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The present study gathers pioneering taxonomical and community data on testate amoebae and agglutinated tintinnids, analyzing their seasonal and spatial distribution patterns in the mesotidal system of the Guadiana Estuary, southeastern Portugal. To evaluate both groups’ potential as bioindicators in climate monitoring and paleoenvironmental reconstructions, their abundance, diversity and living proportions were compared to elevation in relation to mean sea-level, marine influence and to periods of elevated water levels. The distributions of testate amoebae and tintinnid total assemblages were also related to major physicochemical variables by means of multivariate analysis. From 49 surface sediment samples collected in winter and summer 2010, 17 species (25 strains) of testate amoebae were identified (in the 63 m fraction). The Centropyxidae, mainly represented by Centropyxis aculeata, Centropyxis arcula and Centropyxis constricta, had the greatest density (71% of total individuals), while the Difflugidae represented the most species (82% of total species). Higher diversities and densities were observed in winter in the upper estuary, where salinity is negligible, and in the middle estuary where they are concentrated at the lower levels of the intertidal zone. Few or no individuals were observed in the highest marsh zones. In winter, dead testate amoebae were dominant, with empty tests accumulating in the sediments from post-mortem transport by high river discharge. In summer, an increase in the living fraction is observed, with living testate amoebae along the entire estuary, which could indicate that some species are able to live in the lower reaches of the estuary. Along with the testate amoebae, two species of agglutinated tintinnids (>63 m), Stenosemella ventricosa and Tintinnopsis cf. lata, were abundant in the sediments. Their highest abundances were observed in summer. Living individuals were only recorded in summer, mainly in the vicinities of freshwater and sewage outflows, where elevated nutrient concentrations may be expected. The present study demonstrates that both testate amoebae and tintinnids have well defined patterns in their temporal and spatial distribution, offering high bioindicator potential in environmental/climate monitoring studies as well as in paleoenvironmental reconstructions. info:eu-repo/semantics/publishedVersion

The present study analyzes the spatial distribution and seasonal distribution of live benthic foraminiferal communities in the estuary of Guadiana, the fourth largest river on the Iberian Peninsula, and establishes, through statistical analysis, their relationships with a series of environmental parameters. Forty-four superficial sediment samples were collected along distance-to-sea and elevation gradients in the winter and summer of 2010. Fifty-three foraminifera species were identified along the intertidal margins of the estuary. Foraminiferal distribution reflected seasonal variation of environmental factors, whose relative importance varied according to species tolerances. Elevation in relation to mean sea level appeared to be the most important parameter controlling foraminiferal distribution, probably because it combines the effects of a series of other variables (i.e. organic matter, sediment texture, pH and temperature). In the highest marsh areas, where environmental conditions approach survival thresholds, only some agglutinated species are able to survive. In the lower intertidal zone, where subaerial exposure is diminished and environmental conditions are generally less variable, more diverse faunas, mainly composed of calcareous species, prevail. During winter, when fluvial discharge peaks, agglutinated species represent more than 80% of the total individuals. In summer, when marine conditions prevail, calcareous species become more competitive, increase their densities and expand into higher marsh zones and estuarine upper reaches. In the estuary, three different foraminiferal assemblages are distinguished: i) Miliammina fusca assemblage, which dominates in unvegetated areas of the lower marsh and tidal flats of the mid-upper estuary; ii)Jadammina macrescens assemblage, which dominates in the highest marsh areas in the lower estuary; and iii) Ammonia aberdoveyensis assemblage, which dominates the areas of low marsh and tidal flats of the lower estuary. (C) 2014 Elsevier B.V. All rights reserved. Portuguese Foundation for Science and Technology (FCT) [SFRH/BD/28265/2006] info:eu-repo/semantics/publishedVersion

Reinforced concrete is important for nuclear related structures. Therefore, the integrity of structural members consisting of reinforced concrete is germane to the safe operation and longevity of these facilities. Many issues that reduce the likelihood of safe operation and longevity are not visible on the surface of reinforced concrete material. Therefore, an investigation of reinforced concrete material should include techniques which will allow peering into the concrete member and determining its internal state. The performance of nondestructive evaluations is pursuant to this goal. Some of the categories of nondestructive evaluations are electrochemical, magnetism, ground penetrating radar, and ultrasonic testing. A specific ultrasonic testing technique, namely ultrasonic shear wave tomography, is used to determine presence and extent of voids, honeycombs, cracks perpendicular to the surface, and/or delamination. This technique, and others similar to it, has been utilized in the nuclear industry to determine structural conditions.

