Archaeological Methods and equipment

Archaeological Methods

Written Documents; Historical accounts that provides evidence of human past history. Written documents include Books, Journals, Monographs, Magazines/News papers, Dissertations e.tc.

Oral Traditions

Ø  These are oral accounts about human past or history.  These are narratives and descriptions of people and events in the past. It mainly involves face to face narratives of various human events.

Archaeological survey

Ø  Archaeological survey is the systematic attempt to locate, identify, and record the distribution of archaeological sites on the ground and in relation to their natural environment. The main aim of archaeological survey is to identify individual sites for excavation.

Ø  Archaeological survey is one of the most important components of archaeological investigation, for it is concerned with the archaeological record of ancient settlement patterns, with ancient people’s traces on the land. An archaeological survey seeks to identify ancient landscapes, which are far more than merely site dots or settlement patterns plotted on a map.

Ø  There are two types of survey;

1. Reconnaissance survey
2. Intensive survey

Ø  Reconnaissance survey / Surface survey; this is just a preliminary examination of a survey area to identify major sites, to assess potential, and to establish tentative site distributions. This involves background research e.g. examining archives and historical accounts, talking to people and acquiring general environmental information.

Ø  Intensive survey/ sub-surface survey/total survey: is a systematic, detailed field survey that covers an entire area. It may include subsurface testing (i.e. Test Pit excavation) to be sure of the archaeological significance of the respective area.

Survey whether intensive or reconnaissance may be conducted (1) Systematic or (2) Unsystematic.

ü  Systematic survey; this involves the use of grid system so that each section is attentively investigated. The surveyed area is usually divided into sectors and these are walked systematically. Most modern survey is conducted systematically. This involves mapping and surface collection.

ü  Unsystematic survey; involves field walking and recording the locations of artifacts and surface features. It does not involve systematic land walkover due to topographic features of the landscape.

Archaeological Excavation

Archaeological excavation is the principle method of data acquisition in archaeology. It involves the systematic recovering of archaeological remains through the removal of the deposits of soil and other material covering them.

Objectives of Archaeological excavation

Archaeological excavation is very important because it yields the most reliable evidence for the two main kinds of information archaeologists are interested in:

(1) Human activities at a particular period in the past

(2) Changes in those activities from period to period.

To achieve this, archaeologists are ought to study their sites in terms of relationship of the materials in space and time. Thus the relationship of the materials horizontally in space and vertically through time are very important.

Such a study is facilitated by two principles; i.e. principle of association and the principle of superposition.

The Principle of Association

The law states that, objects, features and structures found in the same horizontal plane are associated and contemporary. For example, in an excavated layer in which there are remains of houses, storage pits and artifacts, it can be argued that because of their horizontal relationship such finds are associated to each other. The archaeological principle of association was first stated by Danish archaeologist J. J. A. Worsaae when he was excavating prehistoric burials in 1843 (see Fig 6.3)

The Principle of superposition

This states that geological layers of the earth are stratified one upon the other like the layers of a cake. Therefore, any object found in the lowermost levels, whether a stone or something humanly made, was deposited there before the upper levels were accumulated. In other words, the lower strata are earlier than the upper strata.

The same principle applies to archaeology because archaeological sites are formed under the same principle. Archaeological objects are made and discarded. These are then covered by deposits mostly due to natural processes. Therefore an archaeological site which has been occupied at different periods will contain successive layers of such occupations, with earliest occupation overlain by layers of later occupations. Therefore tools, houses, and other finds in one layer of a site can be dated relative to the other layers (see figure 6.3). The basis of all scientific archaeological excavation is the accurately observed and carefully recorded stratigraphic profile.

Types of excavation

(1)   Total excavation and (2) Selective excavation

Total excavation refers to the rescue exercise which involves the digging of the whole site.

This is a comprehensive work. It is very expensive and undesirable as it leaves none of the site intact for future research.

Selective excavation; this is opposite to total excavation. An area is selected for excavation through the use of sampling methods. This method is used to obtain stratigraphy and chronological data.

Methods of excavation

There are two methods of archaeological excavation; Vertical Excavation and Horizontal Excavation.

Vertical Excavation

This method is basically employed when the main objective is to reveal the chronological sequence of the site. Vertical excavation is used to establish stratigraphic sequence, especially in sites where space is limited, such as small caves and rock shelters, or to solve chronological problems, such as the sequences across sets of ditches and earthworks. Under this method of excavation, test pits are frequently used form of vertical excavation.

They consist of small trenches just large enough to accommodate one or two diggers, and are designed to penetrate to the lower strata of a site to establish the extent of archaeological deposits.

