Zooming in on Microscopic Analysis at SA

Sustainable Archaeology has a new piece of analytical equipment - a Nikon SMZ-25 stereoscopic microscope. We are excited by the versatility of this new instrument, which will allow us to view objects within a range of 6.3 to 315x magnification with both direct and transmitted light sources.

Chad Steele, from Nikon Canada, puts the SMZ-25 together.

No single piece of equipment has arrived at our facility intact - everything from our humidity readers to our microCT scanner, even our building, have arrived in multitudes of pre-assembled pieces. This single microscope was no exception - above is an image of just a fraction of the packaging that this piece of equipment came in.

The SMZ-25 is a fully automated microscope; magnification, zoom and even lighting are mechanically adjusted either on the computer or the separate control unit/monitor. Besides magnification, there are a number of lighting options that increase the versatility of the system. It has a transmitted light source in the base that forces light up through an object, allowing us to view things like thin-sections of ceramic or soil on prepared slides. There is a ring light that sits on the lens, providing even illumination of an object, such as a trade bead, from the top-down. And there are goose-neck fibre-optic lights that allow us to move and adjust the angle of the light source to capture and highlight surface details on an object, such as use-wear on the edge of a projectile point. Oblique coherent contrast (OCC) illumination provides contrast and colour to otherwise clear and colourless objects such as diatoms (microscopic algae) or starch. The unit is also equipped with a 5 megapixel camera for capturing publication-quality images, and the Nikon NIS-Elements software comes with the ability to focus-stack (z-stack) multiple images upon one-another in order to capture a clear image with a greater depth-of-field.

Nikon SMZ-25 stereomicroscope with camera and remote control unit.

We look forward to using the microscope to examine floral remains such as seeds and even pollen, phytoliths or diatoms from archaeological sediments. It will also be used to examine the temper inclusions in ceramics, cut marks on faunal remains, usewear on tools, to identify the species of wood/charcoal samples and even examine fingerprints in clay objects. With analytical software capable of defining regions of interest and morphology, counting, measuring, and filtering, this stereomicroscope makes a valuable contribution to the Imaging capabilities of Sustainable Archaeology: Western.

Flotation Machine in Action

Featured in a previous post, Sustainable Archaeology's soil flotation machine from R. J. Dausman Technical Services, Inc. was put through its paces today. A team from New Directions Archaeology Ltd. was on site to un-crate and set up the machine, running the first tests out in the Lawson village at the Museum of Ontario Archaeology, next door. They will be floating dry sediment samples over the next few days that they have collected from some recent excavations the company has been working on.

The machine requires access to running water for its initial fill, as well as access to a source of electricity for circulating the water in the tank. After its initial fill, the machine recycles water within itself to allow for light-fraction flotation, and heavy-fraction rinsing with an attached spray-hose. The material captured in the screens is then allowed to dry on newspaper before it is packaged, and later analyzed. The fine mesh, as seen in the images below, allows for the capture of tiny floating artifacts, such as tobacco seeds. A courser mesh filters the heavier fraction of sediment, which can include artifacts such as shell, bone and pieces of flaked stone tool.

Guest Blog #3: From the Field to the Lab: Artifacts and “Microfacts” from the McMaster Archaeological Field School

Our third guest blog features the Centre for Sustainable Archaeology at McMaster University in Hamilton, ON. This post was written by Jennifer Walton, a third year anthropology student at McMaster, and Research Assistant at Sustainable Archaeology. The blog features her experience using the Centre's materials analysis equipment to examine "microfacts" recovered from the McMaster field school at the Nursery Site (AhGx-8) this past spring.

From the Field to the Lab: Artifacts and “Microfacts” from the McMaster Archaeological Field School

 By:  Jennifer Walton, Honours Anthropology (III), Research Assistant, Centre for Sustainable Archaeology at McMaster Innovation Park

This spring I had the opportunity to attend the McMaster University archaeological field school held at the Nursery Site (AhGx-8) in Cootes Paradise within the Royal Botanical Gardens. The site dates from approximately 3000 years ago and was also used as a farmstead during the historic era.  During the course of the excavation, we were responsible for conducting two different types of sub-surface surveys to find the boundaries of the site and to evaluate the differences between traditional test-pitting used in cultural resource management, and a finer resolution method.  Each student took standard test-pit samples using a shovel alongside bucket-auger samples to analyze the variability in field survey methods.  Understanding the variability in the recovery of artifacts using different techniques is important because of the history of plowing at the site, and the fragmented nature of the artifacts we recovered.  Test-pit sediment was screened in the field, following the guidelines set by the Ministry of Culture. The auger samples were later wet-screened at the Centre for Sustainable Archaeology at McMaster Innovation Park.

Using the auger at the 2012 field school

Auger sampling has been used at the Nursery Site since the 2010 field school. Since the site has been a plough zone for over 50 years, the Nursery Site had experienced heavy disturbances, resulting in the fragmentation of many of the artifacts. Auger sampling is useful in this context because it retains the entire sediment sample and the finer screening method allows for the collection of smaller artifacts, often resulting in more artifacts per litre of soil compared to traditional test pitting.  The boundaries of a site should show a decrease in artifact density as one moves away from the central area of the site, therefore augering is potentially a more effective way of finding the outer limits of the activity area, especially in highly disturbed areas. 

The bucket-auger sampling method uses a hand held device (7.5cm bucket-auger) that is twisted into the ground below the sub-soil to extract an intact sediment sample. All of the sediment is retained, and once in the Sustainable Archaeology lab, each auger sample is washed through 2mm mesh, dried, and the sediment fraction >2mm is examined beneath a stereomicroscope. The sediment from the test pits, in contrast, is screened in the field through 1/8 inch mesh and artifacts are picked in the field. It is the difference in these screening methods, in association with the methods used to identify artifacts that accounts for the variance in artifact recovery.

In the lab the auger samples were wet-screened, and the remaining fraction was viewed under a Zeiss V8 microscope at 10 X magnification to distinguish if the materials were, in fact “micro” artifacts.  Many research questions can be answered from the analysis of these samples, such as artifact densities and types of artifacts found in specific areas of the site or throughout the site as a whole.  Site boundaries may also be estimated and further insight into disturbance levels may be gained. The results from the auger samples have shown new insights into the artifact densities as well as the extreme fragmentation of the artifacts, especially calcined bone, ceramics and tertiary debitage.  Using this survey method and the resources at the Centre for Sustainable Archaeology has allowed us to identify new areas of the site which can be excavated in future field seasons.

Examples of the "microartifacts" found in the auger samples, using a Zeiss V.16 axiozoom telecentric microscope at 20 X magnification. From left to right: historic era ceramic; tertiary debitage; calcined bone; pre-contact ceramic)