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Study of Archaeological Stratigraphy and the process of excavation. What is Harris Matrix and the laws of it.
In archaeological studies, making of stratigraphic sequences and their periodisation
are the most important task for any excavator. The study of archaeological stratigraphy has
undergone a change through the years. In initial stage, due to the influence of geology much
importance was given to the theories, stratigraphic laws and units of stratification. In the
second stage, attention was paid to archaeological stratigraphy and much attention is given
in recording the sections and plans. Lastly, but very recently, in addition to the section and
plan drawings, post excavation-analysis took central stage in all archaeological studies.
The character of the stratification of a particular archaeological site will depend
upon the historical and cultural circumstances in which it was created. It related to sites in
which the stratification is predominantly of human origin. The interpretation of
archaeological sites is governed by the principles of geological stratigraphy. Some
archaeologists think that geological principles of stratigraphy are adequate for the study of
archaeological sites which are man made stratification. Edward Harris strongly advocates
that archaeological stratigraphy differ from ecological stratigraphy. He felt that when
humans made their debut on the earth, a revolution occurred in the process of stratification
which had been carried out until then by natural agencies. This great change had at least
three major aspects:
first, mankind began to manufacture objects which did not confirm to the process of
organic evolution through natural selection;
• secondly, humans began to define preferential areas of use of the Earth's surface;
• thirdly, people began to dig into the earth, by cultural preference, rather than by instinct,
which eventually altered the stratigraphic record in a non-geological manner.
This revolution separates archaeological from geological stratigraphy, the cultural
from the natural. The stratigraphic signature of the human life become less geological and
more man made when the societies moved from simple to complex or rural to urban. With
prolific industrialization and vast urbanisation, the rate of deposition and degradation
increases manifold in human cultural activity. Due to these activities, now the
archaeologists have started questioning the application of geological stratification directly
upon the archaeological stratification. Some of the archaeologists are still attempting to
unravel archaeological stratification according to rules which were devised over a century
ago for the study of strata formed under sedimentary conditions many millions of years
ago. The origins and development of archaeological ideas have been admirably discussed
in Glyn Daniel's book, A Hundred and Fifty Years of Archaeology, published in 1975.
Until the latter part of the nineteenth century, geology had a great influence on the growth
of archaeological concepts. Even up to the early part of the present century, stratigraphy in
archaeology was primarily seen in a geological light, although many excavators were
examining sites with little or no geological strata. In this chapter, several of the early
archaeological discoveries will be examined from a stratigraphic point of view. Later in the
chapter, more recent ideas of archaeological stratigraphy are discussed. These
archaeological ideas are noted in relation to geological notions of stratigraphy.
Phillips et al. (1951) have provided both a succinct definition of stratigraphy and a
useful distinction: stratification is what you find; stratigraphy is what you do with it. To
properly understand a site's stratification, an archaeologist must combine the law of
superposition with a consideration of context.
As already noted, the term and the basic method come from geology. Some of the
basic assumptions, such as uniformitarianism, come from geology, too. Uniformitarianism
is the assumption geologists make of uniformity or continuity in the processes that form
the strata of the earth. The processes that acted in the past are like those we can observe
today. In other words, when volcanoes erupt today, they lay down layers of ash. Geologists
assume that ancient volcanoes did the same. An excellent example of ancient volcanic
stratigraphic deposition is reported by Sheets (1983, 1992) for the Ceren site in El Salvador.
Similar are the depositional effects from flooding by rivers (known as alluvial deposits).
Deposits laid down by other natural forces include colluvial, aeolian, glacial, and marine
Archaeologists also assume that human behaviour is much the same today as it ever
was. For example, most modern communities have a dump for their rubbish and garbage.
Archaeologists routinely encounter mixed deposits whose likeliest origin seems to be their
having served as the trash heap of a prehistoric people. A. V. Kidder, digging into the
Andover, Massachusetts, town dump in 1922, found layering and change there that was
markedly similar to what he found in the much older trash deposits at the prehistoric
Southwestern ruin of Pecos.
