Interpretation of seismic and potential field data from western New York State and Lake Ontario

Lithoprobe and industry seismic profiles have furnished evidence of major zones of easterly dipping Grenville deformed crust extending southwest from exposed Grenville rocks north of Lake Ontario. Additional constraints on subsurface structure limited to the postulated Clarendon–Linden fault system south of Lake Ontario are provided by five east–west reflection lines recorded in 1976. Spatial correlations between seismic structure and magnetic anomalies are described from both Lake Ontario and the newly reprocessed New York lines.In the Paleozoic to Precambrian upper crust, the New York seismic sections show: (1) An easterly thickening wedge of subhorizontal Paleozoic strata unconformably overlying a Precambrian basement whose surface has an apparent regional easterly dip of 1–2°. Minor apparent normal offsets, possibly on the order of tens of meters, occur within the Paleozoic section. The generally poorly reflective unconformity may be locally characterized by topographic relief on the order of 100 m; (2) Apparent local displacement on the order of 90 m at the level of the Black River Group diminishes upward to little or no apparent offset of Queenston Shale; (3) Within the limited seismic sections, there appears to be no evidence that the complete upper crustal section is vertically or subvertically offset; (4) Dipping structure in the Paleozoic strata (15° to 35°) resembles some underlying Precambrian basement elements; (5) The surface continuity of inferred faults constituting the Clarendon–Linden system is not strongly supported by the seismic data.Beneath the Paleozoic strata, the seismic sections show both linear and arcuate reflector geometry with easterly apparent dips of 15° to 35° similar to the deep structures imaged on seismic lines from nearby Lake Ontario and on Lithoprobe lines to the north. The similarity supports an extension of easterly dipping Central Metasedimentary Belt structures of the Grenville orogen from southern Ontario to beneath western New York State.From a comparison of the magnetic and gravity fields with the New York seismic sections, we suggest: (1) The largely nonmagnetic Paleozoic strata appear to contribute negligibly to magnetic anomalies. Seismically imaged fractures in the New York Paleozoic strata appear to lie mainly west of a positive gravity anomaly. The relationship between magnetic and gravity anomalies and the changes in the geometry of interpreted Precambrian structures remains enigmatic; (2) North to northeast trending curvilinear magnetic and gravity anomalies parallel, but are not restricted to the principal trend of the postulated Clarendon–Linden fault system. Paleozoic fractures of the Clarendon–Linden system may partly overlie a southward extension of the Composite Arc Belt boundary zone.     

Origin of Archean anorthosites: Evidence from the Bad Vermilion Lake anorthosite complex,Ontario

The Bad Vermilion Lake anorthosite complex (2,700 m.y.) is exposed over an area of about 100 km² near Rainy Lake, Ontario. As is typical of other Archean anorthosites, it is composed of coarse (1–30 cm across), equidimensional, euhedral to subhedral, calcic (An₈₀) plagioclase, in a finer grained mafic matrix. The amount of mafic matrix in individual samples ranges from none to about 70% by volume. The complex has been variably metamorphosed to greenschist facies. Zoisite, chlorite, and hornblende are abundant, but primary plagioclase is preserved in many places. The anorthosite complex is associated with gabbro and with mafic to felsic metavolcanic rocks, and is cut by tonalite plutons and by mafic dikes. Some gabbros contain local concentrations of Fe-Ti oxides and/or apatite, but no chromite. The mafic groundmass of the anorthositic rocks is similar in major and trace element chemistry, including rare earth elements, to the associated basaltic metavolcanics, suggesting that the anorthositic complex may have accumulated from a subvolcanic magma chamber which fed mafic lavas to the surface during its crystallization. Mafic flows and dikes chemically similar to the mafic metavolcanics contain plagioclase megacrysts akin to those of the anorthositic rocks, and thus may represent a link between the anorthosite complex and associated mafic lavas. Elongate pretectonic tonalite intrusions were comagmatic with the felsic metavolcanics, but not with the anorthosites or metabasalts. These silicic rocks may represent low-pressure partial melts of the mafic rocks. There is no direct or indirect evidence for significant volumes of ultramafic material at the present exposure level of the complex. An estimate of the bulk composition of all rocks presumed to be comagmatic with the anorthosites, including gabbros and mafic metavolcanics, is an aluminous basalt with about 20 wt.% Al₂O₃. This composition has REE abundances unlike those of typical Archean high-Al basalts and probably does not represent that of a primary or evolved melt. The possibility must be considered, therefore, that a substantial fraction of material comagmatic with the anorthosites has been separated from the complex, either by magmatic or tectonic processes.     

