Tasmania: Archaeological and Palaeo-Ecological Perspectives

Article excerpt

Tasmania, at the south of the land-mass, experienced the Glacial Maximum as a properly cold affair. Recent archaeological work, some in country now difficult of human access, has developed an intricate story of changing adaptations. At the Pleistocene-Holocene boundary, a major reorganization of Aboriginal adaptation strategies is seen in the archaeological record, argued to follow late-Pleistocene environmental amelioration.

In past 30 years, recorded Tasmanian human antiquity has increased from c. 8000 years to at least 35,000 years. Aboriginal adaptation to extremes of late Pleistocene climate (see Jones 1981) had to cope with rapid and unpredictable environmental changes, such as the transition from interstadial to full glacial conditions at about 25,000 b.p. (Isotope Stage 3 to 2), and the Pleistocene - Holocene transition, the subject of this volume. Both these periods are well represented in Tasmanian palaeo-ecological and geomorphological data.

Although archaeological evidence suggests that Tasmania was continuously occupied from c. 35,000 b.p. (Allen 1994; Cosgrove in press a), there is a major (although not complete) gap in the sequence between c. 13,000 and c. 10,000-8000 b.p. It reflects a combination of environmental factors (sea-level rise and stabilization, reforestation), and survey/excavation biases.

This paper reviews regional environmental and archaeological sequences through the Pleistocene-Holocene transition, concentrating on the period c. 17,000 to c. 7000 b.p.

The Tasmanian region and its zones

Tasmania and present-day Bass Strait form a natural region bounded in the north by the sill levels of the Bassian Rise and King Island/ Mornington Peninsula Basement Ridge, and in the west, east and south, by the Southern Ocean and Tasman Sea (Figure 1). Lowered late Pleistocene - early Holocene sea-levels exposed much of Bass Strait. Elsewhere around Tasmania, exposed areas of continental shelf were, in terms of land area, relatively insignificant (generally <30 km wide), because of steep coastal and submarine topography.

The region can be divided into several generalized environmental zones.

Western Tasmania is rugged, dominated by Precambrian and Palaeozoic geology, and today covered in wet temperate rainforest, button grass moorland, and to a lesser extent, wet eucalypt forest. The prevailing westerly winds, the roaring forties, which sweep the west coast and ranges, provide an annual average rainfall of 1200-3600 mm, and temperatures are cool to cold.

The east in contrast is drier (500-1200 mm), the result of a rainshadow effect; it is covered principally in dry sclerophyll forest, with an area of rainforest and wet eucalypt forest in the northeastern mountain region. A transitionary zone, dominated by wet eucalypt forest, occurs through central Tasmania where rainfall is within the range 1000-1400 mm.

Eastern islands such as those of the Furneaux Group are environmentally similar to coastal northeastern Tasmania, whilst King and Hunter Islands in west Bass Strait, are most similar to western, particularly northwestern, Tasmania.

Sea-level change and palaeogeography in

Bass Strait

Late Pleistocene sea-levels less than approximately -55 m created a land-bridge between northern Tasmania and the southeastern coast of mainland Australia. By using Chappell's (1983) sea-level curves, Blom (1988) finds the Bassian Rise may have been inundated c. 49-43,000 b.p., c. 41-37,000 b.p., and at c. 29,000 b.p., and at such times existed as a strait.

It is difficult to be precise about dates of inundation for various parts of Bass Strait. From c. 27-28,000 to c. 11,000 b.p., Tasmania was connected to mainland Australia. When sea-level was at its Last Glacial Maximum low of around minus 120-130 m, abroad plain was exposed, with an extensive Lake Bass, probably existing in its centre. …