Late Devensian and Holocene relative sea‐level changes on the Isle of Skye,Scotland, UK

Detailed litho‐ and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the Isle of Skye, Scotland, UK, reveal evidence for several changes in relative sea level during the Late Devensian and Holocene. At the start of the record, relative sea level in the area was high at ca. 12 500 ¹⁴C (ca. 14 800 cal.) yr BP but then fell, reaching a low point during the Younger Dryas, at ca. 11 000–10 000 ¹⁴C (ca. 13 000–11 600 cal.) yr BP, when a rock platform, correlated with the Main Rock Platform, was formed. In the early–middle Holocene, relative sea level was rising by ca. 8000 ¹⁴C (ca. 8800 cal.) yr BP and in northeast Skye a lagoonal surface, correlated with the Main Postglacial Shoreline, was formed at ca. 6600 ¹⁴C (ca. 7500 cal.) yr BP. By the late Holocene, relative sea level was again falling, but a rise, registered at at least two sites, began probably before ca. 4000 ¹⁴C (ca. 4500 cal.) yr BP, and a second lagoonal surface in northeast Skye, correlated with the Blairdrummond Shoreline, was formed, although by ca. 3000 ¹⁴C (ca. 3200 cal.) yr BP relative sea level in the area had resumed its downward trend. The pattern of relative sea‐level changes disclosed is compared with evidence elsewhere in Scotland. Copyright © 2006 John Wiley & Sons, Ltd.     

Relative sea-level trends during the early–middle Holocene along the eastern coast of mainland Scotland, UK

Previously published radiocarbon-dated horizons relating to early and middle Holocene relative sea-level change along the eastern coast of mainland Scotland are examined and trends determined. The data are modified to ensure comparability and are compared against the pattern of glacio-isostatic uplift in the area. Results show that the rate of relative sea-level rise during the Main Postglacial Transgression in the middle Holocene becomes greater towards the edge of the uplifted area, whilst the age of the Main Postglacial Shoreline becomes younger in the same direction. Linear and quadratic regression analyses disclose trends which indicate that at the 0 m HWMOST isobase of the Main Postglacial Shoreline the rate of relative sea level rise between c. 8400 and c . 7000 14 C years BP ( c . 9500 to c . 7900 cal. BP) was 5-11 mm/radiocarbon year or 6-11 mm/calibrated year, whilst at the same isobase the Main Postglacial Shoreline was reached between 5500 and 6100 14 C years BP (between 6300 and 7000 cal. BP). The relative sea-level changes identified are compatible with a rising sea surface level offshore, which may have involved three episodes, possibly related to regional and wider deglaciation.     

Quaternary sea-level changes in Western Scotland

In recent years, major advances have been made in our understanding of Late Quaternary sea-level changes in western Scotland. In particular, new hypotheses have been advanced to explain the ages and origins of high-level rock platform fragments and high-level marine shell beds. Certain raised shorelines in Islay and Jura, SW Argyll and Wester Ross have been related to former margins of the last ice sheet and are associated with drops in the Lateglacial marine limit. In some areas the decline in Lateglacial sea-level took place in association with a stationary ice margin while in others the fall in sea-level occurred in conjunction with considerable ice retreat.During the Lateglacial Interstadial, relative sea-level fell rapidly between ca. 13 and ca. 12 ka BP and thereafter more slowly until ca. 11 ka BP. Renewed marine erosion during the cold climate of the Loch Lomond (Younger Dryas) Stadial (ca. 11-10 ka BP) resulted in the production of the Main Lateglacial Shoreline, which declines in altitude to the W, SW and S away from the centre of glacio-isostatic uplift in the W Highlands. The shoreline has a maximum altitude of 10–11 m O.D. in the Oban area and passes below sea-level in NE Islay, Ardnamurchan, Colonsay, W Mull, Kintyre and Arran.During the early Holocene a pronounced marine transgression took place, probably culminating between 6.6 and 7.0 ka BP. The culmination of the transgression is represented by the Main Postglacial Shoreline that reaches a maximum altitude of ca. 14 m in the Oban area and declines gently in altitude away from the centre of glacio-isostatic uplift. Reconstruction of the uplift isobases for this shoreline appears to indicate a slight eastward migration of the uplift centre since the Younger Dryas. In peripheral areas of western Scotland the Main Postglacial Shoreline is not present owing to the effect of Holocene submergence.     

