Sedimentology and Geochemistry of Modern Sediments in the Kingston Basin of Lake Ontario

J. Great Lakes Res. 10(4):358-374 Internat. Assoc. Great Lakes Res., 1984

SEDIMENTOLOGY AND GEOCHEMISTRY OF MODERN SEDIMENTS IN THE KINGSTON BASIN OF LAKE ONTARIO

P. G. Sly National Water Research Institute Canada Centre jor Inland Waters P. O. Box 5050 Burlington, Ontario L7R 4A6

ABSTRACT. Accumulation of Recent fine sediment is limited to deep water areas in the Kingston basin and thicknesses of more than 50 em are found only in the St. Lawrence trough; elsewhere, sands and silty sands are largely composed ofreworked material. Local sources provide little input of fine sediment to the Kingston basin. Statistical relationships derived from geochemical analyses indicate several forms of association between heavy metals and organic carbon, sulphides, clays, hydrous Fe and Mn oxides, and carbonates. A comparison between Kingston and Niagara sediments shows that the combined effects ofriverine and lacustrine erosion have resulted in a generally greater content of carbonates in the Niagara sediments. The content of Fe (which is partly influenced by redox potential) is highest, however, in sediment of the Kingston basin, where higher P values are also associated with an increased clay content. Differences in the concentrations of heavy metals in Lake Ontario, except for Hg, Co, Cu, and Zn, are largely explained by variations in silt and clay contents. Contaminant loadings from the Niagara River are largely responsible for the anomalously high concentrations ofHg and, to a lesser extent, Cu and Zn. Cobalt occurs at higher concentrations in the sediments of eastern Lake Ontario, where its presence is thought to reflect glacial dispersal patterns. ADDITIONAL INDEX WORDS: Lake sediments, trace elements, chemical composition, geomorphology.

INTRODUCTION

Although both Niagara and Kingston sites lie within the same lake, they differ considerably. At Niagara, sediment accumulation rates are high, and distributions largely reflect the modern environment. The morphological association between shoreline and Niagara bar deposits is generally accompanied by similarities in coarse sediment texture and composition which also reflect the dominance of longshore drift in the nearshore zone. On the other hand, silty sediments show very different dispersal patterns associated with the Niagara River plume, in which organics (from both in-lake and anthropogenic sources) are combined with a range of natural and enriched trace-metals. Clayey sediments, which accumulate as bottomset beds in deep water, show little direct effect from riverine contributions; they are, instead, characteristic of largely independent mid-lake processes.

One of the principal difficulties in studies on sediment/water interaction has been to make direct comparisons between sedimentological and geochemical characteristics at different locations. There has been no standard format which could be applied in different aquatic environments (Golterman et al. 1983, de Groot et al. 1983). However, following the development of a satisfactory model of low and high energy (boundary 2.7 phi) waterlain sediments (Sly et al. 1983), based on skewness/kurtosis measures, it has become possible to link sedimentological and geochemical parameters in a uniform manner. This approach was first applied in western Lake Ontario, where Sly (1983a) described the occurrence of recent sediments at the mouth of the Niagara River, as an example of point source dispersal. 358

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY The Kingston basin of Lake Ontario, now described, is characteristic of another type of sedimentary environment in which there is generally very little accumulation of Recent fine sediment. Sly and Prior (1984) described the late glacial and postglacial evolution of the Kingston basin and demonstrated that early postglacial deposits have been reworked in response to fluctuating water levels. Lag gravels and gravelly sands are typical of many areas in the basin where water depths are 20 to 25 m or less, but little coarse sediment is now being contributed to the basin from the surrounding shore-line. Redistribution of sand and silty sand is likely to water depths of at least 20 m (Sly 1975). Accumulations of Recent fine sediment appear to be limited to areas where depths exceed 25 to 30 m outside the St. Lawrence trough, or 35 to 40 m within the trough; but, the fact that many such deposits are only a few centimetres thick suggests that these areas are subject to both seasonal deposition and reworking. Only at depths in excess of 35 m is there a significant accumulation of fine silt and clay. The intent of this paper is to show that the techniques of data analyses, previously applied at Niagara, are equally applicable to the Kingston site; and that direct comparisons of data from both sites are possible. It is not the intent to use the data to provide a detailed explanation of geochemical associations, the study of which requires a different approach. PROCEDURES A nested grid (Sly 1969a) sampling pattern was used in the Kingston basin, with a minimum sample spacing of 100 ft (30 m) and a maximum spacing of 10,000 ft (3,048 m), comprising 281 sample locations. The data are reported in Sandilands and Sly (1977). A Mini-Fix navigation system provided accurate positioning (± 6 m at the 750/0 probability level, over most of the area), and a double Shipek grab sampler (Sly 1981) was used to recover surficial bottom sediments. A 2-cm-deep sub-sample was taken from the grab samples for particle-size and geochemical analyses (Sly 1983a). A Benthos gravity corer (Sly 1969b) was used to obtain sediment cores. Particle-size was determined using standard sieving and pipette procedures and samples were freeze-dried and ground to 100 mesh before geochemical analyses. A Philips PW1220C X-ray fluorescence spectrometer was used to determine major element concentrations (AI, Ca, Fe, K,

