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Forensic Anthropology Population Data

The taphonomy of human remains in a glacial environment

Marin A. Pilloud a,*, Mary S. Megyesi b, Martin Truffer c, Derek Congram d

a Department of Anthropology, University of Nevada, Renob Central Identification Laboratory, Defense POW/MIA Accounting Agencyc Department of Physics, University of Alaska, Fairbanksd Trudeau Centre for Peace, Conflict, and Justice, University of Toronto

A R T I C L E I N F O

Article history:

Received 22 May 2015

Received in revised form 17 November 2015

Accepted 23 January 2016

Available online xxx

Keywords:

Forensic anthropology

Glacial taphonomy

Glacial movement

Glacial dynamics

A B S T R A C T

A glacial environment is a unique setting that can alter human remains in characteristic ways. This study

describes glacial dynamics and how glaciers can be understood as taphonomic agents. Using a case study

of human remains recovered from Colony Glacier, Alaska, a glacial taphonomic signature is outlined that

includes: (1) movement of remains, (2) dispersal of remains, (3) altered bone margins, (4) splitting of

skeletal elements, and (5) extensive soft tissue preservation and adipocere formation. As global glacier

area is declining in the current climate, there is the potential for more materials of archaeological and

medicolegal significance to be exposed. It is therefore important for the forensic anthropologist to have

an idea of the taphonomy in this setting and to be able to differentiate glacial effects from other

taphonomic agents.

� 2016 Elsevier Ireland Ltd. All rights reserved.

Contents lists available at ScienceDirect

Forensic Science International

jou r nal h o mep age: w ww.els evier . co m/lo c ate / fo r sc i in t

Glaciers cover approximately 680,000 km2 of the world and canbe found on every continent except Australia [1]. Glaciers willgradually release and expose once hidden artifacts of medicolegaland archaeological significance as part of their normal massturnover process. This process is accelerated in the current climate,which leads to a general loss of glacier area globally [2]. In fact, thereduction in glacier mass has led to the discovery of many newarchaeological artifacts and has garnered renewed interest in thefield of glacial archaeology [3]. Melting glaciers have alsouncovered human remains of archaeological [4,5] and historicforensic significance [6].

A cold or frozen environment has the potential to alter objects;and, there is a body of literature focusing on these changes inorganisms (e.g. [7–9]). However, a glacial setting is uniquelydynamic and has the potential to significantly alter human remainsbeyond the typical effects of cold temperatures and freezing.Glacier movement and flow is a complex process that produces(often) destructive forces on remains and artifacts, and can affectwhere these materials are ultimately recovered. This unique set ofenvironmental parameters can leave a characteristic taphonomicsignature on objects subject to glacial forces. Glacial taphonomydiffers from the effects of aquatic or terrestrial taphonomy.

* Corresponding author at: 1664N. Virginia St University of Nevada, Reno Reno,

Nevada 89957-0096. Tel.: +1 775 682 7693.

E-mail address: mpilloud@unr.edu (M.A. Pilloud).

Please cite this article in press as: M.A. Pilloud, et al., The taphonom(2016), http://dx.doi.org/10.1016/j.forsciint.2016.01.027

http://dx.doi.org/10.1016/j.forsciint.2016.01.027

0379-0738/� 2016 Elsevier Ireland Ltd. All rights reserved.

Without proper context and/or understanding of the conditionsand forces acting within glacial environments, the effects on boneof glacial taphonomy may be confused with other more commonand familiar processes.

The focus of this study is to describe the effects of a glacialenvironment on human remains of a forensic nature in relation totheir causal agent, effectors, and actor. The characteristic damagerelating to a glacial environment described herein includes (1)movement of remains, (2) dispersal of remains, (3) altered bonemargins, (4) splitting of skeletal material, and (5) extensive softtissue preservation and adipocere formation. These alterations arediscussed with specific references to the processes that causedthem and how, when combined, they are unique to a glacialenvironment. The formulation of this taphonomic signature isbased on human remains recovered from Colony Glacier, Alaska, in2012 and 2013, which were subsequently brought to the DefensePOW/MIA Accounting Agency–Central Identification Laboratory(DPAA-CIL) for analysis.

