The spatial configuration of the Antarctic ice sheet has fluctuated widely during the Late Quaternary, primarily in response to climate and sea-level forcings. Ice core time-series have long been used as proxy climate records for the Antarctic ice sheet surface and polar atmosphere, and there has been a major multinational effort to drill ice cores on or near the summit of ice domes to retrieve the longest possible records. The annual layering of ice accumulation has afforded high resolution proxy climate records on annual to decadal intervals, spanning a few hundred to hundreds of thousands of years. These time-series have also detailed the changes in the ice sheet surface elevation and dynamics, particularly since the transition from glacial to Holocene climate. However, ice sheet sensitivity to external forcings and the associated fluctuations in ice volume are probably best researched around the ice sheet's margins. The sedimentary record in these circumAntarctic margins holds the key to our unravelling of past and future responses of the Antarctic ice sheet and circumpolar oceans to climate and environmental change, including: fluctuations in ice volume; the distribution of ice shelves; the production of Antarctic bottom water; the variability in the fast ice and pack ice characteristics; biogeochemical cycling and marine productivity; and the evolutionary response of marine and terrestrial species and ecosystems.

This issue contains a group of papers selected from those presented at the 1st workshop of the SCAR-GLOCHANT and IGBP-PAGES cosponsored programme on the Late Quaternary Sedimentary Record of the Antarctic Ice Margin Evolution (ANTIME), held in Hobart, 6-1 1 July 1997. ANTIME is focused on the circurn Antarctic reconstruction of palaeoclimate, palaeoenvironment, and ice sheet palaeogeography throughout the last glacial cycle. There were 65 participants from Australia, USA, UK, Italy, Spain, Japan, Sweden, Germany and Russia at the workshop. The participants included representatives of PAGES, IMAGES, and INQUA. The workshop included three scientific sessions on:

1. Extent, timing and regional differences during Glacial Stage 2 (10–30 kyr BP) in Antarctica, from the terrestrial and marine records;

2. Climatic, environmental and glacial events during the Holocene;

3. Late Quaternary geochronological problems in Antarctica.

Over the past 15 years, Japanese, Australian and Russian expeditions to Prydz Bay have collected about 30 000 km of bathymetric data, 6000 km of sidescan sonar data and more than 250 sediment grab and core samples. These data were used in the present study to compile surficial sediment, bathymetric, and geomorphological maps of the Prydz Bay region. Lithofacies distribution was determined by surficial sediment data analysis using sample matrix (Q-mode) and cluster analysis techniques based on data from 206 sites. Data included percentage biogenic silica (opal), calcium carbonate, gravel, mud, and relative abundance of two diatom species (Fragilariopsis curta and F. kerguelensis). Five lithofacies are identified from the available data: (1) slightly gravelly sandy mud (g)sM lithofacies, (2) siliceous mud and diatom ooze (SMO) lithofacies, (3) F. kerguelensis pelagic ooze lithofacies, (4) F. curta gravelly muddy sand gmS lithofacies and (5) calcareous gravel lithofacies. In many areas the lithofacies correlate to geomorphological provinces as defined by previous investigators using 3.5 kHz and sidescan sonar data. In some cases, Holocene SMO sediments are seen to drape over iceberg plough marks, implying that these are relict features. These five lithofacies are likely to dominate most of the East Antarctic shelf region and may be helpful in defining sedimentary successions resulting from ice-sheet advance and retreat over glacial-interglacial cycles.

A marine survey in Prydz Bay, provides an unparalleled view of glacigenic and marine sedimentation across Prydz Channel and Amery Depression during the Late Quaternary. Gravity cores and a suite of eight radiocarbon dates indicate that the Late Wisconsin Glacial Maximum (LGM) was associated with grounding of a palaeo-ice shelf along the periphery of Prydz Channel. Deposition in front of the grounding line was dominated by ice-rafting. A granulated facies, containing angular clay and diamicton clasts, was producd by a combination of regelation freezing, near to the grounding line, and remelting of this basal debris in the sub-ice shelf setting. Beneath these LGM marine deposits lie two key beds of diatom ooze that are distinct in size sorting and Pliocene diatoms. These “interstadial” units can be traced across most of the Prydz Channel, and are underlain by additional glacial marine units. Debris related to the Lambert Deep is distinct from detritus from eastern Prydz Bay and deposition of these two sources within the channel oscillated during the LGM. We suggest that coastal drainage systems contributed to a limited glaciation of the shelf during the LGM, rather than direct outflow via the Lambert/Amery system. It is proposed that shelf-wide glaciation is related to the duration of glacial sea level lowstands rather than the absolute magnitude of eustatic fall during such episodes.

Stable isotope data from waters of lakes in the McMurdo Dry Valleys (MDV) of southern Victoria Land, Antarctica are presented in order to establish the climatic history of this region over the past two millennia. New data from Lake Fryxell and Lake Hoare in Toylor Valley, along with previously published data from Lake Vanda, Wright Valley and Lake Bonney, Taylor Valley are used to infer the recent climatic history of MDV. Lakes Vanda, Fryxell and Bonney appear to have lost their ice covers and evaporated to small, hypersaline ponds by 1000 to ~1200 yr BP. Lake Hoare either desiccated or did not exist prior to 1200 yr BP. These data indicate a major lowering of lake level prior to ~1000 yr BP, followed by a warmer and/or more humid climate since then.

