Stratigraphy (archaeology)
Stratigraphy is a branch of archeology and helps with the relative age determination of archaeological deposits. As archaeological stratigraphy is defined as the detectable during an excavation in a vertical profile sequence of strata (Latin stratum, Pl strata to sternere " spread ", " layer " ) caused by natural and anthropogenic deposits and construction ( embankment, ditch, manhole, well, post hole, grading, backfilling, etc.) has emerged.
- 4.1 correlation
- 4.2 phase position and stratigraphic sequences
Research Historical Background
The Danish scientist Nicolaus Steno ( Nils Stensen ) grew in 1669 with the Stratigraphic Basic Law, the basis of stratigraphic observations in geology. To aid in the assessment of marine sedimentary rocks came to his knowledge of the Glossopetrae (fossil shark teeth, so-called " tongue stones " ) from the Danish collection. For a stay in Florence in 1666 he was allowed to dissect a recently caught on the coast shark. In the examination of the teeth he came to the conclusion that the Glossopetrae are fossilized shark teeth. From this he concluded that the " tongue stones " marine deposits represent and, consequently, is the surrounding sedimentary rocks of marine origin. Steno is considered as the founder of the stratification in the historical geology.
Another major player was the English engineer and geologist William Smith ( 1769-1839 ). He could see a recurring sequence of layers with the fossils contained in them in canals in southern England. His discovery laid the foundation for the strategy chronological correlation by means of the associated fossils. So Smith recognized that two strata with the same number and similar fossils must be at the same time.
The Scotsman Sir Charles Lyell (1797-1875) also played a crucial role in the history of stratigraphy. In his famous three -volume work, Principles of Geology he managed a relationship between fossils that have been found in layers and the present-day organisms. He showed that it is possible to identify a smaller number of fossils with extant species in older layers and vice versa: the number of identifiable with today's living species fossils is significantly greater in younger strata. With Steno 's, Smith's and Lyell's geological knowledge, the basis for the stratigraphy had been created.
Among these was then the English geologist James Hutton (1726-1797), who formulated the principle of uniformitarianism. This principle states that the geologic processes that can be observed today is basically no different from those who were active in earlier geological times. Thus one could draw conclusions about past geological activities and processes based on current observations. The time between each stratigraphischenen activities called Hutton unconformity or interface. Since the geological epochs were measured in millions of years, of course this caused a controversy with the Biblical idea that the world is 6,000 years old. This dispute was resolved by the invention of radiometric dating, which measures the time or the duration of the interfaces just mentioned.
During the 19th century the principle of stratigraphy has been used in connection with cultural layers. Leading the way especially the Danish archaeologist CJ Thomsen (1788-1865) and JJA Worsaae (1821-1885) were also the excavator of Troy, Heinrich Schliemann ( 1822-1890 ). Thus, the stratigraphy was also enshrined in archeology.
Axioms of stratigraphy
In stratigraphy, there are four laws that were first formulated specifically for EC Harris in 1979 for archeology:
- The Stenosche storage law (law of superposition )
- The law of original horizontality (law of original horizontality )
- The law of original continuity (law of original continuity )
- The law of the stratigraphic sequence (law of stratigraphical succession )
The Stenosche storage law states that in the process of deposition layer follows layer and thus in an undisturbed sequence of layers, the upper layers are younger than the lower ones.
The law of original horizontality states that unconsolidated soil, tends mainly due to gravity, to align horizontally.
The law of the original continuity indicates that each layer is defined by a natural surface mold and gradually runs out into the thin ends.
These first three rules have been formulated in the geology of Steno, however, the fourth law in archeology has been developed. It expresses that one to be examined layer is determined by its position between the upper ( younger ) and the lower (older). Thus, any relationship with other layers can be neglected, since only the stratigraphic units that have a direct contact with the layer to be tested for these by importance.
Stratification and Strata
Stratification
The process of stratification consists of two components: erosion and accumulation. Loose rocks erode always downward and accumulate in a Ablagerungsbasin ( accumulation ), through which thereby forming strata are limited. Such limitations can be Bette old rivers, military trenches and walls and walls of houses.
However, new layers are created not only by natural processes, but also by human activities, such as digging. Digs you a hole in the ground, piling you scooped out to the earth, which in turn erodes over time and spreads horizontally. Thus, the archaeological stratification is an interplay of natural processes of erosion and deposition and human changes to the landscape.
When stratification, nature always seeks the path with the least resistance. Thus eroded soft, unconsolidated material first, the process is faster, can the more easily eroded material. Strata of human origin depend solely on the cultural preferences of the people. You are not bound by this rule. People can ignore the limitation of the aforementioned Ablagerungsbasins ( and by digging their own create ). Nature is not in a position. You must follow the topography and contours ( exceptions include volcanic eruptions ). It is a process in which particles down towards the sea are transported. The natural transport of geological material thus depends on the force of gravity. For example, break rocks from a larger formation and fall down. Further erosion as well as wind and water forces carry away small fragments of this rock until they also lose their energy and are the particles themselves to rest. If the transport thus ends, the deposit begins.
