Archaeological Survey and Excavation
Lesson Objectives: Understand the steps in locating and extracting archaeological evidence.
What else must the archaeologist do before stepping
outside to begin fieldwork? Your book plunges right into fieldwork without
mentioning crucial issues such as gaining permission or access to lands,
permits for work on public lands, and making sure you have laboratory
and storage space for processing and curating the materials you might
dig up. Another essential step is connection with the local people,
landowners or other residents, to find out what they might already know
about the land. Have they collected artifacts, seen darker soils when
plowing, or heard that some older residents once knew about older historic
structures that once stood there? What will be the effects of your digging
or surveying upon the local community? In our new era of mistrust of
science and government, I have had to assure people that finding artifacts
on their land will NOT mean that the state takes it away from them,
and that I would like to see the artifacts they have collected ONLY
to photograph them, if permitted, not to take them away.
What do we mean by archaeological survey? This
is the answer to the common question, “how do you know where to
dig?” (And again, we do not want to dig everything we find, but
preserve as much as possible.) Survey is the process of locating the
archaeological resources in a given area of land. Doing the background
work can help pinpoint areas of greater interest. Besides the practical
considerations mentioned above, research on the archaeology of the region
is also absolutely essential. Where are most prehistoric sites located?
Along coasts or rivers or springs? Those portions of land would then
have the highest probability and perhaps require the greatest scrutiny.
Is the survey being done in the path of proposed construction? If so,
then perhaps only the areas where the ground will be disturbed need
to be examined.
Learning the environmental and historical variables
must take place before you step into the field. Your book describes
the work of Heinrich Schliemann, who read the classics and located the
Troy of the Trojan Wars. It also mentions the importance of good maps,
not only modern, but historical, to show both how the landscape may
have changed and what historic remains might have once been located
there. In more populated urban areas the old Sanborn insurance company
maps may show building outlines or “footprints” that lie
underneath modern features.
What is meant by remote sensing? Anything (usually technological device) that helps you learn what is on/in the ground without your having to be there or dig there. So a map is a remote sensing device, but even more sophisticated are aerial photos, including aerial infrared photos, satellite images, and pictures generated by various geophysical prospecting techniques such as magnetometers, electrical resistivity detectors, ground-penetrating radar (GPR), other kinds of radar, sonar, and all those spy devices developed by your friendly military scientists. The raised fields of the ancient Maya were not apparent on the ground in Central America, because, well, it is a jungle out there, but they were easily seen during testing of military imaging technology in the 1970s. Buried or jungle-shrouded features can be anything from just black midden stains to traces of ancient canals, buildings, mounds, and other earthworks. If you do as much remote sensing as possible before and during the on-the-ground fieldwork, site discovery is greatly enhanced.
How is most archaeological field survey conducted?
There is no substitute for being there and walking around. Especially
important is covering open and disturbed ground, where shallower remains
may have been churned up by plows, other heavy road building equipment,
burrowing animals, and so on. In Florida, we walk dirt roads, plowed
lanes in orange groves and cotton or soybean fields, and look for gopher
tortoise burrows where the dirt is thrown out around the entrance and
may have artifacts in it. We see on the map where the streams and springs
are, and the highest ground nearby, and usually find prehistoric sites
there. At the northeast end of our campus is a ditch along the road
filled with slimy water and alligators today. Old maps show it was a
pond with a stream outlet to Cypress Creek and the Hillsborough River,
major transportation and communication routes in prehistory. It is no
surprise that there are prehistoric human habitation sites around this
last remaining small ditch! We have also talked with old-timers in the
grounds department and elsewhere, who remember finding “arrowheads”
(spear points) in that area of campus, especially during construction
of various buildings there.
Does survey include any digging? Subsurface sampling
is enormously important, especially in the eastern U.S., which is often
heavily forested. In the desert Southwest you can drive around and see
the standing ruins of prehistoric pueblos. Many of these “windshield
surveys” used to be done in the East, as well, by archaeologists
looking for sites in plowed fields. But there is no substitute for seeing
what is buried, whether there is cultural material on the surface or
not. Methods of subsurface investigation during survey must be fast
but careful. The shovel test is usually 50 cm square and a meter deep
according to Florida state guidelines; it is easily dug in our soft
sands, and the soils can be dry-screened by one fieldworker while the
other is digging (show photos of shovel-testing and other methods).
We can also take cores or soil probes, pressing or twisting a tubular
device into the ground to see what comes out. Besides 1-inch and 4-inch
diameter hand-coring tools, we have a gas-powered auger which drills
into the ground, which can be even faster but more destructive
What other technological devices must modern archaeologists
use? Lately we must have a Global Positioning System (GPS)
unit, which reads signals bouncing off several satellites to give exact
locations in latitude/longitude or other coordinates. We also want to
utilize Geographic Information Systems (GIS), which are simply
computerized ways of making maps of different features that can be overlain
to show relationships of natural and cultural features through time.
Once the site is found, how do you know what part of
it to dig? Site survey and mapping can be done at
several levels, from a rough sketch using a compass and pacing distances
to formal mapping with a surveyor’s transit, electronic station,
or other device. A typical local site here is a scatter of artifacts
on the surface, but there may be a mound, concentrations of artifacts,
a stream or hill, modern features such as roads, that all need to go
on a base map. We often set up a site grid in uniformly sized squares
so that everything can be precisely mapped in plan view and later in
three dimensions. There are good examples in your book (pp. 91-93; show
other examples of site maps).