The concept of Stratigraphy in Archaeology Several formative periods in the
development of archaeological stratigraphy may be perceived. Frere, Thomson, Worsaae,
Wheeler, Kenyon and Kidder refined the archaeological stratigraphy to the present state
through their intensive observation of various archaeological sites. Glyn Daniel in his book,
“A Hundred and Fifty Years of Archaeology (1975)” admirably discussed the origins and
development of archaeological thought and also explained the influence of geology in
archaeology, particularly in stratigraphy. For instance, the stratigraphical position of
prehistoric artefacts was not given till the mid 18th Century.
Stratigraphy took its root with the formulation of the principles of stratigraphy and
its acceptance by the geologist and archaeologist. C.J.Thomsen advocated in his book
Three Age System”, in which human passed the three technological stages namely stone,
bronze and iron. Thomsen's successor J.J.Worsaae proved this transformation with
stratigraphic validity. Though this Three Age System looks extremely simple it gave
considerable depth to the chronology of human past. Again, the Stone Age was further
classified into palaeolithic and neolithic by Sir John Lubbock. This way archaeological
layers containing peculiar items to each stratum helps to identify deposits of same date in
other locations. The identification of cultural material in this manner is considered as a
revolution in antiquarian thought. Nevertheless, independent archaeological stratigraphy
did not develope but lingered on geological stratigraphy throughout the nineteenth century.
In the 1920s, Mortimer Wheeler began to produce section drawings in the reports which
have been considered as landmark in archaeology. In continuation of Wheeler's tradition,
his student Kathleen Kenyon further improved it by including the things like pits, ditches
and other types of interfaces.
Wheeler and Kenyon provided two essential ideas to the theory of archaeological
stratigraphy, namely: the value of interface and the numbering of layers. These concepts
have been expressed in Wheeler's book Archaeology from the Earth (1954)” and Kenyon's
book “Beginning in Archaeology (1952)”. This becomes the backbone of stratigraphy and
it is popularly known as Wheeler-Kenyon system of archaeological stratigraphy and this
continued for a longer period. This Law of Superimposition has never been questioned or
revised until recently despite the great difference between consolidated sedimentary strata
of geological site and unconsolidated man-made. strata of archaeological site. Edward
Harris is the one who questioned the application of geological law into the archaeological
Harris Matrix
Edward Harris in his book “Principles of Archaeological Stratigraphy (1979)
devised a new method in archaeological stratification which is popularly known as Harris
matrix which was, in fact, invented in 1973. He questioned the application of geological
laws namely Law of Superposition, Original Horizontality, Original Continuity and
Stratigraphical Succession without any revision in archaeological stratigraphy. He felt that
geological laws are no longer suitable for most archaeological purposes and must be
augmented by our own standards.
The following are the Laws of Archaeological Stratigraphy devised by Harris after
making certain revision in the geological law.
The Law of Superposition
In a series of layers and interfacial features, as originally created, the upper units of
stratification are younger and the lower are older, for each must have been deposited on, or
created by the removal of, a pre-existing mass of archaeological stratification.
In archaeological stratigraphy, the Law of superposition must also take account of
interfacial units of stratification which are strata in a strict sense. These interfacial units of
stratification may be seen as abstract layers and will have super-positional relationship with
strata which lie above them or through which they were cut or lie above.
The Law of Original Horizontality
Any archaeological layer deposited in an unconsolidated form will tend towards a
horizontal position. Strata which are found with tilted surfaces were originally deposited that
way, or lie in conformity with the contours of a pre-existing basin of deposition”.
This section drawing, made by Mortimer Wheeler in 1934, is one of
the earliest to contain 'layer numbers' (from Wheeler 1943
In geology, the Law of Original Horizontality assumes that when deposits formed
by sedimentary process underwater or in the dry-land conditions, the strata will tend
towards the horizontal. In archaeological stratigraphy one must consider both the dry-land
conditions and man-made deposits. In horizontal surface, deposits are made in horizontal
position. If a basin of deposition is a slope or a ditch then the deposition will be in a tilted
position. As the filling of the ditches or slopes progresses, the deposits would gradually
approach the horizontal position. There are other possibilities also, after the deposition, the
land may tilt due to some other causes like earthquake. Therefore, archaeologists should
take care of the significant interfacial features.
