Workshop 3 - Flake Terminations
In Workshop 2 we looked the features of conchoidal and bending initiations, plus undulations, umbos, and eraillure scars and flakes.
Now, in Workshop 3, we will focus on the attributes of flake terminations, particularly hinges and steps, but also overstruck, axial, and feather terminations.
Be sure to open up the Annotations in the model's sidebar to find pins that mark the features under discussion.
Tip: hit the play button to load the 3D model. You can now rotate the model as you read the text on the left.
A flake ends in a hinge termination when the force driving the crack is not sufficient for it to travel all the way to the bottom of the core, yet the crack is travelling too deep to exit the core ‘cleanly’, so it abruptly changes direction and curves upward to exit the core face. Many, if not most, stone cores have scars with hinge terminations at various scales.
This chert core was reduced by hard-hammer percussion flaking to produce macroblade blanks for spearpoints in northwest Queensland, Australia. In archaeological convention, a blade is a flake that is more than twice as long as wide, and a macroblade measures greater than 40 mm long.
On this model, you can see two triangular-shaped scars on the core face from striking off spearpoint blanks, but between them is a rectangular scar with an exceptionally deep hinge termination. Note the way the hinge termination curves abruptly outward. This scar cuts into a prior scar that also ended in a hinge termination.
The triangular point scars curve slightly towards the core face, but not abrupt enough to be classified as hinge terminations.
Hinge terminations are relatively common in making long blades because it is difficult to deliver sufficient force to maintain the crack to the end of the core. If you strike too hard, the macroblade may break during detachment or dive through the core, creating an overstruck termination. Conversely, if you don't strike hard enough—if your blow is too 'soft'—the macroblade may end in a step or hinge termination.
Step and hinge terminations are far more common at macroblade quarries in Queensland than overstruck terminations, suggesting that the stoneworkers consistently erred to the 'too soft' blow. This is likely related to an intention to strike-off unbroken macroblades that feather out on the central arris in a triangular shape.
When hinges or steps start to develop, a flintknapper often manipulates the end of the core, or strikes it off altogether. This reduces the mass at the core base and makes it easier to re-establish axial or feather terminations. The flintknapper who reduced this core chose to discard it altogether rather than rework the base.
This model is of a small chert blade core from the Mesolithic period in France. Blades were struck from the core by percussion.
Look at the two hinge-terminated scars indicated in the Annotations. Hinge Termination 1, on the right, is small and relatively subtle, but Hinge Termination 2 is very deep and pronounced.
Hinge and step terminations are often seen on discarded cores because the morphology led the flintknapper to conclude that correcting the hinge terminations was no longer viable.
Hinge Termination 2 appears to have been from a failed attempt to increase the angularity of the flat core face. If it had been successful, it would have re-prepared the core face for further blade detachments by re-establishing prominent arrises to strike behind.
A step termination occurs when the crack stalls from insufficient downward (compression) force. The indenter is still in contact with the platform when the stall occurs, and as the indentor follows-through along the arc of the swing, it pulls the proximal end of the stalled flake away from the core face. Since the tensile strength of knapping stone is low, the proximal end of the flake can only be pulled a short distance before snapping off in a bending fracture.
Alternatively, step fractures may occur from excessive outward force. When the flake is pulled away from the core and snaps, the compression force is removed from the propagating crack. With the compressive energy removed, the crack stalls within a short distance of the snap.
This process leaves an abrupt shelf on the core face, called a 'step'. This is the face of the bending-snap on the distal part of the flake adhering to the core.
The flake that comes away from the core is simply a broken flake—the distal part is still embedded in the core. As such, it is impossible to differentiate this type of proximal flake fragment from other flakes that break during detachment, or flakes broken afterward through use or taphonomic processes such as trampling. Many archaeologists record 'step' terminations on proximal flake fragments as a termination attribute, but the only way to reliably identify a step termination if by conjoining the broken flake back onto its core scar. Short of this, step terminations can only be reliably identified on core scars, not on flakes.
Step fractures at various scales are exceptionally common, and most cores have them.
This model is of a large silcrete horsehoof core from New South Wales, Australia. Several examples of flake scar terminations are listed in this model's Annotations.
Start by examining the annotation labelled 'Mixed termination: step'. Note that this scar mostly ended in a step termination, but the crack had just enough energy in the corner to curve upwards to the core face—this a hinge termination (labelled in the annotations as 'Mixed termination: hinge'). The termination for this scar is, technically, a mixture of step and hinge, although most archaeologists would probably call this a step-terminated flake scar. The crack force mainly dissipated across that flat surface and stalled, resulting in the step, but the arris (ridge at the edge of a flake scar) on the left-hand side channelled and concentrated the force there, allowing that part of the crack to travel somewhat farther and hinge. Mixed terminations like this are relatively common.