Dendrochronologically dated changes in the limit of pine in northernmost Finland during the past 7.5 millennia

Postglacial changes in the occurrence of Scots pine in northernmost Finland and adjacent areas are indicated in data sets of megafossils dated to an accuracy of 1 year using analysis of tree rings. After adjustment for land uplift, results in the altitudinal and latitudinal extent and in the structure of the pine limit are compared in the context of megafossil and pollen evidence from Fennoscandia, the Kola Peninsula and Scotland. Temporal changes in tree density at the forest limit are estimated from chronology sample size. The record from the subregion of Enontekio shows a long-term retreat of pine, corresponding to summer cooling caused by orbital forcing. This long-term trend is superposed by shorter-term fluctuations, which is consistent with other proxy evidence of pine. An abrupt decline in the forest limit occurred during the first millennium BC in two major steps, with no indication of high-altitude pine germination between 800 BC and AD 100. The subregions of Inari and Utsjoki show significant fluctuations at the forest limit in tree density only.     

Early and Middle-Flandrian pollen zonation in the Eastern Highlands of Scotland

A review is presented of published data on Early and Middle-Flandrian pollen zones recorded at various sites in the Eastern Highlands of Scotland. This reveals a number of screpancies from site to site, particularly with regard to the position and timing both of the Pine expansion, and the Alnus- rise. On Deeside, Pine-Birch forests appear to have been established before the main expansion of Alder, which occurs on Upper Deeside in the period following 6700 B.P. On Speyside, evidence is conflicting, suggesting either that the arrival of Pine and Alder took place almost synchronously about 7000 B.P., or that, as on Deeside, Pine-Birch forest establishment preceded the main Alnus- rise, dated at Loch Garten at about 5900 B.P. In addition, the rate of immigration of Pine recorded at silcs of close proximily appears to vary quite markedly.
Evidence from two further Speyside diagrams confirms the second view, and also shows that a gradual expansion of Pinus values took place during the period 8000-6600 B.P., with the Alnus -risc delayed until 5500 B.P. Discrepancies in the records of Early and Middle-Flandrian pollen zones from site to site are then explained in terms of differential accumulation rates, and the theory that the phase of expansion of the Pine in the Eastern Highlands took place during a period of low or falling water-levels.     

Allt Odhar and Dalcharn: Two pre-Late Devensian/Late Weichselian sites in northern Scotland

The lithostratigraphy and biostratigraphy of two sites (Allt Odhar and Dalcharn) in north-central Scotland are described, where pollen spectra of temperate affinity have been obtained from organic deposits that underlie till. The pollen record from Allt Odhar, in association with evidence from plant macrofossils and Coleoptera, shows the expansion of birch woodland and its eventual replacement by open grassland under a climatic regime slightly cooler than that prevailing in the northern highlands of Scotland at the present day. The organic sediments accumulated during an Early Devensian interstadial episode, which has been dated by the uranium series disequilibrium method to ca. 106 ka BP. Evidence for one and possibly two Devensian glaciations may be preserved at the site. The pollen record from Dalcharn, by contrast, reflects the middle and later stages of an interglacial cycle with the transition from pine forest to grassland. The overlying till sequence contains evidence of at least two separate glacial episodes. The age of the warm stage cannot be established precisely on present evidence, but there are indications that it may predate the last (Ipswichian) interglacial. These are the first sites from the mainland of Scotland to provide evidence of wooded conditions during interstadial and interglacial episodes of the Middle/Late Pleistocene.     

Influence of Southern Upland ice on glacio-isostatic rebound in Scotland: the Main Rock Platform in the Firth of Clyde

This paper identifies an anomaly between the currently acccpted isobasc pattern for raised shorelines in Scotland. which is a simple ellipsoid centred over the Western Highlands, and current models for the morphology of the Late Devensian ice-sheet. which show a primary dome in the Western Highlands but a prominent secondary dome over the Southern Uplands. One explanation of this anomaly is that it is an artefact of inadequate shoreline data for south-west Scotland. To test this hypothesis, altitude data on the Main Rock Platform in the Firth of Clyde area have been collected and analysed. and demonstrate patterns that probably result from the influence of Southern Upland ice. The ice-sheet models in this area are therefore supported.     