359

Mg, Mn, Na, P, Si, and Ti). These XRF values were reported to 0.01 per cent concentration, with repeatability often better than 95 per cent. Trace elements were analysed by atomic absorption (Thomas et al. 1972, 1973) and AAS values were reported to 0.1 p,g/g for all elements except Cd and Hg which were reported to 0.01 p,g/¥>. Over most of the naturally occurring concentration ranges repeatability was better than 90 per cent. Field geochemistry (temperature, Eh, pH) followed procedures of Thomas et al. (1972). Echo sounding was carried out with a Kelvin Hughes MS 32M (14.25 KHz) sounder, and an MS 26F (30KHz) sounder equipped with a ground discrimination transducer. Side scan sonar data were obtained using an E. G. and G. Mark I dual channel system (200 KHz). Sounding lines were spaced 400 to 600 m apart. Samples were collected in 1970, and further details are provided in Sandilands and Sly (1977). SEDIMENT ACCUMULATION The bathymetry of the study area is shown in Figure 1, in which a series of well-defined ridges trend northeast-southwest. Broad and relatively shallow sub-basins lie between the ridges, and open to the west and southwest. For convenience, these subbasins have been numbered I-IV, with IV (the St. Lawrence trough) being the largest and deepest of these features (Fig. 2). Five core samples are used to illustrate the relationships between the modern and early postglacial deposits. In each case, undrained shear strength (measured at l-cm intervals with the fall-cone test; Hansbo 1957, Sly 1983b) is related to core depth and lithology, and echo trace data. Locations are shown in Figure 2, and cores in Figures 3-6. Core 843 is not shown. Site 636: This lies close to the west side of the northern part of the St. Lawrence trough (IV). A thin layer of modern silty clay (less than 30 cm thick) overlies sediment of unit C (Sly and Prior 1984) which is estimated to be about 10,500 to 11,000 years old. Undrained shear strengths increase slightly from about 1.0 kPa to 3 kPa between core depths of 30 to 125 cm and are typical of early Holocene sediments in the Kingston basin. Site 701: This core comes from the western end of sub-basin II, on the north side. Low undrained shear strengths (0.5 to 2 kPa), again, mark the presence of modern sediment to a depth of 15 cm

360

P. G. SLY

KINGSTON BASIN Bathymetry Depths in metres

~ 15m or less •

35m or more

HAMlLlON ;II

FIG. 1. Bathymetry of Kingston basin study area.

o i

2

3

4

5km i

KINGSTON BASIN

Sub - Basins (I -

I':;~:'

o

nn

:'1 Bedrock exposed Coarser than 3 phi

r.w:ol W:l Finer

than 3 phi

.

I::::::::::~ ..... Finer

than 6 phi

mean particle size

0773 Core locations

~= ~

FIG. 2. Distributions of sediment grain-size and recent sediment accumulation, and core locations.

"

2-6cm sandy silt over sands and gravelly sands.

2-6cm silty mud and sandy silt over sands gravelly sands • and firm clays ~ .'.

DUCK ...\~tJ.Sl:.~NI? 6' YORKSHIRE ~

o I

2

3

4

5km I

ISLAND

up to 1.5m of soft mud Oller glaciolacustrine clays (mostly 10-50cm of mud)

43

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY Undrained shear strength kPa

Core NO. 636 water depth 27. 9 m

Sandy silt layer

o

Sitty clay

361

1.0

with strongOQ1

10.0 100.0

1JYR2.5/1 sulphide odour, ..

effer\lesces with

H CI.

Approx: posn.

20

Firm sitty clay with

core 636

20

clear laminations no sulphide odour and no efflllV8SCel1CEl

40

60

E 0

20-'

40

5YR4/1 from HCI.

i0

60

~

.

~

0;

.!:

80

J:

g

80

u

Q)

i

30-

.g

g100

~ Q)

100

.!1 0

120

FIG. 3. Core data, location #636.

~

120

140

140

160

160

Undrained shear strength kPa

Core NO. 701 water depth 33.8m

o

~Y_2-,-5,I1

50-

to

10.0 100.0

Soft sitt

Approx. pesn.

core 701

Sitty clay

20

5Y4/1

::::::~and

20

dark banding (no odour and no HCI effervescence)

40

40

60

60

HCI effervesence

80

lAlry fine sand with shel fragments

100 5Y5/1

120

i

~~

Laminated grey clays

120

.2

140

FIG. 4. Core data, location #701.

160

0 W i!i

140

160

\

P. G. SLY

362

Core NO. 773 water depth 49.9 m

o

40

kPa

si~y

mud with 00.1 numerous strong dark laminations (weak HCI effervesand 10YR cence at gcm to 20 2.5/1 top of core)

Soft

5Y3/1

20

Undrained shear strength

5Y4/1

Firm si~y clay with 40 occasional sulphide banding to base of

\1.0

10.0 100.0 Approx. posn. 773

core

~

core. (no odour and no 60 HCI effervescence)

60

E 0 .£

80

.s::.

i S

100

~ E

~

j

50-

.§.

80

J:

100

~

120

120 SY4/~ Thin clay layer

140

(Strong HCI efferwscence )

\ 140

FIG. 5. Core data, location #773. 160

Core NO. 774 water depth 31.5 m

o 20

Soft si~ SY4/1 SY2.5!1 Soft clayey silt

60 .£

.s::.

a

40

.~

60

(;)

80

~

:~

80

>

0

c:

~

2? 100

100

8

Clay layer with very fine sand and shell fragments.

120

140

FIG. 6. Core data, location #774.

Approx. pesn. core 774

.<::

0

160

5G'i4-ii

Hard brown clay .. ----- layer SYS/1 Firm clay Strong HCI effervescence below 123 cm )

