When a Tree Falls…A New Approach to Interpreting Archaeological Sites in Northern Alberta

Krista Gilliland1, Jody Pletz, Petr Kurzybov, Peter Stewart, Rob Kadis, and Terrance Gibson2

Western Heritage, 46A Riel Drive, St. Albert, Alberta, Canada, T8N 3Z8. 1kgilliland@westernheritage.ca, 2tgibson@westernheritage.ca

IntroductionMany archaeological sites in northern Alberta’s boreal forests are difficult to interpret compared to non-boreal sites because:

• artifact assemblages are dominated by lithics that have limited interpretive value

• poor organic preservation prevents radiocarbon dating• slow sediment accumulation rates can contribute to poor preservation of occupation layers and/or to mixing of artifacts from different time periods in the same layer

• disturbance processes (tree throw, cryoturbation) can redistribute artifacts

• incomplete understandingsof site formation processescan result in erroneous or incomplete interpretations of archaeological sites

Boreal forest region in Alberta1.

Anatomy of a Profile

Increasing Understandings

GoalTo increase understandings of boreal forest archaeology sites by improving the nature and quality of the data collected during routine historic resources impact assessments (HRIAs).

MethodsEconomical, efficient, and easySediment-based approach:

• Field descriptions of texture, colour•Portable optically-stimulated luminescence (POSL)2

**(POSL); Uses an optical signal to measure time sincesediment was last exposed to sunlight

Study sites from HRIAs conducted in northernAlberta during 2013 and 2014 field seasons

New Perspectives

Unsolved Mysteries

• Identifying possible multiple occupations• Documenting extent of disturbances

• Suggesting that some sitesare of considerable antiquity

• Correlating relative chronologies locally and regionally

• Contributing to regionalpalaeoenvironmental reconstructions • Can we work toward establishing regional chronologies using

OSL calibration curves4?• What do OSL signals of boreal forest sediments represent?• How do site formation and disturbance processes in the boreal forest actually work?

• How to improvecorrelations of artifactswith sediments?

• Some sites appear to be of considerable antiquity• OSL dating could produce archaeologically meaningful ages• The extent of site disturbance is difficult to detect visually• Possibility of distinguishing multiple occupation periods at a site or group of sites

• Archaeological stratigraphies can contribute enormously to past understandings of cultural and environmental dynamics of the region

GaPv-14ST133P

1

10

9

87

6

5

4

3

11

2

Loamy sand

Loamy sand

Loamy sand

Loamy sand

Coarse sand

0

10

20

30

40

50

Root mat

Sandy clay loam

1E+03 1E+04 1E+05 1E+06 1E+07

1

02

03

04

05

06

07

08

09

10

11

0.5 1 1.51

02

03

04

05

06

07

08

09

10

11

1E+04 1E+05 1E+06 1E+07 1E+08

1

02

03

04

05

06

07

08

09

10

11

1.25 2 2.75 3.5

1

02

03

04

05

06

07

08

09

10

11

0 0.2 0.41

02

03

04

05

06

07

08

09

10

11

IRSL(counts)

IRSLdepletion

OSL(counts)

OSLdepletion IRSL/OSL

1E+04 1.25 2.0 2.75 0.2 0.40.00.5 1.0 1.5

1E+03

1E+06

1E+06

1E+05

1E+07

1

2

3

4

5

6

7

8

9

10

11

1E+05

1E+07

1E+08

1E+04 3.5

POSL interpretation

Relatively rapid deposition

Loamy sand in Samples 9, 8 have higherfeldspar content (i.e. IRSL/OSL ratio) than underlying Samples 11, 10; may represent influx of freshlyeroded material

Pause or change in deposition at about 40 cm BS(i.e. above Sample 8, as seen in no. of counts)

Relatively rapid deposition

Fluctuations in depletion and IRSL/OSLratios suggest increased variability in source and/or nature of depositional processes comparedwith above and below; possible transition period (i.e. from fluvial to aeolian deposition)

Gradual deposition (no. of counts in Sample 4 isan order of magnitude larger than that in Sample 1),although possible depositional break (B) before Sample 1

Consistency in depletion and IRSL/OSLratios suggest similar sediment source and depositional processes, particularly whencompared to underlying samples

POSL results are consistent with interpretation thatSamples 4-1 represent aeolian deposition

Fluvial

Aeolian

B

Artif

act

zoneOver 200 lithic flakes

recovered frombetween 5-30 cm BSbut no visible stratigraphic breaks-Disturbance? Intact?

