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An annually laminated succession in Crawford Lake, Ontario, Canada is proposed for the Global boundary Stratotype Section and Point (GSSP) to define the Anthropocene as a series/epoch with a base dated at 1950 CE. Varve couplets of organic matter capped by calcite precipitated each summer in alkaline surface waters reflect environmental change at global to local scales. Spheroidal carbonaceous particles and nitrogen isotopes record an increase in fossil fuel combustion in the early 1950s, coinciding with early fallout from nuclear and thermonuclear testing – 239+240Pu and 14C:12C, the latter more than compensating for the effects of old carbon in this dolomitic basin. Rapid industrial expansion in the North American Great Lakes region led to enhanced leaching of terrigenous elements by acid precipitation during the Great Acceleration, and calcite precipitation was reduced, producing thin calcite laminae around the GSSP that is marked by a sharp decline in elm pollen (Dutch Elm disease). The lack of bioturbation in well-oxygenated bottom waters, supported by the absence of fossil pigments from obligately anaerobic purple sulfur bacteria, is attributed to elevated salinities and high alkalinity below the chemocline. This aerobic depositional environment, highly unusual in a meromictic lake, inhibits the mobilization of Pu, the proposed primary stratigraphic guide for the Anthropocene.

Varved sediments in meromictic Crawford Lake consist of dark-light couplets of organic matter (primarily phytoplankton and amorphous organic matter) capped by calcite crystals. The crystals precipitate in the alkaline epilimnion between spring and fall turnover, consistent with Langelier Saturation Index calculations that predict calcite precipitation when pH and temperature exceed 7.76 and ~ 15°C respectively. Climate, primary production, and acid precipitation control lamina thickness: acid precipitation primarily affects the precipitation and accumulation of calcite crystals, whereas both endogenic calcite and authigenic organic matter are affected by climate and primary production. Thin varves, often with barely perceptible light-coloured calcite lamina were deposited between the late 1940s and mid-1970s, when air and water quality were impacted by rapid industrialization. Conditions required for precipitation of calcite laminae were absent during the 16th to mid-19th centuries, an interval corresponding to the Little Ice Age when no human impact occurred in the catchment. Varves dating from 1867 CE onwards (the Canadian Zone) facilitate the candidacy of the deep basin sediments of Crawford Lake to define the Anthropocene epoch.

Lechaion's inner harbour basin was constructed in the 7th-6th c. BCE and served as Corinth's principal port for over a millennium. The harbour decline and abandonment in the 6th c. CE has been attributed to several causes: natural siltation, co-seismic uplift, coastal subsidence, and damage by tsunami impacts. A multi-proxy palaeoenvironmental study was conducted on seven cores from Lechaion's inner harbour to determine changes in the coastal environments and timing and cause of harbour abandonment. Palaeoenvironments were reconstructed using high-resolution micro-XRF core scanning of sedimentary facies, isotopic (δ18O, δ13C), and micropalaeontological analyses (foraminifera, palynomorphs). The harbour lithostratigraphy consists of an uppermost (∼1 m) sequence of laminated mud and marl overlying interbedded pebbly sand and mud containing abundant marine microfossils and Roman pottery refuse. A thin (

Coarse root biomass was estimated in a temperate pine forest using high-resolution (1-GHz) 3-D ground-penetrating radar (GPR). GPR survey grids were acquired across a 400-m2 area with varying line spacing (12.5 and 25 cm). Root volume and biomass were estimated directly from the 3-D radar volume using isometric surfaces calculated with the marching cubes algorithm. Empirical relations between GPR reflection amplitude and root diameter were determined for 14 root segments (0.1-10 cm diameter) reburied in a 6-m2 experimental test plot and surveyed at 5-25 cm line spacing under dry and wet soil conditions. Reburied roots >1.4 cm diameter were detectable as continuous root structures with 5 cm line separation. Reflection amplitudes were strongly controlled by soil moisture and decreased by ~40% with a two-fold increase in soil moisture. GPR line intervals of 12.5 and 25 cm produced discontinuous mapping of roots and GPR coarse root biomass estimates (0.92 kgCm-2) were lower than those obtained previously with a site-specific allometric equation due to non-detection of vertical roots and roots

Offshore sedimentary deposits preserved in submarine canyons in southern Calabria, Italy, provide evidence for mid-Holocene (ca. 6000 BP) erosion and the transport of organic-rich floodplain sediments by flash-flood (hyperpycnal) flows from the San Pasquale River. Marine geophysical surveys (bathymetry, side-scan sonar) and diver reconnaissance revealed an unusual offshore peat deposit containing plant macrofossils representing local habitats, potentially reflecting human modified landscapes. The 20–30 cm thick organic deposit included a large tree trunk, well-preserved seeds, leaves, sticks and other delicate organics. Textural and microfossil (foraminifera) analysis of associated sediments (sands and muds) indicate that these deposits resulted from hyperpycnal flood events that were deposited as sediment gravity flows within gullies on the canyon margins. Whilst the value of studying in situ submerged prehistoric landscapes is well documented, we demonstrate that reworked floodplain deposits preserved in offshore environments can provide useful palaeoenvironmental information that may not be preserved in terrestrial settings. The botanic archive preserved in submarine flood deposits at San Pasquale affords a unique insight into the local environment in which people lived during the Final Neolithic.

