Workshop 4 - Platforms and Other Attributes
In Workshop 3, we examined the attributes of flake terminations, particularly hinges and steps, but also overstruck, axial, and feather terminations.
In Workshop 4 we will look at platform types that occur on flakes, plus other interesting attributes such as finials, detachment scars, and demicones.
Refer to 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.
Single Facet Platform
A core is struck on a blow on the platform to remove the flake. A part of the core's platform breaks away and is found at the flake's proximal end. The nature of the platform surface on the flake and the core can tell us a great deal about the stone-flaking strategy.
When a blow is struck onto a relatively flat, unmodified surface, a single-facet platform is created. Some archaeologists refer to single facet platforms as 'plain' platforms, to distinguish them from flaked, or 'facetted', platforms.
In many cases, the unmodified platform surface was a prior flake scar.
Single-facet platforms are the most common platform type, and, depending on the technology, they can dominate flake assemblages.
The macroblade core in this model has a broad, relatively flat surface. The surface is a negative flake scar from when the top of the chert nodule was struck off at the start of reduction. Rotate the core and look down on the platform and visualise the single-facet platforms that must occur at the proximal ends of the macroblades struck from this core.
Now rotate this model of a chert blade and look directly down onto the single-facet platform surface. The platform on the core was a flat surface without any prior modification by flaking.
The black line across the platform is a pencil mark made by the analyst marking out the axis for measuring the platform's depth.
Multi-Facet Platform
When the blow that detaches a flake is struck onto a surface that was prepared by first removing smaller flakes, those smaller flake scars can be seen on the flake's platform. Archaeologists call this a 'facetted' or 'multi-facet' platform.
This form of platform preparation might be done to alter the angle between the platform surface and the core face, or to strengthen the core edge prior to the percussion blow. Multi-facet platforms are common attributes on flakes produced in 'on-edge' percussion, when a blow is struck directly onto the platform edge, such as in biface thinning.
Rotate this model of a fan scraper and zoom in. The blow was struck onto a platform that was first prepared by striking off many smaller flakes.
This microblade from Australia has several small tiny step-terminated scars across the platform surface. These were likely produced in a raking action towards the platform surface to remove the platform's thin, attenuated edge. This is a way to strengthen the edge for the percussion blow. It may also have been done to partly reduce the ridge on the platform surface in this location.
Now review this core and this core. Rotate each core so that you are looking down onto the platform struck to produce the large flake scar on the core face. You will see the distal ends of small flake scars created in retouching the platform to steepen it, prior to removing the large flake. The proximal ends of the flake scars are on the flake struck from the platform, and were removed from the core.
This flake is the one that was struck from the second of these cores, and you can see the the proximal ends of the retouching scars on its multi-facet platform.
Dihedral Platform
Bifacial cores have flakes removed from two adjoining faces. Sometimes the arris (ridge) between two adjacent flake scars is fortuitously placed to remove a flake to the opposite surface. The raised ridge can be an ideal platform because its height makes it easy to strike.
When the flake is removed, the point of force application (PFA) can be seen directly on the arris between the two flake scars. Two scars are present on the platform, so it is referred to as 'dihedral'.
Cortical Platform
Archaeologists call the natural outer surface of a rock 'cortex'. A flake detached by striking this surface has a cortical platform. Rotate this model of a Tula adze from northwest Queensland, Australia to see an example of a cortical platform.
The reduction sequence that produced tula adzes in northwest Queensland involved striking flakes off a chert cobble in series, much like slicing a loaf of bread. And, in the same way a slice of bread has crust on the edge, each tula flake has a cortical platform. The models of tula adze slugs available here and here also have cortical platforms.
Finials on Flake Scars
A finial occurs on hinge terminations and bend-snaps. The finial itself frequently breaks from the parent flake and is one element making up the abundant shatter produced in stone-flaking.
A finial is formed when the crack, just as it exits the core, changes direction and creates a thin shelf or projection. When the flake is terminating in a hinge, the main crack front turns abruptly towards the core face. If it then shifts direction and runs parallel to the core face, in the original direction of the main crack, the resulting finial is called 'retroflexed'.
If the finial runs in the opposite direction of the main flake, essentially rolling back over onto its dorsal surface, the finial is called 'inflexed'.
