The current saline state of the Black Sea is only the latest of a series of freshening-salinization episodes that have affected that body of water during past glacial–interglacial cycles. Here, we model the salinity history of the basin and its sedimentary porewaters since the end of the penultimate saline period, variously thought to have occurred in the period between ∼128 and ∼65 Kyr BP. Our model results argue that the down-core salinity profiles of Black Sea Holocene sediments have been affected by the diffusion of salt from the penultimate saline episode. Retrodiction of these porewater profiles also requires that the Black Sea bottom waters be either fresh, or very weakly brackish ( S  ≤ 1), between ∼50 and ∼10 Kyr BP. In addition, we find that the timing of the first deposition of the well-known Holocene sapropel corresponds to the time when salty bottom waters first reached the surface waters, and we speculate that increased organic matter production could have been caused by the release of nutrients stored in the saline bottom water. Finally, using current salinity proxy data, we find that the porewater salinity profiles generated from these proxies do not match the observed interstitial profiles.

The current saline state of the Black Sea is only the latest of a series of freshening‐salinization episodes that have affected that body of water during past glacial–interglacial cycles. Here, we model the salinity history of the basin and its sedimentary porewaters since the end of the penultimate saline period, variously thought to have occurred in the period between ∼128 and ∼65 Kyr BP. Our model results argue that the down‐core salinity profiles of Black Sea Holocene sediments have been affected by the diffusion of salt from the penultimate saline episode. Retrodiction of these porewater profiles also requires that the Black Sea bottom waters be either fresh, or very weakly brackish ( S ≤ 1), between ∼50 and ∼10 Kyr BP. In addition, we find that the timing of the first deposition of the well‐known Holocene sapropel corresponds to the time when salty bottom waters first reached the surface waters, and we speculate that increased organic matter production could have been caused by the release of nutrients stored in the saline bottom water. Finally, using current salinity proxy data, we find that the porewater salinity profiles generated from these proxies do not match the observed interstitial profiles.

The net freshwater balance plays a central role in the biological, chemical, geological and physical changes in the Black Sea since the Late Glacial Maximum (LGM), that is, 18–24,000 years BP. Past estimates of this balance vary widely. Here we solve inversely a water balance model coupled to two previously published Bosporus flow models, that is, flow rates controlled either by hydraulics with a critical height or by channel friction. We drive both models with two previously proposed Black Sea water‐level histories, that is, a smooth transition to saltwater entry and the “flood” scenario. First, we find that flow control by channel friction is far more likely than control by critical‐height hydraulics, as the latter does not allow Marmara Sea water to enter the Bosporus at any time in the past and predicts present‐day outflows that are far greater than observed. Prior to intense glacial melting (12–14,000 years BP), all models retrodict net freshwater inflow far less than previously assumed, that is, on the order of −1 to +10 km 3 yr −1 , rather than +100 s km 3 yr −1 . Thus, our results explain the ease by which the Black Sea could switch from evaporative to water gain conditions, as implied by water‐level records for that period. In addition, the channel friction model hindcasts glacial meltwater spikes during the transition from the LGM to the Holocene that are much smaller, that is, 100–250 km 3 yr −1 , than retrodicted by the hydraulic model or reported in the literature, that is, >1,000 km 3 yr −1 .