Loch Lomond Stadial and Flandrian shorelines in the inner Moray Firth area,Scotland

Morphological mapping and stratigraphical investigations have identified surface and buried relict marine features in the inner Moray Firth area. The features consist of a buried gravel layer formed during the Loch Lomond Stadial, a buried beach of early Flandrian age, and surface beaches and estuarine flats of mid-late Flandrian age. Analysis of the altitudes of morphological features has identified two buried and five (possibly six) surface glacio-isostatically tilted raised shorelines. The steepest shoreline is associated with the buried gravel layer and slopes down towards N20°E at a gradient of 0.20m/km. Younger shorelines have lower gradients between 0.16–0.03m/km. The shoreline sequence combined with published data defines relative sea-level movements in the area during the last 11000 years. The inner Moray Firth shorelines are correlated with similar features in other areas of Scotland which include the Main Lateglacial, Main Buried and Main Postglacial Shorelines.     

Provenance and depositional environments of Quaternary sediments from the western North Sea Basin

As the majority of the data on Quaternary sediments from the North Sea Basin are seismostratigraphical, we analysed the Elsterian Swarte Bank Formation, the Late Saalian Fisher Formation and the Late Weichselian (Dimlington Stadial) Bolders Bank Formation in order to determine genesis and provenance. The Swarte Bank Formation is a subglacial till containing palynomorphs from the Moray Forth and the northeastern North Sea, and metamorphic heavy minerals from the Scottish Highlands. The Fisher Formation was sampled from the northern and central North Sea. In the north, it is interpreted as a subglacial till, with glaciomarine sediments cropping out further south. These sediments exhibit a provenance signature consistent with the Midland Valley of Scotland, the Eocene of the North Sea Basin, the Grampian Highlands and northeast Scotland. The Bolders Bank Formation is a subglacial till containing palynomorphs from the Midland Valley of Scotland, northern Britain, and a metamorphic heavy‐mineral suite indicative of the Grampian Highlands, Southern Uplands and northeast Scotland. These data demonstrate that there was repeated glaciation of the North Sea Basin during the Middle and Late Pleistocene, with ice sheets originating in northern Scotland. There was no evidence for a Scandinavian ice sheet in the western North Sea basin. Copyright © 2011 John Wiley & Sons, Ltd.     

Devensian organic interstadial deposits and ice sheet extent in Buchan,Scotland

Pre-Late Devensian organic deposits in the Buchan area of northeast Scotland were investigated for their geomorphological and palaeoecological (pollen, plant macrofossils, coleoptera) properties. Close ecological agreement exists between fossil indicators and allows the inference that the environment in the vicinity of the deposits was a dwarf shrub tundra of the type met today in high latitude areas of Scandinavia and arctic Russia. The latest in a series of radiocarbon dates from the site produced determinations beyond the limits of the method, although the geomorphological and fossil evidence appears to point to an interstadial date within Oxygen Isotope Stages 5a or 5c. The site has special significance for arguments concerning the much-debated concept of ‘Moraineless Buchan’; indeed, evidence is presented which supports the concept of extensive ice sheet glaciation during the Late Devensian for this crucial geographical area. If Buchan is to be seen as a further casualty amongst other disputed ice-free enclaves, then a return to earlier models of extensive ice sheet glaciation in the Late Devensian of Scotland would seem to be necessary. © 1998 John Wiley & Sons, Ltd.     

The Late Pleistocene Afton Lodge Clay Formation,Ayrshire, Scotland: evidence for Early to Middle Devensian climatic changes and Late Devensian onshore ice flow and rafting from the Firth of Clyde

An investigation into the late Pleistocene sediments exposed at Afton Lodge has helped to clarify the glacial history of western central Scotland. The sequence includes several allochthonous bodies of ‘shelly clay’ (Afton Lodge Clay Formation) associated with Late Devensian (Weichselian) age diamict. The shelly clay contains abundant marine macro- and microfauna, as well as palynomorphs consistent with its deposition within a shallow marine to estuarine environment. Faunal changes within the main body of marine clay record at least one, millennial-scale cycle of Arctic-Boreal, to Boreal, and back to Arctic-Boreal climatic conditions. A radiocarbon date of over 41 ka ¹⁴C BP obtained from the foraminifera indicates that the marine clays are older than the surrounding till. Afton Lodge is thus one of a suite of ‘high-level’ shelly clay occurrences around the Scottish coasts that are now considered to be glacially transported. Together with closely associated ‘shelly tills’, the rafts were emplaced during an early phase of the last glaciation by ice flowing from the western Grampian Highlands of Scotland through the topographically-confined Firth of Clyde basin. The blocks of marine sediment were detached subglacially, unfrozen, and carried at least 10 km by ice that splayed out onshore against reversed slopes favouring raft emplacement and the creation of closely associated ribbed moraine. Transport of the rafts was facilitated by water-lubricated décollement surfaces and their accretion was accompanied by dewatering. The shelly tills were formed mainly by the attenuation and crushing of rafts of shelly clay during their transport within the subglacial deforming bed.     