Horizontal/area Excavation

Horizontal, or area, excavation is done on a much large scale than vertical excavation and is the next thing to total excavation. This method covers a wide area to recover building plans or the layout of entire settlements, even historic gardens. A major problem with this method is stratigraphical control especially in sites with several periods of occupation. To minimize this problem the area to be excavated is divided into a grid squares with walls several meters thick between each square.  However, a large scale excavation with grids is expensive and time consuming.

Excavation Equipments/tools

Trowels

Small plastic bags to hold the artifacts from each layer

Waterproof black markers to label the bags

 Pencils

Brushes

 Record sheets

 Clipboards

Small sieves

Tape measures

Mapping machine (Full set)

Machete

Common Dating Techniques

Archaeological investigations have no meaning unless the chronological sequences of the events are reconstructed.  The real meaning of history is to trace the developments in various fields of the human past.  Towards this end, while investigating the past cultures, archaeology depends on various dating methods.  These dating methods can broadly be divided into two categories;

1.  Relative dating methods and

2. Absolute dating methods

Relative Dating Methods

These are mainly non-scientific dating methods. These methods were relied on especially prior to the introduction of scientific methods of dating. However, even when the scientific methods of absolute dating are available, this method of dating has not lost its importance because many archaeologists still depend solely on relative dating.

The various methods of relative dating are as follows:

o   Stratigraphical sequence

Stratigraphy is the study of the arrangement of cultural layers (also called deposits) one above the other. From the point of view of relative dating, the important principle is that the underlying layer was deposited first and therefore older than the overlying layer. According to this method, the upper deposits are younger and the lower deposits are older. Therefore, archaeological artifacts found in the lower deposits are older than those found in the upper deposits. Therefore good stratigraphic excavation at an intact archaeological site is designed to obtain such a sequence.

o   Associations

When a group or types of objects are found together in the excavated layers they are said to be associated. It is nearly always association with other phenomena that gives a first clue as to the use, the age and chronological attribution of a potential date. In general if there has been no disturbance and mixing up, the various artifacts found in a layer should, when excavated, offer not only a relative dating of the layers but also human activities contained in those layers.

o   Typological sequences

Typology is a classification system based on the comparison of type of artifacts. Typological sequence therefore, can be used to establish relative chronological sequences because of the two basic assumptions;

a.       Artifacts of the same period and place have a recognizable style and that their distinctive shape and other attributes are characteristic of the society that produced them.

b.      The change in the style of artifacts is normally gradual or evolutionary. Therefore, artifacts made at the same time are alike and those made later will be different due to stylistic change through time.

Absolute /Chronometric Dating

Before 1950’s archaeologists depended on relative dating techniques for establishing chronological sequences. These sequences could only tell which artifacts or cultures are older or later than others and which are contemporary.

Beginning the 1950’s a number of chronometric or absolute dating techniques have been developed for dating the past. Absolute dating therefore is the determination of age with reference to a specific time scale, such as fixed calendrical system.

There are several methods of Absolute Dating;

1. Radio Carbon Dating

This is one of the most important methods of dating the ancient objects which contain some carbon in them.

There are three heavy isotopes of carbon; C12, C13, and C14. C12 is the most common forms of carbon and C13 are stable and can be used to reconstruct ancient diets. C14 is unstable isotope. It is known as radiocarbon and it decays at a known rate. This allows it to be used for dating.

Carbon 14 is produced in the atmosphere and is absorbed by plants through carbon dioxide in the process known as photosynthesis. Carbon 14 enters animals when they eat plants. The proportion of C14 in an organism remains constant until its death. Until that time no further C14 is taken in.

The radioactive carbon present at that time undergoes its normal decrease through the process of radioactive decay.

For example, the time taken for half-life of a radioactive to decay can be measured and is called half life. In case of C14, the half life is 5,730 years. Therefore bone remains, charcoal hair skin and other organic materials can be used for carbon 14 dating. Carbon 14 can only be used to determine age sample not older than 50,000 years.

2. Dendrochronology

Dendrochronology is a method that uses tree-ring analysis to establish chronology. This method is also called Tree-Ring Dating Method.

Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year.

Often, the tree-ring analysis from a site can give strong clues about the length of occupation, certain periods of building or repair activities at the site. Another application of tree-ring analysis is the inference of past environmental conditions, which is extremely useful to the archaeologists.

3. Potassium – Argon dating
4. Uranium series dating
5. Archaeomagnetic dating
6. Obsidian hydration
7. Fission Track dating