The recent report from Working Group II of the Intergovernmental Panel on Climate Change (IPCC) called for an increased understanding of how groundwater interacts with the ocean-atmospheric system. This remains a prerequisite to better understand how groundwater will respond to climate change. However, achieving this goal is hampered by several problems, including: (1) our minimal understanding of how current groundwater conditions evolved and responded to previous climatic perturbations, and (2) the scarcity of techniques available for evaluating prehistoric groundwater. Subfossil benthic foraminifera in underwater caves are an overlooked method of evaluating prehistoric groundwater on coastal carbonate terrain because they provide a proxy for groundwater salinity and circulation. Twelve radiocarbon dates and foraminiferal paleoecology from two sediment cores obtained from Green Bay Cave (GBC), Bermuda, provide the first Holocene-scale groundwater reconstruction. First, the cave floor (− 20.7 mbsl) was flooded at 7.7 ka as North Atlantic sea level and groundwater rose in near synchrony. Over the Holocene, groundwater conditions (salinity, circulation and degree of oxygenation) shifted a minimum of five times, primarily in response to sea-level rise. Most importantly, we provide evidence that a prehistoric meteoric lens collapsed at 1.6 ka as sea-level rise breached a local sill and completely altered Bermudian coastal circulation. The complete loss, or retreat, of a groundwater mass associated with a minor sea-level change validates some numerical predictions that small changes in sea level can destabilize coastal groundwater resources, when coastal geometry and circulation are considered.

Supersonic ejectors have been used in cooling/refrigeration applications since the early 1900s. Interest in supersonic ejectors has been rekindled by recent efforts to reduce energy consumption; ejector refrigeration systems can be powered by solar energy or by waste heat generated by another process. This paper describes an experimental test bench using R245fa that was assembled and operated at CanmetENERGY in Varennes. The results from this test bench provide a source of reference data that may be used to validate numerical models of ejectors that could be used in refrigeration applications. Limited results from two numerical models are presented for comparison; global results from a 1D model and results from a detailed CFD model that show the flow field inside the ejector.

Quaternary climate and sea-level research in coastal karst basins (caves, cenotes, sinkholes, blueholes, etc.) generally focuses on analyzing isotopes in speleothems, or associating cave elevations prior sea-level highstands. The sediments in coastal karst basins represent an overlooked source of climate and sea-level information in the coastal zone, but to accurately interpret these sediments first requires an understanding of the forcing mechanisms that emplace them. In this study, we hypothesize that coastal karst basins transition through vadose, littoral, anchialine, and finally into submarine environments during sea-level rise because groundwater and sea level oscillate in near synchrony in the coastal zone, causing each environment to deposit a unique sedimentary facies. To test this hypothesis, the stratigraphy in twelve sediment cores from a Bermudian underwater cave (Green Bay Cave) was investigated and temporally constrained with twenty radiocarbon dates. The results indicate that we recovered the first succession spanning the entire Holocene from an underwater cave (~ 13 ka to present). The sediments were characterized with X-radiography, fossil remains, bulk organic matter, organic geochemistry (δ13Corg, C:N), and grain size analysis. Four distinct facies represent the four depositional environments: (i) vadose facies (> 7.7 ka, calcite rafts lithofacies), (ii) littoral facies (7.7 to 7.3 ka: calcite rafts and mud lithofacies), (iii) anchialine facies (7.3 to 1.6 ka: slackwater and diamict lithofacies), and (iv) submarine facies (