Now click on the annotation labelled 'Step termination'. The pin marks the step termination on this relatively short flake. If you click on the annotation labelled 'Embedded crack', you will see the crack extending into the core. This is the distal end of the snapped flake, which remains embedded in the stone.
The conventional view among archaeologists is that step terminations are flintknapping mistakes, but in the case of horsehoof cores, step-terminated flakes were struck purposefully as a way of rejuvenating the edge of a large core tool without removing much mass. The technique is called 'step-flaking' retouch.
This model is a Clovis point from North America. Clovis points are famous for being ‘fluted’—one of the last steps in manufacture involved striking large flakes lengthwise up the point from the basal edge. These are referred to as 'flutes' or 'channel flakes'.
The point is fluted on both faces. The annotations direct you to several shallow step terminations on the channel flake scars. Channel flakes often ended in step terminations because the geometry of the biface's surface, combined with the length of the flake, tended to cause the propagating flake to end abruptly, rather than dissipating in a feather termination.
The undetached portions of the flakes still adhering to the point are called 'hangnails' by some modern flintknappers. They consider them unsightly and try to remove them from their modern-made points. Thin ones can be snapped off, at least partly, by flicking upward with the fingernail or a thin metal tool. Some flintknappers coax water under the hangnails and then put the tool in a freezer, hoping the expansion of the freezing water will pop them off.
Taphonomic processes tend to remove small hangnails from ancient points, although deeper or thicker ones tend to remain. Stone artefact authenticators become suspicious of supposed ancient artefacts with many visible hangnails. Step terminations and hangnails often provide surfaces for adhering residues from the tool's use and soil matrix from where it was originally deposited.
This model is a ‘bullet’ core from the famous site of Mohenjo-daro in Pakistan. The facets on the core are from making microblades using a pressure technique.
A step termination is clearly visible on one face of this core. Note that the step-terminated scar is partly cut by the scars on either side. This is one strategy for removing a step termination from the surface of a core: by incrementally removing the edges of the step, and raising its height by removing mass to either side, it is sometimes possible to undercut the step with a subsequent flake. That last step was not attempted on this core because the step termination cut too deeply into the stone.
On this model we will look at a common tactic to cope with step and hinge terminations during blade production. Be sure to refer to the model's annotations.
The pattern and morphology of flake scars on the dorsal surface of this blade reflect a 'bidirectional' reduction strategy. A bidirectional core has platforms that are directly opposite each other. If a step or hinge is created when a flake is removed from one platform, the core is rotated and a flake is struck from the opposite platform, undercutting the step or hinge and removing it from the core. This can be seen on the sequence of blade removals in this model, as indicated by the annotations.
Bidirectional cores are particularly common in blade-making technologies because steps and hinges are such a common problem when attempting to remove long, narrow flakes from shallow platforms. Naviform cores from Western Asia, like the one in this model, were reduced bidirectionally, and bidirectional scars can be seen on the dorsal surface of this blade, struck from a Naviform core. A bidirectional approach was sometimes used to made microblades in Australia.
A bidirectional strategy is common in biface manufacture: steps and hinges on flakes from one biface edge can be removed by undercutting them with flake removals from the opposite edge. Refer to the annotations on this model and this model for examples of the strategy, called 'dive flaking' or 'hinge flaking'.
Dive flaking was used to produce ultra-thin bifaces, as the recovery flake tends to dip slightly when it intersects the step or hinge. The flintknapper Errett Callahan speculated that a dive-flaking strategy might be used to create an ultra-thin biface with a hole in the middle. Although this has never been achieved, if you use the cross-section and measurement tool to examine this model, you will find the biface was thinned to about 2.4 mm thick in one area.
Step and hinge ‘islands’
Despite the strategies for overcoming problematic step and hinge terminations on core faces, those strategies were not always successful.
This model is of a bifacially-flaked disc knife from the Tenerean period in the Sahara Desert, Niger. These artefacts can be exceptionally well-made, and thin relative to their width.
However, on this model, an ‘island’ of mass is visible on one face, encircled and isolated by many overlapping hinge- and step-terminated flake scars. Note that the flintknapper struck flakes from around the entire periphery in unsuccessful attempts to remove this island from the face of the biface. There are up to 9 attempts from one direction alone, as indicated by the stratified series of steps and hinges. The opposite face was successfully flattened without this problem.
Hinge and step terminations tend to proliferate on the same part of the core if flakes are struck too close to one another.
This model is a small arrowhead, also from Saharan Africa. The point was made by pressure flaking, and a series of flakes ended in step terminations, isolating an island of stone in the centre of one face.
