962), suggesting the influence of coastal/estuarine conditions at some stage during the depositional period.
N. arcuata has been reported from freshwater ponds at Skarvsness (Hirano, 1983) and Akebono Rock (Fukushima et al., 1989), and N. molesta has been collected from freshwater habitats around the Syowa base of the Ongul Islands (Ko-Bayashi, 1965).However, the dominance of A. oligotrophenta in particular might indicate a continuation of brackish conditions through to the present day. A. oligotrophenta is considered Introduction

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Full a mesohaline diatom, and is cosmopolitan across saline lakes within the European Diatom Database (http://craticula.ncl.ac.uk/Eddi/jsp/index.jsp);however, its abundance appears to be optimal in less-saline waters with a low conductivity (<3 µS/cm).A similar development of A. oligotrophenta (described as A. veneta and A. veneta var.capitata) was observed in the sediments of the coastal brackish Pup Lagoon at Larsemann Hills and interpreted as indicating saline lacustrine conditions following isolation (Gillieson, 1991;Verleyen et al., 2004).The upper sediments of Pup Lagoon is characterized by a ubiquitous cyanobacterial mat that is also evident throughout recent non-marine sediments of L. Skallen.Therefore, it is also possible that the low-diversity flora within the upper sediments of L. Skallen reflect a symbiotic, periphytic relationship between the dominant taxa (A.oligotrophenta and N. arcuata) and the cyanobacterial mat.

Phototrophs determined 16S rRNA and the marine-lacustrine transition
The PCR-DGGE analysis was performed to derive independent evidence for changes in the biota of L. Skallen through time based on DGGE band preserved within the sediment profile (Fig. 7).In the region shallower than 190 cm, DGGE band patterns varied according to depth although several bands were detected throughout a broad range of sediment depths.In contrast, sediment samples deeper than 190 cm exhibited almost identical band patterns, characterized by two predominant bands (skA and skB).These two bands had identical nucleotide sequences, which were very closely related to that from the chloroplast of the marine diatom, Chaetoceros socialis (identity = 526/528 BP).It is very likely that this sequence originated from marine diatoms buried within the sediment.Marine diatom related bands were not detected in the shallower layers, suggesting a change in the biota of L. Skallen Oike through time.Band skC was detected in the depth range of 160 to 200 cm, and closely related to cyanobacteria of the genus Synechococcus.It is likely that the organism corresponding to this band existed within the water column or surface sediments during the depositional age corresponding to these layers.However, the other sequenced DGGE bands (labeled in Fig. 7) were closely related to heterotrophic bacteria or only distantly related to cultured Introduction

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Full bacterial strains.As to these bands, it is impossible to judge whether they had been preserved in the sediment since their deposition, or were actively growing within the sediment.

Holocene crustal uplift rate around L ützow-Holm Bay
Model predictions of crustal motions and gravity changes driven by glacial isostatic adjustment (GIA) in West Antarctica indicate present-day peak GIA-related uplift rates of 14-18 mm yr −1 (e.g.Ellsworth Mountains region), with lower rates in the East Antarctic coastal region (Ivins and James, 2005).However, few studies have documented the emergence age of marine-lacustrine transitions in Antarctica.In the Lambert Glacier region, the relative uplifting rate and emergence age of Heart Lake and Pup Lagoon (in the Larsemann Hills) have been estimated to be 1.8-1.9mm yr −1 based on a linear extrapolation of dated marine-lacustrine transitions over the past 2800 cal yr BP (Verleyen et al., 2005).This figure is comparable to rates reported for the Vestfold Hills (Zwartz et al., 1998).
Based on comprehensive descriptions for the altitudes of present-day lakes, age determinations of the marine-lacustrine transitions at Lakes Skallen and Oyako (Fig. 9a), and possible off-set model from ecology in L. elliptica (Fig. 10), we estimate the mean crustal uplifting rates during the late Holocene in the L ützow-Holm Bay area.Here we consider a scheme for calculating the crustal uplifting rate, where t is defined as time in chronological order.The time t 0 represents the initial marine stage, and t 1 and t 2 represent the emergence age (i.e., the transition from marine to freshwater; a.m.s.l.t=1 ) and the present day (a.m.s.l.t=2 ), respectively (Fig. 8).Therefore, the crustal uplifting rate k is defined as k = (a.m.s.l.t=2 − a.m.s.l.t=1 )/(t 2 − t 1 ) Introduction

