9 Chapter 9: Conducting Archaeological Research

By the end of this chapter, you will be able to:

• Explain the six stages of archaeological research.
• Describe the elements of a research design.
• Describe the three general approaches used by archaeologists to identify sites.
• Compare and contrast the techniques used for reconnaissance.
• Characterize the various types of evidence of archaeological sites that can be detected through remote sensing.
• Understand the different kinds of dating techniques

You may think that archaeologists just walk into the field and begin digging up amazing artifacts. Actually, many hours have been spent preparing for that moment when the archaeologists pick up their shovels. Extensive planning is required before excavation or even a survey can begin. The archaeologists must formulate a research question, which will guide all aspects of the work including where to excavate, what kinds of data to collect, and what types of artifacts are relevant to the study. This is a critical step that never gets portrayed in the movies!

Archaeological Research

In the early days of archaeology, archaeologists focused on the excavation of sites. They would find a site, dig, and study the artifacts. However, they were not as concerned about the broader context of their findings. How did humans of the time interact with their environment, for example? Today, archaeologists approach research in a more focused way with specific goals in mind. The overarching goal now is to preserve the archaeological record, which means actually digging is not the first option for research. The best way to preserve a site is to leave it in its original state! When digging does occur, it means excavating in a careful and precise way so as to preserve the context of the site in question and the provenance of any artifacts recovered. So, before any field or laboratory work begins, archaeologists must plan their research. Archaeological research is typically done in six general stages: research design, implementation, data acquisition, processing and analysis, interpretation, and publication (Fagan, 2006).

Research Design

The first stage of archaeological research is to carefully formulate a systematic plan to execute the research, known as research design. It is during this stage that background research is completed and the research questions are developed. A research design needs to be thought out and thorough including the details that will be needed to acquire funding and permissions. Sometimes excavations are related to the appled archaeology field of cultural resource management , often called CRM. This means the research plan will also need to consider compliance with local and national laws, for instance  Section 106 of the National Historic Preservation Act in the United States. As the research design is being developed, there are some key elements that need to be considered.

 

Implementation

Once the research design is in place, then the implementation phase begins. This is when archaeologists begin procuring the funds to undertake the research project as well as putting together the research team. At this stage they identify any consultants and volunteers, if needed, to assist with the project, as well as ensure all necessary equipment is accessible. Most importantly, archaeologists must obtain all necessary permissions from federal, state, and local governments in addition to tribal authorities before any excavation can begin. Increasingly collaboration with local and descendant communities has become an important part of archaeological research and the implementation phase is a moment to cement those relationships, though optimally those communities are involved in the research design process as well!

Data Acquisition/Fieldwork

After the team has been assembled, equipment gathered, and all permissions have been granted, the collection of data begins. However, the shovel and trowel are not the first tools for which an archaeologist reaches. Research begins with an archaeological survey using non-intrusive tools. An excavation, actual digging, is only initiated if is determined necessary after the initial survey has been completed.

Processing and Analysis

As artifacts and other aspects of material culture are collected, they are sent to the lab for processing and analysis. This phase begins during excavation and can continue long after the archaeologists have closed down the excavation and recovered the site. Artifacts are cleaned, labeled, classified, cataloged, and prepared for curation. This stage is when materials may be sent out for dating or samples sent to specialists for analysis.

Today, archaeological data is entered in a computer database, most often this is a Geographic Information System (GIS). Geographic Information Systems is a powerful new tool for mapping archaeological sites as well as the data related to those sites. In addition to generating maps, GIS can be used to perform analysis on aerial imagery and LiDAR models.

Interpretation

In the interpretation phase, all information that has been gathered from the research is brought together in a final summary or report of the findings. This explanation of the findings must relate to the original research questions. It is a report on the knowledge that has been learned through the research project. Collaboration with local and descendant communities can provide additional insight at this stage and improve archaeological interpretations.