Origin of halite brine in the Onondaga Trough near Syracuse,New York State,USA: modeling geochemistry and variable-density flow

Halite brine (saturation ranging from 45 to 80%) lies within glacial sediments that fill the Onondaga Trough, a bedrock valley deepened by Pleistocene glaciation near Syracuse, New York State, USA. The most concentrated brine occupies the northern end of the trough, about 10 km downgradient of the northern limit of halite beds in the Silurian Salina Group, the assumed source of salt. The chemical composition of the brine and its radiocarbon age suggest that the brine originally formed about 16,700  years ago through dissolution of halite by glacial melt water and later mixed with saline bedrock water. Two hypotheses regarding the formation of the brine pool were tested through variable-density flow simulations using SEAWAT. Simulation results supported the first hypothesis that the brine pool was derived from a source in the glacial sediments and then migrated to its current position, where it has persisted for over 16,000  years. A second hypothesis that the brine pool formed through steady accumulation of brine from upward flow of a source in the underlying bedrock was not supported by simulation results, because the simulated age distribution was much younger than the age estimated from geochemical modeling.     

U-Pb geochronology of the Grenville Orogen of Ontario and New York: constraints on ancient crustal tectonics

Based on lithological, structural and geophysical characteristics, the Proterozoic Grenville Orogen of southern Ontario and New York has been divided into domains that are separated from each other by ductile shear zones. In order to constrain the timing of metamorphism, U-Pb ages were determined on metamorphic and igneous sphenes from marbles, calc-silicate gneisses, amphibolites, granitoids, skarns and pegmatites. In addition, U-Pb ages were obtained for monazites from metapelites and for a rutile from an amphibolite. These mineral ages constrain the timing of mineral growth, the duration of metamorphism and the cooling history of the different domains that make up the southern part of the exposed Grenville Orogen. Based on the ages from metamorphic minerals, regional and contact metamorphism occurred in the following intervals:Central Granulite Terrane:Adirondack Highlands: 1150 Ma; 1070–1050 Ma; 1030–1000 MaCentral Metasedimentary Belt:Adirondack Lowlands 1170–1130 MaFrontenac domain 1175–1150 MaSharbot Lake domain ca. 1152 MaFlzevir domain: 1240 Ma; 1060–1020 MaBancroft domain: ca. 1150 Ma; 1045–1030 MaCentral Gneiss Belt: ca. 1450 Ma; ca. 1150 Ma; 1100–1050 MaGrenville FrontTectonic Zone ca. 1000 Ma.Combination of mineral ages with results from thermobarometry indicates that metamorphic pressures and temperatures recorded by thermobarometers were reached polychronously in the different domains that are separated by major shear zones. Some of these shear zones such as the Robertson Lake shear zone and the Carthage-Colton shear zone represent major tectonic boundaries. The Grenville Orogen is made up of a collage of crustal terranes that have distinct thermal and tectonic histories and that were accreted laterally by tectonic processes analogous to those observed along modern active continental margins. The subsequent history of the orogen is characterized by slow time-integrated cooling rates of 3±1°C/Ma and denudation rates of 120±40m/Ma.     

