Limit Of Glaciation Research Articles

GEMAS: Phosphorus in European agricultural soil - sources versus sinks at the continental-scale - the geological perspective

Phosphorus (P) is one of the essential elements for life on Earth. As a major nutrient it is needed for healthy growth both in plants and living organisms. Although the abundance of P in the Earth's upper continental crust is relatively high (655 mg/kg), many soil types are poor in available phosphorus. The main natural factors controlling the availability of P in soil are pH, mineralogy, and formation of insoluble complexes with Al and Fe under acidic, and with Ca and Mg under alkaline soil conditions. Superimposed weathering processes and climate contribute strongly to P mobility and availability. Additionally, a large fraction of total soil P is in organic forms, which are not directly available to plants. Phosphorus is a major component in fertilisers and thus a significant source of anthropogenic P in soil and water.In the agricultural soil samples that were collected during the Geochemical Mapping of Agricultural and grazing land Soil (GEMAS) project, the total P concentrations (XRF, median 786 m/kg) are only slightly higher than those extracted by hot aqua regia (AR, median 653 mg/kg), while the median concentration in the weak MMI® cold extraction is as low as 4.1 mg/kg. The AR results show very low P concentrations over the coarse-grained sandy sediments of the last glaciation in central and northern Europe and in calcareous soil. The southern limit of the last glaciation is visible as a concentration break on the geochemical maps. In general, north-eastern and north-western Europe are marked by high P values, probably related to cold and humid climate and enrichment in humus-rich coastal soil. The spatial distribution of P at the continental-scale is dominated by geogenic and climatic factors, and the anthropogenic influence is difficult to assess and quantify.

Rapid erosion along Holderness coast of East Yorkshire, UK and rising eustatic sea levels driven by climate change

Following the end of the last ice age, decelerating global post‐glacial sea level rises submerged the southern North Sea, and along this coast, 63 km of soft glacial deposits are still being rapidly washed away. The collapse of the massive ice sheets covering Britain, Ireland and Fennoscandia was a complex process, with warming after 14.7 ka. Limited glaciation then returned during the Loch Lomond Stadial at the end of the Pleistocene, Doggerland, connecting Britain with the continent, was slowly immersed, becoming a shrinking island which was rapidly submerged after 8 ka. This coincided with the Storegga tsunami which hit what remained of Doggerland’s shores and along the coasts of Scotland and Northumberland. Since then, the sea has risen by around 27.5 m. Now it is clear eustatic increases in global sea levels are starting to accelerate once again, we must start adjusting to this reality in the way we manage our coastal infrastructure and try to understand more about how this interacts with naturally dynamic shorelines.

Glacial Erratics from the Sea Floor South-East of the Faeroe Islands and the Limit of Glaciation

On the outer shelf and slope south-east of the Faeroe Islands down to 300 meters depth, 82 percent of the erratics consist of basalt and 14 percent of tuff carbonate sediments. At 400 to 700 meters depth these rock types only constitute 54 percent of the erratics, the rest being mainly sandstones and gneisses of distant origin. This sudden increase in the proportion of foreign erratics is probably caused by the front of the Faeroese ice sheet preventing ice-rafting over the shelf during the last glacial epoch.

