INTRODUCTION
Early Archaeological Research in Eastern Nigeria
In southeastern Nigeria, Donald Hartle played a significant, pioneering role in archaeological research. His main focus was on habitation sites and phases of human occupations in caves and rock shelters, specifically in the Nsukka and Afikpo area, which constitute parts of northern Igboland (Hartle Reference Hartle1966, Reference Hartle1967; Andah and Anozie Reference Andah and Anozie1980; Chikwendu Reference Chikwendu1998). At the time, human occupation and cultural developments in Igboland, based on the archaeological excavations of a University of Nigeria, Nsukka farm site by Hartle (a parcel of land donated for agricultural activities), were dated to 2555 ± 130 BP. Pottery recovered from the ceramic phase in the Afikpo cave sites dated to about 2500 BP. This farm site dated is one of the early settlement areas in Nsukka with evidence of crude and thick pottery featuring seed impressions, which indicated human activities there as from about 3000 BP. The occurrence of pottery was used as a distinction between aceramic and ceramic phases in Afikpo. This distinction was interpreted as indicative of a transition from hunting and gathering to food production.
In northern Igboland, Anozie (Reference Anozie1979, Reference Anozie1985) noted variants of extinct smelting activities, which gave rise to different slag types observed in Opi, Lejja, Umundu in the Nsukka area and Nwofe community in Abakiliki, Ebonyi State. Pit or bowl furnace types, believed to be the earliest forms of furnaces, were recovered in the area. Anozie (Reference Anozie1985) is of the view that the Lejja iron smelters, in addition to the pit or bowl furnaces, made use of other furnace types and perhaps variants of shaft furnaces. This was indicated by different types of slag aggregates including flow slag present there. Okafor (Reference Okafor, Shaw, Sinclair, Andah and Okpoko1993), based on the analysis of slag residues, questioned the existence of pit or bowl furnaces in the Nsukka region. He believed that the blocks of slag were formed in slag pits by slag tapping from draught shaft furnace. This position posed some fundamental questions. For instance, how do we account for the very heavy weight of the cylindrical slags when compared with other slag aggregates from slag tapping of shaft furnaces in the Nsukka area? Besides, there are observable original iron ores in and around some of the slag blocks (Okpoko and Ibeanu Reference Okpoko, Ibeanu and Okpoko1999). Shaft furnaces would be expected to produce or/and smelt better than pit/bowl furnace as noted in the Nsukka area. Be that as it may, the radiocarbon (14C) dates from Okafor’s research have phased iron smelting technology into three developmental stages, viz early, middle and late stage. The Opi and Lejja iron smelting sites were regarded as early phases based on their furnace type as indicated by cylindrical slag deposit with early radiocarbon dates of 520–200 BC (Okafor and Patricia Reference Okafor and Patricia1992; Okafor Reference Okafor, Shaw, Sinclair, Andah and Okpoko1993). However, a very earlier date of 2000 BP was obtained from the Lejja iron smelting site (Eze-Uzomaka Reference Eze-Uzomaka2013). The middle and later phases are dated to cal AD 895–AD 1020 and AD 810–AD 1430 and cal AD 1430–AD 1950, respectively. These findings notwithstanding, an aspect of the ecological anthropology of the area that requires attention is in the paleoenvironmental conditions under which these human occupations occurred and the possible plants that constituted the food resources exploited during the early and later occupation of the study area. To achieve these objectives, sediment samples for palynological analyses were collected from two cave sites, Onualor and Ozizza, while iron slag, obtained from the excavations of Eziamaugwu, an iron-smelting site, was subjected to geoarchaeological analyses.
Here we document archaeological investigations of Ojebe-Ogene in Nsukka area in northern Igboland. The sites consist of (i) an iron smelting and (ii) caves sites located in the Ukehe community. In the study area, the Ukehe community was selected for excavation because of the copious evidence of iron smelting activities in the past. In addition, we present results of palynological studies of the deposit of bat guano after our discovery of the Onualor cave. The two sites we believed could enhance our understanding of aspects of our research objective(s), bordering on the sequence of smelting technology compared with dated smelting sites in Nsukka. In addition, at Ozizza cave on the southern edge of the cuesta, the research was geared towards enhancing our understanding of the sequence of human occupation when compared with other cave sites on the cuesta. It was expected that the deposits from the two caves (Onualor and Ozizza) would throw more light on both the paleoenvironmental and possibly the human–landscape interactions in the study area.