The Law of Original Continuity
Any archaeological deposit, as originally laid down, or any interfacial feature, as originally
created, will be bounded by a deposition, or may thin down to a featheredge. Therefore, if any
edge of a deposit or interfacial feature is exposed in a vertical view, a part of its original extent
must have been removed by excavation or erosion, and its continuity must be sought or its
absence explained.
This law may be expanded in two ways, one for the down-going feature and another
for the upcoming feature. The first is its application to interfacial features which are
considered to be units of stratification, such as ditches. If such feature appears in a vertical
view, a part of its original context may be assumed to have been destroyed. In the second,
the upstanding strata like wall will survive to the level of its truncation. The ditch and the
wall both must be treated as an interfacial unit of the stratification. In geology, the
accumulation of deposits is like a deck of cards whereas in archaeology these unilinear or
deck-of-card sequences cannot be applied, as they are man-made deposits.
Law of Stratigraphical Succession
A unit of archaeological stratification takes its place in the stratigraphic sequence of a
site from its position between the earliest (undermost) of the units which lie above it and
the latest (uppermost) of all the units which lie below it and with which the units has a
physical contact, all other superpostional relationships being redundant”.
Most archaeological sites have multilinear sequences with presence of upstanding
strata (features) and other interfacial features. The upstanding (wall) and interfacial
(pit/porthole) features create new basins of deposition within which separate sequences
accumulate. These characteristics go against the simple correlation used in geology. To
mitigate the deficiency that found is in geology, Harris developed a method by which
stratigraphic sequences can be diagrammatically expressed in very simple terms in
archaeological studies.
The Harris Matrix and Stratigraphic Sequences
When constructing the stratigraphic sequence the Law of Superposition is of
paramount importance. It is this law that provides a body of stratification with its
chronological direction. The question thus posed about strata is which came first? And
consequently the units of stratification can be placed in sequential order in relative time,
one after another.’ (Hams, in Fagan, 1996). During site excavation the Harris Matrix
provides archaeology with a method, one which enables stratification sequences to be,
using simple terms, displayed as a diagram.
The Harris Matrix comprises a grid, on paper, of rectangular boxes. Its format is
designed to show the stratigraphic relationships found on site. The matrix is the resulting
diagram and represents the excavated stratigraphic sequence. The stratigraphic sequence is
therefore the order of deposition of layers and the creation of feature interfaces through the
course of time.’ (Harris, in Fagan, 1996). This order is interpreted using the first three laws
of archaeological stratigraphy. However, the translation of these relationships that are
uncovered are achieved using the fourth law, that of stratigraphical succession. The matrix
sequential diagram thus builds up on the paper grid as the excavation progresses. The
placing of layers and other features in sequential order thus becomes the main objective of
the matrix.
Excavated strata cannot be dated realistically without examining the remains found
in the deposits. The dating of strata and artefacts can be inferred once the stratigraphic
sequence has been determined. From this cart be calculated the date of origin of an artefact,
its main period of use, and then the date or time of its deposition. Three questions can thus
be posed for the time an artefact has lain in a stratum. The aim of analysing found artefacts
is to date found layers and interfaces, based on the stratigraphic law of superposition of
strata. By way of this method the aim is to relate stratigraphy to chronology.
The Harris Matrix is therefore a method of straigraphic recording, of an excavation
site, where each deposit is allocated a number. Each deposit can be seen as a time capsuleor
unique indicator of evidence encompassing cultural, environmental, and chronological
data. The stratigraphic analysis gives a relative scale, a stratigraphic time that is established
during excavation and recording. The study of found artefacts gives an absolute date or
calendar time. For the Harris Matrix stratification presents as a three-dimensional body of
deposits and features `…from which a fourth dimension of relative time can be inferred…’
(Harris, in Fagan, 1996), thus the stratigraphic sequence, the order in relative time, of
thedeposition of layers and the creation of interfacial features. (Harris, in Fagan, 1996).