Early and Middle Pleistocene glaciation of the southern Patagonian plain

Evidence of at least three Early to Middle Pleistocene glaciations is recorded in the stratigraphic exposures near the outer limit of glaciation in southern Patagonia. At Cabo Vírgenes, at the mouth of the Strait of Magellan, up to 70 m of till, gravel, sand, and stony silt were deposited in a grounding-line environment at the front of the Magellan lobe along a front several tens of kilometres wide. Accommodation space for the sediments was produced by glacio-isostatic depression resulting from the advance of the Magellan lobe to the Atlantic coast. At that time, the ‘moat’ in which the sediments accumulated may have been seaward of the modern Atlantic shoreline because the continental shelf is shallow and sea level was much lower than it is today. The sediments at Cabo Vírgenes are normally magnetized, carry no reversed overprints, and thus probably date to the Brunhes Chron (<0.774 Ma). Seacliff exposures south of the Strait of Magellan along the Atlantic coast of northern Tierra de Fuego expose two tills separated by glaciofluvial sediments. Although not dated, the tills record two advances of the Magellan lobe onto the Atlantic continental shelf. The location of the exposures relative to Cabo Vírgenes indicates that the upper of the two tills may correlate with the Cabo Vírgenes drift. The Tres de Enero highway cut, 90 km northwest of Cabo Vírgenes, exposes lodgement tills deposited during the Great Patagonian glaciation (GPG) – two stacked, normally magnetized tills overlie a reversely magnetized till. Truncated sand wedges separate each of the three tills, indicating that the tills record three separate Early to Middle Pleistocene glaciations. The younger of the two normally magnetized tills, and perhaps both, were deposited in the Brunhes Chron; the lowest, reversely magnetized till records extensive glaciation late during the Matuyama Chron (2.608–0.780 Ma). At Bella Vista in the Río Gallegos valley, a 0.89-Ma-old basalt flow caps a thick unit of normally magnetized glaciofluvial gravel, which was probably deposited during the Jaramillo Subchron (1.075–0.991 Ma), but certainly not later. Sediments at Tres de Enero and Bella Vista show that the GPG is not a single event as originally thought, but rather at least three glaciations, perhaps spanning several hundred thousand years.

A sedimentary record from the Makarov Basin, Arctic Ocean, reveals changing middle to Late Pleistocene glaciation patterns

Sediment core ARC5-ICE6 from the Makarov Basin was used to reconstruct circum-Arctic glaciation and surface-ocean circulation history for the Middle to Late Pleistocene, ∼0.5–0.7 Ma. Sedimentary proxies include elemental composition, coarse grain content, clay mineralogy, and radiogenic isotopes (Sr-Nd-Pb). Earlier studied records from the central Arctic Ocean were compared with ICE6 for a broader paleoceanographic context. Results indicate predominant sediment delivery from the Eurasian shelves and glaciated mainland with intermittent glacial inputs from North America. Low proxy variability prior to Marine Isotope Stage (MIS) 6 (∼0.2 Ma) suggests persistent sediment transport by sea ice via the Transpolar Drift and limited glaciation at the Eurasian margin. Since MIS 6, sediment inputs and provenance exhibit large shifts between glacial- and interglacial-type environments. The overall northern Eurasian Ice Sheet (EAIS) expansion was possibly related to climatic cooling and growth of a perennial sea ice in the Arctic Ocean. Provenance indicators from MIS 6, 5b and 4/3 reflect EAIS expansions followed by deglacial meltwater discharge from west Siberia. This provenance indicates a strong cyclonic circulation in the Arctic Ocean characterized by a significantly eastward-extended Transpolar Drift. Different glaciogenic sourcing and attendant circulation are proposed for several events within MIS 5 and 3, where proxies indicate increased sediment inputs from North America rather than Eurasian ice sheets. Overall limited glacial influence inferred for MIS 3 is consistent with relatively high sea level reconstructed for this interstadial. The Last Glacial Maximum is barely identifiable in the ICE6 record due to low glacial inputs and/or depositional hiatus.

Hydromorphologial assessment of the Vjosa river at the catchment scale linking glacial history and fluvial processes

Balkan rivers are described as hotspots of biodiversity due to the limited glaciation to a few high-altitude cirques during the last ice age. Although many studies have examined local-scale highlights in biota and biodiversity, an overall hydro-morphological characterization and development assessment of these rivers during the Holocene are missing. Aim of the presented study is to put together the present and recent river dynamics and Quaternary landscape development for a comprehensive understanding of geomorphic processes and the current river morphological characteristics of the Vjosa river. This was done by linking satellite imagery and hydro-dynamic modelling to read the landscape, i.e., to determine the development of landscape units, and (i) the active channel, (ii) the active floodplain and (iii) the morphological floodplain. The digital terrain of the Vjosa River catchment, as an example of the Balkan rivers, was based on a 25 m × 25 m digital elevation model, and hydrodynamic numerical analysis was conducted with a one-dimensional step-backwater model. The application of this assessment approach enabled a clear differentiation of four different sections along the longitudinal profile of the Vjosa—mainly differentiated by the slope and partially corresponding with the confluence of tributaries. We also found that periods of glaciation imposed a strong impact on the hydro-morphological characteristics of the Vjosa River. In particular, the delineation of the active channel and the active floodplain exhibited two different morphological reaches. The first reach exhibits a clear incision of the river into fluvial deposits when the historical sediment supply was high, and the second reach occurs downstream where the current sediment supply is equal or higher than that during the Pleistocene or earlier periods. These differences in hydro-morphological development exert a strong impact on the floodplain development and the human use of these reaches. Thus, despite the given uncertainties due to the lack of bathymetric accuracy, the hybrid assessment approach is useful for the hydro-morphological characterization of the Vjosa river and the identification of landscape forming processes on the catchment scale.

