Previous Glaciations Research Articles

Luminescence dating of the MIS 6 glaciation of the Pamir mountains (Central Asia)

The Pamir Mountains are one of the highest mountain systems in the world; they act as sources of fresh water for the main rivers of Central Asia: the Amudaria and Syrdaria. Throughout the Quaternary, the Pamirs played a major role in controlling atmospheric circulation and land-surface processes, and provided great volumes of terrigenous sediments for transport by large rivers to the depressions in the Aral and Caspian regions. These ultimately provided broad aeolian cover in the sandy deserts, and finer dust for the widely distributed loess-palaeosol sequences. The glaciation history of this highly dynamic region provides an important basis for understanding climate change, sediment source and landscape evolution in Central Asia during the Quaternary. The question of the number, distribution, extent and timing of Pleistocene glaciations in the Pamir is debated. One of the main obstacles to research, together with difficulties of access and severity of current climate, is the varying degree of preservation of traces of previous glaciations in the western and eastern Pamir. As a result of a geological survey, we for the first time identified a thick lacustrine deposit at high altitudes in a tributary of the Panj – the valley of the Sary-Shitharv River – this records the damming of the Panj River valley by a large glacier. Luminescence measurements were undertaken to obtain the age of the Sary-Shitharv glacially-dammed lake. As often in mountain catchments the quartz OSL signal was unsuitable for dose estimation, and so the chronology of the Sary-Shitharv section is based entirely on post-IR IRSL signals from K-rich feldspar. We used pIRIR50,290 and pIRIR200,290 protocols and obtained indistinguishable ages from both protocols. Given the high sedimentation rates deduced from the structure of lacustrine deposits, the entire sequence must have been accumulated rather quickly, over a period of no more than a few thousand years. The average age over the whole series of dates is 165 ± 11 ka. This places the existence of the glacially-dammed lake at Sary-Shitharv in late MIS 6, a result that fits well with the general course of the glacial history of the Pamirs.

Discovery of a peculiar insular race of Ravenna nivea (Nire, 1920) (Lepidoptera: Lycaenidae) endemic to Yinggeling Mountain of Hainan, suggesting heterogeneous geological history of mountain formation of the island.

A peculiar population of Ravenna nivea (Nire, 1920) was discovered from the Yinggeling Mountain Mass of central Hainan. Its wing pattern and COI barcode data show considerable distinction from other geographic populations of R. nivea, including that of Bawangling, approximately only 40 km away and also located in Hainan. The p-distance value of the COI barcode between the Yinggeling and Bawangling populations was 1.1%, considerably higher than the value (0.6%) between Bawangling population and populations in eastern China, where the subspecific name howarthi Saigusa, 1993 applies. The population is regarded as a distinct subspecies ngiunmoiae Lo & Hsu, subsp. nov. The distinctness and high degree of COI haplotype diversity of R. nivea found in Hainan and Taiwan suggest continental islands may serve as glacial refugees for the butterfly and other organisms during previous glaciations, and the presence of the relict populations of montane butterflies like R. nivea may provide useful clues towards a better understanding of the geological history of mountain formation within islands.

Basal debris of the NEEM ice core, Greenland: a window into sub-ice-sheet geology, basal ice processes and ice-sheet oscillations

AbstractWe present new data from the debris-rich basal ice layers of the NEEM ice core (NW Greenland). Using mineralogical observations, SEM imagery, geochemical data from silicates (meteoric10Be, εNd,87Sr/86Sr) and organic material (C/N, δ13C), we characterize the source material, succession of previous glaciations and deglaciations and the paleoecological conditions during ice-free episodes. Meteoric10Be data and grain features indicate that the ice sheet interacted with paleosols and eroded fresh bedrock, leading to mixing in these debris-rich ice layers. Our analysis also identifies four successive stages in NW Greenland: (1) initial preglacial conditions, (2) glacial advance 1, (3) glacial retreat and interglacial conditions and (4) glacial advance 2 (current ice-sheet development). C/N and δ13C data suggest that deglacial environments favored the development of tundra and taiga ecosystems. These two successive glacial fluctuations observed at NEEM are consistent with those identified from the Camp Century core basal sediments over the last 3 Ma. Further inland, GRIP and GISP2 summit sites have remained glaciated more continuously than the western margin, with less intense ice-substratum interactions than those observed at NEEM.