Hydrothermal chromium (Cr) cycling contributes to marine Cr inventories and their Cr isotopic composition, yet Cr isotope effects associated with this cycling remain poorly documented. Here we determine the distribution, isotopic composition, and diagenetic mobility of Cr in hydrothermal sediments from the distal flank of the South East Pacific Rise (SEPR, DSDP-site 598). We find that Cr is primarily associated with the metalliferous iron (oxyhydr) oxide and detrital components of the sediment (0.4–3.6 mg kg−1), whereas Cr concentrations are much lower in the dominant carbonate phase (<0.03mg kg−1). The Cr:Fe ratio of the metalliferous component, however, decreases with increasing depth below the sediment water interface, with an apparent loss of >80% Cr from the sediment relative to Fe. We propose this loss is tied to oxidation of authigenic Cr(III) to Cr(VI) followed by diagenetic remobilization and efflux from the sediment pile. The bulk δ53Cr composition of the SEPR sediments is isotopically light (−0.24 to −0.57 ± 0.05‰) and the authigenic δ53Cr is as light as −1.2 ± 0.2‰. We argue that this light Cr isotopic composition results from the partial reduction of oxic seawater-bearing Cr(VI) by hydrothermal vent fluids enriched in Fe(II)aq. Diagenetic oxidation of the reactive Cr pool by Mn-oxides and loss of Cr(VI) from the sediment may further deplete the sediment in 53Cr during diagenesis. The δ53Cr composition of the detrital Cr fraction of the sediment (average δ53Cr composition = −0.05 ± 0.04‰) falls within the igneous silicate earth (ISE) range, revealing that detrital Cr delivered to this region of the Pacific ocean is unfractionated, and has carried a relatively constant δ53Cr composition over the last 5.7 million years. Together our results show that light δ53Cr compositions in hydrothermal sediments are imparted through a combination of processes previously overlooked in the marine Cr biogeochemical cycle, and that the δ53Cr composition of such sediments may provide a rich source of information on paleo-marine redox conditions.

We present a high resolution sedimentary record of dinoflagellate cysts spanning the last similar to 900 years recovered from Effingham Inlet, a glacial fjord on the west coast of Vancouver Island, Canada. The combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters, together with restricted bottom water circulation in the silled fjord, fosters the preservation of laminated sediments in the inner basin of Effingham Inlet. Geochemical data are used to assess the sedimentary fades of the core, which is composed primarily of laminated units (50.2%) occasionally interrupted by "seismites" (39.5%) and homogenous units (102%). The chronology of the similar to 2 m-long core is based on varve counting and fifteen C-14 dates, and is anchored by a seismite previously dated at AD 1946.The dinoflagellate cyst assemblages are diverse (total of 47 taxa), abundant (average concentrations of 102,900 cyst g(-1) of dry sediment), and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples. Overall, cyst assemblages are characterized by Operculodinium centrocarpum (362%) accompanied by Brigantedinium spp. (18.0%) and Dubridinium spp. (6.6%). Multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately, and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary.Specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the "Medieval Climate Anomaly" (from the base of the record, similar to AD 1090 to 1230), the "Little Ice Age" (similar to AD 1230 to late 19th century) and warming in the second half of the 20th century. The timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of Vancouver Island. The origin of homogenous units in the sedimentary record of Effingham Inlet and paleoseismicity in the region are also discussed. (C) 2015 Elsevier B.V. All rights reserved.

The vertical flux of particles and their interactions within the ocean, together with the global ocean circulation, control the water-column distribution of a wide range of elements. Such processes condition patterns of their deposition and burial within marine sediments. Our understanding of these processes can be used to hindcast environmental conditions in the past from the sedimentary record. Here we report the major, minor and trace element compositions of a small sub-set of samples of sinking material collected at four depths (225, 410, 810, 1200m) in the Cariaco Basin (10.5° N, 64.67° W), which is anoxic below ~275m depth. We compare these data with the composition of the most recent basin floor sediment at the same location. The sediment trap samples examined represent material collected during both a high- and a low-productivity season, during a short-period flood event in coastal Venezuela, and immediately following an earthquake that induced a gravity flow. Our results show that the lithogenous composition of all four groups of trap samples and the basin floor sediment is uniform. This indicates that the source of siliciclastic detritus is largely from the local rivers draining the coastal region to the south of the Cariaco station. Enrichments of Ba relative to a model lithogenous background are found in the opal-rich high productivity samples from all depths; enrichments of Ag, Cd, Cu, Ni and Zn, directly associated with the flux of phytoplankton organic matter from the photic zone, are found not only in the high productivity samples, but also in the low productivity samples that have higher CaCO3 contents and lower organic matter and opal contents. In addition, modest particle and sediment enrichments of some redox-sensitive trace elements that are known to be removed from solution and sequestered in suboxic and anoxic sediments, namely Cr, V and Re are observed. However, barely detectable enrichments of U and Mo are present in all trap samples. In contrast with the trap sample compositions, the modern laminated basin-floor sediment exhibits significantly higher contents of Re, Mo and U than a solely lithogenous contribution, confirming studies that have found greater sub-sea floor fixation of these elements. Finally, the high settling flux of Ba observed in the high productivity trap samples is not preserved in the bottom sediment.

