Surface Collections

Surface Collections

Surface materials are important for archaeological first-impressions. Archaeologists make many research judgments based on surface information. Surface indications guide decisions about which sites to excavate--which site is likely to yield the most significant subsurface material and which site likely does not offer significant research potential--and about where to dig on a particular site. Comparisons of surface materials might also be used to distinguish among different types of sites.

However, surface collections may be influenced by natural selective processes that cause certain kinds of artifacts to be buried quickly or driven to the surface frequently. Understanding these influences is necessary if accurate predictions about buried materials are to be made and if meaningful site comparisons based on surface materials are to be drawn. This study indicates that surface material from one location may be as different from subsurface material at that location as is material from two different sites.

In order to evaluate how static the frequencies of artifact types are in surface collections, we conducted three complete surface collections at the Tenderfoot Site over several field seasons. We hoped that the comparisons of successive surface collections from one site would give us information to aid in predicting the potential significance of a site. Surface lithic-scatter sites are the most commonly recorded sites in the West; the value of much of the archaeological record will be increased by making the interpretation of surface sites more secure.

X2 value of differences among surface collections across the Tenderfoot site.

Attribute

Chi square value

df

Significance

Material

20.979

4

.000

tool-debitage

155.603

2

.000

condition

1195.690

12

.000

fragment

11125.821

10

.000

platform

1221.236

4

.000

termination

1129.909

6

.000

cortex

1017.667

8

.000

Cross-tabulation analysis shows that the compositions of the three surface collections from Tenderfoot are statistically different. The collections were conducted at the same site, using the same methods, and were separated by time. Yet, the three collections do not appear to be randomly drawn from the same population. Since they were drawn from the same population--material left behind in prehistory--there is one conclusion to be drawn: the natural processes that move artifacts between surface and subsurface and between subsurface and surface are not random processes, but are selective processes.

If surface collections from the same site are as different from each other as are surface collections from among sites, then site survey alone might cause one to interpret the results of natural processes as cultural differences. Furthermore, these natural, nonrandom selective forces must be working elsewhere. For instance, if they are operating while a stratified site is aggrading, they may create a series of sorted assemblages; the archaeologist who excavates such a site might interpret assemblage differences among levels in the site as evidence of culture change. We must discover the natural processes at work and learn how they act on artifacts to prevent such misinterpretations.