R.D. Knight, J.M. Bednarski, E. Grunsky, H.A.J. Russell...... using a portable X-ray fluorescence...
1
GEOLOGICAL SURVEY OF CANADA COMMISSION GÉOLOGIQUE DU CANADA Groundwater Geoscience Program - Geological Survey of Canada Portable XRF chemostratigraphy of a paleo-glacial foreland basin, the Nanaimo Lowalands, Vancouver Island C onclusions A relatively thick and extensive succession of late Pleistocene proglacial, glacial and interstadial sediments occurs in the Strait of Geor gia in British Columbia (and Puget Sound in Washington). Strata include the Dashwood and Vashon tills, the Cowichan Head, Quadra sand, and Capilano sediments. All of these units form either regional aquifers, or aquitards, hence understanding the spatial heterogeneity and lithochemistry are of high interest due to increasing groundwater issues in this area. Numerous studies have reviewed the lithostratigraphy, depositional environments and age relationship of these units; however, to-date there has been no systematic geochemical characterization. To resolve this knowledge gap the Geological Survey of Canada in collaboration with the Regional District of Nanaimo, British Columbia, has completed a chemostratigraphic study of 2 boreholes (~130 m deep) approximately 20 km apart, using a portable X-ray fluorescence spectrometer and multivariate statistical methods. Results from the 234 analyses of the <63 µm (silt + clay) size fraction identify 15 elements that document the stratigraphic chemical variability. In the Dashwood till changes in both single element concentrations and multi-element associations indicate local variability within these sediments. The overlying lower Cowichan Head Formation displays similar elemental concentration trends as the underlying Dashwood till and is attributed to sediments sourced from Vancouver Island. In contrast, the upper Cowichan Head Formation and overlying Quadra sand have a geochemical signature (e.g. a relative increase in Sr concentration) reflecting a change in provenance to the Coast Mountains. The overlying Vashon Drift and Capilano Sediments can be differentiated from each other and the underlying Quadra Sand, by variations in the relative enrichment/depletion of the elements Ba, Fe, and Mg. To our knowledge these results are the first systematic geochemical characterization of late Pleistocene succession in the Nanaimo Lowlands. Comparing the score and loading plots identifies co-relationships between elements and positive and negative relationships of the elements. The relative change of these values and their trends display the behavior of the weighted grouping of elements (i.e. a change in the trend displays a change in the relationship of elements at that depth). Use of principal components can reveal relationships between elements that are co-related and most likely represent a variation in lithology and provenance of the sediments. M ethods I ntroduction S implified S tratigraphy P rincipal C omponent A nalysis: S cores and L oading P rincipal C omponent A nalysis L ocation R.D. Knight, J.M. Bednarski, E. Grunsky, H.A.J. Russell 1) 2) 3) 4) 5) 6) 7) PCA Scores PCA Loading Knight, R.D., Kjarsgaard, B.A., Plourde, A.P., and Moroz, M., 2013. Portable XRF spectrometry of reference materials with respect to precision, accuracy, instrument drift, dwell time optimization, and calibration; Geological Survey of Canada, Open File 7358 doi:10.4095/292370 D 5 cm D 5 cm D 5 cm D 5 cm D 5 cm D 5 cm D 5 cm D 5 cm D D 5 cm 5 cm D 5 cm D 5 cm D 5 cm D 5 cm S edimentary F acies + E nvironment Spider Cochrane Sample at ~1 