Sediment traps were deployed inside the anoxic inner basin of Effingham Inlet and at the oxygenated mouth of the inlet from May 1999 to September 2000 in a pilot study to determine the annual depositional cycle and impact of the 1999 La Niña event within a western Canadian inlet facing the open Pacific Ocean. Total mass flux, geochemical parameters (carbon, nitrogen, opal, major and minor element contents, and stable isotope ratios) and diatom assemblages were determined and compared with meteorological and oceanographic data. Deposition was seasonal, with coarser grained terrestrial components and benthic diatoms settling in the autumn and winter, coincident with the rainy season. Marine sedimentary components and abundant pelagic diatoms were coincident with coastal upwelling in the spring and summer. Despite the seasonal differences in deposition, the typical temperate-zone Thalassiosira–Skeletonema–Chaetoceros bloom succession was muted. A July 1999 total mass flux peak and an increase in biogenous components coincided with a rare bottom-water oxygen renewal event in the inlet. Likewise, there were cooler-than-average sea surface temperatures (SSTs) just outside the inlet, and unusually high abundances of a previously undescribed cool-water marine diatom (Fragilariopsis pacifica sp. nov.) within the inlet. Each of these occurrences likely reflects a response to the strong La Niña that followed the year after the strongest-ever recorded El Niño event of 1997–1998. By the autumn of 1999, SSTs had returned to average, and F. pacifica had all but disappeared from the remaining trap record, indicating that oceanographic conditions had returned to normal. Oxygenation events were not witnessed in the inlet in the years before or after 1999, suggesting that a rare oceanographic and climatic event was captured by this sediment trap time series. The data from this record can therefore be used as a benchmark for identifying anomalous environmental conditions on this coast.

Stagnant bottom-water conditions (e.g., low and stable redox potential, long-water residence time) is an assumption commonly used to explain the preservation and burial of high amounts of organic carbon (C-org) in marine sediments. Rather than stagnant conditions, the evidence presented here from north-central Tunisia supports dynamic conditions during formation of variably C-org-rich, outermost shelf carbonates of the early-middle Eocene. The dynamic conditions are inferred by the deposition of four distinct lithofacies in this outermost shelf setting. Shedding of carbonate (i.e., mud and fragmented bioclasts) from the shallower source areas controlled the distribution of all lithofacies, with higher amounts of transported benthic debris occurring in the most proximal lithofacies and vice versa. This carbonate shedding also controlled the deposition of three orders of lithological cycles, from limestone/marly limestone couplets grading to cycles made up of groups of couplets. Bottom-water redox potential varied in intensity throughout this depositional setting, with moderate oxygen depletion (suboxic conditions) in the southern sector of north-central Tunisia and much higher oxygenation in the northern area. Evidence for suboxic bottom waters in the southern sector (higher C-org contents) is provided by higher trace metal (Cu, Ni, Zn, Cr, Mo, U and V) enrichments than in the northern area. Regionally heterogeneous primary productivity of surface waters is suggested to have caused a higher C-org burial flux in the southern sector compared to the north, a situation interpreted to have been related to varying upwelling patterns due to the effects of regional palaeogeography and the dominant wind patterns.The deposition of the studied C-org-rich carbonates spanned part of the calcareous nannofossil Zones NP13 to NP14 (similar to 50-48 m.y. ago) and coincided with the initiation of the Cenozoic global cooling subsequent to the early Eocene climatic optimum (EECO) (similar to 52-50 m.y. ago). An implication is that an increased C-org burial in north-central Tunisia could have been part of a major event sequestering atmospheric CO2 in marine sediments that caused climatic cooling immediately after the EECO. This implication, however, is difficult to reconcile with the data available elsewhere. Other than our Tunisian carbonates, major C-org sequestration in marine sediments of the early-middle Eocene transition are poorly documented globally. If this scenario is confirmed, other negative feedbacks, such as enhanced continental weathering, increased terrestrial carbon stock, decreased CO2 outgassing and/or changes in ocean circulation, would have been more influential to the onset of the Cenozoic global cooling. (c) 2013 Elsevier B.V. All rights reserved.