Dynamic landscape changes in Glen Roy and vicinity,west Highland Scotland,during the Younger Dryas and early Holocene: a synthesis

This paper introduces a special issue devoted to the sequence of events in and around Glen Roy during the Loch Lomond or Younger Dryas Stadial, the short but important cold period dated to between ∼12,900 and 11,700 years ago, during which glaciers last expanded to occupy the Scottish Highlands, and during the subsequent transition to warmer conditions at the start of the Holocene. The Glen Roy area is internationally famous for the ‘Parallel Roads’, pre-eminent examples of ice-dammed lake shorelines which were formed during the stadial. What makes these shorelines unique, however, is their role as distinctive time markers, allowing the order of formation of landforms and sediments to be construed with unprecedented detail. Varved lake sediments preserved within Glen Roy and nearby Loch Laggan provide a precise timescale – the Lochaber Master Varve Chronology (LMVC) – for establishing the rates and timing of some of the events. This introductory paper first sets the geological context for those new to this topic, with a digest of key advances in understanding made between the nineteenth century and the publication of the LMVC in 2010. It then summarises the evidence and ideas that have emerged from new research investigations reported in this special issue for the first time, and which shine new light on the subject. Two final sections synthesise the new data and consider future prospects for further refinement of the precise sequence and timing of events. A major conclusion to emerge from this new body of work is that the ice-dammed lakes, and the glaciers that impounded them, persisted in the area until around 11,700 to perhaps 11,600 years ago. This conflicts with recently promoted suggestions that the last glaciers in Scotland were already in a state of considerable decline by ∼12,500 years ago.     

Major late Caledonian and Hercynian shear movements on the Great Glen Fault

Synthesis of palaeomagnetic data from Ordovician-Devonian rock formations of North Scotland, involving “original” as well as overprinted magnetizations, has uncovered two major phases of transcurrent motion on the Great Glen Fault. It is inferred that the first of these displacements occurred in the late Middle Devonian and was of left-lateral character: it led to a minimum of 35° clockwise rotation of the Northern Highlands, corresponding to an offset of the order of 600 km along the Great Glen Fault. The second major movement took place during Hercynian time, amounting to c. 300 km in the dextral sense. The new reconfiguration of Scotland prior to the late Middle Devonian gives supporting evidence for late Proterozoic and Caledonian zonal correlations between the Central and Northern Highlands, as well as being compatible with various features of the Old Red Sandstone rocks of the Orcadian Basin. A recent proposal of a c. 2000 km sinistral offset along the Great Glen Fault in the Carboniferous is shown to be wrong, but the new evidence for superimposed offsets in opposite directions opens new perspectives for reconsidering megascale mid-late Palaeozoic displacements along the North Atlantic orogenic belt.     

Denudation history of the Southeastern Highlands of Australia

The low-relief summit plateaus (high plains) of the Southeastern Highlands are remnants of a widespread peneplain that was initially uplifted in the mid-Cretaceous and reached its current elevation in the Miocene–Pliocene. There are two mutually exclusive scenarios for the origin of the high plains: an uplifted peneplain originally formed by long-term denudation through the Mesozoic and late Paleozoic, contrasting with creation by ～1.5 km of erosion following the mid-Cretaceous uplift (based on fission track data). The hypothesis of a Mesozoic peneplain is consistent with the low relief of the high plains, the ca 200 Ma available to form the peneplain, and the pre-late Mesozoic oxygen-isotope composition of secondary kaolinites in weathering profiles on the high plains. If the ca 30 Ma cooling event recorded by the fission track data is due to ～1.5 km of denudation, then the high plains peneplain formed in the Late Cretaceous–early Paleogene, close to sea-level, and was uplifted in the early Paleogene, because evidence from basalts and fossil floras shows that the high plains surface was moderately elevated in the Eocene. This scenario is difficult to reconcile with the long-term erosion necessary to form such an extensive peneplain, the lack of sedimentary evidence for early Paleogene uplift, and the relatively small reduction in elevation (～250 m) that would have resulted from ～1.5 km of erosion (because the crust in this area is in isostatic equilibrium). Furthermore, extensive Cretaceous–early Paleogene denudation should have removed the pre-late Mesozoic secondary kaolinites present in weathering profiles in the highlands. There is no evidence that the Mesozoic peneplain was buried by kilometres of sediment and then exhumed in the Cretaceous–early Paleogene. I therefore conclude that the high plains of the Southeastern Highlands are the remnants of a Mesozoic peneplain uplifted in the mid-Cretaceous and again in the Miocene–Pliocene.     