Seventeenth Day of the Second Month

Historians consider the biblical account of the Deluge as a myth. However, this famous event occurred at the earliest times of recorded history (Sumerian King List). Today scientists believe in the last ice age called Pleistocene ending to 10,000 BCE, but there is no witness (prehistory) of this planetary cataclysmic event and its existence is based solely on the (controversial) interpretation of its consequences and their dating. The existence of erratic blocks and the disappearance of mammoths are presented as evidence of the last glaciation, but contrary to what one might think 14C dating provides conflicting results. Moreover, the sudden extinction of mammoths (some were found with food undigested in their stomachs or still unchewed in their teeth) would be spread over thousands of years! Likewise, during the last glaciation the sea level would have decreased by at least 140 m (which is currently explained by melting of glaciers) but such variations of the sea level did not occur during previous glaciations. Dating obtained by calibrated 14C is considered absolute by most experts but confrontation with the Egyptian chronology, which some dates are fixed by astronomy, reverses this belief. This comparison shows that dates obtained by 14C calibrated by dendrochronology match to those from astronomy until -2200 but before this date increase exponentially. Thus the rate of 14C tends gradually to 0 around -3500, which implies an important consequence: before that 14C dating is no longer possible. The biblical and Sumerian accounts of the Deluge are very similar (which occured in year 600 of Noah or Ziusudra) and suppose a dating around -3000 (3170 BCE according to the Septuagint). The period 3170-2800 is very poorly documented, the only remarkable event is the construction of the Tower of Babel then its abandonment and the emergence of languages. According to Mesopotamian literature the ziggurat of Babylon called "temple of the foundation of heaven and earth" in Sumerian was dedicated to Marduk. Many scholars estimate that these mythological texts have no historical value, but several Sumerian and Babylonian inscriptions have confirmed the antiquity of this ancient ziggurat and the name of its builder. Sumerian stories confirm the biblical version about four key points: 1) a universal deluge, 2) only one language at the origin, 3) construction of the Tower of Babel and 4) a sudden and simultaneous onset of languages (like Sumerian, Akkadian, Egyptian, etc.). Human longevity seems to have remained constant over the entire period from 3100 BCE up to now, which contradicts the biblical data concerning the relatives of Abraham who would have lived, prior 1600 BCE, much more than 130 years. However, contrary to the popular common sense suggests, human limits are difficult to set by science. Studies on human longevity provide amazing data in accordance with the Bible. Thus, for unexplained reasons, the maximum age at death (longevity) is not constant but increases regularly and since 1960 there is an unexplained acceleration of the increase. The transmission of many historical and chronological data (reigns, lifetimes, long periods, etc.) as well as many proper names, is necessarily flawed, unless one believing in an (unlikely) scribes infallibility. Thus, ancient texts, that are preserved in more than one copy, have been compared to determine how much variation occurs between manuscripts. This kind of study showed that the most stable texts surveyed are those containing ritual instructions, which have led, for example, to the exact transmission of the Torah in the late Second Temple period. The accuracy of the transmission of the text can be checked owing to the accuracy of its chronology and through the comparison between the sum of the intermediate values and the total value indicated in the text. Textual criticism now favors an anteriority of the Septuagint text Vorlage (H*) on the proto-Masoretic which comes from an overhaul of this Vorlage, including chronological data from the text of Genesis. According to the reconstruction of chronological data, Jewish corrections of the Hebrew text (preserved in the Septuagint) were performed in two steps: after the onset of the Book of Jubilees (c. -160) durations in Genesis 5:3-31 were reduced by 100 years and were adopted by a part of the Jews, as Eupolemus and by the Samaritans, and afterward, at the Synod of Yabneh (c. 90 CE), durations in Genesis 11:10-26 were also reduced by 100 years and were canonized by the rabbis (Pharisees). There was no dispute since the priests (Sadducees) no longer existed, as well as scrolls of the temple (except some of them which has been retrieved by Josephus thanks to emperor Titus in 70 CE).

