Thursday’s touchstone blurt has prompted three interesting comments–two of which from long-time acquaintances; one of which was left by Edward Harris, progenitor of the Harris Matrix and author of Principles of Archaeological Stratigraphy [which the author has made freely available online–just click on the title].
All three expressed dismay that any archaeological sites are still excavated in arbitrary levels, and they all added a gentle prod to the effect that I should not be so quick to accept the practice’s continued use, even for sites in California. The problem really boils down to this. California archaeologists aren’t dealing with cultural deposits in homogeneous natural sediments. They’re dealing with completely homogenized (bioturbated) natural sediments and cultural traces. That’s quite a different story, as I’ll argue further down. But right now: nail buffing time.
The Matrix man [or so he calls himself] sent me an email in addition to leaving a comment on Thursday’s blurt, which I copy here for posterity
Thank you for your kind remarks and I made a comment on your interesting blog.
How can we advance the revolution (the Matrix is 40 next February!). Perhaps I should learn how to do a blog.
Anyway, I was speaking with colleagues from Playa Vista in California, who suggest they could not have done that dig without the matrix!
Here is the first one ever made and also a little article. You can post them if you like. The first-ever Matrix (read, as we now know, “stratigraphic sequence”) was made in 1974 for the site excavated that year at the south gate into the Roman town of Winchester, England.
Edward C. Harris, MBE, JP, PHD, FSA, Executive Director
To see his article on time and the Matrix, click here.
|First-ever Harris Matrix–South Gate, Roman Winchester, 1974 (Photo courtesy of E. Harris).|
In what follows I’ll try to explain (and not explain away) the conundrum faced by every archaeologist in almost any landform and at almost any altitude in California. Here goes!
Regardless of the characteristics of the parent material on and in which pre-Columbian California archaeological occupation sites have formed, and regardless of the rate of aggradation throughout the period during which the cultural materials were abandoned, there is a Nemesis against which it is futile for an archaeologist to struggle: fossorial rodents–specifically the ground squirrel (Sciuridae) and the pocket gopher (Geomyidae). These animals are prodigious breeders and tireless burrowers. And because they have been present throughout the epoch of human occupation, they have had a universal and profound, time-transgressive effect on the vertical and horizontal distribution of archaeological materials in California sites. This has been documented in numerous ways and in sites across the Golden State.
These animals are capable of transporting any clast smaller than their burrow’s diameter anywhere from millmeters to (eventually) meters from it original location (if that was, in fact, its ‘original’ location). At any time they are regularly disturbing the top 50 cm or so. Given their habit of pushing their backdirt upward and out onto the surface, the smaller archaeological pieces ‘liberated’ in this fashion tend to remain in the upper 10 cm or so. And larger clasts are transported generally downward because over time they are undermined and drop a few cm at a time. This can happen to boulders and everything smaller that can’t be displaced along the burrow itself.
The habits and ubiquity of these rodents have ensured that no site in California, and certainly no site with a longish occupation sequence, can be expected to present observable stratification or, for that matter, a vertical column that contains the oldest traces at depth; the youngest near or at the surface. Moreover, the process size-selective upward and downward displacement I’ve just outlined means that in general there is a bi-modal vertical distribution of artifacts and natural clasts.
Donald L. Johnson’s three drawings below illustrate what can and does occur as a matter of course in (quite literally) any unconsolidated dirt anywhere in California with the exception of [and I’m guessing here] the area above the tree line. It’s necessary to read the detailed figure captions to make sure you understand what’s going on in each series. However, I’m certain that those of you who aren’t from around here will be astonished and might eventually come to accept why it is no surprise that arbitrary levels are still the state of the art in California.
|Johnson. Donald L. 1989. Subsurface Stone Lines, Stone Zones, Artifact-Manuport Layers, and Biomantles Produced by Bioturbation via Pocket Gophers (Thomomys Bottae), American Antiquity, 54, 370-389.|
a. the position of the large clasts that weren’t released during excavation.
b. the presently visible rodent krotovinas
c. a humic layer at the top of the sequence that represents where the latest decomposed vegetation has resulted in illuviation
d. any pedogenetical horizonation that may still be in evidence below where burrowing has occurred, which is often the case in what are known as ‘prairie soils’ in relatively xeric landscapes, where illuviation of carbonates creates a relatively rodent-unfriendly consolidated layer at depth.