Central Canada experiences numerous intraplate earthquakes but their recurrence and source areas remain obscure due to shortness of the instrumental and historic records. Unconsolidated fine-grained sediments in lake basins are ‘natural seismographs’ with the potential to record ancient earthquakes during the last 10,000 years since the retreat of the Laurentide Ice Sheet. Many lake basins are cut into bedrock and are structurally-controlled by the same Precambrian basement structures (shear zones, terrane boundaries and other lineaments) implicated as the source of ongoing mid-plate earthquake activity. A regional seismic sub-bottom profiling of lakes Gull, Muskoka, Joseph, Rousseau, Ontario, Wanapitei, Fairbanks, Vermilion, Nipissing, Georgian Bay, Mazinaw, Simcoe, Timiskaming, Kipawa, Parry Sound and Lake of Bays, encompassing a total of more than 2000 kilometres of high-resolution track line data supplemented by multibeam and sidescan sonar survey records show a consistent sub-bottom stratigraphy of relatively-thick lowermost lateglacial facies composed of interbedded semi-transparent mass flow facies (debrites, slumps) and rhythmically-laminated silty-clays. Mass flows together with cratered (‘kettled’) lake floors and associated deformations reflect a dynamic ice-contact glaciolacustrine environment. Exceptionally thick mass flow successions in Lake Timiskaming along the floor of the Timiskaming Graben within the seismically-active Western Quebec Seismic Zone (WQSZ), point to a higher frequency of earthquakes and slope failure during deglaciation and rapid glacio-isostatic rebound though faulting continues into the postglacial. Lateglacial faulting, diapiric deformation and slumping of coeval lateglacial sediments is observed in Parry Sound, Lake Muskoka and Lake Joseph, which are all located above prominent Precambrian terrane boundaries. Lateglacial sediments are sharply overlain by relatively-thin rhythmically-laminated and often semi-transparent postglacial silty-clay laminations. Postglacial neotectonic activity is recorded by co-seismic water-escape structures, faults, slumps and debris flows in Lake Simcoe (above a terrane boundary) and especially within lakes Timiskaming and Kipawa, recording ongoing deformation within the WQSZ. High resolution seismo-stratigraphic data presented here support the model that ongoing mid-plate earthquake activity is a consequence of brittle deformation of the upper crust of the North American plate. Such activity appears to have been greatest during deglaciation but continues today.

Understanding the processes that deposit till below modern glaciers provides fundamental information for interpreting ancient subglacial deposits. A process-deposit-landform model is developed for the till bed of Saskatchewan Glacier in the Canadian Rocky Mountains. The glacier is predominantly hard bedded in its upper reaches and flows through a deep valley carved into resistant Palaeozoic carbonates but the ice margin rests on a thick (

The arrival of Paleoindian peoples in the lower Great Lakes (ca 11.5 ka cal. BP) coincided with a phase of lowstand lakes and rapid environmental change in southern Ontario. At Rice Lake, an archaeologically-rich area north of Lake Ontario, rising Early Holocene water levels inundated wetland areas exploited by Paleoindian and Archaic peoples. In order to better understand the distribution of submerged archaeological sites and the water level history of Rice Lake, a detailed multi-proxy study was conducted on two vibracores extracted from the open lake and a shallow ( The basin stratigraphy consisted of Holocene organic-rich muds (gyttja), laminated marls, and peats overlying glacial Lake Iroquois sands and clay deposits. Two erosional hiatuses indicating lowstand phases (EH-1 ca 12.5–11 ka cal. BP EH-2 ca 6–3 ka cal. BP) were identified by rapid shifts in particle size and thecamoebian abundance and assemblages. The dominant thecamoebian species in the open lake basin were Arcella vulgaris and Centropyxis constricta ‘aerophila’, indicating the trophic status of the lake has remained stable throughout the Holocene. In the McIntyre lagoon, the EH-1 lowstand was associated with a unique bog and wetland species ( Bullinularia and Phryganella sp.) along with the recovery of microdebitage, indicating that Paleoindian peoples were likely exploiting wetland resources such as plants, fish and waterfowl. We show that the study of lacustrine paleoenvironments using a multi-proxy approach provides additional information for identifying areas of archaeological potential and gaining additional understanding of settlement patterns and resource procurement strategies of Paleoindian and Archaic peoples in Southern Ontario.

Rice Lake, located in the eastern Great Lakes of North America, has a high density of prehistoric (11–0.5 ka BP) terrestrial archaeological sites. It has been speculated that a large number of sites are submerged on the lakebed, as lake levels have risen >9 m since the arrival of Early Paleoindian peoples (∼11 ka BP). In order to better understand the submerged landscape and its archaeological potential, a detailed bathymetric survey and sediment-coring program was conducted across a 30-km 2 area of northeastern Rice Lake. Changes in Holocene water levels and shoreline positions were reconstructed by integrating core data with a digital elevation and bathymetric model (DEBM) that accounted for differential isostatic uplift and basin sedimentation. The DEBM was used to generate a series of maps showing changes in the lake paleobathmetry and paleogeography and areas of prehistoric archaeological potential. Isostatic uplift of the eastern basin outlet (>30 m) had a dramatic influence on water levels and shoreline positions since the inception of Rice Lake (∼12 ka BP). During the Early Paleoindian occupation phase (∼11–10.5 ka BP), water levels were at a maximum lowstand (10 m bpl) and much of the present lakebed was an exposed lake plain with extensive wetlands. At the time of the Late Paleoindian/Early Archaic occupation (9.5–8.7 ka bp; 11,150–9560 cal. BP), the lake was about half its modern extent and during the second lowstand phase ( 4 m bpl and the lake became hydrologically closed. After 4000 cal. BP, water levels recovered and the lake approached its modern extents. An archaeological potential map based on the reconstructed paleoshorelines identified four areas with archaeological potential: these include drowned river mouths, submerged wetlands and an area of uplifted Early Holocene lakebed in northeast Rice Lake. The results illustrate that isostatically driven changes in lake paleobathymetry can be substantial and must be accounted for when attempting to reconstruct paleoshoreline positions. The approach can be applied more broadly to other basins within the Great Lakes and elsewhere to assess prehistoric site archaeological potential.

