Modern humans in Sarawak, Malaysian Borneo, during Oxygen Isotope Stage 3: palaeoenvironmental evidence from the Great Cave of Niah

Journal of Archaeological Science 34 (2007) 1953e1969 http://www.elsevier.com/locate/jas

Modern humans in Sarawak, Malaysian Borneo, during Oxygen Isotope Stage 3: palaeoenvironmental evidence from the Great Cave of Niah Chris O. Hunt a,*, David D. Gilbertson b, Garry Rushworth c a

School of Archaeology and Palaeoecology, Queen’s University of Belfast, 42 Fitzwilliam Street, Northern Ireland, Belfast BT7 1NN, UK b Department of Geography, University of Plymouth, Plymouth PL4 8AA, UK c Department of Geography & Environmental Science, University of Bradford, Bradford BD7 1DP, UK Received 13 December 2006; received in revised form 13 February 2007; accepted 25 February 2007

Abstract During recent reinvestigations in the Great Cave of Niah in Borneo, the ‘Hell Trench’ sedimentary sequence seen by earlier excavators was re-exposed. Early excavations here yielded the earliest anatomically-modern human remains in island Southeast Asia. Calibrated radiocarbon dates, pollen, algal microfossils, palynofacies, granulometry and geochemistry of the ‘Hell Trench’ sequence provide information about environmental and vegetational changes, elements of geomorphic history and information about human activity. The ‘Hell’ sediments were laid down episodically in an ephemeral stream or pool. The pollen suggests cyclically changing vegetation with forest habitats alternating with more open environments; indicating that phases with both temperatures and precipitation reduced compared with the present. These events can be correlated with global climate change sequences to produce a provisional dating framework. During some forest phases, high counts of Justicia, a plant which today colonises recently burnt forest areas, point to fire in the landscape. This may be evidence for biomass burning by humans, presumably to maintain forest-edge habitats. There is evidence from palynofacies for fire on the cave floor in the ‘Hell’ area. Since the area sampled is beyond the limit of plant growth, this is evidence for human activity. The first such evidence is during an episode with significant grassland indicators, suggesting that people may have reached the site during a climatic phase characterised by relatively open habitats w50 ka. Thereafter, people were able to maintain a relatively consistent presence at Niah. The human use of the ‘Hell’ area seems to have intensified through time, probably because changes in the local hydrological regime made the area dryer and more suitable for human use. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Borneo; Sarawak; Palaeoenvironment; Palynology; Palynofacies; Human impact; Biomass burning; Colonisation; Late Pleistocene; Climate change; Savannah corridor

1. Introduction This paper describes stratigraphic, sedimentary and palynological evidence for changing environments during Oxygen Isotope Stage 3 (OIS 3) at an area known as ‘Hell Trench’ in the West Mouth of the Great Cave of Niah, Sarawak, and Malaysian Borneo (Fig. 1), which was the find-spot for the ‘Deep Skull’, a morphologically modern human skull associated with a radiocarbon date for w42 BP (Harrisson, 1958)

* Corresponding author. Tel.: þ44 2890 975147. E-mail address: [email protected] (C.O. Hunt). 0305-4403/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2007.02.023

and thus for many years the oldest morphologically modern human remains known in the region. The evidence described in this paper enables us to address two much-discussed but still under-researched issues. These are outlined below. 2. Biogeography and rain-forest refugia in OIS 3 e evidence and conjecture Although the period w35e50 ka is of critical importance for understanding the dispersal and subsistence of anatomically modern humans, there is a dearth of palaeoecological information from OIS 3 terrestrial sites in Island SE Asia. Biogeographical arguments, on the basis of modern faunal

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C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

Fig. 1. Geological map showing the outcrop of sedimentary layers in the Archaeological Area in the West Mouth of the Great Cave of Niah and (inset) location in Borneo after data in Gilbertson et al. (2005).

distributions, hold that the ‘coastal’ lands of north and northwest Borneo, including Niah, may have remained sufficiently humid during the Late Pleistocene to have been a refugium for lowland rainforest (Brandon-Jones, 1998; Gathorne-Hardy et al., 2002). As yet, there is no palaeoenvironmental evidence to test this theory. Pollen diagrams from Lake Sentarum and Setia Alam in west-central and south-central Borneo (Anshari et al., 2004; Kershaw et al., 2001) provide evidence for tropical rainforest during the Late Glacial Maximum (LGM) in those areas. It is suspected, however, that during these times dry dipterocarp woodland and savannah expanded into regions now occupied by humid lowland rainforest (Hope et al., 2004; Bird et al., 2005). It was hypothesised that, in ‘‘Sundaland’’ (the continental shelf north-west of Borneo exposed by sea level fall during glacial periods: Molengraaf 1921, Voris 2000) and other low-lying areas, the extent of lowland rainforest increased (Sun et al., 2000). Further to the northwest, however, palynological evidence from the continental shelf suggests episodically more open vegetation, perhaps associated with the input of abundant Artemisia pollen and loess from central Asia (Sun et al., 2000). Cranbrook (2000) investigated the many vertebrate and invertebrate

remains that are broadly associated with the Niah ‘‘Deep Skull’’ at w40 ka. These included Presbytis and Pongo: the overall assemblage implying the local presence of tall evergreen rainforest forest and some open habitats. The Late Pleistocene was generally subjected to highly episodic climatic fluctuations with a wide range of variations in precipitation and temperature (Shackleton et al., 2004). During the Last Glacial Maximum in Borneo, offshore sea water temperatures may have been w2e3  C lower than today, while air temperatures may have been reduced by 6e7  C (Bird et al., 2005). The estimated reduction in annual precipitation at the LGM compared to the present is substantial, the cooler annual air temperatures being associated with a reduction of precipitation of w30e50% (Sun et al., 2000; Kershaw et al., 2001; van der Kaars et al., 2000; Hope et al., 2004; Bird et al., 2005). The modern climate in the area is affected on a daily basis by coastal winds, modulated within the year by the distinctive seasonal reversal of winds and storms associated with the East Asian and Australian monsoons, whilst El Ni~no episodes can bring strong and sustained droughts and sometimes fire in the region. It is probable that similar variability occurred in the past. There is, however, little compelling evidence to help us reconstruct the vegetation of this area between w30 and w50 ka.

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

3. Palaeobiogeographical modelling, human dispersal, subsistence and biomass burning The environment offers potential opportunities and constraints to people: thus a detailed understanding of the environment at the time of the early use of the cave constrains archaeologically based models of human activity. Recent modelling constrained by palaeo-topographic and palaeo-climatic information, but not supported by any new palaeoecological data (Bird et al., 2005) suggests that much of ‘‘Sundaland’’ at and before the LGM could have included substantial areas (or indeed a corridor) of savannah or open woodland, reviving an earlier interpretation of this landscape. This model could have critical importance for understanding human behaviour, dispersal and subsistence in the lowland tropics of Island Southeast Asia during OIS3. Human movement and activity in terrain covered in wet lowland rainforest are very different from similar activity in grasslands, savannah or even open woodlands. According to some commentators, sustained human activity based on foraging for animal proteins would have been difficult, if not impossible, in an environment dominated by deep wet tropical forest, as is present at Niah today (e.g. Headland, 1987; Hutterer, 1988; Bailey et al., 1989; Townsend, 1990; Bailey and Headland, 1991; Dentan, 1991). Limited archaeological evidence (Bellwood, 1997) suggests that foraging in wet tropical lowland forest might have occurred during the Late Pleistocene elsewhere in Island Southeast Asia: the biogeographical evidence discussed above might suggest similar environments around Niah. Yet, it is clear that people were at Niah during OIS 3. Thus, if tropical forest was present at Niah, the people must have developed strategies to deal with it. If tropical forest was not present, this suggests different scenarios for human activity. One important strategy e biomass burning e seems to have been widely used by people to deal with dense wet tropical forest. Biomass burning apparently related to human activity at w40,000e30,000 BP has been widely recognised in the region. High concentrations of micro-charcoal have been detected in deposits correlated with OIS 3, through the southern parts of Island SE Asia and into Australasia, and offshore in the Bandung Basin, Java, on the Lombok Ridge south of Flores, in the Banda Sea, on the north Australian continental slope at ODP 820 and on land in north Australia at Lynch’s Crater (Turney et al., 2001; Haberle et al., 2001; Kershaw et al., 2002; Hope et al., 2004; Thevenon et al., 2004). The practice of biomass burning during the Late Pleistocene has not yet been recognised in the northern part of Island Southeast Asia. As a result, it was not known how Late Pleistocene human activities around the Great Cave might differ from those of people further south who appear to have burned biomass as part of their pattern of activities.

