10.1 Excavation Techniques and Site Formation Processes
3 min read•july 25, 2024
Excavation techniques in paleoanthropology are crucial for uncovering our ancient past. From survey methods like aerial photography to careful fossil extraction, these methods ensure we gather as much information as possible from archaeological sites.
Understanding site formation and is key to interpreting fossil evidence. By studying how remains become fossils and the processes that affect them over time, we can better reconstruct past environments and the lives of our ancestors.
Excavation Techniques
Techniques in paleoanthropological excavations
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- Survey methods scout potential sites before excavation
- Aerial photography captures large-scale landscape features (ancient riverbeds)
- Ground-penetrating radar detects subsurface anomalies without digging (buried structures)
- Magnetometry measures magnetic variations in soil indicating past human activity (hearths)
- Excavation grid system organizes site for precise spatial recording
- Establishment of datum points creates fixed reference for measurements
- Division of site into squares facilitates systematic excavation and artifact mapping
- Careful removal of sediment preserves contextual information
- Use of and brushes prevents damage to delicate fossils
- Sieving of excavated material recovers small artifacts and ecofacts (teeth, pollen)
- Documentation techniques create comprehensive site record
- Detailed field notes describe soil composition, artifact locations, and observations
- Photography of fossils captures spatial relationships before removal
- 3D mapping of artifact locations enables virtual reconstruction of site
- Fossil extraction methods protect fragile specimens
- Application of consolidants strengthens brittle fossils (PVA)
- Plaster jacketing for fragile specimens supports bones during transport (hominid skulls)
Importance of stratigraphic control
- Determination of relative age of fossils based on layer position
- Identification of distinct geological layers reveals depositional history
- Reconstruction of paleoenvironments from sediment composition and inclusions
- Correlation with other sites establishes regional chronologies
- Establishment of chronological sequence orders events in time
- Recognition of intrusions or disturbances alerts to potential contamination (rodent burrows)
Site Formation and Taphonomy
Site formation processes for fossils
- Depositional processes bring remains to resting place
- Fluvial transport moves bones along rivers and streams
- Volcanic ash falls rapidly bury organisms (Pompeii)
- Cave sedimentation gradually accumulates remains over time
- Post-depositional processes alter fossil composition
- Diagenesis changes original bone structure through chemical reactions
- Compaction flattens fossils under sediment weight
- Mineralization replaces organic material with minerals
- Bioturbation disturbs original fossil positions
- Root action can fragment or displace bones
- Animal burrowing mixes sediments and fossils from different layers
- Weathering and erosion degrade exposed fossils
- Physical weathering breaks fossils through freeze-thaw cycles
- Chemical weathering dissolves fossils in acidic environments
- Anthropogenic factors introduce human influence
- Ancient human activities create fossil assemblages (butchery sites)
- Modern disturbances damage sites through construction or looting
Role of taphonomy in interpretation
- Taphonomy studies processes affecting organisms from death to fossilization
- Analysis of fossil accumulation distinguishes origins
- Natural vs. cultural assemblages reveal cause of death (predator kill vs. human hunting)
- Time-averaging of deposits mixes fossils from different time periods
- Identification of preservation biases affects representation
- Differential preservation of hard vs. soft tissues skews fossil record
- Size-related preservation patterns favor larger, more robust specimens
- Reconstruction of depositional environment informs past conditions
- Interpretation of fossil orientation and distribution reveals transport history
- Recognition of post-mortem modifications informs taphonomic history
- Carnivore damage shows scavenging activity (tooth marks)
- Trampling marks indicate exposure on ground surface
- Weathering stages reveal duration of surface exposure before burial
- Implications for paleoecological reconstructions consider taphonomic filters in interpreting past ecosystems
Key Terms to Review (19)
Contextual Analysis: Contextual analysis refers to the method of understanding archaeological findings by examining the spatial, temporal, and cultural contexts in which artifacts are discovered. This approach emphasizes the relationships between items and their surroundings, providing insights into the behaviors, practices, and environments of past societies.
Decomposition: Decomposition is the natural process through which organic material breaks down into simpler forms of matter, usually involving the action of microorganisms, fungi, and other decomposers. This process is vital in paleoanthropology as it affects the preservation of fossils and artifacts, as well as the formation of archaeological sites, influencing how we understand past environments and behaviors.
Geoarchaeology: Geoarchaeology is the study of the relationship between geological processes and archaeological sites, focusing on how these processes affect the formation, preservation, and interpretation of archaeological materials. This field combines techniques from both geology and archaeology to better understand how environmental factors influence human activity over time. By analyzing soil, sediment, and landforms, geoarchaeologists can reconstruct past landscapes and assess site formation processes that inform about human history and cultural development.
