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Rice chaff in ceramics from the archaeological site of Sumhuram (Dhofar, Southern Oman)
Journal of Archaeological Science 38 (2011) 1173e1179
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Rice chaff in ceramics from the archaeological site of Sumhuram (Dhofar, Southern Oman) Marta Mariotti Lippi a, *, Tiziana Gonnelli a, Pasquino Pallecchi b a b
Dipartimento di Biologia evoluzionistica - Biologia vegetale, Università di Firenze, Via G. La Pira, 4, 50121 Firenze, Italy Soprintendenza ai Beni Archeologici per la Toscana, Laboratorio di Analisi, L.go del Boschetto 3, 50143, Firenze, Italy
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 March 2010 Received in revised form 15 September 2010 Accepted 23 September 2010
The identification of the chaff used as temper in ancient ceramics represents a possible source of information about the area of origin of the pottery. This paper studies the occurrence of rice (Oryza sp.) chaff in potsherds from the archaeological site of Sumhuram (Dhofar, Sultanate of Oman). The information gathered at the site offers insight into commerce routes and networks to which the town belonged in the first centuries AD. The analysis of the plant material in the pottery and potsherds can also furnish interesting data on the ancient technologies of pottery production. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Chaff Ceramic temper Oryza Pottery Indian Ocean
1. Introduction Ceramic is obtained by firing a mixture of clay, water, and diverse materials intentionally added and collectively named temper. Clay is the main component of pottery making; it always contains a combination of diverse minerals which vary according to the natural deposits from which clay is collected. The intentional addition of temper aims at changing the physical and chemical features of ceramic: among the known changes is the slowing down of the drying process, the reduction of shrinkage and prevention of cracking, the diminished thermal shock in firing. Additives generally used as temper were shells, sand, ashes, dung, and plant parts. Among the latter, cattail fuzz and cereal straw and chaff were the most common (Johnston, 1974; Matson, 1974; Stilborg, 2001; Vincent, 2003; Valamoti, 2005). The mineralogical-petrographic analysis of thin sections of pottery is an important technique in the study of ceramics and represents a fruitful line of research on ancient technology. The identification of the minerals which occurred naturally in the clay deposits (often named “natural temper”) usually helps establish the geographical origin of the pottery and, as a consequence, the interregional trades and cultural interactions. The analysis of temper deliberately added is germane for the identification of the * Corresponding author. Tel.: þ39 055 2757375; fax: þ39 055 2757373. E-mail address: mariotti@unifi.it (M. Mariotti Lippi). 0305-4403/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2010.09.028
area of provenance. Although this type of study is still in the beginning stages, the example of Essouk-Tadmakka in Mali has recently proved the usefulness of such analysis. In the EssoukTadmakka excavation, sponge spicules and Sorghum chaff were found in several pottery sherds (c. 950e1100 AD); this indicates that they were imported from the region of the Niger River (Nixon, 2009). As a general rule, plant materials used as temper are entirely oxidized during firing and leave behind small holes which increase the porosity of the ceramic body. This is an important element which allows for lighter vessels which may have been used to maintain water cool (Matson, 1974). The preservation of plant temper may depend from low firing temperature (Jiang and Liu, 2006) or short firing period; as an example, the presence of pollen grains in potsherds from a ChalcolithiceEarly Historic site of NW India was proven to be the result of quick firing (Ghosh et al., 2006). Mineralogicepetrographic analysis of earthenware from the archaeological site of Sumhuram (Dhofar, Sultanate of Oman) was carried out with the intent of establishing the geographic origin and commercial routes in ancient Dhofar (Southern Oman). During this study, additional plant material was found in some of the thin sections of the objects of study. This paper presents the results of the investigation of such plant material; vegetal temper was identified with the intention of gathering information on the geographic area where the pottery was produced.
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2. Material and methods 2.1. Archaeological site and pottery Sumhuram is a pre-Islamic walled town located along the coasts of Dhofar (Sultanate of Oman), at the estuary of the Wadi Darbat (Khor Rori), about 4 km East from Taqah (Figs. 1 and 2). Five construction phases of the town were identified during the excavations: the first dates back to the 3rd century BC and the last before the site was abandoned in the 5th century AD (Buffa and Sedov, 2008). Sumhuram was an important port in Arabia, involved in the profitable commerce of frankincense (the gum-oleo-resin of Boswellia sacra Flueck.) along the trade routes connecting the Indian and African coasts of the Indian Ocean and extending towards the Mediterranean (Avanzini and Orazi, 2001). These commercial contacts are attested by findings of amphorae from Egypt, terra sigillata and amphorae from Rome, glazed green ceramics and “black and grey” wares probably from India (Office of the Adviser to His Majesty the Sultan for Cultural Affairs, 2008). The ancient town is now an UNESCO World Heritage site on the “Frankincense Trail”. The studied pottery sherds were recovered in different areas of the ancient town: - Area A (called “Residential Quarter”) near the Monumental Building, and particularly Unit 209, which most likely was the collapsed upper floor of Room A85 (IMTO. Sumhuram preliminary report NovembereDecember 2006). - Area B (called “Storage Quarter”) in the SE corner of Sumhuram, near the “Small Gate”, a separate passage to exit the city. - Area F (the “Cult Quarter”) at the NE corner of the city wall, near Building BF3. The first analyzed sherd (signed US 208.7) was recovered in a narrow storage-room named “bin” (A84), which is located near the square A77, in the Area B (Fig. 1). Cement-like plaster showing several layers of renovation covered the entire floor of the storage space; this suggests a prolonged and continuous use. The pottery