Ice cap erosion patterns from bedrock 10Be and 26Al, southeastern Tibetan Plateau

AbstractQuantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ 10Be and 26Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km2 during pre‐LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in‐between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non‐erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd.

Refining the Laurentide Ice Sheet at Marine Isotope Stage 3: A data-based approach combining glacial isostatic simulations with a dynamic ice model

While glacial geologic records track the retreat history of the Laurentide Ice Sheet, constraints on the ice-sheet build-up history are more elusive. As the Laurentide Ice Sheet expanded to its maximum extent at the Last Glacial Maximum (26 ka), it erased most evidence of previous glaciations. However, an increasing number of dated, non-glacial deposits point to a relatively confined Laurentide Ice Sheet during Marine Isotope Stage 3 (MIS 3; 60-26 ka), suggesting rapid ice growth rates leading to the Last Glacial Maximum. In this study we demonstrate that predictions of relative sea-level change due to glacial isostatic adjustment involving a late and rapid growth of the Laurentide Ice Sheet are consistent with sea-level bounds associated non-glacial deposits of MIS 3 age in Canada. We also run a simple dynamic ice model that adopts the paleotopography generated from the glacial isostatic adjustment simulation and show that, using accumulation rates similar to that of the present-day Arctic, rapid glaciation rates starting at mid-MIS 3 (44 ka) are predicted.

Phylogeography, evolutionary history and effects of glaciations in a species (Zootoca vivipara) inhabiting multiple biogeographic regions

AbstractAimDuring glaciations, the distribution of temperate species inhabiting the Northern Hemisphere generally contracts into southern refugia; and in boreo‐alpine species of the Northern Hemisphere, expansion from Northern refugia is the general rule. Little is known about the drivers explaining vast distributions of species inhabiting multiple biogeographic regions (major biogeographic regions defined by the European Environmental Agency). Here we investigate the fine‐scale phylogeography and evolutionary history of the Eurasian common lizard (Zootoca vivipara), the terrestrial reptile with the world's widest and highest latitudinal distribution, that inhabits multiple biogeographic regions.LocationEurasia.MethodsWe generated the largest molecular dataset to date of Z. vivipara, ran phylogenetic analyses, reconstructed its evolutionary history, determined the location of glacial refuges and reconstructed ancestral biogeographic regions.ResultsThe phylogenetic analyses revealed a complex evolutionary history, driven by expansions and contractions of the distribution due to glacials and interglacials, and the colonization of new biogeographic regions by all lineages of Z. vivipara. Many glacial refugia were detected, most were located close to the southern limit of the Last Glacial Maximum. Two subclades recolonized large areas covered by permafrost during the last glaciation: namely, Western and Northern Europe and North‐Eastern Europe and Asia.Main conclusionsIn Z. vivipara, most of the glacial refugia were located in the South of their current distribution. Previous studies suggested the existence of Northern refuges, but the species' inability to overwinter on permafrost and the lack of genetic support suggest that the presence of a refugia in the north of the Alps is unlikely. This species currently inhabits boreo‐alpine climates and retracted during previous glaciations into southern refugia, as temperate species. Two clades exhibited enormous geographic expansion that started from two distinct glacial refugia. These phylogeographic patterns were highly congruent with those of Vipera berus. Together they suggest that glacial retraction, the location of the refugia and absence of competition may have promoted the enormous geographic expansion of two clades.