Exploration for submerged prehistoric archaeological sites in the Great Lakes (North America) is a major challenge due to difficulties in locating scant cultural artifacts in lake-bottom sediments. Stone tool microfragments (microdebitage, 106 per tool) and more dispersed around tool-making sites, but have not been identified previously in an underwater context. To evaluate their use as a submerged site indicator, microdebitage analysis was conducted on five lake sediment cores from a shallow lagoon adjacent to a long-occupied prehistoric site (McIntyre site, Rice Lake, Ontario). We identified 155 microdebitage fragments within a distinctive muddy peat horizon (2–2.5 m depth) using light microscopy and scanning electron microscopy methods. The microdebitage consisted of angular to very angular quartz fragments (400–1000 μm) with characteristic conchoidal fractures and flake scars produced by mechanical percussion. The microdebitage horizon had a distinctive bimodal particle size peak and contained a low-diversity soil thecamoebian assemblage (Phryaginella, Bullinularia sp.) indicative of a wetland environment that formed during an early Holocene shoreline transgression. Accelerator mass spectrometry 14C dating of wood fragments yielded ages of 9470–8760 ± 50 yr B.P. (11,070–9560 cal [calibrated] yr B.P.), indicating a Late Paleoindian–Early Archaic age for the deposit. Results demonstrate that coring and microdebitage analysis are effective tools in the search for underwater prehistoric sites and can be employed more broadly in exploration of submerged landscapes in the Great Lakes basins.

Eyles, N., Eyles, C., Menzies, J. & Boyce, J. 2010: End moraine construction by incremental till deposition below the Laurentide Ice Sheet: Southern Ontario, Canada. Boreas, 10.1111/j.1502-3885.2010.00171.x. ISSN 0300-9483. Just after 13 300 14C a BP in central Canada, the retreating Ontario lobe of the Laurentide Ice Sheet briefly re-advanced westwards through the Lake Ontario basin to build a large end moraine. The Trafalgar Moraine (27 km long, 4 km wide) is composed of a distinctly red-coloured silt-rich till (Wildfield Till, up to 16.5 m thick) formed by the reworking of proglacial lake deposits and soft shale bedrock. The moraine has a pronounced ramp-like longitudinal form passing upglacier into fluted till resting on exposed shale. Analysis of water well stratigraphic data, drilled sediment cores, downhole gamma-ray logs and exposures in deep test pits shows that within the moraine the Wildfield Till is built of superposed beds up to 7 m in thickness. These are inferred to result from the repeated incremental deposition of fine-grained debris being moved towards the ice margin as a deforming bed such as identified at modern glaciers. A total till volume of 0.81 km3 was produced in a very brief time-span along a transport path probably no greater than 10 km in length. Subglacial mixing of pre-existing sediment and soft shale was clearly a very effective process for generating and moving large volumes of till to the ice margin. Similar till-dominated end moraines occur widely around the margins of the Great Lake basins, where the markedly lobate margin of the retreating Laurentide Ice Sheet re-advanced repeatedly into proglacial lakes and over fine-grained sediment. This suggests the wider applicability of the till transport and incremental depositional model presented here.

Ballast stone deposits are a common feature of sediments in ancient harbour basins but are often overlooked as a potential source of archaeological information. Recent geophysical investigations at Caesarea Maritima in Israel have discovered a thick, laterally extensive ballast layer in the area seaward of the 1st c. BC Roman harbour. The ballast deposits were identified by low-relief mounds on the seabed with elevated magnetic intensities. Jet probing and excavation of magnetic anomalies at several locations revealed a 20–60 cm thick rubble layer containing large quantities of Late Roman and Byzantine pottery, local sedimentary boulders (kurkar sandstone, limestone cobbles) and foreign igneous and metamorphic boulders (granite, schist, volcanics; ca. 50%). The foreign boulders and pottery identify the rubble layer as ballast and ships refuse jettisoned by merchant ships outside the harbour. The strong magnetic contrast between the ballast deposits and the natural seabed sediments is attributed to the high magnetic susceptibility (>10−3 SI) of crystalline boulders and pottery materials within the ballast rubble. AMS 14C and OSL dates and pottery evidence indicate the ballast accumulation began in the Late Roman period (ca. 200–330 AD) and continued well into the Late Byzantine (ca. 7th c. AD). The main phase of ballast deposition (ca. 4th–5th c. AD) coincided with a decline in the state of Caesarea's harbour following a destructive tsunami event in the early 2nd c. AD and records a shift to a more intensive use of the area seaward of the harbour as an anchorage and ballast lightening area.

