Archaeology through a different lens: Thin section analysis of lithic materials

Written by: Emily Moffat, Regulatory Approvals Coordinator, Archaeological Survey of Alberta

By examining the microscopic details of a lithic material, the geological history and characteristics of the rock comes into focus, which contributes to our understanding of the archaeological record. Archaeologists use this information to understand how people made tools, how they collected or traded stones, and how they moved around past landscapes. Thin sections therefore provide a different lens through which we can view human behaviour.

Thin sections are extremely fine slices of material that are viewed under a microscope to observe details not visible to the unaided eye. Petrography is the detailed description of the composition and texture of rocks and although it started in the field of geology, it has since been applied to archaeology. Petrographic analysis of thin sections has proven to be a powerful tool in better understanding archaeological materials, such as stone tools and other lithic artifacts, by furthering our knowledge of the rock types that they were made from.

To make a thin section, a small cut of rock is adhered to a glass microscope slide and polished down to a thickness of about 0.03 mm. At this point, the sample is so thin that light can pass through it. Petrographic microscopes are specifically designed to view rock thin sections because they have light polarizers that reveal unique optical properties of minerals. By viewing the rock under these polarizers (termed plane polarized and cross polarized light), the minerals within the sample can be identified and small-scale features that give clues as to how the rock formed become visible.

Rock thin section and petrographic microscope. Source: Emily Moffat.
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The Archaeological Survey in Numbers- 2019 Update

Written By: Colleen Haukaas (Archaeological Survey)

This week’s post is an update on archaeological project and site data for 2019 from the Archaeological Survey. Click the image below the see the full size.

Archaeological Survey in Numbers 2019

Disclaimer: the archaeological site counts for 2019 may not be final. They are constantly being updated as consultants and researchers submit their reports to the Archaeological Survey.

See previous infographics from this series here:

Archaeology and Development: Statistics from the Historic Resources Management Branch

Archaeological Survey in Numbers Part One: Archaeological Permits

Archaeological Survey in Numbers Part Two : Archaeological Permit Holders and Companies

Archaeological Survey in Numbers Part Three : Archaeological Site Investigation

The Archaeological Survey in Numbers – 2017 Update

The Archaeological Survey in Numbers – 2018 Update

Alpine Archaeology and a Pre-contact Stone Quarry in Alberta’s Rocky Mountains

Written by: Todd Kristensen, Archaeological Survey of Alberta

Jasper National Park and Willmore Wilderness Park include some of the most rugged and remote mountains in Alberta; and for over 10,000 years, people have called these places home. A high alpine pass at the north edge of Jasper and south edge of Willmore holds clues of an important resource that ancient people visited year after year, in a place that nowadays only hardy back-packers and horseback visitors can reach.

Glacier Pass contains a quarry of stone that people used to make spear heads, knives, scrapers and other tools. The quarry was discovered by archaeologists B.O.K. Reeves and J. Elliot in the early 1970s. The rocks found there are what geologists call ‘concretions’ that were picked up as rounded cobbles by people long ago. Recent archaeological research tells us that the round rocks were then hammered to get rid of certain pieces and expose the best quality stone for making tools.

Stone cobbles like the ones here at Glacier Pass were picked up and worked into spear heads, knives, scrapers and other pre-contact tools. Source: Todd Kristensen.

 

A laboratory technique called hyperspectral scanning has confirmed that the composition of artifacts made from Glacier Pass concretions matches the composition of specific bands or portions of the cobbles from Glacier Pass. Glacier Pass concretions formed when bands of silica-rich rock grew around a core over millions of years. Some bands were good for stone tools while other portions of the rock were thrown out because they were too soft and/or unpredictable to flake or ‘flint knap’. Source: Todd Kristensen.

Based on the number of artifacts found by archaeologists, Glacier Pass was likely visited by small groups of people thousands of times over thousands of years. The stone quarry was part of a seasonal round when people moved from month to month to different areas to exploit or target different things. The alpine concretions at Glacier Pass were probably collected after the snow melted in summer or in fall when people hunted big game animals on high slopes like sheep and caribou.

Recent research by an archaeological team from the Archaeological Survey of Alberta, Parks Canada and the University of Alberta has revealed that pre-contact people cracked Glacier Pass concretions to get at specific zones or bands of high quality stone that was ideal for making stone tools. The first two rows in this picture are mostly flakes removed while making tools. The bottom row (artifacts 11-15) are stone tools including knives, a core and a likely spear head that may be over 6,000 years old (14). Source: Todd Kristensen.

Modern visitors to Glacier Pass are unlikely to see tools: most of the artifacts there today are flakes of rock that people broke off while making stone tools. Almost all the finished products were carried away from the area. Visitors are reminded to respect the story of parks and mountain landscapes in Alberta by leaving all artifacts and rocks in place for others to experience. And remember that the land under our feet has a deep history full of geological wonders and human adaptations.

Glacier Pass between Jasper National Park and Willmore Wilderness Park is a beautiful and fragile place. To preserve the story of this landscape, and others in Alberta, visitors are encouraged to leave stones and artifacts in place. Source: Todd Kristensen.

 

Pitch and Timber: A History of Human Relationships with Trees in Alberta (Part 2)

Editor’s note: This is part two of a two-part series on the history of human relationships with trees in Alberta. If you missed part one, read it now.

Written by: Todd Kristensen, Archaeological Survey of Alberta

Development of Alberta’s Forestry Industry

From 1900 to 1910, population growth and steady local demand for lumber meant that most settlements had commercial sawmills. Because of the way that timber berths were leased to operators, most sawmills were small and portable. Some operators harvested in the summer and moved their timber using rivers, flumes (a series of wooden chutes that filled with water and carried logs), splash dams (a temporary wooden dam that held back water that would then be released in a surge to carry logs), and log drives along big rivers that brought wood to riverside mills or to rail yards in river valleys. But winter was generally the ideal time to log because wood could be moved by horses and sleds. Portable sawmills would move machinery on skis to temporary camps in western and northern Alberta. The seasonal nature was perfect for struggling families because farmers could work the fields in warm seasons and cut timber for mills in the winters.

A man poling down Athabasca River between 1937-39 (from the Chisholm Sawmill and Freeman River Lumber Camp). Log drivers floated along with the timbers to dislodge jams and notify the mills when shipments were arriving by water. Image A3790 courtesy of the Provincial Archives of Alberta.

A logging camp (the Jackpine Wood Camp on Little Slave River in 1909) with men and their tools. Image A2532 courtesy of the Provincial Archives of Alberta.

Alberta’s forestry industry was younger than in British Columbia and neighbouring states to the south, many of which had various gold rushes that required commercial sawmills in the 1800s. It was fairly common for Alberta farmers to log in B.C. during winters in the early 1900s and many Alberta ranches provided B.C. logging operations with horses. A good-sized sawmill in B.C. or Alberta could employ several hundred men and up to 60 horses over the winter.

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Quarry of the Ancestors

Editor’s note: All images in the post below were sourced from a report developed by the Archaeological Survey, Lifeways and Stantec.

Written by: Matthew Wangler, Executive Director, Historic Resources Management Branch

For decades, northeastern Alberta has been home to large-scale industrial activity in the region’s massive petroleum deposits. A remarkable discovery in the midst of the oil sands revealed that the same area of the province also accommodated another significant industry in ancient times; that historic and contemporary land use share a common origin in an epic event that profoundly shaped our province’s past.  This blog post will explore how historic resource management in Alberta helped reveal a lost chapter of our province’s history, how the discovery illuminated both the remarkable richness and depth of the Alberta story, and the surprising connections between past and present.

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