Limnology and Oceanography BulletinVolume 22, Issue 1 p. 19-20 2013 ASLO AwardFree Access G. EVELYN HUTCHINSON AWARD: CURTIS SUTTLE Stephen Calvert, Stephen Calvert calvert@eos.ubc.ca Earth, Ocean & Atmospheric Sciences, University of British Columbia, CanadaSearch for more papers by this author Stephen Calvert, Stephen Calvert calvert@eos.ubc.ca Earth, Ocean & Atmospheric Sciences, University of British Columbia, CanadaSearch for more papers by this author First published: 18 December 2014 https://doi.org/10.1002/lob.201322119AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume22, Issue1February 2013Pages 19-20 RelatedInformation

In this study, we use records of nitrogen isotope ratios (delta N-15), UK'37 temperature estimates, organic carbon and opal percentages from high-resolution sediment cores located in the eastern equatorial Pacific (EEP) to explore the mechanisms linking millennial-scale changes in low-latitude sea surface temperature, water column denitrification and surface productivity to the timing of northern or southern polar climate during the last 100,000 yr. Our results support a hypothesis that the Southern Hemisphere, and its connection to the low latitudes via shallow subsurface ocean circulation, has a primary influence on the biogeochemistry of the EEP. In addition, our results suggest that, during the last glacial stage, denitrification rates fluctuated on millennial timescales in response to water-column ventilation rather than upstream oxidant demand in intermediate-depth waters.However, due to the poor age constraints available for Marine Isotopic Stage (MIS) 3, the EEP sedimentary data presented here could support two conflicting mechanisms, one driven by enhanced intermediate overturning circulation in the Southern Ocean during Heinrich Events/Antarctic Warm Events, implying that subsurface flow rates control thermocline ventilation, and a second one consistent with more sluggish intermediate circulation during Antarctic Warm Events and giving a central role to the temperature control on oxygen solubility in Southern Ocean surface waters. (C) 2010 Elsevier Ltd. All rights reserved.

The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20 kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by rivers entering the Black Sea from Eastern Europe. Alkali metal: Al and heavy: light rare-earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early Holocene lacustrine phase of the basin. The shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral-hosted trace elements Ti and Zr.The geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase, when high salinity Mediterranean water entered the basin beginning 9.3 kyrs BP. Bottom water that had been oxic throughout the lake phase became anoxic at approximately 8.4 kyrs BP, as recorded by the accumulation from the water column of several redox-sensitive trace metals (Mo, Re, U). The accumulation of organic carbon and several trace nutrients (Cd, Cu, Ni, Zn) increased sharply ca. 0.4 kyrs later, at 8.0 kyrs BP, reflecting an increase of primary productivity. Its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages. During this profound environmental change from the lacustrine to the marine phase, the accumulation rate of the lithogenous sediment fraction decreased as much as 10-fold in response to the rise of the water level in the basin from a low stand ca. 9.3 ka to its current level. Published by Elsevier Ltd.