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Full where a.m.s.l.t=1 is equal to 0 m, representing the emergence event (marine-lacustrine transition) in time units of cal yr BP.Given that the present sill heights for L. Skallen and L. Oyako are 10 and 5 m a.m.s.l., respectively, the mean crustal uplifting rate k Sk,Ok (accuracy <0.5 m; see Aoki et al., 2000) is calculated to be 3.6 mm yr −1 (r 2 =0.97) for the period since the marine-lacustrine transition; i.e., over the past 2940 years at Skallen and past 1060 years at Skarvsnes (Eq. 3 in Fig. 9a).
The relative sea-level curve of the Vestfold Hills was estimated from marinelacustrine transition by Ace Lake, Anderson Lake, Highway Lake, Watts Lake, and Organic Lake (Roberts and McMinn, 1999;Zwartz et al., 1998).Subsequently, the relative sea-level curve of the Larsemann Hills was also estimated using data from Kirisjes Pond, Heart Lake, and Pup Lagoon (Verleyen et al., 2005).Hence, comparison of relative sea-level changes with other ice-free areas along the EAIS suggests that the present uplifting rate along the Soya Coast is greater than that in the Larsemann Hills and Vestfold Hills (Fig. 11).

Ecology of the suspension feeder bivalve, L. elliptica: an insight into habitat depth
In order to validate the first-order model of glacial-isostatic uplift rate derived from L. Skallen and L. Oyako (k Sk,Ok ), we compared these estimates with uplift rates based on radiocarbon dating of in situ marine mollusk fossils (L.elliptica) from raised beach deposits, described previously (Miura et al., 1998c) (Figs. 9 and 10).Radiocarbon dating of marine fossils around Antarctica is problematic because of the reservoir effect associated with melt water from the ice sheet and upwelling of Antarctic deep water.Furthermore, we cannot confirm the water depth of the habitat of marine fossils that lived below the paleo-sea level at which carbon fixation within indigenous shells occurred.Therefore, it is useful to consider the ecology and habitat preferences of L. elliptica prior to interpreting the radiocarbon composition of fossil remains.The estimated glacial-isostatic uplift rate presented above can be complemented by a Introduction

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Full re-assessment of radiocarbon dates obtained previously for the marine mollusk L. elliptica fossils (Miura et al., 1998c).L. elliptica is an endemic suspension feeder that is probably most common in water depths shallower than 20 m (Dell, 1990).It is widely distributed around Antarctica, occurring as dense patches in subtidal (sub-littoral zone) soft-sediment areas, and is one of the most conspicuous members of infaunal assemblages (e.g.Ahn, 1993;Urban and Mercuri, 1998;Jonkers, 1999;Cattaneo-Vietti et al., 2000;Ahn, 2001;Ahn et al., 2004;Norkko et al., 2004;Sato-Okoshi and Okoshi, 2008;Tatian et al., 2008).The vertical and spatial distribution of L. elliptica is mainly controlled by habitat stability and food availability in benthic environments (Ahn et al., 2003).In a study conducted at King George Island, Ahn (1994) reported that L. elliptica began to appear in the subtidal zone (depth >6-7 m) on the gentle slope.Ahn and co-workers estimated L. elliptica biomass at different water depths at several shore localities in Antarctica.
Ice impact in areas near intertidal (littoral) zones is a prevailing physical factor that affects the vertical distribution of L. elliptica.Below the ice-impact zone, optimum biological interactions (including the light regime and primary production) act as the main structuring force on the benthic community (Ahn, 1994;Ahn and Shim, 1998;Sahade et al., 1998).L. elliptica lives buried in the sediment (burrowing depth >50 cm) with the aid of large siphons, and reaches a length of approximately 100 mm over 12-13 years (Ralph and Maxwell, 1977;Zamorano et al., 1986).Since species-specific and regionspecific corrections have not yet been developed, we applied the general pre-bomb marine reservoir correction of 1300 years to the radiocarbon ages, following previous studies using emerged Antarctic marine fossils (Berkman et al., 1998).Considering this ecological context, we propose that the habitat depth of L. elliptica (below sealevel: meter, corresponding to life position within the subtidal water column), in combination with its burrowing depth (below the sea floor: meter, corresponding to siphon length > ca.0.5 m) yields a depth offset showing ∆H (Fig. 10), which in turn yields (∆T ) an age offset with regard to the calendar age model (Fig. 9b).Introduction