Origin and age of The Hillocks and implications for post‐glacial landscape development in the upper Lake Wakatipu catchment,New Zealand

Ambiguous landscape histories can arise from equivocal or incomplete geomorphological, sedimentological or geochronological evidence. In this study, we apply quantitative analyses to robustly assess the origin and age of a field of rounded mounds, known as ‘The Hillocks’. Using clast analysis, the sediment is shown to be consistent with a landslide origin but inconsistent with other glacial sediments in the region. Cosmogenic ¹⁰Be exposure age dating suggests The Hillocks formed ~8 ka. Ground‐penetrating radar reveals that the deposit rests upon deltaic foreset beds; combined with topographical data, we calculate a deposit volume of ~15–27 M m³, consistent with the estimated volume of the proposed source area. Overall, our data support a rock avalanche origin, indicating that by 8 ka the valley was ice‐free at The Hillocks’ location, and the level of Lake Wakatipu was lower than 340 m asl by this time. The Dart River delta shoreline was situated somewhere between The Hillocks and the present day shoreline at that time, and has prograded at a maximum average rate of 1 m a^?1 since ~8 ka. These findings are significant given the lack of landforms by which to constrain glacial or post‐glacial landscape histories in this region of New Zealand. Copyright © 2019 John Wiley & Sons, Ltd.     

江苏南部湖成因演化再研究

记述了湖的基本特征,讨论了全新世镇江海侵对湖的影响,根据全新世各时期沉积物的分布,阐明了湖湖岸的变化;依据古生物与人类活动遗迹资料,指出湖演化发展可分为３个阶段,即距今１００００ａ～６０００ａ为雏形阶段,距今６０００ａ～２０００ａ为发展阶段,距今２０００ａ以来为现代湖成形阶段。究其成因为新构造活动—河道淤塞—人工改造而成。     

Holocene alluvial stratigraphy in the upper Susquehanna River Basin, New York

Two alluvial terraces and the present flood plain were studied at two locations along the Susquehanna and Unadilla Rivers in south-central New York state. They have formed since deglaciation and incision of the stream channels into the valley train deposits. The higher terrace has noncumulative soil profiles with well-developed color B horizons predominantly of silt loam and very fine sandy loam. The terrace is weathered to a degree similar to nearby glacial outwash terraces that have caps of similarly textured sediments. Incision that produced the terrace occurred before 9705 ± 130 yr B.P. The lower terrace is characterized by relatively thick, vertical-accretion deposits of silt loam that contain sequences of thin, buried A, color B, and C horizons. They were formed between about 3240 ± 110 (¹⁴C data of soil humin) and 235 ± 80 yr B.P. Deposits above the 235 ± 80 yr B.P. stratum are unweathered. The soil stratigraphy and ¹⁴C dates of soil humin from buried A horizons are surprisingly well correlated between sites. Most sediments of the present flood plain have been deposited since 1120 ± 80 yr B.P. Incipient A horizons and oxidation of inherited organic matter in the subsoil are the only evidence of pedogenesis in the flood-plain deposits that are older than 275 ± 80 yr B.P. The most recent flood-plain fill deposited since then is unaltered. These youngest sediments of the flood plain along with the youngest veneer of vertical-accretion deposits on the lowest terrace are associated with an increased rate of deposition largely attributable to clearing of the forests by settlers, beginning in the late 1700s. Comparison of the alluvial stratigraphy with the radiocarbon-dated pollen stratigraphy of southwestern New York (Miller 1973) reveals some apparent time correlations between alluvial events and vegetation changes. This gives reason to speculate that climatic change or forest catastrophes such as disease or drought are causes of some of the alluvial events.     

Pollution records from sediments of three lakes in New York State

Sediment core segments from Sylvan Lake, Lake Champlain and Lake Canadarago were dated radiometrically with ²¹⁰Pb and ¹³⁷Cs. Their respective sedimentation rates were determined to be 0.11, 0.14 and 0.52 g cm^?2 yr^?1. For the two lakes of lower sedimentation the variations of selected elemental abundances as function of depth were analyzed. Two groupings were found: Al, K, Ti, Rb and Zr were correlated among themselves but reflected different variations in the input of terrigenous erosion material to the lakes. The Cu, Zn and Pb correlated among themselves showed similar depth dependence with increasing concentrations toward the top which can be attributed to cultural pollution. Recent ‘excess’ fluxes to the sediments above the natural contribution by clastic material were derived for the location of the cores, which for Cu, Zn and Pb amounted to 3.8, 24 and 16 μg cm^?2 yr^?1 respectively for Sylvan Lake and 4.9, 20 and 16 μg cm^?2 yr^?1 for Lake Champlain. The corresponding ²¹⁰Pb flux was 3.3 and 2.3 dpm cm^?2 yr^?1, respectively for the two lakes.Approximate residence times in the water column were obtained for trace metals at the Lake Champlain location. Short residence times estimated for Pb (< 0.15 yr) and Cu (< 0.4 yr) indicate fast removal, whereas those for Zn (1.0 ± 0.3 yr) and Cr (2.0 ± 0.5 yr) appeared to be dominated by the water residence time.     