A multi‐proxy record of changing environments from ca. 30 000 to 9000 cal. a BP: Onepoto maar palaeolake,Auckland, New Zealand

We present a high‐resolution record of lacustrine sedimentation spanning ca. 30 000 to 9000 cal. a BP from Onepoto maar, northern North Island, New Zealand. The multi‐proxy record of environmental change is constrained by tephrochronology and accelerator mass spectrometric ¹⁴C ages and provides evidence for episodes of rapid environmental change during the Last Glacial Coldest Period (LGCP) and Last Glacial–Interglacial Transition (LGIT) from northern New Zealand. The multi‐proxy palaeoenvironmental record from Onepoto indicates that the LGCP was cold, dry and windy in the Auckland region, with vegetation dominated by herb and grass in a beech forest mosaic between ca. 28 500 and 18 000 cal. a BP. The LGCP was accompanied by more frequent fires and influx of clastic sediment indicating increased erosion during the LGCP, with a mid‐LGCP interstadial identified between ca. 25 000 and 23 000 cal. a BP. Rapid climate amelioration at ca. 18 000 cal. a BP was accompanied by increased terrestrial biomass exemplified by the expansion of lowland podocarp forest, especially Dacrydium cupressinum. Increasing biomass production is reversed briefly by LGIT perturbations which are apparent in many of the proxies that span ca. 14 000–10 500 cal. a BP, suggesting generally increased wetness and higher in situ aquatic plant productivity with reduced terrestrial organic matter and terrigenous detrital influx. Furthermore, conditions at that time were probably warmer and frosts rare based on the increasing importance of Ascarina. The subsequent early Holocene is characterised by podocarp conifer forest and moist mild conditions. Postglacial sea‐level rise breached the crater rim and deposited 36 m of estuarine mud after ca. 9000 cal. a BP. Copyright © 2011 John Wiley & Sons, Ltd.     

Lateglacial and Holocene relative sea‐level changes and first evidence for the Storegga tsunami in Sutherland,Scotland

We reconstruct one of the longest relative sea‐level (RSL) records in north‐west Europe from the north coast of mainland Scotland, using data collected from three sites in Loch Eriboll (Sutherland) that we combine with other studies from the region. Following deglaciation, RSL fell from a Lateglacial highstand of +6?8 m OD (Ordnance Datum = ca. mean sea level) at ca. 15 k cal a BP to below present, then rose to an early Holocene highstand and remained at ca. +1 m OD between ca. 7 and 3 k cal a BP, before falling to present. We find no evidence for significant differential Holocene glacio‐isostatic adjustment between sites on the north‐west (Lochinver, Loch Laxford), north (Loch Eriboll) and north‐east (Wick) coast of mainland Scotland. This suggests that the region was rapidly deglaciated and there was little difference in ice loads across the region. From one site at the head of Loch Eriboll we report the most westerly sedimentary evidence for the early Holocene Storegga tsunami on the Scottish mainland. The presence of the Storegga tsunami in Loch Eriboll is predicted by a tsunami wave model, which suggests that the tsunami impacted the entire north coast of Scotland and probably also the Atlantic coastline of north‐west Scotland.

     

Lake George revisited: new evidence for the origin and evolution of a large closed lake,Southern Tablelands,NSW, Australia. 2: earliest Pleistocene (Gelasian) environments