This, via the Harris Matrix, is translated into an abstracted diagram.In this way the Harris
Matrix system can readily cope with deeply stratified excavations, an example would be
York, and other rescue operations within urban environments. The Harris Matrix did not
deny the validity of the stratigraphic ideas of Sir Mortimer Wheeler. The Harris Matrix
systematised these ideas by referring to units of stratification rather than layers or strata,
especially with stress upon interfacial features.
Stratigraphy in Archaeology
Archaeological excavation sites vary according to soil features and material culture
content, depth and extent of stratified deposits. Stratigraphic sequences also show varying
examples on non-historical objects. Firstly, indigenous remains are those from the time of
layer formation, which implies objects and the layer are contemporaneous. Secondly,
residual remains are objects made during a time a time prior to the formation of the layer.
This suggests such objects were present in earlier layers but were dug up or disturbed
subsequently. Thirdly, infiltrated remains arethose created at a later date than the layer
formation. Archaeological stratification is therefore a layering of deposits due to human
activity, whereas archaeological stratigraphy is the chronological and sequential
relationships between the deposits, strata, and associated interfaces. Using the Harris
Matrix helps to determine the cultural history of a site by recording the sequences in a
diagram. The essence of the Harris Matrix system is the placing of each unit (on the
diagram) in its stratigraphic place in relation to features above and below. A Harris Matrix
diagram therefore illustrates and encapsulates the archaeological site record within one
Finally, artefactual analysis has to contextualised during and after an excavation. It
is not simply placing an artefact or object in a stratigraphic sequence. The describing,
drawing, and handling an artefact from a stratum may avoid the making of interpretations.
This process may miss important details and overlook that beyond individual artefacts there
is a context. So, stratigraphic sequences and the Harris Matrix system enable questions to
be asked, was the artefact found in a well, a grave, a ditch? In addition how did it end
up there and why? What other artefacts were associated with it? Were associations ritual,
mundane and everyday, or with,‘ richer finds? Unless artefacts are placed in the
archaeological record in this way the artefact will become decontextualised. Taking an
artefact out of its topographical, geographical, social and historical context leaves it
orphaned. If it is lifted out of time it is disembodied with its physical circumstances denied.
In this sense the Harris Matrix is a means whereby artefacts and sites remain dynamic rather
than become passive objects and open to all manner of inaccurate personal interpretations.
i. K. Rajan, Archaeology: Principals And Methods, Manoo
Pathipakkam, Thanjavur, 2002.
ii. Thomas R. Hester, Harry J. Shafer, Kenneth L. Feder, Field
Methods in Archaeology, Routledge Taylor and Francis Group,
London, 2009.
iii. Philip Barker, Techniques of Archaeology Excavation, Routledge
Taylor and Francis Group, London, 1993.
iv. K. V. Raman, Principles and Methods of Archaeology, Parthajan
Publications, Madras, 1986.
v. Herbert D. G. Maschner, Christopher Chippindale, Handbook of
Archaeological Methods, Vol. I, Altamira Press, New York, 2005.
vi. Edward C. Harris, Principles of Archaeological Stratigraphy,
Academic Press, London, 1997.
ResearchGate has not been able to resolve any citations for this publication.
Philip Barker's survey of current excavation techniques - at once authoritative and stimulating - was immeadiately hailed as the standard work and is one of the most widely used archaeological field manuals.
  • K Rajan
K. Rajan, Archaeology: Principals And Methods, Manoo Pathipakkam, Thanjavur, 2002.
  • Thomas R Hester
  • Harry J Shafer
  • Kenneth L Feder
Thomas R. Hester, Harry J. Shafer, Kenneth L. Feder, Field Methods in Archaeology, Routledge Taylor and Francis Group, London, 2009.