Possible new evidence for Mid-Pleistocene glaciation in the Vale of Pickering, North Yorkshire, UK

Whilst the Late Devensian glaciation (MIS2) of the Vale of Pickering is well-documented, earlier glaciations within it are not. A proposed limited glaciation in the Mid-Pleistocene, thought to be of Marine Isotope Stage 8 (MIS) age is not well constrained. This paper aims to obtain preliminary ages for two of the most prominent geomorphic features in the Vale of Pickering to see if they related to pre-Devensian glaciations. New luminescence dating by infra-red stimulation of feldspars from sand accumulations near the summit of Gallows Hill, part of the Wykeham Moraine, and from a section through poorly sorted fluvial sand and gravel on the flanks of the Hutton Buscel Terrace in Yedman Dale gave ages of 176 ± 14 ka and 156 ± 12 ka, respectively. Evidence suggests they represent a glacial incursion (MIS 6) into the Vale of Pickering blocking its eastern end and forming a pre-Devensian Glacial Lake Pickering. Whilst they could be older, this style of glaciation is very different to the limited plateau ice-field proposed for MIS 8 at the western end of the Vale of Pickering. Taken at face value, these preliminary ages suggest that the Vale of Pickering was partially glaciated in MIS 6 as part of a wider ice sheet and contemporary with the Saalian glaciation in Europe.

Reconstruction of pre-Illinoian ice margins and glaciotectonic structures from airborne ElectroMagnetic (AEM) surveys at the western limit of Laurentide glaciation, Midcontinent U.S.A.

Early and early Middle Pleistocene glaciations in midcontinental USA are poorly understood relative to more recent Illinoian and Wisconsinan glaciations, largely because pre-Illinoian glacial landforms and deposits are eroded and buried. In this paper, we present a new interpretation of buried, pre-Illinoian glacial features along the Laurentide glacial margin in northeastern Nebraska using Airborne ElectroMagnetics (AEM) supplemented with borehole logs and 2 m LiDAR elevation data. We detect and map large-scale (101–102 km) geological features using contrasts in electrical resistivity. The Laurentide glacial limit is marked by a continuous (>120 km) contrast between conductive (<15 Ω-m), clayey tills and resistive (>40 Ω-m) sandy sediments. Several smaller (102 km2) till salients extend 10s of km westward of this margin. We recognize a lithologically heterogeneous zone characterized by variable resistivity and complex geophysical structures extending as much as 17 km west of the glacial limit. This zone is interpreted as a glaciotectonic thrust complex, and it is analogous to a similar thrust complex in Denmark where structural analysis of co-located seismic and AEM surveys provides a standard for comparison. Our study suggests that the maximum advancement of pre-Illinoian glacial ice into Nebraska involved extensive deformation of sedimentary strata, local overriding of these deformed strata by smaller ice tongues, and emplacement of tills as much as 30 km west of the principal Laurentide ice margin. These insights provide the first glimpse of the large-scale stratigraphic architecture of glacial sediments in Nebraska and point to future clarifications of the geology and geomorphology of the Laurentide glacial limit.

The first dated preglacial diatom record in Lake Ladoga: long-term marine influence or redeposition story?