1. Taphonomic agents within a glacial environment

1.1. Glacier dynamics

The dynamics of glaciers is reviewed first because of itsrelevance to glaciers as a unique taphonomic agent. Glaciers formon land where snow accumulation is greater than melt. Snow thatsurvives to the following year is known as firn. Firn undergoes

y of human remains in a glacial environment, Forensic Sci. Int.

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metamorphosis either through melting and refreezing, or throughthe pressure and compaction of the overlying snow, or both. Theend of this process (firnification), normally after several years, isthe transformation of firn into glacier ice [10].

A typical valley glacier will amass snow in the higher altitudes,in an area known as the accumulation area. The nature of snowaccumulation can lead to a layered structure with clear stratifica-tion. Downslope of the accumulation area is the equilibrium line,where the loss of ice is equal to the gain of ice. Below this line is theablation area, where ice is lost and the surface area can be coveredin melting ice [11]. Ablation is the loss of snow and ice from theglacier predominantly through melting; however, other processescan contribute to ablation, including wind erosion, avalanche, andsublimation [12]. Glaciers terminating in a water body (lake orocean) will also lose mass through frontal ablation, which is acombination of calving (mechanical break-off of ice) and subaque-ous melting. Fig. 1 illustrates these various areas in a characteristicvalley glacier.

Once formed, the weight of the glacier ice causes the glacier toflow, and this motion is in fact one of the defining characteristics ofa glacier [13]. Glaciers move through internal deformation andbasal sliding. Internal deformation is the result of stresses fromweight and gravity that cause the lower layers to behave in aplastic manner. Deformation is greatest in areas of high stresses;that is, near the bottom and sides of the glacier. Glacier velocitiesare highest near the center lines, away from the margins [11]. Theplastic nature of the ice allows the ice to flow around largeobstacles [13]. This plasticity also leads to the deformation ofthe stratigraphic layers formed by annual snow accumulation[11]. As glaciers move across irregular terrain, the less plastic andmore brittle top surface of the glacier may fracture and formcrevasses [14]. The other manner in which glaciers move is basalsliding, which is the movement of a glacier over underlying bedrockfacilitated by meltwater [11]. Glacial flow, or motion, can be quitecomplex and is influenced by multiple factors: size of glacier, slope ofthe land, and temperature [14], although most glaciers in non-polarareas are at the pressure-dependent melting point. Smaller glacierscan move several meters per year; however, the fast part of a largerglacier can move between 50 to well over 1000 meters a year. Thefastest glaciers are those that terminate in tidewater.

As geologic agents, glaciers erode, transport, and depositmaterials they encounter. As glaciers move, they work to erodematerials around them [14]. The bottom layer of the glacier is fullof debris, which allows the glacier to abrade the surface below it[13]. Through this process of erosion, glacial striae (scratches) orgrooves (deep scratches) are formed on underlying rock [14].Glaciers can be quite large, and are therefore capable of carrying a

Fig. 1. Illustration of a typical valley glacier. Based on Hooke [10] and Hambrey and

Alean [11]. Arrows within the glacier represent trajectory lines for deposited

materials.

Please cite this article in press as: M.A. Pilloud, et al., The taphonom(2016), http://dx.doi.org/10.1016/j.forsciint.2016.01.027

great amount of material. Materials of all sizes can be transportedin one of three areas: supraglacial load is the material on top of theglacier, the englacial load is the material frozen inside the glacier,and the subglacial load is the material at the bottom of the glacier.Finally, a glacier can deposit materials at the glacier terminus.Materials can either be directly deposited by the ice or can beexposed by water action as the result of melting ice [14].

1.2. Glaciers as taphonomic agents

Gifford-Gonzalez [15] describes taphonomic agents in terms ofcausal agent, effector(s), and actor(s) all working together to alterdeposited materials. In the glacial setting, human remains aresubject to damage caused by glacial motion (causal agent); glacialload, surrounding bedrock, and ice (effectors); and the glacier itself(the actor). Each of these agents will alter the bone in differentways.