Description of the Study Sites
The study areas (iron smelting site and Onualor cave) are located in Ukehe, and Ozizza in Enugu and Ebonyi state (Figure 1). These areas of study are situated in Nsukka-Okigwe-Afikpo trending cuesta (Figure 2). Onuolar Cave, one of the three study locations, is located in the Ukehe community, and is along Nsukka-Okigwe to Afikpo road; the area is characterized by several rock shelters and caves. Onualor cave contains a huge deposit of bat guano of about 1.5 m thick, which formed the basis of the palynological investigation there (Figure 2). The other study sites are an iron smelting site, and Ozizza cave all located in Ukehe Igbo-Etiti Local Government Area and Afikpo in Ebonyi state, southeast Nigeria. The Onualor cave and Eziamugwu iron smelting sites have satellite locations of 60º39'02.2"N, 70º75.27'08.2", elevation 308 m and 60º38'32.4"N, 70º24'39.2"E, elevation 497 m, respectively, while Ozizza is situated at satellite location 5º54'42"N, 7º57'19"E (Figure 1). These study areas are situated in Nsukka-Okigwe-Afikpo trending cuesta (Figure 2). The cuesta trends from north to south with its east-facing scarp slope rising between 200 and 300 m above the Cross River plains. The Cuesta is formed by the resistant sandstones of the Mamu formation and the lower part of Ajalli formation (Ofomata Reference Ofomata and Ofomata1978; Obi et al Reference Obi, Okogbue and Nwajide2001).
Figure 1 Map of the study area. Green rectangles indicate the iron-smelting sites and caves in Ukehe and Ozizza, respectively. (Please see electronic version for color figures.)
Figure 2 A geology map of the Nsukka-Okigwe-Afikpo cuesta area. The study sites are in red.
The vegetation of the study region varies from humid to dry with evidence of intense human activities and exploitation of resources trending along the north-south cuesta that gave rise to the dry vegetation. The notable climate is characterized by dry and wet seasons. The region experiences an average of eight months of rainfall between March and October and four months of dry season between November and February. Dominant trees found in the area include Palm tree Nkwu (Elaeis guineensis), Oha (Pterocarpus soyauxii), Bitter kola Akinu (Gacinia cola), Kola nut Oji (Cola acuminata), Cashew Ijikara (Anacardium occidentale), Pepper fruit Mmimi (Denettia tripetala),Ogirishi (Newbouldia laevis), Icheku (Dialium guineense), Oil bean Akpaka (Pentaclethra macrophylla), Native mango Ujuru (Irvingia gabonensis), Native pear (Canarium schweinfurthii), breadfruit Ukwa (Treculia africana), Star/African apple Udara (Chrysophylum albidum), and Avocado pear Ube oyibo (Pecia americannum).
METHODS
The following methods were adopted in the collection of data for this research:
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1. Reconnaissance survey and collection of ethnographic data;
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2. Excavation of selected sites;
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3. Scientific analysis of recovered artifacts/ecofacts;
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4. Pollen analysis of guano and sediment samples from the caves; and
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5. 14C estimates of charcoal and guano samples collected in stratigraphic contexts. Samples for 14C dating were sent to Beta Analytic Inc.
From the archaeological reconnaissance and survey, some sites were identified including those with features where iron was smelted in Eziamaugwu in Ukehe, and the Onualor cave filled with bat guano. Observations were made of the current use of the cave for bats and other animals/reptiles as well as for hunting. Data generated from cave and iron smelting sites were sent for further scientific analysis including the radiocarbon dating of both charcoal and guano samples (Table 2). X-ray diffraction analysis was carried out on the slag obtained from the archaeological excavations in Eziamaugwu. Aggregate slag samples discovered from the iron smelting site was used to determine the possible type of furnace used for smelting and the period of iron working following the three developmental phases of iron working technology in Nsukka proposed by Okafor (Reference Okafor, Shaw, Sinclair, Andah and Okpoko1993). In Ozizza, a rock outcrop, identified in Ogba-eju Rock Shelter was used as the datum point. The rock outcrop measured 5 feet (ca. 1.5 m) in height and situated adjacent to the rock shelter. Test-pits that measured 2 × 2 m were excavated. A total of number of six spits was dug starting from 0 to 120 cm. Materials recovered included charcoal, potsherds, quartzite, palm kernel, seed husk, snail shells and metal objects.