The sedimentary characteristics of shell beds within an interpreted tsunami deposit from Sur Lagoon, Oman were examined using shell taphonomy and high-resolution particle-size analysis. The tsunami bed was deposited by the 28 November, 1945 tsunami generated by the Makran subduction zone. Q-mode cluster analysis of particle-size data was evaluated as a means of discriminating individual tsunamite shell layers from lagoonal intertidal deposits. Results showed that the tsunami shell bed was more poorly sorted, and heterogeneous (in both the digested and undigested samples) than the background lagoonal sediments. The tsunami bed thickness correlated generally with the thickness of the shell-bed, however, cluster analysis extended the tsunami unit several centimeters above or below the shell bed in some cores. The particle-size analysis also showed subtle textural trends in the tsunami unit, suggesting that the tsunami bed was deposited in several distinctive phases during tsunami incursion into Sur Lagoon. The findings indicate that cluster analysis of particle-size data can be used to identify tsunami beds in intertidal environments and holds potential for identifying paleotsunami deposits in sediments from embayed intertidal–subtidal siliciclastic systems where obvious sedimentary structures may be absent.

Colonel By Lake, located near Kingston, Ontario, was created in the early 19th century during the construction of the Rideau Canal waterway. Canal flooding inundated a large area of the Cataraqui River lowlands, submerging important pre-contact and colonial settlements. In order to gain a better understanding of the pre-canal environment and its archaeological setting, a systematic bathymetry and side-scan sonar survey was conducted over a 2-km2 area of Colonel By Lake. A 2-D digital bathymetric model (DBM) of the lake bottom was constructed and overlain with side-scan mosaics to map the paleogeography of the river flood plain. The data-fused sonar images clearly identify the submerged pre-canal topography, including the former Cataraqui River channel, relict meanders, tree stump fields, and bedrock uplands defining the valley sides. By comparing the DBM with landscapes depicted in pre-canal period maps (ca. 1828), the locations of several potential archaeological targets were identified. The DBM provides a basis for mapping submerged cultural resources in the Rideau and for predicting the location of undiscovered archaeological sites. The results show that integration of single-beam bathymetric mapping with side-scan imagery is an effective strategy for mapping submerged terrestrial landscapes and archaeological inventory in shallow water settings. © 2008 Wiley Periodicals, Inc.

This study addresses the paleogeographic coastal evolution of the coastal plain in the environs of Iskele, Turkey. Eight sediment cores were collected along a north–south and east–west transect and analyzed to determine whether the coastal environment had changed in the recent past. The results illustrate that the coastal environment consisted of a transgressive systems tract, ending approximately 6000 BP and represented by marine transgression, flooding of incised river channels, and marsh development, followed by a high stand systems tract. Five major environmental facies were identified: terrestrial, wetland, lagoon, foreshore, and upper shoreface. The high stand systems tract was characterized by the development of a beach-barrier consecutive series of longshore transport-derived sandbars. These sandbars contributed to the creation and eventual isolation and terrestrial infilling of nearshore lagoons and wetlands. Sea-level indicators indicate rapid sea-level rise reaching a peak approximatel...

This study examines the anthropogenic alteration of sedimentation in Frenchman’s Bay in Lake Ontario, using high-resolution particle size analysis in two 200 cm cores. Lithofacies were determined using the particle size data of both the terrigenous sediment and terrigenous sediment + diatom fractions. Terrigenous particle size data from the centre of the lagoon provided the most representative record of anthropogenic impacts. Three distinctive lithofacies were recognized: (1) a Natural Wetland (NW) lithofacies (106–200 cm) had an average mean particle size of 49.4 μm, a mode of 29.4 μm and an average standard deviation of 119.1 μm; (2) an Agricultural and Deforestation (AD) lithofacies (40–105 cm) had a statistically significant lower average mean (30.8 μm), mode (13.5 μm), and standard deviation (48.5) μm; (3) an Urbanized (U) lithofacies (0–40 cm) showed a continued trend towards smaller particle sizes with an average mean of 21.2 μm, a mode of 9.4 μm, and an average standard deviation of 32.7 μm. The lithofacies correlated with previously identified trends in thecamoebian biofacies and magnetic susceptibility data showing post-colonial lagoon eutrophication and increased overland soil erosion. The up-core trend towards finer and less variable particle sizes is attributed to erosion of fine-grained watershed sediments (glacial Lake Iroquois silts and clay) during land-clearance and modification of natural drainage patterns. The influx of silts and clays into the lagoon is also recorded by increased sediment accumulation rates and a reduction in seasonal sediment variability in the wetland. Based on the 210Pb dates, sedimentation rates increased at 1850 ±56 AD (AD lithofacies) and suggest an exponentially increasing trend in accumulation rates. Increasing sedimentation rates can be attributed to the progressive loss of native vegetation and intensified erosion of Lake Iroquois deposits via stream and hillslope erosion. Ecologically, the increased input of fine-grained sediments into the wetland has resulted in reduced water clarity and has altered the wetland substrate contributing to wetland loss in Frenchman’s Bay.

