Doing Fieldwork: Why Archaeologists Dig Square Holes

This chapter will enable you to answer these questions: Why does context matter? How is it recorded? What determines preservation? What is the difference between arbitrary and Natural levels? Why do these matter? How do archaeologists recover the smallest artifacts and ecofacts?

Outline Excavation: What Determines Preservation? Principles of Archaeological Excavation Precision Excavation Sifting the Evidence Cataloging the Finds Conclusion: Archaeology’s Conservation Ethic: Dig Only What You Must

Introduction An artifact’s provenience, or the location relative to a system of spatial data collection, is the most important thing about the artifact. Provenience is essential to recording an artifact’s context, the relationship of an artifact, ecofact, or feature to other artifacts, features, and geological strata in a site. This information is crucial to knowing what an artifact has to tell us.

The Folsom Site and Humanity’s Antiquity in North America Pleistocene, a geological period from 1.8 million to 10,000 years ago, which was characterized by multiple periods of extensive glaciation. Artifacts with bones of animals living during the Pleistocene proved that humans had been in N. America for at least 10,000 years.

The Folsom Site and Humanity’s Antiquity in North America Discovered by George McJunkin (1851-1922), who spotted bones protruding from walls of arroyo The Folsom site in 1998. A bison skull is uncovered in the excavation unit.

The Folsom Site and Humanity’s Antiquity in North America A fluted Folsom spear point lying between the ribs of an extinct species of bison at the Folsom site.

The Folsom Site and Humanity’s Antiquity in North America In situ, from Latin, meaning “in position”’ the place where an artifact, ecofact, or feature was found during survey or excavation. The association between the spear points and extinct bison remains confirmed the presence of people in the Americas since at least the end of the Pleistocene, some 10,000 years ago.

Excavation: What Determines Preservation? The exact procedures in any excavation depend on several factors, beginning with the kind of materials that have survived the passage of time. Some sites preserve organic materials, including basketry, leather, and wood. In other sites only ceramics, stones, and bones survive. Decomposition is carried out by microorganisms that require warmth, oxygen, and water to survive. The absence allows preservation.

Excavation: What Determines Preservation? A 2000-year-old duck decoy from Lovelock Cave, Nevada; dry and dusty conditions allowed preservation.

Excavation: What Determines Preservation? The archaeological site of Ozette on the coast of Washington with saturated dirt and clay preserved entire houses with all the furnishings and gear.

Excavation: What Determines Preservation? Ötzi, the “Ice Man” and portions of some of his tools (above) preserved in a glacier.

The Excavator’s Toolkit 5–6 inch trowel Metal file 2- and 25-meter tape measure Work gloves Builder’s level and angle finder Compass Pencils and Sharpie pens Spoon, Nails, Jackknife Straight-edge ruler (metric) Torpedo level Root clippers Small wire cutters Canisters and Ziploc bags for samples Toilet paper (for wrapping delicate artifacts) Dental tools, brushes, bamboo slices, aluminum foil Toothpicks (for temporarily marking artifact locations)

Principles of Archaeological Excavation: Test Excavations Test excavation, a small initial excavation to determine a site’s potential for answering a research question. Dig metrically, typically in 1-meter squares, recording the x and y axes (horizontal coordinates) and the z axis (vertical coordinate). Vertical provenience is measured relative to the ground surface.

Principles of Archaeological Excavation Establish a datum, or zero point, which is a fixed reference used to keep control on an excavation; controls both the vertical and horizontal dimensions of provenience. Archaeologists excavate within horizontal excavation units in natural levels and arbitrary levels.

Principles of Archaeological Excavation Natural levels, the site’s strata which are more or less homogeneous, visually separable from other levels by a change in texture, color, rock, or organic content. Archaeologists prefer to excavate in natural levels wherever possible.

Principles of Archaeological Excavation Arbitrary levels, basic vertical subdivisions of an excavation square. They are used only when recognizable “natural” strata are lacking and when natural strata are more than 10cm.

Principles of Archaeological Excavation Strata (singular stratum), more or less homogeneous or gradational material visually separable from other levels by a discrete change in the character of the material– texture, compactness, color, rock, organic content– and/or by a sharp break in the nature of the deposition.

Arbitrary Levels Can Effect Artifacts From Natural Strata The natural strata—A, B, C, and D—each contain a particular kind of artifact. Each strata represents a unit of time. If excavated using arbitrary levels—1, 2, 3, and 4—those levels would crosscut the strata.

Expanding Gatecliff’s Excavation As the result of flash floods, layers of sterile silt neatly separated living floors, or distinct buried surfaces where people lived. The investigation shifted to concentrate on recording spatial distributions of artifacts and features on the living floors, in order to reconstruct what activities took place in the shelter.

Precision Excavation Total station, a device that use a beam of light bounced off a prism to determine an artifact’s provenience and accurate to millimeters. Recording the provenience of every item found in situ provides a very accurate record Record the “top” side of the artifact, the compass orientation of the long axis, and its slope and inclination

Sifting the Evidence Digging is just the beginning of excavation. No matter how carefully you excavate, it is impossible to see, map, and recover everything of archaeological interest. Sifters find things that hand excavation misses. Screen size affects what you recover and how fast you recover it.

Sifting the Evidence: Water Screening and Matrix Sorting Water screening, a sieving process in which deposit is placed in a screen and the matrix washed away with hoses; essential where artifacts are expected to be small and/or difficult to find without washing. Matrix sorting, the hand sorting of processed bulk soil for minute artifacts and ecofacts.

Sifting the Evidence: Flotation Flotation, the use of fluid suspension to recover burned plant remains and bone fragments from archaeological sites.

Cataloging the Finds Excavation is only about 15 percent of a project – most time is spent in the lab analyzing the remains. Objects must be catalogued to ensure that an artifact’s original provenience, and consequently its context, is never lost.

Summary Questions Why does context matter? How is it recorded? What determines preservation? What is the difference between arbitrary and natural levels? Why do these matter? How do archaeologists recover the smallest artifacts and ecofacts?