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Home arrow Sites of interest arrow  Al-Khidr arrow Archaeobotany arrow Analysis of phytoliths
First sampling for phytolith analysis (Al-Khidr 2006)

Luc Vrydaghs ( This email address is being protected from spam bots, you need Javascript enabled to view it )


In order to complement the plant macroremains record, a phytolith oriented sampling of Al-Khidr site (Failaka Island, Kuwait) has been conducted in February 2006. This sampling intends to address a) the phytolith potentialities of the site, b) tracking evidences for plant food.

Stone in plants. A brief introduction to the world of phytoliths

Phytoliths are inorganic bodies of plant origin. Their most frequent published chemical compositions are calcium oxalate and opal (among other see Chattaway 1955 and 1956; Pinilla et al. 1997; Piperno 1988; Rovner 1971 and 1983). Calcium oxalates are observed as crystals, while opal phytoliths present a wide array of morphologies. However, aluminium (Sangster et al. 1997; Madella et al 2002) and apatite (Vrydaghs et al. 2000) components have also been reported. The sampling conducted in 2006 was designed to track the opal phytoliths.

Opal phytoliths may appear as mineralizations in the cell lumen, the intercellular space, of the cell wall or in a combination of them ending in a partial mineralization of some tissues. They are reported for Pteridophyts (Piperno 1988), Gymnosperms (Klein and Geist 1978; Sangster et al.. 1997), Mono- and Dicotyledons (Brown 1984; Bozarth 1992; Metcalfe 1960, 1971; Metcalfe and Chalk 1950, 1979 and 1983; Tomlinson 1961; Twiss 1992; Kealhoffer and Piperno 1998; Rovner 1971 and 1983). Phytoliths are observed in different plant organs: leaves (Piperno 1988; Rovner 1971), culm (Blackman 1968), Angiosperm reproductive organs (Piperno 1989), woody tissues (Amos 1952; Balan Menon 1965; IAWA 1989; ter Welle 1976 a & b; Vrydaghs et al. 1995) and roots (Tomlinson 1961). Their morphologies vary with the organ and their tissues under consideration.

After the death of the phytolith bearing plant and the decay of the tissues, the phytoliths are released in the environment and may be transported by hydrochoric, zoochoric or anemochoric agents. After their deposition phytoliths may be degraded and even destroyed under certain conditions, but some of the oldest known specimens date back to the Miocene (Thomassen 1980 a and b, 1983).

Previous research in the Gulf area

While having been successfully applied to several Near Eastern archaeological deposits (i.e. Anderson et al in press, Albert 1999, 2005; Ollendorf, 1987; Rosen 1992, 1993), so far the published phytolith data for the Gulf area are restricted to three sites: Saar (Bahrain; Matthews et al 1997), ed-Durr (Um el-Kawein, U.A.E.) (De Paepe et al 2003; Haerinck et al 1998; Vrydaghs et al 2001; in press) and Kush (Ras al-Khaimah, UAE) (Ishida et al 2003).

At Saar, date palm phytoliths are reported for the inner part of the temple (Matthews et al 1997). The research conducted for ed-Durr includes one bulk sample (Haerinck et al 1998; Vrydaghs et al 20001) and a collection of over 180 thin sections of potsherds (De Paepe et al 2003; Vrydaghs et al in press). Several phytoliths type deriving from the palm tree lignified tissues are identified for the ed-Durr bulk sample (Vrydaghs et al 2001). The origin of the sample (a black lens from the main entrance of a temple) suggests that date palm trunk might have been use during rituals (Haerinck et al 1998; Vrydaghs 2003). As to the analyses of the petrographic thin sections, it contributes to the characterisation of the local and non local production (De Paepe et al 2003) and suggests that the local production exploited several clay sources within the Omani mountains.