Radiocarbon Dates
Much reliance would be given to dateable materials (guano and charcoal fragments) from the deepest stratigraphic levels (Figure 3). The charcoal samples were sent for accelerator mass spectrometry (AMS) 14C dating at Beta Analytic Inc. in Florida, USA. These samples were subjected to pretreatment for the removal of contaminations. For the charcoal samples and guano sample at 40–60 cm, the pretreatment was the same. The sample was first visually inspected for size and durability. It was reduced to small particles (1–5 mm) through dissecting and crushing and saturated in de-ionized water at 70ºC. It was then soaked in 0.1N HCL for 1–2 hr and repeated, to eliminate any carbonates present. The sample was then rinsed to neutral; 1–2% alkali was then applied (50/50wt NaOH) at 70°C and repeated until no color change was observed. It was then rinsed to neutral. A final hot acid wash (0.5–1.0 N HCL) was applied to ensure the alkali was neutralized and once again rinsed to neutral, this time using deionized water. During this process all roots and exogeneous organic debris were removed. Samples were dried at 100ºC or desiccated for 12–24 hr, then microscopically examined for cleanliness, uniformity and, where applicable, appropriately subsampled for the measurements.
Figure 3 Stratigraphic profile of the southern wall of the Onualor cave excavation.
Palynology: Onualor and Ozizza
Five samples of bat guano (coprolites) were collected from the five (1–5) stratigraphic layers identified from the excavated 2 × 2 m test pit inside Onualor-Ogadike cave. The depths of layers 5–1 are as follows: 5 (115–140 cm), 4 (62–115 cm), 3 (38–62 cm), 2 (17–38cm), and 1 (0–17 cm). Twenty grams of the guano samples were subjected to pollen analysis. Similarly, in Ozizza, six sediment samples from the six stratigraphic layers of the excavated trench in the cave were subjected to pollen analysis. The laboratory preparation techniques included using HCl, HF, and heavy liquid (ZnCl2) mineral separation. There was no acetolysis because it would likely destroy several of the presumably fragile palynomorphs.
RESULTS
Based on the 14C dates and slag characteristics, slags identified in Ukehe were aggregate and flow slags while the bloom coagulates in ball forms were raked out from the furnace. Slags from Ukehe were similar to those found in Owerre-Elu iron smelting, which was classified under late phase of iron working in Nsukka. X-ray diffraction analysis showed the presence of minerals such as chamosite, haematite, quartz, siderite, goethite, and smectite (Figure 4a). The identified minerals categorized the slag as fayalite (Fe2SiO4) with evidence of glass. This is similar to the minerals found in the Owerre-Elu iron smelting site (Okafor Reference Okafor1992). The photomicrograph of the slag showed the occurrence of dark quartz crystal and light grey iron oxide (Figure 4b), which is similar to what was obtained in Owerre-Elu (Okafor Reference Okafor1992).
Figure 4 Slag analysis: (a) X-ray diffraction of slag from Eziamaugwu iron smelting site Ukehe; (b) microscope photograph of the (mineral) macerals from Eziamaugwu iron smelting at Ukehe.
Palynological Data from Onualor
Pollen count was low (14–35) in almost all the samples except for Layer 3 which yielded 110 pollen grains per pair of slides (Table 1). A total of 44 palynomorph types, and xylem vessels were recovered from the samples; pollen grains were 35 (79.5%), pteridophyte spores were six (13.6%) while fungal spores were four (9.1%); there were two spores of parasitic organisms and xylem vessels. Palynomorphs were classified into phytoecological groups based on the natural habitat of their parent plants (Table 1; Figure 5) for ease of interpretation. In Layer 5 (115–140 cm), the dominant palynomorphs are those the parents of which are natural to secondary (open) forests and Guinea savanna. Layer 4 (62–115 cm), showed typical woodland species natural to Guinea and Sudan savanna. For Layer 3 (38–62 cm), several economic plants, namely Elaeis guineensis, Phyllanthus discoideus, Dacryodes edulis, and Combretaceae/Melastomataceae were the main pollens recovered (Figure 6). In Layer 2 (17–38 cm), there was a paucity of pollen due probably to poor preservation. Layer 1 (0–17 cm), showed further paucity of pollen and spores; the recovered pollen included Elaeis guineensis (Figure 6) which represented secondary forests. The other pollen grains were those of rainforest, freshwater swamp forest, Guinea savanna, and open vegetation (grasses).
Table 1 Phytoecological groups and plant groups represented in the Onualor-Ogudike cave pollen assemblage.
Figure 5 Pollen diagram of excavated Onualor-Ogadike cave herb (green), shrub (magenta), tree (blue), fern (red), fungi (yellow), climber (green), and unclassified (brown).