4. The Great Cave of Niah The Great Cave of Niah is one of the largest and most intensively studied caves in Sarawak, Malaysian Borneo. In

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many ways the site is still a cornerstone archaeological site in Southeast Asia. Between 1954 and 1967, Tom and Barbara Harrisson excavated in the West Mouth of the Great Cave of Niah (Fig. 1). They recorded and partially published probably the most important archaeological sequence yet recovered in Island Southeast Asia. A critical find was the ‘Deep Skull’. This was recovered from some 1.6 m below the local surface of the sedimentary fill of the West Mouth in an excavation unit named ‘Hell Trench’ by the Harrissons. The trench name apparently refers to the extremely uncomfortable working conditions in this area, characterised by confined air circulation, strong ammonia flux from the sediments, very high humidity and extreme warmth. Associated charcoal was subjected to one of the earliest archaeological applications of radiocarbon dating, through an ‘enhancement technique’ at Groningen, and an age of w42,000 radiocarbon years established (Harrisson, 1958, 1959a,b; Barker et al., 2002b; Gilbertson et al., 2005), for decades making this skull the oldest skeletal remains of an anatomically modern human in the world. It is clear from Tom Harrisson’s manuscript notes and from notes and diagrams made by Lord Medway that they distinguish distinct sedimentary units, but these were not described in their published accounts (Gilbertson et al., 2005). A combination of the absence of a published stratigraphy, the possibility that the ‘‘Deep Skull’’ might be intrusive from much younger burials, and general doubts about the ageedepth approach used by the Harrissons has led to doubts not only about the antiquity ‘‘Deep Skull’’ (Anderson 1997; Bellwood, 1997; Gilbertson et al., 2005), but also perhaps about other aspects of T. Harrison’s work (see also Zuraina Majid, 1982). Further, in spite of the involvement of a number of specialists in these early excavations, there was no published detailed assessment of the environmental context of this e at that time e earliest modern human activity in Island Southeast Asia and Australasia. The position was still substantially the same before the start of the Niah Cave Project (of which this paper is an outcome) in 2000. The Great Cave lies at the northeast corner of the Gunung Subis, an isolated tower karst massif in Miocene patch-reef limestones of the Subis Limestone Member of the Tangap Formation (Leichti et al., 1960; Wilford, 1964; Banda, 2001). The Great Cave lies some 64 km SSW of Miri, the regional capital, and 12 km inland from the coast of the South China Sea. It lies only 1e2 km from the tidal waters of the Sungai Niah, however, and the very deepwater of the Northwest Sabah-Palawan Deep Ocean Trough is just 150 km to the north. The Island of Borneo lies in some of the warmest seas on earth, with modern temperatures averaging w28  C (Yan et al., 2002). The South China Sea, to the North, is part of the Indo-Pacific Warm Pool, which has a major effect on the present-day wet tropical climate in Borneo (Tapper, 2002). Hazebroek and Morshidi (2001) note mean annual rainfall of w2000 mm a1 at Niah, reaching w5000 mm a1 on higher ground further inland, and a daily temperature range from 22  C before dawn to 32  C in the afternoon. Around the Gunung Subis are coastal mangrove and alluvial swamp forests, with lowland

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

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dipterocarp forests on low-relief topography developed in Tangap Formation siltstones and sandstones (Pearce, 2004). The West Mouth is the largest of the mouths of the Great Cave, a low arch up to 60 m high and 180 m across. It opens w12 m up the cliff-like side of the rock-floored gorge which separates the karst tower containing the Great Cave from the main massif of the Gunung Subis. The cave mouth is partly blocked by a rampart of speleothem and rockfall debris and by vegetation (Gilbertson et al., 2005). The Harrisson excavations are on the north side of the West Mouth, immediately inside the entrance to the cave (Fig. 1). Further location details are given by Barker et al. (2000, 2002, 2007). The research reported here has proceeded directly from cleaned-up exposures left by T. Harrisson and Zuraina Majid in the West Mouth. It is part of a multidisciplinary re-investigation which has examined both the remaining exposures and the large archived collections in the Sarawak Museum’s collections (Barker et al., 2000, 2001, 2002a,b, 2003, 2005, 2007; Barker, 2005; Gilbertson et al., 2005). Taphonomic research investigating the contemporary depositional patterns of guano and airfall material in the West Mouth (Hunt and Rushworth, 2005a) showed that there are gross lateral variations in sedimentation rate and type, with a zone in the cave mouth dominated by wind-blown silt and airfall pollen, with the interior of the cave dominated by guano from bats and swiftlets containing very abundant pollen derived from their foraging activities. The stratigraphy of the remaining Late Quaternary sedimentary sequence exposed in the West Mouth has been described recently (Dykes, in press; Gilbertson et al., 2005; Stephens et al., 2005; Table 1). The West Mouth sediments are the result of airfall, wash, fluvial, colluvial and mudflow processes, with episodic surface ponding and drainage (Gilbertson et al., 2005). Recent unpublished and published investigations of the remaining excavation faces in and around the ‘‘Hell Trench’’ also indicated that traces of human activity in the West Mouth of the Great Cave occur from 45,900  800 BP uncalibrated (OxA-V-2057-31) (Barker et al., 2001, 2002a,b, 2007; Barker, 2005; Gilbertson et al., 2005). Thereafter, there was episodic human activity through the Late Pleistocene and most of the Holocene. This research is offering insights into human behaviour in the cave and in its hinterland.

As part of this, the palynological, sedimentological and geochemical investigations described here identify changing environments and traces of human activity inside and outside the cave during part of OIS 3. 5. Materials and methods In the West Mouth excavation area, Gilbertson et al. (2005) distinguish four major sedimentary units of Pleistocene age (apart from a thin band of fluvial deposits (unit 5) adjacent to the cave wall). These are briefly described in Table 1, with present emphasis on their Unit 2 which yielded the samples described here. Unit 2 is a sequence of waterlain and colluvial deposits. Field and micromorphological studies indicated that this deposit accumulated during episodic small floods of limited power, in small pools and as small mudflows, in a linear hollow eroded into underlying components of Units 2C and 1 and the limestone bedrock of the cave entrance lip. The accumulating sediments of Unit 2 were prone to dry out, producing polygonally cracked muds that were re-entrained by later flows and re-deposited as rip-up clasts. The hollow opened to the north into a basin 10e15 m across where the water drained through the sedimentary fill into a swallow-hole inferred from geophysical data. In sediment-thin sections, bone, charcoal, and other localized evidence of human activity were observed upon former palaeosurfaces together with fluviallyproduced graded bedding and water-escape structures (Stephens et al., 2005). Small accumulations of ash and charcoal lie in shallow depressions, typically 30 cm across, on old land surfaces in this unit. These might be interpreted as the remains of fires. One surface could be extrapolated directly to the inferred find-spot of the ‘‘Deep Skull’’ (Barker et al., 2002a,b, 2007) although the actual location was completely removed by the earlier investigations. The western margin of Unit 2 interdigitates with Unit 2C, a complex of slope, colluvial and organic deposits and archaeological remains (Table 1). Unit 2C also includes the debris from the collapse and disintegration of a large speleothem column, which on the evidence of field relationships, took place during the accumulation of this unit. Material shed from human activity on the cave entrance lip accumulated with Units 2 and 2C.