sherd was found in a deposit (Unit 208) on the most recent floor. The latter consists of a fine light-brown soil packed with a large quantity of small pebbles and large stones (IMTO. Sumhuram preliminary report NovembereDecember 2006). The sherd was probably part of ceramic kitchenware, such as a pan or bowl, and may be chronologically attributed to the 1st to 4th cent. AD. 2.2. Methodology 2.2.1. Chemical and petrographical analysis The petrographic description of the ceramics was performed using a polarised light microscope Leitz Ortolux POL II on thin sections (30 mm thickness) with an imat image analysis system (Hesp Technology). The morphological and chemical characterization of the inclusions have been performed using an FEI Company Quanta 200 scanning electron microscope coupled with EDS-DX4 with a sUTWþ energy dispersion detector. The acceleration voltage was 25 kV and the filament current 40 mA. 2.2.2. Plant temper analysis In order to identify the plant temper, thin sections were observed under light microscope (l.m.), operating at 200e400; measurements were made on the dark brown remains (see Section 3 below). Reference material was chosen on the basis of general morphology and size of the plant fragments in the sherds. Spikelets of the following cereals were collected from fresh plants and/or exsiccata in the Herbarium Centrale Italicum (FI): Avena sativa L.; Brachiaria ramosa (L.) Stapf; Coix lacryma-jobi L. (male spikelet); Digitaria cruciata (Nees) A. Camus; Echinochloa colona (L.) Link; Hordeum vulgare L.; Oryza sativa L.; Panicum miliaceum L.; Paspalum scrobiculatum L.; Secale cereale L.; Setaria italica (L.) Beauv.; Triticum spp. Further information was collected from literature (Bor, 1960; Arber, 1965; Lazarides, 1980; DeWet, 1981; Hubbard, 1984; Clayton and Renvoize, 1986; Terrell et al., 2001). The spikelets of the reference plants were measured and observed under stereo-microscope with the aim of testing the distinctive features of glumes, lemmas, and paleas: for example the presence or absence of hairs and wings; the number and
Fig. 1. Map showing the location of Sumhuram and the archaeological site.
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Fig. 2. The ancient town of Sumhuram, facing the Wadi Darbat estuary. In the background, the Arabian Sea. Today, a sand barrier separates the estuary from the sea.
distribution of nerves; section outline. Reference fresh material was also sectioned with a cryotome for a more detailed observation under l.m. and comparison with the plant temper of the potsherds. In this paper, the term “chaff” is used to indicate all the components of the cereal spikelet, including the pedicel (the spikelet stalk) but not the caryopsis. Terminology is according to Clayton and Renvoize (1986) and Terrell et al. (2001).
3. Observations The macroscopic appearance of the surface of the ceramic artifacts consists of a reddish matrix with white, earth-like, elongated inclusions which are generally iso-oriented (Fig. 3). Under polarizing microscope the ceramic shows a reddish subisotropic matrix. The temper is characterized by plant material and angular to sub-angular grains of quartz, which locally display ondulose extinction, feldspar, plagioclase, and mica. Small amounts of pirosseno and carbonatic material are also present in the samples. Clasts are, on the average, of small dimensions (granulometric average 80 mm) and predominantly sub-angular in shape.
Fig. 3. Pottery sherd from Sumhuram. Note the white inclusions in the red matrix.
Many dark brown plant fragments were found in ceramic sections (Fig. 4); others, similar in shape, appeared whitish in color (Fig. 5); intermediate inclusions (whitish with small dark parts) were also observed. The whitish fragments are located nearer to the edges than the dark brown ones, suggesting they were more severely affected by oxidation. The relative amount of whitish and dark brown fragments differs in the examined sherds: this suggests different atmospheres (oxidizing or reducing) used in the firing of the ceramic. On the whole, the plant temper still visible forms 12e26% of the total surface. If we consider the holes a result of complete or nearcomplete oxidation, we can hypothesize that the total plant temper could have amounted to 34% of the surface. The shape and size of the plant material varies according to the original features of the plant and the different directions of the cut during the sectioning of the ceramic. The most common were: (1) curved or rarely linear sections of leaf-like structures with one smooth and one wavy surface; the thickness spanned 40e 60 mm in the crests to 20e30 mm in the troughs. Few sections appeared thicker (70e100 mm in the crest) owing to the
Fig. 4. Thin section of the pottery sherd. Note the abundance of plant material.
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Fig. 5. Dark (left) and bright (right) plant material in the sherd. The second one was more severely affected by oxidation during firing.
presence of well-preserved parenchyma cells and smooth epidermal cells. However, for the most part, the thin-walled cells were compressed or oxidized. The distance among the crests was variable averaging about 80 mm. Frequently one of the edges of the section was curled. This kind of material was the most abundant (Fig. 4). (2) linear sections of leaf-like structures, often compressed, with both surfaces smooth. The thickness ranged from 20 to 50 mm (or more in the section with well preserved parenchyma cells); the length was very variable. (3) roughly transversal sections of axes, showing the presence of vascular tissue (Fig. 6). These sections were usually elliptic or asymmetric, with the main axis generally measuring 200e250 mm.
evident mid-nerve, the presence or absence of hairs, the presence or absence of transversal ridges; glumes - the presence or absence of wings, the smooth or rugulose or scabrid surface, the presence or absence of surface hairs on the mid-nerve and at the margin; pedicel and rachilla - the presence or absence of hairs. On the basis of these features, the chaff was attributed to rice (Oryza sp.) of the sect. Oryza, which also has the same dimensional range (Fig. 9). Rice spikelets essentially consists of: (1) a rachilla, usually subglobose; (2) two strongly compressed small structures which are interpreted as sterile lemmas (Arber, 1965; Clayton and Renvoize, 1986) or, alternatively, as glumes (Terrell et al., 2001). In the first
One longitudinally cut radicle germinated from a seed or caryopsis was found in a sample (Fig. 7); dark parallel stripes were also present. The EDS analysis demonstrated the presence of a significant amount of silicon in the plant material (Fig. 8). 4. Plant temper identification The plant temper included in the pottery was identified as cereal chaff which was intentionally added to the clay. The presence of silicon matches the attribution of the temper to Poaceae, which contain a large amount of opaline silica-bodies (phytoliths) in the epidermis (Dayanandan et al., 1983; Clayton and Renvoize, 1986). The comparison between the chaff in the ceramic and the reference material allowed for the exclusion of some alternate attributions. In the context of this study the features which resulted most useful for a correct identification were: lemma - the number, position and prominence of nerves, the smooth or rugulose surface, the presence or absence of an
Fig. 6. Transversal section of an axis (probably rachilla) in the sherd.