Publication

Finally, all research results must be made accessible to, at the minimum, the academic community but preferably to the general public as well. If the results of the research is not recorded, the archaeological record of that site has been lost. The site has been destroyed by excavation and the data collected is lost. Until the research is published and recorded, the archaeological record is incomplete.

Archaeological Fieldwork

There are three steps when undertaking archaeological fieldwork: 1) finding the site, 2) assessing the site, and 3) excavating the site (Fagan, 2006). Some archaeological sites have no problems being identified, such as the Pyramid of the Sun in Teotihuacán, the Pyramids of Giza in Egypt, and the burial mounds and earthworks in eastern United States. However, most sites are inconspicuous and well-hidden. Many archaeological sites have been located through accidental discovery. You have probably seen different news stories on some exciting new discoveries during the construction of a parking lot or highway. One of the most famous archaeological finds in North America to happen randomly was discovered by an African American cowboy named George McJunkin (Figure 1). McJunkin was born enslaved close to Midway, Texas. He grew up with horses since his father was a blacksmith. After the Civil War, he moved to New Mexico and lived near Folsom. While searching for a lost cow and repairing fence lines, he noticed some old bones and a spear point (Nash 2017, Peeples 2015). The bones were later determined to be an extinct species of bison…and the spear point? The spear point is now known as a Folsom Point. The Folsom point was once the oldest stone tool in North America, dating to about 10,000 years ago, though older lithics have now been found.

 

However, we cannot always rely on an accidental discovery. One way to locate sites is to research historical documents and maps. Old historical documents often contain descriptions of a former settlements or burial grounds which sometimes include a general location of a site that has long been lost. These documents can give archaeologists a starting point when searching for the site using aerial imagery and newer technologies such as LiDAR. Many times the survey techniques and tools used in assessing the site are the same that are used for finding the site.

Reconnaissance

Sites not uncovered by chance or by reviewing historical documents are usually detected using three types of reconnaissance: aerial reconnaissance, ground reconnaissance, and subsurface detection. Reconnaissance is the preliminary survey of the site. Basically, it is the initial gathering of information that will inform about the presence of archaeological materials, how to proceed, and determine if additional research is needed. Aerial reconnaissance and some subsurface detection methods can be labeled remote sensing. Remote sensing is using methods of reconnaissance that detect subsurface features and sites through the use of devices and technology such as aerial photography, LiDAR, and ground-penetrating radar. Today, archaeologists rely heavily on remote sensing technologies to investigate and study a site in a non-intrusive manner.

Aerial Reconnaissance

As the name suggests, aerial reconnaissance locates, records, interprets and monitors archaeological sites from above. This is particularly useful when studying large-scale patterns of habitation and the use of a landscape. Photos sometimes reveal buried sites in a surprising way. Earthworks (which consist of buried ditches, banks, and stone walls), crop marks, and soil marks, are all evidence of human habitation and cultivation. These signs are often more apparent from above, and trained eyes can identify areas in the images that suggest archaeological remains beneath the surface.

Aerial photography was first used in archaeology in the early twentieth century and its use expanded significantly after World War I. Archaeologists and their pilots would fly over areas they were interested in investigating, looking for signs of archaeological sites and land formations in which sites or artifacts are commonly found and then photographing them from the air (Figure 2). Not a lot of people are aware that Charles Lindbergh and Anne (his wife) both contributed to early aerial photography efforts. Charles first spotted Mayan ruins while flying in 1928/29 over the Yucatán peninsula in Mexico. His interest in archaeology lead him to volunteer, and while his wife piloted a two-seat, open cockpit biplane Charles would lean out and take photographs (Stewart 2017).

 

In some aerial images, sites can clearly be seen, such as ceremonial locations like Stonehenge or Native American burial mounds. Others, like crop marks, can appear in vegetated areas when plants are growing over buried walls or ditches that stunt or boost their growth relative to the rest of the plants in the area. Soil marks can be revealed when, for example, a plow uncovers a buried stone feature that is close to the surface, exposing a distinct difference in soil color and texture.