Figure 6 Palynomorphs from bat guano in Onualor-Ogadike cave, southeastern Nigeria: 1. Alternanthera sp.; 2. Protea sp.; 3–4. Nauclea diderrichii 5; Combretaceae/melastomataceae; 6. Meliaceae; 7. Poaceae; 8–9. Elaeis guineensis; 10. Pteris sp; 11. Parinari sp.; 12–13. Pentaclethra macrophylla; 14–15. Unidentified; 16. Trichuris sp.; 17. Entada abyssinica; 18. Piptadenistrum africanum.
DISCUSSION
This study gives evidence of early iron/metal working in pre-colonial period in the northern Igbo communities. Pit/bowl furnace is believed to be earliest furnace and iron smelting technology that was extensively deployed in Opi, Lejja, and Nwofe which produced the “giant” slags not yet reported elsewhere in Nigeria. These sites are contemporaneous with but not earlier than the Nok sites notwithstanding the radiocarbon date of 2000 BC iron smelting site of Lejja in Nsukka area Eze-Uzomaka (Reference Eze-Uzoamaka2009). Pole (Reference Pole2010) has however, expressed some reservations on the Lejja date. From the available evidence, it could be argued that the northern Igboland, Nsukka area, in particular, assumed one of the important centers of iron smelting technology in Nigeria.
This fact was achieved by possibly itinerant iron workers that moved from one location to another based on availability of the raw materials haematite ore and hard wood for charcoal making. For better understanding of the impact of early ironworking the issue of origin(s), according to Pole (Reference Pole2010) need to be de-emphasized because of its implicit racial and/or ethnic superiority. Instead, the socio-cultural, as well as economic contexts, should be explored. This would yield more significant benefit to human societies and understanding of intergroup relations within and between various societies.
The socio-cultural contexts of iron smelting/smiting in the study area has been highlighted by Okpoko and Ibeanu (Reference Okpoko, Ibeanu and Okpoko1999; Eze-uzomaka Reference Eze-Uzomaka2013) and need not be re-emphasized in this paper. However, it should be noted that the present inhabitants of the communities which were once iron smelting sites in Nsukka area are ignorant of the iron smelting processes. Presently, various myths are woven around Lejja iron smelting by the community (Opata and Eze-Uzomaka Reference Opata and Eze-Uzomaka2012). This differs from the sites of Umundu in Nsukka that falls within the late phase of iron smelting. In this community as noted by Anozie (Reference Anozie1979, Reference Anozie1985) the elders were able to recollect their observation as children how their forebears smelted iron and produced charcoal for smelting. The Umundu elders were asked to re-enact the processes of iron smelting. They built a shaft furnace with mud wall and the experiment was a near success in the Department of Archaeology and Tourism, University of Nigeria, Nsukka.
The interpretation of the pollen data from Onualor indicated that the cave experienced fluctuation in vegetation from the Late Holocene till recent years. For instance, layer 5, the earliest deposit in the cave, had a complex of dry/secondary rainforest and freshwater swamp forest while elements of (wetter) Guinea savanna were also present (Table 1, Figure 8). It likely experienced humid and warm conditions. During Layer 4, dated to 4650 ± 30 BP (Table 2), the inferred vegetation was largely dominated by Guinea savanna (dry type) and Sudan savanna; conditions were very dry and perhaps unfavourable such that the cave might have been temporarily abandoned or had very little human presence. During Layer 3, there was a return to wet conditions and an expansion in rainforest species (Figure 8). In Layers 2–1, marked changes in the surrounding vegetation resulted in sparse trees and shrubs, an event that corresponded to a combination of climatic and human activities. It should be noted that layers 3–1 coincided in part, with increased human impact on the landscape, particularly, the iron smelting activities, in the region. Furthermore, the occurrence of the pollen of edible and economic plants particularly those associated with human habitation especially in Layers 5 and 3 indicated possible human presence during those times.
Table 2 New 14C dates and calibrations from Nsukka-Afikpo on the north-south trending cuesta in Igboland. Calibration program BetaCal3.21 and the IntCal13 calibration curve (Reimer et al. Reference Reimer, Bard, Bayliss, Beck, Blackwell, Bronk Ramsey, Buck, Cheng, Edwards, Friedrich, Grootes, Guilderson, Haflidason, Hajdas, Hatté, Heaton, Hoffmann, Hogg, Hughen, Kaiser, Kromer, Manning, Niu, Reimer, Richards, Scott, Southon, Staff, Turney and van der Plicht2013) and NHZ3 bomb peak data for the modern (Hua et al. Reference Hua, Barbetti and Rakowski2013) were applied. Please see Figure 7(a–f) for calibration curves generated using IntCal20.