Cannabis is indigenous to Europe and cultivation began during the Copper or Bronze age: a probabilistic synthesis of fossil pollen studies

Conventional wisdom states Cannabis sativa originated in Asia and its dispersal to Europe depended upon human transport. Various Neolithic or Bronze age groups have been named as pioneer cultivators. These theses were tested by examining fossil pollen studies (FPSs), obtained from the European Pollen Database. Many FPSs report Cannabis or Humulus (C/H) with collective names (e.g. Cannabis/Humulus or Cannabaceae). To dissect these aggregate data, we used ecological proxies to differentiate C/H pollen, as follows: unknown C/H pollen that appeared in a pollen assemblage suggestive of steppe (Poaceae, Artemisia, Chenopodiaceae) we interpreted as wild-type Cannabis. C/H pollen in a mesophytic forest assemblage (Alnus, Salix, Populus) we interpreted as Humulus. C/H pollen curves that upsurged and appeared de novo alongside crop pollen grains we interpreted as cultivated hemp. FPSs were mapped and compared to the territories of archaeological cultures. We analysed 479 FPSs from the Holocene/Late Glacial, plus 36 FPSs from older strata. The results showed C/H pollen consistent with wild-type C. sativa in steppe and dry tundra landscapes throughout Europe during the early Holocene, Late Glacial, and previous glaciations. During the warm and wet Holocene Climactic Optimum, forests replaced steppe, and Humulus dominated. Cannabis retreated to steppe refugia. C/H pollen consistent with cultivated hemp first appeared in the Pontic-Caspian steppe refugium. GIS mapping linked cultivation with the Copper age Varna/Gumelniţa culture, and the Bronze age Yamnaya and Terramara cultures. An Iron age steppe culture, the Scythians, likely introduced hemp cultivation to Celtic and Proto-Slavic cultures.

Global biogeographic patterns in bipolar moss species.

A bipolar disjunction is an extreme, yet common, biogeographic pattern in non-vascular plants, yet its underlying mechanisms (vicariance or long-distance dispersal), origin and timing remain poorly understood. Here, combining a large-scale population dataset and multiple dating analyses, we examine the biogeography of four bipolar Polytrichales mosses, common to the Holarctic (temperate and polar Northern Hemisphere regions) and the Antarctic region (Antarctic, sub-Antarctic, southern South America) and other Southern Hemisphere (SH) regions. Our data reveal contrasting patterns, for three species were of Holarctic origin, with subsequent dispersal to the SH, while one, currently a particularly common species in the Holarctic (Polytrichum juniperinum), diversified in the Antarctic region and from here colonized both the Holarctic and other SH regions. Our findings suggest long-distance dispersal as the driver of bipolar disjunctions. We find such inter-hemispheric dispersals are rare, occurring on multi-million-year timescales. High-altitude tropical populations did not act as trans-equatorial ‘stepping-stones’, but rather were derived from later dispersal events. All arrivals to the Antarctic region occurred well before the Last Glacial Maximum and previous glaciations, suggesting that, despite the harsh climate during these past glacial maxima, plants have had a much longer presence in this southern region than previously thought.

The seafloor geomorphology of the Windmill Islands, Wilkes Land, East Antarctica: Evidence of Law Dome ice margin dynamics

A high-resolution multibeam sonar dataset covering an area of ca. 33km2 was collected in the vicinity of the Windmill Islands (67°S, 110°E), Wilkes Land, East Antarctica. The new data permit visualisation of the nearshore seafloor morphology in unprecedented detail, providing invaluable insight into the ice-sheet history of the region. A range of geomorphic features are evident, including prominent parallel northwest-trending linear fault sets affecting Mesoproterozoic metamorphic basement, which appear to control the regional coastal physiography. The fault systems probably formed during fragmentation of eastern Gondwana during the Mesozoic. Networks of sub-glacial meltwater channels, preserved on bedrock platforms and ridges, indicate grounding of a thick ice sheet over the continental shelf during previous glaciations. West-trending subtle glacial lineations and streamlined landforms record evidence of the westward expansion of the grounded Law Dome ice sheet margin, probably during the late Pleistocene. The direction of these features coincides with glacial striae on onshore crystalline bedrock outcrops. Perhaps the most striking glacial geomorphological features are sets of arcuate ridges confined mostly within glacially excavated U-shaped troughs formed by erosion of the northwest-trending bedrock fault sets. These ridge sets are interpreted as push moraines or grounding zone features, formed during episodic retreat of highly channelised, topographically-controlled ice-streams following ice surging of the Law Dome margin. This event was possibly triggered in response to local environmental forcing during the mid-late Holocene. Minor post-glacial marine sedimentation is preserved in several small (≤1km2) isolated basins with shallow seaward sills.

Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps

Abstract. What is the influence of glacial processes in driving erosion and uplift across the European Alps? It has largely been argued that repeated erosion and glaciation sustain isostatic uplift and topography in a decaying orogen. But some parts of the Alps may still be actively uplifting via deep lithospheric processes. We add insight to this debate by isolating the role of post-glacial topographic forcing on erosion rates. To do this, we quantify the topographic signature of past glaciation on millennial-scale erosion rates in previously glaciated and unglaciated catchments at the easternmost edge of the Austrian Alps. Newly measured catchment-wide erosion rates, determined from cosmogenic 10Be in river-borne quartz, correlate with basin relief and mean slope. GIS-derived slope–elevation and slope–area distributions across catchments provide clear topographic indicators of the degree of glacial preconditioning, which further correlates with erosion rates. Erosion rates in the easternmost, non-glaciated basins range from 40 to 150 mm ky−1 and likely reflect underlying tectonic forcings in this region, which have previously been attributed to recent (post 5 Ma) uplift. By contrast, erosion rates in previously glaciated catchments range from 170 to 240 mm ky−1 and reflect the erosional response to local topographic preconditioning by repeated glaciations. Together, these data suggest that Holocene erosion across the Eastern Alps is strongly shaped by the local topography relict from previous glaciations. Broader, landscape-wide forcings, such as the widely debated deep mantle-driven or isostatically driven uplift, result in lesser controls on both topography and erosion rates in this region. Comparing our data to previously published erosion rates across the Alps, we show that post-glacial erosion rates vary across more than 2 orders of magnitude. This high variation in post-glacial erosion may reflect combined effects of direct tectonic and modern climatic forcings but is strongly overprinted by past glacial climate and its topographic legacy.

The cosmopolitan moss Bryum argenteum in Antarctica: recent colonisation or in situ survival?

Since the onset of glaciation following the Oligocene (30–28 Ma), the prevalence of increasingly cold conditions has shaped the evolution of the Antarctic biota. Two hypotheses, postglacial recruitment from extra-regional locations and in situ persistence, have been proposed to explain the biogeography of the contemporary species-poor terrestrial Antarctic biota. Bryophytes, which form a major group of the Antarctic flora, exhibit a strong, inherent ability to survive cold conditions but also have high long-distance dispersal capacities, which are compatible with both hypotheses. Here, we test these hypotheses by means of population genetic and phylogeographic analyses of the cosmopolitan moss Bryum argenteum. We find evidence for at least three independent colonisation events of the species in Antarctica. Ancestral area reconstruction coupled with molecular dating suggests colonisation times of the different Antarctic clades ranging from four million years for the oldest lineage to half a million years for the youngest lineage. This suggests multiple colonisation events of Antarctica by this species during several glacial cycles within the Pleistocene, Pliocene and possibly late Miocene. This is the first study to demonstrate in situ persistence of bryophytes in Antarctica throughout previous glaciations.