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The parallel dark stripes correspond to tangential sections of a lemma or palea which, upon sectioning, only met the ridges. The prevailing occurrence of lemma and palea remains together with the absence of stem or leaf fragments suggests the use of byproducts of the last stage of rice processing. The disarticulation of spikelet of wild rice species is due to the presence of an abscission layer which leaves a smooth abscission scar at the spikelet base, the spikelet being articulated below the glumes (sterile lemmas). In domesticated, nonshattering rice, the spikelets are separated through threshing, which causes an uneven breakage generally at the same level when the rice is mature (Fuller et al., 2009). After threshing, winnowing separates spikelets from by-products, including straw, leaves, and those weed seeds that are lighter than the spikelets. Pounding the spikelets in mortars is the traditional process for dehusking; a second winnowing then permits the removal of the chaff (Harvey and Fuller, 2005). As a consequence, as observed by Harvey and Fuller (2005), the occurrence of only chaff in ceramics indicates that the temper was not made during the early stages of rice processing, but with the final by-product of the entire crop processing, as chaff is the waste from dehusking in a mortar. Fig. 7. Radicle (arrow) in the sherd.
case, glumes are considered to be reduced to two tiny lobes (cf. cupules in Terrell et al., 2001), often obscure, attached to the pedicel tip below the spikelet articulation; (3) the fertile lemma and the palea enclosing the caryopsis (4). The base of the spikelet is enlarged to form the so-called callus. Glumes (or sterile lemmas according to Clayton and Renvoize, 1986) have smooth surfaces. Lemma and palea have identical epidermal morphology: the adaxial surface is smooth, while the abaxial one is characterized by longitudinal ridges and furrows. In the lemma and palea of O. sativa - and closely related species - conspicuous siliceous tubercles are found on the ridges, arranged in vertical tiers and horizontal rows (Terrell et al., 2001). According to this attribution, the sections with one wavy profile correspond to transverse sections of lemma or palea: smooth profiles correspond to the adaxial surface, wavy ones to the abaxial one. The sections which have linear profiles may be considered longitudinal sections of lemmas or paleas, cut in correspondence of the furrows, or sections of the glumes (sterile lemmas according to Clayton and Renvoize,1986). Transverse, oblique and longitudinal sections of the axes also occur, the shape and dimensions determined by the direction of the cut and the original size of the axis. They probably belong to rachillas.
5. Chaff uses and rice cultivation area The use of by-products deriving from plant processing is an interesting topic in ancient and modern economy. Cereal crop processing leaves large amounts of residue which are collectively named straw and chaff (or hull or husk, sometimes fuzz). In arid regions, chaff and straw represented a valuable resource: they were used as fodder particularly when local vegetation was insufficient to support a large number of animals (Van der Veen, 1999). Other uses of chaff were: as primary tempering agent for clay used in building materials (such as mudbricks and plaster), as building component for the upper part of walls and roofs (Van der Veen, 1999; Willcox and Fornite, 1999) or as temper in pottery (Vincent, 2003; Klee et al., 2004; Harvey and Fuller, 2005; Nixon, 2009). Chaff and straw were also a component of dung fuel or used as fuel per se when in bulk (Miller and Smart, 1984; Van der Veen, 1999; Valamoti, 2005); large amounts of dung and chaff were used as fuel for pottery firing (Freed and Freed, 1963). At present, the use of chaff and chopped straw is still widespread in many parts of the world, including the South Arabian Peninsula. The use of plant by-products implies abundance in the territory and, in cases as the one presented here, the diffusion of a specific cereal cultivation. Consequently, its presence in artifacts suggests useful information regarding geographical provenance, particularly when worldwide distribution of that plant is restricted.
Fig. 8. Fracture surface of the sherd observed at Scanning Electron Microscope: note the epidermis of the rice chaff with evident silicised tubercles (left). EDS spectrum indicates the presence of silicon in the plant material (right).
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Fig. 9. Rice chaff in the sherd (lemma or palea), on the left, and in fresh material (lemma), on the right.
Archaeological evidence indicates that rice cultivation was established 5000e3000 years ago in South East Asia and India: it appeared in China around 5000e4000 BC (Zohary and Hopf, 2000; Jiang and Liu, 2006; Fuller et al., 2007; Ruddiman et al., 2008; Zhao, 2010); in India during the third millennium BC (Fuller et al., 2004; Boivin and Fuller, 2009), and in Pakistan in the early second millennium BC (Fuller, 2006). The introduction in Mesopotamia supposedly dates to the late first millennium BC (Sherrat, 1980), probably in Hellenistic times (Zohary and Hopf, 2000); however, the only direct evidence in Western Asia comes from Susa (modern Iran) and dates to the first century AD (Miller, 1981). Regarding the Arabian Peninsula, archaeobotanical data available at present exclude that rice was cultivated at Sumhuram. Rice cultivation is mentioned in Oman only in the Middles Age (Ubaydly, 1993). In his “Travels in Asia and Africa 1325e1354” (Gibb, 1929) Ibn Battuta wrote that the people of Dhofar consumed rice imported from India. Rice has always been a staple commercial product. Desiccated rice grains from the first or second century AD were recovered in waste in Berenike (Egypt) and are considered of probable Indian origin (Wendrich et al., 2003). As for ceramics, charred remains of rice are found in pottery from many archaeological sites. Rice grains, for example, were found in Neolithic pottery of Southern China, dating to about 10.000 BC (Jiang and Liu, 2006); carbonized large-grained rice was found embedded in potsherds at Ban Chiang and Non Nok Tha in Thailand (Smith, 1998); rice husk is present in the pottery of Khok Phanom Di in modern Thailand dating to the second millennium BC (Vincent, 2003), and at Mahagara, a Neolithic site of NorthCentral India (Harvey and Fuller, 2005); ceramics found near Lake Chad (Nigeria) and dating 1500e800 BC were tempered with chaff of domesticated pearl millet and wild rice species (Klee et al., 2004).