The causal agent, glacial movement through internal deforma-tion and basal sliding, can have several effects on human remains.First, remains can, and will be, moved from their original locationof deposition. This rate of movement can be quite fast or slowdepending on deposition location on the glacier, as certain areaswill move at different rates. Glaciers in different climates move atdifferent rates with the highest rates of motion generally found inmarine climates with large mass throughput. As remains becomeexposed and deposited by the glacier, there is additional potentialfor the movement and spread of remains; however, this factor willbe discussed later as it is largely influenced by the actor, or theglacier itself, and not necessarily movement as a result of internaldeformation or basal sliding.

The effect of glacial movement on human remains also dependslargely on where the remains are deposited. If they are deposited inthe ablation area, the remains will be buried in seasonal snow pack,but will be exposed to the atmosphere during each melting season,while being carried towards the glacier front. Remains will besubject to large seasonal temperature fluctuations and repeatedfreeze-thaw cycles. If remains are deposited in the accumulationarea, they will quickly be buried and isolated from atmosphericinfluences. In a temperate glacier, they will be preserved at themelting point and will not be subject to large temperature cycles.Over the years they will travel downglacier in a trajectory that firstincreases in burial depth and then reemerges at the surface in theablation area (see Fig. 1). The higher up on the glacier the trajectoryoriginates, the longer the remains will stay buried. A longtrajectory also results in great burial depths, which exposesremains to high pressure and differential stresses, which increasesdispersal and possible alteration. An example of deep burial andlong transport distances in given in Jouvet et al. [16]. Glaciers thatend on land will always reveal buried objects; the process will beaccelerated in a warming climate. However, glaciers terminating inwater might shed ice containing remains into a proglacial lake orthe ocean, particularly if burial occurred at high elevations in theaccumulation area.

The causal agent (glacial movement) can involve the effectors(glacial load, surrounding bedrock, and glacial ice). As the glaciermoves, the remains can come into contact with the variouseffectors, which have the potential to abrade, polish, crush, round,break, chip and pulverize skeletal material. Abrasion of this naturehas been interpreted as the cause of damage seen on mammothand other faunal bones in a Paleolithic site [17]. Similar damagehas also been seen on the rocks within glacial ice, in addition to thedamage done to the underlying bedrock [18].

Finally, the actor, the glacier itself, can result in various skeletalchanges as elements are subject to the intrinsic factors of theglacier. These factors could include cold temperatures, freezing,the freeze-thaw cycle, and the process of deposition. First, cold

y of human remains in a glacial environment, Forensic Sci. Int.

Fig. 2. Location of crash site (black star) and recovery area (white star) on Colony

Glacier, Alaska. Inset Alaska map based on map from www.hist-geo.com; Colony

Glacier image (Image: Landsat ETM + scene LC80680172015120, LGN00, USGS,

Sioux Falls, 1/20/2015).

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temperatures can influence the manner and rate of decomposition.Frozen remains decompose from the outside in, as opposed tounfrozen remains that decay from the inside out. In cold climates,internal microorganisms are killed, or growth is greatly slowedduring the freezing process; therefore, the outside of the body isfirst directly exposed to microorganisms as it thaws [19]. The rateof decomposition is also affected by temperature [20–22]. Lowtemperatures slow bacterial reproduction, thereby impeding anddelaying the decay process. In addition to slowed decay, coldtemperatures can preserve soft tissue through sublimation, orfreeze-drying [23,24]. Amazingly well-preserved remains havebeen found in these conditions, such as Otzi in the Italian Alps [25],human remains in Scythian tombs in Siberia [26], the ‘‘IceMaidens’’ of Peru [27], and a woolly mammoth carcass found inRussia dating to 39,440-38,850 cal BP [28]. Therefore, remainsfound in a glacial (cold) environment have the potential to exhibitextensive preservation and abnormal (at least as compared totemperate climates) patterns of decomposition.