Coarser sands below30 cm are interpretedas fluvial/glaciofluvial3

Field texture andcolour are especiallyimportant to notefor more accurateinterpretations

Age-with-depth pattern suggests minimal disturbance

Distinct sediment source from ~25 cm to surface

Gradual deposition from ~ 25 cm to surface

Depositional break between ~15 and 8 cm BS

Rapid depositional phases for fluvial sediments

Depositional break ~40 cm BS

Conclusions• Disturbance does

not appear to be responsible for artifact distributions

• Distinct break at ~25 cm BS likely corresponds to onset of Holocene aeolian deposition

• At least 2 occupation periods likely

• Oldest occupation may be considerably older than younger one

• May be able to date the site using OSL

Oldest artifact-bearing sediments are one order of magnitude older than the youngest sediments

Calgary

Edmonton

Foothills Natural RegionUpper Foothills

Lower Foothills

Canadian Shield Natural RegionKazan Uplands

Parkland Natural Region

Central Parkland

Peace River Parkland

Foothills Parkland

Grassland Natural Region

Mixedgrass

Northern Fescue

Foothills Fescue

Dry Mixedgrass

2005 Natural Regions and Subregions of Alberta

2005 Natural Regions and Subregions of Alberta - Alberta Sustainable Resource Development, Alberta Environment,

Alberta Community Development and Agriculture and Agri-Food Canada, June 2005

Boreal Forest Natural Region

Athabasca Plain

Upper Boreal Highlands

Lower Boreal Highlands

Peace-Athabasca Delta

Northern Mixedwood

Dry Mixedwood

Central Mixedwood

Boreal Subarctic

Rocky Mountain Natural Region

Montane

Alpine

Subalpine

These conditions are obstacles to effectively interpreting, managing, and protecting the archaeology of past cultures that inhabited the northern Alberta region, an area that is undergoing intensive developmental pressure.

Boreal Region

Field sampling for POSL-almost as easy as shoveltesting!

Identifying multiple occupations at sites and correlating relative chronologies across a region

References1. Modified from Government of Alberta. 2005. Natural Regions and Subregions of Alberta. Alberta Sustainable Resource Development, Alberta Environment, Alberta Community

Development and Agriculture and Agri-Food Canada, Edmonton.2. Sanderson, D.C W. and S. Murphy. 2010. Using simple portable OSL measurements and laboratory characterisation to help understand complex and heterogeneous sediment

sequences for luminescence dating. Quaternary Geochronology 5(2-3):299-305.3. Fenton, M.M., E.J. Waters, S.M. Pawley, N. Atkinson, D.J. Utting and K. Mckay. 2013. Surficial Geology of Alberta. In ERCB/AGS Map 601. Scale 1:1,000,000. Energy

Resources Conservation Board, Edmonton.4. E.g. Bateman, M. D., S. Stein, R.A. Ashurst and K. Selby. 2014. Instant luminescence chronologies? High resolution luminescence profiles using a portable luminescence

reader. Quaternary Geochronology, http://dx.doi.org/10.1016/j.quageo.2014.12.007.

Charles Schweger, Department of Anthropology Palaeoecology Laboratory, University of AlbertaTim Kinnaird, David Sanderson, and Simon Murphy, Scottish Universities Environmental Research CentreRobin Woywitka, Alberta Culture and TourismCanadian Forest Products and Millar Western Whitecourt

Acknowledgements

Rapiddeposition

Distinct sedimentsource

Possible disturbance

POSL of this Swan Hills profile in-dicated that both buried soils and the overlying sands likely date to a similar time period, and that the sands overlying the buried soils share a similar source that the un-derlying soils do not. This work has the potential to influence cur-rent and future palaeoenvironmen-tal and archaeological reconstruc-tions in the region. GfPs-18

ST712P

Ae11

109

876

5

4

3

1

2

Depthof artifactrecoveries

10

20

30

40

cm BS0

Stratigraphy

Root mat withabundant charcoal

Description

Clay with frequentrounded cobbles

Soil horizon

10YR 3/3

10YR 4/4

10YR 5/4

Bm

Decreasingage

Silty clay loam withabundant rounded cobbles

Clay with fewrounded cobbles

C

Interpretation

Formation of soil horizonsindicates long-term stability of the soil surface (i.e. minimaldisturbance)

Parent material is interpretedas possibly glaciofluvial innature

Association of artifacts withinsediments that include roundedcobbles suggest either disturbanceor that the artifacts were depositedalong with reworked sediments

Possibility that seasonal orepisodic flooding of a river duringthe early postglacial period resulted in localized redistributionof artifacts in this location

Artifact distributions are within sediments that ap-pear to be fluvial or glaciofluvial in nature. Visual observation, soil characteristics, and POSL sug-gest this profile is intact. Future work should focus on investigations of site formation processes and correlating artifact recoveries with their associated sediments.