Rice and other organic additives were used to produce vessels with thick walls but light in weight (the so-called “light ware” or “spongy ware”). These wares spanned a long production period in India and were the object of trade; they have been found in the archaeological excavation in Berenike, Egypt (Tomber, 2008). In a recent paper, Tomber et al., (2011) suggest Gujarat as source area for rice-tempered black vessels recovered at Quseir (Egypt) and Berenike. 6. Conclusion In addition to standard mineralogicalepetrographical analysis, the identification of plant temper in pottery offers precious information regarding specific areas of origin; this is particularly relevant in cases when the mineral tempers in the ceramic paste are widely diffused and hard to pinpoint to a restricted geographic zone. The use of rice chaff as temper denotes the availability of this by-product in the area of pottery production and, as a consequence, the practice of rice cultivation. Tomber (2008) and Tomber et al., (2011) indicated India as the possible area of origin of this type of ceramic. In the pottery from Sumhuram, the mineralogical composition of the natural temper excludes the possibility that the provenance of the raw material used in the preparation of the ceramic matrix were from the local calcareous soils (Ministry of Petroleum and Minerals, 1993; 1998). The rice chaff finding represents proof of the involvement of this town in the Indian-Arabic trade, within the context of the larger IndianeRoman commerce. This trade must have lasted a long time, given that ceramics with rice chaff were found in several deposits throughout Sumhuram, probably dating to different phases of the city life (Sedov, 2008; IMTO. Sumhuram preliminary report November-December 2006).
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The use of organic additives is the result of age-long traditions and economic pressures and can provide archaeologists with useful insights into the ancient technologies of pottery production. In this case, mineral temper belonged to the skeleton of the natural sediment used for the clay paste. The presence of large amounts of skeleton, ranging from 48 to 65%, gives limited plasticity which is improved by the intentional addition of an essentially fibrous component, i.e. the rice chaff. Acknowledgements The authors wish to thank the Adviser for Cultural Affairs, Sultanate of Oman, for the logistic assistance during the visit to Dhofar and the opportunity of studying the archaeological material. They also thank the anonymous referees for their help in improving the text. This research was carried out with financial aid of MURST (PRIN 2007R95LT4). References Arber, A., 1965. The Gramineae. A Study of Cereal, Bamboo, and Grass. Cramer and Weinheim, New York. Avanzini, A., Orazi, R., 2001. The construction phases of Khor Rori’s monumental gate. Arabian Archaeology and Epigraphy 12, 249e259. Boivin, N., Fuller, D.Q., 2009. Shell, middens, ships and seeds: exploring coastal subsistence, maritime trade and the dispersal of domesticates in and around the ancient Arabian Peninsula. Journal of World Prehistory 22, 113e180. Bor, N.L., 1960. The Grasses of Burma, Ceylon, India and Pakistan. Pergamon Press, Oxford. Buffa, V., Sedov, A.V., 2008. The residential quarter: area A. In: Avanzini, A. (Ed.), Khor Rori Report 2. Arabia Antica 5, Archaeological Studies. «L’Erma» di Bretschneider, Roma, pp. 15e59. Clayton, W.D., Renvoize, S.A., 1986. Genera Graminum. Grasses of the World. In: Kew Bulletin Additional series XIII. Royal Botanic Gardens, Kew. Dayanandan, P., Kaufman, P.B., Franklin, C.I., 1983. Detection of silica in plants. American Journal of Botany 70, 1079e1084. DeWet, J.M.J., 1981. Grasses and the culture history of man. Annals of the Missouri Botanical Garden 68, 87e104. Freed, R.S., Freed, S.A., 1963. Utilitarian pottery manufacture in North Indian village. Anthropological Quarterly 36, 34e42. Fuller, D.Q., 2006. Agricultural origins and frontiers in South Asia: a working synthesis. Journal of World Prehistory 20, 1e86. Fuller, D., Korisettar, R., Venkatasubbaiah, P.C., Jones, M.K., 2004. Early plant domestications in southern India: some preliminary archaeobotanical results. Vegetation History and Archaeobotany 13, 115e129. Fuller, D.Q., Harvey, E., Qin, L., 2007. Presumed domestication? Evidence for wild rice cultivation and domestication in the fifth millennium BC of the Lower Yangtze region. Antiquity 81, 316e331. Fuller, D.Q., Qin, L., Zheng, Y., Zhao, Z., Chen, X., Hosoya, L.A., Sun, G.-P., 2009. The domestication process and domestication rate in rice: spikelet bases from the Lower Yangtze. Science 323, 1607e1610. Ghosh, R., D’Rozario, A., Bera, S., 2006. Can palynomorphs occur in burnt ancient potsherds? An experimental proof. Journal of Archaeological Science 33, 1445e1451. Gibb, H.A.R. (Ed.), 1929. Ibn Battuta, Travels in Asia and Africa 1325e1354. http:// www.fordham.edu/halsall/source/1354-ibnbattuta.html. Harvey, E.L., Fuller, D.Q., 2005. Investigating crop processing using phytolith analysis: the example of rice and millets. Journal of Archaeological Science 32, 739e752. Hubbard, C.E., 1984. In: Hubbard, J.C.E. (Ed.), Grasses. A Guide to Their Structure, Identification, Uses and Distribution in the British Isles, third ed. Penguin books, Harmondsworth.