Table 1 Summary stratigraphy in the Hell Trench area of The Great Cave, Niah (after Gilbertson et al., 2005) Unit

Approximate age (ka BP)

Thickness (m)

Description

1 2

>50 45e38

>0.7 >2.5

2C

45erecent

>2.5

3

32e38

1e3

4

19.5e8.5

>4

Light yellow-brown sands with selenite crystals up to 2 cm long overlain unconformably by all later deposits. Strong-brown sands, silts, clays and diamicts showing clear trough cross-bedding, ripple marks and planar bedding, with isolated clay rip-up clasts and concentrations of bone and charcoal. Interdigitates with Unit 2C and has an erosive boundary, with ample evidence of deformation and liquefaction along the contact with Unit 3. Light yellow-brown stony silty-clay diamict, highly calcareous, containing charcoal, lenses of wood ash, lithic artefacts, and bone, in the highest part, potsherds. Dips off the cave entrance-rampart and interdigitates with Unit 2. Pale brown to brown silty diamict with abundant secondary gypsum up to 5 cm in diameter. Crudely bedded, with bedding dipping towards the cave mouth and contains rafts of guano and of sand derived from Unit 2. The sediment body has a lobate form and along its boundary with Unit 2 shows wet sediment deformation and injection structures containing sands derived from Unit 2. The upper part (3R) is more regularly bedded and contains charcoal and bone. Yellow-brown to light yellow-brown silty diamict with occasional cobbles and abundant bones and molluscs. Overlies Units 2, 2C and 3 and interdigitates with upper part of 2C.

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Distinct variations in the three-dimensional geometry and lithological properties of Unit 2 were mapped in the field; and it is probable that many plant and animal remains and distinctive ‘‘concentrated bone’’ assemblages recorded by Harrisson (1965, 1970) were parts of the deposits that are now attributed to this lithofacies. The faces of the excavations by the Harrissons and their local extension by Zuraina Majid (1982) were sound and in good condition and were thoroughly cleaned back to reveal fresh sediment for the stratigraphical study. These faces were then further prepared using a cleaned trowel, immediately before sampling for this study. Five monoliths were taken to provide a continuous set of samples through the thickest and most complete sequence remaining of Unit 2 (Figs. 1 and 2). Monoliths were wrapped in aluminium foil and cling wrap and stored briefly in an air-conditioned room before return to the UK. In the UK, they were stored in a cold room at 4  C before analysis. This study reports investigations of monoliths 1e3. Macroscopic charcoal was extremely rare in this sequence. Spot samples for dating were taken, therefore, where charcoal was visible in the cleaned faces and AMS dated using the ABOX-SC technique (Bird et al., 1999) at Canberra in the Research School of Earth Sciences. The results of the dating programme are described and evaluated by Bird (2001) and further discussed below. The studied sequence lies stratigraphically immediately below a feature containing charcoal dated by Bird (2001) to 42,600  670 BP (Niah-310). A few centimetres higher a fragment of charcoal gave a date of 41,800  620 BP (Niah-311). Below these dates the chronology of the section is thus largely inferential. It is ‘anchored’ at the top by the radiocarbon ages, but no material suitable for radiocarbon analysis was found below these levels in this profile. As yet, attempts to provide parallel series of OSL age estimates are

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not yet fully resolved (Stephens, 2004; Stephens et al., 2007). As a result, the somewhat risky procedure of matching the studied sequence against global standards, such as the GRIP record (Dansgaard et al., 1993; Johnsen et al., 2001; Shackleton et al., 2004) is followed here. There are problems with this approach, because the GRIP record is itself dated largely by extrapolation from relatively few securely dated points (Shackleton et al., 2004) and not all authorities are yet convinced that the sub-Heinrich climatic changes have global expression. Shorttimescale climatic oscillation in the Australian tropics has, however, been argued to be in phase with the GISP2 O18 DeO cyclicity (Turney et al., 2004). All analysed samples reported here for palynology, diatoms and geochemistry were taken from monolith faces 1e3 that were cleaned immediately before analysis in the laboratory. Each monolith was opened in turn and 5 cm thick subsamples were taken for analysis. These were divided between various analyses described below. Samples for chemical and granulometric work were dried at room temperature in covered food-grade plastic trays, and then gently disaggregated with pestle and mortar until fine enough to pass through a 2mm stainless steel sieve. Geochemical analysis on bulk powder samples was carried out using a Spectro X-Lab XRF machine. Further detailed analysis was carried out using ICPMS (Grattan et al., 2004). Calcium carbonate was determined with a Bascomb Calcimeter following the procedure of Gale and Hoare (1991). Magnetic susceptibility was determined using a Bartington MS1. Loss on ignition was done using the low temperature method of Gale and Hoare (1991) with combustion at 425  C for 24 h. Analysis of granulometry was done using the Pipette method (Gale and Hoare, 1991). Palynological methods follow a variation of the method of Hunt (1985), which has been shown to give the best recovery

Fig. 2. The stratigraphy in ‘Hell Trench’ in the Great Cave of Niah and the location of the monoliths 1e3 used in this study.

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C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

in cave sediments where acetolysis destroys fragile pollen and spores (Coles, 1989). Subsamples of 5 cm3 were disaggregated by boiling in 5% sodium hydroxide solution for 10 min, then 3% sodium pyrophosphate solution for 10 min, and then sieved on nominal 6 mm nylon mesh to remove fines and solutes. Coarse clastics and small fossils were removed by sieving through 120 mm nylon mesh. The resulting suspension was decalcified by addition of 5% hydrochloric acid. One slide was made up from each sample at this stage, but pollen concentrations were rather low in many samples. The samples were then treated with cold 20% hydrofluoric acid for two days, and then carefully neutralised by dilution. The neutralised samples were then washed in warm hydrochloric acid, sieved on 6 mm nylon mesh, alkalinised using 5% KOH solution and stained with safranin before mounting in modified Gurr Aquamount. All procedures were carried out using distilled or filtered water and blanks were run to ensure the integrity of the procedures. Analysis of pollen was done in transmitted light and Nomarski interference contrast at 400 and 1000 magnification. The pollen samples were checked for integrity and coherence using UV-fluorescence microscopy (Hunt et al., 2007). Palynofacies analysis enumerates all the particulate organic matter present in a palynological sample. It differentiates local patterns of environmental change and human activity by using patterns of particulate organic matter occurrence (Hunt and Coles, 1988). This approach, while successful in other archaeological contexts (Hunt and Coles, 1988; Hunt, 2000; Hunt et al., 2001, 2002; Hunt and Rushworth, 2005b), has not been used in an archaeological cave site previously, so this study evaluates the usefulness of this approach. Palynofacies counts used the slides prepared for the pollen analysis using the conventions of Hunt and Coles (1988). In the palynofacies counts, material which is brown to dark brown in colour as a result of strong heating is described as thermally mature. Much thermally mature material shows residual cellular structures and can be equated with the material described as ‘microcharcoal’ by some pollen analysts. Other thermally mature material is without regular structure and can be described as amorphous: unpublished taphonomic studies by COH suggest that this material results from the heating of unstructured (amorphous) organic matter in the soil below small fires. The other categories used in this account should be self-explanatory. 6. Results 6.1. Sedimentology Monoliths 1e3 in Unit 2 of the ‘Hell’ sequence consist of trough cross-bedded and occasionally plane-bedded strongbrown sands, silts, clays and diamicts (Gilbertson et al., 2005). Most samples are relatively poorly sorted and can be described as sandy silty clays, silty sandy clays and silty clayey sands. Ripple marked sand bodies and diamict plugs are apparent in the infills of some scours. Occasional concentrations of bone and charcoal, together with isolated reddened clay rip-up clasts are present at the base of some scours. Grainsize analysis (Fig. 3) shows at least 10 cycles of changing