The research conducted by Ishida et al at Kush (2003) represents the first major systematic sampling for phytolith analysis for the Gulf. The time period covered ranges from the 4th till the 11th century AD (Sassanian and Islamic periods). The analyses identify barley (Hordeum sp.) and the date palm tree (Phoenix dactyliphera) for a time period extending from the 4th/5th till the 6th century AD. Though these evidences derive from different contexts, the finding of palm phytoliths is related to building structure, more likely roof. Interestingly, the evidences for crop cereals are provided by papillae morphotypes and not by the dendriform ones, their classical markers (illustrations of papillae and dendriforms might be found at http://home.byu.net/tbb/). An increase in grass phytoliths marks the abandonment of the site during the late 8th and 9th centuries AD. Further evidences for phytoliths deriving from barley were recorded for the late 11th century AD and are associated with a change in the composition of the phytolith spectra.

The site of Al-Khidr

Previous archaeobotanical research conducted at Failaka (Willcox 1990) document two periods, the Bronze Age and the Hellenistic Period. Except for few seeds typical for Leguminosae (n=4) and Palmae (n=1), the Bronze Age remains consist mainly of charcoals from shrub species (Tamarix sp. and Ziziphus sp.).         

The Hellenistic record is marked by a co-occurrence of seeds and charcoals. The seed material derives from Graminae (Triticum aestivum; Hordeum cf. distichon and H. nudum) and Leguminosae (Medicago sp., Trifolium sp. and Lens culinaris). However, while Salicaceae charcoals are reported for the Bronze Age, the Hellenistic period is marked by charcoals from Pinaceae (Pinus sp.). Evidences for the palm tree are also reported but in rather small amount for the region.

In general, the charcoal material is poorly preserved. This observation is related to the high salinity of the soils as with most of the sites in the Arabian Gulf Region (Willcox, ibid.).

The phytolith potentialities of Al-Khidr

Approaching the phytolith potentialities of the Al-Khidr site, the published plant reference material, the present-day phytolith record and the archaeological deposits will be considered.

The plant reference

Of the taxa identified by the previous archaeobotanical research (Willcox, ibid.) the Salicaceae, Triticum and Hordeum are known to accumulate regular phytoliths within their tissues (Vrydaghs 2003 vol. 1 and 3). On the other hand, while several Pinaceae, Rhamnaceae and Leguminosae taxa accumulate phytoliths within their leaves, the literature does not provide evidences for regularities comparable to the ones of the previous taxa. Until now, no data are available for the Tamaricaceae (Vrydaghs ibid.).

Several taxa found nowadays on the island are represented in the Dhofar (Oman) collection (Ball 2002; see tab. 1), the only reference available for the Gulf area. According to this reference collection, at the species levels, they is no evidence for distinctive phytoliths for Aizoon canariense (Aizoaceae), Launea mucronata (Asteraceae), Salsola imbricata and Sueda vermiculata (Chenopodiaceae), Fagonia bruguieri, F. indica and Zygophyllum qatarense (Zygophylaceae). Some other taxa exhibit distinctive morphotypes, Cyperus conglomeratus (Cyperaceae), Aeluropus lagopoides, Cenchrus ciliaris and Cynodon dactylon (Poaceae). At the genus level, regularities are proposed for Heliotropium (Boraginaceae) and Convolvulus (Convolvulaceae) and some are suggested for the Asteraceae and Labiatae (Vrydaghs 2003, Vol. 1 and 3).

In the future, a two steps strategy will be developed in order to establish a workable reference collection. At first, taxa not represented in the literature will be collected. Afterwards, according to the results, complementary taxa will be sampled, being either published ones or not.

The present-day record

The purpose of the study of the phytolith modern day record is the elaboration of a referential for the archaeological material. Samples of modern dung and top soils samples have been taken.

Fig. 1: Al-Khidr, Failaka (Kuwait). Location of the archaeological samples taken during the 2006 campaign.
Marshy areas (sabkha) are a striking feature of the Failaka landscape. As so, they deserve peculiar attention. The sampling of some specific spots such as the lowest point of the island completes this first overview. Each time, a list of the botanical species present on the station has been established by M. Hajnalová.

The collected dung material derives from camel, sheep and goat and an unknown species. As camels graze all over the island, the phytolith content of their dung should provides a general overview of the present-day vegetation. Sheep and goats graze around the farms and are fed by imported fodder (cereals and modern fodder from the continent and Saudi Arabia). The relevancy of their dung should be restricted to the farm surroundings.