In addition to affecting decomposition and preservation, coldtemperatures can alter skeletal material. A wet matrix that isfreezing typically expands more than 9% due to the formation of icecrystals [18]. Histological analysis of frozen human bone foundmicrofracturing at the Haversian canals that were related to thefreezing process and liquid expansion [29]. Surface fractures alsohave been demonstrated on bone that has been frozen [30]. Addi-tionally, experimental work with frozen faunal bones demonstrat-ed that when bones are frozen their fracture properties may beaffected [31].

Remains are also likely to be periodically exposed and re-covered, particularly as they move down the ablation area of theglacier prior to recovery. This process could subject elements todamage relating to freezing and subsequent thawing. A study byCalce and Rogers [32] found that cracking, flaking, and wedginghad occurred as a result of the freeze–thaw cycle on pig crania.Freezing and the freeze–thaw cycle likely present in a glacialenvironment have the potential to fracture remains in character-istic ways. In fact, Gaudio and colleagues [33] describe postmortemdamage to human remains in a glacial environment that includesextensive cracking and fracturing, which they attribute to theunique environment of the glacier.

The actor, or glacier, in addition to altering decomposition ratesand creating fracture patterns, can affect the dispersal of remainsas they are becoming exposed and deposited. Remains can eitherbe moved by the glacier ice directly and exposed through meltingof the ice, or they can be moved by melt and rain water once theyare exposed in the ablation area. In extreme cases, exposedremains could be flushed by water and moved to the bottom of theice through the glacier drainage network. This would result inextreme alteration of any material; however, it is unlikely thatsuch material would ever be found and identified. Furthermore, aselements become exposed in the ablation area, they can thaw andbe subject to more typical decomposition processes. Micozzi [34]found in a study using rats that the freezing and thawing ofremains led to faster disarticulation than in fresh-killed controls.Such a quick disarticulation could lead to more extensive dispersal.A final consideration is that as a result of dispersal and fracturing,the elements can present with different taphonomic signatures, asthey are exposed to different local conditions.

2. Taphonomic changes

Various taphonomic changes have been identified as beingcharacteristic of a glacial environment. Many of these changes arethe direct result of glacier dynamics; however, some are related toa cold environment. A taphonomic signature for a glacialenvironment has been developed based on observations from a

Please cite this article in press as: M.A. Pilloud, et al., The taphonom(2016), http://dx.doi.org/10.1016/j.forsciint.2016.01.027

case study from Colony Glacier in Alaska. Each of the taphonomicchanges is discussed below with specific reference to its presumedcause and examples are given from the case study.

2.1. Colony Glacier, Alaska

This case consists of elements recovered by the DPAA-CIL in2012 and 2013 on Colony Glacier, Alaska. The remains areassociated with a 1952 crash of a U.S. C-124 military aircraftcarrying 52 personnel. The crash site of the plane associated withthis case was well-known at the time of the incident and waslocated at a high elevation (�2,400 m) in the accumulation area ofthe glacier. However, weather conditions prevented any sort ofrecovery after the accident, and remains would have quickly beenburied. The location of the plane was subsequently lost, and it wasnot until 2012 that wreckage was spotted at a locationapproximately 18 km away (downslope) from the reported crashsite [35]. The wreckage was located at the end of Colony Glacier inthe ablation area where the glacier was calving into Lake George(Fig. 2).

During the 2012 recovery, all skeletal remains and materialevidence that were visible on the surface of the glacier wererecovered. Within one year, several new elements had beenexposed and a second recovery was required. The 2013 recoverybrought back additional skeletal remains and material evidence, allof which were exposed as the result of one year of glacialmovement, and it is thus known that no prolonged exposure at theglacier surface had occurred. Thus far, the remains of 19 individualshave been identified, predominantly through mitochondrial DNAanalysis. Future recoveries are planned as more remains areexposed in the ablation area. Osteological analysis conducted onthe initial individuals recovered from the glacier documentedpostmortem alterations throughout the remains believed to be theresult of the glacial environment.

2.2. Movement

The remains associated with this crash moved approximately18 km from the point of impact to the recovery location over a span

y of human remains in a glacial environment, Forensic Sci. Int.