Paper plant effluent revisited-southern Lake Champlain, Vermont and New York

We used geologic and geochemical techniques to document the change with time of the distribution and concentration of contaminated bottom sediments in southern Lake Champlain near an International Paper Company plant. Our work, initiated in 1972, was expanded on behalf of Vermont citizens in a class-action suit against the International Paper Company. To update our 1972–1973 results, we collected nine cores in 1988 upstream and downstream from the paper plant effluent diffuser. Water content, volatile solids, organic carbon, and three ratios, Al/Si, Cl/Si, and S/Si, in addition to megascopic and microscopic observations, were evaluated to identify and trace the distribution of effluent and to measure the thickness of sediment affected by or containing components of effluent. Analyses were carried out on samples from the cores as well as from effluent collected directly from the plant's waste treatment facility. In 1973, two years after the plant opened, we cored near the diffuser; sediment contaminated with effluent was 4.5 cm thick. In 1988, in the same area, sediment contaminated with effluent was 17 cm thick. In 15 years, water content increased from 72 to 85 percent, volatile solids from 7 to 20 percent, and organic carbon from 2 to 12 percent. Cl/Si and S/Si were high only near the diffuser and were zero elsewhere. In the area of the diffuser, contaminated sediment appears to be accumulating at a rate of about 1 cm/yr. At a control location 22 km upstream (south) from the plant, the top, poorly consoli-dated layer was only 1 cm or less thick both in 1973 and in 1988. The class-action suit was settled in favor of the plaintiffs for $5 million.     

Intersecting Isograds in the Whetstone Lake Area, Ontario

Pelitic and calcareous rocks in the Whetstone Lake area havean unusually wide range of chemical composition. Metamorphicreactions have been deduced that represent the observed ‘discontinuities’in compatible mineral assemblages, and by plotting the reactantand the product assemblage of each reaction on a map, metamorphicisograds have been delincated ‘from both sides’.For the pelitic rocks, successively higher-grade isograds arebased on the following reactions: (1)chlorite+muscovite+garnetstaurolite+biotite+quartz+water; (2) chlorite+muscovite+staurolite+quartz kyanite+biotite+water; (3) kyanitesillimanite; (4)staurolite+museovite+quartzsillimanite+garnet+biotite+water. A fifth isograd, based on the reaction (5) biotite+calcite+quartzCa-amphibole+K-feldspar+carbon dioxide+water intersects the isograds based on reactions (2), (3), and (4)in such a manner as to indicate that the H₂O/CO₂ fugacity ratiowas significantly higher in the vicinity of a granite plutonthan in the metasedimentary rocks remote from the pluton. Chemicalanalyses of the coexisting minerals in reaction (5) indicatethat the real reaction may involve plagioclase, epidote, sphene,and Fe-Ti oxides as well.     

Spatial relationships between natural seismicity and faults, southeastern Ontario and north-central New York state