meter intervals and above and below visible geological contacts Dry and disaggregate sample Sieve to <63 µm (silt + clay) Place sample in 23 mm diameter plastic vials, to a height of 30 mm, to obtain sufficient density and “infinite thickness” Seal vials with 4 µm thick Chemplex Prolene Analyzed sample using Thermo Scientific, Niton XL3t GOLDD spectrometer in Soil mode with a 60 second dwell time per filter Insert a Teflon and silica blank, plus multiple CRM’s, at the beginning and end of every session and after every10 samples 0 50 km Cochrane Spider Kilometres 0 200 400 A A −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr Dashwood Drift Spider −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr Cowichan Head Cochrane + Spider Lower Upper −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr Quadra Sand Cochrane + Spider −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr Vashon Drift Cochrane + Spider −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr CD W1 CDW2 CD W3 CDW4 CD W5 CH1 CH2 CP QD SD W1 SDW2 SD W3 SDW4 SD W5 VA Cochrane Dashwood drift 1 Cochrane Dashwood drift 2 Cochrane Dashwood drift 3 Cochrane Dashwood drift 4 Cochrane Dashwood drift 5 Cowichan Head Fm. Cowichan Head Fm. Capilano sediments Quadra sand Spider Dashwood drift 1 Spider Dashwood drift 2 Spider Dashwood drift 3 Spider Dashwood drift 4 Spider Dashwood drift 5 Vashon drift CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA Capilano Sediments Cochrane + Spider 0.00 0.05 0.10 −0.20 −0.15 −0.10 −0.05 −0.05 −0.10 0.00 0.05 0.10 0.15 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 meters PC1 PC2 PC3 PC1 PC2 PC3 Dashwood Drift Quadra Sand Unit 1 2 3 4 5 lower upper Vashon Drift Capilano Sediment Cowichan Head Formation PC Scores Simplified Stratigraphy Gravel/pebbles Shells Organic/roots Mud Silt Fine sand Medium sand Coarse sand Diamicton No recovery - 100 - 110 -80 - 60 - 50 - 70 -90 -40 -20 - 30 - 10 0 −0.4 −0.2 0.0 0.2 0.4 PC Scores meters - 120 - 100 - 110 -80 - 60 - 50 - 70 -90 -40 -20 - 30 - 10 0 Simplified Stratigraphy Gravel/pebbles Shells Organic/roots Mud Silt Fine sand Medium sand Coarse sand Diamicton No recovery Quadra Sand Vashon Drift Capilano Sediment Cowichan Head Formation PC1 PC2 Dashwood Drift Unit 1 2 3 4 5 −0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 PC 1 PC 2 As Ba Ca Cr Cu Fe K Mn Rb Sr Ti V Zn Zr Dashwood Drift Cochrane CDW1 CDW2 CDW3 CDW4 CDW5 CH1 CH2 CP QD SDW1 SDW2 SDW3 SDW4 SDW5 VA Principal component loading and scores for PC 1 and PC 2. Elements of similar relationship are plotted as a positive correlation while elements with an opposite relationship plot as a negative correlation. For the Spider borehole Dashwood drift populations display less clumping than Cochrane and occupy an area more towards the +PC 2 zone. These sediments also display a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island. Most units of the Dashwood drift for Cochrane display clumping populations suggesting localized variability in provenance. The populations occupy an area of both - PC1 and PC 2. These sediments display a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island. Lower Cowichan Head Fm sediment display element similarities with the underlying Daswood Drift diamictons and marine sediments. Upper Cowichan Head Fm. sediments display elemental similarites with the overlying Quadra sand. Quadra sand displays elemental associations related to granitic provenance of the Coast Mountains. Vashon drift displays elemental associations similar to unit two of the Spider and Cochrane Dashwood drift . Capilano sediments displays similarites in elemental associations to the lower Cowichan Head Fm. Cochrane Centered log ratio transformed geochemical data for PC1 and PC2 plotted adjacent to the Cochrane borehole stratigraphic section. Spider Centered log ratio transformed geochemical data for PC1, PC2 and PC3 plotted adjacent to the Spider borehole stratigraphic section. -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -120 -100 -80 -60 -40 -20 -120 -100 -80 -60 -40 -20 0 0 5 10 15 20 25 0 200 400 600 800 20000 40000 60000 0 40 80 120 160 0 50 100 150 200 250 20000 80000 140000 4000 9000 14000 0 20 40 60 80 0 1000 2000 3000 4000 0 200 400 600 2000 6000 10000 0 100 200 300 400 500 20 70 120 As Ba Ca Cr Cu Fe K Mn Rb S Sr Ti V Zn ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 0 1000 2000 LOD 1 Unit 2 3 4 5 0 500 1000 1500 2000 100 150 200 ppm -120 -100 -80 -60 -40 -20 0 ppm -120 -100 -80 -60 Zr meters Clay (% <4um) Sand (% <2mm) Silt (% 63-4um) 0 20 40 60 80 100 0 20 40 60 80 100 0 10 20 30 40 50 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -100 -110 -80 -60 -50 -70 -90 -40 -20 -30 -10 0 LOD LOD LOD LOD ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 1 Unit 2 3 4 5 meters -120 -100 -80 -60 -40 -20 0 0 5 10 15 -120 -100 -80 -60 -40 -20 0 0 200 400 600 -120 -100 -80 -60 -40 -20 0 10000 30000 50000 -80 -60 -40 -20 0 10000 50000 90000 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 0 500 1000 1500 2000 -120 -100 -80 -60 -40 -20 0 10 20 30 40 50 -120 -100 -80 -60 -40 -20 0 0 0 200 400 600 500 1000 1500 2000 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 0 4000 8000 12000 -120 -100 -80 -60 -40 -20 0 0 100 200 300 400 500 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 -120 -100 -80 -60 -40 -20 0 100 300 500 700 -120 -100 -80 -60 -40 -20 0 As Ba Ca Cu Cr Fe K Mn Rb S Sr Ti V Zn Zr -120 -100 -80 -60 -40 -20 0 0 0 30 60 90 120 150 20 40 60 80 100 2000 6000 10000 14000 Clay (% <4um) Sand (% <2mm) Silt (% 63-4um) 0 20 40 60 80 100 0 20 40 60 80 100 0 10 20 30 40 50 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -80 -60 -40 -20 0 -120 -100 -110 -80 -60 -50 -70 -90 -40 -20 -30 -10 0 meters - 100 - 110 -80 - 60 - 50 - 70 -90 -40 -20 - 30 - 10 0 meters - 120 - 100 - 110 -80 - 60 - 50 - 70 -90 -40 -20 - 30 - 10 0 Borehole diameter: Depth Drilled: Easting: 382 789m Project: Groundwater Assessment Borehole: Spider Northing: 5 469 236m Location: Quacilum, BC Date Logged : March 2013 Datum: NAD83 UTM Zone: 10 pXRF: Size Fraction: Vial Window Material: Original Material: Niton XL3t GOLDD, 50-kV Cygnet X-ray tube Dwell Time: 60 seconds per High, Main, and Low filter Mode Type: Soil Mode, Compton normalization <0.063 mm 4 micron SpectroCertified Mylar polyester Freeze-dried, disaggregated, seived Date Drilled: Study Area: Nanaimo Lowlands Method: 155 mm 117.43 m December 2012 Sonic Simplified Stratigraphy Gravel/pebbles Shells Organic/roots Hydrostratigraphic Units Quadra sands: sand CowichanHead Fm: silt, gravel, sand, peat Dashwood drift: till clay/stony clay with marine shells Vashon drift: till lenses, gravel, sand Capilano sediments: deltaic deposits Mud Silt Fine sand Medium sand Coarse sand Diamicton Borehole diameter: Depth Drilled: Easting: 379 107m Project: Groundwater Assessment Borehole: Cochrane Northing: 5 472 671m Location: Quacilum, BC Date Logged : March 2013 Datum: NAD83 UTM Zone: 10 pXRF: Size Fraction: Vial Window Material: Original Material: Niton XL3t GOLDD, 50-kV Cygnet X-ray tube Dwell Time: 60 seconds per High, Main, and Low filter Mode Type: Soil Mode, Compton normalization <0.063 mm 4 micron SpectroCertified Mylar polyester Freeze-dried, disaggregated, seived Date Drilled: Study Area: Nanaimo Lowlands Method: 155 mm 129.23 m December 2012 Sonic Gravel/pebbles Shells Organic/roots Mud Silt Fine sand Medium sand Coarse sand No recovery No recovery Simplified Stratigraphy Gravel/pebbles Shells Organic/roots Hydrostratigraphic Units Quadra sands: sand CowichanHead Fm: silt, gravel, sand, peat Dashwood drift: till clay/stony clay with marine shells Vashon drift: till lenses, gravel, sand Capilano sediments: deltaic deposits Mud Silt Fine sand Medium sand Coarse sand Diamicton No recovery Dashwood Drift Diamicton overlain by mud and gravel.The gravel is a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island. Depositional environment: glacial, glaciofluvial, ice-contact and glaciomarine to marine The sedments were deposited during the early Wisconsin penultimate glaciation. Cowichan Head Fm. Upper member of sandy silt and gravel from volcanic and sedimentary rocks, commonly with reddish oxidized hues rich in fossil plant remains is interpreted asstuarine and fluvial environments. Cowichan Head Fm. Lower member of clayey silt and sand with marine shells is interpreted as glaciomarine Quadra Sand Horizontally, and cross-stratified, sand composed of quartz, feldspar, and lithic fragments of granitic provenance.The sand becomes younger to the south away from its source in the Coast Mountains. Lower parts of the Quadra Sand contains wood and peat lenses is interpreted to be subaerially outwash deposited in proglacial environment on floodplains and locally as deltaic deposits. Vashon Drift Sandy diamicton, with local mud rich, and sand and gravel facies is interpreted as glacial till formed in a variety of ice-contact depositional (landform) settings including esker, deltas, and fans.The lithologic composition reflects the Coast Mountains, Georgia Depression, and reworking of the Quadra Sand. Capilano Sediment The sediment consists of sand and gravel with minor diamicton. It is interpreted as a deglacial succession of coarse glaciofluvial outwash that becomes more distal upwards. 1 2 3 3 2 4 5 6 4 5 6 7 8 9 10 11 12 13 14 7 8 9 1 10 11 12 13 14 Data obtained by pXRF spectrometry can be plotted and compared with the visual stratigraphic sediment descriptions and laboratory grain size analyses. An upwards increase in silt content of the Dashwood Drift is reflected in an upwards increase in concentration of many elements such as Ca, Cr, Cu, Fe etc as seen in the Spider borehole. The Cowichan Head Fm. is expanded in the Spider borehole where the lower unit is comparableto the Dashwood Drift and the upper unit is comparable to the overlying Quadra sand. The Quadra sand displays decrease in silt and clay content compared to other sediments and displays an increase in Sr, and a decrease in Cr, Cu and Ti. The Vashon Drift and Capilano Sediments can be differentiated from each other, and the underlying Quadra Sand, by variations in the concentration of elements such as Ba, Fe, and Mn. B orehole C hemo- S tratigraphy + G rain S ize D ata To our knowledge these results are the first systematic geochemical characterization of late Pleistocene succession in the Nanaimo Lowlands. The Cochrane and Spider borehole data demonstrates that pXRF geochemistry is valuable in differentiating stratigraphic units and can provide insight into the provenance of these sediments. Soil Mode Soil Mode Cochrane Spider
Transcript of R.D. Knight, J.M. Bednarski, E. Grunsky, H.A.J. Russell...... using a portable X-ray fluorescence...