The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number of studies of downcore opal records from the tropical Pacific. The original SALH predicts that unused silicic acid, due to Fe‐driven changes in Si versus N limitation, escaped from the glacial Southern Ocean to equatorial upwelling regimes where it enhanced diatom productivity, thereby decreasing coccolith growth and lowering atmospheric CO2. In contrast to SALH predictions, however, sedimentary records from the eastern equatorial Pacific (EEP) do not show enhanced opal burial during the Last Glacial Maximum (LGM) but higher rates of opal burial during the deglaciation and marine isotopic stage 3 (MIS3). The peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient‐rich waters driven by stronger upwelling of deep water in the Southern Ocean at the end of last glacial period. The large peak in opal burial observed in a number of EEP cores during MIS3 was interpreted as evidence for Si leakage when Southern Ocean diatom productivity was limited by both low dust flux and extended sea ice. On the other hand, the paradoxical LGM decline in opal accumulation in the EEP was explained by enhanced dust input that lowered the diatom Si:C uptake ratio. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to revisit opal burial in the EEP, in particular during the MIS3 “opal peak.” An increase in algal productivity is not supported by the sedimentary concentration of brassicasterol, an organic molecule commonly found in diatoms, or by the ratio of (231Pa/230Th)xs,0, a proxy for opal export production. We therefore conclude that the large peak in opal burial during MIS3 reflects enhanced preservation of diatoms. Building on mechanisms invoked in previous studies, we hypothesize that opal burial in the EEP is controlled both by the physiological response of diatoms to low‐latitude Fe inputs and by the high‐latitude processes leading to silicic acid leakage.

Sediments from Effingham Inlet, Vancouver Island, British Columbia hold a valuable high-resolution Holocene record of paleoclimatic and paleoceanographic conditions in the northeast Pacific Ocean. Accurate interpretation of this record requires that the depositional environment be well understood. In order to assess deposition within the fjord over the last 1500 years, two cores, a Soutar box core and a Kasten core, were analyzed for fossil diatoms, and biogeochemical properties. The cores contain varved sequences intercalated with homogeneous mud layers and a seismite. We show that homogeneous mud units related to periods of bottom water renewal are geochemically distinct from the seismite and that these bottom renewal events are favored when brackish rather than marine surface water conditions are present. The seismite, deposited in AD 1946, has lower opal and higher organic carbon concentrations and higher organic carbon: nitrogen ratios reflecting greater terrestrial material input. In contrast, homogeneous mud units are marked by a lower organic C/N and more isotopically heavy delta C-13 values, suggesting a stronger marine influence. Major metals and trace element data also confirm that the source material of these units differs from that of the AD 1946 seismite. Fossil diatom assemblages within the homogeneous mud units are characterized by a decreased abundance of typical marine spring bloom taxa (Skeletonema costatum, Chaetoceros spp., Thalassiosira spp.) coupled with an increased abundance of the brackish-water taxon Cyclotella choctawhatcheeana. Reduced surface salinity enhances stratification of the water column which, in turn, favors an intensified two-layer estuarine exchange across the shallow sills and associated bottom water renewal. The homogeneous mud units are produced through transport of sediment into the fjord coupled with a reworking of the upper layers of the sediment column. Therefore, these units represent a recorder of past changes in regional oceanography and climate. (C) 2009 Elsevier B.V. All rights reserved.