Preglacial environments in Lake Ladoga, the largest European lake, located within the limits of the Scandinavian glaciations, are very poorly investigated compared to postglacial ones. They were primarily reconstructed based on the studies of terrestrial boreholes and outcrops, often incomplete and poorly dated. Previous diatom studies established that during the Eemian marine transgression, the Ladoga basin became a part of the marine Baltic-White Sea connection. However, the environments established in Lake Ladoga after the regression of the Eemian Sea are not known. This article discusses the first Early Weichselian (MIS5, ~ 118–80 ka) diatom record in Lake Ladoga obtained within the frame of the Russian-German research project PLOT. Low concentrations and selective preservation of diatoms in the preglacial sediments point to unstable high-energy environments. The presence of marine diatoms is thought to result from reworking of marine Eemian sediments, rather than direct marine influence. We argue that post-Eemian environments in Lake Ladoga were neither marine nor glaciolacustrine, as previously suggested. The Early Weichselian diatom record formed in a shallow-water part of a lake affected by inflowing streams transporting large amounts of eroded material. No analogues of the preglacial environments can be found in the postglacial Lake Ladoga. Our record demonstrates close similarity to other Early Weichselian diatom records in the Ladoga region suggesting their formation under the same conditions. Similar trends in concentrations of diatoms, diatom fragments and other siliceous microfossils reflect changing sediment supply, hydrodynamics or reworking intensity. Their lower values ~ 118–113 and ~ 90–80 ka could reflect the Early Weichselian cooling stages, while their increase between ~ 113 and 90 ka might indicate enhanced erosion intensity and increased sediment supply corresponding to the climate amelioration.

Complex causes of landslides after ice sheet retreat: Post-LGM mass movements in the Northern Patagonian Icefield region

Although the dynamics of individual rock-slope failures above recently shrinking glaciers have received increasing study, less is known about the spatial distribution of landslides in paraglacial settings. Here, we present a landslide inventory for large deglaciated area (~100,000 km2) situated within the Last Glacial Maximum (LGM) limits of the Northern Patagonian Icefield (NPI). Using satellite images and the TanDEM-X digital elevation model, we mapped a total of 15,543 landslides, among which 1006 are deep-seated landslides (DSLs) with area ≥0.01 km2. The distribution of DSLs is highly asymmetric in a W-E transect of the NPI region, with pronounced clustering along the semi-arid eastern front of the Patagonian Andes. The most strongly affected domain is volcanic tablelands overlying weak Miocene sedimentary rocks, but DSLs tend to also cluster along recently deglaciated (i.e. since the end of the 19th century) eastern margin of the NPI. Compared with other high mountain regions, alpine valleys of the Patagonian Andes are affected by DSLs only in <1% of their area, an order of magnitude lower than in other reported deglaciated mountains. The modest incidence of DSLs in the Patagonian Andes is due to dominance of hard granitoid rocks and relatively weak historical seismic activity. We conclude that 1) geological conditions control the distribution of DSLs and their types in the NPI region; 2) paraglacial effects play secondary (although locally important) roles in the origin of DSLs; 3) local clusters of large DSLs originate due to specifics of the post-LGM landscape evolution, involving drawdowns of glacial lakes and incision of rivers into the unconsolidated deposits; and 4) increased abundance of landslides above the recently shrinking margin of the NPI results from the repeated Holocene fluctuations of glacier snouts around the Little Ice Age (LIA) glacier limits and the spatial coincidence of glacial debuttressing effects with the presence of active faults.

Origin of the Baltic Sea basin by Pleistocene glacial erosion

ABSTRACT The present marine Baltic Sea basin (BSB) occupies an eroded Proterozoic intra-cratonic basin on the Fennoscandian shield. Competing models propose a Neogene fluvial origin, with later modification by glacial erosion, or a much younger development, with overdeepening beneath the Fennoscandian Ice Sheet (FIS). We test these alternatives using a first order source to sink sediment budget for the catchment of the BSB. Best estimates derived from geomorphic and cosmogenic nuclide evidence suggest depths of erosion over the last 1 Ma of 20 m in basement and 40 m in sedimentary rocks that surround the BSB. As the BSB has been overdeepened below a regional base level provided by the shallow Darss Sill at the boundary with the Kattegat, erosion of the BSB may be interpreted as glacial in origin, without a fluvial component. The estimated total volume of source area erosion is 30,628 km3 of which 87% is derived from the present BSB. Sediment volumes in the sink area within the limits of maximum Pleistocene glaciation are estimated at a minimum of 37,629 km3, after correction for local erosion, porosity, and carbonate losses. Marine Isotope Stage 12 and younger sediments account for 87% of the total Pleistocene sediment volume in the sink in Poland. Although significant uncertainties remain, the sediment budget is consistent with erosion of the BSB entirely by the FIS, mainly when the ice sheet reached its maximum extent and thickness during the Middle and Late Pleistocene glaciations.