70-

Undrained shear strength kPa 1.0 10.0 100.0

20

40

E

160

120

140

160

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY within the core, below which values of 2 to 4 kPa characterize early Holocene deposits. At a core depth of about 100 cm, undrained shear strength increases to about 7 or 8 kPa and this defines the presence of glaciolacustrine clay assigned to a Lake Iroquois age (Sly and Prior 1984). Site 773: This location is near the deepest part of the St. Lawrence trough (IV) and is characterized by about 30 cm of modern silty clay « 0.1 kPa) over mid-Holocene silty clay, which extends to a core depth of at least 125 cm. Site 774: This site is characterized by the presence of thin and isolated patches of recent silty sediment which lie on the east side of the St. Lawrence trough. Modern sediment (0.2 to 1.0 kPa) occupies the upper 30 cm of the core; beneath this, early or mid-Holocene sediment extends to a depth of about 120 cm. Lake Iroquois glaciolacustrine clay forms the base of the core, and the high shear strengths (10 to 80 kPa) below 120 cm are associated with the presence of distorted sediments which are likely to have been overconsolidated. Overconsolidation results from high confinement pressures which cause dewatering and repacking of mineral grains. In order to achieve the high shear strength values measured, the sediments had to have been subject to loading pressures much in excess of the weight of initial overburden. It is believed that ice lobes in the Kingston basin provided the necessary loading during the Great Lakean Stadial, after the fall of Lake Iroquois levels. Decreased overconsolidation toward the southwest of the study area, likely reflects a thinning of the ice override (Sangrey 1970, Sly and Prior 1984). Shear strength profiles of subaerially dried sediments differ from those caused by overconsolidation because of the sharp changes which occur above/below such horizons. Changes of shear strength values beneath overconsolidation are more gradual. Site 843: At this location, at the southeastern limit of the study area, modern fine silt appears to lie almost directly upon the overconsolidated surface of Lake Iroquois clay. Modern silt is less than 15 cm thick and has undrained shear strengths of between 0.5 and 1.0 kPa. The overconsolidated clays (at core depths of 15 to 40 cm) have values reaching nearly 40 kPa, but these reduce to about 9 kPa or less between 40 to 70 cm depth. Field data indicate that water depths must be about 25 m, at least, for fine sediment to accumulate in the shallow sub-basins of the area. Thus, since levels have risen by about 10m in the past 5

363

to 6,000 years (based on the history of rising waters in Lake Ontario; Sly and Prior 1984), longterm average accumulation rates can be no more than 0.01 to 0.02 mm/yr. In the St. Lawrence trough, where water depths must be at least 35 m for the accumulation of fines, levels have risen about 20 m in the past 8,000 years. Therefore maximum longterm accumulation rates of trough sediments are likely to be a little less than 0.2 mm/yr (or about ten times greater than in the surrounding sub-basins). There is no evidence to demonstrate that modern accumulation rates are higher than this average; but, because of increased sediment loading from the watershed (Warwick 1980) and a shift toward higher trophic levels in Lake Ontario (Beeton and Edmondson 1972), it seems probable that the rate of modern deposition may have increased slightly. Surficial sub-samples of fine sediment, from the shallow sub-basins, probably represent material of very recent age (because of periodic reworking). Similar samples from the St. Lawrence trough, however, could contain material that is several decades old. GRAIN SIZE Although coarse rubble and glacial erratics, and bedrock of Ordovician limestone (Liberty 1971) outcrop on the shoal areas, and in small patches along the northeast-southwest trending ridges, most samples have a mean particle size finer than 2.7 phi. Therefore, much of the study area lies within an environment of Low Energy Regime (LER) as defined by Sly et al. (1982 and 1983). The distribution of mean particle size is shown in Figure 2. In contrast with the Niagara area (11.3 percent), however, there is significantly less silt in the coarse fractions of the Kingston basin (5.3 percent). The distribution of skewness/kurtosis values is shown in Figure 7 and these are assumed to be generally characteristic of LER sediments (Sly et al. 1982 and 1983). The skewness/kurtosis sectors represent a sequence of fining particle size; ABCD represent materials in approximate hydraulic equilibrium and sectors EFGH represent material modified by the inclusion of anomalously coarse particles. It is assumed that the presence of most coarse gravel and cobble particles in the medium fine sands and silty sands (sectors E, F) reflect the addition of small quantities of ice-drop debris, and/or lag material. Small quantities of

P. G. SLY

364

KINGSTON BASIN Skewness /Kurtosis Sectors Normal (A-D) and Modified (E - H) Low Energy Regime Sedments

......... No sample recovery

<:. ..:' (mostly bedrock)

Kurtosis ~

\

~

<'r, G


FIG. 7. Distribution of skewness/kurtosis sectors.

coarse particles also occur in the finer muds (sector G), especially in sub-basin I. If these anomalously coarse particles are excluded from the grain analyses, the mean size of sector A material is comparable to that of sector E, B to F, C to G and D to H. Only within the St. Lawrence trough (IV) do modern sediments appear to be largely free of the influence of re-worked or lag material. GEOCHEMICAL DISTRIBUTIONS As a means of further characterizing the sediments of the Kingston basin, selected distribution patterns are shown in Figures 8 to 11. The concentrations of organic (O.C.) are highest in sediments of the deepest parts of the study area (Fig. 8), and the distribution pattern is closely associated with the bathymetry. Near-bed water clarity (based on underwater photographs; Sly 1970, Sly 1983a), during mid-summer, has a similar pattern and this implies that sediment O.C. is closely associated with local plankton production. The distribution of total phosphorus (Fig. 9) shows that high concentrations are associated with

DUCK ..\~'t!.S,=~NI? ~ YORKSHIRE ~ ISLAND

the finer sub-basin sediments but it also demonstrates that highest values (up to 0.6 percent) occur in sub-basin III; the distribution of total iron (maximum about 15 percent) is similar. The water depth in sub-basin III (25 to 30 m) is slightly less than in sub-basins I or II, and the sediments are coarser (mean size 4.5 phi) than in I (6.0 phi) or II (5.9 phi). However, since coarser sediments also exist around the periphery of sub-basins I and II, without significant enrichment of P or Fe, it can be implied that an additional control influences the compositon of P and Fe in the sediments of subbasin III. The distribution of total lead (Fig. 10) shows close association with that of organic carbon, as does that of quartz-corrected mercury (quartz corrected = [E x l00]/[I00-Q] where E is concentration of element and Q is percentage of quartz; Sly 1983a) which is shown in Figure 11. The distribution of quartz-corrected lead remains very similar to that of total lead except that sub-basins I, II, and III have higher values of quartz-corrected Pb than the St. Lawrence trough (resulting from the normalizing procedure which is based on mineral

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY

KINGSTON BASIN Organic Carbon

-2

Values in percent.