As technologies have developed, new avenues of aerial reconnaissance have opened up. One such technology is Light Detection and Ranging, known as LiDAR, which involves lasers scanning landscapes and sites. An aircraft flies over its target sending pulses of light to the surface and measuring the time it takes to reflect back to the receiver. The receiver collects thousands of data points that can be used to create digital elevation models (DEMs). The models are then used to create 3-dimensional topographic maps of the surface. This technology “sees through” dense vegetation and ground cover to reveal the topography below. This allows archaeologists to identify earthworks, overgrown structures, and other features that are hidden in overgrown forests and jungles. Recent applications of LiDAR in Mesoamerica have been incredibly successful, leading to the discovery of 60,000 Mayan structures that include homes, fortifications, and causeways. Thanks to this work, we now know that the Mayan world was much more densely populated and interconnected than previously thought. Archaeologists have revised their estimates of the Mayan population to include millions more people in previously unknown city-states.

Drones, Satellite Imagery

The availability of drones with photographic equipment attached has dramatically increased the accessibility and affordability of aerial reconnaissance efforts. Archaeologists who once needed to hire a pilot can conduct many aerial reconnaissance flights themselves. However, initial reconnaissance flights might not be needed since satellite imagery is freely available, through government databases on the internet and popular tools like Google Earth, and can often provide necessary aerial images. Since these tools are right at a person’s fingertips, they can be used as a first pass of preliminary reconnaissance, guiding future, more detailed inquiries with techniques that offer a greater resolution. Google Earth also provides historical data through satellite imagery archived over time, allowing archaeologists to compare views of a location, potentially revealing changes in environmental conditions, water levels, and even a site’s condition (before plowing, construction, or some other disturbance).

 

Since satellite imagery is free and drone technology is increasingly affordable, barriers to conducting reconnaissance have decreased, which is good for archaeologists and has opened up a new field within the discipline, namely Space Archaeology. Space archaeologists like Dr. Sarah Parcak look for ancient sites using air or space-based means, like satellite images (Marchant 2019). In addition to finding sites in this way, archaeologists can also monitor the condition of known sites, to identify those at risk from environmental hazards or human activities such as looting or development.

Ground Reconnaissance

Eventually, of course, archaeologists must get out of airplanes and their offices and check out potential sites in person to see what is actually there and confirm the presence of sites. They conduct ground reconnaissance to find, record, interpret, and monitor archaeological sites. This type of reconnaissance does not involve excavation. It examines what is visible and accessible directly on the surface of the ground. A primary tool is a surface survey—a systematic search for artifacts by methodically walking the site…that means a lot of walking.

How the survey is conducted depends on one’s research question and the specific conditions at a site. Researchers can, for example, consider an area outlined by a trajectory such as a radius or a line extending outward from a central or starting point. The surveyors look for artifact scatter and/or unusual discolorations that suggest prior human behavior. When a possible artifact or feature is identified, the surveyor places a flag in the ground to identify its location and continues surveying. No excavation occurs at this time. Once the survey is complete, the flagged locations are precisely identified by GPS coordinates. Their locations are recorded and artifacts can then be collected, if appropriate, given the research question.

Subsurface Detection

Once a site has been found, archaeologists need to assess what is present at the site and what activities may have taken place there in the past. Since the goal of archaeologists is to preserve the archaeological record, they prefer using methods that are non-intrusive and have minimal impact on the integrity of the site. What happens when the features of a site are hidden underground? Thankfully, today’s technology provides the tools for subsurface detection of some classes of material culture and to “see below the ground” without digging. Using non-intrusive equipment, archaeologists can identify walls, buildings, and burials that can not be seen from the surface. However, there are times where some digging may be necessary to verify the findings or to understand what is being shown in the data. That is when archaeologists may use probing or test pits for the initial survey of the site.

