Technology and Terminology of Knapped Stone - IRIT

Indirect percussion
Strangely enough, there is no indisputable evidence for blade debitage using a punch
before the Mesolithie. The distinctive features of such blade products are halfway between those
of debitage by direct percussion and by pressure-flaking, and are sometimes difficult to
distinguish from either of the two. Indirect percussion is well adapted to a plain striking platform,
only slightly inclined on the debitage surfaces. The flaking angle is almost 90°, and is one of the
criteria by which this technique can be distinguished, in a long debitage series, from direct
percussion with a soft hammer.
We have chosen to illustrate just three examples.
• Debitage starting from a single striking platform, on a pyramidal core (fig. 29 : 1).
With this kind of pattern, the blade products tend to curve.
• Debitage starting from two opposite striking platforms on a cylindrical or prismatic
core (fig. 29 : 2). Debitage can be performed either by alternating the striking platforms for each
removal, or by removing a series of products from first one platform and then the other. The
products obtained in this manner will be rectilinear.
• Crossed debitage: the two debitage surfaces are parallel, but the directions of
percussion are orthogonal (fig. 29 : 3).
Blade debitage can be carried out from one or more striking platforms, which can be
cortical, plain, or prepared. In the latter case, preparation will involve either a short series of two
or three blades, or a single blade as is common in the Magdalenian (especially the Upper
Magdalenian), where a projection is created on the edge of the striking platform. Part of this
projection is removed along with the blade, which will then have a butt with a spur (fig. 62 : 8).
Pressure debitag e o f blade s
Pressure debitage applies only to the manufacture of blades and bladelets. Identified
relatively late 73
, this technique has, in the last few years, become more and more widely
documented, in space and in time. The most impressive area of distribution covers the Middle
and Far East. Until very recently, it seemed that pressure debitage of blades followed percussion
debitage of blades, and appeared only 12000 years ago, in Japan. At present, its invention can be
7 4
traced to a Sibero-Sino-Mongolian region of Asia, about 25000 years ago . Invented by
hunter-gatherers, this type of debitage moreover proves to be a valuable technical marker, thus
providing added information about the peopling of North America 75
.
Heat treatment, already known to make pressure-retouching easier, is also often
associated with pressure debitage, at least on flints and chalcedonies.
In the case of bladelet manufacture, the pressure causing the fracture wave can be applied
directly with a short hand-crutch (fig. 30 : 1), or with a longer shoulder-crutch, whose "passive"
end is held firm under the arm or presses against the shoulder (fig. 30 : 2). For longer blades, the
pressure is applied with a pectoral (fig. 30 : 4) or abdominal crutch (fig. 30 : 3a and 5). The point
that applies the pressure can be of ivory or antler, which were superseded by metals when these
appeared. As the size of the products increases, it becomes more and more necessary to stabilize
the core (fig. 30 : 3b).
Pressure debitage therefore requires more equipment than percussion debitage : a device
to immobilize the core, a composite tool to apply pressure. Furthermore, the frequent occurrence
of heat treatment testifies to complex and well mastered skills. However, in spite of the
improvement heat treatment can bring about, pressure debitage requires raw material that is both
fine-grained and homogeneous. Obsidian is certainly the best suited material for this type of
debitage.
Owing to the fine nuances of movement and force that can be applied, and to the
accuracy with which the pressure point can be positioned, pressure debitage leads to maximum
73 For the background history, see Tixier, 1984 ; 57-70.
74 Inizan, 1991.
75 Inizan, Lechevallier, Plumet, 1992.
76