A statistical analysis was carried out to investigate spatial associations between natural seismicity and faults in southeastern Ontario and north-central New York State (between 73°18′ and 77°00′W and 43°30′ and 45°18′N). The study area is situated to the west of the seismically active St. Lawrence fault zone, and to the east of the Lake Ontario basin where recently documented geological and geophysical evidence points to possible neotectonic faulting. The weights of evidence method was used to judge the spatial associations between seismic events and populations of faults in eight arbitrarily defined orientation groups. Spatial analysis of data sets for seismic events in the periods 1930–1970 and post-1970 suggest stronger spatial associations between earthquake epicentres and faults with strikes that lie in the NW–SE quadrants, and weaker spatial associations of epicentres with faults that have strikes in the NE–SW quadrants. The strongest spatial associations were determined for groups of faults with strikes between 101° and 146°. The results suggest that faults striking broadly NW–SE, at high angles to the regional maximum horizontal compressive stress, are statistically more likely to be spatially associated with seismic events than faults striking broadly NE–SW. If the positive spatial associations can be interpreted as indicating genetic relationships between earthquakes and mapped faults, then the results may suggest that, as a population, NW–SE trending faults are more likely to be seismically active than NE–SW striking faults. Detailed geological studies of faults in the study area would be required to determine possible neotectonic displacements and the kinematics of the displacements.     

The sedimentary framework of the southern basin of Lake George,New York

Information from 240 km of high-resolution seismic reflection profiles has been analyzed to show the bathymetric and subsurface configuration of southern Lake George in the southeastern corner of the Adirondack Mountains, New York. Three units have been identified and sampled in 13 piston cores as long as 7 m and 4 grab samples; they are glacial drift, glaciolacustrine nonorganic clay, and Holocene lake mud rich in organic material. Three deep bedrock basins controlled glacial, glaciolacustrine, and postglacial deposition within the lake. Glaciolacustrine clay is more than 30 m thick in these basins but is generally absent in water depths less than 20 m. An unconformity separates glaciolacustrine clay from overlying Holocene mud in water depths less than 30 m, but the contact is conformable and transitional in deeper water. The unconformity may have originated from subaqueous or subaerial erosion during a low stage of lake level which probably occurred between 10,000 and 700 yr B.P. Holocene lake mud is thin to absent in the shallower waters separating the three basins, but reaches 15-m thickness near the entrance to The Narrows. A new radiocarbon date of 6950 ± 60 yr B.P. was obtained from a wood fragment which was found in the Holocene lake mud. We found no clear evidence of postglacial tectonic disturbances of the lake sediments although recent releveling profiles suggest that the Adirondack Mountains are undergoing contemporary uplift.     

A review of the literature on the formation and location of drumlins

Drumlins remain a major problem in glacial geomorphology such that no satisfactory explanation to their mode of origin exists. This review attempts, by looking at specific subsections of the drumlin problem, to place in perspective the known facts and observations on drumlins. The most recent drumlin origin theories are examined in the light of our knowledge of the subglacial environment. Although it may seem that every aspect of this unusual landform has been researched, the author will suggest areas where new studies might begin. The interdisciplinary nature of present research into drumlins is stressed. Finally emphasis is placed on finding an explanation of drumlin formation that is not unique but one which will explain this landform's development as only one product of the complex subglacial environment.     

平潭岛岚湖沉积环境和成因的研究

在中全新世后阶段，当海岸风沙正处于始发状态，平潭西南的岗湖还是一个由多叉的山谷组成的洼地。到全新世晚期，由于全球气候的变化和优势的北北东方向风力的逐渐增强，河谷洼地与海湾相联结的地区长时间风沙的堆积而形成岚湖。     

Sedimentologic and palynologic records of the last deglaciation and Holocene from Ballston Lake, New York

Continuous pollen and sediment records from two ∼8.5-m-long cores document late Pleistocene and Holocene sedimentation and vegetation change in the Ballston Lake basin, eastern New York State. Pebbles at the base of both cores and the geomorphology of the watershed reflect the presence of the Mohawk River in the basin prior to ∼12,900 ± 70 cal yr B.P. Ballston Lake formed at the onset of the Younger Dryas (YD) by an avulsion of the Mohawk River. The transition from clay to gyttja with low magnetic susceptibility (MS), low bulk density, and high organic carbon indicates rapid warming and increased lake productivity beginning 11,020 cal yr B.P. MS measurements reveal that the influx of magnetic particles, associated with pre-Holocene clastic sedimentation, ceased after ∼10,780 cal yr B.P. The pollen record is subdivided into six zones: BL1 (12,920 to 11,020 cal yr B.P.) is dominated by boreal forest pollen; BL2 (11,020 to 10,780 cal yr B.P.) by pine (Pinus) forest pollen; BL3 (10,780 to 5290 cal yr B.P.) by hemlock (Tsuga) and mixed hardwood pollen; BL4 (5290 to 2680 cal yr B.P.) by mixed hardwood pollen; BL5a (2680 cal yr B.P. to 1030 cal yr B.P.) by conifer and mixed hardwood pollen; and BL5b (1030 cal B.P. to present) by increasing ragweed (Ambrosia) pollen. A 62% decrease in spruce (Picea) pollen in <320 cal years during BL1 reflects rapid warming at the end of the YD. Holocene pollen zones record more subtle climatic shifts than occurred at the end of the YD. One of the largest changes in the Holocene pollen spectra began ∼5300 cal yr B.P., and is characterized by a marked decline in hemlock pollen. This has been noted in other pollen records from the region and may record preferential selection of hemlock by a pathogen or parasites.     