The surface of this island is a detachment scar, as described in Workshop 4. This is a relatively common occurrence on small arrowpoints made on flake blanks because the flat detachment scar surface does not have zones of high mass to channel the crack, so it spreads out and stalls.
A flake ends in an overstruck termination when the force travels too deep to exit the core cleanly (resulting in a feather or axial termination), so it propagates right through the core and exits the other side. Some archaeologists call this a ‘plunging’ termination’, or ‘reverse hinge’. French analysts call it an outrepasse. Modern flintknappers say the flake has 'overshot'.
Another factor that leads to overstrikes is the lack of core support—the force applied to the base of the core. When a blade core, for instance, is set on a hard surface and a compression force is applied to initiate a flake, the compression causes the crack to travel parallel to the core face and exit cleanly out the bottom—an axial termination.
When compression is not applied, tensile force can take over and the crack propagates around the end of the core—an overstruck termination.
The same forces are at play in biface manufacture, and overstrikes can remove the opposite edge of a biface. In this case, the opposite edge is, in effect, the base of the bifacial core. The overshot flaking technique was used in North America and France to create thin, flat bifaces.
The flake in is model—a blade from southeast Queensland, Australia—terminated in an overstrike. Note the curvature of the ventral surface, and how the mass at the distal end of the flake is disproportionately large compared to the proximal end of the flake, and is marked by cortex and flake scars not related to the production of blades. This suggests that part of the core’s base came away with the flake, which is common with overstruck terminations.
The blade in this model also has a curvature at the distal end, but unlike the Queensland example, the distal mass is proportional to the proximal mass, and all the dorsal scars are consistent with blade production. This is an axial termination. The blade curved inward slightly to the point where the base of the core was supported. It was removed by pressure from a core similar to the one in this model.
This model is a the base of a Clovis point from North America that failed when the flintknapper attempted to remove the flute, or channel flake. As noted previously, Clovis points were fluted by striking a flake up the length of the biface as one of the last steps in manufacture.
In this example, the opposite face was successfully fluted. The trick for the flintknapper, then, was to repeat this success on the reverse face, on an appreciably thinner biface. The flute was initiated successfully but instead of propagating under the mass at the biface's centre, the crack dove through the point and lopped off the distal end.
This is a relatively common type of failure when fluting Clovis and Folsom points. Many modern knappers place a block under the tip of the point during fluting to apply compression support and help prevent overstruck terminations, but they still can occur. Analysis has shown that Folsom knappers deliberately rounded and dulled the tip of the biface prior to fluting so it could better withstand the compression support.
The difficulties involved in fluting—and the fact that it was strictly unnecessary to do this—has prompted some archaeologists to propose that the risky process was imbued with social meaning.
An axial termination occurs when the force driving the crack remains in balance right through to the bottom of the core, cleanly exiting the core face.
Part of the base of the core can be preserved at the distal end of the axially-terminated flake. This section appears squared-off for relatively blocky-ended cores, but, as noted previously, an axial termination can also include a gentle curvature—or even a feather termination—when the flake is removed from pointy-ended cores.
We examined this model of a pressure blade core previously, focusing on the step-terminated scar on the core face. Now rotate the model until you are looking down onto the core’s more bulbous end. There you can see a number of blade scars converging in a pointed configuration. These are axial terminations—the scar equivalent to the termination on this blade.
Several of the blade scars on this blade core end in similar, slightly curved axial terminations. These scars were created by indirect percussion rather than pressure and the shape of the base of the core is an edge rather than a bullet-like point.
Previously we reviewed how compression support at the base of the core can help a blade terminate axially or with a feather termination; another way to achieve this is with indirect percussion. In this case, the balance of downward and outward force can be precisely balanced by the way the punch is angled when positioned on the platform, and and expert flintknapper can produce feather or axial terminations in the absence of core support.
This model is of a ‘livre de burre’ core from the Neolithic period in France. Note that one face is marked by one long negative scar from a blade that travelled the entire length of the core. The blade ended in an axial termination on a squared-off core base, and the blade would have preserved a small part of this squared-off configuration at its distal end.
A feather termination is when a flake exits smoothly from the face of the core, without stepping or hinging. Axial terminations are a type of feather termination where the flake propagates right through the core base. Many flakes end in feather terminations prior to reaching the core base, particularly in biface manufacture, but also in some blade-making technologies.
This is an example of a chert macroblade from Central Australia hafted as a knife. It was made following a similar technological approach to the macroblade core with hinge terminations discussed at the start of this workshop. It was struck by hard-hammer percussion. Note that this macroblade is nearly flat—not curved in long section—and the flake feather-terminated on a ridge near the end of the core. This indicates that the flintknapper possessed complete mastery over the balance of inward and outward forces.