Frenchman’s Bay, on the northern shore of Lake Ontario, has been negatively impacted by eutrophication in the last 50 years through urbanization and the use of chemical fertilizers. Eutrophication began with wholesale land clearance and agricultural practises beginning in the mid-nineteenth century and reached a peak with urbanization after World War II. Eutrophication and the effects of land-use changes on the watershed were investigated by a combined analysis of the sediment magnetic properties and arcellacean (thecamoebian) microfauna. Micropaleontological analyses were conducted on two 2-m-long cores (FMB1 and FMB2) every 10 cm (42 samples) and magnetic susceptibility was measured at 2-cm intervals. Both cores showed a distinct correlative transition at 60 cm and 110 cm that was marked by a rapid increase in thecamoebian concentrations (from approx. 10×103 to 30×103 specimens per cc) and a large increase in Cucurbitella tricuspis (from approx. 10–20% to 40–70%). This transition correlated with a marked increase in magnetic susceptibility (150–200×10−8 m3 Kg−1) at the same depth, which was attributed to elevated levels of detrital magnetic minerals derived from land clearance and soil erosion in the watershed. It was indicated by 210 Pb dates indicate that there was a gradual onset of eutrophication in the mid-nineteenth century (AD 1850±56) and a more rapid rise in the mid-1940s to late 1950s. The initial increase in eutrophication was due to land clearing, agricultural development and increased nutrient loadings. The major eutrophication increase in the 1950s was from urbanization and storm sewer discharge loaded with high yield chemical fertilizers from lawns and gardens. This high concentration of nutrients has led to an unprecedented level of eutrophication within the wetland.

The remediation of toxic sediment in harbours and urban waterways requires detailed mapping of contaminated sediment distribution and thickness. Conventional methods rely on interpolation of pollutant concentrations from widely spaced core samples but can lead to significant errors in estimating sediment distribution. An improved approach, as demonstrated by recent work in Hamilton Harbour in Lake Ontario, is to estimate pollutant levels from proxy measurements of sediment magnetic properties. Measurements from 40 core samples collected within the harbour show that the magnetic susceptibility of a contaminated upper layer of sediment is one to two orders of magnitude greater than in the underlying uncontaminated ‘pre-colonial’ sediments. The susceptibility contrast results from elevated levels of urban-source magnetic oxides and is sufficient to generate a total field anomaly (ca. 5–40 nT) that can be measured with a towed magnetometer. Systematic lake-based magnetic surveying (>500 line km) of the harbour using an Overhauser marine magnetometer identifies well-defined positive magnetic anomalies that coincide with mapped accumulations of contaminated sediments on the harbour bottom. Forward modelling of the anomalies shows that the magnetic response is consistent with a contaminated upper layer thickness of up to 5 m. Apparent susceptibility maps calculated from magnetic survey data show a close spatial correspondence with core-derived magnetic susceptibilities and provide a rapid means for classifying contaminated sediments. Detection of shallow magnetic anomalies is dependent upon a closely spaced survey grid (

A marine geophysical survey was conducted at Caesarea Maritima, Israel, to map the buried structure of King Herod's Roman harbour. Magnetic surveys reveal the presence of an extensive hydraulic concrete foundation below the ruined harbour moles. The magnetic anomaly patterns indicate that the concrete foundation was laid out in header fashion along N-S and W-E trending segments to form two large ‘artificial islands’. Magnetic lows within the structure identify baffles that were infilled with sand to stabilise the concrete foundation walls. © 2004 The Nautical Archaeology Society

In North America, the last (Laurentide) Ice Sheet retreated from much of the Canadian Shield by ‘zonal stagnation’. Masses of dead ice, severed from the main ice sheet by emerging bedrock highs, downwasted in situ within valleys and lake basins and were commonly buried by sediment. Consequently, the flat sediment floors of many valleys and lakes are now pitted by steep-sided, enclosed depressions (kettle basins) that record the melt of stagnant ice blocks and collapse of sediment. At Mazinaw Lake in eastern Ontario, Canada, high-resolution seismic reflection, magnetic and bathymetric surveys, integrated with onland outcrop and hammer seismic investigations, were conducted to identify the types of structural disturbance associated with the formation of kettle basins in glaciolacustrine sediments. Basins formed as a result of ice blocks being trapped within a regionally extensive proglacial lake (Glacial Lake Iroquois ∼12,500 to 11,400 years BP) that flooded eastern Ontario during deglaciation. Kettles occur within a thick (>30 m) succession of parallel, high-frequency acoustic facies consisting of rhythmically laminated (varved?) Iroquois silty-clays. Iroquois strata underlying and surrounding kettle basins show large-scale normal faults, fractures, rotational failures and incoherent chaotically bedded sediment formed by slumping and collapse. Mazinaw Lake lies along part of the Ottawa Graben and while neotectonic earthquake activity cannot be entirely dismissed, deformation is most likely to have occurred as a result of the rapid melt of buried ice blocks. Seismic data do not fully penetrate the entire basin sediment fill but the structure and topography of bedrock can be inferred from magnetometer data. The location and shape of buried ice masses was closely controlled by the graben-like form of the underlying bedrock surface.

Basement fault reactivation is now recognized as an important control on sedimentation and fault propagation in intracratonic basins. In southern Ontario, the basement consists of complexly structured mid-Proterozoic (ca. 1.2 Ga) crystalline rocks and metasedimentary rocks that are overlain by up to 1500 m of Paleozoic sedimentary strata. Reactivation of basement structures is suspected to control the location of Paleozoic fault and fracture systems, but evaluation has been hindered by a limited understanding of the regional structural characteristics of the buried basement. New aeromagnetic- and gravimetric-lineament mapping presented in this paper better resolves the location of basement discontinuities and provides further evidence for basement controls on the distribution of Paleozoic fault and fracture systems. Lineament mapping was facilitated by reprocessing and digital image enhancement (micro-levelling, regional residual separation, derivative filtering) of existing regional gravity and aeromagnetic datasets. Reprocessed images identify new details of the structural fabric of the basement below southern Ontario and delineate several previously unrecognized aeromagnetic and gravity lineaments and linear zones. Linear zones parallel the projected trends of mid-Proterozoic terrane boundaries identified by field mapping on the exposed shield to the north of the study area, and are interpreted as zones of shearing and basement faulting. Mapped aeromagnetic and gravity lineaments show similar trends to Paleozoic faults and fracture networks and broad zones of seismicity in southern Ontario. These new data support an ‘inheritance model’ for Paleozoic faulting, involving repeated reactivation and upward propagation of basement faults and fractures into overlying cover strata.

