81 research outputs found
A record of late Quaternary environments at lunette-lakes Bolac and Turangmoroke, Western Victoria, Australia, based on pollen and a range of non-pollen palynomorphs
No full textA palaeoecological record from Lakes Bolac and Turangmoroke details the changing nature of vegetation patterns, lake levels and climate in the drier part of the Victorian Western Plains over approximately the last 90,000 years. In addition to the routine palynological proxies of pollen, spores and charcoal, a range of non-pollen palynomorphs (remains of algae, fungi, insects and other invertebrates) was analysed and described and provides useful additional information on the ecology of past vegetation communities. A chronology for the record is provided by radiocarbon and refined optical luminescence dating in the upper part of the sequence, and the latter technique is used to provide a timeframe for the period beyond the radiocarbon limit. The record shows that during marine isotope stage (MIS) 5.1 and mid MIS 3 the regional vegetation was composed of open woodland dominated by Allocasuarina luehmannii type with low numbers of Banksia, Eucalyptus and other Myrtaceae under which a diverse understorey developed. During these times Lake Turangmoroke held fresh water of varying depths. The degree of representation of MIS 4 and MIS 3 in the record is uncertain owing to discontinuities resulting from the lake having periodically dried. A change to open grassland-steppe occurred shortly after 47,000 years ago and lake levels fluctuated considerably before the lake became shallow and saline. Open grassland-steppe continued through MIS 2 with almost no trees present while the aquatic flora reflected further lake level declines and increasing salinity. Driest conditions, indicated by deflation of lake sediments during lunette building, occurred between similar to 18,000 and similar to 11,000 cal yr BP. Open woodland in the early Holocene was dominated by A. verticillata type until partial replacement by Eucalyptus around 7000-8000 (14)C yr BP when the vegetation cover present at European arrival was established. (c) 2008 Elsevier B.V. All rights reserved
Observed relationships between El Niño-Southern Oscillation, rainfall variability and vegetation and fire history on Halmahera, Maluku, Indonesia
No full textA temporally high-resolution palynological study of the uppermost section of core MD98-2180 from Kau Bay, Halmahera, Indonesia, provides a vegetation and fire record covering the last 250 years. The record is compared with the Maluku Rainfall Index, Southern Oscillation Index (SOI) and southern hemisphere winter sea surface temperatures (SST) for the central Pacific Ocean based on instrumental data, as well as reconstructions of the SOI and the central Pacific SST and historically recorded El Nino events. The results show that significant El Nino events are generally associated with increased representation of Dipterocarpaceae pollen, probably reflecting the mass-flowering of this taxon during El Nino-Southern Oscillation (ENSO) droughts, and elevated charcoal levels, reflecting a greater incidence of fires during these extremely dry periods, while humid phases show increased fern numbers. Our findings demonstrate that pollen records 'ecological' in scale can provide useful additional proxy records of ENSO events
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