grain-size in the sediments sampled in this study, with sand peaks at 203, 188, 153, 143, 123, 103, 78, 68, 43 and 8 cm. The change in grain size is variable in direction e a coarsening-upward unit is apparent at the base of the section and others at 103e88 cm and 38e30 cm, but fining-upward units are also apparent, e.g. at 203e190 cm, 143e128 cm and 43e33 cm. These cycles of changing grain size are consistent with the trough cross-bedding seen in the sampled sections and most probably reflect pulses of ‘flashy’ discharge in a small channel aligned NortheSouth through the ‘Hell’ area (Gilbertson et al., 2005). Coarsening-up probably reflects increasing turbidity, while fining-up cyclicity most probably reflects declines in the turbidity of flows. The diamict plugs most probably reflect places where either the ‘tail’ of a flow event was exceedingly turbid and graded into a small mudflow, or where a small mudflow from the guano pile in the cave entered the channel. The ripple-marked horizons suggest that shallow water subject to slow flow or (less probably in the context of the cave-mouth) to wind disturbance. The concentrations of bone and charcoal sampled are most probably lag deposits, where fine materials were winnowed out by fluvial erosion leaving these larger elements behind. Samples with over 50% clay occur at 213e208, 193, 168, 148, 128, 113, 88e83, 63 and 33e3 cm e these may reflect episodes of quiet-water sedimentation, where clay settled out of residual pools, except between 33 and 3 cm, where the sediments appear to be mostly sand-sized clay pellets, which probably behaved hydrologically as sand. Alternatively, it is possible that some concentrations of clay may reflect formation of clay minerals by pedogenic processes during still-stands in deposition, though this remains to be verified by thin-section analysis. Clay ripup clasts reflect desiccation of clay-rich quiet-water deposits, with the consolidated hardened clay fragments then caught up in subsequent flash-floods and redeposited. The red-brown colours of the unit suggest that some, but not all, of the material is either derived from, or shares a common origin with, red clay soils that can be observed on the summit of the Gunung Subis massif. Red clays are also visible lower in the depositional sequence in the cave (Gilbertson et al., 2005). The origin of the silt-sized material which is predominant in the Hell sequence is problematic e the Subis Limestones contain remarkably little silt-sized clastic material. Loessic input to the South China Sea during the Late Pleistocene was suggested by Sun et al. (2000) and the grain size characteristics of these cave deposits are perhaps consistent with them being partially derived from loess. 6.2. Geochemistry The geochemistry through the ‘Hell’ sequence is remarkably uniform across the studied section (Figs. 4e6). The most common elements through the whole sequence are Silicon (34e57%), Aluminium (19e29%), Phosphorus (18e 27%) and Calcium (1e16%). Loss on ignition, which varies between 3 and 17%, is likely to include organic matter and weight loss by the dehydration of gypsum during the combustion (although this is likely to be minor given the low figures

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Fig. 3. Grain size analysis of the ‘Hell’ sequenceemonoliths 1e3.

for sulphur, discussed below). Low-frequency magnetic susceptibility is low, between 0.4 and 1.2 susceptibility units. It is highest in zones H-9 and H-10. The Aluminium and Silicon relate to silicate and alumino-silicate minerals, probably mostly quartz silt-sand and clay minerals. The high Phosphorus is likely to be derived partly from bone apatite (Calcium Phosphate) and partly from bird and bat guano. Some Calcium is present as Calcium Carbonate, but the calcimetry indicates that this is minor except in zones H-5 and H-6. A little Calcium is also likely to be present as gypsum (hydrated Calcium Sulphate), but the low figures for Sulphur suggest that this is an unimportant component of the sediments. Elsewhere, most Calcium not present as calcite is probably present in bone apatite. There is no evidence for human occupation in the metal geochemistry. Values for zinc (10e44 ppm) and copper (4e7 ppm) both fell below crustal averages (Wedepohl, 1995). Lead values (9e51 ppm) do occasionally fall above the crustal average, but the mean value 20 ppm is very close to the crustal average value of 17 ppm. Crudely, the sequence can be divided into seven (Table 2), the boundaries in most cases coinciding with the boundaries of pollen zones. 6.3. Palynology In general, the preservation of pollen in monoliths 1e3 is extremely good, with virtually all grains in all samples threedimensional and taking stain in a uniform way. The fluorescence colour of pollen in all samples under UV is a uniform

dark red. The uniformity of the fluorescence signature, and the uniform staining characteristics of the material are consistent with a simple and uncomplicated taphonomic pathway and a lack of recycled or intrusive material (Hunt et al., 2007). Pollen was identified using Bernard Maloney’s type collection, held at Queen’s University, Belfast. Some pollen could not be identified because no type material existed or because it was obscured by debris. These were logged as Indeterminate. The upper part of the sequence, however, contains a number of horizons containing no pollen at all, although in most of these, particulate organic carbon is present and was evaluated in the palynofacies counts. High concentrations of phytoliths are present in the pollen slides from samples that do not contain pollen. This phenomenon is discussed further below. A series of eleven pollen assemblageebiozones (hereafter termed zones) was distinguished (Table 3). In the following sections and in Figs. 7e10, pollen taxa are described as % total pollen and spores, excluding Justicia, together with juvenile pollen which are sometimes so common that all other palynological signals would be obscured if they were included in the pollen sum and which are therefore calculated and displayed as a percentage of the other pollen and spores (Fig. 9). Algae are computed as % pollen and spores (Fig. 9) and palynofacies are computed as % palynofacies (Fig. 10). In Figs. 7e9, where the pollen sum is less than 100 the histogram bars of the pollen diagram are unshaded. The pollen biostratigraphy is used as a framework for the later parts of the paper.

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

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Fig. 4. Geochemistry from XRF, calcimetry, magnetic susceptibility and loss-on-ignition values for the ‘Hell’ sequence in monoliths 1e3.