Geological features supporting cold-water coral habitat in Atlantic Canada are reviewed and exemplified using qualitative field observations from the Scotian margin and Southwest Grand Banks, Newfoundland, in the context of regional geology of the Atlantic Canadian continental margin. Coral habitats are concentrated in areas of shelf-crossing troughs and trough-mouth fans associated with glacial ice streams. Most habitat types are supported by glacial or glaciomarine depositional features, although some are supported by erosional features, probably related to subglacial meltwater erosion. Shelf-break and upper continental slope moraine deposits, subject to strong currents, form current-swept cobble-boulder pavements, forming the principal habitats for the large gorgonian corals Primnoa resedaeformis and Paragorgia arborea . At greater depths, upper slope till tongues are upper continental slope gravelly mud deposits, exposed at the surface as isolated cobbles and boulders in a muddy sand matrix. Common skeletal corals in these environments include the large long-lived gorgonian Keratoisis ornata , the smaller gorgonian Acanthogorgia armata , and, in muddy sand between rocks, the small gorgonian Acanella arbuscula . Erosional environments including friable Tertiary mudstones and semi-consolidated Quaternary sediments, colonized by large gorgonians and other corals, were observed in The Gully, the Stone Fence, and the Southwest Grand Banks. Weak bedrock strength may limit the size of large gorgonian coral colonies. Authigenic carbonate crusts, possibly related to cold seeps, may be locally important in supporting coral growth. Predictive models of coral distribution should consider Quaternary and surficial geology.

The foraminifera from a Lower Cretaceous cored interval of Cohasset A-52 well (located on the Scotian Shelf) were used to interpret the depositional environments of these sediments. Paleoenvironmental interpretation was based on the analysis on 41 samples from four cored intervals of the well collected between 2069 and 2219 m below seafloor. The interval consists of 25 m of interbedded gray-black shale, mudstone and sandstone belonging to the Cree Member of the Logan Canyon Formation. The foraminiferal association recorded in the studied samples is comprised mainly of agglutinated specimens of Trochammina, Haplophragmoides, Ammobaculites and Verneuilinoides . A scattered occurrence of calcareous benthic foraminifera and thecamoebians is also recorded. A comparison of these microfauna with modern foraminiferal associations from paralic environments suggests that these sediments were deposited in a Cretaceous marsh–estuarine environment.

Two hypotheses have been proposed to explain the origin of marine isotope stage (MIS) 11 deposits in small Bermudian caves at +21 m above modern sea level: (1) a +21 m MIS 11 eustatic sea-level highstand, and (2) a MIS 11 mega-tsunami event. Importantly, the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments. After statistically comparing foraminifera in modern Bermudian littoral caves and the MIS 11 Calonectris Pocket A (+21 m cave) to the largest available database of Bermudian coastal foraminifera, the assemblages found in modern littoral caves – and Calonectris Pocket A – cannot be statistically differentiated from lagoons. This observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone, where typical coastal processes (waves, storms) homogenize and rework lagoonal, reefal, and occasional planktic taxa. Fossil protoconchs of the Bermudian cave stygobite Caecum caverna were also associated with the foraminifera. These results indicate that the MIS 11 Bermudian caves are fossil littoral caves (breached flank margin caves), where the total MIS 11 microfossil assemblage is preserving a signature of coeval sea level at +21 m. Brackish foraminifera (Polysaccammina, Pseudothurammina) and anchialine gastropods (∼95%, >300 individuals) indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase. The onset of sea-level regression following the +21 m highstand would first lower the ancient brackish Ghyben-Herzberg lens (