After getting control of horizontal space, how does
archaeology tackle vertical space? Excavation must be done with an understanding
of stratigraphy, the stratification or vertical positioning
of soils and other materials in layers or strata. The law of superposition
dictates that the earliest strata are usually the deepest (but there
are exceptions in disturbed strata such as riverbank flood deposits
or deliberately constructed mounds—see diagrams in book, pp. 96-97).
It is important to be able to recognize strata deposited by natural
geological processes and cultural processes or both, but it may be difficult.
Since we want vertical as well as horizontal control, we ideally want
to excavate one stratum at a time without mixing them. This is not always
possible if color, texture, and content differences are hard to see.
In such cases we can still maintain some control by digging in arbitrary
levels of a standard thickness, such as 10 cm at a time. Sometimes we
might dig in smaller arbitrary levels of 5 cm within a thicker cultural
stratum, for even tighter control. Or, for a really slow but careful
dig, recording each and every find in three dimensions can be done too.
A formal excavation unit can be as small as a meter square or as large
as many meters. We usually dig in squares to be able to see a clean
view of vertical layering. We usually use metrics since they are easier
and more international, though some historic archaeologists may dig
in units of feet and yards if the site is, say, a British fort that
was laid out using those kinds of measurements.
How do we record the three-dimensional provenience?
Your book shows methods, drawn on page 103, using a surveyor’s
transit and measuring rod, and also using a level string, plumb line,
and tape measure. Usually cultural materials such as artifacts and ecofacts
are recovered as individual finds while digging slowly with shovel or
trowel or other, even smaller implement, or else they are recovered
in a screen where the excavated soils are taken for processing. Dry
screening can be done in some of Florida’s sandy soils, shaking
the sand through usually 1/4-inch mesh. Waterscreening is better, since
it washes away the soil and leaves everything easier to see, and can
be done with smaller screen sizes such as 1/8-inch mesh, but you need
a source of water. For our excavations on campus, we just hook up a
hose to the closest faucet, but for our work in the swamp and wilderness
we need our water pump to get water from rivers, bays, and other sources.
What is soil flotation? Just a fancier way of
recovering the smallest remains, it involves taking a standard-sized soil
sample (we use 9 liters) and processing it not through the regular screen
but through the flotation machine. This is a device, usually homemade,
with a 50-gallon drum, a hose connected to a showerhead inside, and graduated
screens within, as well as a very fine screen to catch bits of charcoal
and other light materials that float to the top and out a spout. Much
good information on food remains has come from soil flotation, which can
recover seeds, fish scales, and other tiny remains lost to archaeologists
in the past. A late prehistoric site we excavated in northwest Florida
was transformed into a historic site when a tiny glass seed bead was recovered
during flotation!
What methods are used in recording information from field survey and excavation? A plethora of field forms (show examples), field notes in waterproof ink on surveyors’ waterproof notepaper, photographs, maps, drawings, and other techniques are used. This may also include audiotaping and videotaping fieldwork. There can never be enough recording, and it is often very redundant. But since information is lost the minute things come out of the ground, it is crucial.
How much survey and excavation is enough? It depends
upon the individual project. There is a big difference between a multiyear
research project at a protected site and a salvage project where survey
and excavation must take place in the path of proposed construction.
American archaeologists, especially those working in cultural resources
management, differentiate among the levels of investigation as follows:
Reconnaissance survey usually involves walking around the project
area looking for surface materials and doing the historical background
work to see what might have been there and what is already known or
found. Phase I survey is more intensive and involves subsurface
methods such as shovel testing and writing a more comprehensive report.
Phase II test excavation may be done after survey has identified
the sites in an area, to place formal test units at those sites suggested
to be significant. Significance is often difficult to define.
It can be understood in local to international terms. A significant
site will have undisturbed cultural deposits that have good potential
to produce new information about a past people. This usually includes
features, good intact midden soils, diagnostic artifacts, and so on.
An internationally significant site will usually be a major monument.
Phase II excavation can even include stripping off disturbed soils with
heavy equipment such as a front end-loader to see if undisturbed features
such as refuse pits or house patterns are present below.
Phase III excavations, also known as salvage
or data recovery, might take place at the sites determined during Phase
II to be significant but destined to be destroyed by whatever construction
is planned. During Phase III more extensive excavation units are dug
and as much information and material as possible is recovered, since
this will be all that is retrieved from the site (usually) before it
is gone. There is obviously the ethical consideration, again, of digging
and thus destroying too much of a site if it is NOT destined to be disturbed
or destroyed. Furthermore, it is always better to conserve instead of
dig. Good cultural resources management strategies often involve working
with those planning the construction to avoid site destruction. For
example, after surveying and Phase II testing in the path of a housing
development in Florida, we might find a few sites that are significant.
We might persuade the developer to move planned buildings away from
the site, change the design of the entire plan, or dump some loads of
fill dirt over the site and preserve it as a park or green space, maybe
even with an outdoor display describing the prehistoric people who once
lived here (good public relations for the developer, as well!).