Trampling experiments on bones in fine and soft sediments
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Quaternaire
Revue de l'Association française pour l'étude du
Quaternaire
vol. 29/1 | 2018
Volume 29 Numéro 1
Trampling experiments on bones in fine and soft
sediments
Expériences de piétinement d’ossements dans des sédiments fins et mous
Lee Rozada, Ronan Allain and Jean‑François Tournepiche
Electronic version
URL: http://journals.openedition.org/quaternaire/8593
DOI: 10.4000/quaternaire.8593
ISSN: 1965-0795
Publisher
Association française pour l’étude du quaternaire
Printed version
Date of publication: 1 March 2018
Number of pages: 39-44
ISSN: 1142-2904
Electronic reference
Lee Rozada, Ronan Allain and Jean‑François Tournepiche, « Trampling experiments on bones in fine
and soft sediments », Quaternaire [Online], vol. 29/1 | 2018, Online since 01 March 2020, connection on
22 March 2020. URL : http://journals.openedition.org/quaternaire/8593 ; DOI : https://doi.org/
10.4000/quaternaire.8593
© Tous droits réservésQuaternaire, 29, (1), 2018, p. 39-44
TRAMPLING EXPERIMENTS ON BONES
IN FINE AND SOFT SEDIMENTS
n
Lee ROZADA1, Ronan ALLAIN1 & Jean-François TOURNEPICHE2
RÉSUMÉ
Few neotaphonomic studies of trampling on bones have been made, especially in fine and soft sediments. However, trampling
is an important taphonomical agent that can considerably modify a bone assemblage. Moreover, resulting bone modifications can
be mistaken with other taphonomical agents, including human butchery behavior that can have great consequences on archeological
interpretations. A better understanding of this taphonomical agent is therefore needed. Here we report the results of two trample
experiments done to understand the effects of trampling in soft clay and fine sandy sediments on modern bones. It gives a preliminary
understanding of trampling effects on bones in swampy-like environments.
Keywords: trampling, experiment, neotaphonomy, marks, swamp, clay
ABSTRACT
EXPÉRIENCES DE PIÉTINEMENT D’OSSEMENTS DANS DES SÉDIMENTS FINS ET MOUS
Peu d’études de néotaphonomie sur le piétinement d’ossements ont été faites, en particulier dans des sédiments fins et mous.
Pourtant, le piétinement est un agent taphonomique important qui peut considérablement modifier un assemblage osseux. De plus, les
modifications osseuses résultantes peuvent être confondues avec d’autres agents taphonomiques, comme le comportement humain
lors de la boucherie, ce qui peut avoir de grandes conséquences sur les interprétations archéologiques. Une meilleure compréhension
de cet agent taphonomique est donc nécessaire. Nous décrivons ici les résultats de deux expériences de piétinement réalisées dans
le but de comprendre les effets du piétinement sur des os actuels dans des argiles molles et des sédiments sableux fins. Cela fournit
une première approche des effets du piétinement dans un environnement de type marécageux.
Mots clés : Piétinement, expérience, néotaphonomie, traces, marécage, argile
1 - INTRODUCTION on archeological interpretations (e.g. McPherron et al.,
2010, 2011; Domínguez-Rodrigo et al., 2010, 2011).
Trampling by animals is an important taphonomical Several taphonomical trampling experiments on bones
agent that can considerably modify a bone assemblage. have been done to study and identify spatial movements,
Depending on several parameters (e.g. trampling dura breakage and surface marks patterns from other taphono
tion, trampler weights, soil content and viscosity, bone mical agents (Courtin & Villa, 1982; Fiorillo, 1984, 1989;
shape…), it can disarticulate skeletons, disperse, reorien Andrews & Cook, 1985; Behrensmeyer et al., 1986;
tate, break and crack bones and create marks on bone Olsen & Shipman, 1988; Blasco et al., 2008; Domín
surface (Courtin & Villa, 1982; Fiorillo, 1984, 1989; guez-Rodrigo et al., 2009). However, most of them took
Andrews & Cook, 1985; Behrensmeyer et al., 1986; place in coarse sands and knowledge of trampling effects
Olsen & Shipman, 1988; Auguste, 1994; Domίnguez- on a bone assemblage in swampy environment sediments
Rodrigo et al., 2009; Blasco et al., 2008; Denys & is lacking (A.K. Behrensmeyer, pers. com., 2016).