This paper presents new data on distribution patterns of modern benthic foraminifera and other microfossils from the Canadian Arctic, specifically the Beaufort Shelf and slope. The material was collected in June to August of 2004 and is the first of its kind in this area to be collected since 1970. We examined the smaller sizes (45–63µm) as well as N 63µm and discovered that many species had been severely underrepresented in previous studies. Deep sea forms, that had been overlooked previously, were common on the shelf; two species (Elphidiella arctica and Ammotium cassis) appeared in preliminary results to be indicators of methane seepage; and it was possible to make determinations of sea-ice coverage using a combination of foraminifera and tintinnids (planktic ciliates). Our data indicated the presence of many of the same species as previous studies from this area, but improved techniques of sample processing greatly increased the number of specimens and species found (particularly the small deep sea arctic species Buliminella hensoni and Bolivina arctica) which provide much more reliable data for paleoceanographic determinations. One of the primary objectives for this work was to provide baseline data to help determine paleo-ice cover; these data cover a broad range of conditions on the Beaufort Shelf that make it possible to achieve this objective as well as improving

Deep-sea gorgonian corals secrete a 2-part skeleton of calcite, derived from dissolved inorganic carbon at depth, and gorgonin, derived from recently fixed and exported particulate organic matter. Radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters, respectively. Using specimens collected from Northwest Atlantic slope waters, we generated radiocarbon records for surface and upper intermediate water layers spanning the pre- and post-bomb- 14 C eras. In Labrador Slope Water (LSW), convective mixing homogenizes the pre-bomb Δ 14 C signature (− 67 ± 4‰) to at least 1000 m depth. Surface water bomb- 14 C signals were lagged and damped (peaking at ∼ + 45‰ in the early 1980s) relative to other regions of the Northwest Atlantic, and intermediate water signals were damped further. Off southwest Nova Scotia, the vertical gradient in Δ 14 C is much stronger. In surface water, pre-bomb Δ 14 C averaged − 75 ± 5‰. At 250–475 m depth, pre-bomb Δ 14 C oscillated quasi-decadally between − 80 and − 100‰, likely reflecting interannual variability in the presence of Labrador Slope Water vs. Warm Slope Water (WSW). Finally, subfossil corals reveal no systematic changes in vertical Δ 14 C gradients over the last 1200 yr.

Primnoa resedaeformis is a deep-sea gorgonian coral with a two-part skeleton of calcite and gorgonin (a fibrillar protein), potentially containing long-term records of valuable paleo-environmental information. For various reasons, both radiocarbon and U/Th dating of these corals is problematic over the last few centuries. This paper explores aspartic acid racemization dating of the gorgonin fraction in modern and fossil specimens collected from the NW Atlantic Ocean. Radiocarbon dating of the fossil specimen indicates a lifespan of 700 ± 100 years, the longest yet documented for any octocoral. Gorgonin amino acid compositions were identical in the fossil and modern specimens, indicating resistance to organic diagenesis. Similar to bone collagen, the fibrillar protein of gorgonin may impose conformational constraints on the racemization of Asp at low temperatures. The rate of racemization of aspartic acid ( d / l -Asp) was similar to previously published results from an 1800 year old anemone (Gerardia). The age equation was: age (years BP 2000 AD) = [( d / l − 0.020 (±.002))/.0011 (±.0001)]2 (r2 = 0.97, p d / l -Asp was marginally better than that for 14C dating over the most recent 50–200 years, although the dating error may be improved by inclusion of more samples over a broader time range. These results suggest that d / l -Asp dating may be useful in augmenting 14C dating in cases where 14C calibrations yield two or more intercept ages, or in screening samples for further 14C or U/Th dating.

A high-resolution record of sea-level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt-marsh peat sequence at Chezzetcook, Nova Scotia, Canada. Former mean tide level positions are reconstructed with a precision of ±0.055 m using a transfer function derived from distributions of modern salt-marsh foraminifera. Our age model for the core section older than 300 years is based on 19 AMS 14C ages and takes into account the individual probability distributions of calibrated radiocarbon ages. The past 300 years is dated by pollen and the isotopes 206Pb, 207Pb, 210Pb, 137Cs and 241Am. Between AD 1000 and AD 1800, relative sea level rose at a mean rate of 17 cm per century. Apparent pre-industrial rises of sea level dated at AD 1500-1550 and AD 1700-1800 cannot be clearly distinguished when radiocarbon age errors are taken into account. Furthermore, they may be an artefact of fluctuations in atmospheric 14C production. In the 19th century sea level rose at a mean rate of 1.6 mm/yr. Between AD 1900 and AD 1920, sea-level rise accelerated to the modern mean rate of 3.2 mm/yr. This acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming. © 2005 Elsevier Ltd. All rights reserved.