2.8

1-

Point values

m-

Sub - basins

FIG. 8. Organic carbon in Kingston basin sediments.

KINGSTON BASIN Total Phosphorus Values in percent

_

.5_

«.3 not differentiateej)

I-W Sub-basin

L

FIG. 9. Total phosphorus in Kingston basin sediments.

DUCK ...4..!.Sl:~N~

~

_

tP YORKSHIRE ISLAND

365

366

P. G. SLY

KINGSTON BASIN Total Lead -50-Values in ~g/g-l(ppm)

1- nr Sub - basins

1oo

50_______

I '.

1'! ., ..

In II'

(1/

/

!«

~~~. . . . . .

0 5Oty=--•.•. . . .

SHOAL

/_~

~~--CHARITY

. . . . •. •. •

A~/

. . •

---,(",

. . .

"\ ...•.•.•... . •

loo~ .•·.•. .·• •.'•.•.) ).•.•.• .•.•.•.•.• .•.•.• .• •. .•.•. i.. •.

f/

~~O~i

1W

mn ~ SHOAL_--.~ 50

~

~~

150

. ALLANI'J

&'7

100 50

//JPIGEON SHOAL

t,y/'

~0~

~'

~/

100

f

'P' .. .

.....""

150

'9"

1>"~' ~y .

r· .. ) y .L.-~'\~%~~~11<' U Ii

~,~Q

~I

7

~I

/~I

!

FIG. 10. Total lead in Kingston basin sediments.

/

f

/

/

.

_ ----.LGL

o I

DUCK 50 ..\~'i!.Sl:~NQ g YORKSHIRE ~ ISLAND 2

3

4

5km I

KINGSTON BASIN Quartz Corrected Mercury

_

-2.0- Values in ~g/g-l(ppm)

_

to

lOtS

1- nr Sub - basins

",.

je----

2.0

2.2t,y/

~~/ tfJ'

~.,.

2.2

~~~~ ~,~Q

2.0

~1 u

~

I

!

L

FIG. 11. Quartz-corrected mercury in Kingston basin sediments.

~

#1

I

1.0~

~,

c:~y

DUCK ..\~'i!.S~~NQ tP YORKSHIRE ~ ISLAND

/

f

/-, /

/

.

_ 2.0

t51.o

to

1.5

367

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY content rather than O.C.). Under some conditions the concentration gradients of heavy metals, such as Pb and Hg, can be used to define transport or dispersal pathways. Figures 10 and 11 show no evidence of point source dispersal; rather they imply selective accumulation in areas of non-point source subject to bathymetric control. SECTOR RELATED GEOCHEMISTRY-SECTOR E The bulk geochemistry of Kingston basin sediments (Sandilands and Sly 1977) is grouped in terms of their sedimentological characteristics, using skewness/kurtosis relationships. This makes it possible to differentiate between modern deposits and reworked or modified sediments, which cover much of the Kingston basin (Fig. 7). Modern deposits are composed of unmixed particle-size populations which are generally in equilibrium with existing sedimentary conditions, and are characterized by groups A-D. Mixed population sediments (which contain both modern and older materials, e.g., lag deposits and reworked glaciolacustrine clay) are characterized by groups E-H. Coarse sediments are discussed first. Most coarse sediments have been reworked, and their major element associations (sector E, 1.9 mean phi size) are presented in summary form, as a correlation analysis based on 78 samples (Table 1). The highest positive correlations are held by Fe, P, and Zn which are present as coatings on grains (Cronan and Thomas 1972), and by Zn and O.C.; the negative correlations between Mg, Ca, and Si seem to characterize the presence of glacially derived and silica dominated sands (mean Si02 content 78 0J0) within areas of carbonate bedrock. At slightly lower levels of correlation, the Ca : Sr

TABLE 1. Sector E linear correlation matrix. n = 0.289 at 1%. r

= 0.8 r = 0.7

Ca

Si

Fe P Zn Mg

Si

P

Fe

Zn

r

= 0.6

r

DC Zn

Mg

78, r

= 0.5

GEOCHEMISTRY OF SECTORS BAND F In Tables 2 and 3, correlation analyses characterize bulk geochemical compositon of unmodified sandy silts (sector B, 5.5 mean phi-size) and modi-

TABLE 2. Sector B linear correlation matrix. n = 0.708 at 1%. r

= 0.9

P Si OC Cd

Si Ti

Ti Na OC Na P

Mg

K Bc JIg Ti S Cu Cu Si Mg Ti Zn S Cu

CdNa Pb Cd NaK OC Ti

OC Zn Ti Cd Si Mg Si Zn S Mg Ti Cd

S Pb PbP Na

S S Hg OC Cu

Hg OC Cu

Cr

P Fe

Cu

Hg

Hg

CuOC

Ni Pb

Zn Cd

Zn

Pb Cd

Silt Pb P Fe

Si Al Mg OC Hg K S Cu

HgS Zn Pb

Silt Mg Ni Sand Cu

Pb

r = 0.7

HgMn

Mn Pb DC

Ca

= 11, r

S Zn

Na

DC Pb Al Mn Mg Silt

r = 0.8

Ca Fe K Mg Mn

Sr

S Si

=

association reflects the composition of the carbonate fraction and there are associations between Fe, Mn, Pb, O.C., P, and Al (in which Al reflects a range of alumino-silicate compositions). At lower correlations Ca and Na are probably associated with the feldspar composition, and Mg (in montmorillonite clay minerals) becomes associated with the silt-size fraction (Thomas 1972, Sly 1983a). Ni and Cu are probably associated with Fe coatings (Cronan and Thomas 1972). Coarse sediments forming the Kingston basin deposits are compositionally different from those previously studied at the western end of Lake Ontario (Sly 1983a). Ordovician bedrock exposed in eastern Lake Ontario is not dolomitic and the low Mg content of derived sediments has a poor correlation with Ca (r = 0.45). Although the Ti content of sediments from both the east and west ends of the lake are similar, Ti in the coarse Kingston basin sediments has only a weak correlation with Mg, Fe, and P; rutile, therefore, may be a more important component in this suite of heavy minerals.

