Post by Marsrocks on Feb 14, 2011 12:22:41 GMT -5
Interesting - how scientists try to distinguish rock flakes to be either created by human action or natural geological action:
Geofacts
When is a Broken Rock NOT an Artifact?
By K. Kris Hirst, About.com Guide
A 'geofact' is a piece of rock that has been naturally broken, as opposed to one that was broken by purposeful human agency. The word is what linguists call a 'back formation' from the word artifact, of course; artifacts are products of human behaviors, while geofacts are products of natural forces.
These are important to distinguish in particular at very very old sites, where the implications of misidentifying broken rock as artifacts are pretty serious. As a result, there are a few rules archaeologists use to sort out geofacts from artifacts. By the way, the flip side of identifying geofacts is identifying systematic flaking--the characteristics of human working.
Evidence of Geofacts
Your artifact is probably a geofact if two or more of the following are true.
There are four or fewer flake scars. A flake (aka waste flake or debitage) is what archaeologists call a tiny fragment of stone broken off a larger stone. A flake scar is the dent made on a piece of rock from where a small fragment was removed. Flake scars can occur naturally, when rocks bang against each other in a rock slide or within a streambed; but more than four begins to look intentional.
There is no platform preparation. Precise control of stone flaking is an important part of stone tool manufacture. Evidence that a flat place was created on a piece of stone from which to knock off additional flakes is a sure sign of human activity.
The flake scars are weathered at different rates. Weathering is the term used to describe the effects of long-term exposure to climatic events. All exposed surfaces of an untouched stone should weather at the same rate. Depending on the climate and the type of rock, it takes many centuries or millennia for weathering to be apparent. If a stone has several flakes removed, and the flake scars are differently weathered, you know there was a large quantity of time passed between flaking events, and so not likely human.
The flake scars occur randomly on the rock. Flaking scars made on stone by human beings are likely to be patterned, rather than random.
For More Information
See the Lithic Analysis section for links to additional resources, including a much larger bibliography than the one that follows. Texas Beyond History has a picture of geofacts that shows how tricky they can be to identify.
Austin, Robert J. 1999 Technological characterization of lithic waste-flake assemblages: Multivariate analysis of experimental and archaeological data. Lithic Technology 24(1):53-68.
Bisson, Michael S. 2001 Interview with a Neanderthal: an experimental approach for reconstructing scraper production rules, and their implications for imposed form in middle Palaeolithic tools. Cambridge Archaeological Journal 11(2):165-184.
Bradbury, Andrew P. and Phillip J. Carr 1995 Flake typologies and alternative approaches: An experimental assessment. Lithic Technology 20(2):100-115.
Collins, Michael B. 1994 Comprehensive lithic studies: Context, technology, style, attrition, breakage, use-wear, and organic residues. Lithic Technology 18(1&2):87-94.
Gillespie, Jason David, Susan Tupakka and Christine Cluney. 2004. Distinguishing between naturally and culturally flaked cobbles: A test case from Alberta, Canada. Geoarchaeology 19:615-633.
Heinrich, Paul V. 2002. Artifacts or Geofacts? Alternative Interpretations of Items from the Gulf of Cambay.
Mercader, Julio, Huw Barton, Jason Gillespie, Jack Harris, Steven Kuhn, Robert Tyler, and Christopher Boesch. 2007. 4,300 Year Old chimpanzee sites and the origins of percussive stone technology. Proceedings of the National Academy of Science.
Pelcin, Andrew W. 1997 The formation of flakes: The role of platform thickness and exterior platform angle in the produciton of flake initiations and terminations. Journal of Archaeological Science 24:1107-1113.
Wallace, Ian J. and John J. Shea 2006 Mobility patterns and core technologies in the Middle Paleolithic of the Levant. Journal of Archaeological Science 33:1293-1309.
archaeology.about.com/od/gterms/a/geofact.htm
faculty.ksu.edu.sa/archaeology/Publications/Palaeolithic/Distinguishing%20between%20Artifacts%20and%20Geofacts.pdf
Geofacts
When is a Broken Rock NOT an Artifact?