Diatom, pollen, foraminifera and thecamoebian assemblages from an outcrop of peat and silt at Girdwood Flats, in the upper Turnagain Arm of the Cook Inlet, Alaska, record four phases of relative land and sea-level changes. The first phase is the development of freshwater swamp above high marsh sediments during relative land uplift, caused by strain accumulation along the locked portion of the Alaska-Aleutian subduction zone. In second phase, the top 2 cm of the peat, all microfossil groups record pre-seismic relative sea-level rise (relative land subsidence). The third phase is rapid land subsidence, 1.7 m, during the earthquake of March 1964 that initiated intertidal silt accumulation above the peat. The final phase is the colonisation of mudflat by salt marsh communities during post-seismic land uplift. The microfossil data compare favourably with sequences from Washington, Oregon and British Columbia that record late Holocene submergence events caused by earthquakes. The comparable changes in microfossil assemblages record the different phases of relative land and sea-level changes and the magnitude of land subsidence caused by each earthquake (expressed relative to the tidal range at the site). These results raise the question whether preseismic sea-level rise represents any kind of warning of large earthquakes.

More than 40 short cores were collected from 10 localities in the Myrtle Beach to McClellandville coastline of South Carolina. The localities were selected on the basis of whether or not they should have a well preserved record of recent hurricanes, most notably Hugo , which occurred in September, 1989. Of the 40 cores collected, results from two sites are presented here as examples — Price’s Inlet, a non-tidal intra-beach ridge area, which was directly in the path of the eyewall of Hugo , and Sandpiper Pond which is a coastal non-tidal pond near Murrells Inlet, about 50–75 km north of where the main landfall of hurricane Hugo but still in the area of high storm surge. These cores were analyzed for percentage organic carbon, visual observations, X-rays, and microfossils. The microfossils were used to differentiate marine/non-marine sequences in the non-tidal inlets and identify reworked sediments by means of displaced benthic foraminifera. Cores were dated using Pb-210 techniques that provide resolution for the last 100 yr. In Price’s Inlet the Hugo effect was most pronounced with an 8 cm thick sand layer containing many nearshore foraminifera, showing transport from offshore. In Sandpiper Pond we could see the trace of Hugo from the offshore foraminifera contained in sediments sandwiched between the freshwater intervals both before and after Hugo , however, there was little detectable trace in the X-rays or sedimentology of this core to indicate a storm event. Hence, we can recognize a range of responses for hurricanes in the form of different types of sediment layers and microfossil assemblages in these non-tidal areas depending on where the impact point is on the coast. Here we are able to distinguish at least two types of signals from the same storm which has significant implications for detecting these events in the pre-historic record and determining their paleo-periodicity.

The Messinian was a time of major climatic and paleoceanographic change during the late Cenozoic. It is well known around the Mediterranean region because of the giant anhydrite/gypsum sequence and the suggested desiccation of the Mediterranean Sea. However, this interval is less constrained outside the Mediterranean region, where several paleoceanographic changes could have taken place because of the desiccation. Hence, we present an integrated stratigraphic framework for future Messinian paleoceanographic studies, determination of the effect of the Mediterranean desiccation on deep-water paleoceanography, and comparison of intra-Mediterranean paleoceanographic changes with those in the open oceans during the Messinian Stage. Four DSDP/ODP Holes (552A, 646B, 608, and 547A) from the North Atlantic Ocean and one land borehole from Morocco have been studied to integrate bio-, magneto-, and stable isotope Messinian stratigraphy with high resolution sampling. Our results produce the best assessment of the Tortonian/Messinian boundaries in all holes because they do not rely on any one signal. In paleomagnetic Subchronozone CSAn.lr in the Sale borehole and DSDP Site 609, a S/D coiling direction change of Neogloboquadrina pachyderma/acostaensis appears to indicate PMOW entering the northeastern Atlantic Ocean, at least reaching 50°N. Diachrony and synchrony of some important Messinian planktic foraminifera from these Atlantic DSDP/ODP holes and the Sale borehole, such as the LO of Gq. dehiscens, the LO of Gt. lenguaensis, the FO and LO of Gt. conomiozea, the FO of Gt. margaritae s.s., the FO of Gt. puncticulata, and the FO of Gt. crassaformis are discussed for understanding some of the paleoceanographic changes. This integrated stratigraphie framework presented here allows much better North Atlantic correlations at this critical point in Messinian geologic history.