Si Ca Ti

368

P. G. SLY TABLE 3. Sector F linear correlation matrix. n = 37, r = 0.414 at 1%. r = 0.9 Ca Fe K Mg Mn P Si OC Cd Cr Cu Hg Ni Pb Zn

P Al

Fe

Hg

r = 0.8 Mn Si P Fe MnCd Si Mg P S P Ni

r = 0.7 Sr Si Cd Mg Fe P Cd Zn ZnMg Cd Fe Cu Zn Si Pb Mn Fe Si S

OC Cr Zn Pb

Cd CdPMn

fied sandy silts (sector F, 3.8 mean phi-size). Sector F sediments contain elemental associations common to both the sands (sector E) and unmodified silts (sector B) as implied by their sedimentological characteristics. For example, Ca and Sr relationships and Fe, P, and Mn relationships remain dominant in sector F but are absent in sector B. On the other hand, Hg and S are closely associated in sediments of both sector Band F but remain of little significance in sector E sediments. Because sector F materials are of mixed population it is easier to use sector B materials as a guide to the characteristics of modern silt accumulation in the basin, even though represented by a total of only 11 samples. In Table 2, Ca (as I.C.) is loosely associated with Sand Zn, but with nothing else. Iron shows no dominant association; K is related to Al and Mg and antithetically to Si and Na, which strongly implies an illite type clay mineral composition (typical of reworked glacial and glaciolacustrine sediments; Thomas et al. 1972) and this is further supported by the Ti relationship (Thomas 1972). Mn is related to P and Hg, and Si is related negatively to almost everything except Na. Organic C is strongly associated with Hg and S, slightly less so with Cu, Mg, Ti, and Zn, and also with Pb, Cd, and K. Strong associations occur between Cu, Hg, and O.C., and Pb, Zn, and Cd. All of which implies that there is a complex relationship between clays

r = 0.6 Zn Al S Ti OC Cu Si Pb Al

r = 0.5 Pb I( Ni Fe Mn Sand Hg Clay P Cd Zn OC Na Pb Nil( NiAll(

Pb Zn Mn Na Pb AIK Cu

Cu Mg Zn MgNi

Zn Hg Mg Cd Cu Zn Pb P Mn Ni Si Si Cu Ni Fe

OC Pb Na Zn AI K Pb P Fe Mn Cd Fe Cu Mg Hg Mg Hg OC

and organic particles and that O.C. appears to be most competitive for associations with Hg, S, Cu, Pb, and Cd. GEOCHEMISTRY OF SECTOR C The correlations presented in Table 4 imply a series of complex relationships between I.C., O.C., sulphides, clays, and hydrated Fe and Mn oxides, in which there are interference and preferential associations with, and between, a number of heavy metals. Most Hg likely occurs as sulphide or organo-sulphide complexes, and Zn and Pb are associated with organic complexes. Ca (as I.C.) is strongly associated with Hg and less so with S, Zn, O.C., P, and Pb in the silt-size fraction, and this suggests the probability of carbonate coprecipitation for some heavy metals as well as the presence of mixed I.C.:O.C. particles in which heavy metals are primarily bound to the organics. This is further supported by Eadie and Robertson (1976), who demonstrated that calcium carbonate can exceed the saturation of the Lake Ontario hypolimnion by as much as five times during summer periods. The presence of "whiting" (CaC03 crystals) in the waters of eastern Lake Ontario and the Kingston basin also has been confirmed by satellite imagery (Robertson and Scavia 1984). The Fe associations with Ti and Mg, and K:Mg

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY

369

TABLE 4. Sector C linear correlation matrix. n = 73, r = 0.3 at 1%. r = 0.9 Ca Fe K Mg Mn P Si

Ti Al

r = 0.8 Hg Mg Fe Si Ti POC OCMnHg Mg

r = 0.7

r = 0.6

Silt SiOC Ti Mg K ZnHg Zn Fe Sand 'Ii Bc Silt Fe Si Silt Zn Sr Zn

Si S Zn OC Sand Sand K Mn Fe Sand Al Silt Fe Si Pb Silt S fIg Ca Na P Zn

r = 0.5 P Pb P Al Silt Zn S Hg SOC Silt Na Pb Cd Cu Sand Cr Sr Si Ca Fe Cd Ti Pb Cu Mn

OC Cd Cr Cu

Hg Zn P Mn

Hg Ni Pb Zn

OC Zn Ca P

Silt Mn

Pb Si Sand S

SMgS Hg P Cu Mn Pb Zn Cu Mn Sand Hg Cd Cr Mn Silt Si Cu Cd Sr Fe

OCHg

Zn CuMn P Pb Cd

Hg OC P Cu Sr Silt Ca Sand Si

Mn Si Ca Cd Cr Fe

relationships imply mixed clay mineral/hydrous Fe-oxide binding and Fe also appears to be complexed with organics. Mn is associated with P and O.C. and can provide sorption sites for Zn and Hg in the silt-size range. Pb, Cd, and Cu are likely to share preferential sorption sites on both hydrous Fe oxides and humics. VARIMAX SUMMARY Summarized data from a series of separate varimax matrix analyses (by skewness/kurtosis sector) are presented in Table 5. An analysis of all the Kingston basin sample data is expressed with 10 factors, accounting for 94.1 % of the problem variance but, for simplicity, only 6 factors have been used to characterize each of the sector sub-sets of data (in which they account for about 80 to 93070 of the problem variance). This presentation simplifies the information carried in Tables 1 to 4 and provides an opportunity to highlight certain characteristics of the data. In the total sample analysis, Factor 1 defines the contrasting relationship between feldspars and quartz (Na, Si) and the association between a.c. and many heavy metals. Factor 2 is strongly characteristic of clay minerals, and Factor 3 accounts for Fe, P, and Mn relationships which are largely dependent upon Eh and pH conditions