The remediation of contaminated sediments in industrialized harbors and waterways is a growing environmental concern in North America. More than 100 marine ports and 42 inland harbors in the Great Lakes basins are currently listed by U.S. and Canadian regulatory agencies as having severe habitat and water-quality impairments due to bottom-sediment toxicity. Current approaches to remediation include sediment dredging and removal, capping with clean sediment, and in-situ treatment with oxidants.

Recent work in southern Ontario, Canada, demonstrates anomalously high vertical groundwater flow velocities (>1 m/year) through a thick (as much as 60 m), sandy silt till aquitard (Northern till), previously assumed to be of very low permeability (hydraulic conductivity

Upper and Middle Waterton lakes fill a glacially scoured bedrock basin in a large (614 km2) watershed in the eastern Front Ranges of the Rocky Mountains of southern Alberta, Canada and northern Montana, U.S.A. The stratigraphic infill of the lake has been imaged with 123 km of single-channel FM sonar (`chirp') reflection profiles. Offshore sonar data are combined with more than 2.5 km of multi-channel, land-based seismic reflection profiles collected from a large fan-delta. Three seismic stratigraphic successions (SSS I to III) are identified in Waterton Lake resting on a prominent basal reflector (bedrock) that reaches a maximum depth of about 250 m below lake level. High-standing rock steps (reigels) divide the lake into sub-basins that can be mapped using lake floor reflection coefficients. A lowermost transparent to poorly stratified seismic succession (SSS I, up to 30 m thick) is present locally between bedrock highs and has high seismic velocities (1750–2100 m/s) typical of compact till or outwash. A second stratigraphic succession (SSS II, up to 50 m thick), occurs throughout the lake basin and is characterised by continuous, closely spaced reflectors typical of repetitively bedded and rhythmically laminated silts and clays most likely deposited by underflows from fan-deltas; paleo-depositional surfaces identify likely source areas during deglaciation. Intervals of acoustically transparent seismic facies, up to 5 m thick, are present within SSS II. At the northern end of Upper Waterton Lake, SSS II has a hummocky surface underlain by collapse structures and chaotic facies recording the melt of buried ice. Sediment collapse may have triggered downslope mass flows and may account for massive facies in SSS II. A thin Holocene succession (SSS III

Deposits left by continental ice sheets are characterized by sedimentological complexity and stratigraphic heterogeneity, but stratigraphic descriptions of such deposits, and resulting “first-generation” facies models, are still based primarily on one- or two-dimensional borehole or outcrop data. Reconstruction of depositional environments, hydrogeological investigations of Pleistocene glacial deposits, and hydrocarbon exploration in pre-Pleistocene glaciated basin fills require a more detailed understanding of the form and heterogeneity of lithofacies sequences in three dimensions. Architectural element analysis is used widely by sedimentologists for categorizing internal stratigraphic heterogeneity in sandstones, particularly those of fluvial origin. This paper demonstrates the first application of architectural element analysis to glacial deposits such as tills. Outcrop, borehole, and a broad range of subsurface geophysical data were collected from a thick (60 m) till sheet present across an 80 km 2 study area near Toronto, Canada. The till sheet is not homogeneous, but is composed of three distinct architectural elements and associated lithofacies, viz, diamict elements, interbeds of subglaciofluvial sediments, and glaciotectonically deformed zones. Application of architectural element analysis to these subglacial strata provides insights into the origin of drumlin bedforms and subglacial processes below the Laurentide Ice Sheet and creates a framework for understanding ground-water and contaminant movement in underlying aquifers.

Over large areas of the western interior plains of North America, hummocky moraine (HM) formed at the margins of Laurentide Ice Sheet (LIS) lobes that flowed upslope against topographic highs. Current depositional models argue that HM was deposited supraglacially from stagnant debris-rich ice (`disintegration moraine'). Across southern Alberta, Canada, map and outcrop data show that HM is composed of fine-grained till as much as 25 m thick containing rafts of soft, glaciotectonized bedrock and sediment. Chaotic, non-oriented HM commonly passes downslope into weakly-oriented hummocks (`washboard moraine') that are transitional to drumlins in topographic lows; the same subsurface stratigraphy and till facies is present throughout. These landforms, and others such as doughnut-like `rim ridges', flat-topped `moraine plateaux' and linear disintegration ridges, are identified as belonging to subglacially-deposited soft-bed terrain. This terrain is the record of ice lobes moving over deformation till derived from weakly-lithified, bentonite-rich shale. Drumlins record continued active ice flow in topographic lows during deglaciation whereas HM was produced below the outer stagnant margins of ice lobes by gravitational loading (`pressing') of remnant dead ice blocks into wet, plastic till. Intervening zones of washboard moraine mark the former boundary of active and stagnant ice and show `hybrid' drumlins whose streamlined form has been altered by subglacial pressing (`humdrums') below dead ice. The presence of hummocky moraine over a very large area of interior North America provides additional support for glaciological models of a soft-bedded Laurentide Ice Sheet.