The changing extent of marine-terminating glaciers and ice caps in northeastern Svalbard since the ‘Little Ice Age’ from marine-geophysical records

Climate warming in Svalbard since the end of the ‘Little Ice Age’ early in the 20th century has reduced glacier extent in the archipelago. Previous attempts to reconstruct ‘Little Ice Age’ glacier limits have encountered problems in specifying the area of tidewater glacier advances because it is difficult to estimate the past positions of their marine termini. Multibeam echo-sounding data are needed to map past glacier extent offshore, especially in open-marine settings where subaerial lateral moraines cannot be used due to the absence of fjord walls. We use the submarine glacial landform record to measure the recent limits of advance of over 30 marine-terminating northeastern Svalbard glaciers and ice caps. Our results demonstrate that previous work has underestimated the ice-covered area relative to today by about 40% for northeastern Svalbard (excluding southeast Austfonna) because marine-geophysical evidence in the form of submarine terminal moraines was not included. We show that the recent ice extent was 1753 km2larger than today over our full area of multibeam data coverage; about 5% of the total modern ice cover of Svalbard. It has often been assumed that moraine ridges located within a few kilometres of modern ice fronts in Svalbard represent either a ‘Little Ice Age’ maximum or relate to surge activity over the past century or so. In the marine environment of northeastern Svalbard, this timing can often be confirmed by reference to early historical maps and aerial photographs. Assemblages of submarine glacial landforms inshore of recently deposited terminal moraines suggest whether a recent advance may be a result of surging or ‘Little Ice Age’ climatic cooling relative to today. However, older terminal moraines do exist in the archipelago, as shown by radiocarbon and10Be dating of Holocene moraine ridges.

Postglacial Uplift: Record in the Gravity Field and in Neogene–Quaternary Structures

Abstract The history of Quaternary glaciation and postglacial uplift in Fennoscandia is considered in relation to the surface topography, gravity, and number of glacial deposits and is compared to the respective processes in North America. The surface topography and the gravity field are correlated over the Fennoscandian region as a whole and for two reference areas of South Norway and the Kola Peninsula. The gravity field is composed as free-air and Bouguer gravity anomalies using modern global models based on satellite data. The impact of glaciation may be responsible for zoned patterns of both topography and gravity. The glaciation centers of Norway are marked by uplifts reaching 2470 and 1500 m and by circular Bouguer gravity lows of ≤ –200 mGal, which correspond to residual crust thickening. The gravity patterns of the Kola Peninsula and Norway consist of circular and polygonal anomalies caused by both postglacial rebound and rock density variations. The general uplift and related extension of the crust led to the formation of fractures of different sizes, from 100–200 km long and 1–2 km deep fjords in Norway to 1–2 km long and 30–20 m deep local fractures on the Kola Peninsula. The gravity field of central North America is characterized by a generalized map of free-air anomalies within the limits of glaciation and a map of free-air anomalies compiled from the global database. Glaciation and its records in the surface topography and gravity patterns are described in more detail for Wisconsin State (USA), where extension fractures are similar to those on the Kola Peninsula. The models explaining the correlation between postglacial uplift and gravity variations can be further updated using seismic and tectonic data, as it was shown previously for the case of Finland.

