Papers by Sean Fitzsimons
Quaternary Science Reviews, 1990
Four major Quaternary glaciations, with associated interglaciations and interstadials, have been ... more Four major Quaternary glaciations, with associated interglaciations and interstadials, have been identified in Tasmania, for which some chronological control is given by radiocarbon and amino-acid assays, pollen analysis and relative weathering characteristics. The glaciations are known as the Margaret, Henty, Moore and Linda.
Australian Journal of Earth Sciences, 1989
... (ii) Gravel dykes in non-calcareous bedrock are stream fills of eroded bedding planes, (iii) ... more ... (ii) Gravel dykes in non-calcareous bedrock are stream fills of eroded bedding planes, (iii) Gravel dykes in weathered limestone are filled dolines and solution ... READ KO 1963. The geology of the Princess River area. BSc (Hons) thesis, University of Tasmania, Hobart (unpubl.). ...
Boreas, 2008
Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests t... more Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests that the Early Pleistocene Thureau Formation is conformably overlain by the Regency Formation. Pollen analysis of the Regency Formation provides evidence of a new climatic stage, the Regency Interglacial. The interglacial deposit consists of humified peat overlain by drifted wood and leaves. The pollen analysis shows a transition from montane scrub rainforest to lowland temperate rainforest dominated by Lagarostrobos franklinii, Nothofagus cunninghamii and Phyllocladus aspleniifolius. Trace quantities of the species Quintinia psi-latispora and Gothanipollis perplexus, now both extinct in Tasmania, were also recorded. On the basis of intense chemical weathering and correlation with sediments that have a reversed magnetization the weathered glacial deposits of the Thureau Formation are thought to be older than 730,000 B.P. The eroded interglacial deposit rests on the weathered deposits and is buried by outwash gravels of the David Formation, which was deposited during an ice advance of the Middle Pleistocene Henty Glaciation (c. 150,000 B.P.). Comparison of the Regency site with a site 2 km to the south at Baxter Rivulet shows that the unconformity between the interglacial deposit and the overlying outwash gravel represents the erosion of the evidence for the Middle Pleistocene Moore Glaciation.
Antarctic Science, 1995
Studies of glacier margins have suggested that form and structure can be used to infer mass balan... more Studies of glacier margins have suggested that form and structure can be used to infer mass balance condition and stability. This paper examines this idea by investigating the form and structure of the Antarctic ice sheet at two coastal oases in East Antarctica. Two principal forms of the margin of the ice sheet in the Vestfold and Bunger hills that are discussed are ice cliffs and gently-sloping ice margins with an inner moraine. The form of the ice margins in both areas is primarily related to the accumulation of drift snow and superimposed ice and not to mass balance condition. It is concluded that the form and structure of ice margins are ambiguous indicators of mass balance condition and stability and that a change in mass budget is probably neither a sufficient nor a necessary condition for a change in the morphology of ice margins. Although we argue that the form and structure of the ice margins tells us little about stability, interpretation of the Holocene history and geomorphology of the oases suggests that the ice margins have been stable at least throughout the Holocene and that this condition of overall stability continues today.
Journal of Quaternary Science, 1990
Mapping, analysis and interpretation of glacigenic sediments in the King Valley, Tasmania has led... more Mapping, analysis and interpretation of glacigenic sediments in the King Valley, Tasmania has led to a revision of the Pleistocene stratigraphy of Tasmania. The sediments provide evidence of a glaciation that occurred between the Middle Pleistocene Henty Glaciation and the Early Pleistocene Linda Glaciation. The Moore Glaciation is estimated, on the basis of weathering rinds, amino-acid dating and palaeomagnetism to have occurred between 400000 and 550000 yrs BP. At Baxter Rivulet, sediments of the Moore Glaciation rest unconformably on highly weathered till and weathered Ordovician limestone and are overlain by outwash gravel of the Henty Glaciation. The Moore Glaciation sediments can be divided into four formations on the basis of lithology, organic content and degree of chemical weathering. The Huxley Formation (oldest) was deposited by an ice advance of the Mt. Jukes Glacier and is overlain by the Baxter Formation. The Baxter Formation consists of a bed of organic silty sand which records a cool non-forested flora of an interstadial period. The overlying Pyramid and Moore formations are outwash gravels from the Mt. Jukes and King Valley glaciers respectively. Though deposited during the same general ice advance, these two gravels were deposited at different times and show that the glaciers of the West Coast Range had spatially differentiated responses to climatic change.