Research history on glacial geomorphology and geochronology of the Cantabrian Mountains, north Iberia (43–42°N/7–2°W)

The study of glacial geomorphology in the Cantabrian Mountains, a mountain range that extends 460 km along the northern coast of the Iberian Peninsula (SW Europe), started late in the 19th century and continues nowadays with a growing number of research papers. However, the number and timing of glaciations remains poorly understood, partially due to the still limited number of numerical ages. Its southerly location and proximity to the Atlantic Ocean make this mountain range potentially sensitive to past climate fluctuations. This work updates the glacial knowledge evolution for the whole range, from the Queixa-Invernadoiro Massif to the Basque Mountains, reviewing: (i) the history of glacial research since the late 19th century; (ii) the methodological approaches applied to reconstruct both the spatial extent and timing of past glacial stages; and (iii) the main geomorphological and geochronological evidence reported until date, including glacial features attributed to the Last Glacial Cycle (last 120 ka) and previous glaciations. According to current knowledge, glaciers extended over the Cantabrian Mountains covering a total area of 3150 km2, showing asymmetric development conditioned by variations of the topographic configuration and moisture supply along the range. Available geochronology based on radiocarbon, optically stimulated luminescence and terrestrial cosmogenic nuclides suggests the occurrence of at least 2 glacial advances during the Last Glacial Cycle: (i) a glacial maximum stage that took place at a minimum age of 36–45 ka (Marine Isotope Stage 3) and (ii) a second glacial advance at 19–23 ka (MIS 2). In some areas the extent of the glacier tongues during the second glacial advance was comparable to previous glacial maximum and was followed by glacial retreat conditions with formation of recessional moraines. Asynchronous glacial maximum conditions have been reported only for the Castro Valnera (MIS 4, 3 numerical ages) and Queixa-Invernadoiro (MIS 6, 1 numerical age) massifs until now. Finally, geomorphological evidence reported in Picos de Europa has been attributed to prior glaciations and correlated to cold conditions recorded during MIS 12 and MIS 22 based on a very limited number of numerical ages.

Relating in situ hydraulic conductivity, particle size and relative density of superficial deposits in a heterogeneous catchment

Summary Estimating the permeability of superficial deposits is fundamental to many aspects of catchment science, but can be problematic where insufficient in situ measurements are available from pumping tests in piezometers. Consequently, common practice is to estimate permeability from the material description or, where available, particle size distribution using a formula such as Hazen. In this study, we examine the relationships between particle size, relative density and hydraulic conductivity in superficial deposits in Morayshire, Northern Scotland: a heterogeneous environment typical of many catchments subject to previous glaciations. The superficial deposits comprise glaciofluvial sands and gravels, glacial tills and moraines, raised marine sediments, and blown sands. Thirty-eight sites were investigated: hydraulic conductivity measurements were made using repeated Guelph permeameter measurements, cone resistance was measured in situ with a Panda dynamic cone penetrometer; material descriptions were made in accordance with BS5930:1999; and disturbed samples were taken for particle size analysis. Overall hydraulic conductivity ( K ) varied from 0.001 m/d to >40 m/d; glacial till had the lowest K (median 0.027 m/d) and glacial moraine the highest K (median 30 m/d). However, within each geological unit there was great variability in measured hydraulic conductivity values. Multiple linear regression of the data indicated that log d 10 and relative density (indicated by cone resistance or BS5930:1999 soil state description) were independent predictors of log K and together gave a relationship with an R 2 of 0.80. Material description using the largest fraction (e.g. sand or gravel) had little predictive power. Therefore, in heterogeneous catchments, the permeability of superficial deposits is most strongly related to the finest fraction ( d 10 ) and relative density of the material. In situ Guelph permeameter measurements at outcrops with good geological characterisation provide an easy and reliable method of determining the permeability of particular units of superficial deposits.