The archaeological deposits

Four sections have been sampled: in trench 22S, in deep sounding in 22S (22S DS for short), sections in the trenches 24AA and 24W (fig. 1). Sections in 22S DS and 24W present a marine and archaeological member. Solely archaeological deposits composed sections in 22S and 24AA. Sections in 22S DS and 24W have been sampled from the uppermost layers of the marine deposits till the top of the archaeological sequence.

Fig. 2: Al-Khidr, Failaka (Kuwait). Sections 24AA (light grey), 22S (orange), 24W (blue) and deep sounding in 22S (green) and their correlations. The black lines point contacts between the layers while the red lines the possible correlations.
A sandy shelly layer provides a correlation between sections in 24AA, 22S and 22S DS (fig. 2). According to M. Hajnalová, archaeological, archaeozoological and rare archaeobotanical evidences distinguish the sandy layer from 24AA from the one observed in 24W and 22S DS. A loose sandy layer correlates sections 24W and 22S DS (fig. 2). However, it is assumed that these four sections might provide a general overview of the phytolith content of the various deposits.

In order to address a possible post depositional contamination of the deposits by phytoliths deriving from roots, two samples of root remains obtained by flotation have been taken.

Tracking evidences for plant food

The method designed to track the evidences for plant food is similar to the one adopted to establish the phytolith potentialities of the site, i.e. the plant reference collection; sampling of the present-day context and the archaeological deposits.

The reference material

Since several years, it has been established that some of the basic Near Eastern food crops (wheat, barley, date palm) produce distinctive morphologies (Rosen 1992; Hodson et al. 2001; Vrydaghs et Doutrelepont 1997). They might be preserved over a long period of time (Rosen 1993; Ishida 2005). More recent developments propose that some common cereal crops might be discriminate on a quantitative base (Ball et al 1996 and 1999).

Modern material

The purpose of this sampling was to approach the phytolith record of the modern agricultural activities. The collected material is distributed into two categories: present-day activities and sub-recent activities.

Present-days activities

Modern fodder and a dung heap have been collected at the Um al-Dakhan farm. This sampling intends to investigate:

  • if it is possible to distinguish the phytoliths deriving from fodder and local grazing;
  • if phytoliths are altered by passing through the digestive system of the ovi-caprin.

A date palm garden (Al Sabbahiyah) located close to the farm has been sampled according to the in and off site strategy. As previously, the vegetation associated to the palm tree garden has been listed.

Sub-recent activities

The superficial soil of an area known to have been cultivated till the 1950s was also sampled. As control sample, dung from camels was taken.

Archaeological deposits

In order to recover phytoliths evidences from the plant resources, two specific contexts have been approached: in situ storage jars and the adherence of charred organic material to potsherds.

Storage Jars

Two storage jars from trench 23W have been sampled in situ.

Charred remains

At least in three cases (Anderson et al, in press; Mbida et al, 2005 and Thompson and Mulholand, 1994) with one example for the Near East (Anderson et al ibid), phytoliths have been reported in charred material adhering to potsherds. Therefore, part of the Al-Khidr potsherds collection has been screened (see tab. 1), leading to selection of 5 pieces for further analyses in the laboratory.

Complementary archaeological material

Four remains obtained by flotation and preliminarily interpreted as dung have been collected and transmitted for phytolith analysis.

Prospects for forthcoming field works

Although laboratory analyses have not yet started, recommendations for future sampling might already be set up. In case the deposits are devoid of any phytoliths, three questions need to be addressed: the taphonomical processes, the phytolith preservation and the human factor. Each question requires specific sampling. Therefore soundings out of the Al-Khidr site are recommended. If possible, three contexts should be investigated:

  • a) if existing, natural context outside marshy areas;
  • b) natural contexts from marshy areas;
  • c) at least one archaeological sequence from another site covering several cultural periods. If possible, this section should be situated inland.

Soundings a) and b) ought to be under the dominant winds blowing from the Al-Khidr site. This will address the hypothesis of the phytolih content of the dust blow. As marshy areas might serve as natural trap, a section in such context might be of particular importance. Moreover, sounding a) and b) might also help providing geological and pedological data. As to the sounding c), it might contributes to circumvent the responsibility of the human factor in the phytolith deposition as well as addressing the question of the evolution of the conditions favouring the phytolih (and possibly of other plants remains) preservation through time.