Patou-Mathis, 2014). The resulting bone modifications Here we report the results of two exploring experi
can be mistaken with other taphonomical agents, such ments done to understand the effects of trampling on
as breakage pattern and surface marks due to predation bones in soft clay and fine sandy sediments. Experi
or scavenge (e.g. crocodile tooth marks) and human tool ments took place during the fourth excavation campaign
manufacture or tool-assisted butchery (e.g. cut marks; in August 2013 at the Lower Cretaceous fossiliferous
Fiorillo, 1984 ; Behrensmeyer et al., 1986; Buc, 2011; Angeac-Charente locality (Charente, France). They have
Njau, 2012). The latter can have great consequences been done on the way to compare with the modifications
1
Muséum National d’Histoire Naturelle, CR2P-UMR 7207, CP 38, 8 rue Buffon, 75005 PARIS, France.
Email: lrozada@mnhn.fr, rallain@mnhn.fr
2
Musée d’Angoulême, 1 rue Friedland, 16000 ANGOULÊME, France. Email: jftbill@aol.com
Manuscrit reçu le 14/03/2017, accepté le 27/04/2017
1801-057-Mep1-2018.indd 39 21/02/18 10:5440
observed on the dinosaur bone assemblage fossilized in 2.1 - EXPERIMENT 1
the swampy-deltaic environment of Angeac (Néraudeau
et al., 2012; Rozada, 2014; Rozada et al., 2014). The first experiment focuses on the study of spatial
displacements of bones in soft clayey sediments. Ten
sheep bones (two scapulae, articulated humerus-ulna-
radius, one tibia and four ribs) have been horizontally
2 - MATERIAL AND METHODS
placed close together at the surface of soft clays in the
Angeac site (fig. 1). The soft, watery clay layer was about
Bone material has been collected in a mass grave in 50 cm thick, overlying harder clays. For one hour, five
a disused quarry near Angeac. They all belong to adult persons (one adult and four children of different ages and
individuals, not weathered and devoid of periosteum. weight) wearing boots trampled the area freely (fig. 1).
Elements have been chosen on the way to represent a
diversity of shape and size (scapulae, long bones and
2.2 - EXPERIMENT 2
ribs). Location of bones before and after experiments
have been recorded with photographs.
Fig. 1: Experiment 1, free trampling on modern sheep bones in soft clayey sediments.
Abbreviations: dist, distal fragment; H, Humérus; prox, proximal fragment; R, Rib; S, Scapula; T, Tibia; UR, Ulna-Radius. Photographs: ©L. Cazes,
MNHN, 2013.
Fig. 1 : Expérience 1, piétinement libre sur des os actuels de mouton dans des sédiments argileux mous. Abréviations: dist, fragment distal; H, Humérus;
prox, fragment proximal; R, Côte; S, Scapula; T, Tibia; UR, Ulna-Radius. Photographies: ©L. Cazes, MNHN, 2013.
1801-057-Mep1-2018.indd 40 21/02/18 10:5441
The aim of the more rigorous second experiment was to mentation, four people wearing boots or trainers have taken
study marks on bone surface left by trampling in different successively ten steps in each hole (fig. 2). To avoid any
soft fine sediments. Four sets of ten fresh bones have been sediment pollution, the tramplers washed their soles before
chosen: one scapula, one humerus, one metatarsal, one stepping each hole. After the experiment, bones were exca
metacarpal, and four ribs (one complete and large, one vated, cleaned with soft brush and water, and surfaces were
proximally broken and large, one thin and one small) of examined with a binocular magnifier and compared with
sheep and two small and thin dog ribs (fig. 2). One meta silicone molds. 1 kg of each sediment was finely sieved to
tarsal shows a pathology (see fig. 2, before experiment assess sediment components and grain size.