Late Pleistocene glaciation of the Mt Giluwe volcano, Papua New Guinea

The Mt Giluwe shield volcano was the largest area glaciated in Papua New Guinea during the Pleistocene. Despite minimal cooling of the sea surface during the last glacial maximum, glaciers reached elevations as low as 3200 m. To investigate changes in the extent of ice through time we have re-mapped evidence for glaciation on the southwest flank of Mt Giluwe. We find that an ice cap has formed on the flanks of the mountain on at least three, and probably four, separate occasions. To constrain the ages of these glaciations we present 39 new cosmogenic 36Cl exposure ages complemented by new radiocarbon dates. Direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought. In conjunction with existing potassium/argon and radiocarbon dating, we recognise four distinct glacial periods between 293–306 ka (Gogon Glaciation), 136–158 ka (Mengane Glaciation), centred at 62 ka (Komia Glaciation) and from >20.3–11.5 ka (Tongo Glaciation). The temperature difference relative to the present during the Tongo Glaciation is likely to be of the order of at least 5 °C which is a minimum difference for the previous glaciations. During the Tongo Glaciation, ice was briefly at its maximum for less than 1000 years, but stayed near maximum levels for nearly 4000 years, until about 15.4 ka. Over the next 4000 years there was more rapid retreat with ice free conditions by the early Holocene.

Antarctic terrestrial life – challenging the history of the frozen continent?

Antarctica is a continent locked in ice, with almost 99.7% of current terrain covered by permanent ice and snow, and clear evidence that, as recently as the Last Glacial Maximum (LGM), ice sheets were both thicker and much more extensive than they are now. Ice sheet modelling of both the LGM and estimated previous ice maxima across the continent give broad support to the concept that most if not all currently ice-free ground would have been overridden during previous glaciations. This has given rise to a widely held perception that all Mesozoic (pre-glacial) terrestrial life of Antarctica was wiped out by successive and deepening glacial events. The implicit conclusion of such destruction is that most, possibly all, contemporary terrestrial life has colonised the continent during subsequent periods of glacial retreat. However, several recently emerged and complementary strands of biological and geological research cannot be reconciled comfortably with the current reconstruction of Antarctic glacial history, and therefore provide a fundamental challenge to the existing paradigms. Here, we summarise and synthesise evidence across these lines of research. The emerging fundamental insights corroborate substantial elements of the contemporary Antarctic terrestrial biota being continuously isolated in situ on a multi-million year, even pre-Gondwana break-up timescale. This new and complex terrestrial Antarctic biogeography parallels recent work suggesting greater regionalisation and evolutionary isolation than previously suspected in the circum-Antarctic marine fauna. These findings both require the adoption of a new biological paradigm within Antarctica and challenge current understanding of Antarctic glacial history. This has major implications for our understanding of the key role of Antarctica in the Earth System.

SPATIAL INVENTORY OF LANDFORMS IN THE RECENTLY EXPOSED CENTRAL HIGHLAND OF SUB-ANTARCTIC MARION ISLAND

ABSTRACT Until recently, the Central Highland of sub-Antarctic Marion Island (above 750m a.s.l.) was covered by snow. Climatic amelioration is deemed responsible for the disappearance of the former permanent snowline which had a lower altitudinal limit of approximately 650m a.s.l. during the early-1950s. The recent sub-aerial exposure of this area now enables the geology and geomorphology to be documented. Mapping incorporated air-photo interpretation and field surveys using a hand-held Global Positioning System (GPS) to ensure spatial accuracy. Most grey lava outcrops above 750m a.s.l. exhibit some evidence of previous glaciations whereas black lava flows show no evidence of the effects of glaciers and must, therefore, post-date the Last Glacial Maximum (LGM). Frost processes currently predominate in the Central Highland, but there is a conspicuous lack of periglacial landforms (i.e. patterned ground) in scoria and grey lava areas. With the exception of thermal contraction cracking at one location, no other evidence for the development of geomorphological landforms in black lava areas exists. Other geomorphological landforms include meltout features, a manifestation of landscape process responses to climatic amelioration, mass movement landforms and the emergence of rudimentary aeolian landforms. Receding snow cover may enhance frost and aeolian processes, which could result in an interesting myriad of geomorphological landforms.