See also

Table 1

The present-day vegetation of the Failaka Island (according to Abbadi and El-Sheikh 2002) and the botanical species represented in the Dhofar reference collection (Ball 2002)

FamilyFailaka (after)Dhofar (Oman)
Aizoaceae Aizoon A. canariense Aizoon A. canariense
  Mesembryanthenum M. nodiflorum    
Asteraceae Atractylis A. carduus Atractylis A. kentropylloides
  Filago F. pyramidata    
  Iflogia s I. picata    
  Launaea L. capitata    
  Launaea L. mucronata Launaea L. mucronata
  Launaea L. nudicaulis Launaea L. bornmuleriana
      Launaea L. castanosperma
      Launaea L. intybacia
      Launaea L. massuaensis
  Picris P. babylonica    
  Senecio S. glaucus    
  Sonchus S. oleraceus    
Boraginaceae Anchusa A. hispida    
  Arnebia A. decumbens    
  Arnebia A. linearifolia    
      Cordia C. perottettii
  Heliotropium H. bacciferum    
      Heliotropium H. calcarium
      Heliotropium H. fartakense
      Heliotropium H. longiflorum
  Moltkiopsis M. ciliata    
      Nogalie N. drepanophyullum
      Trichodesma T. africanum
      Trichodesma T. hildebrantia
      Trichodesma T. indica
Caryophylaceae     Cometes C, absinica
  Gypsophila G. capilaris    
  Herniaria H. hemistemon    
  Paronychia P. arabica    
  Polycarpaea P. repens    
  Polycarpaea P. robbairea    
      Polycarpaea P. spicata
  Silene S. arabica    
  Silene S. arenosa    
  Silene S. villosa    
  Spergularia S. diandra    
Chenopodiaceae Anabasis A. setifera    
      Arthrocnemum A. machrostacyum
  Atriplex A. dimorphostegia    
  Atriplex A. leucoclada    
  Bassia B. muricata    
  Bassia B. eriophora    
      Chenopodium C. murale
      Cornulaca C. monacantha
  Halocnemum H. strobilaceum    
  Salsola S. imbricata Salsola S. imbricata
  Seidlitzia S. rosmarinus    
      Sueda S. egyptica
  Suaeda S. vermiculata Sueda S. vermiculata
Cistaceae Helianthenum H. lipii    
Convolvulaceae Convolvulus C. cephalopodus    
  Convolvulus C. oxyphyllus    
  Convolvulus C. pilosellifolius    
      Convolvulus C. prostratus
      Convolvulus C. sinesis
      Convolvulus C. virgatus
  Cressa C. cretica    
      Ipomoea I. obscura
      Ipomoea I. pes-capre
      Seddera I. latifoia
Cruciferae Brassica B. tournefotii    
  Diplotaxis D. harra    
Cyperaceae Cyperus C. arenarius    
  Cyperus C. conglomeratus Cyperus C. conglomeratus
      Cyperus C. irea
      Cyperus C. laevigatus
      Cyperus C. longus
      Schoenoplectus S. litoralis
Euphorbiaceae     Acalypha C. indica
      Andrachne C. aspera
  Andrachne A. telephioides    
      Chrozophera C. oblongifolia
      Croton C. confertus
      Euphorbia E. arabica
      Euphorbia E. balsamifera
      Euphorbia E cactus
      Euphorbia E. grannulata
      Euphorbia E. hadraumatica
      Euphorbia E. hirta
      Euphorbia E. lariea
      Euphorbia E. schimperi
      Jatropha E. dhofarica
      Jatropha E. glandulosa
      Ricinus R. communis
Frankeniaceae Frankenia F. pulverulata    
Geraniaceae Erodium E. bryoniiflium    
  Erodium E. laciniatum    
Poaceae Aeluropus A. lagopoides Aeluropus A. lagopoides
  Brachypodium B. distachum    
  Bromus B. madritensis    
  Cenchrus C. ciliaris Cenchrus C. ciliaris
  Cutandia C. memphitica    
  Cynodon C. dactylon Cynodon C. dactylon
  Hordeum H. murinum    
  Lasiurus L. scindicus    