Journal of Quaternary Science, 1991
Sediments spanning the last 30000 yr BP were obtained from two sections in the southern part of t... more Sediments spanning the last 30000 yr BP were obtained from two sections in the southern part of the Tengger Desert, northwestern China (38°10h 46i N, 102°45h 53i E). The pollen assemblage suggested a Picea forest domination under a wetter and cooler environment from 27580 to 23510 yr BP. During the following period from 23510 to 21880 yr BP a Cyperaceae meadow occurred under a wet and cold climate. Wetter and cooler conditions returned and a Picea forest re-occupied this region between 21880 and 20910 yr BP. From 20910 to 15590 yr BP a steppe under a dry environment dominated the region. The first temperature increase started at ca.15590 yr BP. The pollen assemblage covering the period between 15590 and 10890 yr BP can be divided into six minor zones, suggesting that the vegetation compositions changed rapidly under unstable climate. Between 10710 and 10370 yr BP the climate became cold and dry again. The climatic conditions became warmer and more humid between 10260 and 9140 yr BP. From 8450 to 7950 yr BP a steppe landscape under a dry climate occupied this region. Between 7950 and 7290 yr BP climate seemed more humid. The following period from 7290 to 5670 yr BP was generally warm. The period between 5670 and 3510 yr BP was characterized by dramatic climatic oscillations. Relatively cold intervals appeared around 7760 and 7380, 6490ü 6290, 5670ü5010, 4470ü3510 yr BP. Two pronounced dry events occurred in 6290ü5670 and 5010ü4470 yr BP with a marked wet spell from 3510 to 3000 yr BP.
Quaternary Research, 1991
Analysis of the geomorphology, geology, and palynology of deposits in the King Valley permits the... more Analysis of the geomorphology, geology, and palynology of deposits in the King Valley permits the identification of four glaciations and two interglaciations and has led to a revision of the Pleistocene stratigraphy of the West Coast Range. The oldest late-Cenozoic deposits in the valley appear to predate glaciation, contain extinct pollen types, and are probably of late-Tertiary age. Overlying deposits of the Linda Glaciation show intense chemical weathering and have a reversed detrital remanent magnetization indicating deposition before 730,000 yr B.P. The highly weathered tills are conformably overlain by organic deposits of the Regency Interglaciation which show a transition from montane scrub rainforest to lowland temperate rainforest.
Journal of Quaternary Science, 1991
Excavation of peat and clay filling a sink hole has provided a relatively long late glacial to Ho... more Excavation of peat and clay filling a sink hole has provided a relatively long late glacial to Holocene pollen/vegetation record for the King Valley. The record shows a change from alpine herbland, Microstrobos scrub and heath at 13 ka BP to Eucalyptus subalpine woodland. Phyllocladus-Nothofagus rainforest succeeded after 12.5 ka BP but degenerated to scrub rainforest after 11 ka BP, when Lagarostrobos franklinii expanded. The sequence of local changes occurred while the sink-hole lake was being rapidly infilled and converted to topogenous peat around 12 ka BP.Examination of the timing of changes in vegetation associations in other pollen profiles from different altitudes in western Tasmania indicates that many of the changes are non-synchronous and cannot be related directly to climatic events. They probably reflect the effects of both biological and local environmental factors.The major regional climatic change from alpine to temperate conditions on the lowlands occurred ca. 13 ka BP. Demonstration of non-synchronous changes in the late glacial to early Holocene pollen/vegetation associations at several sites contrasts with the view of Markgraf et al., who infer synchronous changes related to climate. There are no indications in the pollen/vegetation sequence of either Allerød or Younger Dryas events in western Tasmania.
Sedimentology, 1992
Quaternary sedimentary successions are described from the Linda Valley, a small valley in western... more Quaternary sedimentary successions are described from the Linda Valley, a small valley in western Tasmania that was dammed by ice during Early and Middle Pleistocene glaciations. Mapping and logging of exposures suggest that an orderly sequence of deposits formed during ice incursion, occupation and withdrawal from tributary valleys. Four principal sediment assemblages record different stages of ice occupation in the valley. As the glacier advanced, a proglacial, lacustrine sediment assemblage dominated by laminated silts and muds deposited from suspension accumulated in front of the glacier. A subglacial sediment assemblage consisting of deformed lacustrine deposits and lodgement till records the overriding of lake-bottom sediments as the glacier advanced up the valley into the proglacial lake. As the glacier withdrew from the valley, a supraglacial sediment assemblage of diamict, gravel, sand and silt facies formed on melting ice in the upper part of the valley. A lacustrine regression in the supraglacial assemblage is inferred on the basis of a change from deposits mainly resulting from suspension in a subaqueous setting to relatively thin and laterally discontinuous laminated sediments, occurrence of clastic dykes, and increasing complexity of the geometry of deposits that indicate deposition in a subaerial setting. A deltaic sediment assemblage deposited during the final stage of ice withdrawal from the valley consists of steeply dipping diamict and normally graded gravel facies formed on delta foresets by subaqueous sediment gravity flows. The sediment source for the delta, which prograded toward the retreating ice margin, was the supraglacial sediment assemblage previously deposited in the upper part of the valley. A depositional model developed from the study of the Linda Valley may be applicable to other alpine glaciated areas where glaciers flowed through or terminated in medium- to high-relief topography.
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Papers by Sean Fitzsimons