 

Non-intrusive Tools

Archaeologists also have subsurface detection tools that allow them to conduct reconnaissance below the surface of the ground without excavating. One way to do preliminary exploring below the surface is to use a metal detector. However, the most important non-destructive tools are geophysical sensing devices such as Ground Penetrating Radar  (GPR, see figure 3). These devices actively probe underground by passing various types of energy, laser, or radio waves through the soil and measuring how the waves are reflected back to find out what is below the surface. Passive geophysical sensing devices measure the physical properties of the soil, such as gravity and magnetism. As with LiDAR, these tools capture data that generate a map of what lies below the surface. These highly technical non-destructive subsurface methods require a trained practitioner capable of running the machines over the site and interpreting the resulting data.

Archaeologists can also use probes that physically dig below the surface to learn more about what lies underground. A probe involves using a rod or auger, which looks like a giant drill bit, inserted into the ground to drill down as far as possible into the soil. The auger is then brought back to the surface, carrying with it samples of soil (that may or may not contain artifacts) from various levels below the surface. It is easy to see why this method must be used with caution as it involves plunging a sharp, destructive device into the ground, potentially damaging anything it encounters, including human burials. Another method of physically examining the subsurface is making shovel test pits (Figure 4), which are essentially very small excavations, usually smaller than one meter by one meter in size, to see if there is a potential archaeological site under the surface. Typically, several test pits are opened at the same time at a consistent distance from one another. This method is particularly useful for confirming the results of other forms of reconnaissance, and for identifying buried concentrations of artifacts that are not associated with material culture detectable by subsurface detection tools.

 

Excavation

Excavation is not an easy task. First, it is an expensive proposition in terms of time and financial resources. More importantly, however, it is a destructive technique since the archaeological record is not renewable. If an error is made during the excavation process, the archaeologist cannot undo that work or even redo it—what’s been dug up stays dug up. It is critical that nondestructive methods are used whenever possible and that excavation is used only when there is no other way to gather the data needed to accomplish the research goals. With that said, excavation often offers an important opportunity to gather physical evidence (in context!) of past human activities that can address anthropological questions about past societies.

You have probably seen photographs of excavations, in this text and in other texts and publications, in which the “holes” are square rather than round. Why does the shape of the hole matter? By digging a square hole, archaeologists can easily calculate how many artifacts and other items are present per unit—in this case, a measure of volume.  Inside this square excavation, stratigraphy, the study of layers of soil, is a crucial consideration. Stratigraphic data assist archaeologists in putting the archaeological record into context; the data provide a relative way to date the site and its contents and can provide some contextual clues about cultural and natural formation processes that occurred after the site was abandoned. The next decision is how deep each excavated level will be since the excavation is in three dimensions—length, width, and depth. Some archaeologists elect to tie the depth of each level to the natural strata of the site with each layer representing a level. Other archaeologists select an arbitrary strata depth such as 10 or 20 centimeters regardless of the stratigraphic layers. As excavating proceeds, the material removed is sorted using a screen to recover artifacts, and samples are often collected for laboratory analyses. When excavators reach the bottom of a natural or arbitrary strata level, several things occur. First, the archaeologist typically takes measurements of the depth of excavation across the entire square. The archaeologist then draws sketches of the excavated layer and its stratigraphic profile, and photographs the entire unit, the stratigraphic profile, and important characteristics of the soil to document the stratigraphy. This process continues until the archaeologists have gathered all the information they can from the unit, encounter something unexpected (such as the water table), or come to the end of the project. Before the unit is backfilled, they take high-quality photographs and draw sketches of it.

 

Archaeological Dating Methods

Establishing the age of cultural objects is an important element of archaeological research. Determining the age of both a site and the artifacts found within is key to understanding how human cultures developed and changed over time. Other areas of science, such as paleontology and geology, also use the same dating techniques to understand animal and plant species in the ancient past and how the earth and animal species evolved over time.