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of 60 years. That is an average movement of 300 meters a year. Thisrate of movement suggests that the crash occurred on a relativelyrapidly moving part of the glacier, likely towards the center awayfrom lateral areas of friction. It is likely that the crash was quicklycovered by snowfall, which allowed it to integrate into the glacierand also made it invisible to subsequent search efforts.

Along with the human remains, aircraft wreckage and otherassociated artifacts were transported downglacier. While not allglaciers will move this fast, and the specific location within aglacier will determine the rate of movement, movement from theinitial area of deposition is one characteristic sign of inclusion in aglacial environment. This finding is a result of what has beendefined as the causal agent, or glacial movement.

2.3. Dispersal

As remains are exposed and deposited by the glacier they aresubject to dispersal over the landscape and the glacier surface. Thisis a result of properties relating to the glacier itself, as the actor. Thedegree of dispersal over the landscape will differ for each casebased on several factors (e.g. temperature, size of glacier, rate ofmovement, maximum burial depth, etc.). In a forensic contextother factors can play a role in dispersion such as perimortemtrauma. Perimortem skeletal fractures can lead to greater degree ofdistribution across the landscape as the remains are already in afractured state prior to exposure.

Such is the case with the Colony Glacier remains. Severalelements associated with this recovery were fractured during theperimortem interval as a result of the initial aircraft crash.Elements that could be re-fit during osteological analysis wererecovered from various proveniences. For example, four portions ofa fractured mandible belonging to a single individual wererecovered in four different locations with a total spread ofapproximately 7 meters. These fractured elements presenteddifferent coloration as well, due to their various locations withinthe glacier and therefore differential exposure to, for example, thesun, which causes bleaching (Fig. 3). Several other fragmentedelements were recovered from multiple locations and could be re-fit during laboratory analysis, including a fractured maxilla, leftinnominate, and right humerus, each recovered from twoproveniences; and a left femur with fragments in three differentrecovery units. Additionally, a fractured femoral head wasrecovered in 2013 and was found to re-fit to a proximal femurrecovered in 2012 (Fig. 4).

While the remains of 19 individuals could be identified, themajority of the elements recovered from Colony Glacier in

Fig. 3. Fractured mandible from Colony Glacier, Alaska found in four different

locations, this includes the three fragments seen here as well as a premolar.

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2012 and 2013 were found to belong to a single individual. It islikely that the remains associated with this individual remainedlargely intact while traveling from the original crash site to therecovery location over 60 years of glacial movement. As remainswere exposed in the ablation area, it is then likely that they werespread across the landscape (Fig. 5).

2.4. Altered bone margins

Several elements displayed altered margins that we argue is theresult of the effectors (glacial load and ice). As a result of beingincorporated into glacial firn and subsequent compaction andmetamorphosis into glacial ice, materials within the glacier canexperience shearing, abrading, grinding, and crushing forces. Thisprocess can expose the underlying trabecular bone and fray orcrush the outer cortical bone. There is also an area on the corticalbone next to the fracture margin that shows abrasion andscratching into the cortical bone (Fig. 6). Frayed cortical bonecan be more obvious in flat bones where the trabecular bone is notalso visibly involved, such as in the scapula or the ilium (Fig. 7). Inaddition to the crushing, grinding, and abrasion, damaged longbone ends appear to be sheared, having an even and planeappearance (Fig. 8). This characteristic damage could be the resultof plane shearing from ice, exposure of bone ends in the glacier, orboth.

While some of these alterations, particularly the crushed longbone ends (see Fig. 6) can look similar to carnivore modifications,taphonomic changes resulting from a glacial environment can bedifferentiated from animal scavenging in several ways. Skeletalremains with carnivore damage tend to have pits, punctures,scoring, and furrows. Moreover, postmortem changes from

Fig. 4. Right femur recovered from Colony glacier. The femoral shaft was recovered

in 2012 and the femoral head was recovered in 2013. Photo credit A. Hauer.

y of human remains in a glacial environment, Forensic Sci. Int.

Fig. 5. Map illustrating the distribution of single individual in recovery area on Colony Glacier, Alaska.