Polished slip planes resulting from Basin and Range detachment faulting of mid-Tertiary volcaniclastics are well exposed at Lake Pleasant, Arizona, U.S.A. Slip planes show erosional features formed by abrasion below moving sheets of gouge (coarse-grained diamict) during repeated faulting and shearing. Tectonically generated forms are identical to those found in glaciated terrains. Slip planes show ‘rat-tail’ ridges and grooves (‘ridge-in-groove structures’), ‘nail head’ striations and ‘wear tracks’. A prominent morphological element consists of flute ridges, up to 30 cm wide and at least 7 m long, formed of gouge preserved in the lee of boulders projecting as obstacles above slip surfaces. Crescentic scours around the stoss side of such boulders record enhanced abrasion by ‘streams’ of gouge debris. Clasts are striated and show shapes comparable to ‘flat iron’ clasts produced by glacial abrasion. Kinematic indicators at Lake Pleasant are directly comparable in form to flutes and drumlins in glaciated terrains. The data presented here not support a recent hypothesis arguing that glacial striations, flutes and drumlins are the product of turbulent subglacial meltwater. Instead, diamict produced along fault planes (gouge) by low-grade shearing is directly comparable to diamict facies (deformation till) formed by pervasive shear at the base of ‘soft-bedded’ ice sheets. Both facies are tectonically generated cataclastites produced in low-grade shear zones and display genetically related, but differently scaled, streamlined bedforms.

The search for new landfill sites in the Greater Toronto area of southern Ontario, Canada, is producing a wealth of data regarding the subsurface stratigraphy and geometry of Late Wisconsin (

Determining the position of Liman Tepe's (ancient `Clazomenae') archaeological features relative to the coastline is important for understanding their intended function and reconstructing the character of Aegean maritime activities and sea-based trade. Previous attempts at reconstructing harbour locations at Liman Tepe relied on extrapolating paleoenvironments based on modern surface topography. In light of this, samples from a sediment coring survey and terrestrial and underwater archaeological excavations were analysed using multi-proxy geoarchaeological methods to determine paleoenvironmental facies. Micropaleontological (foraminifera), sedimentological (grain-size analysis) and geochemical (delta C-13/delta O-18) analyses resulted in the reconstruction of the coastal paleogeomorphology, including the presence and absence of ancient harbouring areas. Neither of the previous coastal reconstructions was supported by the new results. Instead, two separate harbouring areas were recognized, one coincident with the Early Bronze Age (4800-3900 years bp) and a second during the archaic and classical periods (c. 2800-2400 years bp). These results emphasize the necessity for multi-proxy geoarchaeological studies when approaching coastal archaeological sites as a means to reconstruct paleocoastal geomorphology and understand ancient maritime development better.

Lake Wanapitei, located within the Southern Province of Ontario, Canada, provides the setting for a unique study of an impact crater situated within a shield environment. Evidence for the 7.5-km-diameter Wanapitei impact includes a circular Bouguer gravity low centered over the central area of the lake and features of shock metamorphism in samples of glacial drift found on the southern shores. Geophysical studies of craters in hard-rock environments are often limited by the lack of markers used for exploration; this may be overcome with the use of the large igneous dike swarms that characterize Archean terrains. The 1.2 Ga Sudbury dike swarm predates the impact that is suggested to have generated Lake Wanapitei and provides the setting for a study to constrain the size and location of the impact crater. The swarm is clearly visible on aeromagnetic maps as high amplitude, linear features, suggesting they could be used as vertical markers indicative of structural changes having an effect on target rock susceptibilities.To fully establish the size of the crater, a total fi eld magnetic map was produced to trace the Sudbury dikes through the proposed crater center. A gap in their signature, expressed as a 100 nT low, 2–3 km in width, constrains the size of the crater to

The remediation of toxic sediments in harbours and urban waterways requires detailed mapping of contaminated sediment distribution and thickness. Conventional methods rely on interpolation of pollutant concentrations from widely spaced core samples but can lead to significant errors in estimating sediment distribution. An improved approach, as demonstrated by recent work in Hamilton Harbour, in southern Ontario, is to estimate pollutant levels from ‘proxy’ measurements of sediment magnetic properties. Measurements from 40 core samples collected within the harbour show that the magnetic susceptibility of the contaminated upper layer of sediment is up to two orders of magnitude greater than in the underlying uncontaminated ‘pre-colonial’ sediments. The susceptibility contrast results from elevated levels of urbansourced magnetic oxides and is sufficient to generate a measurable total field anomaly (ca. 5-40 nT) that can be measured with a towed magnetometer. Lake-based magnetic surveying (> 500 line km) of the harbour using a towed Overhauser marine magnetometer clearly identifies a number of shallow magnetic anomalies which coincide with known contaminant ‘hot-spots’ and accumulations of urban sediments on the harbour bottom. Detection of shallow sediment magnetic response is dependent upon a closely spaced survey grid (< 75 m line spacing, 1 m inline sampling) and careful post-cruise processing to remove diurnal, regional and water-depth related variations in the magnetic field intensity.