Relative Dating

The earliest dating methods utilized the principles of relative dating, developed in geology. This method places objects or events in the order in which they occurred and establishes if something is younger or older than other things at a site. What a relative dating technique will never do, however, is provide an exact dating for an object or event! Geologists developed this technique by observing exposed cliffsides in canyons and noting the layers of different types of stone that they called strata (stratum in the singular). It was hypothesized that the strata at the bottom were older than the strata higher up; this became known as the law of superposition. According to the law of superposition, not just geological layers but also the objects found within them can be assigned relative ages based on the assumption that objects in deeper layers are older than objects in layers above. The application of the law of superposition to archaeological fieldwork is sometimes called stratigraphic superposition. This method assumes that any cultural or natural artifact that is found within a stratum, or that cuts across two or more strata in a cross-cutting relationship, is younger than the stratum itself, as each layer would have taken a long time to form and, unless disturbed, would have remained stable for a very long time. Examples of forces that might cause disturbances in strata include natural forces such as volcanos or floods and the intervention of humans, animals, or plants. If you have ever seen pictures of, or visited the Grand Canyon (Figure 5) in person the effect of these natural forces and the subsequent stratigraphic layering can be easily seen!

 

The law of superposition was first proposed in 1669 by the Danish scientist Nicolas Steno. Some of the first applications of this law by scholars provided ages for megafauna (large animals, most commonly mammals) and dinosaur bones based on their positions in the earth. It was determined that the mammalian megafauna and the dinosaur bones had been deposited tens of thousands of years apart, with the dinosaur remains being much older. These first indications of the true age of fossil remains suggested a revolutionary new understanding of the scale of geological time.

It was eventually determined that if a specific set and sequence of strata is noted in several sites and over a large enough area, it can be assumed that the ages will be the same for the same strata at different locations in the area. This insight enabled geologists and archaeologists to use the structures of soils and rocks to date phenomena noted throughout a region based on their relative positions. Archaeologists call this method archaeological stratification, and they look for stratified layers of artifacts to determine human cultural contexts. Stratigraphic layers found below cultural layers provide a basis for determining age, with layers above assumed to be more recent than those below (see Figure 6).

 

Another method of relative dating utilized by archaeologists relies on typological sequences. Archaeological typologies compare created objects to other objects of similar appearance with the goal of determining how they are related. This method is employed by many subdisciplines of archaeology to understand the relationships between common objects. For example, typological sequencing is often conducted on spearpoints created by Indigenous peoples by comparing the types of points found at different locations and analyzing how they changed over time based on their relative positions in an archaeological site. Typological sequencing can also be done through the process of seriation. Seriation is a relative dating method in which artifacts are placed in chronological order once they are determined to be of the same culture. An English Egyptologist, Flinders Petrie introduced seriation in the 19th century. He developed the method to date burials he was uncovering that contained no evidence of their dates and could not be sequenced through stratigraphy. To address the problem, he developed a system of dating based on pottery. This dating technique using seriation is still very much practiced today, as can be seen in the seriation below of Moche Stirrup-Spout bottles (Figure 7).

 

Typological sequences of pottery, stone tools, and other objects that survive in archaeological sites are not only used to provide dating estimates. They can also reveal much about changes in culture, social structure, and worldviews over time. For example, there are significant changes in stratigraphy during the agricultural age, or Neolithic period, at around 12,000 BCE. These changes include the appearance of tended soils, pollens that indicate the cultivation of specific plants, evidence of more sedentary living patterns, and the increased use of pottery as the storage of food and grain became increasingly important. Archaeological evidence also shows a growing population and the development of a more complex cultural and economic system, which involved ownership of cattle and land and the beginning of trade. Trade activities can be determined when pottery types associated with one site appear in other nearby or distant locations. Recognizing the connections between objects used in trade can shed light on possible economic and political interrelationships between neighboring communities and settlements.