Pb Sand Ca Cu Cd Ti OC Sr OC Pb Sr

at the sediment/water interface. Factor 4 defines a close association between Ca, Sr, and inorganic carbon (as carbonate) and Hg, and suggests that Mg : carbonate co-precipitation may occur as proposed by St. John (1972) in Kalamalka Lake, B.C. Although the mean particle size of sector C sediment at Kingston (7.3 phi) is not very different from the sector C sediment at Niagara (7.5 phi), the geochemical relationships between sector B/C sediments vary markedly at the two sites. In western Lake Ontario (Sly 1983a) there was a pronounced change in composition between the sector Band C sediments which was interpreted as characterizing the break between the distal limit of bottomset beds derived from the Niagara River and the fine muds which were deposited under the separate influence of mid-lake processes. At Kingston, the change in elemental compositions is nowhere so pronounced, despite a comparable increase of a.c. and clay mineral content in deep water sediments. SUMMARY OF SEDIMENT CHARACTERISTICS The bulk geochemistry and distribution patterns indicate that the following conditions influence

370

P. G. SLY

TABLE 5. Varimax matrix summary. Skew/Kurt Sector E

Skew/Kurt Sector B

H£ ~nOC Pb Cu Na Si

OC ZN Pb P Fe Silt MnHg

Ca IC Zn Cu.!'b Cd Hg OC Sr Si Mg Ti

Zn Pb Cd PMnCu SiHg

PbMnP OC Zn Ni Hg Cd Cu

Cu OC Zn Hg Cd Al Pb K Ni Mg

2

AIK Clay Mg

Ca IC Si Na Sr Mg

Na Si Fe KMgHg OC Clay

Al K OC Ti !:!g gay Mn Fe

I( Al 'Ii Mg Fe Si

Fe P Si Mg Ni Na Pb Mn

Fe P Mn

Ni Cr Cu Cd Clay Na

MnP Clay

Silt Mg Na Si

Ca IcHg

3

Sr Ca MnlC

CalC Sr Hg

Al K Clay IC Cu

All(

Ti Mg

Co Ni

Fe P

Sr Silt

Co Hg Sr

Cr Ni

Factor

4

All Kingston Samples

5 Cr Ni

6 Co Sr

7

Skew/Kurt Sector F

Ca Ic Sr Clay

CuMn

Cr Ni

Skew/Kurt Sector C

Silt Si Na Sr Si

Cr Cd

Skew/Kurt Sector G

Silt Ti CoMg

Clay

Clay K Al

Silt Na

Na

Co

Cr Ti Cd

Co Sr

Na Sr

3.78¢

7.31¢

Ti Mg AIK

8

Na

9

Mn Sr

10

Cd Ni

Mean Size % Problem Variance

1.87¢

94.1

80.1

5.55¢

93.1

sediment characteristics and accumulation in the Kingston basin. 1. Many of the sands and sandy silts in the basin are of mixed population, and reflect reworking of relict deposits under the influence of fluctuating water levels.

84.0

8.8

5.55¢

88.8

2. Modern silts and silty clays are thin and restricted to areas of bathymetric depression, and little silt has been incorporated into the coarser sand and gravel deposits (thus preserving their value as spawning substrates). The main area of modern fine sediment accumulation (sector C type material) occurs in the St. Lawrence trough. Little of

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY the fine sediment deposited outside the St. Lawrence trough forms permanent accumulations, because of seasonal or periodic reworking. The bulk geochemistry of 2 cm subsamples from these areas, however, may be a better indicator of existing lake conditions than samples from the St. Lawrence trough, in which intermittent removal does not occur and in which mixing (largely biological) can reduce surficial concentrations of contaminant materials. 3. Most heavy metal concentrations are similar to lakewide mean values reported by Thomas (1975), although elevated values are associated with samples having a high O.C. content. This is particularly true for Hg which is strongly associated with both O.C. and S in the sediments. Mercury is believed to be bound to hydrous Fe-oxides and directly with organic particles. It is associated with sulphides and organo-sulphides as a result of diagenetic processes (Thomas 1972) and bacterial degradation at the sediment/water interface (Vanderpost and Dutka 1971). It also appears to have an association with carbonates. Since there are no significant point-source inputs to the Kingston basin, elemental concentrations are expected to reflect lake-wide conditions,local changes in source rock composition or the effects of bioaccumulation (or combinations). 4. Sly and Thomas (1974) reported the presence of a pitted surface on glaciolacustrine clay from the northwest of the Kingston study area and suggested that it had been formed as Fe-Mn nodule casts. This explanation seems in keeping with what is now known about water level changes in the basin (Sly and Prior 1984). The nodules probably formed at an early date (9 to 10,000 years B.P.) when water depths would have been comparable to the modern Brothers Island site, nearby, (Sly and Thomas 1974). As water levels increased, Eh/ pH conditions likely changed at the site and the nodules crumbled and disappeared as the Mn was preferentially dissolved (Burns and Nriagu 1976). The only part of the study area in which evidence of related modern chemical processes occurs is in sub-basin III, where high concentrations of Fe and P appear to be geographically related to the zone of Fe/Mn coatings and precipitation along the north shore of Lake Ontario (described by Cronan and Thomas 1972). Sub-basin III probably marks the most easterly penetration of seasonal mainlake up-welling into the Kingston basin. COMPARISON OF NIAGARA AND KINGSTON SEDIMENTS

In the following discussion, modern sediments are represented by sectors A-C (sand, silt, and silty