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Rice chaff in ceramics from the archaeological site of Sumhuram (Dhofar, Southern Oman) Marta Mariotti Lippi a, *, Tiziana Gonnelli a, Pasquino Pallecchi b a b
Dipartimento di Biologia evoluzionistica - Biologia vegetale, Università di Firenze, Via G. La Pira, 4, 50121 Firenze, Italy Soprintendenza ai Beni Archeologici per la Toscana, Laboratorio di Analisi, L.go del Boschetto 3, 50143, Firenze, Italy
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 March 2010 Received in revised form 15 September 2010 Accepted 23 September 2010
The identification of the chaff used as temper in ancient ceramics represents a possible source of information about the area of origin of the pottery. This paper studies the occurrence of rice (Oryza sp.) chaff in potsherds from the archaeological site of Sumhuram (Dhofar, Sultanate of Oman). The information gathered at the site offers insight into commerce routes and networks to which the town belonged in the first centuries AD. The analysis of the plant material in the pottery and potsherds can also furnish interesting data on the ancient technologies of pottery production. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Chaff Ceramic temper Oryza Pottery Indian Ocean
1. Introduction Ceramic is obtained by firing a mixture of clay, water, and diverse materials intentionally added and collectively named temper. Clay is the main component of pottery making; it always contains a combination of diverse minerals which vary according to the natural deposits from which clay is collected. The intentional addition of temper aims at changing the physical and chemical features of ceramic: among the known changes is the slowing down of the drying process, the reduction of shrinkage and prevention of cracking, the diminished thermal shock in firing. Additives generally used as temper were shells, sand, ashes, dung, and plant parts. Among the latter, cattail fuzz and cereal straw and chaff were the most common (Johnston, 1974; Matson, 1974; Stilborg, 2001; Vincent, 2003; Valamoti, 2005). The mineralogical-petrographic analysis of thin sections of pottery is an important technique in the study of ceramics and represents a fruitful line of research on ancient technology. The identification of the minerals which occurred naturally in the clay deposits (often named “natural temper”) usually helps establish the geographical origin of the pottery and, as a consequence, the interregional trades and cultural interactions. The analysis of temper deliberately added is germane for the identification of the * Corresponding author. Tel.: þ39 055 2757375; fax: þ39 055 2757373. E-mail address: mariotti@unifi.it (M. Mariotti Lippi). 0305-4403/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2010.09.028
area of provenance. Although this type of study is still in the beginning stages, the example of Essouk-Tadmakka in Mali has recently proved the usefulness of such analysis. In the EssoukTadmakka excavation, sponge spicules and Sorghum chaff were found in several pottery sherds (c. 950e1100 AD); this indicates that they were imported from the region of the Niger River (Nixon, 2009). As a general rule, plant materials used as temper are entirely oxidized during firing and leave behind small holes which increase the porosity of the ceramic body. This is an important element which allows for lighter vessels which may have been used to maintain water cool (Matson, 1974). The preservation of plant temper may depend from low firing temperature (Jiang and Liu, 2006) or short firing period; as an example, the presence of pollen grains in potsherds from a ChalcolithiceEarly Historic site of NW India was proven to be the result of quick firing (Ghosh et al., 2006). Mineralogicepetrographic analysis of earthenware from the archaeological site of Sumhuram (Dhofar, Sultanate of Oman) was carried out with the intent of establishing the geographic origin and commercial routes in ancient Dhofar (Southern Oman). During this study, additional plant material was found in some of the thin sections of the objects of study. This paper presents the results of the investigation of such plant material; vegetal temper was identified with the intention of gathering information on the geographic area where the pottery was produced.
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2. Material and methods 2.1. Archaeological site and pottery Sumhuram is a pre-Islamic walled town located along the coasts of Dhofar (Sultanate of Oman), at the estuary of the Wadi Darbat (Khor Rori), about 4 km East from Taqah (Figs. 1 and 2). Five construction phases of the town were identified during the excavations: the first dates back to the 3rd century BC and the last before the site was abandoned in the 5th century AD (Buffa and Sedov, 2008). Sumhuram was an important port in Arabia, involved in the profitable commerce of frankincense (the gum-oleo-resin of Boswellia sacra Flueck.) along the trade routes connecting the Indian and African coasts of the Indian Ocean and extending towards the Mediterranean (Avanzini and Orazi, 2001). These commercial contacts are attested by findings of amphorae from Egypt, terra sigillata and amphorae from Rome, glazed green ceramics and “black and grey” wares probably from India (Office of the Adviser to His Majesty the Sultan for Cultural Affairs, 2008). The ancient town is now an UNESCO World Heritage site on the “Frankincense Trail”. The studied pottery sherds were recovered in different areas of the ancient town: - Area A (called “Residential Quarter”) near the Monumental Building, and particularly Unit 209, which most likely was the collapsed upper floor of Room A85 (IMTO. Sumhuram preliminary report NovembereDecember 2006). - Area B (called “Storage Quarter”) in the SE corner of Sumhuram, near the “Small Gate”, a separate passage to exit the city. - Area F (the “Cult Quarter”) at the NE corner of the city wall, near Building BF3. The first analyzed sherd (signed US 208.7) was recovered in a narrow storage-room named “bin” (A84), which is located near the square A77, in the Area B (Fig. 1). Cement-like plaster showing several layers of renovation covered the entire floor of the storage space; this suggests a prolonged and continuous use. The pottery
sherd was found in a deposit (Unit 208) on the most recent floor. The latter consists of a fine light-brown soil packed with a large quantity of small pebbles and large stones (IMTO. Sumhuram preliminary report NovembereDecember 2006). The sherd was probably part of ceramic kitchenware, such as a pan or bowl, and may be chronologically attributed to the 1st to 4th cent. AD. 2.2. Methodology 2.2.1. Chemical and petrographical analysis The petrographic description of the ceramics was performed using a polarised light microscope Leitz Ortolux POL II on thin sections (30 mm thickness) with an imat image analysis system (Hesp Technology). The morphological and chemical characterization of the inclusions have been performed using an FEI Company Quanta 200 scanning electron microscope coupled with EDS-DX4 with a sUTWþ energy dispersion detector. The acceleration voltage was 25 kV and the filament current 40 mA. 2.2.2. Plant temper analysis In order to identify the plant temper, thin sections were observed under light microscope (l.m.), operating at 200e400; measurements were made on the dark brown remains (see Section 3 below). Reference material was chosen on the basis of general morphology and size of the plant fragments in the sherds. Spikelets of the following cereals were collected from fresh plants and/or exsiccata in the Herbarium Centrale Italicum (FI): Avena sativa L.; Brachiaria ramosa (L.) Stapf; Coix lacryma-jobi L. (male spikelet); Digitaria cruciata (Nees) A. Camus; Echinochloa colona (L.) Link; Hordeum vulgare L.; Oryza sativa L.; Panicum miliaceum L.; Paspalum scrobiculatum L.; Secale cereale L.; Setaria italica (L.) Beauv.; Triticum spp. Further information was collected from literature (Bor, 1960; Arber, 1965; Lazarides, 1980; DeWet, 1981; Hubbard, 1984; Clayton and Renvoize, 1986; Terrell et al., 2001). The spikelets of the reference plants were measured and observed under stereo-microscope with the aim of testing the distinctive features of glumes, lemmas, and paleas: for example the presence or absence of hairs and wings; the number and
Fig. 1. Map showing the location of Sumhuram and the archaeological site.