GEOLOGICAL SURVEY OF CANADA COMMISSION GÉOLOGIQUE DU CANADA Groundwater Geoscience Program - Geological Survey of Canada
Portable XRF chemostratigraphy of a paleo-glacial foreland basin, the Nanaimo Lowalands, Vancouver Island
Conclusions
A relatively thick and extensive succession of late Pleistocene proglacial, glacial and interstadial sediments occurs in the Strait of Geor gia in British Columbia (and Puget Sound in Washington). Strata include the Dashwood and Vashon tills, the Cowichan Head, Quadra sand, and Capilano sediments. All of these units form either regional aquifers, or aquitards, hence understanding the spatial heterogeneity and lithochemistry are of high interest due to increasing groundwater issues in this area. Numerous studies have reviewed the lithostratigraphy, depositional environments and age relationship of these units; however, to-date there has been no systematic geochemical characterization. To resolve this knowledge gap the Geological Survey of Canada in collaboration with the Regional District of Nanaimo, British Columbia, has completed a chemostratigraphic study of 2 boreholes (~130 m deep) approximately 20 km apart, using a portable X-ray fluorescence spectrometer and multivariate statistical methods.
Results from the 234 analyses of the <63 µm (silt + clay) size fraction identify 15 elements that document the stratigraphic chemical variability. In the Dashwood till changes in both single element concentrations and multi-element associations indicate local variability within these sediments. The overlying lower Cowichan Head Formation displays similar elemental concentration trends as the underlying Dashwood till and is attributed to sediments sourced from Vancouver Island. In contrast, the upper Cowichan Head Formation and overlying Quadra sand have a geochemical signature (e.g. a relative increase in Sr concentration) reflecting a change in provenance to the Coast Mountains. The overlying Vashon Drift and Capilano Sediments can be differentiated from each other and the underlying Quadra Sand, by variations in the relative enrichment/depletion of the elements Ba, Fe, and Mg. To our knowledge these results are the first systematic geochemical characterization of late Pleistocene succession in the Nanaimo Lowlands.
Comparing the score and loading plots identifies co-relationships between elements and positive and negative relationships of the elements. The relative change of these values and their trends display the behavior of the weighted grouping of elements (i.e. a change in the trend displays a change in the relationship of elements at that depth). Use of principal components can reveal relationships between elements that are co-related and most likely represent a variation in lithology and provenance of the sediments.
MethodsIntroduction
Simpli�ed Stratigraphy
Principal Component Analysis: Scores and Loading
Principal Component Analysis
Location
R.D. Knight, J.M. Bednarski, E. Grunsky, H.A.J. Russell
1)
2)3)4)5)6)
7)
PCA Scores
PCA Loading
Knight, R.D., Kjarsgaard, B.A., Plourde, A.P., and Moroz, M., 2013. Portable XRF spectrometry of reference materials with respect to precision, accuracy, instrument drift, dwell time optimization, and calibration; Geological Survey of Canada, Open File 7358 doi:10.4095/292370
D
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Sedimentary Facies + Environment
Spider
Cochrane
Cochrane
Sample at ~1 meter intervals and above and below visible geological contacts
Dry and disaggregate sample Sieve to <63 µm (silt + clay) Place sample in 23 mm diameter plastic vials, to a height of 30 mm, to obtain sufficient density and “infinite thickness”
Seal vials with 4 µm thick Chemplex Prolene Analyzed sample using Thermo Scientific, Niton XL3t GOLDD spectrometer in Soil mode with a 60 second dwell time per filter
Insert a Teflon and silica blank, plus multiple CRM’s, at the beginning and end of every session and after every10 samples
0 50 km
CochraneSpider
Kilometres
0 200 400
A
A
−0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4
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PC 1
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CrCu
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Dashwood DriftSpider
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Cowichan HeadCochrane + Spider
Lower
Upper
−0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4
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As
Ba
Ca
CrCu
Fe
K
Mn
Rb
SrTi
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Zn
Zr
Quadra SandCochrane + Spider
−0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4
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PC 1
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Ba
Ca
CrCu
Fe
K
Mn
Rb
SrTi
V
Zn
Zr
Vashon DriftCochrane + Spider
−0.7 −0.6 −0.5 −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4
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PC 1
PC
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Ba
Ca
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Fe
K
Mn
Rb
SrTi
V
Zn
Zr
CDW1CDW2CDW3CDW4CDW5
CH1CH2
CP
QD
SDW1SDW2SDW3SDW4SDW5
VA
Cochrane Dashwood drift 1Cochrane Dashwood drift 2Cochrane Dashwood drift 3Cochrane Dashwood drift 4Cochrane Dashwood drift 5
Cowichan Head Fm.Cowichan Head Fm.
