The volcanic environment for 40,000 years of human occupation on the Willaumez Isthmus, West New Britain, Papua New Guinea
Introduction
The Willaumez Peninsula on the island of New Britain, Papua New Guinea (PNG), has a long history of Pleistocene and Holocene volcanic activity, much of which has recently come to light as a result of collaborative research among geologists, physicists, palaeobotanists, and archaeologists (e.g. Machida et al., 1996, Torrence et al., 1999, Torrence et al., 2000, Torrence et al., 2004a, Torrence et al., 2004b, McKee et al., 2005, Boyd et al., 2005, Jago and Boyd, 2005, Lentfer and Torrence, 2007). When integrated, these detailed analyses of stratigraphic records, microfossils, geomorphology, and ancient artefacts, provide an intriguing history of interaction between volcanic hazards and cultural responses. Despite the damaging impacts of volcanic eruptions, human societies have persisted in the region with remarkably few changes. The human history is characterised by local disappearances of populations as a consequence of volcanic activity, occasionally followed later by the introduction of new forms of cultural behaviour. Alongside this punctuated record, however, there is also evidence for long-term, gradual change, particularly in population levels and subsistence patterns (Torrence, 2002a, Torrence, 2002b, Torrence and Doelman, 2007). The aim of this paper is to illustrate the role of detailed stratigraphic studies of volcanic sequences in the assessment of how volcanic disasters have shaped human history. The major contributions of the lithological and mineralogical studies have been to provide the essential environmental background necessary for addressing questions about the sources and nature of the volcanic hazards and for assessing their varying impacts on resources important for the maintenance of cultural groups.
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Archaeological background
Archaeological research in Papua New Guinea is still in its infancy despite important new studies in the Bismarck Archipelago during the past 20 years (Spriggs, 1997). West New Britain province is unique because volcanic activity during the Pleistocene and Holocene has created a remarkable archaeological record consisting of multiple cultural horizons buried under volcanic tephras which blanket the central part of New Britain. These well preserved contexts span the entire c. 40 ka years of
Study area
New Britain is one of the most volcanically active areas in Papua New Guinea. It comprises part of the Bismark Volcanic Arc (Johnson, 1970) that stretches more than 1000 km along the southern margin of the Bismark Sea. The Arc is an active intra-oceanic subduction system formed where the Solomon Sea Plate in the east and the Australian Plate in the west descend northwards beneath the Bismark Plate. The Wadati–Benioff zone dips at about 70° beneath New Britain, with progressively deeper
Stratigraphy
The stratigraphy of the region is expressed in the two sections described below, beginning with the oldest beds and finishing with the Holocene sequence. The oldest beds are found at FABM (Fig. 3), where they are informally recognised in a sequence from A (oldest) to H (youngest). A detailed lithological description may be found in Torrence et al. (2004a). Briefly, the field appearance of the units moving progressively upwards in a section located in the middle of the hill is described below.
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Mineralogical studies
Whilst the macroscopic stratigraphic record provides an indication of the variable environmental conditions at a site, it does not provide details of provenance. For interpreting the nature of risk that the Pleistocene eruptions posed for human settlement in the wider region, it would be useful to know the source of the tephras at FABM. To this end a detailed mineralogical analysis of FABM was undertaken. Attribution of provenance is based on (1) grain shape (to separate material with a
History of impacts
The volcanic impacts represented at FABM can be usefully summarised in terms of 13 major episodes. After a brief description of how these might have impacted on human activities, we can place the events into several different categories that provide the basis for comparisons.
Beginning at the base of FABM, we have no information on any previous human presence prior to the deposition of Unit Upper A. The A beds, which are much more indurated than any succeeding units, represent the first episode
Comparisons of impacts
The impact of eruptions on the Willaumez isthmus can be grouped into three categories of severity.
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The most serious major plinian eruptions, represented by tephra beds Upper A, C, W-K1, W-K2, W-K3, & W-K4 (see also Boyd et al., 1999).
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The less serious subplinian eruptions (or distal plinian eruptions), represented by tephra beds D1, D2, Lower E, Dakataua, W-H4, and W-H5.
- 3.
The fine tephra beds which indicate long periods of tephra accretion, represented by units B1, Lower B, Upper B, Middle C, Upper
Human responses
The study of human responses to ancient volcanic activity in the Willaumez isthmus is the subject of ongoing research (Torrence and Doelman, 2007). One of the difficulties of interpreting the results of the archaeological and environmental analyses is the paucity of comparable data from nearby regions, with much less complete archaeological records. This makes it hard to track the movements of refugees following major volcanic events, and to distinguish to what extent changes in behaviour
Conclusions
The history of the Willaumez isthmus region, as represented by the stratigraphies at FABM and FAAH XVII, is reconstructed as a sequence of volcanic episodes separated by lengthy periods of quiescence. Throughout this long sequence there is abundant evidence for human settlement during the intervals between volcanic events. Variation in the scale of the volcanic events had a significant effect on cultural history. Volcanic episodes were either of short duration, i.e. plinian and subplinian
Acknowledgements
Funding was provided by the Australian Research Council, Australian Museum, AINSE, Pacific Biological Foundation, and New Britain Palm Oil, Ltd. We are also grateful to the following institutions in Papua New Guinea for their assistance: National Research Institute; National Museum and Art Gallery; University of PNG, West New Britain Provincial Cultural Centre; Kimbe Bay Shipping Agencies; Walindi Plantation; and Mahonia Na Dari Research Station. We thank the many volunteers who assisted in the
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2012, Quaternary InternationalCitation Excerpt :The social system indicated by the stemmed tools must have successfully integrated large groups of people, because it survived the W-K1 volcanic disaster that represents the first of a new series of particularly large plinian eruptions from the Witori and Dakatau volcanoes (Fig. 3; Table 1). These devastated large areas of the Willaumez Peninsula as well as the whole of central New Britain and forced the evacuation of both study regions (Machida et al., 1996; Torrence, 2002a; Torrence and Doelman, 2007; Neall et al., 2008; Torrence et al., 2009a). Stemmed tools disappeared after the W-K2 eruption at the same time that the first pottery was introduced to this region.
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2010, Quaternary Science ReviewsCitation Excerpt :The magnitude and impact of these eruptions ranged from minor events with restricted local impacts, to cataclysmic events with significant airfall and flow deposits that affected large areas and caused extensive landscape devastation close to the volcanic centres (Torrence and Doelman, 2007; Torrence, 2008; Torrence et al., 2009). At least eight eruptions are evidenced at archaeological sites in the study area, but the oldest four cannot be related to the older series recognised on Willaumez Peninsula (Neall et al., 2008; Torrence et al., 2009, table 1). Four later tephras can be confidently identified with major Holocene eruptions of Witori (the W-K series) (Table 1; Jackson, 1999).