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Fig. 2. The ancient town of Sumhuram, facing the Wadi Darbat estuary. In the background, the Arabian Sea. Today, a sand barrier separates the estuary from the sea.
distribution of nerves; section outline. Reference fresh material was also sectioned with a cryotome for a more detailed observation under l.m. and comparison with the plant temper of the potsherds. In this paper, the term “chaff” is used to indicate all the components of the cereal spikelet, including the pedicel (the spikelet stalk) but not the caryopsis. Terminology is according to Clayton and Renvoize (1986) and Terrell et al. (2001).
3. Observations The macroscopic appearance of the surface of the ceramic artifacts consists of a reddish matrix with white, earth-like, elongated inclusions which are generally iso-oriented (Fig. 3). Under polarizing microscope the ceramic shows a reddish subisotropic matrix. The temper is characterized by plant material and angular to sub-angular grains of quartz, which locally display ondulose extinction, feldspar, plagioclase, and mica. Small amounts of pirosseno and carbonatic material are also present in the samples. Clasts are, on the average, of small dimensions (granulometric average 80 mm) and predominantly sub-angular in shape.
Fig. 3. Pottery sherd from Sumhuram. Note the white inclusions in the red matrix.
Many dark brown plant fragments were found in ceramic sections (Fig. 4); others, similar in shape, appeared whitish in color (Fig. 5); intermediate inclusions (whitish with small dark parts) were also observed. The whitish fragments are located nearer to the edges than the dark brown ones, suggesting they were more severely affected by oxidation. The relative amount of whitish and dark brown fragments differs in the examined sherds: this suggests different atmospheres (oxidizing or reducing) used in the firing of the ceramic. On the whole, the plant temper still visible forms 12e26% of the total surface. If we consider the holes a result of complete or nearcomplete oxidation, we can hypothesize that the total plant temper could have amounted to 34% of the surface. The shape and size of the plant material varies according to the original features of the plant and the different directions of the cut during the sectioning of the ceramic. The most common were: (1) curved or rarely linear sections of leaf-like structures with one smooth and one wavy surface; the thickness spanned 40e 60 mm in the crests to 20e30 mm in the troughs. Few sections appeared thicker (70e100 mm in the crest) owing to the
Fig. 4. Thin section of the pottery sherd. Note the abundance of plant material.
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Fig. 5. Dark (left) and bright (right) plant material in the sherd. The second one was more severely affected by oxidation during firing.
presence of well-preserved parenchyma cells and smooth epidermal cells. However, for the most part, the thin-walled cells were compressed or oxidized. The distance among the crests was variable averaging about 80 mm. Frequently one of the edges of the section was curled. This kind of material was the most abundant (Fig. 4). (2) linear sections of leaf-like structures, often compressed, with both surfaces smooth. The thickness ranged from 20 to 50 mm (or more in the section with well preserved parenchyma cells); the length was very variable. (3) roughly transversal sections of axes, showing the presence of vascular tissue (Fig. 6). These sections were usually elliptic or asymmetric, with the main axis generally measuring 200e250 mm.
evident mid-nerve, the presence or absence of hairs, the presence or absence of transversal ridges; glumes - the presence or absence of wings, the smooth or rugulose or scabrid surface, the presence or absence of surface hairs on the mid-nerve and at the margin; pedicel and rachilla - the presence or absence of hairs. On the basis of these features, the chaff was attributed to rice (Oryza sp.) of the sect. Oryza, which also has the same dimensional range (Fig. 9). Rice spikelets essentially consists of: (1) a rachilla, usually subglobose; (2) two strongly compressed small structures which are interpreted as sterile lemmas (Arber, 1965; Clayton and Renvoize, 1986) or, alternatively, as glumes (Terrell et al., 2001). In the first
One longitudinally cut radicle germinated from a seed or caryopsis was found in a sample (Fig. 7); dark parallel stripes were also present. The EDS analysis demonstrated the presence of a significant amount of silicon in the plant material (Fig. 8). 4. Plant temper identification The plant temper included in the pottery was identified as cereal chaff which was intentionally added to the clay. The presence of silicon matches the attribution of the temper to Poaceae, which contain a large amount of opaline silica-bodies (phytoliths) in the epidermis (Dayanandan et al., 1983; Clayton and Renvoize, 1986). The comparison between the chaff in the ceramic and the reference material allowed for the exclusion of some alternate attributions. In the context of this study the features which resulted most useful for a correct identification were: lemma - the number, position and prominence of nerves, the smooth or rugulose surface, the presence or absence of an
Fig. 6. Transversal section of an axis (probably rachilla) in the sherd.