Sea level oscillated between 5500 and 3500 years ago at Murrells Inlet, South Carolina, Chezzetcook and Baie Verte, Nova Scotia and Montmagny, Quebec. The oscillation is well constrained by foraminiferal marsh zonations in three locations and by diatoms in the fourth one. The implications are: (1) there was a eustatic sea-level oscillation of about 2–10 m in the late mid-Holocene on the southeast coast of North America (South Carolina to Quebec) that is not predicted by present geophysical models of relative sea-level change; (2) this oscillation coincides with oceanographic cooling on the east coast of Canada that we associate with melting ice; and (3) this sea- level oscillation/climatic event coincides exactly with the end of pyramid building in Egypt which is suggested to have resulted from a climate change (i.e. drought, cooling). This sea-level/climatic change is a prime example of feedback where climatic warming in the mid-Holocene promoted ice melt in the Arctic which subsequently caused climatic cooling by opening up Arctic channels releasing cold water into the Inner Labrador Current that continued to intensify until 4000 years ago. This sea-level event may also be the best way of measuring when the final ice melted since most estimates of the ages of the last melting are based on end moraine dates in the Arctic which may not coincide with when the last ice actually melted out, since there is no way of dating the final ice positions.

Nova Scotia's position near the margin of large Pleistocene ice sheets makes the Scotian Shelf region critical for evaluation of glaciation models and sea-level change. The sea floor of the inner Scotian Shelf was mapped using multibeam bathymetry, a combination of conventional seismic and sonar techniques, and sampling. Multibeam bathymetry provides an areal image of the sea floor. Combining this unique image with sub-bottom seismic imaging, the relationships between sea floor topography and the underlying strata were explored. The inner continental shelf of Nova Scotia can be subdivided into five major terrain “zones”. These are the: (1) Truncation Zone, (2) Morainal Zone, (3) Outcrop Zone, (4) Basin Zone and (5) Scotian Shelf End-Moraine Complex. The Scotian Shelf End-Moraine Complex and Basin Zone are glacial-depositional zones at the seaward edge of the inner shelf. Landward of these zones is a region of high relief bedrock, with ridges and valleys largely devoid of surficial sediments extending from 80 to 120 m water depth (Outcrop Zone). This zone is interpreted as a relict bedrock surface, preserved under frozen-bed glacier conditions. To the east of the Outcrop Zone, in similar water depths, are unmodified till ridges overlying bedrock (Morainal Zone). The Truncation Zone is a region of the inner shelf from −90 m to the present shoreline characterized by muted acoustic topography and planar erosional surfaces truncating bedrock and surficial sediments. The Truncation Zone is subdivided into the Valley Subzone, the Transition Subzone, the Platform Subzone and the Estuarine Subzone. The Valley Subzone is typified by sediment-infilled valleys occurring in 75 to 90 m water depths. These valleys contain seismic facies with a ponded style of deposition planed off at the sea floor or by erosional unconformities near the sea floor. The Transition Subzone is marked by a relatively steep “ramp” and terraces. The ramp at the type section extends from 75 to 65 m water depth. The surface of the ramp can be either an erosional unconformity or a depositional surface formed by clinoform beds. The −65 m former shoreline is interpreted as the top of the Transition Subzone ramp surface. At one ramp locality, clinoform beds form part of a progradational sequence called the Sambro Delta. A mussel valve fragment ( Mytilus edulis ) was obtained from a core in the foresets and radiocarbon dated. An age of 11,650 ± 110 yr B.P. was obtained, adjusted for isotopic fractionation. Above −65 m the sea floor forms a low relief, gently sloping erosional surface (Platform Subzone). Estuarine deposits have been found above −50 m. The new sea-level curve constructed with the dated −65 m shoreline and recently published data is at variance with calculated RSL curves based on geophysical models, primarily in the amplitudes and rates of RSL change. Reasons for the discrepancies may be late-melting ice and regional variations in lithospheric strength and thickness.