371

clay) and modified sediments by sectors E-G (lag deposits, reworked glacial till, and glaciolacustrine clay). In Table 6, selected major and trace element concentrations are expressed as the ratio Niagara:Kingston, by skewness/kurtosis sector. In sector A (only 5 samples at Kingston), the concentrations of most elements, with the exceptions of Mg, I.C., Si, and Hg, are slightly greater at Kingston than at Niagara. At Niagara, the higher content of Si reflects the fact that sector A sediment contains a greater percentage of sand. The high concentration of Hg is directly associated with the contaminant load of the Niagara River. In sector B, the Niagara:Kingston ratios indicate that concentrations of Ca, Mg, S, and I.C. are all higher at Niagara; these reflect a slightly greater contribution of local bedrock as a source of sedimentary material. Concentrations of Cr, Cu, Hg, and Zn are also greater at Niagara and, although some of the difference may be accounted for by the higher silt content of Niagara sediments, most is likely the result of local contaminant loading from the Niagara River. Concentrations of these elements at Niagara are significantly above lakewide means (Sly, 1983a). Cobalt is noticeably higher at Kingston (in all sectors), and indicates a difference in the composition of (source) glacial tills at the east and west ends of the Lake Ontario basin. In sector C, as in sector B, many of the differences in major and trace element compositions are accountable on the basis of different contents of clay and silt in the fine fractions of Niagara and Kingston sediments. Large differences in the content of Hg, Mn, and Co, however, are clearly anomalous. The differences in content of Hg and Co are caused by the same factors which have influenced content of sector B materials. Although Mn values are higher at Niagara than at Kingston, Niagara values are below the lakewide mean (Sly 1983a). Therefore, this difference is best explained by very low concentrations at Kingston (due to differences in local Eh/pH conditions). There are no sector D sediments within the Niagara study area, and at Kingston, almost certainly, none of the sector D materials are of modern origin. In sector E sediments, ratios of Ca, Mg, and I.C. at Niagara, again, reflect the significance of local source rock. The ratio differences, however, are greater than in sector A (mean size comparable) and indicate that local bedrock at Niagara is noticeably more important than at Kingston as a source of coarse materials (lag deposits). The silt

~

TABLE 6. Niagara: Kingston elemental ratios.

......

N

Sector AI

Cu

Hg

Sr

Zn

0.8 0.5

0.5

1.1

0.3

1.0 0.6 0.6 0.3

0.5

1.9 0.4 0.4 0.5

0.7

-

1.1

0.8

0.7

1.9

1.0

1.0

1.6 0.9

1.2 0.3

1.1

5.4 0.7

0.8

0.9

1.3

-

0.8

1.6 0.7

1.2

1.2 0.4

1.3

4.8

1.0

1.1

0.8

1.4

-

0.7

1.0

1.1

0.7

0.8

1.0 6.8 0.7

0.8

0.7

1.8 0.2

1.1

2.1

0.6

0.8

0.8

1.0 0.7

B

0.9

1.4 0.9 0.9

1.3

0.8

(j

'<

Co

Na

0.7

~

IC

Mg Mn

0.8

a.

OC

K

P

0.8

C

1.1

1.0

1.2

1.0

1.1

1.9

1.1

1.0

1.2

1.1

0.9

1.2

E

0.8

1.2

0.7

0.8

1.7 0.5

0.7

0.8

0.3

1.0 2.1

2.5

Cd

Cr

0.1

Pb

~

<:

Si

Fe

Ni

Cl

S

Ca

A

Trace Elements

Carbon

Major Elements

~

0.4

Low levels of all trace metals except Hg, associated with 0 C High carbonates/sulphates associated with silt-size fraction Generally similar throughout lake, except Hg and Zn loading. Mn associated with clays.

~ F

0.8

1.5

0.4 0.8

1.2

0.3

0.7 0.5

1.3

1.1

3.2 0.4 0.4 0.1

1.2

0.7

8.2 0.4 0.6

0.6 0.8

0.4

1.1

1.6 0.4

~ rIJ

G

1.0 2.1

~ ;. Co

I>'

'<

'" S· :::J

::;

'" '"

0.8

~ ~ ;:

...a' ~ 0 (')

I>'

::;

!!l.

'" '"

'"S· :::J ::;

'"'"

0.9

1.5 0.6 0.7

t'"' ~ 0'" ~ ;: ~~ ... 3o 0 % ~ ... ::;::T

(')

(')

'<

... ...I>'

'" S'

:::J ::;

<11

'"

a

'" o='" (') ~.'"

e.1!l E,g '"

- ... ! .::;

(')

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:n:: ~

(')

0

~

"'" a :::J ::; '"...

1.0

1.4

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(j

~

t'"'

::TI>' ... (JQ

"'~ .'<

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0

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"'"

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"'" ..... (j

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::T dQ. ::s-

","<11

'" !!l. P.-

4.2

1.0 1.8

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'"...'" ;:

'"0~ ~ ... '"S· .c5• '"'" 8... c5 •

'"...

~.

8'" 8-

s·

'"~

!!l. ~

I>'

(JQ

... '"

I>'

1.4 0.5

0.3

(j 0 a'

~

e!. ~

I>'

'<

'" ::sdQ. ::s-

'"...

!!l. ~

::; (JQ

~

0 ::;

1.2 2.4 0.7 ~

0.8

0.8

1.4 0.1

~

~

~

~

I>'

'<

'" ::s-

dQ. ::s-

'"...

!!l. ~

I>'

(JQ

... I>'

I>'

-< ::T dQ. ::s<11

...

!!l. Z

JJ. ...

I>' I>'

~

...'" ! !!l.

(JQ

e!.

'"t:

~

...

t:

e!.

(')

0.6

0

::;

t: '<

2.3

...0

...'" ...