Deposition of marine black shales has commonly been interpreted as having involved a high level of marine phytoplankton production that promoted high settling rates of organic matter through the water column and high burial fluxes on the seafloor or anoxic (sulfidic) water-column conditions that led to high levels of preservation of deposited organic matter. or a combination of the two processes. Here we review the hydrography and the budgets of trace metals and phytoplankton nutrients in two modern marine basins that have permanently anoxic bottom waters. This information is then used to hindcast the hydrography and biogeochemical conditions of deposition of a black shale of Late Jurassic age (the Kimmeridge Clay Formation, Yorkshire, England) from its trace metal and organic carbon content. Comparison of the modern and Jurassic sediment compositions reveals that the rate of photic zone primary productivity in the Kimmeridge Sea, based on the accumulation rate of the marine fraction of Ni, was as high as 840 g organic carbon m(-2) yr(-1). This high level was possibly tied to the maximum rise of sea level during the Late Jurassic that flooded this and other continents sufficiently to allow major open-ocean boundary currents to penetrate into epeiric seas. Sites of intense upwelling of nutrient-enriched seawater would have been transferred from the continental margins. their present location, onto the continents. This global flooding event was likely responsible for deposition of organic matter-enriched sediments in other marine basins of this age, several of which today host major petroleum source rocks.Bottom-water redox conditions in the Kimmeridge Sea, deduced from the V:Mo ratio in the marine fraction of the Kinumeridge Clay Formation, varied from oxic to anoxic, but were predominantly suboxic, or denitrifying. A high settling flux of organic matter, a result of the high primary productivity, supported a high rate of bacterial respiration that led to the depletion of O-2 in the bottom water. A high rate of burial of labile organic matter, albeit a low percentage of primary productivity, in turn promoted anoxic conditions in the sediment pore waters that enhanced retention of trace metals deposited from the water column. Published by Elsevier B.V.

Determining climate variations over the Holocene requires high-resolution records with well-developed age models. A 40 m long marine sediment core raised from Effingham Inlet, an anoxic fjord on the west coast of Vancouver Island, British Columbia, Canada, yields such a record. Forty six14C accelerator mass spectrometry (AMS) dates determined from terrestrial plant material form the age model. Downcore sampling at both 5 cm (20 year) and 1.5 cm (7 year) resolution indicates that high-frequency oceanographic variability has prevailed at this site over the last 10 000 years. Spectral analysis of wt.% opal, a proxy for diatom productivity in the basin, reveals the bidecadal and pentadecadal periods of the Pacific decadal oscillation (PDO) – North Pacific index (NPI) that are related to changes in the strength of the Aleutian Low. Coherence analysis between the Effingham Inlet data and δ18O records from Jellybean Lake (a high elevation site in southwest Yukon) indicates regional coherence at periods of 45, 70, and 510 years between productivity in Effingham Inlet and changes in the Aleutian Low strength. Over the entire Holocene, the strength of decadal variability has changed. Both 20- and 50-year periods are present to some degree in the early Holocene, and only the 50 year period is evident in the late Holocene. These data imply that regime shifts would have been more frequent in the early Holocene relative to the last several thousand years.

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-la, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at similar to 12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core 6180 record and was completed by 10 700 BP, similar to 800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12-35 (x 10(4)) and 1-3.4 (x 10(4)), respectively, indicating that although large-amplitude, high-frequency fluctuations Occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years.

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-1a, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ∼12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ∼800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12–35 (×104) and 1–3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years.

The sedimentary record in a 40.9 m giant (Calypso) piston core (MD02-2494) raised from the inner basin within Effingham Inlet, British Columbia, Canada, during the 2002 Marges Ouest Nord Americaines (MONA) campaign, spans from 14 360 C-14 years BP (17 300 calibrated calendar (cal.) years BP) to about nine centuries before present. The core archives changes in sedimentation and sea level immediately following deglaciation of the Late Wisconsin Fraser Glaciation, which peaked about 15 000 C-14 years BP. The presence of the Mazama Ash in the core anchors a detailed chronology based on 49 radiocarbon dates and seven Pleistocene paleomagnetic secular variation correlations. Diatom assemblages identify a marine-freshwater-marine transition in the basin, which occurred 11630 C-14 years BP (13 500 cal. years BP). At this time, a bedrock sill, presently at 46 in depth, was briefly exposed as sea level fell and then rose again during isostatic crustal adjustments. These data constrain a new sea-level curve for the outer coast of Vancouver Island covering the past 12 000 C-14 years BP (14000 cal. years BP), providing new information on the nature of deglaciation along the west coast of Canada and informing interpretations of regional palcoceanographic records and mantle viscosity models.