7. Discussion 7.1. Establishment of a chronology Deposition in the Hell sequence was certainly not continuous. Textural, geochemical, field and stratigraphic evidence have been presented in this paper to show that deposition was episodic, with several still-stands. The boundaries between pollen assemblage biozones in this sequence are mostly very sharp, suggesting of discontinuities in deposition. Thus, occasional relatively short-lived depositional events were most probably sampling airfall pollen that had accumulated on surfaces in the cave over the preceding weeks, months and years. The fact that there is systematic variation of pollen assemblages within some zones suggests, however, that some depositional events took several hundred years during episodes when climatic change drove vegetational change. There are, however, most probably gaps of considerable e and irregular e duration between the depositional events. There is therefore the likelihood that entire climatic events, associated with vegetational

change, are not represented in the sequence described here and hence there is a possibility that the number of climatic fluctuations is under-counted. Therefore, ages derived this way can be regarded only as provisional minimum estimates. Nevertheless, the pattern of vegetational change does suggest that a series of climatic events is recorded, and the dating of charcoal in nearby baulks in the same stratigraphic unit in the cave fill, at the same altitude and less than 5 m away (Barker et al., 2002a,b, 2007), suggests that there are no very long gaps in the sequence. Immediately above the studied section, Bird (2001) obtained radiocarbon dates in stratigraphic sequence of 41,800  800 BP (Niah-311) and 42,600  670 BP (Niah-310), the latter in an archaeological feature, thus precluding recycling (Fig. 2). These were calibrated using the program of Fairbanks et al. (2005) to provide ages of 45,500  695 and 46,200  624 cal. BP (Table 3). The substantial percentages of mangrove and lowland forest pollen during biozones H-9 to H-11 at the top of the studied section (Fig. 9) is consistent with this being a time of major marine transgression and

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

Fig. 5. Geochemistry of common elements from ICPMS in the ‘Hell’ sequence in monoliths 1e3.

Fig. 6. Geochemistry of selected rarer elements from ICPMS in the ‘Hell’ sequence in monoliths 1e3.

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C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

Table 2 Key geochemical characteristics of the ‘Hell’ sequence e monoliths 1e3 Depths (cm)

Major elements

Other characteristics

215e190

High Silicon (c.50%), moderate Aluminium (c.23%), Phosphorus (16%) and Calcium (10%). Other measured elements below 1%. Lower Silicon (c.43%) and Aluminium (c.21%); higher Phosphorus (23%) and Calcium (13%). Lower Silicon (c.40%), moderate Aluminium (c.22%) and Calcium (c.13%); raised Phosphorus (c.24%). High Silicon (c.52%) and Aluminium (c.26%), lower Phosphorus (c.18%), low Calcium (c.2%). Lower Silicon (c.47%) and Aluminium (c.23%); higher Phosphorus (c.22%) and Calcium (c.4%). Higher Silicon (c.50%) and Aluminium (c.25%), lower Phosphorus (c.19%), low Calcium (c.4%). Lower Silicon (c.36%) and Aluminium (c.19%); higher Phosphorus (c.24%), Calcium (c.8%), Sulphur (c.3%) and Potassium (c.5%).

Low loss on ignition (c.3%), calcimetry (c.1%) and magnetic susceptibility (0.4 units)

190e165 165e130 130e75 75e40 40e10 10e0

temperatures perhaps similar to modern. The evidence from the mangrove pollen for a high sea stand and the high percentages of swamp forest and lowland forest taxa suggest that this is probably a major interstadial. In contrast, biozone H-8 is characterised by high percentages of herbaceous taxa and little mangrove pollen (Fig. 9), suggesting a drier, more open environment and low sea levels. In many parts of the Australasian tropical zone, arid episodes are likely to be contemporaneous with northern hemisphere stadials (Hope et al., 2004: 108e 112). It thus seems likely that episodes with high percentages of lowland forest taxa may be correlated with global interstadial phases, and episodes with high percentages of open ground taxa correlate with global stadial episodes. The calibrated dates immediately above the studied section fall between 45.5 and 46.2 thousand calendar years and perhaps the most likely correlation for the immediately underlying biozones H-11 to H-9 is with GRIP Interstadial 12 of Johnsen et al. (2001). Using a ‘count from the top’ approach (Table 4) this would suggest that the interstadial represented by the lowland forest episode in H-7 to H-5 is GRIP Interstadial 13, (w49 ka: Johnsen et al., 2001) and the base of the Hell sequence is possibly late in GRIP Interstadial 14, which ends w52 ka (Johnsen et al., 2001) (Table 5). 7.2. The Pleistocene environment at Niah In this section, the results are synthesised and the Pleistocene environment at Niah reconstructed. In the absence of secure dating, the framework for this section is the pollen biostratigraphy. The biogeography and ecology of the plant taxa follow Muller (1972), Anderson and Muller (1975), Ashton (1988), Kamaludin and Azmi (1997), Morley (2000) and Pearce (2004). The ecology of the algal taxa follows Pals et al. (1980), Hunt et al. (1985) and unpublished work by COH. Taphonomic calibration is provided by Hunt and Rushworth (2005a). The start of the studied sequence in monoliths 1e3 is provisionally inferred to lie late in GRIP Interstadial 14 at

Little change Calcimetry high (c.5%), otherwise little change. Calcimetry low (c.1.2%); low loss on ignition (4%) and magnetic susceptibility (c.0.8 units) Raised loss on ignition (c.6%), calcimetry (c.1.3%) and magnetic susceptibility (1.5 units) Higher loss on ignition (c.7%), calcimetry (c.1.6%) and low magnetic susceptibility (0.6 units) Higher loss on ignition (c.8%) and magnetic susceptibility (0.8 units); lower calcimetry (c.1.3%)

w52 ka. Zone H-1, dominated by Podocarpus with some herbaceous species, is consistent with a lowered treeline e Podocarpus today is not found below 100 m regionally (Pearce, 2004) and is most common in montane forest (Muller, 1972), for instance forming monospecific stands on Mount Kinabalu. Podocarpus today is very rare in lowland Borneo outside kerangas (sparse forest developed on well-draining highly acid sand substrates: Morley, 2000: 202), suggesting that it is relatively tolerant of drought stress. Dacrydium and Casuarina, also characteristic of kerangas (Morley, 2000: 202), are present in H-1. The drought-tolerant taxa Myrica, Casuarina, and Oleaceae are found in coastal dune systems today and are also found at altitude (Muller, 1972). Most of the open-ground taxa recorded are also drought-tolerant. A climate drier and cooler than present is indicated. The abundant Saeptodinium sp. reflect an algal bloom, and thus relatively eutrophic conditions, in a relatively deep, permanent water body (Hunt et al., 1985). The high clay content may reflect deposition in quiet water. A substantial rainfall event during a relatively dry cold period can be inferred. Zones H-2 to H-4, dominated by open-ground taxa, mostly Poaceae and Cyperaceae, with herbaceous taxa such as Chenopodiaceae, Asteraceae, Lactucae and Artemisia suggest major drought stress and the retreat of forest vegetation. A rise of freshwater swamp and lowland forest taxa during H-3 might suggest a minor interstadial and a climate more similar to that of the present day than that of H-2 and H-4. The current archaeological excavations at Niah have located evidence for human activity e lithics, charcoal and cut-marked bone e at similar altitudes to the base of the sample column, less than 4 m away in the cave fill (Barker et al., 2007). The appearance of thermally mature material (often known as micro-charcoal) in H-2 suggests fire, but because this material disperses widely during burning, it is unclear whether this reflects combustion inside or outside the cave, and the agency is thus necessarily obscure. Thermally mature amorphous matter, which has a small peak in H-2, however, is likely to indicate burning local to the deposition site, since the

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

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Table 3 The pollen zonation for Hell Trench, Great Cave of Niah e monoliths 1e3 Zone

Defining taxa

Depth (cm)