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The parallel dark stripes correspond to tangential sections of a lemma or palea which, upon sectioning, only met the ridges. The prevailing occurrence of lemma and palea remains together with the absence of stem or leaf fragments suggests the use of byproducts of the last stage of rice processing. The disarticulation of spikelet of wild rice species is due to the presence of an abscission layer which leaves a smooth abscission scar at the spikelet base, the spikelet being articulated below the glumes (sterile lemmas). In domesticated, nonshattering rice, the spikelets are separated through threshing, which causes an uneven breakage generally at the same level when the rice is mature (Fuller et al., 2009). After threshing, winnowing separates spikelets from by-products, including straw, leaves, and those weed seeds that are lighter than the spikelets. Pounding the spikelets in mortars is the traditional process for dehusking; a second winnowing then permits the removal of the chaff (Harvey and Fuller, 2005). As a consequence, as observed by Harvey and Fuller (2005), the occurrence of only chaff in ceramics indicates that the temper was not made during the early stages of rice processing, but with the final by-product of the entire crop processing, as chaff is the waste from dehusking in a mortar. Fig. 7. Radicle (arrow) in the sherd.
case, glumes are considered to be reduced to two tiny lobes (cf. cupules in Terrell et al., 2001), often obscure, attached to the pedicel tip below the spikelet articulation; (3) the fertile lemma and the palea enclosing the caryopsis (4). The base of the spikelet is enlarged to form the so-called callus. Glumes (or sterile lemmas according to Clayton and Renvoize, 1986) have smooth surfaces. Lemma and palea have identical epidermal morphology: the adaxial surface is smooth, while the abaxial one is characterized by longitudinal ridges and furrows. In the lemma and palea of O. sativa - and closely related species - conspicuous siliceous tubercles are found on the ridges, arranged in vertical tiers and horizontal rows (Terrell et al., 2001). According to this attribution, the sections with one wavy profile correspond to transverse sections of lemma or palea: smooth profiles correspond to the adaxial surface, wavy ones to the abaxial one. The sections which have linear profiles may be considered longitudinal sections of lemmas or paleas, cut in correspondence of the furrows, or sections of the glumes (sterile lemmas according to Clayton and Renvoize,1986). Transverse, oblique and longitudinal sections of the axes also occur, the shape and dimensions determined by the direction of the cut and the original size of the axis. They probably belong to rachillas.
5. Chaff uses and rice cultivation area The use of by-products deriving from plant processing is an interesting topic in ancient and modern economy. Cereal crop processing leaves large amounts of residue which are collectively named straw and chaff (or hull or husk, sometimes fuzz). In arid regions, chaff and straw represented a valuable resource: they were used as fodder particularly when local vegetation was insufficient to support a large number of animals (Van der Veen, 1999). Other uses of chaff were: as primary tempering agent for clay used in building materials (such as mudbricks and plaster), as building component for the upper part of walls and roofs (Van der Veen, 1999; Willcox and Fornite, 1999) or as temper in pottery (Vincent, 2003; Klee et al., 2004; Harvey and Fuller, 2005; Nixon, 2009). Chaff and straw were also a component of dung fuel or used as fuel per se when in bulk (Miller and Smart, 1984; Van der Veen, 1999; Valamoti, 2005); large amounts of dung and chaff were used as fuel for pottery firing (Freed and Freed, 1963). At present, the use of chaff and chopped straw is still widespread in many parts of the world, including the South Arabian Peninsula. The use of plant by-products implies abundance in the territory and, in cases as the one presented here, the diffusion of a specific cereal cultivation. Consequently, its presence in artifacts suggests useful information regarding geographical provenance, particularly when worldwide distribution of that plant is restricted.
Fig. 8. Fracture surface of the sherd observed at Scanning Electron Microscope: note the epidermis of the rice chaff with evident silicised tubercles (left). EDS spectrum indicates the presence of silicon in the plant material (right).
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Fig. 9. Rice chaff in the sherd (lemma or palea), on the left, and in fresh material (lemma), on the right.
Archaeological evidence indicates that rice cultivation was established 5000e3000 years ago in South East Asia and India: it appeared in China around 5000e4000 BC (Zohary and Hopf, 2000; Jiang and Liu, 2006; Fuller et al., 2007; Ruddiman et al., 2008; Zhao, 2010); in India during the third millennium BC (Fuller et al., 2004; Boivin and Fuller, 2009), and in Pakistan in the early second millennium BC (Fuller, 2006). The introduction in Mesopotamia supposedly dates to the late first millennium BC (Sherrat, 1980), probably in Hellenistic times (Zohary and Hopf, 2000); however, the only direct evidence in Western Asia comes from Susa (modern Iran) and dates to the first century AD (Miller, 1981). Regarding the Arabian Peninsula, archaeobotanical data available at present exclude that rice was cultivated at Sumhuram. Rice cultivation is mentioned in Oman only in the Middles Age (Ubaydly, 1993). In his “Travels in Asia and Africa 1325e1354” (Gibb, 1929) Ibn Battuta wrote that the people of Dhofar consumed rice imported from India. Rice has always been a staple commercial product. Desiccated rice grains from the first or second century AD were recovered in waste in Berenike (Egypt) and are considered of probable Indian origin (Wendrich et al., 2003). As for ceramics, charred remains of rice are found in pottery from many archaeological sites. Rice grains, for example, were found in Neolithic pottery of Southern China, dating to about 10.000 BC (Jiang and Liu, 2006); carbonized large-grained rice was found embedded in potsherds at Ban Chiang and Non Nok Tha in Thailand (Smith, 1998); rice husk is present in the pottery of Khok Phanom Di in modern Thailand dating to the second millennium BC (Vincent, 2003), and at Mahagara, a Neolithic site of NorthCentral India (Harvey and Fuller, 2005); ceramics found near Lake Chad (Nigeria) and dating 1500e800 BC were tempered with chaff of domesticated pearl millet and wild rice species (Klee et al., 2004).