C1). Additionally, a fossilized dinosaur bone splinter
has been added in each set to test if trample marks can
appear on mineralized bone surfaces. The material has 3 - RESULTS
been cleaned with soft brush and acetone. As control,
sheep bone surfaces were replicated before experiment 3.1 - EXPERIMENT 1
with silicone RTV silastic 3481 and fossil bone splinter
surfaces with RTV silicone paste. During the experiment, children firstly tried to trample
Four different sediments were used in this experiment. the bones deliberately. After a few seconds of trampling,
They correspond to the four lithological units described at the bones were not visible any more, buried in a layer
Angeac-Charentes locality, in which dinosaur bones have of very fluid clays (fig. 1). During the rest of the experi
been preserved: fine light gray sands (C1), fine yellow mentation, children were playing together in a large area,
sands (C2), brown clays (C3) and dark-gray clays (C4). walking, running, jumping and sliding.
Four holes have been dug in the gray clays (C4) in the Ones excavated, bones appeared in a horizontal plane, at
Angeac site, covered by hermetic plastic bags, and filled by the limit between liquid and more resistant clays (fig. 1).
each sediment saturated in water. Bones of each set were Three bones have been highly horizontally displaced: the
positioned horizontally at the surface and covered by less tibia (T), one rib also highly reoriented (R2), and one rib
than one centimeter of sediment (fig. 2). During experi never recovered (R1). The two other ribs (R3, R4) and one
Fig. 2: Experiment 2, 40 steps on modern sheep and dog bones in fine sandy and clayey sediments. Photographs: ©L. Cazes, MNHN, 2013.
Fig. 2 : Expérience 2, 40 pas sur des os actuels de moutons et de chiens dans des sédiments mous finement sableux et argileux. Photographies: ©L.
Cazes, MNHN, 2013.
1801-057-Mep1-2018.indd 41 21/02/18 10:5442
scapula (S2) were broken. The rib R4 shows a transversal During experiment 2, we have observed that one meta
fracture, with the two fragments very close to each other podial from C4 stayed stuck on the boot of the trampler
and showing a slight vertical reorientation. For the rib R3, and was deposited outside the hole (fig. 2). After the expe
the proximal and distal fragments are present, with the riment, bones trampled in C1, C3 and C4 showed a lot
proximal one showing oblique (spiral) fracture and distal of displacements and orientation change, while they are
one being turned over (R3 prox, R3 dist). However, the limited in C2 (fig. 2). One rib from C1 has been broken
central fragment is missing (fig. 1, R3). For the scapula (transversal fracture), some bones are cracked, and several
(S2), one fragment stayed in place but rotated to a vertically little splinters has been found after sieving. One metapo
direction, and some bone splinters have been found on and dial from C4 shows an oval-shaped crushed (fig. 3).
in contact with the main part of the scapula (fig. 1, S2). Numerous typical trample marks have been observed
Finally, a fragment of the superficial layer of the proximal on bone surfaces: stripes, parallel striations and scratches
epiphysis of the tibia has been pulled off (fig. 1, T). (fig. 3A-E, tab. 1). They appear preferentially on rounded,
convex, flat or prominent surfaces of bones. Stripes are
3.2 - EXPERIMENT 2 very fine, and shallow grooves often linear and simple,
Tab. 1: Table of observations of trample marks on bones after experiment 2.
Big bold crosses indicate figured marks (fig. 3). Orientation of marks is relative to the long axis of the bone. Abbreviations: dist, distal; frag, fragment;
IC, intercrossing marks; M, mark (any kind); N, Number of bone or bone fragment; prox, proximal; St, stripe; Sc, scratch; PS, parallel striations; R, rare
occurrence of marks (one or two isolated marks).
Tab. 1 : Tableau d’observation des traces de piétinement sur les os après l’expérience 2. Les grandes croix en gras indiquent les traces figurées (fig. 3).
L’orientation des traces est relative à l’axe longitudinal de l’os. Abréviations : dist, distal ; frag, fragment ; IC, traces entrecroisées ; M, trace (tout
type) ; N, nombre d’os ou de fragment d’os; prox, proximal; St, rayure simple ; Sc, Eraflure ; PS, stries parallèles ; R, rare présence de traces (une ou
deux traces isolées).