Characteristics

H-1

Podocarpuse Cyperaceaee Poaceae

215e212

H-2

Poaceaee Cyperaceaee Podocarpus

212e190

H-3

Poaceaee Podocarpuse Cyperaceaee Sphagnume Quercus

190e180

H-4

Poaceaee Quercus

180e165

H-5

Lithocarpuse Dodoneae Cyperaceae

165e145

H-6

Lithocarpuse Dodonea

145e135

Zone H-7

Poaceaee Cyperaceaee Dodonea

135e110

H-8

Poaceaee Cyperaceaee Pteropsidae Podocarpus

110e85

H-9

Pteropsidae Podocarpuse Poaceae

85e50

H-10

Avicenniae Symplocos

50e35

H-11

Symplocose Podocarpus

35e0

Characterised by high Podocarpus (52%), some Cyperaceae (12%) and some Poaceae (5%), with Picea, Pinus, Myrica, Dacrydium, Sphagnum, small smooth trilete spores, Symplocos, Quercus and Asteraceae present. Saeptodinium sp. cysts are common (14%). The palynofacies is dominated by inertinite (74%), some fungal hyphae (17%) and the presence of thermally mature amorphous matter, plant cuticle and cell walls, amorphous matter, pollen and fungal spores. Characterised by high to very high Poaceae (32e68%), some Cyperaceae (8e13%) and Podocarpus (1e9%). Lactucae are present in most samples. Some samples contain Convolvulaceae, Dodonea, Myrica, Alnus, Cyathaceae, Polypodium type, Rutaceae, Ericaceae, Quercus and Pteropsida monolete. Justicia is present in some samples. Algae are present, with Spirogyra and Saeptodinium in most samples. The palynofacies is mostly inertinite (44e97%), some plant cuticle and cell walls (1e4%) and a little pollen. Most samples contain thermally mature amorphous matter, amorphous matter, fungal hyphae and fungal spores. Characterised by Poaceae (14e20%), Podocarpus (6e9%), Cyperaceae (3e19%), Sphagnum (3e13%), and Quercus (1e8%), with some Myrica (2%), Brownlowia (1.5d3%), Alnus (1e2%), Elaeocarpus (1e4), Artemisia (0.5e1%), Pteropsida (2e7%), Palmae (0.5e1%), Rosaceae (1e2%) and small smooth trilete spores (1%). Justicia is abundant (50e150%). Peridinioid cysts (1e4%) and Saeptodinium sp. (1e11%) are present. The palynofacies assemblages are characterised by declining inertinite (79e14%), and rising thermally mature (2e15%), plant cuticle and cell walls (5e27%) and fungal hyphae (4e27%). Characterised by declining Poaceae (78e15%) and rising Quercus (2e16%). Most samples contain Rubiaceae, Podocarpus, Cyperaceae, Pteropsida, and Justicia. Pollen preservation is poor at the top of the zone, where unidentifiable pollen rise to 57%. Peridinioid cysts are presenting most samples. The palynofacies assemblage includes common inertinite (20e46%), plus thermally mature amorphous (12e26%), thermally mature (0.5e22%), plant cuticle and cell walls (4e22%), amorphous (2e35%) and fungal hyphae (1e26%). Characterised by diverse assemblages with Lithocarpus (12e40%), Dodonea (3e7%), Cyperaceae (2e8%) and Combretocarpus (1e5%). Most samples contain Casuarina, Elaeocarpus, Gluta, Palmae indet. Areca, Rubiaceae, Rutaceae, Castanopsis, Chionanthus, Quercus, Sterculia, Poaceae and Pteropsida. Justicia is abundant. Algae are rare. Palynofacies assemblages are very variable, with significant pollen (0.5e83%), thermally mature amorphous (2e52%), plant cuticle and cell walls (2e22%) and thermally mature (7e10%). Characterised by diverse assemblages with (24e45%), Lithocarpus (4e6%), Dodonea (3e4%), Myrica (1e2%), Avicennia (1e3%) Aizoaceae (0.5e2%), Elaeocarpus (1e16%), Iguanura (1e4%), Rubiaeae (0.5e1%), Rutaceae (0.5%), Castanopsis (0.5e1%), Quercus (1e2%), Sterculia (0.5e1%), Cyperaceae (2e3%), Poaceae (1e2%) and Pteropsida (0.5e2%). Justicia and juvenile Palmae are extremely abundant. Algae are rare. The palynofacies assemblage contains mostly thermally mature amorphous (14e73%) and pollen (7e44%), with some thermally mature (6e12%), plant cuticle and cell walls (3e12%) and amorphous (2e13%). Characterised by diverse and very variable assemblages with Poaceae (5e15%), Cyperaceae (2e14%), Dodonea (0.5e28%), Podocarpus (0.5e4%) and Quercus (0.5e2%). Most samples contain Oleaceae, Alnus, Santiria, Elaeocarpus, Liliaceae, Polypodium type, Symplocos, Lithocarpus, Urticaceae, Kleinhovia, Ochnaceae, Asteraceae, Lactucae, Pteropsida and Rumex. Justicia is extremely abundant. Iguanura is abundant (24e42%) in two samples. Peridinioid cysts (1e24%) are present. The palynofacies is very variable, with pollen (12e84%), thermally mature amorphous (4e48%), inertinite (5e10%), thermally mature (4e23%), plant cuticle and cell walls (4e25%) and amorphous (0e15%) significant. Characterised by fairly diverse assemblages with high Poaceae (16e32%), Cyperaceae (10e44%), Podocarpus (2e8%) and Pteropsida (5e10%). Most samples contain Myrica, Urticaceae and Chenopodiaceae. Justicia is present in some samples. All samples contain algae, with two assemblage-types alternating, one consisting of Peridinioid cysts, Spirogyra and Botryococcus, and the other of Saeptodinium. The palynofacies includes generally high inertinite (4e52%), variable thermally mature amorphous (6e74%) and some thermally mature (7e28%), plant cuticle and cell walls (0e26%) and pollen (2e10%). Characterised by sparse and rather low diversity assemblages with Pteropsida (12e13%), Podocarpus (0e12%), Poaceae (0e16%) and Cyathaceae (4%). Justicia is present in one sample. Some assemblages contained no pollen. Algae are rare. The palynofacies assemblage contains generally abundant inertinite (12e47%), thermally mature (10e53%) and plant cuticle and cell walls (2e58%). Characterised by low diversity and rather variable assemblages with high Avicennia (20e28%), some Symplocos (3e32%), Poaceae (5e8%), and also Chionanthus (1%), Lithocarpus (2e4%), Cyperaceae (0.5e1.5%), Lactucae (0.5e1%) and Pteropsida (1%). Brownlowia is abundant (44%) in one sample. Algae are rare. The palynofacies is predominantly thermally mature (59e64%), with some inertinite (11e22%) and plant cuticle and cell walls (8e12%). Characterised by sparse, low diversity and rather variable assemblages with Symplocos (1e20%) and Podocarpus (1e7%). Most samples contain Oleaceae, Casuarina, Convolvulaceae, Avicennia, Elaeocarpus, Areca, Quercus, Albizia, Lactucae, Poaceae and Pteropsida. Justicia is present in one sample. Some assemblages contained no pollen. Algae are rare. The palynofacies is dominantly thermally mature (31e79%), with inertinite (10e46%) and plant cuticle and cell walls (4e15%).