Absolute/Chronometric Dating Methods

Chronometric dating methods, also known as absolute dating methods, are methods of dating that rely on chemical or physical analysis of the properties of archaeological objects to provide a specific date or date range for the object. Using chronometric methods, archaeologists can date objects to a range that is more precise than can be achieved via relative dating methods. Radiocarbon dating, which uses the radioactive isotope carbon-14 (14C), is the most common method used to date organic materials. Once a living organism dies, the carbon within it begins to decay at a known rate. The amount of the remaining residual carbon can be measured to determine, within a margin of error of 50 years, when the organism died. The method is only valid for samples of organic tissue between 300 and 50,000 years old.

Other kinds of absolute dating systems can measure the atomic decay of uranium ( Uranium–uranium dating) or the decay of potassium into argon (potassium-argon dating), and can be used to date nonorganic materials such as rocks. The rates of decay of radioactive materials are known and can be measured. The radioactive decay clock begins when the elements are first created, and this decay can be measured to determine when the objects were created and/or used in the past. Volcanic materials are particularly useful for dating sites because volcanoes deposit lava and ash over wide areas, and all the material from an eruption will have a similar chemical signature. Once the ash is dated, cultural materials can also be dated based on their position relative to the ash deposit.

The technique of dendrochronology relies on measuring tree rings (Figure 8) to determine the age of ancient structures or dwellings that are made of wood. Tree rings develop annually and vary in width depending on the quantity of nutrients and water available in a specific year. Cross dating is accomplished by matching patterns of wide and narrow rings between core samples taken from similar trees in different locations. This information can then be applied to date archaeological remains that contain wood, such as posts and beams. Dendrochronology has been used at the Pueblo Bonita archaeological site in Chaco Canyon, New Mexico, to help date house structures that were occupied by the Pueblo people between 800 and 1150 CE. The Laboratory of Tree-Ring Research, based in Tucson, is the world’s oldest dendrochronology lab. Go on a tree-ring expedition (https://openstax.org/r/tree-ring)!

 

The most effective and ideal approach for dating archaeological objects is to apply a variety of dating techniques, assuming that funding can be found! Applying more than one dating method allows the archaeologist to triangulate or correlate data. Correlating multiple methods of dating provides strong evidence for the specific time period of an archaeological site.

Terms You Should Know

Context

Research Design

Cultural Resource Management

Elements of research design

Implementation Phase

Non-intrusive tools

Artifacts

Geographic information system (GIS)

Folsom point

Aerial reconnaissance

Earthworks

LiDAR

Space Archaeology

Ground reconnaissance

Subsurface detection tools

Remote sensing

Ground Penetrating Radar

Study Questions

1. Why are assumptions made about the formation of stratigraphy important for archaeologists?
2. What are the differences between absolute and relative dating techniques?
3. How have technological changes altered the accessibility and affordability of aerial reconnaissance in archaeology?

References

Fagan, B. M. 2006. Archaeology: A brief introduction. Upper Saddle River, NJ: Pearson Prentice Hall.

Marchant, Jo. 2019. Adventures of a space archaeologist. Nature. https://www.nature.com/articles/d41586-019-01972-3

Nash, Stephen E. 2017. How the Folsom Point Became an Archaeological Icon. Sapiens. https://www.sapiens.org/column/curio…haeology-icon/.

Peeples, Matt. 2015. George McJunkin and the Discovery That Changed American Archaeology. https://www.archaeologysouthwest.org/2015/02/23/george-mcjunkin-and-the-discovery-that-changed-american-archaeology/

Stewart, Tamara Jager. 2017. Charles Lindbergh’s Little-Known Passion. American Archaeology, 21(2): 18-27.

A derivative work from

Paskey, Amanda Wolcott and Cisneros, AnnMarie Beasley. 2020. Digging into Archaeology: A Brief OER Introduction to Archaeology with Activities. ASCCC Open Educational Resources Initiative (OERI).

Scheib, Crystal. 2023. Archaeology: It’s More Than Digging in the Dirt. LibreTexts