Navigating Excavation Decisions in Commercial Archaeology: Insights and Techniques

Commercial archaeology, a field that intersects with construction projects, plays a crucial role in preserving and understanding our historical heritage. While it can often be a challenging and meticulous process, it is essential to ensure that archaeological sites are protected and studied before major construction endeavors occur. The decision of what areas to excavate, and how deeply, requires a deep understanding of several factors, including the geology, topography, and potential archaeological remains.

The Process of Stratigraphic Excavation in Commercial Archaeology

Commercial archaeologists often face a variety of conditions and challenges when undertaking excavations. One common method involves the removal of topsoil by machine. This process is essential as it helps to reveal the underlying layers and potentially important archaeological features. The depth of topsoil can vary widely depending on the local geology, farming practices, and other factors. Despite these variable conditions, the key objective remains to uncover and preserve as much historical information as possible.

After the topsoil is removed, archaeologists assess the site for any visible features or structures. If there are no significant remainders, a more cautious approach is necessary. The excavator's drivers are directed to maintain a consistent depth, ensuring that they do not accidentally damage any features that might be present below the ploughsoil. This method, often referred to as stratigraphic excavation, involves carefully uncovering each layer to reveal the historical timeline.

Dealing with Compounded Layers: Geology and Archaeology

One of the significant challenges in excavation is the presence of compounded layers, which can make it difficult to determine the true depth at which archaeological features might be present. Factors such as alluvium, colluvium, and other geological processes can bury ancient artifacts or structures. Therefore, archaeologists need to make informed decisions about the depth at which to continue excavation. For instance, on some sites, the ancient land surface where the archaeological remains are located may be buried beneath layers of geological processes. This requires a thorough understanding of local geology and pedology (soil science).

For example, in figure 1, an early medieval site in Bavaria, the remains included boundary ditches, post-built structures, and two graves. The geology of the area indicated that the soil was Alm, a type of loess soil. In figure 2, an area near Augsburg, excavations revealed 3 Roman graves, one of which had been robbed in antiquity. The geology here was Loess, which provided excellent working conditions, allowing for clear sections. Figures 3 and 4 depict early medieval graves and a unique ritual enclosure near Dachau and Augsburg, respectively, with the local geologies being glacial gravel and glacial soil.

Techniques for Ancestral Feature Identification

Identifying ancestral features is a critical part of the excavation process. Commonly observed features include postholes, wall slots, fence lines, ditches, wells, graves, and other signs of human activity. However, in highly ploughed areas, such as those depicted in figures 1 and 2, modern ploughing might have obliterated some features or made them difficult to distinguish due to soil chemistry. In such cases, the excavation techniques and the geology play a crucial role in uncovering what remains.

For instance, in figure 1, the post-built structures and graves were clearly visible, while in figure 2, the robbed grave showed a distinct robber trench as an oval shape. The use of geological information helps to understand the soil's behavior, thus aiding in the identification of archaeological remains. In figure 3, early medieval graves were examined in an area with glacial gravel, further emphasizing the importance of geology in archaeology. Figure 4 provided insights into a unique ritual enclosure near Dachau, which required skilled excavation techniques and a deep understanding of the prehistoric period.

Conclusion: Balancing Development and Discovery

In commercial archaeology, the balance between development and discovery is delicate. Through careful stratigraphic excavation, informed by geology and topography, archaeologists can uncover significant historical data. The techniques used in these excavations not only help in identifying and preserving archaeological remains but also provide valuable insight into the historical and cultural heritage of a site.

By understanding the nuances of geology and the careful execution of excavation methods, archaeologists can make informed decisions about what to excavate and how deeply, ensuring that important historical information is not lost in the process of development.