Horizontal vs. vertical excavation: Horizontal and vertical excavation are two primary excavation techniques used in archaeological fieldwork. Horizontal excavation focuses on uncovering large horizontal areas of a site to understand the spatial relationships between artifacts, structures, and features, while vertical excavation involves digging downwards to reveal stratigraphy and chronological layers within a site, providing insights into the temporal sequence of human activity.
In situ: In situ is a Latin term meaning 'in its original place.' In the context of excavation and site formation processes, it refers to artifacts, fossils, or other archaeological materials that are found in their original location of deposition. This concept is essential for understanding the context in which these materials were created or used, as it helps preserve the spatial relationships between objects and the surrounding environment.
Laetoli: Laetoli is an archaeological site in Tanzania known for its well-preserved hominin footprints, which were discovered in 1976. These footprints provide critical evidence of early hominin bipedalism and offer insights into the behavior and environment of our ancestors during the Pliocene epoch.
Olduvai Gorge: Olduvai Gorge is a significant archaeological site located in Tanzania that has provided crucial fossil evidence and stone tools related to early human ancestors. This site is pivotal in understanding human evolution and has played a major role in reconstructing the story of our origins.
Open-area excavation: Open-area excavation is a method used in archaeological digs that involves removing soil over a large, flat area to reveal artifacts and features in a systematic way. This technique allows for the observation of spatial relationships between finds and helps to understand the layout of past human activities, making it particularly useful for understanding site formation processes.
Preservation conditions: Preservation conditions refer to the specific environmental and contextual factors that affect how well organic and inorganic materials are maintained over time at archaeological sites. These conditions include aspects like temperature, humidity, soil acidity, and the presence of microorganisms, which can greatly influence the rate of decay or fossilization of remains. Understanding these factors is essential for interpreting archaeological findings and assessing the site's historical significance.
Provenience: Provenience refers to the specific location or context in which an artifact or fossil is found during excavation. Understanding provenience is crucial because it provides insights into the historical and cultural significance of the find, as well as the relationships between artifacts and their surroundings. Proper documentation of provenience helps researchers reconstruct past environments and human behaviors, making it a key element in archaeological studies.
Remote sensing: Remote sensing is the technique of obtaining information about an area or object from a distance, typically using satellite or aerial imagery. This method allows researchers to gather data without direct contact, making it invaluable for studying large and often inaccessible sites, especially in paleoanthropology. By analyzing these images, scientists can identify features like soil composition, vegetation cover, and potential archaeological sites, which aids in planning excavation strategies and understanding site formation processes.
Screening: Screening refers to the process of sifting or separating materials during excavation to identify and collect artifacts or ecofacts from sediment. This technique is essential for recovering smaller items that might be overlooked in bulk excavations and helps to ensure a thorough examination of a site. By utilizing various methods, screening can enhance the understanding of site formation processes and the context of archaeological finds.
Sediment deposition: Sediment deposition refers to the process by which particles, such as sand, silt, and clay, settle out of a transporting medium like water or air and accumulate in a new location. This process is crucial for understanding how geological formations develop over time and can provide insights into the environmental conditions that existed during different periods of Earth’s history.
Shovels: Shovels are essential tools used in archaeological excavation to dig, move, and transfer soil or sediment from sites of interest. These tools come in various shapes and sizes, making them versatile for different excavation techniques and helping researchers effectively expose and document artifacts and other significant features within a site.
Site disturbance: Site disturbance refers to any alteration or disruption of an archaeological site that affects its integrity and the context of artifacts, features, and ecofacts. This can occur naturally through processes like erosion and sedimentation or anthropogenically through construction, agriculture, or looting. Understanding site disturbance is crucial for evaluating how sites form and are preserved over time.
Strata: Strata refer to layers of sedimentary rock or soil that are deposited over time, often revealing a chronological sequence of geological or archaeological events. These layers can provide critical information about the history of a site, including changes in environment, climate, and human activity. Analyzing these layers allows researchers to understand how a site has formed and what it may contain.
Stratigraphic excavation: Stratigraphic excavation is a systematic method used to study archaeological sites by carefully removing layers of soil and sediment to reveal the chronological sequence of human activity. This technique helps researchers understand how different layers were formed over time, reflecting the site's history and the environmental conditions at various points. It’s crucial for reconstructing past behaviors, cultures, and the processes that shaped the archaeological record.
Taphonomy: Taphonomy is the study of the processes that affect organic remains from the moment of death to their discovery as fossils. This field helps to understand how fossils are formed, preserved, and altered over time, shedding light on the ecological and environmental contexts in which these remains were found.
Trowels: Trowels are essential hand tools used in excavation, particularly in archaeology and paleoanthropology. They feature a flat blade with a pointed end, allowing researchers to carefully remove soil and sediment layers while minimizing disturbance to the surrounding area. Trowels are crucial for revealing stratigraphy and understanding site formation processes, enabling a detailed examination of artifacts and fossils within their context.