  Panicum P. turgidum    
  Pennisetum P. divisum    
  Phalaris P. paradoxa    
  Phragmites P.australis    
  Polypogon P. monspeliensis    
  Rostraria (Trisetum) R. cristata    
  Schismus S. barbatus    
  Sphenopus S. divaricatus    
  Sporobolus S. arabicus    
      Sporobolus S. iocladus
      Sporobolus S. virginicus
  Stipa S. capensis    
  Stipagrostis S. ciliata    
  Stipagrostis S. plumosa    
Iridaceae Gynandriris G. sisyrinchium    
Labiatae Salvia S. aegyptiaca    
      Teuchrium T. nummulariflora
      Caesalpinia C. erianthera
      Cassia C. angustifolia
      Delonix D. elata
      Senna S. italica
      Tamarindus T. indica
Leg-Mimosoideae     Acacia A. asak
      Acacia A. ebunea
      Acacia A. nilotica
      Acacia A. senegal
      Acacia A. tortilus
      Prosopis P. judiflora
Leg-Papilionoideae Alhagi A. graecorum    
      Alysicarpus A. vaginalis
      Crotalaria C. retusa
  Hippocrepis H. unisiliquosa    
  Lotus L. halophilus    
  Medicago M. laciniata    
  Trigonella T. stellata    
      Indigofera I. argentae
      Indigofera I. caerium
      Indigofera I. colutea
      Indigofera I. hochstetteri
      Indigofera I. oblongifolia
      Indigofera I. oblongifolium
      Indigofera I. volkensii
      Indigofera I. trita
      Psoralea P. corylifolia
      Sesbania S. sesban
      Tephrosia T. apollinea
    Tephrosia T. quartiniana
    Vatovaea V. pseudolablab
  Astralagus A. annularis    
  Astralagus A. bombycinus    
  Astralagus A. hauarensis    
  Astralagus A. tribuloides    
  Onomis O. serrata    
      Ormocarpon O. dhofarense
Liliaceae Allium A. sindjarense    
      Asparagus A. gracilis
  Asphodelus A. tenuifolius    
      Chlorophytum C. laxum
  Dipcadi D. erythraeum    
Malvaceae     Albemoschus A. esculentus
      Albemoschus A. bidentatum
      Albemoschus A. pannosum
      Gossypium G. herbaceum
  Malva M. parviflora    
      Malvastrum M. coromandelianum
      Senra S. incana
      Sida S. ovata
      Sita S. urens
Plantaginaceae Plantago P. boissieri    
Plumbaginaceae     Dyerophytum D. indicum
      Limonium L. axillare
  Psylliostachys P. spicata    
Polygonaceae Emex E. spinosa    
  Plantago P. coronopus    
  Polygonum P. patulum    
  Rumex R. vesicarius    
Resedaceae     Ochradenas O. baccatus
      Ochridinus O. arabica
  Oligomeris O. linifolia    
  Reseda R. arabica    
      Reseda R. sphenocleiodes
Scrophulariaceae     Bacopa B. monnieri
      Buchnera B. hispida
      Campylanthus C. seddoides
      Campylanthus C. sessiliflorus
      Kickxia K. hastata
      Lindenbergia L. indica
      Lindonbergia L. fruticosa
      Lindenbergia L. muralea
  Scrophularia S. deserti    
      Striga S. angustifolia
      Striga S. gesnerioides
Tamaricaceae Tamarix T. aucheriana Tamarix T. muscatensis
Umbelliferae Ducrosia D. anethifolia    
  Bupleurum B. semicompositum    
Zygophylaceae Fagonia F. bruguieri Fagonia F. brugereii
  Fagonia F. indica Fagonia F. indica
      Fagonia F. socrotrana
  Zygophyllum Z. qatarense Zygophyllum Z. qatarense
      Zygophyllum Z. decumbens
      Zygophyllum Z. robecchii
      Zygophyllum Z. simplex


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Click on a map to see all known archaeological sites on Failaka island from the Bronze Age up to the present day.