Another example is the gradual disintegration of walls. If these or if a trench is filled by erosion own decay and collapse, the nature of the carrier of this material for deposition site. If a trench is however filled with household garbage, man transported.
Strata
There are two types of people created layers: horizontal and vertical strata. Vertical strata may be as walls or walls. All three types of layers, the natural horizontal, the people created horizontal and vertical layers have in common is that they all have one upper and one original (lower ) surface. However, vertical strata have not only horizontal surfaces, but also those that are vertical. Edward Harris warns in his book Principles of Archaeological Stratigraphy (1979 ) before digging at an archaeological dig ditches around this vertical strata, as this would destroy the vertical relationships. Stratigraphic relationships between layers are in fact created by the deposition of new layers to existing layers. The deposits are located on the vertical surfaces of the upstanding Straten, therefore, also have relations. All stratigraphic units therefore have surfaces.
Boundary and Surface Contours
There are two kinds of contours, having a layer. The boundary contours and the surface contours. The former are outlines that define the spatial extent of a stratigraphic unit in horizontal and vertical dimensions. Surface countours other hand, show the topographic relief of the surface of a layer. This type of contours but usually shown only in plans, not in profiles. Furthermore, all stratigraphic units have a certain position in the sequence stratigraphy of a. This provides a relative position of age, compared to the other units in the same sequence. The exact age of a layer that is measured in years, but often can not be determined without datable artifacts. Chronological data, as a stratigraphic unit also, do not change their position in the stratigraphic sequence. However, many of these data appear contradictory to the rest of the sequence. For this is the already mentioned Edward Harris a simple example, which was formulated by the Scotsman Sir Charles Lyell:
"Even in cities,: such as Venice and Amsterdam, it can not be laid down as universally true, did the upperparts of each edifice, of brick or marble Whether, are more modern than the foundations on Which They rest, for thesis Often Consist of wooden piles, Which june have rotted and been Replaced one after the other, without the least injury to the building above; meanwhile, thesis june have required scarcely any repair, and june havebeen Constantly inhabited. "
In this example, the foundation of new, than the overlying structure of the house appears. This problem can also occur in the stratigraphy.
The interface
There is a fundamental distinction between the three types of interfaces, which are explained in this chapter. Layer interface is referred to as the surface a layer that was deposited horizontally, and the vertical surfaces of an upright layer. The extent of the layer interface is as usually large as that of the layer itself These interfaces have the same stratigraphic relations as their layers, which is why they are given in sections drawn the same number and it is recognized as part of the deposits. In upstanding layer interfaces no surface contours can be recorded only boundary contours. Horizontal layer interfaces, however, have both boundary and surface contours. Both types of the layer interface label the time that has elapsed between the formation of a particular layer and their funeral.
The feature interface arises due to destruction of existing deposits. They have their own stratigraphic relations, surface and boundary contours, and should therefore have its own number when you create a profile of the associated stratigraphy. Horizontal feature interfaces are associated with upright Straten and identify the levels at which such strata have been destroyed. Vertical feature interfaces, however, are the result of the trench pits and trenches. The layers at the bottom of the pit are located on a lower level than other contemporaneous deposits outside the pit. Thus, this is the bottom of a pit or a trench located layers have relations to other stratigraphic units of a much younger age.
The period interface is expressed quite simply, the interface or the "border" between two periods or phases. This may be prehistoric, historical, constructive and deconstructive phase, for example, settlement phases.
Correlation, phase and stratigraphic sequences
Correlation
Strata can stand on three ways in relation to each other. Two layers can either does not have direct contact, are located one above the other, or they can be used as parts of the same original layer was separated, for example by a moat, occur. These relations may, however, be clearer and thus easier represented using the so-called Harris Matrix in a stratigraphic profile or.
However, must be recorded in a Harris matrix not all relations between all strata. According to the law of the stratigraphic sequence (law of stratigraphical succession ) are relevant to only a stratum with the relations for the next higher and the next lower layer. Thus, the Harris matrix can be reduced to the essentials.
Phasing and Stratigraphic sequences
The goal of a stratigraphic investigation is called a sequence to create. This is to study nothing else than the existing Straten, bringing in conjunction with each other and finally record. Stratigraphic sequences are represented by profiles. If a sequence has been recorded, you can start with the development of the phase angle or the division of the sequence into periods. These strata are belong together in phases combined, represent a geohistoric or cultural-historical period, such as the period in which at a certain point one culture settled ( settlement period ) or in has occurred another event, such as the excavation a trench or the like.