Bifaces and breakage patterns

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

10:49 AM - Jun 21, 2006 #1

Hello all,

I know several of you are following my research at the moment and I want give you an update. Bruce and I have agreed on my dissertation topic. I will be doing an experimental study to further our understanding of the cause of perverse fracturing during bifacial thinning. This research is designed to be broad so that the results can be applied to most bifacial thinning technologies / cultures (i.e. Paleo, Solutrean, Caddo, etc.)

I am currently searching for an archaeological assemblage that contains large thin bifaces that exhibit perverse fracturing during manufacture. The ideal would be to have all the refit pieces to compare to the experimental results, but I know that would be a stretch. I will likely have a Solutrean component, but am open to examples from the States. Any ideas or leads would be greatly appreciated.

Thank you,
Michael Miller
University of Exeter
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

Just a Flake
Registered User
Just a Flake
Registered User
Joined: 9:40 AM - Mar 05, 2006

12:47 PM - Jun 21, 2006 #2

Good project Michael, at least one flintknapper will benefit from breaking large thin bifaces in the next year or so. Do you need only refits? Guys in Texas are digging a lot of blades that are broken and they can be had cheap. Lots of tips and backs and the breakage patterns are remarkably consistant, Thinness is also usually very consistant. If you need exact refits it's a tall order, the few pieces I have are material flaw breaks. If specific refits are not necessary I can put you in touch w/ a man that can get you all you want. How large is large? and I assume thinness is better than 6/1?Marty
Quote
Like
Share

Paleoknapperjim
Registered User
Paleoknapperjim
Registered User
Joined: 10:23 AM - May 30, 2006

2:05 PM - Jun 21, 2006 #3

Hi Michael,

I'm unclear on perverse fracturing, is it just the normal type of fracture? I know a number of us break big bifaces during the thinning process, would photos of these be of value to your study? ...jim
Quote
Like
Share

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

5:19 PM - Jun 21, 2006 #4

Hello,

Thanks for the good comments. The terminology is lacking when it comes to breaking bifaces. There are two types that can be generally agreed upon, bending and perverse. A perverse fracture is a spiral / twisting break that occurs during bifacial thinning. Example, you strike a thinning flake in the center and the blade breaks in three fragments, one break travels from the center towards the base while the other goes toward the tip. Bending fractures occur when the strike causes to much stress and the elasticity of the stone can't hold. An example would be a biface breaking into two and the fracture is straight across the blade and you have a lip at the top end of one fragment.

Photos of bifaces broken with perverse and bending fractures would be welcomed. A good shot of the flake that broke the biface would also be helpful. As we all know, the platform of that flake was not right or our swing was off. I'm trying to scientifically find a range and a normative cause among bifaces and the knappers who make / break them.

I'm not really looking to purchase any archaeological material. I'd rather use an established dataset of provenienced finds and I would only need some photos and measurements.

Thanks,
Michael
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

scalp creek
Registered User
scalp creek
Registered User
Joined: 10:59 PM - May 23, 2005

1:03 PM - Jun 23, 2006 #5

Michael,
Well I think you explained the two types pretty well.....I have some broken bifaces, I think almost all are bending breaks from your description.
If you can find a photo/photos of "perverse fracture" on biface and what to look for to distinguish it from bending fracture..that would be helpful in finding material for your use.

scalp creek
"History is a bloody business."
I have never lost an obstinate sense of detachment, of the need for solitude---a feeling which increases with the years. ~~ Albert Einstein
Quote
Like
Share

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

9:18 PM - Jun 23, 2006 #6

Hello,

You are right, pictures can always say more than words. Here are two bifaces from Les Matrieux in France. Both broken by perverse fracture. I included some close-ups of the edges from both the obverse and reverse of the one piece.








Cheers,
Michael
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

eskimoboy
Registered User
eskimoboy
Registered User
Joined: 8:19 AM - May 14, 2005

2:26 AM - Jun 26, 2006 #7

Thanks for posting the photos, that helped lots.
I broke a peice awhile back, give me a couple of days to post a photo, I never had one break quite like it did
Quote
Like
Share

scalp creek
Registered User
scalp creek
Registered User
Joined: 10:59 PM - May 23, 2005

5:24 PM - Jun 26, 2006 #8

MJFLINTY,
thanks for posting the pix and closeups too, they help a lot in saying what you are talking about. KNow you are limited in time to spend on the web..with school and all. thus your time is very important. will need to check my stash of broken points and see what I have that looks like that.
great pixs by the way., specially the closeups of the fracture ledges.
scalp

PS, Michael, okay, I got home from work, made some pixs of some fractures on ancient pieces that may or may not be perverse fractures. What I tried to do was make a pix of the biface "straight on" and then tilt it so you could see the shape of the fracture ledge itself. So usually the following pix are in that order, 1. straight on & 2. tilted same piece. One or two may have two tilted shots, but he straight on is first always. This is a slide show, you should be able to see the still pix, if not email me and I will send you a link to the folder.
s60.photobucket.com/albums/h8/clovisfirst/perverse%20fractures/?action=view&slideshow=true


there are 9 different bifaces in the photos on the slide show.
scalp creek
"All that tread the globe are but a handful to the tribes that slumber in it's bosom."
I have never lost an obstinate sense of detachment, of the need for solitude---a feeling which increases with the years. ~~ Albert Einstein
Quote
Like
Share

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

10:01 AM - Jun 27, 2006 #9

Hello Scalp,

The images you posted are very good! The majority are perverse fractures. There are two that are not. The colorful Alibates piece broke due to an incipient fracture plane (an old break in the stone that was there when the maker started). The paleo base looks like a haft snap (transverse fracture). The rest are all textbook examples of perverse fracture. When I get to my figures section I may include some of these if I can have your permission. I'd just need a rough idea about the assemblage they come from and location (state is fine).