The three sedimentary units infilling Lake George provide the longest quasi-continuous sedimentary record of any Australian lake basin. A combination of cosmogenic nuclide burial, magnetostratigraphy and biostratigraphic dating techniques previously has shown that the basal (fluvial) unit, the Gearys Gap Formation, began accumulating at ca 4 Ma, in the early Pliocene (Zanclean), and (ii) deposition had ceased by ca 3 Ma, in the mid-late Pliocene (Piacenzian). The same techniques confirm the middle unit, the (fluvio-lacustrine) Ondyong Point Formation began accumulating in the late Pliocene and deposition continued into the earliest Pleistocene (Gelasian) when a shallow but probably laterally extensive freshwater lake extended across the drillhole site. Our data provide a minimum Gelasian age for tectonic blockage of former spillway(s) and formation of paleo-Lake George. Whether this was the earliest lake to form within the basin is unknown, since the dated intervals are separated by a ferric hardpan, interpreted as representing a prolonged period of erosion or non-deposition. Temperate rainforest angiosperms including Nothofagus growing during the late Pliocene had been extirpated or become extinct during this interval, although a number of gymnosperms, now endemic to New Caledonia, New Guinea, New Zealand and Tasmania still survived in the otherwise sclerophyll-dominated vegetation. The succession of plant communities is considered to be due to effectively drier local conditions, which in turn reflect regional aridification during the Plio-Pleistocene transition, despite the formation of a freshwater lake across the basin. The sequence provides a reliable framework for recognising and correlating Plio-Pleistocene deposits elsewhere on the Southern Highlands.     

Scottish early Holocene vegetation dynamics based on pollen and tephra records from Inverlair and Loch Etteridge,Inverness-shire

This paper presents the results of an investigation of early Holocene cryptotephra layers recovered from sediments in two kettle-hole basins at Inverlair (Glen Spean) and Loch Etteridge (Glen Fernisdale). Electron probe micro-analysis (EPMA) of shards from two cryptotephra layers revealed that the uppermost layer in both sequences has a composition similar to the An Druim tephra, first reported from a site in Northern Scotland. We present evidence that distinguishes the An Druim from the chemically very similar early Holocene Ashik tephra. The lowermost layer at Inverlair matches the composition of the Askja-S tephra found in the Faroe Islands, Ireland, Sweden, Germany and Switzerland. This is the first published record of the Askja-S tephra from mainland Scotland. As at other sites, the Askja-S seems to mark a short-lived climatic deterioration, most likely the Pre-Boreal Oscillation: at Inverlair it occurs just above an oscillation represented by a reduction in LOI values and in the abundance of Betula pollen, and by a peak in Juniperus pollen. The lowermost layer at Loch Etteridge has a Katla-type chemistry and extends through the upper part of the Loch Lomond (Younger Dryas/GS-1) Stadial to the Stadial/Holocene transition; it may represent a composite layer which merges the Vedde and Abernethy tephras. One of the key conclusions is that the glacial-melt deposits in the vicinity of Inverlair (kames and kame terraces) were ice-free by c. 10.83 ka (the age of the Askja-S), providing a limiting age on the disappearance of LLR ice in Glen Spean.     

Vegetation and climates in southern Tasmania since the last glaciation

Enclosed basins (glacial and nonglacia) of Tasmania contain the most comprehensive record in Australia of trends in a regional vegetation and climate since the late Pleistocene. Seven pollen sequences, each continuous and extending back at least 10,000 years, are used to reconstruct the history of postglacial vegetation and climate in Southern Tasmania (42°S–43°30′S). Interpretations are supported by a study of the modern pollen rain. Postglacial climates in Tasmania were characterized by a strong west-to-east decrease in precipitation. During the late Pleistocene, climates were markedly colder and drier than at present, and the vegetation was largely devoid of trees. A major rise in temperature between ca. 11,500 and 9500 yr B.P., accompanied by rising effective precipitation, resulted in the expansion of Eucalyptus, then other trees, across Tasmania. This warming trend may have been temporarily reversed during the early postglacial. Dry climates delayed the development of forest in inland eastern Tasmania until after ca. 9500 yr B.P. There is no evidence for a major change in climate since this temperature rise. Two broad phases of development have occurred within the postglacial forests. The first was an early Holocene phase during which Nothofagus cunninghamii cool temperate rain forest developed in western Tasmania and on the slopes of mountains in central and southeastern Tasmania. Eucalyptus sclerophyll forests developed in eastern Tasmania and have remained dominant there since. By ca. 7800 yr B.P. rain-forest communities were established beyond present-day limits. The second phase was a mid to late Holocene phase during which forests and alpine vegetation became more open in structure, leading to the re-expansion of Eucalyptus and shade-intolerant species. During the early to mid Holocene, climates in Southern Tasmania were wetter and (? then) warmer than at present. Maximum and minimum dates for this “optimum” are 8000 and 5000 yr B.P. Since then, climates have become increasingly rigorous, possibly through an increased incidence of inequable “weather types” leading to an increase in the frequency of drought and frost. Structural changes in the postglacial vegetation of Southern Tasmania closely parallel those at equivalent latitudes in New Zealand and Chilean South America, hence are likely to reflect the same primary cause.