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C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

Fig. 7. Palynology of the ‘Hell’ sequence (part 1). All taxa are shown as percentages of total pollen and spores excluding Justicia and juvenile pollen in monoliths 1e3.

taphonomy of this extremely fragile material is very localised. This material is typically derived from the heating of amorphous organic matter within sediments or soils below small surface fires. Spherules resulting from the burning of fatty or resinous material are also present at this level. The excavations in Hell Trench are far enough back in the photic zone of the cave mouth that no plants grow at this point and thus there is no local source of combustible material unless imported by people. Hence, if the dating framework suggested above is correct, there is evidence for human activity in the cave before GRIP Interstadial 13, at w50 ka. During H-3, fire in the landscape around the cave is indicated by the presence of frequent Justicia (Fig. 9) which today forms monospecific swards in the Niah Cave National Park following fire (K. Pearce, pers. comm. 2003). Albizia and Kleinhovia are also present in H-3 (Fig. 8), pointing to a disrupted forest canopy. At this point, there is little evidence for fire within the cave e the thermally mature amorphous counts are low (Fig. 10). In the Hell Trench pollen diagram, Justicia

regularly peaks during pollen zones characterised by high arboreal pollen counts, suggesting that fires coincided with episodes with dense forest. Although fire is common in the Borneo forests today (Goldammer and Seibert, 1989), much of this is anthropogenic: fire is today more commonly perceived to be associated with open savannah-like environments rather than with tropical forests. It is possible that the Justicia curve may reflect biomass burning, most likely to maintain open areas for hunting or to maintain forest-edge habitats which are rich in accessible wild foods (E. Kerui, pers. comm. 2003). Biomass burning has been inferred from high charcoal flux during OIS 3 in Iryan Jaya, western Kalimantan and deep-sea cores across the region (e.g. Hope, 1998; van der Kaars et al., 2000; Turney et al., 2001; Haberle et al., 2001; Kershaw et al., 2002; Anshari et al., 2004; Hope et al., 2004; Thevenon et al., 2004). The lower part of the sequence is generally fairly rich in Calcium and Strontium (Figs. 4e6) and consistent with the input of limestone particles resulting from slow granular

Fig. 8. Palynology of the ‘Hell’ sequence (part 2). All taxa are shown as percentages of total pollen and spores excluding Justicia and juvenile pollen in monoliths 1e3.

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

1965

Fig. 9. Palynology of the ‘Hell’ sequence (part 4). All pollen are shown as percentages of total pollen and spores excluding Justicia and juvenile pollen, except Justicia, juvenile pollen and algae, which are calculated as percentages of total pollen and spores; monoliths 1e3.

disintegration of the cave rook and walls. The sudden, marked rise in calcimetry values at the start of H-5 at 163 cm probably reflects an increase in this influx, probably as the result of the fall and partial disintegration of part of the cave-entrance stalagmite curtain. Gilbertson et al. (2005) showed that this occurred during the accumulation of the Hell sequence. The correlation discussed above (Table 3) would suggest an age of w49.5 ka. The palynofacies (Fig. 10) shows distinct minima in thermally mature amorphous matter and thermally mature matter at 168 cm, but both rise at 163 cm, suggesting that if these curves reflect anthropogenic activity to any extent, the event had little impact on human use of the cave. The sediments continue to have high calcimetry values until 133 cm.

Thereafter, Calcium and calcimetry are low, suggesting that disintegration of the stalagmite entrance curtain had ceased. Most forest taxa expand in H-5 to H-7, including taxa typical of lowland, montane, coastal and swamp forest, although Podocarpus contracts (Fig. 8). This probably reflects a rise in rainfall and temperature relative to the previous biozones. Justicia goes through a series of expansions (Fig. 9), perhaps consistent with further biomass burning in response to afforestation. In H-6, Justicia and much palm pollen is immature and in clumps, suggesting derivation from fructifications introduced into the cave rather than the airfall taphonomic route is likely for most pollen in this sequence (Hunt and Rushworth, 2005a).

Fig. 10. Palynofacies analysis of the ‘Hell’ sequence. All organic particulates are shown as percentages of total palynofacies; monoliths 1e3.

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

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Table 4 Calibration of radiocarbon dates (using Fairbanks et al., 2005) Lab. No.

Radiocarbon age

Calendar age

Mean

Std dev

Mean

Std dev

Niah-311 Niah-310

41,800 42,600

800 670

45,497 46,196

695 624

Calibration version

Fairbanks0805 Fairbanks0805

Open ground taxa expand in H-8, mostly Poaceae and Cyperaceae, but also the psilate monolete fern spores (Fig. 8) which are produced by the ferns that colonise open areas today (COH, unpublished). Other groups decline. This could reflect a decline in rainfall and temperature. At the base of H-9 a very abrupt change in palynological assemblage composition and a sharp decline in numbers of pollen (Figs. 9 and 10) recovered per sample suggest a period of non-deposition and a change in sedimentary facies. H-9 and H-10 have very high mangrove pollen and high lowland forest percentages. In H-11, coastal taxa expand, mangroves remain high, while swamp forest taxa are rare. The most important mangrove species in H-9 to H-11 is Avicennia. Taphonomic study (Hunt and Rushworth, 2005a) shows that while pollen of the mangrove genus Sonneratia is brought into the Great Cave by vegetarian bats at the present day, Avicennia pollen is not transported into the cave, although it grows along the coast in some numbers. As a result it is argued that the high Avicennia in H-9 to H-11 reflects airfall deposition from nearby mangrove vegetation. Thus, H-9 to H-11 suggest warm, perhaps increasingly dry environments and a high sea stand. Justicia occurs at the base of H-10 and in H-11, perhaps consistent with further biomass burning. The number of algae per sample drops at the base of H-9 and the deeper water planktonic species (Peridinioid cysts and Saeptodinium) virtually disappear. The decline in numbers of pollen per unit sediment is likely to reflect an increase in the deposition of clastic material and thus the dilution of pollen, while the decline of algae in general and the deepwater planktonics in particular indicate shallower, perhaps more ephemeral discharges through the Hell area. Although the pollen assemblages suggest that it was relatively dry at this time, similar dry phases in H-2 to H-4 and H-8 were not accompanied by a similar shift in algae. The decline in algae and disappearance of the deepwater planktonics are thus most probably linked to a change in the hydrological regime inside the cave. A number of samples in H-9 to H-11 do not contain pollen and a few contain no organic matter. The properties of the sediment in the field and the magnetic susceptibility data suggest that the absence of organic materials in some samples may be the result of hot fires on the sediment surface causing the Table 5 Suggested provisional correlation of Hell Trench interstadials with GRIP interstadials, and estimated dates Hell Trench pollen zones

GRIP interstadial

Estimated age (GRIP years/Cal. BP)