Figure 7a Calibration curve: Guano from 60–80 cm. Lab code Beta-543519.
Figure 7b Calibration curve: Ozizza from 80–100 cm. Lab code Beta-543522.
Figure 7c Calibration curve: Ozizza from 60–80 cm. Lab code Beta-543523.
Figure 7d Calibration curve: EI SS charcoal from 80 cm. Lab code Beta-543524.
Figure 7e Calibration curve: Onualo charcoal 20–40 cm. Lab code Beta-543521.
Figure 7f Calibration curve: Guano from 40–60 cm. Lab code Beta-543520.
Figure 8 Palaeoecological groups in the excavated unit in Onualor-Ogadike cave, Enugu State, southeastern Nigeria.
Figure 9 Palynomorphs from Ozizza cave, southeastern Nigeria: 1. Cyathidites minor; 2. Stereisporites; 3. Droseridites; 4. Distaverrusporites sp/Pteris sp.; 5. Punctatisporites major; 6. Ericipites annulatus Gonza; 7. Dictyophyllidites harrisii; 8. Cingulatisporites; 9. Numulipollis neogenicus; 10. Laevigatosporites discordatus Pflong; 11. Araucaria cites sp.; 12. Stereisporites sp.; 13. Mauritidites sp.; 14. Monoporites annulatus; 15. Psilastephano colporites laevigatus; 16. Nymphaea lotus; 17. Cingulatisporites ornatus; 18. Gleicheniidites sp.
Palynological studies of sediment samples from Ogba-eju cave in Ozizza revealed an abundance of fern spores (Figure 9). Ferns are particularly prevalent in moist areas. The sediments deposited during the earliest period (120–80 cm) seem to have been fairly humid considering the relatively small number of fern spore types recovered. In the middle section (80–40 cm), the palynomorphs decreased while fern spores decreased significantly; an explanation for this is that conditions became drier leading to the subsequent decrease of the ferns (Table 3). In the latest period (40–0 cm), the increase in the fern communities was an indication that conditions improved. The inferred vegetation changes seem to generally correlate with those of Onualor in the following ways: the earliest levels of Onualor and Ozizza reflected humid conditions which was followed by some dry conditions and then subsequently by wet conditions. However, unlike in Onualor, the impact of humans was not noted in Ozizza. It must however be stated that due to the lack of 14C dates from Ozizza, it is difficult to correlate the data with those from Onualor much less the iron smelting site of Eziamugwu.
Table 3 Palynomorphs represented in the Ozizza cave.
CONCLUSION
The results of the study in Onualor cave, Eziamugwu iron smelting site and Ozizza rockshelter seems to suggest evidence of early human activities within the areas. In Onualor, there is evidence of fluctuating environmental conditions from humid to dry and moist in the Late Holocene. Similar palaeoenvironmental conditions were inferred for Ozizza, although it was difficult to correlate Ozizza with the other sites because of the lack of dates.
Furthermore, the presence of these edible plants’ pollen possibly suggested the predominant of these plants and human activities in and around the study area. Apart from bat, the presence of high percentage of phosphate in the cave sediment seems to suggest human use and organic decay in the cave as was found in Okigwe cave (Ibeanu Reference Ibeanu2000). Human migration along the cuesta (Afigbo Reference Afigbo and Afigbo1987) seems to suggest movement from Nsukka to Okigwe and lastly to Afikpo area. The early date of Onualor cave, possible period of human settlement tarries with Uhuchukwu in Okigwe dated 4691 ± 78 BP (Umeji et al. Reference Umeji, Ibeanu and Agwu2012), this date showed period of human occupation and activities in the cave which is near to the period of human occupation in Onualor cave while Ozizza seems to suggest the later occupation. The analyses shows the rockshelter in Ukehe and Ozizza indicates the occurrence of past environmental changes as well as the effects of anthropogenic activities in the region. However, the narrow range of dates between Onualor and Okigwe seems to suggest contemporaneity of human activities in the two caves located to the north and south of the trending cuesta.
ACKNOWLEDGMENT
Our sincere appreciation goes to TETFUND, which provided grants (TETFUND/DESS/UNI/NSUKKA/2018/RP/ VOL.1 University of Nigeria, Nsukka) for the radiocarbon dating.