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Full  Miura et al. (1998c) compiled the ages of emerged beaches based on radiocarbon dating of L. elliptica fossils from along the Soya Coast, and reported two clusters of ages: a younger mid-Holocene group (3000-8000 yr BP, uncorrected for reservoir effects) and an older late-Pleistocene group (Fig. 9b).Nakada et al. (2000) examined sea-level variations at eight sites along the coast of Antarctica with the aim of reconstructing the melting history of the Antarctic ice sheet.These earlier studies were limited by uncertainty regarding the magnitude of Antarctic reservoir effects, especially for the late Holocene before ca.3000 yr BP.

Validity of linear approximation model of marine-lacustrine emergence age
To estimate relative sea-level change for a previously neglected period during the past 3000 yr BP, we fitted a linear approximation model (Fig. 9a) with an emergence age based on the ages obtained for the marine-lacustrine transitions and the ages of in situ L. elliptica collected from Skarvsnes and Langhovde (Maemoku et al., 1997;Miura et al., 1998a, b, c), calibrated using a calcareous marine reservoir correction (Berkman et al., 1998).Bearing in mind the above ecological description of the living environment of L. elliptica, we interpreted the offset of chronological time and sea-level record of L. elliptica using Eqs.( 2) and (3) (Fig. 9).The maximum possible water depth of the subtidal environment is represented as the difference between the value of a.m.s.l. on Eqs. ( 2) and ( 3) in the a.m.s.l.(m) axis (∆H: habitat depth below sea-level and below the sea floor during the lifecycle of L. elliptica with thickness of re-deposition sediment).The resulting emergence age (cal yr BP) gives a crustal uplifting rate k Sk,Ok of 3.6 mm yr −1 (r 2 =0.97, this study).Based on a linear approximation model (Fig. 9b), we propose k L. el l i pti ca (1) and k L. el l i pti ca (2) (rate constant k of Eqs. 1 and 2, respectively) to be 3.9 mm yr −1 (r 2 =0.68) and 3.2 mm yr −1 (r 2 =0.68), respectively.Hence, the burial age (∆T ) of fossilized L. elliptica would correspond to the difference between Eqs. ( 2) and ( 3) along the time (cal yr BP) axis (see Fig. 10).Although we cannot confirm the precise paleo-sealevel values associated with L. elliptica and its exact marine reservoir effect (e.g.Hayashi and Yoshida, 1994;Berkman et al., 1998;Ingolfsson et al., 1998), Introduction

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Full we presume that the linear approximation obtained between emergence age (Fig. 9a) and L. elliptica age (Fig. 8b; Miura et al., 1998c) represents the mean uplifting rate associated with regional isostatic rebound during the late Holocene.

Conclusions
In a study of the Soya Coast, L ützow-Holm Bay, East Antarctica, we investigated the sedimentary facies, biological facies, and crustal uplift rates based on the timing of marine-lacustrine transitions associated with regional glacio-isostatic rebound during Holocene deglaciation in EAIS.A combination of inorganic geochemistry and nitrogen isotope analysis of organic matter, supplemented by diatom species assemblages and fossil DNA and 16S rRNA for Lake Skallen, clearly document a transition from a marine to freshwater aquatic environment in both lakes, with the transition occurring in 2940±100 cal yr BP at L. Skallen and 1060±90 cal yr BP at L. Oyako.Based on these estimates, the crustal uplift rate of the Soya Coast was faster than other ice-free areas such as Lambert glacier region and Vestfold Hills.These differences are probably due to differing geological settings: the late Holocene deglaciation was the primary factor in controlling the emergence of L ützow-Holm Bay region and also in generating simultaneous changes in sedimentary and biological facies.Our estimate of the crustal uplift rate is supported by a regional survey of radiocarbon dates of fossils of the endemic suspension feeder L. elliptica.An improved understanding of the ecology of these organisms would represent a key advance in integrating geological and geochemical age models for the precise determination of the rate and extent of crustal uplift during the late Holocene.Introduction