Capilano sediments
Quadra sand
Spider Dashwood drift 1Spider Dashwood drift 2Spider Dashwood drift 3Spider Dashwood drift 4Spider Dashwood drift 5
Vashon drift
�
CDW1CDW2CDW3CDW4CDW5
CH1CH2
CP
QD
SDW1SDW2SDW3SDW4SDW5
VA
CDW1CDW2CDW3CDW4CDW5
CH1CH2
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QD
SDW1SDW2SDW3SDW4SDW5
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CDW1CDW2CDW3CDW4CDW5
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CP
QD
SDW1SDW2SDW3SDW4SDW5
VA
CDW1CDW2CDW3CDW4CDW5
CH1CH2
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QD
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VA
CDW1CDW2CDW3CDW4CDW5
CH1CH2
CP
QD
SDW1SDW2SDW3SDW4SDW5
VA
Capilano SedimentsCochrane + Spider
0.00 0.05 0.10−0.20 −0.15 −0.10 −0.05
−0.05−0.10 0.00 0.05 0.10 0.15
−0.3 −0.2 −0.1 0.0 0.1 0.2 0.3
met
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Vashon DriftCapilano Sediment
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PC Scores
Simplified Stratigraphy
Gravel/pebblesShellsOrganic/roots
Mud
Silt
Fine sand
Medium sand
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Diamicton
No recovery
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−0.4 −0.2 0.0 0.2 0.4PC Scores
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Simplified Stratigraphy
Gravel/pebblesShellsOrganic/roots
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Silt
Fine sand
Medium sand
Coarse sand
Diamicton
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Quadra Sand
Vashon DriftCapilano Sediment
Cowichan Head Formation
PC1PC2
Das
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d D
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PC 1
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Fe
K
Mn
Rb
SrTi
V
Zn
Zr
� ��
�
��
�
�
�
Dashwood DriftCochrane
CDW1CDW2CDW3CDW4CDW5
CH1CH2
CP
QD
SDW1SDW2SDW3SDW4SDW5
VA
�
Principal component loading and scores for PC 1 and PC 2. Elements of similar relationship are plotted as a positive correlation while elements with an opposite relationship plot as a negative correlation.
For the Spider borehole Dashwood drift populations display less clumping than Cochrane and occupy an area more towards the +PC 2 zone. These sediments also display a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island.
Most units of the Dashwood drift for Cochrane display clumping populations suggesting localized variability in provenance. The populations occupy an area of both - PC1 and PC 2. These sediments display a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island.
Lower Cowichan Head Fm sediment display element similarities with the underlying Daswood Drift diamictons and marine sediments. Upper Cowichan Head Fm. sediments display elemental similarites with the overlying Quadra sand.
Quadra sand displays elemental associations related to granitic provenance of the Coast Mountains.
Vashon drift displays elemental associations similar to unit two of the Spider and Cochrane Dashwood drift .
Capilano sediments displays similarites in elemental associations to the lower Cowichan Head Fm.
Cochrane
Centered log ratio transformed geochemical data for PC1 and PC2 plotted adjacent to the Cochrane borehole stratigraphic section.
Spider
Centered log ratio transformed geochemical data for PC1, PC2 and PC3 plotted adjacent to the Spider borehole stratigraphic section.