Six abandoned colonies of Adélie penguin (Pygoscelis adeliae) were excavated near Palmer Station, Anvers Island, Antarctic Peninsula, to investigate the occupation history of this species. Sediments from each site yielded abundant fish bones and otoliths and squid beaks that represent prey remains deposited by penguins during the nesting period. Radiocarbon analyses indicate that colony occupation began prior to the Little Ice Age (LIA; 1500–1850 AD), with the oldest site dating to 644 yrs before present (BP; average reservoir-corrected date with Is range, 603–679 yr BP). Food remains indicate that the non-euphausiid prey of penguins consisted primarily of a mesopelagic squid (Psychroteuthis glacialis) and two species of fish (Pleuragramma antarcticun and Electrona antarctica). The relative abundance of the first two prey taxa varied significantly among six sites (X2>34.6; df = 10; P <0.001) with colonies dating prior to the LIA having greater representation of squid, and less of silverfish, than those occupied during the LIA. Data from control excavations at three modern colonies indicate a diet similar to that of the pre-LIA sites. These results suggest that Adélie penguins may have changed their diet in response to warming and cooling cycles in the past. In addition, only Adélie penguins are known to have nested in the Palmer Station area prior to the l950s; gentoo (Pygoscelis papua) and chinstrap (P. antarctica) penguins now breeding in this region have expanded their ranges southward in the Peninsula within the past 50 yrs, in correlation with pronounced regional warming.

Two gravity cores, Gebra-1 and Gebra-2 from the central and eastern basins of Bransfield Strait, West Antarctica, consist mainly of hemipelagic, laminated muds with black layers rich in sand-sized volcanic ash. Micropalaeontological (diatoms and radiolarians) and geochemical (organic and inorganic) analyses, together with radiometric dating (U/Th, 14C and 210Pb) have been performed on both cores. AMS analyses on Total Organic Carbon yielded a 14C-age older than expected, 2810 yr BP for the core top of Gebra-1 and 2596 yr BP for Gebra-2. The downcore pattern of ages indicates a sedimentation rate of 130 cm kyr1 for Gebra-1 and 160 cm kyr1 for Gebra-2 210Pb anomalies suggest the core top of Gebra-1 is present-day sediment. The diatom and radiolarian assemblages are related to the sequence of neoglacial events over the last three millennia. The recent significant reduction in Chaetoceros resting spores is interpreted as a reduction in palaeoproductivity. The progressive increase in sea-ice taxa for the last three millennia may indicate a cooling trend. Greater sea-ice coverage during the coldest neoglacial events in the Bransfield Basin, as well as in the Weddell Sea and Bellingshausen Sea, is documented by increases in sea-ice taxa and reductions in Thalassiosira antarctica/ T. scotia resting spores, Fragilariopsis kerguelensis, the Lithomelissa group and the “circumpolar” group of radiolarians. For these periods, we postulate a restricted communication between the Weddell Sea, Bellingshausen Sea and Bransfield basin. The millenial-scale changes are overprinted by a high frequency cyclicity at about 200–300 yrs, which might be related to the 200–yrs solar cycle.

On the continental rise west of the Antarctic Peninsula there are nine large mounds interpreted as sediment drifts, separated by turbidity current channels. Drift 7 is 150 km long, 70 km wide and up to 700 m high and is asymmetric, with steep sides on the south-east (towards the continent) and south-west, and gentle slopes to north-west and north-east. Cores on the gentle sides of the drift show a cyclicity between brown, bioturbated, diatom-bearing mud with foraminifera and radiolarians, and grey, laminated, barren mud. Biostratigraphic evidence is consistent with a Late Quatermary age. Detailed lithostratigraphy and magnetic susceptibility data allow precise correlation over distances of tens of kilometres. On the basis of chemostratigraphy, the brown sediment is interpreted as interglacial (isotope stages 1 and 5) and the grey as glacial (stages 2–4 and 6). Sedimentation rates are 3.0–5.5 cm ka-1. Cores on the steep sides of the drift recovered a condensed section with thinner cycles and hiatuses. Fine grain size, very poor sorting and the absence of a mode in the silt size range indicate deposition from suspension with only weak current activity. There is little evidence for cyclic changes in bottom current strength. Supply of sediment to the benthic nepheloid layer was by entrainment of mud from turbidity currents, and by setting of pelagic material (biogenic grains, IRD, sediment suspended in meltwater plumes). Cyclic changes in sediment supply include more biogenic supply in interglacials with less sea ice cover, more terrigenous supply from turbidites in glacials with ice sheets grounded to the shelf edge, and changes in IRD content

The Weddell Sea region arguably represents the largest unknown in quantifying the Antarctic contribution to the global water balance following the Last Glacial Maximum (LGM). This paper reviews the available onshore and offshore geological evidence constraining the volume of formerly expanded ice in the Weddell Sea embayment, focusing on the West Antarctic Ice Sheet (WAIS) and provides a preliminary reconstruction of the WAIS during the LGM. Dating control is generally poor and so our WAIS reconstruction is based on the assumption that the evidence of most recent ice sheet expansion dates to the LGM. Our reconstruction is intended to provide initial constraints with which glaciological models can be compared and shows grounded ice extent, flow directions, and ice surface elevations. Both marine and terrestrial geological evidence imply a substantial expansion of ice in the Weddell Sea embayment. Marine evidence shows that ice sheets were grounded in Crary Trough in the southern Weddell Sea and on the Antarctic Peninsula continental shelf during the LGM. Inland, the ice thickened by between 400 m (Ellsworth and Palmer Land) and 1900 m (Ellsworth Mountains). Ice core evidence suggests that the interior of the ice sheet remained the same or even thinned relative to present. The main unknowns now concern the exact location of the grounding line on some sectors of the shelf and the timing of ice sheet grounding and retreat. The limited radiocarbon data that exist on the eastern shelf indicates that the East Antarctic Ice Sheet retreated from the shelf prior to the LGM.

This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.