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Full ).The assistance of E. Takeda (Hokkaido University) with microbial community analysis, M. Saito-Kato (Natl.Museum, Japan) and R. Jordan (Yamagata University) with diatom taxonomy and the provision of reference materials is greatly appreciated, as is the contribution of S. Darroch (Tokyo University) for assistance in the preparation of diatom slides.This research was supported in part by the Japan Society for the Promotion of Science (Y.T, N.O, and J.J.T), the Global Environment Research Fund (Y.Y) and REGAL project of NIPR (S.Imura and H. Kanda).The present research activities were also collaborative work during International Polar Year (IPY 2007(IPY -2008)).

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Full   The Larsemann Hills curve was based on the sediment sequences from Kirisjes Pond, Heart Lake, and Pup Lagoon (Verleyen et al., 2005).The marine-lacustrine transitions of those three lakes were plotted.The Vestfold Hills curve was based on sediment sequences from Ace lake, Anderson lake, Highway lake, Watts lake, and Organic lake (Roberts and McMinn, 1999;Zwartz et al., 1998).The Holocene marine-limit of Ace lake was noted.
Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and in turn indicating an abundance of diatoms (Figs. 5 and 6).X-ray diffraction analyses of sediment from core Sk5S indicate abundant opal-amorphous (opal-A) in deeper parts of the section (355 cm) relative to Discussion Paper | Discussion Paper | Discussion Paper | undertook radiocarbon dating of the raw flesh and shell of living marine benthic organisms (Neoliuccinum eatoni, Ophionotus victoriae, Sterechinus neumayeri, Trematomus berunacchii, and Zoarcidae sp.), yielding a mean value of 1120 yr BP; this value is employed as a correction factor in the present study.Before calibrating to calendar ages, we subtracted 1100 years from radiocarbon dates obtained below 180 cm depth in Sk5S Discussion Paper | Discussion Paper | Discussion Paper | , numerous Chaetoceros spores, and the silicoflaggelate Distephanus speculum (Ehrenberg) Haeckel.The freshwater-tolerant taxa within these sediments include Achnanthidium brevipes (C.Agardh) Cleve, Navicula directa (W.Smith) Ralfs, Cocconeis imperatrix M. Peragallo, Pinnularia quadraterea var.bicuneata Heiden and Kolbe, and Amphora Introduction Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | experiments were partly supported by H. Matsuzaki (University Tokyo Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Ingolfsson, O., Hjort, C., Berkman, P. A., Bjorck, S., Colhoun, E., Goodwin, I. D., Hall, B., Hirakawa, K., Melles, M., Moller, P., and Prentice, M. L.: Antarctic glacial history since the Last Glacial Maximum: an overview of the record on land, Antarct.Sci., 10, 326-344, 1998.Ivins, E. R. and James, T. S.: Antarctic glacial isostatic adjustment: a new assessment, Antarct.
Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Matsumoto, G. I., Komori, K., Enomoto, A., Imura, S., Takemura, T., Ohyama, Y., and Kanda, H.: Environmental change in Syowa station area of Antarctica during the last 2300 years inferred from organic components in lake sediment cores, Polar Biosci., 19, 51-62, 2006.Medlin, L. K. and Priddle, J.: Polar marine diatoms, British Antarctic Survey, Natural Environmental Council, Cambridge, 1990Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Fig. 1 .
Fig. 1.Map showing the distribution of ice-free areas (Rundv ågshetta, Skallen, Skarvsnes, and Langhovde) along the Soya Coast, East Antarctica.Arrows indicate the ice-flow directions of present-day outlet glaciers (seeSawagaki and Hirakawa, 1997).Also shown are detailed location maps of Lake Skallen Oike at Skallen and Lake Oyako at Skarvsnes.Topographic contours are based on compilation data from the Geographical Survey Institute(1973, 1987).
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Table 5 .
Summary of fossil diatom data showing the relative abundance of freshwater and marine species in L. Skallen.