Agglutinated foraminifera and arcellaceans (“thecamoebians”) were examined from Carboniferous (late Westphalian-Stephanian) cyclothems in the Sydney Basin of Nova Scotia. Four distinctive assemblages are documented from the coal-bearing strata, and indicate deposition took place on an extensive coastal platform. The eastern part of the basin is dominated by Ammobaculites-Ammotium assemblages that indicate estuarine-low marsh paleoenvironments. Relationships between test size, grain size within the test, and grain size of the substrate are used to differentiate between upper mudflat and lower mudflat sub-facies within estuarine facies. Mixed assemblages dominated by Trochammina, Ammotium and Ammobaculites indicate vegetated substrates, analogous to modern lower marsh environments, and flanked the estuarine system in the eastern and western areas of the basin. Rich Trochammina and thecamoebian assemblages are restricted to the western area of the basin, indicating deposition within the upper part of the tidal range. Trochammina assemblages, typically found underlying coal seams, may indicate vegetated substrates equivalent to modern high marsh facies. Thecamoebian assemblages, dominated by an agglutinated difflugid type, indicate freshwater paleoenvironments. Encystment of the thecamoebian populations suggests paleoenvironments were short lived.

Reworked Tertiary-Cretaceous (T-K) foraminifera occur in a well-defined Pleistocene sequence on the Scotian Shelf. Although T-K rocks are still outcropping here, virtually no T-K foraminifera are found in Holocene sediments. Significant occurrences of these forms have been recorded in glacial sediments and their presence increases deeper into the glacial-marine sequence. The down-section increase in T-K abundance is systematic and suggests that changing abundances of T-K forms may be an index to the amount of erosive glacial activity taking place at the former ice margin shoreward of this location. The abundance of these forms may indirectly provide some chronological control on isolated silt-clay samples that have been recovered recently by offshore drilling.

A number of thecamoebian genera of potential or demonstrated importance for palaeolimnological research (mainly Arcellacea) are discussed. What is known about their biology, ecology, spatial distribution, mechanisms of dispersal and characteristic associations is briefly reviewed in the introductory part. After a short discussion on the concept of species and the somewhat peculiar way in which it applies to this group of organisms, a chapter on systematic taxonomy, including an illustrated guide to the identification of the genera, is presented. The scarce fossil record of the group is then briefly discussed. Practical instructions on collection, preparation and observation of thecamoebians for palaeolimnological research are supplied. The paper closes with the presentation of a few studies performed by the authors as examples of how Arcellacea can become tools for the solution of palaeolimnological problems.