1801-057-Mep1-2018.indd 42 21/02/18 10:5443
but sometimes doubled and/or slightly curved (fig. 3A). 29 of the 33 sheep bones or bone fragments (85 %),
Parallel striations are sets of parallel fine linear stripes exhibit trample marks. 15 of them (39 %) show more than
(fig. 3B-D). They can appear as isolated patches, but one or two isolated marks (tab. 1). Most of the trample
often as elongated patches along bone shafts and ridges, marks are stripes (67 %), then parallel striations (45 %)
with striations being oriented perpendicular or oblique to and scratches (42 %). On 6 bones (18 %), marks have
the long axis of the shaft (fig. 3B, D; tab. 1). Scratches been found intercrossed (fig. 3C). The surface of almost
are shorter, deeper and wider marks. They are sometimes all bones trampled in fine sands (C1, C2) and dark clays
associated with (that means parallel to or as a continua (C4) have been marked, while few isolated marks have
tion of) stripes or parallel striations (fig. 3E, see arrow). been observed on 4 bones trampled in yellow clays (C3).
In some cases, two or more marks are crossing each other Dog ribs and fossil dinosaur splinters does not exhibit
(fig. 3C; tab. 1). any surface modifications.
Results of sediment sieving show that the compo
sition of each sediment includes mostly clays and fine
silts (< 50 µm), silty to fine sand quartz grains (50-100
and 100-250 µm) and few pyrite, calcareous, lignite and
quartz coarser grains (>250 µm; tab. 1).
4 - DISCUSSION
Trampling done in the two experiments has conside
rably modified the artificial bone assemblage. Indeed,
bones have been horizontally and vertically displaced,
their vertical and horizontal orientations have changed,
they have been broken, knocked, and their surfaces have
been affected by trample marks.
Bones have been horizontally displaced from several
centimeters to decimeters, and probably more than one
meter for the missing bones of the experiment 1 (R1, R3).
Horizontal reorientation has reached at least 180° (fig. 1,
R2). However, vertical displacements (few centimeters)
and reorientation (tens of degrees) of bones is more
limited, probably due to the thin thickness of the fluid
sediment layer in the two experiments. These displace
ments and position changes occurred by driving a bone,
carrying a stuck bone to the foot (fig. 2, C4) or moving
the soft soil. The limited displacements and orientation
changes in C2 compared to other sediments are probably
due to the weaker fluidity of this sandy sediment. Tram
pling in soft clays can considerably displace and reorient
bones, and even transport them over short distances.
Only ribs and scapulae have been broken. That prefe
rential breakage pattern is due to their flattened shape and
less compact/density compared to limb bones (Eberth
et al., 2007). The recurrence of fragments of the same
broken bone preserved in close proximity indicates an
in-situ breakage. An unexpected result is the breakage of
the superficial part of the proximal epiphysis of the tibia.
As a result, the proximal epiphysis seems to be abraded
and mimic erosion due to transport. Thus, trampling in
soft clays can break in-situ preferentially less compact
bones and can mimic abrasion.
Fig. 3: Bone surface modifications after experiment 2. Morphology, localization and orientation of traces
(A-E) Trample marks. (A) Double stripe. (B) Elongated patch of parallel found on bone surfaces are very similar to previously
striations along a ridge. (C) Two intercrossing patches of parallel stria
tions. (D) Patch of parallel striations on shaft. (E) Scratch marks. Scale described trample marks (Andrews & Cook, 1985;
bar: 1mm. Photographs: ©L. Cazes, MNHN, 2013. Behrensmeyer et al., 1986; Olsen & Shipman, 1988).
Fig. 3 : Modifications osseuses de surface après l’expérience 2. (A-E)
Traces de piétinement. (A) Rayure double. (B) Patch allongé de stries
They appear preferentially on convex, flat or prominent
parallèles le long d’une crête. (C) Deux patchs de stries parallèles parts, where the siliceous grains are more able to be
entrecroisés. (D) Patch de stries parallèles sur une diaphyse. (E) pushed across the bone (Behrensmeyer et al., 1986).
Éraflure. Échelle : 1 mm. Photographies : ©L. Cazes, MNHN, 2013.
1801-057-Mep1-2018.indd 43 21/02/18 10:5444
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