K Kiernan

Glacial climates in the Antarctic region during the late Paleogene: Evidence from northwest Tasmania, Australia

Published data suggest that ice buildup commenced in Antarctica during the late middle Eocene. This predates by 30 m.y. the earliest evidence of Cenozoic glaciation on other fragments of Gondwana, although several of these were at high latitudes during the Paleogene. We provide new evidence for local glacier development during the late Paleogene in Tasmania, then a mountainous peninsula at about lat 55°-63°S projecting into the circum-Antarctic ocean. The date of glaciation is not precisely known, but an earliest Oligocene age is indicated. We suggest that episode may correlate with abrupt cooling of the sea surface surrounding Antarctica during the earliest Oligocene (36 Ma).

THE EXTENT OF LATE CENOZOIC GLACIATION IN THE CENTRAL HIGHLANDS OF TASMANIA, AUSTRALIA

It is argued that during the most extensive late Cenozoic glaciation of the Tasmanian Central Highlands an ice cap of ~ 6000 km2 developed, probably in the early Pleistocene or late Pilocene. At least three subsequent glaciations have occurred. During the late Last Glacial Stage smaller ice caps were present on the Central Plateau, on a number of smaller plateaus, and on the West Coast Range and other ranges. The more westerly glaciers displayed the highest rates of mass throughout. The ice masses were of temperate maritime character. It is not necessary to invoke any significant shift in the direction of snow-bearing winds to explain the pattern of glaciation when the ice was most extensive.

Glaciation and cave sediment aggradation around the margins of the Mt Field Plateau, Tasmania

Landform evolution around the Mt Field Plateau has been strongly influenced by multiple stages of cold glacial climate. Only small glaciers were present during the late Last Glacial or Global Isotope Stage 2, but degraded moraines and the distribution of erratics indicate that ice cover was more extensive earlier when ice and meltwater invaded neighbouring karst areas and meltwater streams deposited gravel in caves. Weathering evidence suggests a significant glacial advance during Global Isotope Stage 4. Uranium‐thorium dating of speleothems associated with gravels in proglacial caves suggests a major phase of gravel aggradation that post‐dates Global Isotope Stage 5 and pre‐dates Global Isotope Stage 2.

Relationship of cave fills to glaciation in the Nelson River Valley, Central Western Tasmania.

Glacial diversion of the Nelson River into a limestone floored valley promoted karst development. This diversion occurred prior to the Last Glacial Stage. Outwash gravels of pre-Last Glacial age are preserved within a meander cutoff cave and indicate cavern infilling and only minimal cave enlargement during the cold climatic stage. Equivocal evidence exists for human occupation of one cave immediately prior to the late Last Glacial Maximum, when mechanically weathered limestone fragments were precipitated onto the cave floor. Extensive erosion of the cave fills has occurred during postglacial time.

Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island

The geomorphology of Heard Island-McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava flows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene - Early Pliocene Drygalski Formation, which forms a 300m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, surficial sediments, and contemporary geomorphological processes, including glaciofluvial sediment flux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.

Deglaciation and weathering of Larsemann Hills, East Antarctica

Abstract In situ cosmogenic 10Be exposure dating, radiocarbon determinations, salt and sediment geochemistry, and rock weathering observations indicate that parts of Larsemann Hills, East Antarctica have been subaerially exposed throughout much of the last glacial cycle, with the last glaciation occurring prior to 100 ka bp. Salt-enhanced subaerial weathering, coupled with a paucity of glacial erratics, made exposure age dating challenging. Rapid subaerial surface lowering in some places means that some exposure ages may underestimate the true age of deglaciation. Despite this uncertainty, the data are consistent with the absence of overriding by a thick ice sheet during the Last Glacial Maximum ∼20–18 ka bp.