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carnivores typically have margins that are irregular in nature,rounded, and have no uniform pitch from the inner to outer table ofbone [36]. In contrast, taphonomic changes due to a glacialenvironment tend to be more regular in nature, and will not havethe associated pits, punctures, or scoring from teeth or claws. Thetype of postmortem changes to the ends of many long bonesrecovered from the Colony Glacier are even and plane inappearance. Such damage is likely the result of shearing, crushing,

Fig. 6. Epiphyseal ends of long bones. Top row: Left proximal (left) and distal femur

(right) with crushing of cortical bone and exposure of trabecular bone. Bottom row:

proximal left tibia with abraded cortical bone (left), and crushing and exposed

cortical bone (right). Photo credit A. Hauer.

Please cite this article in press as: M.A. Pilloud, et al., The taphonom(2016), http://dx.doi.org/10.1016/j.forsciint.2016.01.027

and plane forces from glacial load and ice as opposed to crushingforces alone, as can be evident in cases of carnivore damage.

That is not to say that carnivore damage cannot exist in a glacialenvironment, and in fact both types of taphonomic agents couldwork on the remains. It is therefore important to evaluate the timethat the remains have been exposed, possible animal access to theremains, and the appearance of the damage when making a finalassessment as to cause of postmortem damage. For example,remains at Colony Glacier were not exposed for a long period oftime, given the surveys of the area and the exposure of the remainsfrom 2012 to 2013. Moreover, they were exposed on the glaciersurface in a relatively unstable portion of the glacier near LakeGeorge where there was active calving of the glacial ice and manycrevasses. DPAA personnel in the field reported mountain goatsand bears in the general area; however, scavengers were notreported on the glacier. It seems unlikely, in this case that thepostmortem changes we describe here were caused by carnivoresor other scavengers.

Fig. 7. Left and right innominates and left scapula (from left to right) from with

frayed margins.

y of human remains in a glacial environment, Forensic Sci. Int.

Fig. 8. Lateral view of proximal right and left tibiae of the same individual with

plane shearing. The tibiae are in anatomical position. Photo credit A. Hauer.

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2.5. Splitting of skeletal elements

Characteristic splitting of bone ends was observed on severalskeletal elements. This was most noted in the clavicles and ribs(Fig. 9). Such changes may be related to the environment of theglacier itself (the actor) and various processes related to the coldand the freeze-thaw cycle. As has been seen in other studies [29,30]freezing appears to have an effect on the microstructure of bone.Fracture morphology appears to be affected by freezing throughmoisture loss [31], and the freeze-thaw cycle may lead toexpansion and contraction of the bone that could have a similareffect [37]. Also, the effects of the freeze-thaw and wet-dry cycleson faunal remains in a periglacial environment have beendiscussed [38]. However, the exact biological processes that areoccurring to enact these changes observed in the bones is unclear.More experimental and observational research could clarify theserelationships.

Fig. 9. Right clavicle (top) and unseriated ribs (below) showing frayed and split bone

margins. Square cut on right clavicle was taken for mtDNA sample.

Please cite this article in press as: M.A. Pilloud, et al., The taphonom(2016), http://dx.doi.org/10.1016/j.forsciint.2016.01.027

2.6. Soft tissue preservation and adipocere formation

Remains recovered from a glacial environment generallyexhibit excellent preservation due to the cold environment. Lowor freezing temperatures stop or retard bacterial growth leading toextensive soft tissue preservation through delayed decomposition[24]. Bones can retain a ‘‘fresh’’ appearance that includes thepresence of bone marrow and retention of a fatty residue;additionally, muscle tissue, ligaments, tendons, and skin may bepreserved (Fig. 10). Soft tissue can also be desiccated (Fig. 11)through the process of sublimation or freeze-drying. This processcan be seen in Arctic and high altitude locations [39]. Finally,adipocere can be present, which is typically indicative of a wetenvironment (Fig. 12).

Elements may present with different levels, or types, ofpreservation within a single site based on their distribution acrossspace or within the glacier. The type of soft tissue preservation canindicate the micro-environment in which the remains werecontained. For example, elements with excellent soft tissuepreservation may have been frozen within the glacier for a longerperiod of time. Whereas desiccated soft tissue may indicateexposure on the glacier under direct sunlight for an extendedperiod. Adipocere formation occurs under wet conditions, and cantherefore indicate if the remains were in melting bodies of water.The findings in this study are consistent with others in glacial

Fig. 11. Mummified left and right feet.