Micropaleontological studies were made of cores from four shelf basins on the eastern Canadian Margin: Emerald and Canso basins on the Scotian Shelf (44°–46° N), Notre Dame Channel, Newfoundland Shelf (50° N) and Cartwright Saddle, Labrador Shelf (55°). Events were correlated using a combination of14C dates and pollen stratigraphies. Surface- and bottom-water changes were compared on the basis of dinoflagellates and benthic foraminifera, respectively. The results indicate significant paleoceanographic shifts along a north—south gradient both prior to and during the Holocene. Distinct Late Pleistocene—Holocene paleoceanographic events were distinguished in the Emerald, Canso and Notre Dame basins; these events are less obvious in Cartwright Saddle which is in deeper water and further off-shore. Pleistocene glaciomarine sediments in all basins contain a fauna dominated byElphidium excavatum f.clavata; dinoflagellates and pollen are rare or absent. The widespreadElphidium fauna probably reflects turbid glacial meltwater and/or a permanent ice shelf cover from 20,000-10,000 yrs BP. The Notre Dame core also penetrates older sediment with an outer Labrador Current fauna which may represent a late Wisconsinian interstade at about 23,000 yrs BP. From 7,000–10,000 yrs BP a cold water fauna occurred which is similar to modern outer Labrador Current faunas. From about 5000–7000 yrs BP, a warm interval is indicated by a relatively warm-water calcareous benthonic foraminiferal fauna and increased representation of typical Gulf Stream dinoflagellates. The most recent change occurred in the last 2000 years with an abrupt cooling associated with stronger flow of the arctic inner Labrador Current. This cooling event is marked by an increase in arctic dinoflagellates and by an exclusively agglutinated benthonic foraminiferal fauna at two sites (Canso and Notre Dame). These Holocene paleoceanographic changes are not clearly seen in the benthic fauna of the deep northern basin (Cartwright Saddle) although dinoflagellate data at this site indicate that surface-water changes have occurred that are similar to those found in shallower basins. Shifts in the zonal position of the Gulf Stream and changes in the relative mass transports of the West Greenland and Labrador currents are mechanisms which may account for the paleoceanographic events. The glacial—interstadial—glacial sequence recorded in the Notre Dame Channel, in conjunction with other theories on glacial triggering mechanisms, provides biostratigraphic evidence which suggests the onset of a glacial stage in the near future.

Earlier studies of this area show profound Holocene-Pleistocene paleoceanographic changes along the eastern continental margin of Canada, based on benthic foraminiferal assemblages. Here we demonstrate that stable isotopic measurements from benthonic foraminifera substantiate and place numerical limits on physical parameters from some of the glacial/postglacial environments. In Holocene intervals, where modern analogues of present-day benthonic foraminiferal faunas can be used to delimit the physical environment, the isotopic results closely parallel the faunal results. In the glacial-marine intervals, where we have no modern analogues, the isotopic results provide us with the first independent evidence that the salinities were not lower than 30% in the bottom waters along this former ice margin. At the time of peak glaciation, salinities may actually have been above normal. We see no indication of a large meltwater event in the 10–11 k.y. B.P. time period that has been suggested to occur with the younger Dryas events. These results demonstrate that stable isotopes can be useful outside the context of relatively stable, deep-sea environments.

1. 1. The calcareous corpuscles of Cysticercus cellulosae , larval Spirometra mansonoides , Taenia saginata , and Diphyllobothrium latum contain various proportions of calcium, magnesium, phosphorus, and CO 2 as major components. 2. 2. The corpuscles of these worms, and those of the previously studied Taenia taeniaeformis , contain in addition several minor inorganic constituents. The corpuscles of the larval worms show a smaller variety of the minor components than those of the adult worms. 3. 3. The crystallization patterns induced by heat or KOH treatment vary, especially in respect to the phosphorus-containing compounds. Three of the latter have been identified: Hydroxyapatite, whitlockite, and calcium-magnesium-orthophosphate. The crystallization variations may be related to the ratios in which the major components occur in the corpuscles of the different species.

The applications of the electron microscope in the study of dental tissues have been described. Some of the results of the investigations of the structure of mature and developing enamel and dentine, and various other tissues, have been presented.

Techniques have been described by which thin sections for electron microscopy can be prepared from both undemineralized and artificially demineralized specimens of carious enamel and dentine. Observations on the typical appearance of these tissues have been reported and illustrated with representative electron micrographs. The relation of the findings to present concepts on the histopathology of dental caries has been discussed.

Excellent contrast revealing detail within and between cells can be obtained in X-ray microradiographs of standard 6 μ sections of soft tissues when a magnesium target is used and photographs are made in vacuum.