Climatic variability in the southwest Pacific during the Last Termination (20-10 kyr BP)

The degree to which palaeoclimatic changes in the Southern Hemisphere co-varied with events in the high latitude Northern Hemisphere during the Last Termination is a contentious issue, with conflicting evidence for the degree of 'teleconnection' between different regions of the Southern Hemisphere. The available hypotheses are difficult to test robustly, however, because there are few detailed palaeoclimatic records in the Southern Hemisphere. Here we present climatic reconstructions from the southwestern Pacific, a key region in the Southern Hemisphere because of the potentially important role it plays in global climate change. The reconstructions for the period 20-10 kyr BP were obtained from five sites along a transect from southern New Zealand, through Australia to Indonesia, supported by 125 calibrated C-14 ages. Two periods of significant climatic change can be identified across the region at around 17 and 14.2 cal kyr BP, most probably associated with the onset of warming in the West Pacific Warm Pool and the collapse of Antarctic ice during Meltwater Pulse-1A, respectively. The severe geochronological constraints that inherently afflict age models based on radiocarbon dating and the lack of quantified climatic parameters make more detailed interpretations problematic, however. There is an urgent need to address the geochronological limitations, and to develop more precise and quantified estimates of the pronounced climate variations that clearly affected this region during the Last Termination. (c) 2005 Elsevier Ltd. All rights reserved.

High-frequency winter cooling and reef coral mortality during the Holocene climatic optimum

A detailed ecological, micro-structural and skeletal Sr/Ca study of a 3.42 m thick Goniopora reef profile from an emerged Holocene reef terrace at the northern South China Sea reveals at least nine abrupt massive Goniopora stress and mortality events occurred in winter during the 7.0-7.5 thousand calendar years before present (cal. ka BP) (within the Holocene climatic optimum). Whilst calculated Sr/Ca-SST (sea surface temperature) maxima during this period are comparable to those in the 1990s, Sr/Ca-SST minima are significantly lower, probably due to stronger winter monsoons. Such generally cooler winters, superimposed by further exceptional winter cooling on inter-annual to decadal scales, may have caused stress and mortality of the corals about every 50 years. Sea level rose by similar to 3.42 m during this period, with present sea-level reached at similar to 7.3 ka BP and a sea-level highstand of at least similar to 1.8 m occurred at similar to 7.0 ka. The results show that it took about 20-25 years for a killed Goniopora coral reef to recover. (C) 2004 Elsevier B.V. All rights reserved.

Holocene depositional history of the Burdekin River delta of northeastern Australia: A model for a low-accommodation, highstand delta

The Burdekin River of northeastern Australia has constructed a substantial delta during the Holocene (delta plain area 1260 km2). The vertical succession through this delta comprises (1) a basal, coarse-grained transgressive lag overlying a continental omission surface, overlain by (2) a mud interval deposited as the coastal region was inundated by the postglacially rising sea, in turn overlain by (3) a generally sharp-based sand unit deposited principally in channel and mouth-bar environments with lesser volumes of floodplain and coastal facies. The Holocene Burdekin Delta was constructed as a series of at least thirteen discrete delta lobes, formed as the river avulsed. Each lobe consists of a composite sand body typically 5-8 m thick. The oldest lobes, formed during the latter stages of the postglacial sea-level rise (10-5.5 kyr BP), are larger than those formed during the highstand (5.5-3 kyr BP), which are in turn larger than those formed during the most recent slight sea-level lowering and stillstand (3-0 kyr BP). Radiocarbon ages and other stratigraphic data indicate that inter-avulsion period has decreased through time coincident with the decrease in delta lobe area. The primary control on Holocene delta architecture appears to have been a change from a pluvial climate known to characterize the region 12-4 kyr BP to the present drier, ENSO-dominated climate. In addition to decreasing the sediment supply via lower rates of chemical weathering, this change may have contributed to the shorter avulsion period by facilitating extreme variability of discharge. More frequent avulsion may also have been facilitated by the lengthening of the delta-plain channels as the system prograded seaward. Copyright © 2006, SEPM (Society for Sedimentary Geology).

A late Pleistocene predator-accumulated avifauna from Kids Cave, West Coast, South Island, New Zealand

A fossil deposit excavated from the floor of Kids Cave, West Coast, South Island, New Zealand, is interpreted as having been primarily accumulated by New Zealand falcon Falco novaeseelandiae, with some contribution by Haast's eagle Harpagornis moorei. The fauna is rich: 3699 bones represented 41 bird species, two frog species, unspecified geckoes and skinks, and one bat species. Fossil deposition was mainly within the Last Glacial Maximum from about 22,000 cal yr bp to about 15,000 cal yr bp, with a marked change in sediment characteristics at the onset of the LGM's coldest period. Chronological control is given by three Uranium-series dates for a speleothem and radiocarbon AMS dating of four avian eggshell samples and one bone. The fauna is the first extensive predator accumulation of LGM age described from the West Coast of the South Island, and it indicates a palaeoenvironment of a mosaic of shrublands with forest patches. The onset of the coldest part of the LGM (Aurora 3 glacial advance, 19,500 - 19,000 cal yrs bp) saw marked climate cooling/drying affecting the site, but the avifauna indicates that although open-country taxa became more common in this period, some forest persisted nearby throughout the remainder of the LGM.

Radiocarbon variations from the southern hemisphere, 10,350-9700 cal BP

We have made AMS measurements on a series of 10-ring samples from a subfossil Huon pine log found in western Tasmania (42degreesS, 145degreesE). The results show a pronounced rise in Delta(14)C over the first 200 years, and a decrease over the following 160 years. Tree-ring width measurements indicate that this log (catalogue SRT-447) can be cross-dated with another subfossil log (SRT-416) for which a series of high-precision radiometric C-14 measurements have previously been made. When the two tree-ring series are thus aligned, SRT-447 is the older of the two logs, and there is a 139-year overlap. We then have a Huon pine floating chronology spanning 680 years, with C-14 measurements attached. The C-14 data sets agree well within the period of overlap indicated by the tree-rings. The C-14 variations from Huon pine show excellent agreement with those from German oak and pine for the period 10,350-9670 cal BP. Aligning the Huon pine C-14 Series with that from German oak and pine allows us to examine the inter-hemispheric offset in C-14 dates in the early Holocene. (C) 2004 Elsevier B.V. All rights reserved.