Fig. 10. Preservation of right lower limb to include soft and skeletal tissue.

y of human remains in a glacial environment, Forensic Sci. Int.

Fig. 12. Adipocere on left distal radius with preserved adhering soft tissue. Photo

credit A. Hauer. Square cut is area taken for mtDNA sample.

Fig. 14. Perimortem trauma of ulnar shaft with evidence of postmortem glacial

damage.

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environments that report excellent tissue preservation [5,40,41]and adipocere formation [33].

It is important to note that this delay in decomposition couldextend the time bone retains its ability to fracture in a manner thatis usually designated perimortem due to characteristics of thefracture margins. It is important for the anthropologist analyzinghuman remains to understand taphonomy in a wide range ofenvironments to accurately distinguish peri and postmortem bonealteration. In the case of the Colony Glacier remains, allperimortem fracturing was consistent with a rapid decelerationevent to include multiple comminuted and complete midshaftfractures (Fig. 13). These fractures display characteristics typical ofperimortem fractures to include irregular and smooth margins,

Fig. 13. Representative perimortem trauma at midshaft of long bones.

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which can be distinguished from postmortem damage that canshatter the bone or lead to more regular fragments [42]. Further-more, glacier damage (frayed cortical bone) could be seen onperimortem fractures margins (Fig. 14), further evidence that thesefractures occurred prior to glacial movement.

3. Conclusions

A glacial environment is a unique and dynamic setting, withforces and factors that can leave a characteristic taphonomicsignature on human remains of forensic significance. Glacialtaphonomy is best interpreted with an understanding of glacialmovement (causal agent), glacial load and ice (effectors), and theglacier itself (actor). Using the human remains recovered fromColony Glacier in Alaska, a taphonomic signature of a glacialenvironment has been described, which consists of the followingobservations:

1. Movement of remains away from original area of loss throughglacial movement

2. Dispersal of remains within a confined area due to differentialmovement, exposure, and deposition from the glacier

3. Abrasion of cortical bone focused towards the fractured ends4. Frayed fracture margins on skeletal elements5. Crushed fracture margins on skeletal elements6. Oblique shearing of long bone ends7. Splitting of cortical bone (predominantly observed in ribs and

clavicles)8. Extensive preservation of soft and skeletal tissues9. Adipocere formation

Glacial environments are typically remote; however, as glaciersare retreating worldwide, materials of anthropological interestthat were once enclosed in them may be revealed. This couldinclude archaeological sites, or materials that require the expertiseof a forensic anthropologist, such as previously unrecoveredaircrafts (as illustrated in the case study described here), or otherunidentified individuals. It is therefore important for the anthro-pologist to be familiar with factors that may alter bone in theseenvironments and how these factors will be manifest on theskeletal remains. This work illustrates one example of the effects ofglacial dynamics on remains of forensic significance. More work isneeded, either experimental or observational, to fine tune theseobservations for other glacial environments and to document theireffect on human remains.

y of human remains in a glacial environment, Forensic Sci. Int.

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Acknowledgments

Most importantly, we want to acknowledge the men involved inthis incident and the sacrifice they and their families made for theircountry. Many people at the DPAA-CIL were part of this work, asrecovery efforts and analysis of this scale required the expertise ofmany of our current and former colleagues. Greg Berg, Kelly Esh,MariaTeresa Tersigni-Tarant, Nicholas V. Passalacqua, Alec Chris-tensen, Sean Tallman, Robert Mann, Thomas Sprague, Sabrina Ta’ala,Matt Rhode, Denise To, Owen O’Leary, and Andy Heuer assisted insome way with this project. Gary Haynes gave valuable commentson an earlier draft of this manuscript. Thank you to the CentralIdentification Laboratory at the Defense POW/MIA AccountingAgency for granting permission to publish this work. We also thankthe anonymous reviewers for improving this manuscript.

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