In Workshop 3 you examined hinge terminations on this model, a chert blade core from France. Refer to the model's annotation for hinge termination 1. At the right-hand part of the hinge, you can see how the fracture rolled back over onto itself. This is an inflexed finial.
On the left-hand part of the hinge, you can see how the fracture started to run in the same direction as the parent flake, extending up the arris in this location. This is a retroflexed finial.
Arrises have a tendency to ‘channel’ the nearly-spent forces driving crack propagation, and termination ‘run-ons’ up arrises, including retroflexed finials as in this example, are very common. They are essential attributes to observe when reconstructing the order that flake scars were produced.
This model is a modern-made chert bifacial point from the Khambhat region of India. To see the finials, access the annotations for this model using the sidebar.
The hinge termination of the main scar spun-off an inflexed finial, which itself terminated in a hinge and spawned a second inflexed finial before finally ending in a feather termination. Compound finials like this are common and attest to the often complex and chaotic way that a crack exits the face of a core.
This model is of a chert retouched flake from Song Gupuh Cave in East Java. The finial is shown by a pin accessible using the annotations.
The platform struck to produce this scar was removed by steep unifacial retouching. Click on the pin and the model will rotate to show the finial. Note how the flake hinged in this area, but the main crack changed direction to run in the opposite direction for a short distance, creating a hook-shaped profile. This is an example of a retroflexed finial.
The edge of a retroflexed finial can be razor sharp. Since they tend to occur towards the middle of a stone tool's face, rather than at the edge, they can be dangerous to hold in the hand. Most of this final was broken off, perhaps by the person who used the tool.
Detachment Scar
Stone tools were often made on flake blanks. The ventral surface of the flake, when visible on a finished tool, is referred to as the 'detachment scar'.
A flake struck onto the ventral surface of a flake blank will preserve that ventral surface as a scar on its dorsal surface. That is also referred to as a detachment scar.
Detachment scars on tools and flakes are evidence that cores in the assemblage were reduced to produce flake blanks for tools.
The size of the detachment scar remaining on a discarded tool depends on the amount of reduction that occurred to the ventral surface of the flake blank. For instance, when a flake is reduced bifacially into a tool, the detachment scar is often eliminated entirely.
This model is a flint arrowhead from Neolithic Denmark. It is referred to as a 'transverse' arrowhead because it was hafted on the arrow shaft with the sharp edge as the business end. The detachment scar on this point is unmodified. Note that the direction of the undulations is subtly visible on the detachment scar, but you may have to go into the sidebar and convert the render to metallic to see them. The undulations show how the tool was oriented within the flake blank.
The lateral edge of the flake blank was the cutting edge of the transverse arrowhead. Now look at this model of an indirect percussion blades from about the same time and place. Compare the arrises on the dorsal surface of the arrowhead to the parallel arrangement of arrises on the blade—blades like these were broken into sections and retouched by ‘backing’ to produce transverse arrowheads.
The arrowhead in this model, from Saharan Africa, has a raised island surrounded by step-terminated flake scars, as we reviewed in Tutorial 3. The surface has a flat profile and is likely a detachment scar—a remnant of the original ventral surface of the flake blank it was made from.
Demicone
In this model of an English gunflint there are two cone-shaped features visible at either end of the dorsal surface, shown by pins in the annotations. These are, in fact, the tops of hertzian cones, and the exposed parts are, technically, umbos.
The features are called 'demicones' by archaeologists, and they are created in truncating flakes by percussion. The truncation technique involves placing the flake flat on a hard surface and striking the top with a hard hammer percussion blow. In prehistory, the purpose was usually to section the flake into pieces with useful, steep-sided edges.
This gunflint was made in the historic period, and in this case the purpose was to section a blade into roughly square or rectangular pieces with one sharp side—the lateral edge of the blade—which became the working edge when mounted in the gun lock.
To section a blade, it was rested on a metal stake set in the flintknapper’s workbench, and the surface was struck with a steel hammer, initiating the truncation fracture. To see the process of gunflint making in action, view this historic video. Blades are truncated and trimmed starting at about 2:20 in this film, and demicones are clearly visible on the gunflint shown at 2:36.