Distribution of Pb between sediments and pore water in Woods Lake,Adirondack State Park,New York,U.S.A.

Interstitial water samples and sediments were collected from acidified Woods Lake (pH= 5.0) to evaluate Pb profile stability and distribution between the solid and aqueous phases. A simple equation was developed to describe the distribution coefficient for Pb(Kd_Pb), based on the sample moisture content and analyte concentrations in bulk sediment and pore water. In Woods Lake sediment Kd_Pb values ranged from 6.7 × 10⁴to6.7 × 10⁵ml/g. The affinity of Pb for the solid phase was further demonstrated by inverting a sediment core and leaving it for 10 months in situ. Upon retrieval, the Pb profile was found to have remained intact over the same depth, albeit inverted, as in the surrounding sediment. Geochemical modeling using MINTEQA2 demonstrates that Pb solids that may reasonably be expected to precipitate were all undersaturated by several orders of magnitude with respect to the interstitial water, indicating that Pb was sorbed to, rather than precipitated in, Woods Lake sediment.     

Sequence of till deposition and erosion in drumlins

Whittecar, G.R. & Mickelson, D. M. 1977 06 01: Sequence of till deposition and erosion in drumlins.
Extensive sand and gravel workings have exposed structural and compositional features of 17 gravel-cored drumlins of late Wisconsin age in eastern Wisconsin. The drumlins are blanketed by 3 m of sandy basal till which truncates lower tills of earlier advanccs, outwash gravels, and an overlying till which is conformable to the gravel bedding and indistinguishable in composition from the surface till. Sands and gravels in the interior of some drumlins are deformed into large overturned folds, and into elastic dikes of fine sand and silt which penetrate to the top of the drumlin and warp overlying gravels. Both the folds and horizontal bedding are truncated by either the drumlin edge or the till blanket.
We interpret the conformable, truncated, and in some cases folded, till as a basal till deposited during glacial advance. The capping, truncating till is viewed as a basal till left by retreating ice.
The following sequence of events is suggested: (1) advance of ice over outwash, and deposition of till in a zone mar the margin; (2) thickening of the ice and erosion of the drumlin shapes; (3) local folding of the gravels and continued erosion; (4) retreat of ice and deposition of basal till under thin ice; (5) deposition of localized ablation till and stratified deposits.     

Origin of biotite-hornblende-garnet coronas between oxides and plagioclase in olivine metagabbros,Adirondack region,New York

Complex multivariant reactions involving Fe-Ti oxide minerals, plagioclase and olivine have produced coronas of biotite, hornblende and garnet between ilmenite and plagioclase in Adirondack olivine metagabbros. Both the biotite (6–10% TiO₂) and the hornblende (3–6% TiO₂) are exceptionally Titanium-rich. The garnet is nearly identical in composition to the garnet in coronas around olivine in the same rocks. The coronas form in two stages:

1. Plagioclase+Fe-Ti Oxides+Olivine+water =Hornblende+Spinel+Orthopyroxene±Biotite +more-sodic Plagioclase
2. Hornblende+Orthopyroxene±Spinel+Plagioclase =Garnet+Clinopyroxene+more-sodic Plagioclase

The Orthopyroxene and part of the clinopyroxene form adjacent to olivine. Both reactions are linked by exchange of Mg²⁺ and Fe²⁺ with the reactions forming pyroxene and garnet coronas around olivine in the same rocks. The reactions occur under granulite fades metamorphic conditions, either during isobaric cooling or with increasing pressure at high temperature.     

