OUT IN THE FIELD AND IN THE LAB
Archaeology involves the study of objects that were made and/or used by humans. The study of these objects, or artifacts, occurs through the excavation of archaeological sites and through analysis of those artifacts. The excavation of a site must be systematic and carefully recorded because once a site is excavated, it is destroyed. Thus, all that remains are the detailed research records that were written and the artifacts that were collected. Archaeology can be compared to the investigation of a crime scene, where archaeologists are detectives that must piece together clues to create a picture of the past.
Figure 1. Tools of the trade.
Excavation
Tools Used for Archaeological Excavation
These are some tools that are necessary for excavating archaeological sites that are provided by the instructor and/or employer.
Flat edged shovel: long handled, with the point cut off and
sharpened; for removing vegetation and dirt from an excavation
unit.
Screens: a loose bolt attaching the screen and legs; for sifting dirt
from excavation units and recovering artifacts.
Measuring tapes: metric markings are used for measuring
distances and placing excavation units.
Folding rule tape measures: uses centimeters for measuring
elevation of levels and orienting artifacts and features.
Mason trowel: usually 4 to 6 inches long and diamond shaped;
for recovering artifacts and careful excavation of balk
lines.
Stakes and chaining pins: stakes mark the corners of
excavation units and chaining pins mark corners of balks.
Tools Used for Surveying and Mapping an Archaeological Site
Compass
Measuring tape
Philadelphia rod: long rod with metric markings; used in
conjunction with transit
Transit: measures angles, distances, and control lines in
reference to the datum point.
Forms to Fill Out During Excavation
- Feature Forms:
-
Level Forms:
*Click on image to enlarge.
Figure 2. Feature Form.
Figure 3. Level Form.
Figure 4. Excavation square with
vegetation removed.
Excavating a Square Unit
First, remove any vegetation that is on the surface of the excavation unit (Figure 4). Then begin to remove the sediment ½ inch at a time using a flat edged spade in a careful scraping manner (Figure 5). Place the excavated sediment in a galvanized bucket and once the bucket is full, empty it into a screen (Figure 7). The sediment is then sifted and any artifacts that are found are placed in a labeled paper bag. Excavation should be done in levels. Levels are often excavated in 10 centimeter increments, but it depends on the sediment layering. Level 1 is measured from the surface down to 10 centimeters, and Level 2 is measured from 10 to 20 centimeters, and so forth. After each level is excavated to its proper depth, the balk of the square must be trimmed or cut evenly with a trowel (Figure 6).
Once a level is completed a level form must be filled out. This records the artifacts found, the soil colors (using the munsell soil color chart) encountered, the site name and number, the type of unit, the square name, what level was excavated, the depth of the square from the datum, the recorder's name, and the date. This form also provides a place to draw a map of the unit, which is used to record the locations of important artifacts and/or features. Once subsoil is found and artifacts are no longer encountered, the excavation unit is complete.
Figure 5. Excavating level one.
Why a Square Unit?
1) Square units are easy to map and
layout.
2) The walls of the square can
reveal any stratigraphic information
or layering in sediments.
3) Square units provide a precise and
accurate unit to collect artifacts from
and then record their locations.
Figure 6. Troweling the balk.
Figure 7. Screening excavated sediment.
What Do You Do When You Find an Artifact?
When an artifact is uncovered, the position within the unit where it was found must be recorded. The three dimensional position in which the artifact is found is called the provenience. The location of the artifacts needs to be recorded to show the relationship, or context, between all the artifacts within a site. Once recovered, artifacts should be placed in paper bags that are labeled with the site name and number, the square name, the level excavated (along with depth) and the date.
What If You Find A Feature?
Features are items that cannot be removed from a site without being destroyed because they have become part of the sediment. Features include pits, post-molds, and ditches (trenches). Features are cross-sectioned (half of the feature is excavated) so that its profile can be viewed, and then a sediment sample is place in a labeled bag and taken to the lab for analysis. A feature form should be filled out when a feature is found. This form includes a map of the feature, the site name and number, the square name, the sediment color and the date of excavation. Figure 8 shows the cross-section of a post-mold (the darker soil area that is outlined).
Figure 8. Cross-section of postmold.
Archaeological Lab Analysis
Artifacts collected from a site are taken to a laboratory where they are cleaned with a toothbrush and water. After artifacts are cleaned and dried, they are sorted into categories such as pottery, flint, cannel coal, daub, shell, bone, rocks, et cetera (Figure 8). Pottery is further classified according to the type of temper used, any decoration, et cetera. Flint artifacts are divided into types of flakes, shatter, projectile points, scrapers, blades, drills, or worked flint (flint from which other flakes have been removed), et cetera. These categories are further divided based on whether the flint was utilized or not, and whether or not it was heat-treated (flint tends to be red if it has been heat treated). Bone is divided according to whether or not it has been burned (burned bone is white or black). Bone may also show cut marks or may be worked into a particular shape. Mussel shell is classified according to whether it has been burned or not (burned shell turns grey). Cannel coal (a fine-grained form of coal) is only classified further if it has been worked or carved.
Figure 9. Sorting and weighing artifacts.
Figure 10. Cataloguing artifacts.
After the artifacts have been classified, the quantity and weight of each type of artifact is recorded. For example, all of the shell- tempered plain (undecorated) pottery is counted and weighed. All of the artifacts collected from one level of one square are assigned an unique catalogue number (a number that indicates the year the artifact was found, the number of the site where it was found, and the artifact number). For example, the first artifact catalogued that was found in the year 1997 at site 123 would be catalogued
97-123-1. The second artifact catalogued would be 97-123-2, and so on. These catalogue numbers are written in ink on some artifacts, mainly flint, pottery, and bone using a very fine-point calligraphy pen (Figure 9). Catalogued artifacts are placed in a plastic bag with a label that includes the name of the site, the site number, the square name, the level in which it was found, the catalogue number, and a description of the artifact. An artifact list for the entire square is also made. The records made during lab analysis are one of only a few links that artifacts have with the site from which they were recovered. It is also an index that can be used by other archaeologists who wish to conduct research concerning similar data.