A chronology for North Sea Lobe advance and recession on the Lincolnshire and Norfolk coasts during MIS 2 and 6

During the last (MIS 2) and older glaciations of the North Sea, a North Sea Lobe (NSL) of the British-Irish Ice Sheet flowed onshore and terminated on the lowlands of eastern England, constructing inset sequences of either substantial ice-marginal deposits and tills or only a thin till veneer, indicative of complex and highly dynamic glaciological behaviour. The glaciation limit represented by the Marsh Tills and the Stickney and Horkstow Moraines in Lincolnshire is regarded as the maximum margin of the NSL during MIS 2 and was attained at ∼19.5 ka as determined by OSL dating of overridden lake sediments at Welton le Wold. A later ice marginal position is recorded by the Hogsthorpe-Killingholme Moraine belt, within which ice-walled lake plains indicate large scale ice stagnation rapidly followed ice advance at ∼18.4 ka based on dates from supraglacial lake deposits. The NSL advanced onshore in North Norfolk slightly earlier constructing a moraine ridge at Garrett Hill at ∼21.5ka. In addition to the large ice-dammed lakes in the Humber and Wash lowlands, we propose that an extensive Glacial Lake Lymn was dammed in the southern Lincolnshire Wolds by the NSL ice margin at the Stickney Moraine. Previous proposals that older glacier limits might be recorded in the region, lying between MIS 2 and MIS 12 deposits, are verified by our OSL dates on the Stiffkey moraine, which lies immediately outside the Garrett Hill moraine and appears to be of MIS 6 age.

The glacial geomorphology of the Loch Lomond (Younger Dryas) Stadial in Britain: a review

ABSTRACTThis paper systematically reviews the glacial geomorphological evidence of the Loch Lomond Stadial (LLS; Younger Dryas) glaciation in Britain (12.9–11.7 ka). The geomorphology of sub‐regions within Scotland, England and Wales is assessed, providing the most comprehensive synthesis of this evidence to date. The contrasting nature of the evidence at the local scale is reviewed and conceptual themes common to multiple sub‐regions are examined. Advancements in glaciological theory, mapping technologies, numerical modelling and dating have been applied unevenly to localities across Britain, inhibiting a holistic understanding of the extent and dynamics of the LLS glaciation at a regional scale. The quantity and quality of evidence is highly uneven, leading to uncertainties regarding the extent of glaciation and inhibiting detailed analysis of ice dynamics and chronology. Robust dates are relatively scarce, making it difficult to confidently identify the limits of LLS glaciers and assess their synchroneity. Numerical models have allowed the glacier–climate relationships of the LLS to be assessed but have, thus far, been unable to incorporate local conditions which influenced glaciation. Recommendations for future research are made that will allow refined reconstructions of the LLS in Britain and contribute to a more comprehensive understanding of glacier–climate interactions during the Younger Dryas.

Late Quaternary glaciation of the northern Urals: a review and new observations

This is a synthesis of the glacial history of the northern Urals undertaken using published works and the results of geological surveys as well as recent geochronometric and remote sensing data. The conclusions differ from the classical model that considers the Urals as an important source of glacial ice and partly from the modern reconstructions. The principal supporting evidence for the conventional model – Uralian erratics found on the adjacent plains – is ambiguous because Uralian clasts were also delivered by a thick external ice sheet overriding the mountains during the Middle Pleistocene. Alternative evidence presented in this paper indicates that in the late Quaternary the Ural mountains produced only valley glaciers that partly coalesced in the western piedmont to form large piedmont lobes. The last maximum glaciation occurred in the Early Valdaian time at c. 70–90 ka when glacial ice from the Kara shelf invaded the lowlands and some montane valleys but an icecap over the mountains was not formed. The moraines of the alpine glaciation are preserved only beyond the limits of the Kara ice sheet and therefore cannot be younger than MIS 4. More limited glaciation during MIS 2 generated small alpine moraines around the cirques of the western Urals (Mangerud et al. 2008: Quaternary Science Reviews 27, 1047). The largest moraines of Transuralia were probably produced by the outlet glaciers of a Middle Pleistocene ice sheet that formed on the western plains and discharged across the Polar Urals. The resultant scheme of limited mountain glaciation is possibly also applicable as a model for older glacial cycles.