By K. Kris Hirst, About.com Guide
A 'geofact' is a piece of rock that has been naturally broken, as opposed to one that was broken by purposeful human agency. The word is what linguists call a 'back formation' from the word artifact, of course; artifacts are products of human behaviors, while geofacts are products of natural forces.
These are important to distinguish in particular at very very old sites, where the implications of misidentifying broken rock as artifacts are pretty serious. As a result, there are a few rules archaeologists use to sort out geofacts from artifacts. By the way, the flip side of identifying geofacts is identifying systematic flaking--the characteristics of human working.
Evidence of Geofacts
Your artifact is probably a geofact if two or more of the following are true.
There are four or fewer flake scars. A flake (aka waste flake or debitage) is what archaeologists call a tiny fragment of stone broken off a larger stone. A flake scar is the dent made on a piece of rock from where a small fragment was removed. Flake scars can occur naturally, when rocks bang against each other in a rock slide or within a streambed; but more than four begins to look intentional.
There is no platform preparation. Precise control of stone flaking is an important part of stone tool manufacture. Evidence that a flat place was created on a piece of stone from which to knock off additional flakes is a sure sign of human activity.
The flake scars are weathered at different rates. Weathering is the term used to describe the effects of long-term exposure to climatic events. All exposed surfaces of an untouched stone should weather at the same rate. Depending on the climate and the type of rock, it takes many centuries or millennia for weathering to be apparent. If a stone has several flakes removed, and the flake scars are differently weathered, you know there was a large quantity of time passed between flaking events, and so not likely human.
The flake scars occur randomly on the rock. Flaking scars made on stone by human beings are likely to be patterned, rather than random.
For More Information
See the Lithic Analysis section for links to additional resources, including a much larger bibliography than the one that follows. Texas Beyond History has a picture of geofacts that shows how tricky they can be to identify.
Austin, Robert J. 1999 Technological characterization of lithic waste-flake assemblages: Multivariate analysis of experimental and archaeological data. Lithic Technology 24(1):53-68.
Bisson, Michael S. 2001 Interview with a Neanderthal: an experimental approach for reconstructing scraper production rules, and their implications for imposed form in middle Palaeolithic tools. Cambridge Archaeological Journal 11(2):165-184.
Bradbury, Andrew P. and Phillip J. Carr 1995 Flake typologies and alternative approaches: An experimental assessment. Lithic Technology 20(2):100-115.
Collins, Michael B. 1994 Comprehensive lithic studies: Context, technology, style, attrition, breakage, use-wear, and organic residues. Lithic Technology 18(1&2):87-94.
Gillespie, Jason David, Susan Tupakka and Christine Cluney. 2004. Distinguishing between naturally and culturally flaked cobbles: A test case from Alberta, Canada. Geoarchaeology 19:615-633.
Heinrich, Paul V. 2002. Artifacts or Geofacts? Alternative Interpretations of Items from the Gulf of Cambay.
Mercader, Julio, Huw Barton, Jason Gillespie, Jack Harris, Steven Kuhn, Robert Tyler, and Christopher Boesch. 2007. 4,300 Year Old chimpanzee sites and the origins of percussive stone technology. Proceedings of the National Academy of Science.
Pelcin, Andrew W. 1997 The formation of flakes: The role of platform thickness and exterior platform angle in the produciton of flake initiations and terminations. Journal of Archaeological Science 24:1107-1113.
Wallace, Ian J. and John J. Shea 2006 Mobility patterns and core technologies in the Middle Paleolithic of the Levant. Journal of Archaeological Science 33:1293-1309.
archaeology.about.com/od/gterms/a/geofact.htm
faculty.ksu.edu.sa/archaeology/Publications/Palaeolithic/Distinguishing%20between%20Artifacts%20and%20Geofacts.pdf