(')

0.7

<11

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1I!l I>'

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::;

~

0

::;

~

LAKE ONTARIO SEDIMENTOLOGY AND GEOCHEMISTRY

content of the mixed population sector E sediment' is also much higher at Niagara, and this is seen in the higher values of O.C., Cu, Hg, and Zn which are associated with this finer fraction. In sector F, the importance of local bedrock is further substantiated as a source of water lain sediment at Niagara, where I.C. values are double those of modern sector B sediment (mean size comparable). The addition of modern contaminants to sector F materials is well shown by the very high ratio difference of Hg values beween Kingston and Niagara sediments. In sector G, the bedrock influence is present, again, at Niagara. The contaminant influence of Cd, Zn, and, particularly, Hg, in the silt size fraction of these mixed population sediments is also well shown. On the other hand, Cr, Ni, and Pb are low at Niagara, reflecting the lower clay content of the sediments. The ratio of total element concentrations in sediments from the western and eastern ends of Lake Ontario in the fine sediments of sector C (generally in equilibrium with modern hydraulic conditions) indicate somewhat higher concentrations at Niagara; often at ratios that are comparable to the differences in the west/east lake water chemistry (Chau et al. 1970). However, total element ratios in coarse sediments (sector A) and in the mixed population sets (sectors E, F, and G) are not comparable to the differences observed in water chemistry. In these sediments, it is evident that regional differences in the composition of source material are of primary importance.

REFERENCES

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373

Eadie, B. J., and Robertson, A. 1976. An IFYGL carbon budget for Lake Ontario. J. Great Lakes Res. 2:307-323. Golterman, H. L., Sly, P. G., and Thomas, R. L. 1983. Study of the relationship between water quality and sediment transport. Technical papers in hydrology, #26, UNESCO, Paris. Hansbo, S. 1957. A new approach to the determination of the shear strength of clay by the fall-cone test. In Proc. Roy. Swedish Geotech. Inst. #14. Liberty, B. A. 1971. Palaeozoic geology of Wolfe Island, Bath, Sydenham and Gananoque map-areas Ontario. Geol. Surv. Can. paper 70-35. Robertson, A., and Scavia, D. 1984. North American Great Lakes. In Lakes and Reservoir Ecosystems, Ed. F. Taub, pp. 135-176. Vol. 23 Ecosystems of the World. New York: Elsevier Publ. Sandilands, R. G., and Sly, P. G. 1977. Data listings of surficial sediment samples from grid sampling studies on the Great Lakes (4 vols.). Unpublished Reports; Canada Centre for Inland Waters, Burlington, Ontario. Sangrey, D. R. 1970. Evidence of glacial readvance over soft layered sediments near Kingston, Ontario. Can. J. Earth Sci. 7:1331-1338. Sly, P. G. 1969a. Sedimentological studies in the Niagara area of Lake Ontario, and in the area immediately north of the Bruce Peninsula in Georgian Bay. In Proc. 12th Conf. Great Lakes Res., pp. 341-346. Internat. Assoc. Great Lakes Res. ____ . 1969b. Bottom sediment sampling. In Proc. 12th Conf. Great Lakes Res., pp. 883-898. Internat. Assoc. Great Lakes Res. ____ . 1970. Underwater photography in the Great Lakes-a report. In Proc. 13th Conf. Great lakes Res., pp. 282-296. Internat. Assoc. Grea Lakes Res. ____ . 1975. Statistical evaluation of recent sediment geochemical sampling. In Proc. 9th Internat. Sediment. Cong., Nice, Reprint. ____ . 1981. Equipment and techniques for offshore survey and site investigations. Can. Geotech. Jour. 18:230-249. ____ . 1983a. Sedimentology and geochemistry of recent sediments off the mouth of the Niagara River, Lake Ontario. J. Great Lakes Res.9:134-159. ____ . 1983. Recent sediment stratigraphy and geotechnical characteristics of foreset and bottomset beds of the Niagara Bar. J. Great Lakes Res. 9:224-233. ____ , and Prior, W. J. 1984. Late glacial and postglacial geology of Lake Ontario. Can. Jour. Earth Sci. 21 :802-821. ____ , and Thomas, R. L. 1974. Review of Geological research as it relates to an understanding of Great Lakes limnology. J. Fish. Res. Board Can. 31 :795-825. ____ , Thomas, R. L., and Pelletier, B. R. 1982. Comparison of sediment energy-texture relationships

374

P. G. SLY

in marine and lacustrine environments. Hydrobiologia 91/92:71-84. ____ , Thomas, R. L., and Pelletier, B. R. 1983. Interpretation of moment measures derived from water-lain sediments. Sedimentol. 30:219-233. Sl. John, B. 1972. Preliminary report on the limnology of the mainstem Okanagan lakes. Task 121. Unpublished report, Canada Centre for Inland Waters, Burlington, Ontario. Thomas, R. L. 1972. The distribution of mercury in the sediments of Lake Ontario. Can. J. Earth Sci. 9:636-651. _ _ _ _ . 1975. Sediment characteristics. In Interna-

tional Working Group on the Abatement and Control ofPollution from Dredging Activities. Report to the Governments of Canada and the United States. Ottawa.

____ , Kemp, A. L. W., and Lewis, C. F. M. 1972. Distribution, composition and characteristics of the surficial sediments of Lake Ontario. J. Sediment. Petrol. 41 :66-84. ____ , Kemp, A. L. W., and Lewis, C. F. M. 1973. The surficial sediments of Lake Huron. Can. J. Earth Sci. 10:266-271. Vanderpost, J. M., and Dutka, B. J. 1971. Bacteriological study of Kingston Basin sediments. In Proc. 14th Conj. Great Lakes Res., pp. 137-156. Internal. Assoc. Great Lakes Res. Warwick, W. F., 1980. Palaeolimnology of the Bay of Quinte, Lake Ontario: 2800 years of cultural influence. Can. Bull. Fish. Aquat. Sci. 206.