Late Quaternary Paleoceanography and Sedimentary Environments in Hudson Strait

Airgun and high resolution Huntec seismic reflection profiles are interpreted to show up to 130 m of glacial, glaciomarine and postglacial sediments overlying bedrock. In a basin at the eastern entrance to Hudson Strait most of the surficial sediment was deposited during the last déglaciation, but in western Hudson Strait multiple till sequences from previous glaciations are recognized. Five acoustic units were identified, at least three of which were penetrated with piston cores. Foraminifera of the stratigraphically deepest core in the eastern basin indicate a proximal glaciomarine environment and a likely presence of an ice shelf. A 14C date of 8060 ± 70 yBP (TO 750) on molluscan shells gives a minimum age for the top of the acoustically laminated distal glaciomarine sediments. The early postglacial foraminifera suggest a period of increased influence of offshore bottom waters restricted to the deep eastern basin. The surface sediments of all cores contain species indigenous of colder and fresher inshore waters of the present time. The ratio of 18CV16O in the benthic foraminifer Cibicides lobatulus is herein related to bottom salinity. Downcore measurements of 8'8O on C. lobatulus tests indicate bottom paleosalinities lower by about 0.5%o shortly before the dated horizon of 8000 yBP. By this time Hudson Strait was sufficiently clear of glacial ice for establishment of the present tidal regime. The lower bottom salinities indicate that tidal mixing took place between glacial meltwater leaving Hudson Bay and the offshore counterflow. This process is thought to have reduced the sharpness of the salinity difference between the offshore water and the surface plume of Laurentide meltwater as it entered the ocean.

Indirect climatic control of the clay mineral composition of Quaternary sediments from the Cariaco basin, northern Venezuela (ODP Site 1002)

Variations in the clay mineral composition of mid-late Quaternary sediments recovered from the Cariaco basin are interpreted in terms of changes in paleoclimate. The results indicate the changing contribution of regional and local sediment sources during interglacial high stands vs. glacial low stands. The relative contribution of illite increases during interglacial stages, and decreases during glacial stages. Illite–smectite shows a much weaker negative relationship to glacial eustacy. The abundances of kaolinite and chlorite show no correlation with paleoclimate. Sediments sourced from rivers adjacent to the Cariaco basin contain low illite and provide a significant influx of illite–smectite during low sea level stands, but during interglacial periods, they are probably deposited on the shallow continental shelf bordering the local coastline. Clays sourced from the Amazon and Orinoco rivers are richer in illite, and their contribution is reduced in times of low sea level stands, as the continental shelf becomes much narrower and sediment is discharged directly onto the continental rise. During the last glacial period, changes in clay mineral composition were magnified relative to previous glaciations, possibly due to tectonic evolution of the region. The sill depth between the Cariaco basin and the open Caribbean Sea was reduced to a minimum, decreasing further the relative importance of the Amazon/Orinoco contribution.

The glacial succession in lowland Northern England

Abstract The landscape of Northern England has been subjected to glacial activity several times during the Quaternary period. Successive ice sheets may have ‘swept clear’ the bedrock surface in places, but may also have incorporated materials from previous glaciations into later formations, and eventually into the present cover of glacial till. Hence, almost all the till materials now existing over Northern England were deposited during the last major ice sheet glaciation, which is known as the Late Devensian or Dimlington Stadial. These glacial tills are engineering soils, and the variable and often complex successions in which they occur have frequently led to problems on civil and mining engineering projects. Many theories have been proposed to explain the complex distribution and succession for the Late Devensian tills, which have involved the waxing and waning of the ice sheets, variations in the directions of ice flows, and other changes in the glacial and post-glacial environments. This paper attempts to summarize the published research and compare this with the authors' own experience and observations gained mainly from opencast coal mining operations in the exposed lowland coalfield areas of Cumbria, Northumberland, Tyne & Wear and County Durham. Finally, the implications for ground investigations, plus the design of stable excavations and other earthworks, are briefly discussed in the light of this experience.