-120
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-80
-60
-40
-20
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-20
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-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-120
-100
-80
-60
-40
-20
-120
-100
-80
-60
-40
-20
00 5 10 15 20 25 0 200 400 600 800 20000 40000 60000 0 40 80 120 160 0 50 100 150 200 250 20000 80000 140000 4000 9000 14000 0 20 40 60 80 0 1000 2000 3000 4000 0 200 400 600 2000 6000 10000 0 100 200 300 400 500 20 70 120
As Ba Ca Cr Cu Fe K Mn Rb S Sr Ti V Znppmppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
0 1000 2000LOD
1Unit
2
3
4
5
0 500 1000 1500 2000
100 150 200
ppm
-120
-100
-80
-60
-40
-20
0
ppm
-120
-100
-80
-60
Zr
met
ers
Clay(% <4um)
Sand(% <2mm)
Silt(% 63-4um)
0 20 40 60 80 100 0 20 40 60 80 100 0 10 20 30 40 50
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-100
-110
-80
-60
-50
-70
-90
-40
-20
-30
-10
0
LOD
LODLOD
LODppmppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
1Unit
2
3
45
met
ers
-120
-100
-80
-60
-40
-20
00 5 10 15
-120
-100
-80
-60
-40
-20
00 200 400 600
-120
-100
-80
-60
-40
-20
010000 30000 50000
-80
-60
-40
-20
010000 50000 90000
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
00 500 1000 1500 2000
-120
-100
-80
-60
-40
-20
010 20 30 40 50
-120
-100
-80
-60
-40
-20
00 0 200 400 600500 1000 1500 2000
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
00 4000 8000 12000
-120
-100
-80
-60
-40
-20
00 100 200 300 400 500
-120
-100
-80
-60
-40
-20
020 40 60 80 100
-120
-100
-80
-60
-40
-20
0100 300 500 700
-120
-100
-80
-60
-40
-20
0
As Ba Ca CuCr Fe K Mn Rb S Sr Ti V Zn Zr
-120
-100
-80
-60
-40
-20
00 0 30 60 90 120 15020 40 60 80 100 2000 6000 10000 14000
Clay(% <4um)
Sand(% <2mm)
Silt(% 63-4um)
0 20 40 60 80 100 0 20 40 60 80 100 0 10 20 30 40 50
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-80
-60
-40
-20
0
-120
-100
-110
-80
-60
-50
-70
-90
-40
-20
-30
-10
0
met
ers
-100
-110
-80
-60
-50
-70
-90
-40
-20
-30
-10
0
met
ers
-120
-100
-110
-80
-60
-50
-70
-90
-40
-20
-30
-10
0
Borehole diameter:
Depth Drilled:
Easting: 382 789m
Project: Groundwater Assessment
Borehole: SpiderNorthing: 5 469 236mLocation: Quacilum, BC Date Logged: March 2013
Datum: NAD83UTM Zone: 10
pXRF:
Size Fraction:
Vial Window Material:Original Material:
Niton XL3t GOLDD, 50-kV Cygnet X-ray tubeDwell Time: 60 seconds per High, Main, and Low filterMode Type: Soil Mode, Compton normalization
<0.063 mm
4 micron SpectroCertified Mylar polyesterFreeze-dried, disaggregated, seived
Date Drilled:
Study Area: Nanaimo Lowlands Method:155 mm
117.43 m
December 2012
Sonic
Simplified Stratigraphy
Gravel/pebbles
Shells
Organic/roots
Hydrostratigraphic Units
Quadra sands: sand
CowichanHead Fm: silt, gravel, sand, peat
Dashwood drift: till
clay/stony clay with marine shells
Vashon drift: till lenses, gravel, sand
Capilano sediments: deltaic depositsMud
Silt
Fine sand
Medium sand
Coarse sand
Diamicton
Borehole diameter:
Depth Drilled:
Easting: 379 107m
Project: Groundwater Assessment
Borehole: CochraneNorthing: 5 472 671mLocation: Quacilum, BC Date Logged: March 2013
Datum: NAD83UTM Zone: 10
pXRF:
Size Fraction:
Vial Window Material:Original Material:
Niton XL3t GOLDD, 50-kV Cygnet X-ray tubeDwell Time: 60 seconds per High, Main, and Low filterMode Type: Soil Mode, Compton normalization
<0.063 mm
4 micron SpectroCertified Mylar polyesterFreeze-dried, disaggregated, seived
Date Drilled:
Study Area: Nanaimo Lowlands Method:155 mm
129.23 m
December 2012
Sonic
Gravel/pebblesShells
Organic/roots
Mud
Silt
Fine sand
Medium sand
Coarse sand
No recovery
No recovery
Simplified Stratigraphy
Gravel/pebbles
Shells
Organic/roots
Hydrostratigraphic Units
Quadra sands: sand
CowichanHead Fm: silt, gravel, sand, peat
Dashwood drift: till
clay/stony clay with marine shells
Vashon drift: till lenses, gravel, sand
Capilano sediments: deltaic depositsMud
Silt
Fine sand
Medium sand
Coarse sand
Diamicton
No recovery
Dashwood Drift
Diamicton overlain by mud and gravel.The gravel is a mixture of plutonic lithologies derived from the Coast Mountains and volcanic and sedimentary lithologies from the east coast of Vancouver Island.
Depositional environment: glacial, glaciofluvial, ice-contact and glaciomarine to marine The sedments were deposited during the early Wisconsin penultimate glaciation.
Cowichan Head Fm.Upper member of sandy silt and gravel from volcanic and sedimentary rocks, commonly with reddish oxidized hues rich in fossil plant remains is interpreted asstuarine and fluvial environments.
Cowichan Head Fm.Lower member of clayey silt and sand with marine shells is interpreted as glaciomarine
Quadra SandHorizontally, and cross-stratified, sand composed of quartz, feldspar, and lithic fragments of granitic provenance.The sand becomes younger to the south away from its source in the Coast Mountains.
Lower parts of the Quadra Sand contains wood and peat lenses is interpreted to be subaerially outwash deposited in proglacial environment on floodplains and locally as deltaic deposits.
Vashon DriftSandy diamicton, with local mud rich, and sand and gravel facies is interpreted as glacial till formed in a variety of ice-contact depositional (landform) settings including esker, deltas, and fans.The lithologic composition reflects the Coast Mountains, Georgia Depression, and reworking of the Quadra Sand.
Capilano SedimentThe sediment consists of sand and gravel with minor diamicton. It is interpreted as a deglacial succession of coarse glaciofluvial outwash that becomes more distal upwards.1
2
3
3
2
4
5
6
4
5
6
7
8
9
10
11
12
13
14
78
9
1
1011
12
13
14
Data obtained by pXRF spectrometry can be plotted and compared with the visual stratigraphic sediment descriptions and laboratory grain size analyses. An upwards increase in silt content of the Dashwood Drift is reflected in an upwards increase in concentration of many elements such as Ca, Cr, Cu, Fe etc as seen in the Spider borehole. The Cowichan Head Fm. is expanded in the Spider borehole where the lower unit is comparable to the Dashwood Drift and the upper unit is comparable to the overlying Quadra sand. The Quadra sand displays decrease in silt and clay content compared to other sediments and displays an increase in Sr, and a decrease in Cr, Cu and Ti. The Vashon Drift and Capilano Sediments can be differentiated from each other, and the underlying Quadra Sand, by variations in the concentration of elements such as Ba, Fe, and Mn.
Borehole Chemo-Stratigraphy + Grain Size Data
To our knowledge these results are the first systematic geochemical
characterization of late Pleistocene succession in the Nanaimo Lowlands.
The Cochrane and Spider borehole data demonstrates that pXRF geochemistry is valuable in differentiating stratigraphic units and can provide insight into the
provenance of these sediments.
Soil Mode
Soil Mode
Cochrane
Spider