Thanks for the great show!
Michael
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

scalp creek
Registered User
scalp creek
Registered User
Joined: 10:59 PM - May 23, 2005

11:43 AM - Jun 27, 2006 #10

Michael,
They all are from Texas. The alibates was found in the panhandle of Texas. All the remaining pieces were found in central Texas, the area around Georgetown, Texas. You certainly have my permission to use the photos. If you need the actual artifacts, I can them to you for your use. A lot of the alibates material has old lines of fracture or layering in the stone, that is likely what caused that break on the ancient one's piece there.
Glad you could use the pix.
Cheers to you,
scalp creek
"All that tread the globe are but a handful to the tribes that slumber in it's bosom."
I have never lost an obstinate sense of detachment, of the need for solitude---a feeling which increases with the years. ~~ Albert Einstein
Quote
Like
Share

scalp creek
Registered User
scalp creek
Registered User
Joined: 10:59 PM - May 23, 2005

8:03 PM - Jul 04, 2006 #11

michael,
if you are still reading this forum, I had a perverse fracture today (I think) while knapping, I had a large san antonio putty colored flint preform that I was thinning from the side and it fractured right across the middle at an angle and has the characteristic shape of the fracture face. here is the slideshow:
s60.photobucket.com/albums/h8/clovisfirst/perverse%20fracture%202/?action=view&slideshow=true

hope it works.
scalp creek
"All that tread the globe are but a handful to the tribes that slumber in it's bosom."
I have never lost an obstinate sense of detachment, of the need for solitude---a feeling which increases with the years. ~~ Albert Einstein
Quote
Like
Share

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

10:47 PM - Jul 04, 2006 #12

Great pictures,

Just about the perfect perverse fracture. I'd say that crystal vug helped it along too. Any ideas on why it happened? How did you support the piece?

Thanks,
MichaelMichael J. Miller
University of Exeter - Archaeology
Webmaster - www.flintknappers.com
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

scalp creek
Registered User
scalp creek
Registered User
Joined: 10:59 PM - May 23, 2005

11:02 PM - Jul 04, 2006 #13

yeah, i had been trying to work around the vug...,my error was i was thinning the middle prior to the ends.....i knew better. i was supporting it freehand with my fingers completely under it. i had just taken about three real nice flakes and my confidence was high....too high.
scalp
ps the blow that broke came from bottom of first pix.
"All that tread the globe are but a handful to the tribes that slumber in it's bosom."
I have never lost an obstinate sense of detachment, of the need for solitude---a feeling which increases with the years. ~~ Albert Einstein
Quote
Like
Share

BOHUNTER
Registered User
BOHUNTER
Registered User
Joined: 5:44 PM - Feb 20, 2006

10:04 AM - Sep 10, 2006 #14

Michael,

Im not really sure on the Perverse fracture but I have noticed when I break a preform it ALWAYS breaks in a fracture diagonal as it was a Heavy hit, even with an OK platform set up. The cone makes the bulb and this radiates from one side of it diagonally!

I have not broken many that went Perpendicular to the Center median. Its like a spiral fracture too twisting across.

And if you have a little crystal or pocket, well your lucky to get it thin and keep it together! As for anyone!
Quote
Like
Share

turk4224
Registered User
turk4224
Registered User
Joined: 10:57 PM - Oct 28, 2005

7:08 PM - Sep 10, 2006 #15

Here is a point i found it is broken at a crystal pocket thought you might like a look
Quote
Like
Share

mjflinty
Registered User
mjflinty
Registered User
Joined: 2:46 AM - May 05, 2006

9:34 PM - Sep 10, 2006 #16

Hello,

That point looks like it was broken in the haft. I'm sure the quartz vug helped the fracture too. Most finished bifaces don't suffer from perverse fracture as the width/thickness ratio only goes up as it is resharpened. You do sometimes see what I think may be a perverse fracture when a pressure flaker is twisted just right inside a notch and causes the ear, barb, or whole base to break off.

Thanks for the post!
Michael
Michael Miller
http://www.FlintKnappers.com
Quote
Like
Share

FLINTKNAPPING RAY
Registered User
FLINTKNAPPING RAY
Registered User
Joined: 5:06 AM - Feb 17, 2007

5:59 PM - Mar 16, 2007 #17

Callahan, E. 1979 The Basics of Biface Knapping In The Eastern Fluted Point Tradition. A Manual for Flintknappers And Lithic Analysts. Archaeology of Eastern North America 7: 1-180. ed. Brennan, New York.
Quote
Like
Share