Rice and other organic additives were used to produce vessels with thick walls but light in weight (the so-called “light ware” or “spongy ware”). These wares spanned a long production period in India and were the object of trade; they have been found in the archaeological excavation in Berenike, Egypt (Tomber, 2008). In a recent paper, Tomber et al., (2011) suggest Gujarat as source area for rice-tempered black vessels recovered at Quseir (Egypt) and Berenike. 6. Conclusion In addition to standard mineralogicalepetrographical analysis, the identification of plant temper in pottery offers precious information regarding specific areas of origin; this is particularly relevant in cases when the mineral tempers in the ceramic paste are widely diffused and hard to pinpoint to a restricted geographic zone. The use of rice chaff as temper denotes the availability of this by-product in the area of pottery production and, as a consequence, the practice of rice cultivation. Tomber (2008) and Tomber et al., (2011) indicated India as the possible area of origin of this type of ceramic. In the pottery from Sumhuram, the mineralogical composition of the natural temper excludes the possibility that the provenance of the raw material used in the preparation of the ceramic matrix were from the local calcareous soils (Ministry of Petroleum and Minerals, 1993; 1998). The rice chaff finding represents proof of the involvement of this town in the Indian-Arabic trade, within the context of the larger IndianeRoman commerce. This trade must have lasted a long time, given that ceramics with rice chaff were found in several deposits throughout Sumhuram, probably dating to different phases of the city life (Sedov, 2008; IMTO. Sumhuram preliminary report November-December 2006).
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The use of organic additives is the result of age-long traditions and economic pressures and can provide archaeologists with useful insights into the ancient technologies of pottery production. In this case, mineral temper belonged to the skeleton of the natural sediment used for the clay paste. The presence of large amounts of skeleton, ranging from 48 to 65%, gives limited plasticity which is improved by the intentional addition of an essentially fibrous component, i.e. the rice chaff. Acknowledgements The authors wish to thank the Adviser for Cultural Affairs, Sultanate of Oman, for the logistic assistance during the visit to Dhofar and the opportunity of studying the archaeological material. They also thank the anonymous referees for their help in improving the text. This research was carried out with financial aid of MURST (PRIN 2007R95LT4). References Arber, A., 1965. The Gramineae. A Study of Cereal, Bamboo, and Grass. Cramer and Weinheim, New York. Avanzini, A., Orazi, R., 2001. The construction phases of Khor Rori’s monumental gate. Arabian Archaeology and Epigraphy 12, 249e259. Boivin, N., Fuller, D.Q., 2009. Shell, middens, ships and seeds: exploring coastal subsistence, maritime trade and the dispersal of domesticates in and around the ancient Arabian Peninsula. Journal of World Prehistory 22, 113e180. Bor, N.L., 1960. The Grasses of Burma, Ceylon, India and Pakistan. Pergamon Press, Oxford. Buffa, V., Sedov, A.V., 2008. The residential quarter: area A. In: Avanzini, A. (Ed.), Khor Rori Report 2. Arabia Antica 5, Archaeological Studies. «L’Erma» di Bretschneider, Roma, pp. 15e59. Clayton, W.D., Renvoize, S.A., 1986. Genera Graminum. Grasses of the World. In: Kew Bulletin Additional series XIII. Royal Botanic Gardens, Kew. Dayanandan, P., Kaufman, P.B., Franklin, C.I., 1983. Detection of silica in plants. American Journal of Botany 70, 1079e1084. DeWet, J.M.J., 1981. Grasses and the culture history of man. Annals of the Missouri Botanical Garden 68, 87e104. Freed, R.S., Freed, S.A., 1963. Utilitarian pottery manufacture in North Indian village. Anthropological Quarterly 36, 34e42. Fuller, D.Q., 2006. Agricultural origins and frontiers in South Asia: a working synthesis. Journal of World Prehistory 20, 1e86. Fuller, D., Korisettar, R., Venkatasubbaiah, P.C., Jones, M.K., 2004. Early plant domestications in southern India: some preliminary archaeobotanical results. Vegetation History and Archaeobotany 13, 115e129. Fuller, D.Q., Harvey, E., Qin, L., 2007. Presumed domestication? Evidence for wild rice cultivation and domestication in the fifth millennium BC of the Lower Yangtze region. Antiquity 81, 316e331. Fuller, D.Q., Qin, L., Zheng, Y., Zhao, Z., Chen, X., Hosoya, L.A., Sun, G.-P., 2009. The domestication process and domestication rate in rice: spikelet bases from the Lower Yangtze. Science 323, 1607e1610. Ghosh, R., D’Rozario, A., Bera, S., 2006. Can palynomorphs occur in burnt ancient potsherds? An experimental proof. Journal of Archaeological Science 33, 1445e1451. Gibb, H.A.R. (Ed.), 1929. Ibn Battuta, Travels in Asia and Africa 1325e1354. http:// www.fordham.edu/halsall/source/1354-ibnbattuta.html. Harvey, E.L., Fuller, D.Q., 2005. Investigating crop processing using phytolith analysis: the example of rice and millets. Journal of Archaeological Science 32, 739e752. Hubbard, C.E., 1984. In: Hubbard, J.C.E. (Ed.), Grasses. A Guide to Their Structure, Identification, Uses and Distribution in the British Isles, third ed. Penguin books, Harmondsworth.
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