H-9 to H-11 H-5 to H-7 H-1

12 13 14

45,000e48,000 49,000e50,000 52,000e55,000

oxidation of surface and subsurface organic matter and this may explain the decline of thermally mature amorphous matter in H-9. It is possible that the sediment surface in the ‘Hell’ area became more attractive to people because it was drier and less often flooded as a result of the hydrological changes suggested above. H-9 to H-11 contain many siliceous microfossils e diatoms and phytoliths. Diatoms from this part of the section include a variety of estuarine species, including Diploneis spp. (Sarah Davies, pers. comm. 2005). The near approach of estuarine waters seems to have enabled the diatoms to be introduced into the cave by wind, people or animals. Such biological transport might be on elements of mangrove flora or fauna encrusted with diatoms, or in fauna containing the diatoms in gut contents, or on the feet or bodies of people or animals who had been moving about on estuarine mud. The phytoliths are probably the result of the import and burning of wood and other vegetable matter in the cave (L. Kealhofer, pers. comm. 2005) and are thus consistent with the other evidence of frequent fire discussed above. 7.3. Human activity The palynofacies analyses, with thermally mature amorphous matter through most of the sequence, suggest the presence of fire and resultant scorching of the sediments within the cave and thus (with the concurrent archaeological evidence) that humans were present virtually from the initiation of deposition at this site, tentatively suggested to be w52 ka. The date is as early as humans are reported in well-dated contexts anywhere else in Island SE Asia or Australia. In this paper, in the absence of evidence to the contrary, and given the presence of the ‘‘Deep Skull’’ and other fragmentary human remains, we assume that this palaeoecological evidence is the result of anatomically modern humans, rather than Homo erectus or Homo floresiensis. It is impossible to be sure from the evidence discussed here precisely what people were doing in the cave other than making fires (see Barker et al., 2007, for further details of the archaeology), but it can be suggested from the palynofacies that the human activity became more intense in the cave after w47 ka. Despite the fact that the palaeoecological evidence at the site indicates that the climate, and consequently the regional vegetation, went through a series of very rapid and intense changes, the palynofacies indicators suggest that human presence was relatively uninterrupted at the Great Cave. This attests to the flexibility and adaptability e attributes of behavioural modernity e of the Niah people. These findings also suggest that palynofacies analysis may have a key role in the investigation of caves where there is only sparse evidence for human activity as evidenced by more conventional methodologies. Deliberate biomass burning may be indicated by the coincidence of abundant Justicia pollen with forest phases. This first happens in H-3, shortly after the first convincing signs of human presence w50 ka, and close to the time that biomass burning is first reported in Indonesia and Australia (Kershaw

C.O. Hunt et al. / Journal of Archaeological Science 34 (2007) 1953e1969

et al., 2002, 2003; Thevenon et al., 2004) and but earlier than western Kalimantan (Anshari et al., 2004). Justicia then recurs again in H-5 to H-7 (w49e48 ka), and again, to a small amount in H-10 (w47 ka). This may point directly to people controlling their environment by creating resource-rich forest-marginal and regenerating environments during times of high forest. These observations must, however, be treated cautiously until corroborated by other lines of evidence, particularly as natural fires are held to be part of Bornean ecosystems today (Goldammer and Seibert, 1989). These finding also offer a local resolution of anthropological debates concerning the ability of Pleistocene foragers to find sufficient protein within wet tropical forested environments (Bailey et al., 1989; Townsend, 1990; Bailey and Headland, 1991; Dentan, 1991). In brief, the adjacent landscape was sometimes forested e giving rise to the palaeontological evidence for forest (Cranbrook, 2000) e at other times savannah-like vegetation was prevalent. But people at Niah may also have already developed strategies to cope with forest growth by biomass burning. Likewise, considerations of human dispersal in the region take on a new perspective with the demonstration of episodes characterised by significant areas of open vegetation, through which movement would not have been arduous. The spatial details and precise chronology of the shifting landscape mosaic during the Late Pleistocene still require exploration, however. 8. Conclusion This paper has integrated several proxies which provide evidence for a series of significant shifts in the character of the vegetation adjacent to the Great Cave of Niah during part of OIS 3. These shifts reflect the impact of climatic, vegetational, sea-level and human influences. Radiocarbon ages anchor the upper part of the sequence at w45e46 ka cal BP. Correlation between local biotic signals and the GRIP sequence (Dansgaard et al., 1993) suggests the studied sequence may extend to w52 ka. The sequence is, however, discontinuous: it is possible therefore that the base is older than a simple count from the top would suggest. Northern Borneo has been suggested as a major refugium for tropical rainforest during the Late Pleistocene. This paper shows that lowland rainforest species occurred only episodically at this location during OIS 3. This finding is compatible with the earlier conclusions of Cranbrook (2000). The biogeographical results of Gathorne-Hardy et al. (2002) are perhaps explained by the retention of closed forest on the higher parts of the island, for instance on Mount Kinabalu, which would have had orographic rainfall even during drier episodes. This research suggests a more complex and dynamic local biogeography than envisioned previously for northern Sarawak during the Late Pleistocene. The Niah area was cyclically dominated by lowland forest, montane forest, and open savannah-like vegetation. These indicate combinations of lower temperatures and much reduced precipitation compared with the present day. The data presented here offer support for the savannah corridor hypothesis of Bird et al. (2005) for the

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dispersal of the earliest modern people in the region. Biomass burning may have taken place during more forest-rich phases and therefore people were not necessarily foraging under closed canopy high forest. The first palynofacies evidence for people in the entrance to the Great Cave at Niah is during a savannah phase, tentatively dated to w50 ka. Thereafter, people seem to have maintained a more-or-less consistent presence at Niah. Acknowledgments We thank the Chief Minister’s Department of Sarawak for permission to undertake the fieldwork at Niah, and the staff of Sarawak Museum, especially its Director Sanib Said and Assistant Director Ipoi Datan, for their support and encouragement. Reconnaissance by DG during 1999 in the Niah Caves was funded by the British Academy’s Committee for Southeast Asian Studies and the University of Adelaide through a Visiting Fellowship; all later work is indebted to the successful outcome of an AHRB grant proposal led by Graeme Barker. This paper draws on the research of the many scholars collaborating in the Niah Cave Project, published in the Sarawak Museum Journal and the project related papers. Their help and contributions are gratefully acknowledged, especially those of the project’s coordinator Graeme Barker; the excavation director Tim Reynolds; DG is the co-ordinator of palaeoenvironmental research. Dr J. Grattan kindly provided ICPMS results and discussion. A constructive review by J.G. Knox and helpful comments by Prof J. Rose and two anonymous referees are gratefully acknowledged. This is NCP contribution no. 34. References Anderson, D.D., 1997. Cave archaeology in Southeast Asia. Geoarchaeology 12 (6), 607e638. Anderson, J.A.R., Muller, J., 1975. Palynological study of a Holocene Peat and a Miocene Coal deposit from NW Borneo. Review of Palaeobotany and Palynology 19, 291e351. Anshari, G., Kershaw, A.P., van der Kaars, S., Jacobsen, G., 2004. Environmental change and peatland forest dynamics in the Lake Sentarum area, West Kalimantan. Indonesia Journal of Quaternary Science 19 (7), 637e655. Ashton, P.S., 1988. Manual of the Non-Dipterocarp Trees of Sarawak. Kuching, Forestry Department, Sarawak. Bailey, R.C., Headland, T.N., 1991. The tropical rainforest: is it a productive environment for human foragers? Human Ecology 19 (2), 261e285. Bailey, R.C., Head, G., Jenike, M., Owen, B., Reichtman, R., Zechenter, E., 1989. Hunting and gathering in tropical rainforest: is it possible? American Anthropologist 91, 59e82. Banda, R.M. 2001. The Nomenclature and Depositional History of the Miocene Coastal Sediment in Northwest Sarawak, Malaysia. Bull. 2, Jabatan Mineral dan Geosains. Barker, G., 2005. The archaeology of foraging and farming at Niah Cave, Sarawak. Asian Perspectives 44 (1), 90e106. Barker, G., Barton, H., Beavitt, P., Chapman, S., Derrick, M., Doherty, C., Farr, L., Gilb0ertson, D., Hunt, C., Jarvis, W., Krigbaum, J., Maloney, B., McLaren, S., Pettit, P., Pyatt, B., Reynolds, T., Rushworth, G., Stephens, M., 2000. The Niah Caves Project: preliminary report on the first (2000) season. Sarawak Museum Journal 55 (76), 111e149.

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