The tectonic 'rejuvenation' of Precambrian basement faults is now recognized as an important mechanism for generating intraplate earthquakes. In many areas of intraplate North America, concern for the design and safe operation of strategic facilities (e.g. nuclear generating stations) has prompted efforts to re-evaluate basement seismic hazards and map zones of basement faulting. In southern Ontario, Canada, recent efforts have focused on evaluating deeply seated Grenville-age (ca. 1.2 Ga) basement fault zones. The present study is applying a multi-parameter geophysical approach to investigate basement fault zones underlying several lake basins in southern Ontario. Geophysical investigations have included collection of >2000 line km of high-resolution lake-based magnetic surveys (50-100 m line spacing, 1 m in-line sampling), 5-15KHz sub-bottom sonar profiling and side-scan images in western Lake Ontario and Lake Simcoe. Results from western Lake Ontario delineate a prominent, west-east linear magnetic anomaly that is coincident with normal faulting (up to 50 m displacement) of bedrock below the buried Dundas Valley. The anomaly is aligned with surface topographic lineaments on the valley floor and the trend of a previously mapped fault with basement magnetic expression (the Hamilton-Presqu’ile fault). Magnetic mapping in western Lake Simcoe reveals west-east trending linear magnetic anomalies that displace a major Grenville-age terrane boundary. The magnetic boundaries are spatially co-incident with faulting, slumps and gas-escape structures in lake-bottom sediments and are interpreted as reactivated basement faults.

An alternative logarithmic transformation procedure is proposed for emphasizing the structural information present in magnetic data. The procedure enhances subtle geologic information present at low-amplitude values and yet preserves the relative amplitude information. The application of the procedure is demonstrated by considering a portion of a 1983 helicopter-based aeromagnetic survey of the Hemlo gold camp on the north shore of Lake Superior.

On 28 November 1945, in the Makran trench off Pakistan, a large earthquake (8.1 Mw) produced a tsunami that struck the coast of Oman and left a taphonomically distinct shell bed in Sur Lagoon. The shell bed was thick (5–25 cm) and laterally extensive, covering a >1 km2 area. The shell assemblage from the deposit contained a mean of 59% for articulated bivalves of allochthonous offshore and subtidal species (e.g., Tellina palatam ) as well as a mean of 20% for lagoonal species, indicating large-scale erosion and transport. Taphonomic traits (e.g., articulation, rounding, fragment angularity) of all bivalve material >5.6 mm were quantified for eight sample horizons, and compared with a tsunamite from Caesarea, Israel. Some of the taphonomic characteristics between the shell beds from these two different depositional settings were similar, and three tsunamigenic specific traits were identified: (1) thickness and lateral extent of the shell deposit, (2) presence of allochthonous articulated bivalves out of life position, and (3) extensive angular fragmentation. These results show that tsunamis form shell accumulations and cannot be ignored when assessing shell bed origin for the geological record. When these three traits are collectively found, a tsunamigenic origin should be considered for the shell bed.

Underwater geoarchaeological excavations on the shallow shelf (∼10 m depth) at Caesarea, Israel, have documented a tsunami that struck and damaged the ancient harbor at Caesarea. Talmudic sources record a tsunami that struck on 13 December A.D. 115, impacting Caesarea and Yavne. The tsunami was probably triggered by an earthquake that destroyed Antioch, and was generated somewhere on the Cyprian Arc fault system. The tsunami deposit consisted of an ∼0.5-m-thick bed of reverse-graded shells, coarse sand, pebbles, and pottery deposited over a large area outside of the harbor. The lower portion of the deposit was composed of angular shell fragments, and the upper portion of whole convex-up Glycymeris spp. shells. The sequence records tsunami downcutting (∼1 m) into shelf sands, with the return flow sorting and depositing angular shell fragments followed by oriented whole shells. Radiocarbon dating of articulated Glycymeris shells, and optically stimulated luminescence (OSL) dates, constrain the age of the deposit to between the first century B.C. and the second century A.D., and point to the tsunami of A.D. 115 as the most likely candidate for the event, and the probable cause of the harbor destruction.

The Peterborough drumlin field (5000 km 2 ) is the largest in central Canada and was formed during readvance of the Laurentide ice sheet shortly after 13,000 B.P. Morphometric analysis of 998 drumlins, combined with study of 6921 borehole logs and downhole geophysical data, has established the distribution of drumlin types and their stratigraphy along a 70 km flow line through the drumlin field. In the north, drumlins are spindle-shaped, composed of till resting directly on bedrock, and were formed by deformation of till into low-pressure zones in the lee of bedrock scarps. Eskers record subglacial drainage by channeled meltwaters flowing on bedrock. To the south, drift thickness increases and eskers are absent; drumlins are larger and more ovoid and are composed of overridden proglacial and glaciolacustrine sediments overlain erosively by deformation till. Till is thin over drumlin crests and thick in interdrumlin swales and records subglacial cannibalization and mixing of overridden sediments; the drumlin form is the product of erosion by streams of deforming till flowing in swales separating cores composed of older sediments. Systematic down-field changes in drumlin shape and size can be related to decreased duration of subglacial deformation toward the limit of the readvance and increased thickness of preexisting sediments available for dissection by subglacial till streams. Absence of eskers in the central and southern parts of the drumlin field suggests that the ice base was drained by mass flow of the deforming substrate. The substantial subsurface data available from the Peterborough area indicate that drumlins are predominantly erosional in origin and are the geomorphological expression of a deforming subglacial bed below the margin of the Laurentide ice sheet.