Geomorphological and sedimentary evidence of probable glaciation in the Jizerské hory Mountains, Central Europe

The Jizerské hory Mountains in the Czech Republic have traditionally been considered to be a highland that lay beyond the limits of Quaternary glaciations. Recent work on cirque-like valley heads in the central part of the range has shown that niche glaciers could form during the Quaternary. Here we report geomorphological and sedimentary evidence for a small glacier in the Pytlácká jáma Hollow that represents one of the most-enclosed valley heads within the range. Shape and size characteristics of this landform indicate that the hollow is a glacial cirque at a degraded stage of development. Boulder accumulations at the downslope side of the hollow probably represent a relic of terminal moraines, and the grain size distribution of clasts together with micromorphology of quartz grains from the hollow indicate the glacial environment of a small glacier. This glacier represents the lowermost located such system in central Europe and provides evidence for the presence of niche or small cirque glaciers probably during pre-Weichselian glacial periods. The glaciation limit (1000m asl) and paleo-ELA (900m asl) proposed for the Jizerské hory Mountains implies that central European ranges lower than 1100m asl were probably glaciated during the Quaternary.

Glacial refugia and the prediction of future habitat coverage of the South American lichen species Ochrolechia austroamericana.

The biogeographic history of lichenized fungi remains unrevealed because those organisms rarely fossilize due to their delicate, often tiny and quickly rotting thalli. Also the ecology and factors limiting occurrence of numerous taxa, especially those restricted in their distribution to tropical areas are poorly recognized. The aim of this study was to determine localization of glacial refugia of South American Ochrolechia austroamericana and to estimate the future changes in the coverage of its habitats using ecological niche modeling tools. The general glacial potential range of the studied species was wider than it is nowadays and its niches coverage decreased by almost 25% since last glacial maximum. The refugial areas were covered by cool and dry grasslands and scrubs and suitable niches in South America were located near the glacier limit. According to our analyses the further climate changes will not significantly influence the distribution of the suitable niches of O. austroamericana.

A flint artefact (Accession No. DONMG 2016.7.1) from Lindholme, South Yorkshire

One of the last papers which Alan was working on when he died was a short note on a flint artefact from the surface of a gravel scrape at Lindholme in South Yorkshire. This was found during fieldwork by Robert Friend, a postgraduate student in Geography at the University of Edinburgh, working on the limits of the last glaciation in the Vale of York (Friend 2011). The results of this have been published elsewhere (Bateman et al. 2015; Friend et al. 2016), but the context of the artefact is ambivalent and Alan’s appendix on the flint was judged too archaeological and site specific for inclusion in either paper. It is a find, however, worth placing on record as one of a number of scattered surface finds of Upper Palaeolithic affinity from the region (compare with Garton et al. 2016; Grassam &amp; Weston 2015; Harding et al. 2014).

The Drangajökull ice cap, northwest Iceland, persisted into the early-mid Holocene

Abstract Most glaciers and ice caps in Iceland experienced rapid deglaciation in the early Holocene, reaching a minimum extent during the Holocene Thermal Maximum. Here we present evidence of the Holocene glacial history from lake sediment cores retrieved from seven threshold lakes around the Drangajokull ice cap in the Vestfirðir peninsula, NW Iceland. The sediment cores show on/off signals of glacial meltwater activity, as minerogenic material deposited from glacial meltwater alternates with organic-rich material (gyttja) deposited without glacial meltwater. We base the chronology of the sediment cores on 14C ages and geochemical identification of key tephra layers with known ages. A 25-cm thick layer of the Saksunarvatn tephra in Lake Skorarvatn indicates that the northern part of the ice cap had reached a similar size as today or was smaller already by 10.2 cal kyr BP. However, 14C ages of lake sediment cores from the highlands southeast of Drangajokull suggest that this part of the ice cap was larger than today until 7.8–7.2 cal kyr BP. Even today, the Drangajokull ice cap has a different behavior than the main ice caps in Iceland, characterized by a very low glaciation limit. Because palaeoclimatic proxies show an early-mid Holocene temperature optimum in this part of Iceland, we suggest that the persistence of Drangajokull into the early Holocene and, possibly, also the entire Holocene was due to high winter precipitation.