Indicator mineralogy of kimberlite boulders from eskers in the Kirkland Lake and Lake Timiskaming areas, Ontario, Canada

Sixteen kimberlite boulders were collected from three sites on the Munro and Misema River Eskers in the Kirkland Lake kimberlite field and one site on the Sharp Lake esker in the Lake Timiskaming kimberlite field. The boulders were processed for heavy-mineral concentrates from which grains of Mg-ilmenite, chromite, garnet, clinopyroxene and olivine were picked, counted and analyzed by electron microprobe. Based on relative abundances and composition of these mineral phases, the boulders could be assigned to six mineralogically different groups, five for the Kirkland Lake area and one for the Lake Timiskaming area. Their indicator mineral composition and abundances are compared to existing data for known kimberlites in both the Kirkland Lake and Lake Timiskaming areas. Six boulders from the Munro Esker form a compositionally homogeneous group (I) in which the Mg-ilmenite population is very similar to that of the A1 kimberlite, located 7–12 km N (up-ice), directly adjacent to the Munro esker in the Kirkland Lake kimberlite field. U–Pb perovskite ages of three of the group I boulders overlap with that of the A1 kimberlite. Three other boulders recovered from the same localities in the Munro Esker also show some broad similarities in Mg-ilmenite composition and age to the A1 kimberlite. However, they are sufficiently different in mineral abundances and composition from each other and from the A1 kimberlite to assign them to different groups (II–IV). Their sources could be different phases of the same kimberlite or—more likely—three different, hitherto unknown kimberlites up-ice of the sample localities along the Munro Esker in the Kirkland Lake kimberlite field. A single boulder from the Misema River esker, Kirkland Lake, has mineral compositions that do not match any of the known kimberlites from the Kirkland Lake field. This suggests another unknown kimberlite exists in the area up-ice of the Larder Lake pit along the Misema River esker. Six boulders from the Sharp Lake esker, within the Lake Timiskaming field, form a homogeneous group with distinct mineral compositions unmatched by any of the known kimberlites in the Lake Timiskaming field. U–Pb perovskite age determinations on two of these boulders support this notion. These boulders are likely derived from an unknown kimberlite source up-ice from the Seed kimberlite, 4 km NW of the Sharp Lake pit, since indicator minerals with identical compositions to those of the Sharp Lake boulders have been found in till samples collected down-ice from Seed. Based on abundance and composition of indicator minerals, most importantly Mg-ilmenite, and supported by U–Pb age dating of perovskite, we conclude that the sources of 10 of the 16 boulders must be several hitherto unknown kimberlite bodies in the Kirkland Lake and Lake Timiskaming kimberlite fields.     

Distribution of pollutants from a new paper plant in southern Lake Champlain,Vermont and New York

From November of 1973 to May of 1974, 15 arrays of sediment traps were placed along 33 km of southern Lake Champlain to sample the distribution of effluent from a large paper plant located on the western shore which had commenced operation in 1971. In the arrays located near the effluent diffuser pipeline as much as 2.3 cm of sediment accumulated, whereas elsewhere in the lake less than 1 cm accumulated. In the area of accelerated accumulation, sediments contained high concentrations of several components used in or derived from paper manufacturing. Values for kaolinite, expressed as the ratio of kaolinite to chlorite, for example, were as high as 1.4, anatase (TiO₂) concentrations were as high as 0.8%, organic carbon 8.7%, and phosphorus 254 μg/g; all were more abundant than in sediments collected in traps to the south or north. In surficial bottom sediments collected near each array organic carbon and phosphorus were also higher (4.2% and 127 μg/g respectively) near the diffuser than elsewhere. Thus, the new plant after three years of production measurably affected the composition of suspended sediment and surficial bottom sediment despite the construction and use of extensive facilities to reduce the flow of pollutants to the lake.