Advances in Quaternary studies in Tasmania

Abstract The last 35 years have seen rapid advances in our knowledge of climate change during the Quaternary Period in Tasmania. Extensive mapping and new dating studies, particularly since the advent of exposure dating, have revealed that maximum ice advance occurred 1 Ma ago and later advances were less extensive. Ice advances occurred several times during the last 100 ka, not only during the Last Glacial Maximum. Deglaciation was rapid after 18 ka and complete by 14 ka. Ice strongly affected limestone and produced extensive glaciokarst with deranged surface drainage. Glacial sediment plugged conduits to underground passages partially filled with glaciofluvial gravels. Periglacial erosion, and human impact since late oxygen isotope stage (OIS) 3, enhanced sediment influxes. New pollen records, particularly from Lake Selina, provide a 125 ka vegetation and climate record representative of the Southern Hemisphere. Finally, stable isotope studies of speleothem growth have revealed wide swings in climate. The climate was warm and moist during OIS 5e and early in OIS 1. Climate was cold and dry during OIS 5d and 4, and prevented speleothem growth during OIS 3 and OIS 2.

Hickmania Troglodytes, the Tasmanian Cave Spider, and its Potential Role in Cave Management

Cave faunas – which often contain a high representation of spiders – are subject to increasing pressure from the effects of epigean habitat degradation and recreational caving activities. Hickmania troglodytes is a prominent member of the Tasmanian cave fauna, a spider of phylogenetic, zoogeographic and ecological importance, but about which little has previously been known. Long-term monitoring has revealed many unusual life-cycle characteristics in this species, most of which occur over long periods of time and are dependent upon environmental stability. The species presents a potentially useful tool in the management and monitoring of cave fauna and karst, as it is large, conspicuous, numerous, ubiquitous, sedentary, functionally significant and potentially sensitive to various sources of disturbance. H. troglodytes may provide a visible and obvious measure of disturbance in and around cave entrances, and may also prove useful in detecting broader scale impacts affecting the entire cave. Many promising developments are being made in terms of cave management in Tasmania, but other issues are less well addressed and still need to be resolved. With further research, the use of indicator or sentinel species may prove to be well suited to the less complex and often sparsely populated subterranean environment, and may play an important role within larger management strategies for cave fauna and karst.

Glacial history of the upper Derwent Valley, Tasmania

Part of an extensive ice cap that developed in the Tasmanian Central Highlands during the late Cenozoic discharged southwards via a major outlet glacier that occupied the valley of the Derwent River. At least three and probably five phases of glaciation took place. The first and most extensive glaciation may have been early Pleistocene in age, while the most recent and least extensive occurred during the late Last Glacial Stage. When the ice cover was most extensive, the Derwent Glacier was up to 500 m thick. It may have extended to as low as 230 m above sea level, 70 km downvalley. Diffluent lobes of this glacier spread eastwards to merge with other glaciers in the Nive Valley, southwards into the upper Gordon Valley, and westwards into the upper Franklin and Alma Valleys. The ice masses of west-central Tasmania were mainly of temperate maritime character.

The Nature Conservation, Geotourism and Poverty Reduction Nexus in Developing Countries: A Case Study from the Lao PDR

Despite high geodiversity and biodiversity conservation values, scenic landscapes and parts of the Nam Ou Valley being perceived by western visitors as wilderness, there has been limited progress towards securing long-term protection of some of these attributes in nature conservation reserves. Higher priority has been given to economic development, partly in a bid to address endemic poverty that is the product of the area’s remoteness and its turbulent political and military history. However, unless nature conservation is properly integrated into programs intended to enhance economic and social development, the natural values of the area are placed at increasing risk, as are some tourism enterprises with potential to assist in poverty reduction. Tensions between meeting immediate economic needs through tourism versus environmental management consistent with the long-term sustainability of tourism highlight the inadequate attention accorded to geodiversity by overseas aid programs that have shaped the nature conservation agenda in Laos. Enhanced recognition of the significance of geodiversity and geoheritage is especially important for geotourism based on physical landforms including inherently vulnerable karst caves. Improved understanding of key environments to inform development and implementation of effective protective management strategies is essential to stem accelerating degradation of some key visitor attractions. Unless this occurs, local tourism will be unable to progress beyond what presently amounts to little more than rudimentary, unmanaged and destructive scenery mining and to mature into a sustainable industry that can nourish long-term economic and social development.